| Entrained-flow gasification technology is one of the core technologies of modem coal chemical industry.The dry pulverized coal gasification technology has been widely used in our country due to its excellent flexibility to coals,long operation period,low cost,and superior technical indicators.Therefore,the optimization of the main operating parameters of the dry pulverized coal gasification unit,the study of the heat transfer of its key components,the gasification nozzle and the water wall,are of great significant to the design of the gasifier and long-term stable operation.Taking a 2000 t/d dry pulverized coal gasifier used by a coal chemical enterprise in Ningdong as the research object,a three-dimensional model of an industrial-scale gasifier was established to simulate the gasification process.The two-step competitive reaction model is used to simulate the pulverized coal devolatilization process,the eddy dissipation conceptual model(EDC)is used to simulate the homogeneous turbulent chemical reaction,the reaction condensation model is used to simulate the heterogeneous coke gasification reaction process,and the P1 model is used to simulate heat radiation.Based on the orthogonal experiment of three factors and three levels,the main process parameters were optimized by simulation such as the gasifier operating pressure,the mass ratio of coal/oxygen and the mass ratio of water vapor/oxygen.Some results were showed as follows.The mass ratio of coal/oxygen is the primary factor of affecting the content of syngas at the outlet of the gasifier.The secondary factor is the mass ratio of water vapor/oxygen.The operating pressure has the least effect.The optimal process conditions are as follows:operating pressure 4.4 MPa,m(C)/m(O)=1.4,m(H2O)/m(O2)=0.1/0.9.It is verified that the content of synthesis gas at outlet can reach 93.22%under the optimal process conditions.And the outlet temperature is 1400?,which meets the operating need.The gasification nozzle has an important influence on the flow field distribution and gasification efficiency in the entrained bed gasifier.In this paper,a detailed gasification nozzle structure model is established,and the key structure parameters of the nozzle are simulated and analyzed for the flow field in the gasification furnace.According to the installation angle a of the swirling blades in the gasification agent channel and the rotation angle ? of the pulverized coal channel,the influence of different a and ?values on the gasification process was investigated.The results are as follows:when ?=30°,?=60°,the temperature field in the gasification chamber is the best.The high-temperature area is reasonably located,and the main body temperature and wall temperature are in line with actual production conditions,and the total content of CO and H2 reaches 91.02%.The gasifier model with detailed nozzle structure is more detailed and more reasonable for investigating the flow field distribution of the gasification process than the simplified symmetrical model.It is an important basis for the optimization design of the equipment.In addition,a simulation study on the heat transfer of the local structure of the water wall of the gasifier was carried out.The result shows the surface temperature of the slag layer in the gasification chamber has a great influence on the temperature of the water wall.The slag nails can effectively improve the heat transfer efficiency and remove the excess heat in the gasifier in time.And the slag nails with small angles and triangular arrangement have better heat transfer efficiency and the temperature distribution is more uniform. |
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