FGD and DeNOx
NEWSLETTER       

                                                                                                                    February  2002
                                                                                                                          No. 286

Dense Phase Reburn 

Bruno Morabito and Robert Hochstetler of Trigen-Cinergy Solutions of Rochester and Allen Wiley of Wiley & Associates dis­cussed the Dense Phase Reburn Combustion System (DPRCS) at Power-Gen 2001. Key elements of the DPRCS  technology include the Centro­Float milling systems, production of a premium micro­fine dry powdered fuel, collection and storage of this fuel, and accurate distribution and dense phase delivery of the fuel in very small (1 ½ inch) lines to dense phase coal torches with a high velocity furnace penetration. The fuel is metered in the range of 500-2000 lb/hr into the individual fuel lines. This premium fuel will also be piped to main burners allowing for stoichiometric fine-tuning at each burner position. In effect the entire furnace, from bottom to top, will be operated as a low NO_x combustor.

The application of DPRCS has the potential of reducing NO_x 25 to 65 percent. It could also allow restoration of lost mill capacity and a potential increase in generating capacity. Lighting off dense phase coal torches in a cold furnace could replace oil as a startup fuel. Turndown could be changed from a typical 3:1 to a potential 15:1. DPRCS also has the potential to allow milling a wide variety of biomass fuel for reburning or direct-fired combustion, lower LOI, and stabilized combustion. Injection of micronized fuel into the main burners has the po­tential to stabilize flames, improve burnout, and fine tune furnace stoichiometry at each burner level.

The milling is done by a CentroFloat milling system. CentroFloat is a high speed, light­weight, self-righting system, which has a fluid suspended rotat­ing body, free floating on a thin cushion of air and rotating about a center of mass rather than a fixed axis. 

The following economic example is based on a 500-MWe wall-fired power plant with LNB & OFA in place and a current level of 0.50 lbs/MMBtu NO_x. This example compares the addition of DPRCS, SCR, or DPRCS and ammonia trim, the resultant NO_x levels, capital and O&M costs associated with each application. The following criteria is the basis used to calculate annual cost per ton of NO_x removed (See Figures 3 and 4).

·         500-MWe plant operating at MCR with 5700 annual operating hours

·         Baseline NO_x 0.50 lbs/MMBtu

·         Discount rate 13 percent

·         DPRCS application

ο 50 percent removal (0.25 lbs/MMBtu)

ο Capital costs $25/kw

ο O&M costs $700,000/yr

·         SCR applications

ο 80 percent removal (0.10 lbs/MMBtu)

ο Capital costs $80/KW

ο Reagent costs $1,000,000/yr

ο Catalyst life 10 yr with amortized replace­ment or regeneration $1,535,000/yr

·         DPRCS with ammonia trim

ο 70 percent removal (0.15 lbs/MMBtu)

ο Capital costs $35/KW

ο Reagent costs $250,000/yr

ο O&M costs $700,000/yr

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