The object of the study is the circulating fluidized bed (CFB) steam generator BKZ 500–13.8 using an off-specification fuel (anthracite screenings of the Listvyanka coal field in the Novosibirsk region). The purpose of the study is to apply the zone method of calculation of the basic elements of the CFB steam generator when switching to a new fuel. The calculations determined the geometric characteristics of the combustion chamber and heating surfaces (zones of the superheater, economizer, and air preheater). The most important indicators of the CFB steam generator operating on anthracite culm were found: boiler efficiency of 92.42%, anthracite consumption of 14.4 kg/s, sulfur oxide emissions of 22.2 kg/s, and nitrogen oxide emissions of 12.8 kg/s. This steam generator can operate on the lowest-grade fuels with minimum environmental damage.