DESIGN IMPACT ON PERFORMANCE OF SLOP / SPENT-WASH FIRED BOILER

HOW TO CHECK DESIGN IMPACT ON PERFORMANCE, (WRONG DESIGN PREDICTION lead to start JUSTIFICATION in BOILER)

CONCERN:

  1. High Economiser Outlet Water temperature
  2. High Flue Gas temperature at ESP Inlet / APH Outlet
  3. High Emission from ESP (White Smoke / Fine dust)
  4. Low Final Steam Temperature @ 100 % MCR load with zero attemperation / spray water
  5. SCAPH Bypass to control ESP Inlet temperature
  6. Low Deaerator Outlet Water Temperature to control Boiler Parameters
  7. High Primary Superheater outlet steam temperature (more than final steam temp.)
  8. STEAM DRUM SATURATION TEMPERATURE at Drum Operating Pressure v/s ECONOMISER OUTLET FEED WATER TEMPERATURE

BASIC DESIGN RULE :- Difference to be kept more than > 20 degC at designed deaerator operating temp. in-between Drum & Economiser water temperature

ACTUAL BOILER LOG :- Slop fired boiler is being operated at very less difference i.e. less than <05 degC only

IMPACT ON BOILER :- Steaming in Economiser, Scaling in Economiser, Disturbed boiler circulation, Pressure Part Failure, Reduce Boiler performance,

SOLUTION / CORRECTIVE ACTION :- Correct the Boiler Design according to Safe temperature difference, Reduce Deaerator Operating temperature from designed temperature

Example of Actual Running Boiler Parameter:

Steam Drum Operating Pressure - 50 Kg/cm2g, Main Steam Pressure - 45 kg/cm2g Steam Drum Saturation water temp - 264 degC, Economiser Outlet Water Temperature - 259 degC

2. ESP PERFORMANCE REDUCTION due to HIGH FLUE GAS TEMPERATURE at APH OUTLET / ESP INLET

BASIC DESIGN RULE :- ESP Design / Operating maximum Inlet temperature for best performance is less than < 180 degC. All ESP are designed in-between 140 degC to 160 degC only for best performance

ACTUAL BOILER LOG :- Slop fired boiler is being operated at very high ESP Inlet Temperature i.e. more than >205 degC & going upto 240 degC

IMPACT ON BOILER :- High Emission, High Gas volume m3/sec at ESP inlet, White smoke with fine dust particles, High ID fan Power Consumption

SOLUTION / CORRECTIVE ACTION :- Correct the Boiler Design to reduce flue gas temperature, Correct the ESP Design / Increase SCA to reduce emission, Reduce SCAPH Operating temperature

Example of Actual Running Boiler Parameter:

APH Air Outlet temp - 195 degC, ESP Inlet gas temp- 215 degC and ESP Collection efficiency will reduced drastically below < 84%.

Disturbed parameters in boiler due to wrong predicted design value in calculation, deteriorate the Boiler Efficiency and increase steam to fuel ratio and running cost of plant along with higher failures and maintenance.

3. LOW APH AIR INLET TEMPERATURE to control HIGH FLUE GAS TEMPERATURE at ESP INLET

BASIC DESIGN RULE :- SCAPH is design to avoid Dew Point Corrosion at APH Inlet

ACTUAL BOILER LOG :- SCAPH bypass / out of service due to Slop fired boiler is being operated at very high ESP Inlet Flue Gas Temperature i.e. more than >205 degC

IMPACT ON BOILER :- High risk of Dew Point corrosion in APH, High ESP inlet Temperature, High Auxiliaries Power Load

SOLUTION / CORRECTIVE ACTION :- Do Not Bypass SCAPH to avoid dew point corrosion, Reduce SCAPH Operating temperature

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