Powder - Particles Spouted Bed Semi-dry Flue Gas Desulfurization Multi-phase Transmission, The Response Characteristics Of The Numerical Simulation Of The Multi-scale Effect

The environmental problems have become popular nowadays. With increasing concern on this issue, controls on the emission of various pollutants are increasingly stringent. Coal is the main energy source of china, so it is a major issue to reduce the environmental pollution caused by sulfur component in coal. Powder-particle spouted bed semi-dry flue gas desulfurization technology, which developed in Japan, has many advantages, such as high desulfurization rate, high sorbent utilization, low cost and so on, and has become a very promising new flue gas desulfurization technology.Powder-particle spouted bed semi-dry flue gas desulfurization system is regarded as a complex multi-phase system, including gas, liquid, particles and powder. In addition, complicate physical and chemical changes such as evaporation, dissolution, sulfur absorption, particle broken and air entrainment will occurring during this process. Researches on the multi-phase transfer, reaction characteristics and particle flow structure in the powder-particle spouted bed, which will help for optimal design of spouted bed reactor and development of multi-scale theory, are useful and necessary.In this paper, computational fluid dynamics (CFD) method has been used to simulate the powder-particle spouted bed semi-dry flue gas desulfurization system. A mathematical model describing water evaporation and desulfurization has been established, through reasonable simplifying assumptions. The results show that the annulus region of spouted bed is the main areas where the water evaporation and desulfurization occur, because it has more heat transfer area, longer residence time of materials, and high gas flow rate. Moreover, obvious laminar flow of particle has been simulated in the spouted bed, and there is no efficient mixing between inner and outer particles, so that the particle surfaces cannot be fully used, which result in unsatisfactory mass and heat transfer. The results also show that there is a cumulative process of desulfurization agent in the reactor, and only under a certain concentration of desulfurization, a perfect desulfurization can be received.In addition, the energy-minimization multi-scale (EMMS) theory has been introduced to study the influence of particle agglomeration on gas-solid phase interactions and particle flow structure. A drag coefficient model has been formulated by solving EMMS equations, using experimental data, and implemented into the commercial CFD code. The simulation results show that satisfactory agreement between the prediction and measurements has been obtained. Based on the experimental data, a simplified model method for solving EMMS equations is reasonable and reliable, and significantly reduces the huge amount of calculation of nonlinear equations.