Installation Guide Nu

INSTALLATION GUIDE MONOLITHIC REFRACTORIES

Installation Guide NU.DOC

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WORKING INSTRUCTIONS for REFRACTORY - CASTABLES A. General instructions B. Working instructions - conventional castables C. Working instructions - low cement castables D. Placement of monolithics by gunning E.

Working instructions - gunning concretes

F.

Working instructions - insulating castables

G. Working instructions-mortars H. Anchor-systems I.

Drying and heat-up schedules

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A. General Instructions

6

1. Introduction

6

2. Transport

6

3. Storage

6

4. Recommended mixer types 4.1 Paddle mixer 4.2 Continuos mixer 4.3 Mixocret

9 9 10 11

5. Mixing Procedure 5.1 Recommended mixing time 5.2 Recommended consistency (ball-in-hand-test)

12 12 13

6. Casting and vibrating 6.1 Preparation of adjoining areas

14 14

7. Templates and expansion joints 7.1 Templates 7.2 Expansion joints

14 14 16

8. Setting time, Removal of the mould

17

9. Drying and heat-up 9.1 Controll of the heat-up process

17 18

B. Working Instructions for conventional castables

19

1. Delivery and storage

19

2. Water

19

3. Mixing and vibrating

20

4. Heat-up instructions

21

C. Working Instructions for low cement castables

22

1. Delivery and storage

22

2. Water

22

3. Mixing and vibrating

23

4. Heat-up schedule

24

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D. Gunning application

25

1. Types of gunning machines

26

2. Air supply

28

3. Nozzle

29

4. Water

29

5. Communication and co-ordination

30

6. The gunning process

31

E. Working Instructions for gunning concretes

34

1. Delivery and storage

34

2. Placement by gunning

34

3. Checklist 3.1 Air supply 3.2 Water supply 3.3 Material hose 3.4 Nozzle assembly 3.5 Start up 3.6 Gunning 3.7 Shut down

34

F. Working Instructions for insulating castables

36

1. Delivery and storage

36

2. Water

36

3. Mixing and casting

36

4. Placement by gunning

37

5. Setting time

37

6. Drying and heat-up

37

G. Working Instructions for mortars

38

1. Product characteristic

38

2. Delivery and storage, shelf life

38

3. Preparation and mixing

39

4. Setting behaviour

40

5. Drying and heat-up

40

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H. Anchor system

41

1. Selection criteria

41

2. Examples for lining supports

42

3. Metallic anchors 3.1. Distribution (walls) 3.2. Distribution (ceilings) 3.3. Types of metallic anchors 3.3.1. Linings with insulation 3.3.2. Linings without insulation 3.4. Anchor material 3.5. Electrodes

43

I. Drying and heat-up instructions

49

1. Preheater and Heat Exchanger

49

2. Dryinf of Kiln Hood, Tertiary Air Duct, Cooler 2.1 Auxiliary burner for drying the Kiln Hood 2.2 Auxiliary burner for drying the Tertiary Air Duct 2.3 Auxiliary burner for drying the Cooler

51

3. Heating up the Rotary Kiln 3.1 Preparations 3.2 Heating up the entire plant 3.3 Rotating the kiln during heat-up 3.4 Disturbances and repeated heating up

53

4. Shutdown of the Kiln

57

5. Important points

58

6. Error sources when rotating Rotary Kilns

59

7. Sketches

60

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A.

GENERAL INSTRUCTIONS

1. Introduction When handling and placing chemical, hydraulic or low cement bonded castables, attention has to be paid to the following principle: ”A high value product handled bad may be of worse quality then a perfectly placed lesser value product.” The technical data sheets of these products line out the amount of mixing water as the most important indicator for castables. Depending on the conditions when mixing, the amount of water may be varied within ± 0,5 to 1 %. The most important factors of influence are: -

lining thickness

-

kind of insulating or permanent lining (porous or water repellent)

-

temperature of the permanent lining

-

ambient temperature when mixing and placing the castables (ideal 15-20°C)

2. Transport Refractory mixes, insulating castables, mortars and auxiliary materials have to be protected against moisture. Therefore, they have to be transported in closed wagons, trailers or ship holds. When arriving at the working-site, all packages have to be checked if any damages happened during transport. Any damages occurring during transport are to be notified to the carrier, the supplier and to the appropriate insurance company immediately.

3. Storage Storage Type I: Outside storage with tarpaulin cover For fireclay bricks, lightweight bricks, insulating bricks, (high) alumina bricks, anchors and auxiliary materials. The ground should be plain and compacted to ensure that it is possible to transport materials by a fork lift. It is necessary to ensure that rain water can easily be drained away to avoid dampness from the ground. Frozen material has to be warmed up sufficiently (material temperature at least +10°C). Installation Guide NU.DOC

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Storage type II: Inside storage in covered, closed rooms For all magnesia bricks, unburned chemical bonded high alumina and light weight bricks, refractory concretes, insulating concretes, mortars, block insulation and auxiliary materials. All above-mentioned materials have to be stored dry and frost-free in ventilated, closed rooms (ideal temperature 15 - 25 °C). If the storage capacity is insufficient, it is allowed to store the block insulation and auxiliary materials as described under ”Storage Type I”. Unshaped products generally have a limited storage life, indicated in the respective data sheets. Especially already opened packages of monolithic materials have to be stored as mentioned above and to be used as soon as possible. The material should be used within six months; - in practice, if the ambient relative humidity is very low, and the storage is like mentioned above, the material will not suffer and the storage life can be doubled. Castables: If castables have hardened during storage and contain lumps, which cannot be crushed by hand, the material cannot be used under any circumstances, because the binder may already have reacted. Storage in tropical climate (i.e. extremely high humidity and strong sun radiation): If it is not possible to avoid the formation of condensation water under the shrink wrapping despite ventilation, the shrink wrapping should be opened. Because of expected formation of condensation water, it is forbidden to store the material in transport containers. If the castables, mortars and insulating concretes were exposed to direct radiation from the sun, it is recommended to let them cool down (ideal 20 °C) before mixing. Otherwise the setting behaviour would change rapidly, e.g. it would not be possible to install the concrete properly, due to a very fast bonding. Already installed magnesia bricks Basic bricks have to be installed as late as possible, i.e. immediately before heating up (maximum 4 weeks). Take care of well ventilation and protection of lining against wetness in the period between completion of installation and first heating up. Effect of wetness If refractory materials have become wet, despite protective measures, they have to be stored free of frost (i.e. above +10°C), furthermore the following instructions have to be considered ! ⇒

Fireclay bricks, high alumina bricks, light weight bricks and insulating bricks: These materials have to be dried carefully before use.

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⇒

Magnesia bricks: They have to be checked in view of damages by hydration (characterised by cracks on the surface and increase in volume) and be dried at ”room temperature” (i.e. no hot air). Damaged bricks cannot be used anymore!

⇒

Refractory concretes, insulating concretes and mortars: Unshaped materials cannot be used when they got wet, because the bonding of the cement already began.

⇒

Unburned chemical bonded high alumina and light weight bricks: These special products tend to absorb moisture from the air even when properly stored, but in that case they need not to be dried before installation.

⇒

Block insulation: If insulation blocks have become wet, they can be installed without previous drying. Nevertheless drilling holes into the steel shell is recommended.

Permitted stack height of pallets The basic precondition for higher stacks is a sufficient load bearing capacity of the ground. Storage Type I: Bricks: Light weight and insulating bricks:

4 pallets 2 pallets

Storage Type II: Bricks: Unshaped materials (castable, mortar, etc.): Block insulation:

4 pallets 3 pallets 2 pallets

Management of stock If larger amounts of refractories are delivered, storing in accordance to the construction schedule is recommended. It should be possible for a fork-lift truck to reach each block directly. Furthermore take care that the marking is clearly visible. Hint: For logistical and technical reasons, it is wise to store the insulating materials as well as the auxiliary materials (anchors electrodes, adhesives, Bitumen etc.) in separate areas or rooms.

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4. Recommended mixer-types for RHI refractory concretes RHI´s conventional castables and low cement castables contain additives, which, during mixing, should be moistened with a low amount of water and be dispersed in the best possible manner. The quality of the concrete depends on the shear-power which is achieved by the power of the mixer-paddles. For this reason only paddle-mixers are recommended for mixing of RHI - refractory concretes. Concrete mixing drums should only be used in exceptional cases and exclusive for conventional castables with higher cement content. Mixers warming up the material more then 35°C because of to high r.p.m. of the paddles are unsuitable; the setting and working time of the concrete will decrease decisively.

4.1. Paddle Mixer To achieve perfect quality of the refractory concrete the material should be quickly homogenised by mixing dry (about 10-30 seconds or 10 rounds). Next add quickly ¾ of the total water required and mix about 1 minute. Add the remaining quarter progressively to obtain the required consistency. The total mixing time varies from 3 to 6 minutes, depending on the size of the mixer used. The commonly used paddle mixers have a capacity of 100 to 150 kg. / filling, that means a capacity of 1 to 2 tons of concrete / hour. dry mix

water

mixing paddles

motor ready-mix outlet

fig. 1: paddle mixer

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fig. 2: Zyklos paddle mixer

fig. 3: paddle movement

4.2. Continuous Mixer One alternative to the big paddle mixers is the continuous or horizontal mixing unit. This type of mixer is able to mix up until 10 tons of concrete per hour, depending on the capacity of the used feeding-screw. Although the mixing time is short compared to the paddle mixer, for most applications the mixing intensity is sufficient. The required amount of water is added continuously at the water ring. The exact amount of water has to be adjusted manually by the operator, which shows an disadvantage of these mixer types. The most practical and reliable method to check the consistence is still the ”ball in hand test”: A ball (approx. as big as a fist) is formed. If the ball (when shaking the hand slightly) crumbles – the concrete is too dry slowly flows apart – the concrete has the optimum consistency flows apart quickly – the concrete was mixed with too much water. (See also chapter 5, Mixing; Recommended consistency)

The following mixer types are approved by RHI: PFT.....................................TYPE HM5 PUTZMEISTER ................TYPE CM 1228; 932

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dry mix

water inlet nozzle

worm conveyor mixing paddles

motor

fig. 4: continuous mixer

4.3. MIXOCRET MIXING and PUMPING UNIT The speciality of the MIXOCRET is it’s double function of being a paddle mixer as well as a pumping equipment, so it is no longer necessary, in contrary to the conventional paddle mixers - to use cranes, transporting units like buckets, chute slides etc. A further advantage is the compactness of the whole unit. Moreover the MIXOCRET is an excellent paddle mixer and is very well suited for the mixing of thixotropic low cement castables. Function of the MIXOCRET - system: In the pressure vessel a single horizontal paddle mixer with changeable special mixing tools is installed, which have a mixing and transporting function as well. After filling the vessel with the material and adding the required amount of water an intensive mixing starts. As soon as the mixing is done and the lock is closed, pneumatic pressure is blown into the vessel. The pressurised air compacts the castable in the vessel and pushes it, supported by the mixing tools, to the outlet. Directly after the outlet a second pipe injects the transportation-air into the system. Thus the refractory is transported to the hose-outlet in form of ”plugs” (material – air – material – air ...). The main-pressure to the vessel and the transport-air to the hose coupling are separately controlled. The outlet block with pot and arc shaped outlet device let the pressurised air and the mix escape at the end of the outlet-tube without interruption.

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1.........pressure vessel 2.........compressed air 3.........mixing paddles 4.........motor (10-30 kW) 5.........gear box 6.........material hose 7.........material outlet nozzle

fig. 5: The MIXOCRET system

fig. 6.: MIXOCRET mixer

5. Mixing procedure 5.1

Recommended mixing time A) B)

Dry mixing: Homogenising with water - for conventional castables - for low cement castables

1

minute

3 minutes 4 - 5 minutes.

The longer mixing time for low cement castables is required to homogenise and to disperse the micro-powder additives. Brands with additives of organic fibres or steel fibres have to be premixed with ¾ of the required amount of water before adjusting the right consistency with the remaining quarter.

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5.2

Recommended consistency - “BALL-IN-HAND-TEST”

The most practical and reliable method to check the correct consistency is still the ”ball in hand test”: A ball (approximately as big as a fist) is formed. If the ball (when shaking the hand slightly):

crumbles – the concrete is too dry

slowly flows apart – the concrete has the optimum consistency

flows apart quickly – the concrete was mixed with too much water.

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6. Casting and vibrating The working time for these castables is approximately half an hour, dependent on the amount of water and the ambient temperature. Therefore never mix more material than you can install within half an hour. After mixing the concrete should be placed immediately. Depending on the quantity needed and the complexity of the templates either use vibrators fixed to the moulds or poker-vibrators. Their number, size and power must be selected for each particular case. In general it is advised to avoid excessive vibration; a flat, bright surface indicates that the product is sufficiently compacted. If vibration is continued, the mix will begin to segregate and laitance will appear on the surface. Among other undesirable effects, the mechanical strength of the casted section will be reduced.

6.1

Preparation of adjoining areas:

Adjoining areas which may withdraw moisture from the concrete have to be impregnated or made water-repellent. This can be done by applying liquid sodium silicate, oil, grease or paraffin or by covering the surfaces with plastic.

7. Templates and expansion joints 7.1. Templates Contrary to brick - installations, where you are bound to certain shapes, installations using refractory castables can be adjusted to any required shape and lining thickness. Nevertheless, monolithic linings may not be casted in just one piece. To begin with, you are forced to cast in sections due to the speed of the installation. On the other hand, these products extend (or shrink) when heating up. Thus the total area is divided into fields (Fig. 7; 8; 9). This is made by templates made of wood or metal. The resulting joints mostly are constructed staggered, as a so called “Z-joint”, and are “sealed” with ceramic fibres. Installation of unshaped products Relating to the chapter “Mixing of refractory castables”, refractory castables are installed using paddle mixers. By that means the progress of the installation is restricted, unless very heavy mixers, with e.g. a capacity of 1 tonne, are used. Because of the very quick bonding behaviour of these hydraulically bonded castables, the amount of mix to be installed, has to be calculated thoroughly. The single sections may only be so big, that they can be filled completely within half an hour.

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To facilitate the removal of the template after castables setting, oil the surface of the template moderately; excessive use of oil may decrease the lining quality. The casted sections should not be greater then 1 m2. The resulting expansion joint should compensate the thermal stress. As expansion joint use ceramic fibre blankets with a thickness of 3 - 12 mm. Make the blankets water repellent by covering with plastic or impregnate with water glass (liquid sodium silicate). ATTENTION: When using self-flowing castables the moulds / templates have to be absolutely watertight. Because of the self-flowing / levelling behaviour of these mixes the material can flow out even through slightest gaps and result in great losses of material. Examples for casted sections: a) ceiling or hearth

5 1

b) beams

3

6

1

2

4

2

4

fig.: 007

fig.: 008

c) rotary kilns / tubes:

refractory concrete

working joint

metallic anchor

wooden or iron template

shell

ca. 1m

fig 009

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7.2. Expansion joints After installation, when drying these products, they undergo shrinking-processes, due to bonding-reactions. During the first heat-up an irreversible heat-extension takes place. Later, during drift, reversible linear changes appear. To protect the refractory castables against mechanical damage, the contact areas of the single sections are provided with expansion – joints (Fig. 10). Also in corners or between different parts of the aggregates, attention has to be paid to sufficient expansion (Fig. 11). Equally between refractory areas and metallic areas, e.g. between the refractory lining of cyclone roofs and the insertion tubes. The kind and thickness of the materials used, respectively the application areas can be found in the technical drawings.

Fig. 10

Fig. 11

It can be chosen between different materials with different thickness, for every application and area. Find here a choice of our articles. Material

Description

BD [kg/m³]

CT* [°C]

Pyrofiber 1260

Loose ceramic fibres

Pyrostop Blanket 128/1260

Ceramic fibre blanket

128

1260

Pyrostop Superfelt 1300

Ceramic fibre blanket

180

1300

Pyrostop Felt 128/1430

Ceramic fibre blanket

128

1430

Pyrostop Papier 1260

Ceramic fibre paper

200

1260

1260

* Classification Temperature

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8. Setting time, Removal of the mould Depending on the ambient temperature and the kind of the castable, the setting time will be approx. 6 hours. The templates can be removed approx. 10 - 12 hours after the installation is completed. After finishing the job these mixes must air dry for at least 24-48 hours. It is recommended that the installed parts are covered with plastic during curing. Only then can heating begin.

9. Drying and heating When the curing is done, dense castables must be heated-up to the drift temperature sufficiently slowly and gradually to avoid damaging them. A number of phenomena, mainly irreversible, occur during this preliminary heating-up. Below 600°C, these phenomena mainly result from the progressive dehydration of the material. When the material has set, it contains water in two forms: -

chemically bonded water has reacted with the cement to form hydrates,

-

“free” water which is saturated in the porous material (dense castables contain roughly 50% of the mixing water still in the free state).

Free and bonded water, at higher temperature change into steam. If the steam pressure is higher then the ambient pressure the steam will escape. However, the temperature has to be increased slowly to ensure that the mechanical strength of the material is sufficient to withstand the steam pressure. The air or gas in contact with the material has to be as dry as possible to allow the steam to escape. In other words, the air has to be constantly renewed. When the water is extracted, the dimensions of the material vary irreversibly and non linearly. These variations are characteristics of the first heating up. They initially occur when the free water is eliminated and the structure becomes more compact and, subsequently, variations occur due to the crystalline structure of the hydrates changing. This again makes it essential to ensure that the temperature is increased slowly to avoid sudden changes in dimensions generating high stresses which could lead to disintegration of the material. Free water starts to evolve as soon as the temperature rises and the maximum extraction efficiently is reached in the range of 100 - 150 °C. Subsequently, bonded water is evolved at various temperatures between 250 and 600 °C, depending on the types of hydrates formed during setting.

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9.1 Control of the heat - up program: It is essential to use thermocouples to control the temperature-graph during heat-up. Place these thermocouples both at the hot face an the cold face of the lining, in several points to control the temperature in different parts of the lining. In very complex cases (multi layer linings, variable lining thickness etc.) it is advisable to place thermo-feelers even in different depths of the lining to obtain as much information as possible to control the heating up program. Electrical heating elements would offer the highest degree of flexibility and sensitivity. However, in most cases, the aggregates own source of energy (oil; gas) or hot air generators are used for drying. The higher the capacity of one of these systems is, the less is their sensitivity. Care must be taken to follow the theoretical graph as close as possible. There is no ”universal” graph applicable to every situation; the nature and thickness of the different materials used, makes each lining a special case. To allow the steam to decompress and to stabilise the pressure, at several temperature points so called ”holding points or holding times” are installed. The length of the constant temperature periods must be varied, depending on the rate at which steam escapes; the temperature must be held as long as the steam-volume does not decrease. Depending on the specific cases the holding periods may be longer or shorter as shown in the theoretical graph.

For further informations see also chapter: I. Drying and heat-up instructions

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B.

WORKING INSTRUCTIONS FOR CONVENTIONAL CASTABLES

1. Delivery and storage RHI’s conventional castables are delivered dry in humidity proof valve bags. Depending on the application the material can be supplied in bags from 25 kg up to 1 tonne. These refractory concretes are, like all hydraulically bonded gunning/vibrating mixes, very sensitive to moisture. It is possible that, under the wrong storage conditions, the material will begin to bind in the package. Therefore the material has to be stored frostfree at temperatures of around 20 ± 5°C and protected against moisture. Under these conditions the shelf life is at least 8 months. The precise lifetime can be found in the technical datasheets. If the castables have hardened during storage and contain lumps, which cannot be crushed by hand, the material cannot be used under any circumstances, because the binder may already have reacted.

2. Amount of water and its temperature Only potable water has to be used (no seawater !!). These low cement castables have to be blended in a suitable paddle mixer with potable water (temperature 15 to 25 °C). Higher water temperature accelerates the setting time, and there would not be enough time for casting and vibrating. The exact amount of mixing water can be found in the technical datasheets. Usually the amount is given in litres/100 kg dry mix. Too much water increases setting time and reduces strength. The amount of water may be reduced or exceeded within ± 0,5 %. The water added during mixing has two functions: -

completely hydrate the hydraulic binder (cement) make the product sufficiently fluid (but not too fluid !) for placement.

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3. Mixing and vibration procedure For these kind of castables the use of a paddle mixer is recommended ! Contamination of the concrete has to be avoided, so only clean and faultless units may be used. To reach the optimum consistency a mixing period of 4-5 minutes has to be adhered to. To achieve an even grain distribution mix the castable without water for 30 to 60 seconds. After this dry-mixing-period add approx. 80 % of the water. Mix the material for 3 minutes. The remaining water is added to achieve the correct consistency. The stipulated amount of mixing water may be varied by a maximum of ± 0.5 %. If the amount is increased dramatically it inevitably leads to separations and decreased strength. If the amount is decreased dramatically you will no longer be able to install the material properly. To achieve the correct amount of mixing water we recommend an initial consistency-test. Put a poker-vibrator into a bucket with the castable. The concrete must compact within 5 seconds due to the vibration. As an alternative the “ball-in-hand”-test is recommended. The working time for this kind of castable is approximately half an hour, dependent on the amount of water and the ambient temperature. Therefore never mix more material than you can install within half an hour. Depending on the application vibrators on the moulds/templates or poker-vibrators are used. Excessive vibrating has to be avoided. A smooth and shiny surface relates to a good compaction. If the structure is that large that the product must be poured in successive layers, it is essential to break the structure down into zones, that no more than 20 minutes elapse between pouring the first layer and adding the next batch of material to ensure correct bonding between the successive layers.

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4. Heat-up schedule for conventional castables This is a commonly valid heat-up schedule for a single-layered installation with a lining thickness of 6 inches. The given temperature is the temperature in the furnace chamber. As a rule of thumb the holding times are given with 1 h / 1 cm. For combined multi-layer installations different heat-up schedules are needed. 1000

drift temperature

900 800 700

50°C/h

600 [°C]

HT 15 h

500

15°C/h

400 300

15°C/h

200

HT 15 h

100

40°C/h 0 0

10

20

30

40

50

60

70

Duration of heat-up [h]

See also chapter: I. Drying and heat-up instructions

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C.

WORKING INSTRUCTIONS FOR LOW CEMENT CASTABLES

1. Delivery and storage These “Low-Cement” castables are delivered dry in moisture protected packages. Depending on the application the material can be supplied in bags from 25 kg up to 1 tonne. These low cement refractory concretes are, like all hydraulically bonded gunning/vibrating mixes, very sensitive to moisture. It is possible that, under the wrong storage conditions, the material will begin to bind in the package. Therefore the material has to be stored frostfree at temperatures of around 20 ± 5°C and protected against moisture. Under these conditions the shelf life is at least 6 months. The precise lifetime can be found in the technical datasheets. If the castables have hardened during storage and contain lumps, which cannot be crushed by hand, the material should not be used under any circumstances, because the binder may already have reacted. The package has to be stored at an ambient temperature of 20 °C ± 5 °C and to be protected against moisture.

2. Amount of water and its temperature Only potable water has to be used (no seawater !!). These low cement castables have to be blended in a suitable paddle mixer with potable water (temperature 15 to 25 °C). Higher water temperature accelerates the setting time, and there would not be enough time for casting and vibrating. The exact amount of mixing water can be found in the technical datasheets. Usually the amount is given in litres/100 kg dry mix. Too much water increases setting time and reduces strength. The amount of water may be reduced or exceeded within ± 0,5 %. The water added during mixing has two functions: -

completely hydrate the hydraulic binder

-

make the product sufficiently fluid (but not too fluid !) for placement.

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3. Mixing and vibration procedure These low cement castables have to be blended in a suitable paddle mixer with potable water at a temperature of about 15 to 25 °C. Contamination of the concrete has to be avoided, so only clean and faultless units may be used. To reach the optimum consistency a mixing period of 5 - 6 minutes has to be adhered to. To achieve an even grain distribution mix the castable without water for 30 to 60 seconds. After this dry-mixing-period add approx. 80 % of the water. Mix the material for 4 minutes. The remaining water, carefully measured, is added to achieve the correct consistency. The stipulated amount of mixing water may be varied by a maximum of ± 0.5 %. If the amount is increased dramatically it inevitably leads to separations and decreased strength. If the amount is decreased dramatically you will no longer be able to install the material properly. Attention: Under no circumstance may these castables be casted with a liquid consistency. To achieve the correct amount of mixing water we recommend an initial consistency-test. Put a poker-vibrator into a bucket with the castable. The concrete must compact within 10 seconds due to the vibration. As an alternative the “ball-in-hand”-test is recommended. The working time for this kind of castable is approximately half an hour, dependent on the amount of water and the ambient temperature. Therefore never mix more material than you can install within half an hour. Depending on the application vibrators on the moulds/templates or poker-vibrators are used. Excessive vibrating has to be avoided. A smooth and shiny surface relates to a good compaction. If the structure is so large that the product must be poured in successive layers, it is essential to break the structure down into zones, that no more than 20 minutes elapse between pouring the first layer and adding the next batch of material to ensure correct bonding between successive layers. Castables which are about to set, may not be mixed again or vibrated.

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6. General heat-up schedule for low cement castables Drying at ambient temperature 24 - 48 hours, depending on linings thickness. Within the first 12 - 16 hours the surface should be sprayed with water or be covered with a wet mat or plastic. Heating up to 175°C within 8 hours following by a subsequent holding time of 24 to 48 hours (depending on lining thickness: - about 1 hour per cm thickness). Heating up to 250°C by increasing the temperature with 25 °C per hour, followed by another holding time of 12 hours. Heating up to 450°C with approx. 15 °C per hour; at that temperature holding time of 12 hours or more. Heating up to working temperature in steps of 40-50°C / hour.

This is a commonly valid heat-up schedule for single-layered installations with a lining thickness of 6 inches. The given temperature is the temperature in the furnace chamber. As a rule of thumb the holding times (HT) are given with 1 h / 1 cm (at low temp.) and 1 H / 2 cm (at high temp.). For combined multi layer installations different heat-up schedules are needed. 1000

drift temperature

900

800 700

50°C/h

600 [°C]

HT 8 h

500 400

HZ 8 h

300

15°C/h

HT 15 h

200

25°C/h

15°C/h 100

50°C/h 0 0

10

20

30

40

50

60

70

Duration of heat-up [h]

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D. APPLICATION OF MONOLITHIC REFRACTORIES BY GUNNING

Unlike brick-laying, the application of monolithic refractory products is not a traditional trade. The increasing development of highly-technical products and the progress made with equipment (gunning machines and pumps), now oblige a conscientious supplier to provide training for users of these monolithic refractory castables. The procedures and guidelines of pneumatically placed refractory materials are frequently left up to the installers on the job site. Much of their knowledge was gained by trial and error - or at times, just get the job done the best possible way. The successful application of any refractory product by gunning depends, to at least 85 %, on the man at the nozzle, the machine operator and the type of equipment used. The following pages are to help to establish some guidelines and provide assistance to both the nozzle operator and the machine operator for the best placement of refractory gunning mixes. The various types of material, the conditions under which they should be used and improvements, which can be introduced to get the best from the equipment, should be discussed. There are several types of monolithic refractory products : (a) (b) (c) (d) (e)

Refractory castables Refractory castables Pre-dampened refractory ramming mixes Plastic refractory ramming mixes Insulating refractory castables

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1. Types of gunning machines There are now many types of gunning machine offering different levels of performance. It could even be said that the gunning technique has not kept up with developments in industry even though it has been in use since the last century. The oldest type of machine has a pressurised tank and is referred to as the ”BATCH GUN”. There are 3 versions of this machine, all still frequently used.

1.1. The simple gravity Batch-Gun The product is poured into the tank from the top. The opening is closed by a bell-shaped valve which bears against a rubber seal attached round the circumference of the opening. The pressure in the tank then forces the bell upwards until it is hermetically sealed. The flow of product is controlled by a butterfly valve, mounted at the bottom of the outlet cone, and by the quantity of compressed air fed into the tank.

1.2. Gravity Batch-Gun + mechanical flow controller The principle is the same as above but the flow of product is controlled by speeding-up or slowing-down a paddle rotor.

1.3. Gravity Batch-Gun + mechanical flow controller (conveyor screw) The principle is the same as above but the paddle rotor is replaced by a conveyor screw. All three machines can be used in various ways.

1.4. The intermittent-loading Batch-Gun The previous load must have been entirely finished before a new batch can be loaded. To load a new batch, gunning must be stopped and the machine must be filled, either using bags which takes long time and is not really compatible with modern working conditions - or from a hopper. This second method allows the machine to be fully loaded, with a large quantity of material - 1 to 3 tons depending on the tank capacity - at a single go.

1.5. The continuous-loading Batch-Gun This machine requires a double chamber. In this case, the lower part of the machine is filled first, the conical valve is then closed, this first chamber is pressurised and we are ready to start gunning. At the same time, the machine operator fills the second chamber, pressurises it and opens the conic valve leading to the lower compartment such that the load can fall into it. This cycle can then be repeated to allow continuous gunning.

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Obviously, this type of machine requires a very good operator since there is no room for mistakes in any of the operations. A few of these machines are still used but they are tending to disappear because they require far too much support for large jobs (a nozzle operator, a machine operator, a conveyor belt, feed hoppers, a fork lift truck and driver are all required throughout the work).

1.6. “Rotor-chamber” machines These are known as ”mechanical distribution” machines and allow continuous loading. There are many manufacturers of such machines, including Meynadier, PFT, Aliva, Velco, BSM and REED. All these machines work on the same principle: The product is loaded into a hopper (1) and drops into a slotted rotor (2) driven by an electric or compressed air motor. As the rotor turns, the slots, full of material, pass under a rubber seal which bears against the upper face of the rotor. This seal contains a hole which forms a compressed air inlet (3) to the slots. The compressed air therefore pushes the product downwards.

There is a similar seal at the bottom of the rotor. This also has a hole (4) of the same diameter as the rotor slots. The compressed air therefore forces the product out of the rotor via this hole and into the delivery hose (5). 3 5 4

Although the machine is relatively simple, the maintenance required to keep it in good working condition is expensive. The seals must be replaced frequently and the top and bottom faces of the rotor become worn and require regrinding. This means the distribution section of the machine must be completely stripped. The problems this can cause when the operation must be carried out on site can easily be imagined.

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fig. 11: gunning machine

2. Air supply The inside diameter of the air feed line to the machine must be at least 2/3 of the inside diameter of the product delivery hose (check the diameter of the air supply lines). If the diameters available on the site are less than this value, a Y or T junction can be connected at the end of the machine air feed line. However, always check that the capacity of the two or three hoses connected to these junctions is at least equal to the capacity of the machine air feed line.

The minimum air flow required is 8000 litres per minute at a minimum pressure of 5 bar. Having ensured that the machine has an adequate air supply, we must now consider the product delivery line to the wetting nozzle. The hoses are supplied, as standard, in 20 meter lengths. If only one length is used, it will be found that the flow of product is slightly jerky because the space between the rotor slots leave slight gaps in the flow of product. To avoid this, always use two lengths of hose. This will leave sufficient time for the product flow to stabilise and ensure a perfectly uniform feed to the nozzle.

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3.

Nozzle

fig. 12: hydromix nozzle The wetting nozzle ensures: - that the gunned mix is completely uniform, - better wetting of the product to prevent the generation of dust even when high air pressures are required in the hoses, - no dust or misting is generated. The features of the nozzle which ensure this are : - a water ring with small-diameter holes set at 45° to the pipe centreline. These generates a crossed, conical jet which wets the product, even in its very centre, as it passes through the ring. - a length of hose after the water-ring to compress the product and ensures that fine particles will bind to larger grains, and that the product is a completely homogeneous mix before it is fed to the metal outlet pipe. The length of hose in the wetting nozzle can vary depending on the type of product. The rubber hose must never be more than 750 mm long for normal gunned alumina products. The metal lance can be up to 600 mm long, as required on site, without causing any problems.

4. Water The water pressure must always be twice the pressure indicated on the air pressure gauge of the gunning machine. This will ensure better wetting and less rebound. Obviously, the water will not correctly penetrate the air / material flow at the water ring if the air pressure is greater than the pressure of the water. The water pressure available on sites rarely exceeds 3 bars and is frequently far less. This is why many of our machines are fitted with booster pumps to increase the normal mains pressure to 8 bar. This ensures that the product will be thoroughly wetted and perfect to gun.

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fig.013: different valve types

water rings

5. Communication and co-ordination Communication and co-ordination are very important when the application area of the gunning material is in some distance, or on a different level, to the machine. Communication is essential for safety reasons, but is also needed to ensure that the best conditions are maintained at both ends of the operation, i.e.: - to ensure that the air / material ratio is always correct, - to ensure that the water pressure is kept at the right value for correct wetting at the nozzle, - to minimise time and unnecessary operations. Many measures have to be taken by the operators. The most important are : - The gunning equipment must be correctly maintained. This includes cleaning and greasing every day and after completing the job. - The equipment must be correctly installed for each job. NEVER attempt to work in a zone where there is not sufficient air and water. - The machine operator is the team’s ”King-pin”. For example, if the air/product mix is not correct and the flow in the delivery hose is not uniform, even the best nozzle operator will not be able to do a good job. - These two men - THE MACHINE AND NOZZLE OPERATORS - must form a team. If possible, each should be capable of doing the other’s job. - The nozzle operator’s job will vary depending on the type of lining being installed, including its thickness, anchor-arrangements, vertical or overhead surfaces, the ambient temperature and the type of product being applied.

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6. Gunning process Essential aids to good gunning include: -

Proper lighting of the working zone.

-

Enough space to handle the nozzle correctly.

-

If scaffolding or a platform are required, they should be movable to allow the nozzle operator always to respect the recommendations on the use of the nozzle given below. The distance from the lining and the nozzle angle required are particularly important.

-

Proper spacing and location of anchors, particularly on overhead installations. Keep anchors free of any rebound material.

6.1. Start-up The start-up operations must be carried out in a strict sequence which is always the same, for all types of rotary machines. 1.

Check that all connections have been made.

2.

Open the air and adjust the flow to the value required for the operation (depending on the distance and difference in levels).

3.

Open the water valve to check the wetting nozzle.

4.

Close the water valve.

5.

Close the air valve.

6.

Load the machine.

7.

Open the air valve.

8.

Slowly open the water valve until a spray is obtained at the tip of the nozzle.

9.

Start the rotation of the distribution barrel.

10. Adjust the water flow to obtain a completely uniform product mix.

The quantity of water required at the nozzle depends on the products but also on the type of surface to which they are to be applied.

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6.2. Shut-down If gunning must be stopped, either temporarily or because the job is finished, a strict sequence of operations must again be followed and is the same for all machines : 1.

Stop the product flow by stopping the rotor

2.

Allow all the product in the delivery hose to flow out

3.

Close the water valve when no more product flows from the nozzle

4.

Close the air valve

At the end of a job, the machine must be emptied and cleaned before transport. However, if only small quantities of product have been gunned, there is no need to carry out complete maintenance. Nonetheless, the nozzle and the water valve must be cleaned with compressed air and water to ensure they are completely empty.

6.3. Gunning A.

Gunning vertically

When gunning on a vertical wall, the nozzle should be pointed downwards at approx. 45° at chest height. A small circular movement should be used. Always try to produce the complete thickness of the lining when gunning from the bottom to the top of the zone. A reasonable cold-gunning zone would be 60-90 cm high by 150-180 cm wide. On a vertical surface, the product must be sufficiently dry to bind without slumping but sufficiently wet (i.e. plastic) to absorb all the particles projected. Its finish should be shiny and large diameter grains should be visible, bedded into the material. B.

Gunning horizontally

When gunning overhead, always try to keep the nozzle at approximately 45° to the surface. Project the material into the layer being formed, which should be kept as near horizontal as possible. Gun the layer as thick as the atmosphere or temperature and the product used will allow. If sufficient thickness cannot be obtained in a single pass, never allow a long time to elapse between successive passes. This also applies when moving on to another zone. When gunning overhead onto a casing it is essential to use adequate anchors.

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More water must be used for gunning onto a horizontal floor, to make the product more plastic and allow any small quantities of material rebounding sideways to mix in with the bulk of the gunned material. Less water must be used for overhead gunning and the surface of the product must have a slight satin finish. The air pressure should also be increased slightly to obtain firmer bonding. In any event, there is always more rebound in this case than in other applications. C.

General hints

NEVER APPLY GUNNED MATERIAL IN LAYERS OR USE A METHOD SIMILAR TO PAINT SPRAYING. If access to the gunning zone is difficult, reduce the product flow to avoid excessive rebound. Determine the best distance between the nozzle tip and the lining to achieve the best application of the product and minimise rebound. With the proper air pressure for the product and the resultant nozzle velocity, this distance is roughly 60-120 cm. Holding the nozzle too far back will generally cause excessive rebound and thus change the density significantly since coarse particles will be ejected. The new lining will therefore be excessively rich in fines.

6.4. Common mistakes - made by gunning teams -

Excessively high AIR / PRODUCT speed through the nozzle.

-

The wetting pipe (water ring,...) is not correctly cleaned.

-

Same comment on the cleaning of the machine feed mechanism between jobs.

-

The nozzle operator applies the product in layers parallel to the wall, in the same way as he would spray paint.

-

Insufficient co-ordination between the nozzle and machine operators.

-

The nozzle operator attempts to apply the lining but does not have enough room to work. Many of these recommendations are then neglected.

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E. WORKING INSTRUCTIONS FOR GUNNING CONCRETES 1. Delivery and storage RHI gunning concretes are delivered dry in humidity proof valve bags, 25 kg each. The package has to be stored at an ambient temperature of 20°C ± 5°C and to be protected against moisture.

2. Placement by gunning Both the products and the equipment must be carefully selected to use this technique since the flow must be uniform with a minimum of dust and rebound , for a perfect placement of the material. These factors depend just as much on the gunning machine characteristics and settings as on the gun-ability of the material. The best machine is the one which generates the most uniform flow.

3. Check list a for proper placement by gunning 3.1. Air supply Compressor: 10 to 15 cubic meters / min The supply hose from the compressor to the machine should be 1,5 inches (38 cm) inside diameter. The diameter should not be less then the diameter of the material hose.

3.2 Water supply Recommended: 8,0 bar. If this is not available, a water booster pump should be used. Install a ¾ inch inside diameter hose from supply to pump. Install a ½ inch inside diameter hose from pump to nozzle.

3.3. Material hose Recommended length of hose: Recommended diameter:

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minimum 30 meters. 32 mm (1 ¼ inch) to 38 mm (1 ½ inch)

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3.4. Nozzle assembly A hydromix nozzle should be used for good a hydration of the material. A needle valve (inside diameter 3/8 inch) should be used for the regulation of the water flow. The nozzle outlet should have the same inside diameter as that of the material hose to offer proper gauge reading on the velocity of material / air flow.

3.5. Procedure for gunning operation (Start up) a)

Supply machine with electricity (air when using an air-driven motor)

b)

Open water supply to nozzle (turn on water booster pump)

c)

Supply air for nozzle operation; regulate air flow on machine

d)

Start material feed system. Make sure that the flow of material . air is smooth without surging

e)

Adjust right consistency of material on nozzle. Material should be applied as wet as possible; the gunning material should have a shining surface.

3.6. Gunning a)

Vertical surfaces: The nozzle operator should apply the lining in its complete thickness at 45 degree angle from the wall, starting from the bottom using circular motions when applying.

b)

Horizontal surfaces (floor) Water supply and air pressure should be increased a little.

c)

Overhead gunning (ceiling) Water supply should be slightly reduced, air pressure slightly increased.

3.7. End of gunning procedure (shut down) a)

Stop material feed at the machine

b)

Increase air pressure from machine to nozzle to clean material hose.

c)

The nozzle man has to increase the water supply to flush out the nozzle, and to turn off the water when the section is clean.

d)

Stop the air supply in the material hose.

e)

Stop the water booster pump.

e)

Make sure that no material is left in the hose from the machine to the nozzle. Always clean the machine feed system and nozzle assembly (water ring) at the end of a shift or days work.

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F.

WORKING INSTRUCTIONS FOR INSULATING CASTABLES

The RHI insulating / light weight castables can be installed by casting, ramming or gunning. The correct application method can be found in the technical datasheets.

1. Delivery and storage Insulating castables are delivered dry in packages protected against moisture. Insulating / light weight concretes are, like all hydraulically bonded gunning / casting mixes, very sensitive to moisture. It is possible that, under the wrong storage conditions, the material will begin to bind in the package. Therefore the material has to be stored frostfree at temperatures of around 20 ± 5°C and protected against moisture. Under these conditions the shelf life is at least 8 months. The precise lifetime can be found in the technical datasheets. If the castables have hardened during storage and contain lumps, which cannot be crushed by hand, the material should not be used under any circumstances, because the binder may already have reacted. Never stack more than 3 pallets on top of another !

2. Amount of water and its temperature These castables have to be mixed in a suitable mixer with potable water with a temperature of about 15 to 25 °C. The exact amount of mixing water can be found in the technical datasheets. Usually the amount is given in litres / 100 kg dry mix.

3. Mixing and casting Contamination of the concrete has to be avoided, so only clean and faultless units may be used. To achieve an even grain distribution mix the castable without water for 30 seconds. After this dry-mixing-period add the mixing water. The stipulated amount of mixing water may be varied by a maximum of ± 5 % to achieve the optimum consistency. MIXING TIME:

3 minutes check consistency of first mixtures observe equal mixing periods, to achieve uniform consistency

POT LIFE:

Install prepared mixes immediately (within 20 minutes); mixes which are about to set, must not be used

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TEMPLATES:

Only use dense and stable templates; make templates water-repellent before casting

PLACEMENT: Casting and rodding: The consistency is ok when you can press water out of the castable by hand. Do not compact the castable too much, the insulating properties would disappear. Casting and slight vibration: The more dense light-weight castables may be vibrated slightly when installing. Do not compact the castable too much, the insulating properties would disappear. Ramming: When the insulating castables are installed as “back-fill” mixes by ramming, it is recommended to keep a drier consistency.

4. Placement of insulating concretes by gunning Both the products and the equipment must be carefully selected to use this technique, because, for a perfect placement of the material, the flow must be uniform with a minimum of dust and rebound. These factors depend just as much on the gunning machine characteristics and settings as on the gun-ability of the material. For regards about gunning refer to “chapter D: Application by gunning”

5. Setting time At ambient temperature (15 - 20 °C): 6 -8 hours The setting time may be longer at lower temperatures and shorter at higher temperatures.

6. Drying and heat-up Drying:

At ambient temperature: 24 - 28 hours Heating up with 10 - 30 °C/h to 150 °C Holding time at 150 °C approx. 24 hours (about 1 h/cm wall thickness)

Heat-up:

Up to 500 - 600 °C with 10 - 30 °C/h Holding time at about 500 °C approx. 12 hours (0,5 h/cm wall thickness) Up to operating temperatures with 30 - 50 °C/h

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G.

WORKING INSTRUCTIONS FOR MORTARS

1. Product characteristics RHI mortars / mastics are mixes containing ceramic non-basic refractory raw materials of very fine grains. The mortars are used for the installation of refractory bricks. The mortars can have a ceramic, chemical or hydraulic bonding system. In the product range of RHI three different types of mortars / mastics are available. Dry mortars which have to be prepared with potable water Dry mortars which have to be prepared with a special mixing liquid “Ready for use” mastics The different types of mortars / mastics demand different processing, e.g. the shelf life and the working instructions differ considerably. Group 1: These refractory mortars are dry batches which are mixed on site with potable water only. The ceramically-bonded mortars develop their strength at higher temperatures due to sintering. A chemical or hydraulic bond ensures high strength already at low temperatures. Group 2: These mortars are dry mixes. For the mixing of these products special liquids have to be used. These mixing liquids are either based on sodium silicate (DIKASIL) or phosphate (DIFOSIL). Group 3: Mastics of this group are delivered “ready for use”. The mixing liquid is already admixed to the material.

2. Delivery and storage; shelf life All mortars, also these which have to be mixed with special mixing liquids, are delivered dry in packages protected against moisture. The mixing liquids DIFOSIL or DIKASIL are supplied in separate plastic holders. “Ready for use” mastics are delivered in plastic buckets (hobbocks).

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Group 1: These mortars have to be stored frostfree at temperatures of around 20 ± 5°C, and protected against moisture. Under these conditions the shelf life is at least 6 months. The precise lifetime can be found in the technical datasheets. Group 2: The mortar and the mixing liquid have to be stored at temperatures of 20 ± 5°C and protected against humidity and frost. The mortar is resistant to frost but nevertheless has to be used frostfree. Under appropriate storing conditions these mortars have an unlimited shelf life.

If the mixing liquid is frozen it has to be brought to room temperature slowly. The binder may only be used, if - after thorough mixing - no lumps can be found. The mixing liquids DIKASIL and DIFOSIL have an unlimited shelf life (under appropriate storing conditions). Group 3: The hobbocks have to be stored at an ambient temperature of 20 °C ± 5 °C and to be protected against frost. If the mortar, despite all measures taken, was frozen, it nevertheless might be used - if, after proper mixing, no lumps can be found in the mastic. A defrosting must be undertaken at ambient temperatures; because at temperatures above 30 °C the mastics tend to bind in the buckets. Therefore it is important to store the mastic at temperatures under 30 °C !!

3. Preparation and mixing Group 1: These dry mortars have to be blended properly with potable water (temperature 15 to 25 °C) in a suitable paddle mixer. (When mixing smaller quantities a whisk or beater may be used). The exact amount of mixing liquid can be found in the technical datasheet. Usually the amount is given in litres / 100 kg dry mix. To reach the optimum consistency a mixing period of 5 minutes has to be adhered to. If necessary, water or dry mortar powder can be added to reach a perfect consistency. Group 2: These dry mortars have to be blended properly with the delivered mixing liquid in a suitable paddle mixer. (When mixing smaller quantities a whisk or beater may be used). The exact type and amount of mixing liquid can be found in the technical datasheets. Usually the amount is given in litres / 100 kg dry mix. To reach the optimum consistency a mixing period of 5 minutes has to be adhered to. If necessary water or dry mortar powder can be added to reach a perfect consistency.

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Group 3: These mortars of above mentioned types are “ready for use” (that means the binder is already added to the dry mix). Due to the special composition of these mixes these mastics tend (like most phosphate-bonded jointing materials) to harden during storage. Nevertheless these mastics can be brought to a user-friendly consistency by intensive mixing. If mixing liquid can be seen at the surface of the material, the liquid may not be spilled, rather this liquid has to be mixed into the material again. Slightly stiffened mastic can be blended with potable water to achieve a userfriendly consistency. Hardened un-plastic mastic is no longer suitable for use and has to be deposited.

For all mastics it has to be observed, that the buckets have to be properly closed when breaks are made. This has to be done to prevent a drying of the surface of the mastic. Due to air contact hardened mastic is unfit for use.

4. Setting behaviour: The setting time of the single mortars depends very much on the bonding system. Therefore it is difficult to specify a commonly valid schedule.

5. Drying and Heat-up For drying and heating up of the mortars no special measures have to be taken. Rather the instructions for the heat-up of the installed bricks (the whole aggregate) have to be followed.

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H. ANCHOR-SYSTEMS The material selected for the support is just as important as the shape of the support in lining design. For instance, at high temperatures the mechanical strength of metal fittings decrease and the fittings corrode more rapidly. Thus, the support material selected must provide adequate thermal resistance and a longer service life besides conforming to the design specifications. In selecting the material for a support, the design engineer should start with the temperature to which the tip of the support embedded in the lining will be exposed. As this is extremely difficult to obtain experimentally, it should be predicted from the lining temperature gradient obtained by calculating lining heat transfer.

1. Criteria for the selection of lining support material Basically, the choice of the anchoring system is mainly determined by the maximum temperature of the monolithic lining to be expected:

Temperature of support tip less than 450°C

Support material Metallic anchor (carbon steel)

900°C

metallic anchor alloy AISI 304 (18 Cr - 8 Ni)

1100°C

metallic anchor alloy AISI 310 (25 Cr - 20 Ni)

>1250°C

ceramic anchor (SK 36 / fireclay)

>1450°C

ceramic anchor (SK 38 / andalusite; bauxite)

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2. Examples for lining supports

metallic anchor

ceramic anchor

insulating plate insulating brick ceramic anchor castable / gunning mix

a

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b

c

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3. Metallic anchors 3.1. Distribution of metallic anchors in vertical linings (walls)

v

a

a

a a a a

a

a

a

H

Recommendation lining thickness (mm)

anchor length H (mm)

distance a (mm)

number of anchors per m2

150

125

150

49

175

150

175

36

200

175

185

30

225

200

200

25

250

225

250

16

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v

3.2. Distribution of metallic anchors in horizontal linings (ceilings)

H

a

a

a

a

a

a a a a

Recommendation lining thickness (mm)

anchor length H (mm)

distance a (mm)

number of anchors per m2

75

50

130

60

100

75

150

45

125

100

150

45

150

125

160

39

175

150

170

35

200

175

185

29

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3.3. Types of metallic anchors Various anchor types are on the market, the most important ones are described below. All types have in common that they are made from round steel bars with a diameter of 8 mm or 6 mm.

3.3.1. Anchors to be used for linings with insulation Anchor types HTP / CTP / HTH / CTH

TYPE

CTP.6

L

75 - 200

A

Material

Plastic caps

304

K

35 - 100

FER 126

309

310

CTP.8

150 - 300

35 - 150 330

FER 168

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TYPE

L

A

HTP.6

100 - 200

35 - 100

Material

plastic caps

304

K

FER 126

309

K 310

HTP.8

150 - 300

35 - 150 330

FER 168

Anchors of the twin pin series are perfectly suitable for anchoring of multiple layer refractory linings. The twin pin anchor of type P can be fastened by the stud welding method, type H is for manual welding only. The insulation is simply to be applied over the anchor and anchor ends projecting beyond the insulation are then bent open over the washers provided. Types CTP / CTH with its corrugation provides a greater retaining capacity for the refractory material. Types HTP / HTH is notable for its deeper corrugations which produce a further improvement in retaining capacity.

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3.3.2. Anchors to be used for linings without insulation Anchor types CH1 / CH2 / CH3

TYPE

CH2.6

L

α

65-145

70°

150 - 250

60°

Material

plastic caps

304

K

309

K 310

CH2.8

85 - 145

70°

150 - 250

60°

330

The CH series is a anchoring system designed for fastening by manual welding. CH anchors are perfectly suitable for anchoring of single layer refractory compound linings When a gunned insulating layer is used, two layer wall claddings can also be anchored very well. As type CH1, the anchor is used for simple anchoring functions, e.g. with relatively light materials or in flat positions Type CH2 with its corrugation provides a greater holding capacity for the refractory material. Type CH3 is notable for its double corrugation, which provides a further improvement in anchoring strength.

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3.4. Anchor-material: Mainly the following alloys are used:

AISI-No. Material code Max. temperature Chem. Composition C Cr Ni

AISI 304 1.4301 750 °C

AISI 309 1.4828 1100 °C

AISI 310 1.4841 1200 °C

< 0,07 % 17,0 - 19,0 % 8,5 - 10,5 %

< 0,2 % 19,0 - 21,0 % 11,0 - 13,0 %

< 0,2 % 24,0 - 26,0 % 19,0 - 22,0 %

For the anchoring of refractory materials, in addition to ceramic anchors, predominantly metallic systems have always been used. Apart from a number of special applications, the use of metallic anchors is appropriate and economical. Up to a temperature of 750 °C AISI 304 can be used. This alloy has a good corrosion resistance, but should not be exposed to frequent and severe temperature fluctuations. AISI 309 represents the standard alloy for most applications in a cement line, since this material can work at temperatures of up to 1100 °C. For the highest temperatures in a cement line, preferably AISI 310 is used as a kind of standard material.

3.5. Welding electrodes For the anchor material AISI 304/ AISI 309 and AISI 310 the following electrode type is recommended (there are many similar brands from various manufacturers on the market): for example:

ESAB type OK 6713 DIN 8556 ISO 3581 E19.12.3 LR rutile-encircled, basic

chemical composition:

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C Si Mn Cr Ni

0,1 % 0,5 % 1,7 % 26,0 % 21,0 %

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I.

DRYING AND HEAT-UP INSTRUCTIONS

1. Drying of Preheaters and Heat Exchangers In most cases the rotary kiln start-up is done with the main burner. However, newly lined kiln hoods, heat exchangers or coolers must be dried separately. This is especially the case if larger areas have been lined with refractory castables. In a modern multi-stage cyclone preheater several tons of refractories may have been installed. The total amount of refractory castables and mortars and, consequently, the share of bonded water can be quite high in such plants. This amount of water must have the possibility to vaporise slowly during the drying procedure. ♦ Too quick heat-up will always effect in preliminary damage to the refractory castable sections and the brickwork. The damage is caused by the extremely high steam pressure. For separate heat-up of the heat exchanger the use of fuel oil burners has provided good results. Heating is done via the man holes in the inlet chamber. The arrangement of the auxiliary burners must be discussed and co-ordinated with the local plant management. This will ensure that a uniform heat distribution is applied across the entire heat exchanger. If a uniform heat distribution is not possible with a single burner due to the design of the plant, it will be necessary to install further auxiliary burners in the lower areas of the different locations that must be dried properly. The flame must always be positioned in the middle of the free gas duct cross-section so that the refractory brickwork is not touched directly. The maximum fuel throughput of the auxiliary burner should be about 5 % of the entire fuel amount of the plant with a controllability of 1 : 10. Peepholes, poke holes and man holes must stay closed during the drying and heat-up procedures. However, the flap valves and meal ducts must stay open. It must also be checked if all passage areas and screens are open and the heat exchanger has been cleaned in order to avoid any leftover building materials or breakout materials from causing disturbances later on.

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IMPORTANT! The setting time of the refractory castables is at least 24 hours. For refractory castables, which have just been installed, it is not possible to start with drying procedures until setting (hardening) has been completed.

Mercury thermometers are used for checking the temperature of the refractory brickwork in the preheater unit. It is also possible to use other suitable temperature measuring equipment with a measuring range of 0 °C to approx. 350 °C. Refer to the enclosed sketch SK 01 for more details regarding the arrangement of temperature measuring spots. The measuring spots must be in easily accessible areas and slightly above head so that the measuring equipment is not damaged when walking by. The brickwork temperature at the back side of the wear lining must be at least 100 °C. 3 days will be at least required for the drying procedure. 5 days will be required if larger amounts of refractory castables have been installed. Drying and heating-up are effected by way of the natural draft of the plant. If the natural draft is not sufficient, the exhaust or filter fan must be turned on with minimum performance or smallest flap positioning (setting). The heat-up speed should not exceed 5 – 10 °C / h. During the first day a temperature of approx. 110 to 120 °C will be achieved. This can be increased during the next 2 days up to approximately 160 °C. From then on heating-up is conducted uniform to the maximum temperature. The temperature at the brick hot face may not exceed 400 °C. Smaller auxiliary burners can be used for drying out the plant. These auxiliary burners must only be operated with a small fuel amount, e.g. : •

Maximum fuel consumption of the plant in continuous operation:

•

Auxiliary burner performance 5 % of that:

•

Controllability 1:10

Installation Guide NU.DOC

10,000 l/h fuel 500 l/h fuel 50 l/h fuel

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The fuel amount should only then be increased when the temperature does not increase further over a certain period of time. It should be the objective of the drying procedure to obtain temperatures above 100 °C in the uppermost heat exchanger area. Then one can assume that there is hardly any water left in the hot face brickwork area. An inside wall temperature of approximately 350 °C should be reached in the area of the auxiliary burners. This temperature can be checked regularly with an optical hand-size pyrometer. Complete drying of the rear brickwork is usually not accomplished until continuous operation, because during drying, especially in thicker lined areas, it is not possible to reach 100 °C at every spot. If they do not exist, evaporation hatches should be installed on the cyclone roofs as illustrated in Sketch SK 03. The evaporation hatches must be kept open during the drying and heating-up procedures. These hatches must not be closed again until it is certain that all water in the brickwork has completely evaporated.

2. Drying of kiln hood, tertiary air duct and cooler If larger wall sections in the kiln hood, tertiary air duct or cooler have been lined with refractory castables, these plant sections must be dried separately over a time period of at least 3 days. Consequently, the drying procedure starts 4 days before the intended heating-up date for the kiln. This means that there is one “idling” day between the end of drying and the start of heating-up the kiln. This day will be needed to remove the auxiliary equipment needed for the drying procedure. The maximum amount of fuel needed is about 5 % of the fuel needed for drying the heat exchanger. The auxiliary burners must also have a controllability of at least 1:10. The brickwork temperatures are controlled the same way as in the heat exchanger (sketch SK 01).

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The brickwork temperature at the back side of the wear lining must be at least 100 °C. Heatingup speed should not exceed 5 – 10 °C / h. During the first day a temperature of approximately 110 to 120 0C will be achieved. This can be increased during the next 2 days up to approximately 160 °C. From then on heating-up is conducted uniform to the maximum temperature. The temperature at the brick hot face may not exceed 400 °C.

2.1 Auxiliary Burner for Drying the Kiln Hood: If only the kiln hood has to be dried the burner is preferably positioned in the side manholes of the kiln hood. The flame must point upwards and below the kiln roof. In order to prevent moist waste gas being pulled through the kiln it will be necessary to install some sealing material at the kiln discharge end. There must be some protection against overheating with ceramic wool mats at the kiln hood side. After completion of the drying phase the kiln hood doors are opened and the sealing material in the kiln removed as soon as access is possible.

2.2 Auxiliary Burner for Drying the Tertiary Air Duct: If drying a tertiary air duct connected to the kiln hood, the upper air flap and the tertiary air slide gate must be opened before the start of drying. For drying it is recommended to install an auxiliary burner sitting on a carriage on the reciprocating grate plates in the cooler shaft area. In this case the flame of the burner should be directed straight upwards (refer to sketch SK 05). Beforehand it is very important that the kiln discharge end is equipped with sealing material as already described in the chapter above. The exhaust air flap of the cooler must be closed in order to prevent counter streams flowing in direction of the cooler.

If the tertiary air take off duct is positioned in the roof area of the hot chamber in the cooler, then it is possible to install a carriage holding the auxiliary burner below this take off duct on the cooler plates. Here, too, it is important that the exhaust flap of the cooler is closed (refer to sketch SK 06).

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2.3 Auxiliary Burner for Drying the Cooler: For drying the cooler the auxiliary burner is preferably positioned in the side manholes. The flap for the exhaust air is to be completely opened so that a natural draft in direction of the cooler is generated. If the natural draft is not quite sufficient, especially if this is the case after the burner starts operation, then the ventilator for the cooler exhaust air should be operated in addition with the flap opened only a little bit. In order to prevent one-sided overheating of the hammer crusher it must start operation before igniting the auxiliary burners.

3. Heating-up the rotary kiln Do not start with drying and heat-up procedures for the rotary kiln until all repair work has been completed. This will ensure commissioning without any disturbances. If tertiary air duct, cooler and kiln hood have been dried, they can be heated-up - together with the rotary kiln by using the main burner.

3.1 Preparation Measures Please adhere to the details indicated in sketch SK 07 during the heat-up phase. It is recommend not to put raw meal in the kiln before heating-up. The raw meal stays on the lower part of the rotary kiln and prevents uniform heat-up of the brickwork in this area. If the kiln is rotated the cold brickwork is immediately in contact with the hot gas atmosphere. The tremendous temperature shock can cause premature wear on the refractories, with spalling as a result. It is recommended to feed approximately 20 tons of raw meal about 4 hours before the final feed, so that a protective coating can be built up on the refractory lining. If working with oil-fired burners during the heating-up procedure pay attention that the oil is preheated according to the instructions given by the suppliers.

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3.2 Heating-Up the Entire Plant Peepholes, poke holes and man holes remain closed during heating-up. The flap valves of the meal ducts must be open. The evaporation hatches in the upper areas of the cyclones and gas ducts must also be open (refer to sketch SK 03). It must be checked if all gas passage areas are open. Make sure that the plant has been cleaned beforehand so that leftover building or breakout materials do not cause disturbances during heating-up or during regular operation. If an ignition burner is not at hand for heating-up, it will be necessary to install an auxiliary burner (as shown in sketch SK 02) to generate a support flame. This flame must burn until the kiln becomes hot enough (dark red heat/glow). Then it is ensured that the main flame will maintain itself. The support flame also helps to stabilise the main flame when the kiln is still in a cold state. Heating-up starts with a fuel throughput which does not exceed 5 % of the maximum fuel consumption in continuous operation: Max. fuel consumption of the plant in continuous operation: Auxiliary burner (performance 5 %) for the heat-up: •

10,000 l/h fuel 500 l/h fuel

These figures (counts) must be converted for other fuels.

Heating-up of newly lined plants should be generally done as indicated in sketch SK 07.

Kilns, in which large sections have been newly lined with refractory castables (e.g. long wetprocess rotary kilns), need an additional setting time of 24 hours. During the drying phase the temperature must be kept at 110 °C to 200 °C in the corresponding zones.

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3.3 Temperature Control It is very important to continuously record the temperatures and other occurrences during heating-up. Special attention must be given to the parameters that must be checked for the kiln shell temperature and kiln feed end temperature (chain zone temperature in long wet-process rotary kilns) as well as the pressure at the kiln hood. The measurement of feed end temperature and pressure at the kiln hood is part of the system. An optical hand-size pyrometer is suitable for measuring the kiln shell temperatures. For this measurement it is best to mark a line as measuring point every two meters on the kiln shell or railing. This must be done before heating the kiln up. This procedure ensures a precise determination of the measuring points later on. The measured temperatures should be recorded in a special record book every hour during the entire heating-up phase. If not determined otherwise, the details indicated in the heat-up schedule (sketch SK 07) apply for the temperature of the brick’s hot face in the burning zone. Since most kilns do not have suited integrated measuring equipment, the kiln shell temperature in the specific zones must be measured regularly with an optical hand-size pyrometer. The gas temperature in the inlet chamber must be checked, too. The heat-up speed for newly lined kilns may not exceed 25°C / hour during the first 24 hours and may not exceed 30°C / hour after this period. The gas temperature measured in the inlet chamber serves as measuring value (count) for the control of the heating-up procedures applied for all kiln types. The relation between brick temperatures in the burning zone and exhaust temperature in the inlet chamber serves as an example: Temperature/inlet chamber for idling operation: Corresponding temperature / burning zone:

800 °C 1,200 °C

Temperature increase in inlet chamber:

20 °C

Temperature increase in burning zone:

30 °C

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A certain check is possible by measuring the shell temperature. The temperature inside the kiln can be calculated mathematically and is illustrated in sketch SK 05. It is important that this check reacts in a sluggish way and only provides indications since the shell temperature is also dependent on wind movements. Pay attention to the following points during the heat-up procedure. •

Do not increase the fuel amount for the main burner until the temperature in the plant no longer rises. Set the draft in the plant so that: ♦

the share of cold secondary air stays as low as possible;

♦

no CO is generated during combustion;

♦

combustion heat mainly stays in the sintering zone;

♦

the flames burns short, compact and uniform;

♦

there is no direct contact between flame and brickwork.

3.4 Rotation of the kiln during the heat-up phase Any rotation of the kiln must be limited to the least extent possible during the heat-up phase. The first rotation should not be earlier than 4 hours after ignition. For a partial rotation of the kiln it is sufficient to turn it by ¼. The rotation intervals are indicated in sketch SK 07. This curve also indicates the time period for the subsequent partial charging with raw meal and the final charging. A continuous turning of the kiln is not possible until the brickwork has expanded sufficiently and sits tight as a result of its thermal expansion. In this case the rotation speed should not be less than 10 minutes for each rotation at the start. If the kiln is rotated continuously it is important to observe the relative movement between the kiln shell and tire (applies only for loose tires). During the heat-up phase it can happen, especially on the tire at the discharge side, that there will be contractions in the kiln shell as a result of varying expansion speed between tire and kiln shell. The brickwork is subjected to extreme stress and therefore often damaged prematurely. The measured values (counts) of relative movements must also be recorded in the record book. Measurement can be conducted with chalk lines on the tire and kiln shell or with installed measuring systems.

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If there should be no relative movement after several rotations it will be necessary to reduce the fuel amount on the main burner. The fuel amount should not be increased until the tire has warmed up correspondingly and no longer sits tight. The required time for heating-up the plant can be much longer if the tires are of massive build.

3.5 Disturbances and Repeated Heating-Up Every cooling down and heating-up procedure is dangerous for the refractory lining. This interaction is especially critical if the lining does not yet have a protective coating. If disturbances occur during the heat-up phase it is recommended to continue to heat up the kiln to 1.000 °C in the burning zone. This is very important if more than 1/3 of the entire heat-up phase has been completed. The kiln should be kept at this temperature under the condition that the delay will not last longer than 2 to 3 days. During this procedure the kiln must be rotated slowly every 2 hours by ¼ of the kiln’s circumference. If still in the first 1/3 of the normal heat-up phase, it is recommended to interrupt the heat-up program with subsequent slow cooling down of the kiln. If in the second or last third of the entire heat-up phase, the kiln must be cooled down according to chapter 4 if the disturbance are expected to last longer than 2 to 3 days.

4. Shutdown of the kiln Cooling down speed should not exceed 50 °C / h. This will enable a shutdown of the kiln within 24 hours. Cooling of the kiln is to be accomplished mainly by heat radiation. At the start of cooling down the flap position (setting) of the exhaust gas and filter ventilator must be closed to an extent until a pressure of ± 0 forms at the kiln hood. This must be regulated (set) until there is a dark red heat (glow) in the burning zone. At the end of the cooling down procedure the flap of the ventilator can be opened again. During the cooling down procedure the kiln is rotated with a minimum rotation speed until achieving a dark red heat (glow). Once achieving dark red heat (glow) it is possible to rotate the kiln by ¼ of it’s circumference every

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2 hours until it is completely cold. The kiln must not be rotated any longer once the shell temperature has reached less than 100 °C in the burning zone.

Important ! Too quick cooling down of the rotary kiln by using cold air (opening of the flaps on the kiln hood) or spraying water is not permitted. These methods accelerate the cooling down procedure. However, such procedures tremendously intensify wear and stress on the refractory bricks. This will cause spalling. The refractory brickwork must be carefully checked after each complete cooling down of the kiln. If the bricks are loose in some areas it is possible to use shims which, however, can not be thicker than 2 mm. You should not use more than 5 shims per brickwork ring. Never install more than one shim per joint.

5. Important points The kiln may not be rotated in cold state because otherwise the stability of the brickwork will be endangered. If using the jack method for lining the kiln it is important not to rotate the kiln more than absolutely required. All reference temperatures refer to the hot face temperatures of the refractory lining in the burning zone (flame zone) if not indicated otherwise. The guidelines and instructions for heating-up rotary kilns only apply for kilns in which the refractories have been installed properly. It is recommended to immediately consult the refractory supplier should there be any modifications or deviations regarding the heat-up instructions during execution of drying or heat-up procedures.

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6. Error sources when rotating rotary kilns ⇒ Too early rotation: Effect: loosening of lining, twisting of lining Measures: rotation interval according to heat-up curve SK 07 ⇒ Too late or not enough rotation Effect:

one-sided heating, intensive thermal shock during rotation, specifically upon passage (flow) underneath cooler material, damage of kiln bearings possible. Measures: rotation interval according to heat-up curve SK 07 ⇒ Too frequent rotation during heat-up phase Effect: strong relative movement of brickwork, loosening and twisting of lining Measures: rotation interval according to heat-up curve SK 07 ⇒ Too quick heat-up Effect:

spalling of bricks, contractions in kiln shell in the tire area due to slower heating of tire Measures: reduction of main flame, pay attention to heat-up speed, continuous check of relative movements of tires ⇒ Too quick drying Effect:

steam pressure in brickwork, spalling if using refractory castables. IMPORTANT! Allow at least 24 hours setting (hardening) time for refractory castables. Measures: observe drying times, preliminary drying with auxiliary burners ⇒ Insufficient cooling of discharge end segment Effect: loosening of nose ring by thermal expansion of kiln shell Measures: ensure operation of cooling air ventilators (only with continuous rotation of kiln) ⇒ Interruptions during heat-up phase Effect:

loosening of lining, open expansion joints with already burned out expansion cardboards, twisting of lining and/or downward sliding of the lining Measures: careful preparation of commissioning, careful rotation of kiln, meal feed during heat-up phase to block open expansion joints

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Temperaturmeßstellen „M“ Temperature measuring spots “M“

Blechmantel / Shell

Loch / Hole ∅ 8 – 10mm

Thermometer

Mauerwerk / Brickwork

SK 01

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Isolierung / Insulating Material

Anordnung der Temperaturmeßstellen Arrangement of Temperature Measuring Spots

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a) Kurze Brennerlanze / Short Burner Lance

Gas Brennerlanze / Lance ½“

b) Lange Brennerlanze / Long Burner Lance

Gas

Brennerlanze / Lance ½“

Schnitt A-A / Section A-A Draht / Wire

Öse / Eye

Lanze / Lance

SK 02

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Befestigung eines Hilfsbrenners Attachment of Auxiliary Burner

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Isolierung / Insulation Beton / Castable

SK 03

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Anordnung der Entdampfungsstutzen auf den Zyklondecken Arrangement of the evaporation hatches on the cyclone roofs

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Futterstärke / Lining Thickness [mm] Temperatur der Steinkopfoberfläche (Ansatzfrei) Brick’s Hot Face Temperature (Coating free) [0C]

1.000

800

600

400

200

0

100

200

300

400

500

Ofenmanteltemperatur / Shell Temperature [0C]

SK 04

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Manteltemperaturen von Drehrohröfen Kiln Shell Temperatures

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Temperaturmeßstelle Temperature Measuring Point Tertiärluftleitung Tertiary Air Duct Ofenkopf Kiln Hood

Kühlerabluft Exhaust Air

Abdichtwand Intermediate Wall Hilfsbrenner Auxiliary Burner

SK 05

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Hammerbrecher Hammer Crusher

Trocknen einer Tertiärluftleitung am Ofenkopf Drying of a Tertiary Air Duct, connected with the Kiln Hood

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Temperaturmeßstelle Temperature Measuring Point Tertiärluftleitung Tertiary Air Duct Ofenkopf Kiln Hood

Kühlerabluft Exhaust Air

Hilfsbrenner Auxiliary Burner

SK 06

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Hammerbrecher Hammer Crusher

Trocknen einer Tertiärluftleitung am Kühler Drying of a Tertiary Air Duct, connected with the cooler

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Ofendrehung Kiln Rotation

Aufheizdiagramm für Drehöfen Heating-up curve for Rotary Kilns 1.600 Nach einem Kurzstillstand < 8h After short Shutdown < 8h

Nach Neuauskleidung After new Installation

1.400

≈1000C/h

≈800C/h

1.200 Rohmehlaufgabe / Kiln feeding ca. / approx. 20 to

1.000

≈300C/h

800

≈250C/h 600 Ofenleistung Kiln Capacity

400

< 2,500 t/d

200

>=2,500 t/d

0 0

2

4

6

8

10 12 14 16 18 20 22 24 26 2 8 30 32 34 36 38 40 42 4 4 46 48 50 52 54 56

Stunden / Hours [h]

SK 07

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Aufheizdiagramm für Drehöfen nach erfolgter Trocknung des Vorwärmers Heating-up Curve for Rotary Kilns Valid after Drying the Preheater

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