Full-Scale Demonstration Low-NOx Cell Burner retrofit

This project was undertaken to evaluate the technical and economic feasibility of retrofitting LNCB technology for cell burner boiler NO x emission control in electric power generation service. Most cell burner boilers use two-nozzle cell burners which fire pulverized coal under very high temperature combustion conditions. Because of the high temperature of combustion in cell boilers, high levels of NO x are formed. The LNCB retrofit technology replaces each two-cell burner (and some three-cell burner units) with one larger diameter burner nozzle to provide the same coal-firing capacity as the original two (or three) nozzles. This enlarged burner is fired under highly fuel-rich conditions, and the second-stage combustion air is introduced through the second nozzle of the original cell. The net result is a decrease in combustion temperatures under deeply staged conditions and a reduction in both fuel NO x and thermal NO x. The performance objectives of this project were as follows: 1. To evaluate the ability of LNCB technology to reduce NO x emissions at least 50% in full-scale boilers equipped with cell burners. 2. To achieve the NO x reduction goal with no degradation of boiler performance or life of the unit. 3. To demonstrate that LNCB is an economically viable retrofit technology. All three goals were met or exceeded in the demonstration project, which was conducted at DP&L's J.M. Stuart Station, Unit 4 (rated at 605 MWe). This boiler is fired with Midwestern bituminous coal with an average sulfur content of about 1%. Greater than 50% reduction of NO x emissions was achieved at full and intermediate boiler loads, and nearly 50% at low boiler load. Waterwall corrosion was within normal limits for standard cell boilers. Application of B&W's mathematical models led to the design of a modified LNCB firing configuration which mitigated excessive concentrations of CO and H 2 S in the boiler hopper. No problems were experienced in boiler operation or other emissions under optimized conditions. DP&L accepted the LNCB firing system and continued to run it on a routine basis. B&W has retrofitted LNCB technology to nearly 5,500 MWe of generating capacity in the United States. A 1994 estimate using a nominal 600-MWe unit gave an estimated capital cost for an LNCB retrofit of $9/kW. Assuming uncontrolled NO x emissions of 1.20 lb/10 6 Btu, 50% NO x reduction, and a 15-year project life, the levelized cost on a current dollar basis is …