Coal Mill Ball Interlocks-v0.0

COAL GRINDING BALL MILL - CONTROL LOOPS V0.0 Controlled Parameter

Differential Pressure of mill

Separator Air Flow

Mill Outlet Gas Temperature

Static pressure at mill inlet

Final Product Fineness

Gas Temperature at mill inlet

Actuator

Target

Fresh Feeding Weigh Feeder

Optimisation of the production in terms of output and power consumption

Exhaust fan (separator fan) Variable Speed Drive or Ensure a constant quality of classification (for a constant adjustable Damper feeding of classifier)

Controlling the Fuel added to Hot Gas Generator or Hot gas generator damper/fan speed

Keep the T° in a narrow range between drying achievement and safety limits

Adjustable damper on recirculation duct (or on exhaust duct)

Allow complementary flow from recirculation. Optimisation of pressure load of fan

Classifier Variable Speed Drive

Constant product fineness

Water spraying device / Gas Flow Setpoint adjustment

Adjustment of drying conditions in order to allow a correct working of the control loops according to safety limits (O2, Temperatures)

LOOPS V0.0

DATA TO BE FILLED BY PLANTS Comments

To provide constant material flow through the mill, target mill throughput is given by operator in t/h

Gas flow measurement required (venturi, or equivalent). The minimal required mill ventilation is checked with mill DP calculation. The minimal air for material transport (lifting) is checked with a pressure sensor at the separator outlet.

Temperature set point should be adapted according to the fuel used (safety limits) and final product moisture target. Automatic safety value for actuator when coal mill main drive stops. Prefer cascade loop so that mill outlet temperature sets mill inlet temperature.

The location of adjustable damper can be accepted at stack but it's not recommanded (risks of overpressure in the circuit). The amount of air to be recirculated should be limited by the max O2 level accepted (according to the fuel used). The stack damper and recirculation damper must work in tandem. It's not a PID. The New Speed Set point can be directly entered by operator or calculated (Proportionnal calculation) according to fineness analysis and fineness set point A Control loop is not recommended. The setpoint of the actuator should be adjusted according to conditions (O2, Temperatures) in order to allow a correct working of the control loops. Water can be used to set the level of recycle needed - but not used for continuous control.

Control Loop Available in PCS (Y/N)

Control Loop in Auto/Manual

Reason for run in Manual Mode

Comments [if any]

COAL GRINDING BALL MILL - ESSENTIAL PROCESS INTERLOCKS V0.0 Process Group

All Equipment (isolating flaps are forced closed in stop conditions)

Raw Hopper Feeding

Raw Hopper extraction Hot gas fan

Coal Mill Feed

Coal mill main drive

Source of condition

Start Condition

Stop Condition

Delay for stop [seconds]*

Inerting sequence

COMPLETE

INCOMPLETE.

5*60

Not activated

Activated

3


> HH Activated >HH >HH >HH >HH

3 3 3 3 3 3


>HH

3

Inerting device wherever the zone area Hopper Analog Level Sensor Hopper digital Level Sensor Hopper Temperature sensor Hopper CO analyser Hopper Temperature sensor Hopper CO analyser Temperature at Hot gas fan inlet Coal Mill Outlet Gas Temperature Coal Mill Sound Level Coal Mill Power Raw Coal Hopper Level Temperature sensor at mill inlet Temperature sensor at mill outlet O2 Analyser at filter outlet All Fine coal bins level Temperature sensor at filter inlet Temperature sensor at filter outlet Differential Temperature calculation of filter

>L

N/A

>L

< LL < LL
3 3 3


>HH

3


>HH

3


>HH

3

>HH

3


>HH

3


>HH

3


>HH

3

O2 Analyser at filter outlet


>HH

3

CO Analyser at filter outlet Filter extraction Filter Hopper digital Level Sensor Explosion flaps Differential pressure calculation of filter Filter Hopper Temperature sensor Temperature sensor at mill inlet


>HH OFF

3 5*60

Not activated

Activated

3

Closed

Open

3


>HH

3


>HH

3


>HH

3

Process Filter Fan & Filter

Isolating flaps of aeraulic circuit (start = OK for open, stop = close)

Temperature sensor at mill outlet Temperature sensor at filter inlet Temperature sensor at filter outlet Differential Temperature calculation of filter Filter Hopper Temperature sensor


>HH

3


>HH

3


>HH

3


>HH

3


>HH

3


>HH

3


>HH > HH Activated >HH >HH Activated

3 3 3 3 3


>HH

3


>HH

3


>HH

3

O2 Analyser at filter outlet


>HH

3

CO Analyser at filter outlet Filter Hopper Temperature sensor Hopper Temperature sensor Hopper CO analyser Hopper level Hopper inerting device


>HH

3


>HH

3


>HH >HH >HH Activated

3 3 3

Raw coal hopper CO Analyser

>HH


Filter outlet CO Analyser Pulverised coal hopper CO Analyser

>HH


>HH


>HH


>HH


>HH


>HH


Activated
Not Activated > HH > HH

O2 Analyser at filter outlet

CO Analyser at filter outlet Hopper Analog Level Sensor Hopper digital Level Sensor Hopper Temperature sensor Hopper CO analyser Hopper inerting device Temperature sensor at filter inlet Temperature sensor at filter outlet Pulverized coal Hopper Feeding_filter extraction (stop ==> close isolating Differential Temperature flap) calculation of filter

Pulverized coal Hoper extraction to another bin

Raw coal hopper Temperature Inert gas injection (in the zone where there is an abnormal situation) Filter Differential Temperature sensor Filter hopper temperature sensor Pulverised coal hopper temperature sensor Manual inerting request Hot Gas Generator Outlet Gas Temperature Coal Mill Outlet Gas Temperature Hot Gas Generator Control Unit

Delay min according to the volume to be inertized (2kg of inert gas / m3 of volume)

3 3

Hot Gas Generator Control Unit

Coal Mill Inlet Gas Temperature Hot Gas Generator Outlet pressure

*Delay for stop:-

Note:-


> HH

3

Negative

Positive

3

3 seconds is proposed in order to avoid stoppage due to signal perturbation (can be increased/reduced according to site conditions) In general, delays can be adjusted according to site conditions/circuit configuration/OEM recommendation. Some limit values mentioned in comments are for ultimate safety. Operational limits needs to be set based on supplier/OEM recommendation or circuit configuration.

OCKS V0.0

DATA TO BE FILLED BY PLANT Comments

We have high risks during the stoppage of the equipment while inerting is not avalaible. We should give time to restart the inerting sequence before shutdown. Sequential shutdown is recommended. Except in the pulverized coal hopper if 2 hoppers existing and possibility to go to the non inertized hopper Avoid overfilling Avoid overfilling For each T° sensor. If existing For each T° sensor If existing

Mill must be heated up properly before giving feed Avoid overfilling of the mill. Avoid overfilling of the mill.

Depending on site conditions, H and HH can be different on starting conditions in order to allow start-up. Sequential shutdown is recommended

In order to allow the warmup of the workshop, H and HH are inhibited when hot gas fan is not started (+ delay). Depending on site conditions, H and HH can also be different on starting conditions. Sequential shutdown is recommended

Interlock Available in PCS (Y/N)

Value of Start Value of Stop Values of Condition Condition Alarm Limits

Sensor Operating Range Min Value

Sensor Operating Range Max Value

Existing Delay for Stop [Seconds]

Interlock Active /Bypass

In order to allow the warmup of the workshop, H and HH are inhibited when hot gas fan is not started (+ delay). Depending on site conditions, H and HH can also be different on starting conditions. Sequential shutdown is recommended

For each T° sensor If existing

In order to allow the warmup of the workshop, H and HH are inhibited when hot gas fan is not started (+ delay). Depending on site conditions, H and HH can also be different on starting conditions. Sequential shutdown is recommended

For each T° sensor If existing

Start after delay in order to confirm signal (3s suggested). For the hoppers the delay can be optmised taking into account the % of filling

For protecting the mill bearing and separator

To avoid HGG backfiring

o site conditions)

Reason for Bypass

Comments [if any]