In the olden days blacksmiths used to heat the iron by placing it on a bed of coal. Bellows provide air to the coal from the bottom of the bed. Fluidized Bed combustion is something similar to this. Fluidized Bed At the bottom of the boiler furnace there is a bed of inert material.
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Hot cyclones separate the circulating bed material from the flue gas stream leaving the furnace at around DegC. The solid particles separated from the flue gas are re-circulated back into the furnace through the loop seal. A vortex finder is provided to enhance the separation efficiency of the hot cyclone.
The flue gas containing the fine ash particles exits the cyclones through the vortex finder and outlet flue. The entire hot cyclone, loop seal and outlet flue assembly is provided with a multi layer refractory lining.
The design and arrangement of the hot cyclone is based on specific sizing criteria that are a function of the actual gas velocities entering and leaving the cyclone. Fast to respond to load changes. The CFB, with its low combustion temperature is an especially good solution for coals with low ash fusion temperatures, Preventing the formation of slag. High Combustion Efficiency The continuous circulation of solids through the EnmasGB CFB system keeps the fuel in an ideal combustion environment for a long period of time.
The long residence time results in very efficient fuel combustion, while minimising process changes resulting from sudden changes in fuel quality or mixes. Better sulphur capture with less limestone and improved heat transfer. The ratio between operating gas velocity and minimum solids entrainment velocity allow turndown ratios as high.
Operation over a wide range of boiler loads is possible without starting and stopping burners and auxiliary equipment.
This is due to the combination of low combustion temperature and staged combustion. Elimination of Slagging The low combustion temperature of — DegC in EnmasGB CFB technology eliminates slag formation in the furnace and reduces the volatilisation of alkali salts.
Operating at such low temperatures also means boiler corrosion and convective surface fouling is reduced. Furnace Erosion Potential The maximum velocity of flue gas across various zones is fixed at an optimum level.
Considering low temperature staged combustion associated with the CFBC, the ash particle shape and structure do not reach the level of creating adverse implications in this velocity range. Elimination of hundreds of opening for the arrangement of heating surfaces and in turn the access and inspection openings No horizontal elements need to be arranged in the furnace across the gas flow carrying higher solid density.
Redundancy In the absence of rotating type of equipments, complicated fuel pipes etc. High reliability CFB boilers have demonstrated a high availability due to the simple proven design as offered now.
As a result, we are sure to provide excellent performance results and high reliability. Environmental Aspect We have the ability to provide equipments that consistently meet strict environmental requirements.
This is proved based on the number of operators required for a CFB plant. The reliability is excellent which is why many industrial customers select CFB, for their power plants. The parameters to be monitored in CFB are less.
Our CFBC Boilers are capable of firing nearly all solid fuels - including waste products that otherwise would have been landfilled — while maintaining the lowest levels of emissions, the high equipment reliability and efficiency. Our CFBC Boilers give plant owners the flexibility to source fuel from various suppliers improving their fuel supply security while taking advantages of fuel prices and market conditions. The special advantages of reducing unburnt carbon, coal adaptability, load change capability and reducing pollutants have made CFBC Boiler become rapidly popular. CFBC Boilers adopt fluidized combustion, which is inbetween suspension combustion of PC boiler and fixed combustion of chain Boiler and it also termed as partial suspension combustion. Fluidized type means solid particles are in flow state under the air. CFBC Boiler has bed material material inside Boiler, which is in fluidized state under the pressure of primary air and secondary air to achieve the internal and external circulation of inner and outer furnace, so as to achieve continuous recirculation combustion. Function of cyclone is to achieve solid-gas two phase separation which separates majority solid particles in flue gas; J-seal valve has two function, one is to return the separated solid particles by cyclone back to furnace, so as to achieve continuous recirculation combustion and reactions of Boiler fuel and limestone.
How Circulating Fluidized Bed Boilers Work?