Investigation Of Middle-low-rank-coal-based Acetylene Cogeneration System

Based on high efficient utilization of middle-low-rank-coal, the middle-low-rank-coal-based oxy-thermal acetylene manufacturing process is established to replace the petroleum ethylene manufacturing process route. That is the most effective way to relieve the recent petroleum resource shortage.Depending on the National Basic Research Program of China (also called973Program, No.2011CB201306), the middle-low-rank-coal cascaded conversion for low-carbon fuel and chemicals cogeneration system is investigated. For further researching novel energy-saving process of coal-based oxy-thermal carbide acetylene manufacturing, the thermodynamic mechanism of system integration, energy conversion, energy coupling and energy loss of middle-low-rank-coal-based chemicals and power manufacturing system as well as some process route comparison are also discussed. With the detailed investigation of oxy-thermal carbide furnace thermodynamic mechanism, the novel coal-based oxy-thermal acetylene manufacturing process system is proposed. Simultaneously, combining middle-low-rank-coal-based chemicals (acetylene, lime hydrates, off-gas and pyrolysis tar) manufacturing process, fuel cell/steam combined cycle power producing process and coal tar phrolysis ethylene manufacturing process, the novel coal-based cogeneration system is also researched and developed. The most significant is energy conversion mechanism investigation and chemical reaction equilibrium exploration of oxy-thermal carbide furnace. The main contents are as follows:First of all, for high temperature and high energy consumption key unit, i.e. oxy-thermal carbide furnace, the thermodynamic analysis is carried on. The research work includes oxy-thermal carbide reaction process energy configuration establishing with△G-T and α-H-ε diagram analysis for thermodynamic mechanism of energy coupling, energy conversion and high energy consumption reason. The results show that the combustion reaction between partial carbon and oxygen to produce carbon monoxide in the oxy-thermal carbide furnace has great irreversibility and pays most of thermodynamic penalty. For internal reaction process of carbide furnace, by studying the temperature, pressure and feedstock composition affection of chemical reaction equilibrium limit, the yield of CaC2and reaction selectivity change with variation of the operating conditions is investigated. In the meantime, the calcium vapor affection of chemical reaction equilibrium is considered. In addition, by using△G-T diagram, the reaction temperature and reaction order of CaC2is predicted.Second, system evaluation index, which applies to different basis and multiple output of process system, is proposed. Comparing oxy-thermal carbide process with electro-thermal carbide process in the view of energy, environment and economy, the relatively desirable one is selected to establish the middle-low-rank-coal-based oxy-thermal acetylene manufacturing process system and relevant process simulation is then carried on. Simultaneously, with the novel exergy framework Grassman diagram analysis, the energy utilization and exergy loss distribution of process system are investigated. Energy analysis and exergy analysis results of entire system show that the calcium carbide production unit has the maximum exergy loss, which accounts for57.52%of the total internal exergy loss. Then novel middle-low-rank-coal-based oxy-thermal acetylene manufacturing process is compared with traditional middle-low-rank-coal-based gasification ethylene manufacturing process and these two coal-based chemicals manufacturing process routes are evaluated. The results prove that the new process route has the characteristics of energy-saving and emission-reduction.Finally, a large number of byproducts, which produced by the middle-low-rank-coal-based oxy-thermal acetylene manufacturing process system, e.g. carbon monoxide off-gas and pyrolysis tar, is highly reusable. Because of chemical and thermal energy of high-temperature CO off-gas, the molten carbonate fuel cell/steam combined cycle can be used to recycle the off-gas for generating electricity and heat and then the entire system can realize the energy cascade utilization. Besides, pyrolysis tar contains a variety of organic compounds, which have higher chemical energy. Referring to petroleum ethylene manufacturing process, those pyrolysis tars can be reused as the the feedstock of novel ethylene manufacturing process. By fully recycling by-products (i.e. carbon monoxide off-gas and pyrolysis tar) of middle-low-rank-coal-based oxy-thermal acetylene manufacturing process system, the middle-low-rank-coal-based chemicals/power cogeneration process system is finally proposed.