Numerical Simulation Of Gas-Solid Flow And Wear Analysis Of1025T/H Circulating Fluidized Bed Boiler

The Circulating Fluidized Bed (CFB) Boiler is widely used in energy chemical industry and other industries because of its excellent fuel adaptability and low emission of SOX and NOX. However, the boiler’s safety and economic operation is threatened by the abrasion of water wall. Wear problem is also the bottleneck of CFB boiler’s development to high parameters and large capacity. In this paper, Fluent software and two-phase fluid model were used to simulate the gas-solid flow characteristics in the furnace of1025t/h CFB boiler of Sichuan Baima Power Plant. The purpose is to get the distribution of granule concentration, velocity and impact angle, which decides the wear rate of water wall. Result shows that the granule concentration is high in the bottom area of the furnace while low in the upper area, which is similar to that of CFB boiler of small capacity. However, the radial distribution of granule concentration and velocity don’t show the typical core-annulus type. In the middle and wall area of the furnace, gas-solid fluid with high granule concentration flows downward at low velocity. High-speed upward flow with low granule concentration exits in the center area of the half furnace. Such distribution pattern looks like a saddle. Another phenomenon is that the value of granule concentration in the corner area is higher than that of other wall area. In addition, the distribution of granule concentration and velocity shows spatial inhomogeneity as well as transitory volatility. The impact angle also shows uneven distribution, especially in the bottom area. But the particles scour the water wall mainly with small impact angle.On the basis of the above simulation results, this study also simulated the flow field in the local area of the furnace, such as the corner area, tube bending area and abrasion-proof beam added area. The wear rate of the waterwall was also calculated. Results show that the wear rate of water wall gradually increases along the direction of particles flow. Compared to the leeward side, windward side of the tube is more easily abraded because of its high value of particle concentration. While abrasion-proof beam is added to the corner model, the velocity and particles concentration value of the granular flow are reduced in its surrounding area. For the above area of the abrasion-proof beam, the best anti-wear effect is obtained in the trapezoid abrasion-proof beam model with the width of100mm. Below the abrasion-proof beam, rectangular abrasion-proof beam with the width of80mm is better than the other two. For the bending tube model, the distribution pattern of particle concentration is seriously affected by the tube’s bend, while particle velocity distribution is not obviously changed. In addition, the partical flow changes its direction in some places. It can be deduced that the tube is easier to be abraded at the lateral of the expanding part of the tube, the contraction mouth of the bending tube and the half surface of the neighbor tube which is closer to the bending tube.