The circulating fluidized bed boiler is composed of three main parts: combustion chamber, cyclon and the tail of the furnace. + Combustion chamber: The combustion chamber of a circulating fluidized bed reactor (TSTH) has a similar shape to a coal-spray furnace, however, due to the difference in the burning method, there are some big differences in details.
The circulating fluidized bed boiler is composed of three main parts: combustion chamber, cyclon and the tail of the furnace.
+ Combustion chamber: The combustion chamber of a circulating fluidized bed reactor (TSTH) has a similar shape to a coal-spray furnace, however, due to the difference in the burning method, there are some big differences in details.
The burning principle of the biosynthesis furnace is to burn coal in a gravity manner. The hot air after passing through the 1-stage air dryer will be supplied from the bottom of the furnace with enough pressure to maintain the burning of coal particles of 5 mm in size in the combustion chamber volume. The temperature in the fire chamber is from 3 maintained at about 850oC, much lower than the coal blast furnace. The efficiency of the fire chamber is quite high due to the large coal particle retention time, the coal burns more exhausted than the coal blast furnace. Due to the high thermal inertia of the bioslurry furnace, 2000 kcal / kg fuel can be used. »Low calorific value (up to
In addition, the TSTH boiler has a big difference compared to a coal-fired furnace in the combustion process is burned with limestone to reduce SO2 generated in the coal burning process. During the burning process, people add enough limestone and coal to reduce the sulfur released in the coal burning process. Combustion and desulfurization occur at temperatures around 850 ° C. Coal particles burn in a suspended (boiling) state thanks to the pressurized air from bottom to top. Coal particles filled the combustion chamber volume. Its density (concentration) decreases with the height of the combustion chamber.
+ Part Cyclon: Cyclon is a part used to collect unburnt coal particles back to the combustion chamber to form a cycle. The cyclon in the bioslurry furnace is different from the conventional fluidized bed furnace, the exhaust smoke after leaving the fire chamber and the unburnt particles will be dissociated through the Cyclon set and brought back to the combustion chamber into a circulation cycle to burn completely. The hot smoke will continue to pass through the heat exchangers at the rear of the furnace, through the dust filter system and be discharged through the chimney.
* Advantages of CFB furnace:
- The CFB furnace allows burning of non-combustible fuels, fuel composition can vary in a very wide range, high sulfur content in coal while still ensuring environmental standards.
- Coal does not need to be as fine as a coal blast furnace.
- The burning technology is suitable for both bad coal with low calorific value, low volatile content, and the characteristics of anthracite coal.
- Because coal burns at not high temperature (about 850oC), the amount of NO created in the fire chamber is very low compared to traditional coal blast furnace technology. Therefore, with current environmental standards, there is no need to install an expensive NOx reducer on the boiler exhaust line.
- De-SO2 directly in the combustion chamber and the reduction efficiency is very high thanks to the use of limestone as an additive in the combustion process, so there is no need to install an expensive SO2 reducer on the exhaust smoke line of the boiler.
- The temperature in the combustion chamber is low and closely controlled, preventing slag formation and ash bonding.
The furnace has a wide load adjustment range from 50 to 100 ‰ without the use of fuel oil.
- The coal-fired circulating fluidized bed furnace burns harder, so the carbon content in the ash is lower than the coal blast furnace, which is more suitable for industrial users, especially construction materials.
Previously, because the circulating fluidized bed reactor was a new type with limited capacity and the cost was often higher than a coal-fired furnace with equivalent capacity, it was not commonly applied. However, with the current strict environmental requirements and the development of CFB technology, the circulating fluidized bed reactor is increasingly being applied more widely and at a lower cost than the coal blast furnace. NOx and SOx reducers must be installed on the smoke line.