煤制天然气合成气中CO_2分离方法与特性研究

发布时间：2018-08-26 20:42

【摘要】：在目前的煤制天然气(SNG)工艺中,一般采用低温甲醇洗工艺进行CO2气体的脱除,然而,由于低温甲醇洗往往受到酸性气体中S含量以及装置制冷量的影响,导致脱除效果下降。因此,需要对现有的CO2气体脱除方法特性进行研究,为寻找可替代低温甲醇洗的更有安全、有效的脱除酸性气体的方法提供一定的理论基础和数据支持。本文在实验室的规模下,利用膜分离实验系统、MEA化学吸收实验系统对CO2膜分离法及MEA化学吸收法进行了实验研究,并提出了理论分析方法,在此基础上,本文提出了新型的膜分离——化学吸收联合脱除CO2的方法,在膜分离——MEA化学吸收实验台上对该方法进行了验证。研究结果如下:膜分离系数是衡量高分子膜分离气体性能的一个重要参数,进气的体积流率越大、压力越高以及温度越低,膜分离系数越大,膜渗透端得到的气体CO2浓度越高,Generon210膜的分离系数大于Prism膜,但后者在进气工况变化时分离性能更加稳定,在0.9MPa,25℃,60L/min的进气条件下,Generon210膜渗透端CO2浓度为63.4%,分离效率为63.27%,CH4回收率为93.55%,浓度为95.5%。MEA的流量与温度越高,MEA吸收CO2量越大,MEA溶液浓度超过30%之后,由于溶液粘度增大,吸收量下降,60L/minCO2浓度为15%的混合气体经过30%、55℃、15L/h的MEA溶液吸收后,分离效率可达到99%以上,回收的CH4浓度在99%以上;30%、100℃的MEA富液与6m3/h的蒸汽接触可获得最高的解吸率,为72.52%。根据两性离子机理来准确地描述MEA化学吸收与解吸过程,并由机理推导的动力学模型可计算MEA化学吸收过程中的吸收速率以及解吸过程中任一时刻的解吸率。联合法分离CO2的过程受到进气压力、体积流率、温度以及MEA浓度、流量、温度等多种因素的影响,要达到理想的分离效果,必须调节MEA与CO2的摩尔比达到1.15以上,此时分离效率为81%,回收的CH4浓度为95.5%。联合法有利于大量减少化学吸收所需的MEA量,因此适用于大气量处理工艺中,可作为替代低温甲醇洗的方法。
[Abstract]:In the current (SNG) process of natural gas from coal to natural gas, the low temperature methanol washing process is generally used to remove CO2 gas. However, the low temperature methanol washing process is often affected by the S content in the acid gas and the cooling capacity of the unit, which results in the decrease of the removal effect. Therefore, it is necessary to study the characteristics of existing CO2 gas removal methods in order to provide a theoretical basis and data support for finding a more safe and effective method to remove acid gas from methanol washing at low temperature. In this paper, the CO2 membrane separation method and MEA chemical absorption method are studied by using the membrane separation experiment system under the laboratory scale, and the theoretical analysis method is put forward. In this paper, a new method of membrane separation-chemical absorption combined removal of CO2 has been proposed and verified on the membrane separation-MEA chemical absorption test bench. The results are as follows: the membrane separation coefficient is an important parameter to measure the gas separation performance of polymer membrane. The larger the volumetric flow rate of inlet air, the higher the pressure and the lower the temperature, the larger the membrane separation coefficient is. The higher the gas CO2 concentration at the permeation end of the membrane is, the higher the separation coefficient of the membrane is higher than that of the Prism membrane, but the separation performance of the latter is more stable when the inlet condition changes. The concentration of CO2 at the osmotic end of the membrane is 63.4, the separation efficiency is 63.27g / min, and the recovery rate of CH4 is 93.55. The higher the flow rate and temperature of 95.5%.MEA is, the higher the concentration of CO2 is, and the higher the concentration of CO2 is, the higher the solution viscosity is. After absorption of the mixed gas with the concentration of 60L / min CO _ 2 is 15%, the separation efficiency can reach more than 99%, and the highest desorption rate can be obtained when the concentration of the recovered CH4 is more than 99% and the rich solution of MEA has contact with the vapor of 6m3/h, which is 72.52%. According to the amphoteric ion mechanism, the chemical absorption and desorption process of MEA can be accurately described. The kinetic model derived from the mechanism can be used to calculate the absorption rate in the chemical absorption process of MEA and the desorption rate at any time during the desorption process. The combined separation of CO2 is influenced by inlet pressure, volume flow rate, temperature, concentration of MEA, flow rate, temperature and so on. To achieve the ideal separation effect, the molar ratio of MEA to CO2 must be adjusted to be above 1.15. The separation efficiency was 81 and the recovered CH4 concentration was 95. 5%. The combined method is beneficial to reduce the amount of MEA needed for chemical absorption, so it can be used as a substitute for methanol washing at low temperature.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE665.3

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