煤制甲醇过程的低温余热利用与碳减排工艺研究

发布时间：2018-01-11 21:42

本文关键词：煤制甲醇过程的低温余热利用与碳减排工艺研究　出处：《华南理工大学》2016年博士论文　论文类型：学位论文

【摘要】：中国是世界最大的甲醇生产和消费国。基于富煤贫油少气的能源现状,国内甲醇生产是以煤气化制甲醇为主。煤制甲醇工艺能耗高,并且碳排放强度大。在煤制甲醇生产过程中,释放大量低品位余热,很多企业未加有效利用。另外,在CO_2回收和捕集情景下,CO_2压缩机组消耗大量电能,最终转化为低温热量排放。将这些余热加以利用,可在推进减排二氧化碳的同时实现节能降耗。本文以煤制甲醇过程的低温余热及碳减排为研究内容,通过热集成、余热发电和过程耦合技术,在流程模拟的基础上,对提出的煤制甲醇过程的低温余热利用工艺和碳减排集成工艺进行了评价分析。以GE水煤浆气化为基础的煤制甲醇工艺包括:水煤浆气化、激冷除尘、水煤气变换、低温甲醇洗、甲醇合成、甲醇精馏等单元。过程模拟软件AspenPlus为工具,建立了60万吨产能的煤制甲醇流程模拟。通过模拟计算,研究了各个单元内的流程配置、工艺参数,为煤制甲醇过程的低温余热利用和碳减排工艺的研究提供了工艺数据基础。煤制甲醇过程是大量反应热及高温物流热量释放的工艺过程。夹点分析表明,气化及灰水处理、水煤气变换、甲醇合成及精馏单元的换热网络都是只需冷公用工程的阈值问题,并且存在着大量的低温余热。甲醇合成及精馏单元的余热量较大,但温度低于70℃,难以利用。气化及灰水处理,水煤气变换的温度在80~150℃低温余热,可以作为煤制甲醇工艺过程的低品位热能,进一步进行余热发电利用。有机朗肯循环发电是应用低沸点有机物做循环工质,将低品位热能转换为电能的余热利用技术。应用R600a为煤制甲醇过程余热发电的有机工质,对余热发电单元进行了夹点分析和换热网络的设计。在最大余热回收量时,有机朗肯发电单元是一个只需冷公用工程的换热单元,总体单元内热源物流产生总热量64.2MW,冷、热物流单元内换热量32.2MW。对60万吨产能的甲醇厂,余热利用的发电功率为3.95MW,净输出电为3.55MW,投资回收期为3年。为降低煤制甲醇工艺外排CO_2,提高CO_2捕集效率,将低温甲醇洗酸气脱除单元的解吸与CO_2压缩进行过程耦合。通过提高CO_2解吸的甲醇富液分离温度、降压闪蒸,可大幅提高CO_2捕集率。将低温甲醇洗流程中甲醇富液升温所提供的低温冷量用于压缩过程的低温冷却,在提升CO_2捕集率的情况下,同时可节省压缩过程电力消耗9.6%,降低冷却水消耗36.1%。从提高单位能量利用效率、提高CO_2捕集率两方面考虑,80~90%为集成碳捕集流程的合理CO_2捕集范围。在碳捕集技术应用于煤制甲醇过程时,CO_2多级压缩也会产生低温余热。带常规碳捕集的煤制甲醇进行有机朗肯余热发电,对外供电约4.32MW,相应每吨甲醇的成本降低39元。在应用低温甲醇洗与CO_2压缩集成工艺时,CO_2捕集率提高到85%;CO_2压缩过程采用四级压缩,余热量与常规碳捕集过程相比略有下降,余热电站对外供电约4MW。余热的发电利用减少了电力的使用,间接减少了煤制甲醇过程的碳排放。
[Abstract]:Chinese is the world's largest methanol production and consumption in the energy situation. Based on the rich coal less gas, the domestic methanol production is dominated by coal gasification methanol. Coal methanol process of high energy consumption, and carbon emission intensity. In the production process of coal methanol, the release of a large number of low grade waste heat, a lot of enterprises is not effective use. In addition, the CO_2 recovery and capture scenarios, CO_2 compressors consume a lot of power, eventually transformed into low temperature heat emission. The heat will be used to achieve energy saving in advance of carbon dioxide emissions at the same time. In this paper, the low temperature waste heat and carbon emission reduction process of coal methanol as the research content, through the heat integrated waste heat power generation and process coupling technology, based on the flow simulation, the low temperature waste heat utilization technology and integrated technology for carbon emission reduction of coal methanol process proposed were evaluated with GE analysis. For coal water slurry gasification Including coal to methanol technology based on the coal water slurry gasification, chilled dust, water gas shift, Rectisol, methanol synthesis, methanol distillation unit. Process simulation software AspenPlus, the establishment of the production capacity of 600 thousand tons of coal methanol process simulation. Through simulation research, each unit within the process configuration and the process parameters, process data provides a foundation for the study of the utilization of low temperature waste heat of coal methanol process and carbon emission reduction process. Coal methanol process is the process a large number of high temperature reaction heat and heat release. The logistics pinch analysis shows that the gasification and ash water treatment, water gas shift, heat exchanger network synthesis and methanol distillation the unit is only threshold of cold utilities, and there are a lot of low-temperature waste heat. The heat quantity of methanol synthesis and distillation unit is large, but the temperature is below 70 DEG C, it is difficult to use gas and ash water treatment, Water gas shift temperature at 80~150 degrees of low temperature waste heat, can be used as low-grade heat coal methanol process, further the use of waste heat power generation. The organic Rankine cycle power generation is using low boiling point organic as refrigerant, the low grade heat energy to heat energy utilization technology. The application of R600a for organic fluid process coal methanol waste heat power generation, cogeneration unit of heat exchanger network pinch analysis and design. The maximum heat recovery amount, organic Rankine power generating unit is a heat exchanger unit only cold utilities, the overall unit heat source logistics total heat 64.2MW, cold heat, logistics unit heat 32.2MW. production capacity of 600 thousand tons of methanol plant, power generation of waste heat utilization for 3.95MW, the net output power is 3.55MW, the payback period is 3 years. In order to reduce the coal methanol efflux of CO_2, improve the CO_2 capture efficiency will be. Desorption and CO_2 low temperature methanol washing acid gas removal unit compression process coupling by increasing the separation temperature, methanol rich liquid CO_2 desorption pressure flash, can greatly improve the capture rate of CO_2. The low temperature methanol washing process of methanol in liquid rich heating cold quantity are provided for the compressed cryogenic cooling process, in ascension CO_2 capture rate, and can save the compression process 9.6% of the electricity consumption, reduce the consumption of cooling water from 36.1%. improve energy efficiency, improve the capture rate of CO_2 in two aspects, the reasonable CO_2 80~90% integrated carboncapture flow capture range. The carbon capture technology in coal methanol process CO_2, multistage compression will produce low temperature waste heat. Coal methanol with conventional carbon capture for organic Rankine heat generation, the power is about 4.32MW, the corresponding cost reduced by 39 yuan per ton of methanol. Washing and CO_2 pressure in the application of low temperature methanol The integrated process of shrinkage, CO_2 capture rate increased to 85%; the CO_2 compression process using four stage compression, residual heat and conventional carbon capture process phase decreased slightly, the external power supply of about 4MW. waste heat power plant waste heat generation by decreasing the use of electricity, indirect coal to methanol process to reduce carbon emissions.

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ223.121

【参考文献】