Boilers with circulating fluidized bed (CFB)

The long-term successful operation of CBF boilers in real-world boiler house conditions long ago disproved the former widespread opinion that the fluidised bed technology is inappropriate for industrial energy generation due to its complexity and high construction costs. The CBF technology, which retains all the main advantages of the conventional version, does not require any expensive specialised equipment, and is most adapted for application in the majority of domestic boilers at minimum costs. The layer of an adequate height consists of inert material without any fill, thanks to ashes from its own fuel, and works on a mobile ribbed grate, which externally resembles a narrow, obliquely mounted layered combustion chamber. The main process equipment is usually retained when refurbishing existing boilers. The combination of the advantages of CBF and the principle of fuel combustion on a mobile grate (as on a layered one) has an amazing effect, in terms of both boiler operating reliability and fast mastering of the new technology.

Boilers with CBF have the following advantages (compared to standard layered combustion boilers):

•   increased reliability by elimination of unreliable components and mechanisms, operator comfort;

•   expansion of range of fuels used: they can burn virtually any type of coal (calorific capacity of 1500 to 6000 kcal/kg, ash content up to 50%, grain size from 6 to 50 mm);

•   increased gross operating efficiency to 85 - 87% compared to 72 - 80% in standard layered combustion boilers;

•   wider range of load control (from 20 to 100% of the output);

•   applicability of methods that reduce emissions of nitrogen oxides (NOх) from 1500 - 200 mg/m3 of gas (more than 3 times) already inside the combustion chamber;

•   applicability of multi-step interception of small fuel and ash particles and their return to the combustion chamber to burn completely, reducing 5-6 times the concentration of solid pollutants entering the air compared to standard layered combustion.

Basic operating characteristics of boilers (CBF and layered combustion boilers):