面向建材应用的二氧化碳捕获过程CFD模拟

发布时间：2018-04-27 19:24

本文选题：水泥基建筑材料 + 碳捕集　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：近年来国内外土木工程领域研究表明,二氧化碳气体作为一种新型建筑材料添加剂,可用来改造水泥基建筑材料如混凝土、水泥瓦、水泥再生砖的材料性能。利用二氧化碳作为添加剂,不仅使改造后的建材性能优良,而且能大大减少温室气体的排放。直接从大气中捕获二氧化碳十分困难,实验室生产的二氧化碳只会加重对环境的污染,因此如何高效捕捉排放源中二氧化碳将直接影响这种新型材料在土木工程中的广泛应用。煤炭能源消耗是二氧化碳最大集中排放源,将燃煤烟气中产生的大量废气二氧化碳进行捕集回收,对水泥基材料进行碳化改造,不仅可以提高建筑材料的性能,而且能有效控制大气中二氧化碳的排放、减缓温室效应,可谓一举两得。本文对燃煤烟气中二氧化碳捕集过程进行相应研究,并利用计算流体动力学对碳捕集过程进行模拟分析,为二氧化碳在建筑行业的广泛应用奠定基础。目前可利用的二氧化碳捕获技术主要包括:燃烧前捕获技术、富氧燃烧捕获技术及燃烧后捕获技术。燃烧后脱碳技术当前最可行的方法,工业中常利用化学溶剂吸收法进行燃烧后碳捕集。本文利用计算流体动力学对碳捕集吸收塔装置中氨水吸收二氧化碳过程进行模拟。采用化学溶剂吸收法,以吸收塔内填料层为单元模型,分别模拟了填料单元内气相单相流、气液两相流动过程以及带化学反应的气液两相吸收过程。由气相单相流动可得到与吸收反应相关的压降信息,有助于对填料设备的几何构造进行优化。由气液两相流动可模拟得到液体从液膜到溪流、液滴的流动状态。将模拟结果与相关文献实验结果对比,验证了模型模拟方法的正确性,也为后续研究氨水吸收二氧化碳的气液吸收过程奠定了基础。由组分输运模型、通用有限速率模型和化学反应动力学建立了带化学反应的气液吸收模型,并通过填料表面生成碳酸氢铵浓度计算得到二氧化碳的吸收率。在该模型基础上,考虑气液质量传递过程,编写UDF程序,建立了考虑气液质量传递的化学反应模型,并将两种模型模拟结果进行了分析对比。在此基础上,改变氨水吸收二氧化碳过程的操作条件如:气液体入口流量、二氧化碳入口浓度、氨水入口浓度、压强等,分析了吸收塔填料层内碳捕集过程的影响因素,模拟结果与相关文献实验结果一致。
[Abstract]:In recent years, civil engineering research at home and abroad shows that carbon dioxide gas, as a new additive of building materials, can be used to improve the material properties of cement based building materials such as concrete, cement tiles and cement recycled bricks. Using carbon dioxide as additive can not only improve the performance of modified building materials, but also greatly reduce greenhouse gas emissions. It is very difficult to capture carbon dioxide directly from the atmosphere, and the carbon dioxide produced in the laboratory will only aggravate the pollution to the environment. Therefore, how to capture carbon dioxide from the emission sources efficiently will directly affect the wide application of this new material in civil engineering. Coal energy consumption is the largest concentrated emission source of carbon dioxide. It can not only improve the performance of building materials, but also capture and recover a large number of waste gas carbon dioxide from coal-fired flue gas and carbonize cement based materials. And can effectively control atmospheric carbon dioxide emissions, slow down Greenhouse Effect, can kill two birds with one stone. In this paper, the process of carbon dioxide capture in coal-fired flue gas is studied, and the process of carbon capture is simulated and analyzed by using computational fluid dynamics, which lays a foundation for the wide application of carbon dioxide in the construction industry. Currently available carbon dioxide capture technologies mainly include pre-combustion capture technology, oxygen-enriched combustion capture technology and post-combustion capture technology. The chemical solvent absorption method is often used to capture carbon after combustion in industry, which is the most feasible method of post-combustion decarbonization. In this paper, the process of ammonia absorbing carbon dioxide in carbon capture and absorption tower is simulated by computational fluid dynamics (CFD). The single-phase gas flow, gas-liquid two-phase flow process and gas-liquid two-phase absorption process with chemical reaction were simulated by using the chemical solvent absorption method and the packed layer in the absorber as the unit model. The pressure drop information related to the absorption reaction can be obtained from the gas phase single-phase flow, which is helpful to optimize the geometric structure of packing equipment. The flow state of liquid from liquid film to stream can be simulated by gas-liquid two-phase flow. By comparing the simulation results with the experimental results of related literatures, the correctness of the model simulation method is verified, and the basis for further study on the gas-liquid absorption process of carbon dioxide absorption by ammonia water is established. The gas-liquid absorption model with chemical reaction was established by component transport model, general finite rate model and chemical reaction kinetics. The absorption rate of carbon dioxide was calculated by the concentration of ammonium bicarbonate on the surface of filler. On the basis of this model, considering the process of gas-liquid mass transfer, the UDF program is written, and the chemical reaction model considering the gas-liquid mass transfer is established, and the simulation results of the two models are analyzed and compared. On this basis, changing the operating conditions of the process of ammonia absorption of carbon dioxide, such as: the inlet flow rate of gas and liquid, the inlet concentration of carbon dioxide, the inlet concentration of ammonia water, the pressure, etc., the influencing factors of carbon capture process in the packed layer of absorption tower are analyzed. The simulation results are consistent with the experimental results.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

【参考文献】