Plant Start‐Up of an Atmospheric Fluidized Bed Boiler Retrofit

Start‐up activities at the Black Dog 130 MWe atmospheric fluidized bed combustor (AFBC) conversion began in February 1986 and ran concurrent with the construction schedule through June 1986. During this period, the boiler casing was air tested, and the water/steam circuitry was chemically cleaned. Forty‐six steam blows were made from drum pressures of 56.2 kg/cm2 (800 psig) to clean the boiler. The first fluidized‐bed coal fires were started on June 26, 1986, with the turbine on line and a maximum electrical power output of 45 MWe net. Gross power output as high as 95 MWe was achieved. Early in the Black Dog Unit 2 project, it was determined that only a bubbling fluidized bed combustor could be economically retrofit to the unit. Despite the limitations imposed by the project requirement to build a retrofit unit and not a completely new fluidized bed combustor (FBC), the Black Dog 2 retrofit provides operating flexibility that would be difficult to obtain with other designs. The paper describes what special design features make the operating flexibility possible and evaluate the economics of the design due to the process efficiency penalty when burning a hard Eastern coal.