Experimental Research And Numerical Simulation On Flow, Combustion And Decomposition In Pre-calcined Systems

With the increasing development of construction in China, the output and consumption of cement increase wonderfully for a few years. Until 2005, the output of cement is 10.64 millions tons, which is a half of the total outputs in the world. In the production of clinker, the pre-calcined kilns system is the mainstream of clinkering system, and the pre-calcined system is very important. The characteristics of pre-calcined system, combustion of fuel and decomposition are important to consumption of resources, heat consumption and environmental pollution, which relate to the sustainable development of cement industry. Consequently, research and numerical simulation on flow, combustion and decomposition in pre-calcined systems is one of the important research problems in cement industry.This dissertation was sponsored by Hi-tech Research and Development Program of China (No.2005AA332010.) Some experiment analysis, numerical simulation are investigated on low, combustion, decomposition in pre-calcined systems and their relations. Optimization design of pre-calcined systems with high-efficiency and low environmental load, technology of catalyzed combustion of high ash coal and energy saving of decomposition of raw meal are proposed. The main researches and innovations of the dissertation are as followings:(1) Optimization design method of pre-calcined system is proposed based on computational fluid dynamics. The cold flow field in different pre-calcined systems is investigated by means of FLUENTsoftware. Influences of construction parameters (height of cylinder and middle-neck) and operation conditions on the cold flow field in different pre-calcined systems are also simulated numerically. Compared with the simulated results and the results from the cement plant, the feasibility of optimization design method based on computational fluid dynamics is verified. Moreover, flow models of pre-calcined systems are established according to the simulation results.(2) Evaluation indexes of ignition temperature and ignition/burnout index are used to analyze the combustion characteristics of high ash coal. According to the combustion characteristics of high ash coal, theory and technology of catalyzed combustion of high ash coal are constructed based on new type dry cement process. Influences of alkali metal salts, metal oxides and carbonate salts on the ignition, burnout and heat emission characteristics of high ash coal are investigated using thermogravimetric analysis (TGA). Combustion...