Slop fired Boiler bag filter commissioning & shutdown procedure

Pre-Coating & Pre-heating

• Box – up the bag house and close all access doors properly.
• Keep the module outlet damper full open.
• Close the Bypass dampers 100%.
• Close the inlet damper 100%.
• Make sure that the lime injection system is ready
• Run the ID Fan and adjust the fan controls for effective suction for pre coating. (the air will flow from the boiler section .If required doors in the economizer section can be opened to draw fresh air into the bag filter)
• Run the ID Fan and adjust the fan controls for effective suction for pre coating. (the air will flow from the boiler section .If required doors in the economizer section can be opened to draw fresh air into the bag filter)
• Switch ON the lime injection system and start lime spray into the inlet duct. (Note : Dolomite powder can be used for pre coating)
• Do not start pulsing during this period.
• Observe the change in Differential pressure across the tube sheet.
• After sufficient pre coating, as observed from the Diff Pressure gauge, around 10-  15 mmWG increases, stop the pre coating. Record the readings.
• Stop the ID fan.
• Switch on the hopper heaters
• Switch on the Close Circuit heating system as follows
• Close the bag filter inlet & outlet dampers.
• Open the heating system inlet and outlet valves.
• Start the blower.
• Switch on the heaters.
• Allow the hot air circulation to push up the internal temp > 140 Deg C (Approx).

Bag filter start up

• Open the Bypass dampers both multi lower and puppet dampers by 100%
• Keep Bag filter inlet and outlet dampers closed.
• Ensure that the operation of dust conveying system below the hoppers is checked thoroughly and should be kept in operation
• Light up the boiler and take the exhaust gases through the bypass path.
• Continue with only coal firing.
• Once the gas temperature reaches 140 Deg C +, then take the bag filter in line
• Keep the BF pulsing OFF from the beginning
• Open the bag filter inlet and outlet dampers 100%
• Start closing the multi lower damper in the bypass line gradually, by maintaining the furnace pressure. This will divert the gas gradually through the bag filter. The ID fan speed will go up gradually. This process will take some time
• When the entire gas is diverted through the bag filter and the multi lower damper in the bypass line is fully closed, and then close the puppet damper in the bypass line fully. (Caution: If the bypass dampers is not fully closed then the dust gases can escape to the stack through this route and push up the emission level).
• Continue Coal firing and allow Bag filter inlet temperature to cross 180 Deg C.
• Put the Bag pulsing in demand cleaning mode – Cleaning to start at 175 mmWG and stop at 150 mmWG. This can be readjusted if required.
• Adjust the pulse air pressure to 3.5 Kg/Cm2.
• Adjust Sol. Valve ON time 100 msec , OFF time 25 Sec (to start with)
• Start spent wash firing and increase it gradually in small steps. (Caution: Sudden increase in spent wash firing rate can lead to clinker formation in boiler and chocking of bags in the filter.)
• Start the lime injection system ( Quantity : Lime powder with 50 to 150 microns mesh size @ 150 kg/Hr)
• Restrict the bag filter inlet temp between 180 – 220 Deg C (Max 240 DegC for ½ Hr).
• Record all readings every one hour as given in the log sheet.

Bag filter shut down

Slop fired boiler start up procedure

• After shutdown or tripping the boiler follow following procedures to shutdown bag filter
• Start opening the puppet
  
  
  
  damper fully, after full opening of puppet damper, slowly start opening regulating damper adjusting the furnace pressure & ensure full opening of the damper.
• Close inlet and outlet dampers of the bag filter.
• Keep the pulsing on through timer mode for around ½ hr to dislodge the dust from the bags when the inside temp is high (Caution: Do not pulse the bags when the inside temp is low this may clog the bags.
• Keep the hoper heaters ON.
• Open the inlet and outlet valves of the heating system.
• Start the heating system fan & heater to keep the internal temp to above 140Deg C for ½ hr, till the bag pulsing is over. Keep the dust conveying system ON for at least 1 hr to remove all the dust from the hopper.
• After ½ hour a) Stop the bag pulsing b) Stop the close Circuit heating system. c) Stop the hopper heating system
• Allow the bag filter to cool down in boxed up condition before opening the access doors. Then open the access doors and allow the natural purging before entering inside the filter. 

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