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Operating Conditions Of Various Parts Of CFB Boiler And Requirements For Refractory Castables
Jan 14, 2019

Circulating fluidized bed boiler is currently the most widely used in China, and it is also one of the most environmentally friendly waste heat boilers. Circulating fluidized bed boilers are mainly used in the power industry, petrochemical industry, and waste incineration industries.


 


Although the application industry is different, the structure of the circulating fluidized bed boiler is roughly the same. In the boiler operation, the high temperature gas and the solid particles in the gas cause severe wear on the refractory lining of various parts such as the furnace and the circulation system. Therefore, the wear and heat insulation requirements of the linings for each part are the key to the operation of the boiler. Taking the power plant boiler as an example, the operating environment of each part of the boiler and the requirements for the refractory castable lining are as follows.


1, the lower part of the furnace


The dense phase zone in the lower part of the furnace is a serious part of the circulating fluidized bed boiler. The bed material is coarse, the concentration is large, the fluidization speed is fast, and the combustion atmosphere has certain corrosiveness. The wear-resistant refractory castable used in this part requires anti-wear and good thermal conductivity, and has good thermal burst resistance and thermal shock resistance. Steel fiber wear resistant refractory castables are recommended.


2. Separator inlet flue


The direction of the gas flow changes in the inlet flue of the separator, and the ash particles in the gas stream are fine and the concentration is high. The gas flow rate is generally 4.5 to 6.0 m/s and the temperature is 850 to 950 °C. The combustion atmosphere is an oxidizing atmosphere, and the wear and wash are severe. The castables are required to have anti-wear properties, thermal burst resistance and thermal shock resistance. Steel fiber wear resistant refractory castables are recommended.


3, cyclone separator


The airflow velocity in the cyclone is high, and the coarse particles in the airflow collide with the wall due to the centrifugal force. Serious wear is caused at the inlet of the separator and the inner wall of the cylinder. The working temperature in the separator is less than 1000 ° C, and the refractory wear layer is thick. The atmosphere is an oxidizing atmosphere. The castable is required to be light, compact, wear-resistant, and has good heat insulation performance (for adiabatic separators), which is resistant to thermal bursting and thermal shock resistance. High-strength wear-resistant refractory castables or wear-resistant refractory plastics are recommended.


4, the return feeder


The returning device circulates the ash which is separated by the separator to the furnace, and the returning device is a fluidized bed on the side of the furnace and a moving bed on the other side, which is a fluidized sealed ash conveying device. The fluidization speed is less than 1 m/s, the bed material is fine, the concentration is high, and the working temperature is about 900 °C. Compared with other parts, the working condition of the returning device is not too bad, but the construction of this part is difficult. No burning occurs in the feeder, and the thermal insulation properties, thermal burst resistance and thermal shock resistance of the castable are required. High-strength wear-resistant refractory castables are recommended.


5, screen heating surface


A screen-type heating surface (water-cooled screen, overheated screen) is arranged in the furnace of the power plant boiler. The lower elbow portion of the screen is worn by the ash particles. The castables are required to have good wear resistance and thermal conductivity. High-strength wear-resistant refractory castables are recommended.


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