煤基近零排放系统建模分析及系统内煤加氢气化机理研究

发布时间：2018-04-09 09:24

本文选题：近零排放系统　切入点：煤加氢气化　出处：《北京交通大学》2014年博士论文

【摘要】：依靠电力运行的载运工具,动力大多来自燃煤电站,对于以气为动力源的载运工具,若能利用煤制合成气,也能够充分适应我国“富煤、贫油、少气”的能源结构特点。因此,研究开发新型高效洁净煤利用与转化技术对我国而言意义重大。本文以一种煤基近零排放发电系统(ZEC:Zero Emission Coal)为研究对象,首先分析了系统的整体运行特性,然后对系统内的煤加氢气化模块进行了深入分析研究。首先,根据ZEC系统的思想,本文建立了ZEC系统整体模型,并对系统的主要运行单元进行了验证。分析了氢气循环率风,钙碳摩尔比Rctc以及燃料电池的燃料利用率Uf等主要参数对系统能量效率Een、(?)效率Eex、总能量效率Eten和总(?)效率Etex以及CO2捕集效率Rcs的影响,提出所建系统的最优运行参数为Rh=0.75,Rctc=1.5以及Uf=0.8。在该运行参数下,系统的Een为36.2%,Etom为46.8%, Eex为35.7%,Etex为46.2%,Rc,为87.4%。随后,计算分析了系统中各个单元的能量和(?)的平衡关系,对比了系统各单元能量和(?)损失的大小,发现汽轮机中的能量损失最大,而燃料电池中的(?)损失最大,由此指出为了进一步提升系统的运行效率需要降低燃料电池内高品质能量的过大损失。在对ZEC系统整体性能进行了全面研究后,本文着重对其中的煤加氢气化模块从零维热力学平衡模型、零维化学反应动力学模型、三维数值模拟以及试验研究等方面进行了深入探析。首先,考虑到热力学平衡模型良好的通用性以及采用热力学平衡模型对煤加氢气化的研究仍不充分,本文建立了煤加氢气化热力学平衡模型,验证了模型的可靠性,并利用该模型对煤的加氢气化特性进行了预测。若对气化温度进行控制,则当压力pt为7MPa,反应温度T为1000K时,氢煤质量比Rh/c为0.25左右可以使气化产物中甲烷具有较高的摩尔分数。若不控制气化温度,则当pt为7MPa时,Rh/c为约0.5时,煤中的碳才能够完全转化。其次,鉴于煤加氢气化过程的动力学计算模型尚不完善,本文建立了煤加氢气化动力学模型,验证了模型的可靠性,并利用该模型对煤加氢气化特性进行了预测分析。当pt为13MPa,反应时间t为10s,其他运行参数保持和基准运行参数一致时,煤粉整体转化率CCR可达90%,合成气中CH4的摩尔分数MMF可达32%,H2摩尔分数HMF约占60%。当其他运行参数保持和基准运行参数一致时,如果T不超过1273K,则增加T可以从整体上促进煤加氢气化反应的进行。如果T高于1273K,增加T会对煤的加氢气化反应起到抑制作用。由于鲜见国内外对煤的加氢气化炉三维数值模拟结果的报道,本文完善了煤的加氢气化动力学模型,提出了针对气固异相反应的“带有压力修正的联合随机孔隙-未反应碳缩核模型(CRPSC-PC:Combined Random Pore and Shrinking Core Model with Pressure Correction)",在此基础上针对气流床煤加氢气化炉建立了带有化学反应的气固两相流三维数学模型,并借助商业软件Fluent对该模型进行求解,在所用的模拟方法得到验证后,利用该模型对某气化炉的加氢气化特性进行了预测分析。经过综合分析发现,该气化炉的最佳运行工况组合为pt=7MPa,Rh/c,＝0.4,氧氢质量比Ro/h=1.5。在这一运行条件组合下,Rchar为96.78%,MMF为17.42%,冷气效率CGE为76.4%。最后,考虑到煤加氢热解和气化的动力学基础数据尚不完善,本文对一种褐煤、一种烟煤进行了加压热重分析,研究了不同压力下褐煤、烟煤的失重曲线、失重速率曲线,获得了反应动力学特性的典型参数,确定了反映褐煤、烟煤加氢热解和加氢气化的动力学机理函数并计算了不同压力下褐煤、烟煤的动力学参数,分析了不同压力下褐煤及烟煤加氢热解和加氢气化过程的动力学补偿效应。
[Abstract]:In this paper , a coal based near zero emission power generation system ( ZEC : Zero Emission Coal ) is used as the research object , and the overall operating characteristics of the system are analyzed firstly , and then the coal hydrogasification module in the system is deeply analyzed .

Firstly , according to the idea of ZEC system , the whole model of ZEC system is established , and the main operating units of the system are verified . The system energy efficiency Een is analyzed by analyzing the main parameters such as hydrogen circulation rate wind , calcium carbon molar ratio Rctc and fuel utilization rate Uf of fuel cell . The effects of efficiency Eex , total energy efficiency Eten and total ( ? ) efficiency Etex and CO2 capture efficiency Rcs show that the optimal operating parameters of the proposed system are Rh = 0.75 , Rctc = 1.5 and Uf = 0.8 . In this operating parameter , the Een of the system is 46.8 % , Eex is 38.7 % , Etex is 46.2 % , Rc is 87.4 % . Then , the maximum energy loss is found in the steam turbine , and the loss of ( ? ) in the fuel cell is maximum . Therefore , it is pointed out that in order to further improve the operating efficiency of the system , it is necessary to reduce the excessive loss of high - quality energy in the fuel cell .

After a comprehensive study on the overall performance of the ZEC system , this paper focuses on the deep analysis of the coal hydrogasification module from zero - dimensional thermodynamic equilibrium model , zero - dimensional chemical reaction kinetic model , three - dimensional numerical simulation and experimental research .

Secondly , because the dynamic calculation model of coal hydrogasification process is not perfect , this paper establishes a coal hydrogasification kinetic model , verifies the reliability of the model , and utilizes the model to predict the coal hydrogasification characteristics . When the pt is 13MPa , the reaction time t is 10 s , the other operating parameters are kept consistent with the reference operating parameters , the total conversion of the coal is up to 90 % . If T is not more than 1273K , the increase of T can promote the coal hydrogasification reaction from the whole . If T is higher than 1273K , the increase of T will inhibit the hydrogasification reaction of coal .

In this paper , a three - dimensional mathematical model of gas - solid two - phase flow with pressure correction for gas - solid heterogeneous reaction is established , and the simulation method is used to predict the hydro - gasification characteristics of a gasification furnace . After the simulation method is verified , the optimal operating conditions of the gasification furnace are as follows : pt = 7MPa , Rh / c , = 0.4 , mass ratio Ro / h = 1.5 . Under the condition of operation , Rchar is 96.78 % , the MMF is 17.42 % , and the cold air efficiency is 76.4 % . In the end , considering that the dynamic basic data of coal hydropyrolysis and gasification is not perfect , this paper studied a kind of lignite , a kind of bituminous coal , and studied the dynamic mechanism functions of lignite and bituminous coal under different pressures . The kinetic parameters of lignite and bituminous coal were determined and the dynamic compensation effects of lignite and bituminous coal under different pressures were calculated .

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM611

【参考文献】