Boiler in which coal is burnt in an environment of high concentration of bed material (mineral matter) derived from combustion of coal retained by using cyclone / Separators / other means. This bed material is fluidized by primary air (a part of combustion air).
The high concentration of bed material along with staged air supply ensures that bulk combustion temperatures do not exceed 950°C making it environment friendly (lesser production of NOx) means of utilizing coal.
In CFBC boiler, this ash (mineral matter) is separated using a cyclone or similar device and RECYCLED back and hence termed as CIRCULATING FLUIDIZED BED.
In a fluidised-bed combustor, combustion occurs when proven worldwide for allowing a wide range of fuelthe mixture of fuel and fuel ash particles / Bed material is suspended by using a continuous stream of primary combustion air to create turbulence in the bed. The gas cushion between the solids allows the particles to move freely, giving the bed a liquid-like (fluidised) characteristic.
With emission norms getting stringent every day, it is becoming a challenge to install and operate AFBC boilers due to high SOx and NOx emissions. Industry having requirement of smaller range boilers say less than 80 TPH are forced to install costly FGC technologies. This not only impact CAPEX but OPEX also.
CFBC, is a better alternative to AFBC or even Pulverised Combustion (PC).
CFBC boilers are proven worldwide for allowing a wide range of fuel qualities and sizes to be burnt.
Emissions of SOx and NOx are significantly reduced without the addition of expensive flue gas emissions control systems. This is due to the fact that the combustion temperature in a CFBC boiler (800 – 900ºC) is significantly controlled as compared to AFBC and lower than in PC boiler (1300–1700ºC), which results in considerably reduced NOx formation.
Majority of the sulphur in the coal is captured by limestone that is injected into the furnace; about 90% to 95% SO2 reduction can be achieved.
The lower combustion temperature also limits ash fouling and corrosion of heat transfer surfaces allowing the CFBC to handle fuels that are difficult to burn in PC boiler.
Even though the combustion temperature of a CFBC boiler is low, the circulation of hot particles provides efficient heat transfer to the furnace walls and allows a longer residence time for combustion and limestone reaction. This results in good combustion efficiencies
Current designs and capacities offered by most of Indian Suppliers are for larger size requirements. Smaller capacity boilers are not Cost effective due to high royalties and overheads of these companies.
For small sizes specially for Process Steam requirement, no other option than Imported Boilers having reliability and spare parts issues.
In pursuit to provide industry an innovative, viable and cost-effective solution, Mago Thermal offers smaller and medium range CFBC boilers (as small as 35 TPH) with “HEIST”.
These boilers are proper CFBC technology with all the advantages possible.
With nominal incremental price over AFBC boilers, Mago Thermal CFBC boilers are best option for better efficiency and emission norms. Some of features including :