| As a new type of semi-dry flue gas desulfurization(FGD) technology with relatively simple process and low investment, the technology of circulating fluidized bed for flue gas desulfurization(CFB-FGD) is widely used in the process of small and medium-sized boilers, the desulfurization efficiency of which is similar to the wet FGD technology at the same low Ca/S molar ratio. But most of solid particles leave the main reactor so early that their residence time is not enough, when the CFB-FGD process is in running. In order to solve the problems of wet and tacky wall of the conventional CFB-FGD, large quantity of external circulation ash, and low comprehensive utilization rate of lime, this paper presents the good match between the reasonable mass flow of recyclable materials and the certain volume flow of flue gas, and use the exit geometry to enhance internal circulations in CFB risers for improving the efficiency of desulphurization. Gas-solid two-phase flow characteristics were measured in the CFB reactor for FGD process according to three dimensionless groups for practicable similarity of CFBs. The static pressures along with the height of the reactor were measured and the results show that the system pressure loss mainly lies in the Venturi tube section and it increases significantly with the increasing of the circulating solid flow rate and gas flow rate. The non-isokinetic sampling probe was used to measure the local solids mass fluxes at four cross-section of the reactor. The results show there is core-annulus flow in the reactor, with downward solids flow near the reactor walls and upward solids flow in the central area of the reactor. Moreover, the solids mass reflux ratio decreases with the height of the circulating fluidized bed reactor. The results will give important reference to the design and scale-up of the circulating fluidized bed reactor. This paper studies three patterns exit geometry in CFB risers which are flat, inverted V and V pattern. These patterns have their own best high position to enhance internal circulation in CFB risers. However, for the experimental condition of this paper, the best exit geometry is the flat pattern at the height of h / D = 0.326.The workload of design and calculation CFB-FGD systems is large and cumbersome for the ever-changing of the quality of coal, the volume flow of flue gas and so on. Therefore, the use of the professional design software in desulphurization system design has the advantage of improving work efficiency and design conditions, reducing the labor intensity, and promoting the popularization and application of the CFB-FGD technology. This paper introduces the calculation model of CFB-FGD process design software (including parameters of Physical properties, material balance, energy balance and chemical reaction kinetics model), the development platform - Excel 2003 and the software structure. At the same time, it is necessary to analyze the sensitivity of operating parameters and model parameters of the software. It is certified that the software can provide an important prediction for systems design, debugging and controlling. |
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