Coal Feeder Operation

Tanjung Jati B Training COAL FEEDERS Coal Fired Boiler Design & Performance.1

PT Central Java Power Tanjung Jati B Units 1 & 2

2 x 660MW (net)

Boiler

Precipitator

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OPERATIONS COAL FEEDERS

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Coal Feeders Location

COAL SILOS

COAL FEEDERS

PULVERIZERS

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Coal Feeders

Coal Feeders receive coal from the Coal Silos and control the amount of coal delivered to the Pulverizers. The Coal Feeder is called a “Gravimetric” feeder because the feeder weighs the coal as it travels on the belt or conveyor.

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Coal Feeders Equipment associated with the coal feeder… Stainless Steel Enclosure Downspouts Outlet Chute Discharge Switch “Coal on Belt” Switch Conveyor (Belt) & Drive Motor Cleanout (Scraper) Conveyor & Drive Motor Load Cells & PLC with Microprocessor Belt Tracking Switches Inlet & Outlet Gate Valves Acoustic Emission Flow Detector Seal Air Connection Coal Fired Boiler Design Performance.6 Tanjung Jati& B Training

Coal Feeders Associated Equipment An Acoustic Emission Flow Detector is located between the Coal Silo & the Inlet Gate Valve

Merrick Gravimetric Feeder has a maximum design output of 68.5 metric ton/hour

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Coal Feeders Internals

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Coal Feeders Operation Modes

There are two (2) modes of metering or measuring the coal flow to the pulverizers… …Gravimetric and Volumetric…

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Coal Feeders Operation Modes Gravimetric operation weighs the coal as it travels along the belt. This is the primary mode of operation and provides a more accurate measurement of coal flow. Volumetric operation measures the volume of the coal on the belt. Coal density (kg/m3) must be known for either mode to operate properly.

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Coal Feeders Load Cells & Microprocessor The Microprocessor or Merrick MC3 Controller is located in a control panel which is mounted on the side of the Feeder and is used for the control of the process weighing equipment. The controller is equipped with an LCD display. The DCS interfaces with the Controller to regulate the feeder speed as required.

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Coal Feeders Load Cells & Microprocessor The LCD display has a touch pad screen which allows an operator to monitor Feeder conditions while in service. Various “sub menus” allows an operator to set control parameters, perform calibrations and other functions.

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Coal Feeders Load Cells & Microprocessor Some of the information provided by the Controller’s LCD display include… Feeder Status Feeder Speed Current Coal Feed Rate Historical or Total Coal Flow Calibration Information Date & Time…

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Coal Feeders Load Cells & Microprocessor Each Feeder has two (2) Load Cells which provides information to the Controller in order to calculate the weight of coal on the belt. If there is a failure of one of the two Load Cells, the controls default the mode of operation to Volumetric measurement of coal flow.

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Coal Feeders Conveyor Belt & Drive Motor

The Conveyor Belt transports the coal from the Inlet Chute to the Discharge Chute, and is made of vulcanized rubber. The Coal Feeder is driven by a 3-phase, 1 HP, AC motor with a gear reducer.

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Coal Feeders Belt Tracking & Switches

Explosion proof, double-contact switches are located just before the coal feed inlet at the tail pulley. If the belt tracks to one side, the first switch will activate an alarm to alert the operator. If the belt tracks further off, the second switch will open and the PLC will stop the feeder before belt damage can or will occur.

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Coal Feeders “Coal on Belt” Switch

The Coal on Belt Switch is located downstream of the Feeder Inlet Chute. If no coal is detected, the Coal Feeder will trip after a delay of 120 seconds. When the Feeder trips the Pulverizer associated with that Feeder trips as well.

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Coal Feeders Chutes, Isolation Valves & Instrumentation

Both the Inlet & Outlet Chutes are equipped with motorized Gate Valves. The Inlet Gate Valve isolates the Coal Feeder from the coal silo. The Inlet Gate Valve has a chain to operate the valve if the motor should fail. The Outlet Gate Valve isolates the Coal Feeder from the Pulverizer.

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Coal Feeders Chutes, Isolation Valves & Instrumentation

The Inlet Chute above the Gate Valve has an Acoustical Flow Monitoring device which detects the loss of coal flow to the Coal Feeder. If a loss of coal flow is detected, an alarm will be activated. If loss of coal flow is real, the “Coal on Belt” Switch will signal an alarm shortly after that.

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Coal Feeders Chutes, Isolation Valves & Instrumentation

NOTE: The Outlet Gate Valve must be CLOSED before a pulverizer’s inert & clean sequence is is initiated. This prevents moisture and heat from entering the feeder and potentially damaging internal feeder components (load cells).

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Coal Feeders Chutes, Isolation Valves & Instrumentation

The Outlet Chute has a Discharge Switch which detects whether or not coal is flowing from the feeder. If “no coal flow” is detected, the feeder is presumed to be plugged, therefore the Feeder is commanded to stop. The Feeder is stopped in order to prevent coal accumulating within the feeder and causing potential damage.

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Coal Feeders Cleanout (Scraper) Conveyor The function of the Cleanout or “Scraper” Conveyor, which operates continuously while the feeder is in service, is to keep the bottom of the feeder clean of coal fines and coal which accumulates on the bottom of the feeder.

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Coal Feeders Start Up Prior to allowing the start of a Coal Feeder, all associated equipment must be available and no feeder alarms are present. An operator, at all times, should be at the Feeder during initial start. During the initial start of the Coal Feeder, the minimum flow rate of coal is expected to be approximately 18 tonnes per hour….

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Coal Feeders Start Up …However, the actual minimum coal flow rate will be determined during commissioning of the Boiler. Burner flame stability and Pulverizer operation play a part in determining the minimum coal flow rate.

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OPERATIONS COAL FEEDERS (END)

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