SCR + Ammonia=NOx; ESP= Particulate; FGD+ Limestone= SO2 ; Trona=SO3 ; Activated Carbon= Hg
Clean Power Plan = CO2 Emission Reduction??
Coal Beneficiation + Hybrid of Coal-Gasification
(SO2 & NOx Control Right in the Combustion Step)
The Clean Combustion SystemTM (CCS) is an entrained-flow coal gasifier followed by stages of over-fire air combustion in the boiler furnace section.
This schematic shows the CCS Burner and water-cooled refractory lined Gasifier Section mounted on the boiler's furnace wall.
Pulverized coal, with limestone added as source of calcium for sulfur capture, is fired in the gasifier with limited air.
The coal-sulfur reacts with calcium to form calcium sulfide (CaS), a solid particle. Any NOx from fuel-bound nitrogen is reduced to only N2 under these conditions (near-zero NOx).
The high gasification temperatures melt the coal ash (silica and alumina) along with the CaS, to encapsulate the sulfur in the ash. The inert bottom ash (liquid slag) drains from the gasifier to a water quench tank for disposal.
The clean, hot Fuel-Rich gases then enter the boiler furnace where staged "over-fire" air (OFA) is added to complete the combustion of CO to CO2 and H2 to water.
Attention to the OFA addition helps prevent formation of any new (thermal) NOx.
The gases then exit the boiler furnace and enter the boiler superheat section as was before the retrofit. A bag house is required to collect any fly ash particulates.
Limestone is the only "chemical". There are no hazardous chemicals or waste water. No flue gas desulfurization (FGD) scrubber or selective catalytic reduction (SCR) systems are required.
A CCS Re-Engineering retrofit of a boiler furnace is shown in the above Schematic:
- Improves combustion efficiency - reduced CO2 emissions
- Pollution Emissions compliance for SO2 & NOx
- Provides an extended competitive dispatch with increased plant capacity factor.
The "CCS Coal Beneficiation Module" may include steps to improve the coal-fuels quality before firing: to extract water, ash, and mercury from the pulverized coal. Further coal processing to extract the oil values from the coal may provide a new source of income for the electric generating plant. This income will significantly reduce the plants operating cost; to improve capacity factor and provide opportunities for increased dispatch.
Expected CCS Emissions* Performance when firing Powder River Basin Coals:
- SO2 = < 0.4 lb./mmBtu (< 210 ppm) ~80% reduction
- NOx = < 0.15 lb./mmBtu (< 110 ppm)
- CO = < 200 ppm
- LOI = < 1% (very low carbon in ash)
- SO3 = < 0.3 ppm (condensable)
- Mercury = < 50 ppb
- Particulate = < 0.08 lb./mmBtu (bag house)
- Boiler Efficiency = 2 - 10% increase
* Preliminary estimates of performance, includes bag house - no guarantees
- From Fundamental Combustion Theory to Commercial Operation
- Allow power plant upgrade with waiver of NSPS & PSD - No NSR
- Low Retrofit Cost; maintain older, smaller power boilers competitive
- Improve Plant Capacity Factor & Dispatch
- Fits within Plant & Boiler Site Footprint
- All equipment off-the-shelf & familiar to the Operators
- Safe, stable operation
- Same startup, shutdown and turndown as a PC burner
- Bottom Ash (slag) removed before furnace
- Low particulate/ash load; clean furnace, less soot blowing
- Sulfur removed from furnace gases - near-zero SO3
- Allows for lower furnace exit temperatures
- Minimize water-wall wastage & corrosion
- Can use hot boiler exhaust for pulverizer sweep air
- Dry the coal - reject moisture
- Improves coal pulverizer safety from fire & puffs (low O2)
- Improved Boiler Efficiency (2 to +10%)
- Reduce CO2 emissions
- High combustion efficiency (LOI < 1%)
- Limestone is only "chemical" required
- No waste water discharge
- Ash products have value (sell bottom ash & fly ash)
- No Hazardous or Toxic Chemicals Required
CCS is an ADVANCED COAL GASIFICATION TECHNOLOGY!