Tham khảo tài liệu 'air pollution control systems for boiler and control problems_9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Sim poiPDF Mergeíand Split Unregistered Version - http MIN FLUID ENTRAINMENT PARTICLE - LOG VELOCITY PRESSURE DROP vs GAS VELOCITY Courtesy of Pyropower Corporation Figure 13 2. Pressure drop vs. gas velocity particles leave the combustion chamber with the flue gases so that solids recirculation is necessary to maintain the. bed solids. This type of fluidization is called circulating fluidized bed. e. The mean solids velocity increases at a slower rate than does the gas velocity as illustrated in figure 13-3. Therefore a maximum slip velocity between the solids and the gas can be achieved resulting in good heat transfer and contact time with the limestone for sulfur dioxide removal. When gas velocity is further increased the mean slip velocity decreases again. These are the operating conditions for transport reactor or pulverized coal boiler. The design of the fluidized bed falls between the stoker fired boiler and the pulverized coal boiler using the bed expansion. f The shallow fluidized bed boiler operates with a single bed at a low gas velocity. A shallow bed minimizes fan horsepower and limits the free-board space. The bed depth is usually about 6 inches to 9 inches and the free-board heights are only four to five feet. Desulfurization efficiency of a shallow bed is poor with only about 60 to 80 percent removal because SO2 does not have adequate time to react with the limestone before moving out of the shallow bed. The shallow bed fluidized boiler is of the bubbling bed design. The shallow bed will be of very limited use because of its poor sulfur dioxide removal. g. A deep fluidized bed boiler is a bubbling bed design. 1 The bed depth is usually 3 feet to 5 feet deep and the pressure drop averages about one inch of water per inch of bed depth. The bulk of the bed consists of limestone sand ash or other material and a small amount of fuel. The rate at which air is blown through the bed determines the amount of fuel that can be reacted. There .
