cfb boiler water-cooled wall wear analysis of the main causes

        Circulating fluidized bed boilers from the development to date has been a common problem of serious wear of the water-cooled wall heating surface, the boiler if the water-cooled wall wear problems, but also did not take any timely measures or take improper measures, often resulting in frequent boiler bursts and shutdown of the accident. Especially now many power plants use poor quality fuel, circulating fluidized bed boiler wear more serious, to the thermal power plant has brought huge economic losses and adverse social impact.

　　Circulating fluidized bed boiler water-cooled wall wear

　　Water-cooled wall tube wear is like the most easy to wear parts in the fluidized bed boiler, but also the most serious wear the most difficult to deal with parts.

　　Circulating fluidized bed boiler water-cooled wall wear we generally divided into: refractory transition zone wear, water-cooled wall tube corner area wear, water-cooled wall irregular area wear and general water-cooled wall tube wear. Among them, the refractory transition zone wear and water-cooled wall tube corner area wear is the main wear of the water-cooled wall, wear more harmful.

　　Refractory transition zone wear

　　In circulating fluidized bed boiler, the upper thin phase area of the furnace is a fast bed, under certain conditions, the particles in the thin phase area agglomerate, fine particles gathered into large particle clusters, the weight of the particle cluster increases, the free settling speed increases, once greater than the fluidization speed, the particle cluster is not blown up but downward movement against the airflow. In the process of descending, it is broken up into fine particles by the rising airflow, and then driven upward by the airflow, and then gathered into particle clusters, and then settled down. This physical process of particle mass gathering, sinking, blowing, rising and gathering again makes the strong heat and mass exchange occur between the two phases in the circulating fluidized bed.

　　Water-cooled wall wear in the corner area of the furnace chamber

　　Circulating fluidized bed boiler furnace internal circulation of a large number of bed material, extending the residence time of coal particles in the chamber. The inner circulation particle flow is mostly wall particle flow, and its circulation volume is much larger than the outer circulation volume. The material concentration in the near-wall area of the furnace is high, and the distribution of the material concentration in the horizontal direction is low in the middle and high in the near-wall area. In the angle composed of two walls, the flow is superimposed, and the phenomenon of higher concentration in the corners appears, which is the physical basis of serious wear in the corners.

　　Wear of pipe wall in irregular area

　　Irregular pipe walls include through-wall pipes, bends in the furnace wall openings, welds on the pipe walls, fins between the pipe walls, uneven welds and iron parts remaining from the installation in question. Even small geometric irregularities can cause severe localized wear. Part of the furnace chamber with a hole in the door, viewing hole and other round holes is also one of the easy to wear parts. When measuring the furnace temperature, the thermocouple inserted deep enough in the furnace will also have a large impact on the local particles and flow characteristics, resulting in the wear of the nearby water-cooled wall tubes. Around the various holes, due to the downward flow of particles at the wall, and the role of upward airflow, resulting in serious wear of the lower part of the heating surface.

　　General water-cooled wall tube wear

　　From the current operation of the circulating fluidized bed boiler, the general water-cooled wall tube wear, although widespread, stop furnace inspection also found that the wall was worn bright, but the wear rate is small, uniform wear, basically will not endanger the safety of the heating surface.

      Conclusion

　　Although circulating fluidized bed boiler wear has always existed, but with the deepening of research and accumulation of experience on circulating fluidized bed boiler, circulating fluidized bed boiler water-cooled wall wear solutions are becoming more and more efficient. However, the causes of wear of circulating fluidized bed boilers still need to be analyzed according to the actual situation of each boiler, and the most suitable anti-wear solution should be selected to solve the circulating fluidized bed boiler wear problem efficiently.