Applications Research Of Lattice Boltzmann Method On Gas Solid Flow

Energy is the basis of human living and development. Our country is in a critical period of rapid economic growth currently, leading to great energy consumption. It is quite serious that non-renewable resources are faced with exhaustion, such as coal, oil, natural gas and so on. Industrial waste heat resources are very abundant in our country with only 34.9% recycled resources, so the potential for recycling is huge. Rational utilization of waste heat resources can speed up achieving the strategic goals of industrial energy conservation and emissions reduction.A large number of flue gas at medium and low temperature can be produced in cement production process, which can be recycled by waste heat boiler to generate electricity. However, there are a lot of fly ashes in the flue gas. These ash particles will deposit on boiler heating surface, leading to lower boiler thermal efficiency, reduce boiler capacity, and the energy-saving targets more than expected. So ash deposition problem should be highly valued, which is one of the key problems related whether the waste heat recovery technology can be successful. Ash deposition is one of the typical gas-solid flows. It has very important application and economic value to study dust particles in the flue gas depositing on the tube.The lattice Boltzmann-Lagrange tracking method was used to simulate deposition process of ash-laden gas across tube in this paper, and the effect of tube shape and tube bundle arrangement on particle deposition were explored. The main research contents and results are as followed:1. Two-dimensional porous medium seepage problem was simulated preliminarily using lattice Boltzmann method. The porous medium were constructed by QSGS growth method, and their pore boundary was quite complicated. Results show that lattice Boltzmann method has strong ability to solve problems containing complex boundary.2. Deposition process of ash-laden gas across circular tube and elliptical tube was simulated using multi-relaxation-time lattice Boltzmann-Lagrange tracking method. Results show that distribution of particles with small Stokes number in the flow field is more uniform. With the increasing of Stokes number, particles distribution in the flow field is near the border area of the vortex structure gradually, and the total deposition amount on the circular tube is gradually reduced. When the long axis of the elliptical tube is parallel with the flow direction, the deposition rate and collision frequency per unit area on the elliptical tube are both smaller than those on the circular tube. With the increase of axle ratio, the deposition rate and collision frequency per unit area are reduced gradually.3. For the in-line circular tube bundle with three kinds of combination of horizontal and vertical tube spacing, the same law of particle deposition as a whole is found. A small amount of particles deposit on the windward side of the first row tube bundles, while much more particles deposit on the leeward side. Many particles deposit on the both windward side and leeward side of other row tube bundles. For the fork row circular tube bundle with three kinds of combination of horizontal and vertical tube spacing, the same law of particle deposition as a whole is also found. A small amount of particles deposit on the windward side of each row tube bundles, while much more particles deposit on the leeward side. The number of particles deposition on the second row tube bundles is minimum. When it is fork row layout, the deposition rate is smaller. When the horizontal and vertical tube spacing are equal, the deposition rate is also smaller.