The desulfurization efficiency of circulating fluidized bed is affected by a variety of factors, including the particle size and purity of limestone, bed temperature, sulfur content in coal, residence time of limestone in the furnace, combustion temperature in the furnace, calcium-sulfur ratio, type of limestone, fuel volatile content, and the design and operation of circulating fluidized bed boiler. These factors have a significant impact on the desulfurization efficiency of circulating fluidized bed.
In terms of particle size and purity of limestone, if the particle size is too fine, it may lead to insufficient residence time in the thermal cycle circuit, which will increase limestone consumption, while too low purity will affect the reactivity. Therefore, choosing the appropriate limestone particle size distribution can improve the desulfurization efficiency and reaction speed.
Bed temperature also has a great influence on desulfurization efficiency. If the bed temperature is not enough, the limestone will not be able to decompose, which will lead to inefficient desulfurization. Therefore, the bed temperature of the circulating fluidized bed boiler should be kept within the appropriate range to ensure the effective decomposition of limestone and the progress of the desulfurization reaction.
The level of sulfur in coal also affects the desulfurization efficiency. High-sulfur coal requires more limestone to achieve the same desulphurisation effect, so the relative desulphurization efficiency is reduced.
The longer the limestone stays in the furnace, the higher the utilization efficiency and the higher the desulfurization efficiency. This is because the longer the limestone stays in the furnace, the more contact time and reaction opportunities there are with the flue gas, thus increasing the desulphurization efficiency.
The combustion temperature in the furnace has a great influence on the desulfurization efficiency. The combustion temperature of the circulating fluidized bed boiler should be kept within the optimal range to ensure the effective decomposition of limestone and the progress of the desulfurization reaction.
Appropriately increasing the calcium-sulfur ratio can improve the desulfurization efficiency. The calcium-sulfur ratio is the molar ratio of the calcium in the limestone put into the furnace to the sulfur in the flue gas. Increasing the calcium-sulfur ratio means increasing the amount of limestone input, thereby increasing the rate of desulfurization reactions. However, excessively increasing the calcium-sulfur ratio may adversely affect the operation of circulating fluidized bed boilers, such as increasing NOx emissions. Therefore, it is necessary to reasonably control the calcium-sulfur ratio to achieve the best desulfurization effect.
The type of limestone also affects the desulfurization efficiency and reaction rate. Crystalline limestone is composed of large calcium carbonate crystals, which have a dense structure and a small reaction area, so the reactivity is poor. In contrast, amorphous limestone is composed of small pieces of calcium carbonate crystals, which have a large reaction area and good activity. Therefore, choosing the right type of limestone can improve the desulfurization efficiency and reaction speed.
The volatile content of the fuel also affects the desulfurization efficiency. Because the volatiles in the fuel are precipitated and burned much faster than the diffusion of coal particles, an area of high sulfur dioxide and low oxygen concentrations is formed near the coal feed point. This may affect the reaction of the desulfurizer in the region, which in turn affects the desulfurization efficiency. In addition, the lateral mixing ratio of gases and solids in the dilute phase zone of circulating fluidized bed boilers is poor, which may lead to a decrease in desulfurization efficiency.
The design and operation of circulating fluidized bed boilers will also affect the desulfurization efficiency. Different circulating fluidized bed boilers will have different designs and operation methods, which will also affect the desulfurization efficiency. For example, reasonable limestone particle size distribution and temperature control of desulfurization reaction can improve desulfurization efficiency. In addition, the skill level and experience of the operators will also have an impact on the desulfurization efficiency of the circulating fluidized bed boiler.
In summary, the desulfurization efficiency of circulating fluidized bed is affected by many factors. In practice, it is necessary to comprehensively consider these factors and take corresponding measures to improve the desulfurization efficiency of circulating fluidized bed boilers according to the specific situation. If necessary, it is advisable to consult a professional for more comprehensive and accurate information.