基于中空纤维膜技术的二氧化碳吸收和解吸研究

发布时间：2018-07-10 15:29

  本文选题：二氧化碳 + 中空纤维膜　； 参考：《浙江大学》2014年博士论文

【摘要】：基于液态吸收剂的燃烧后碳捕集技术是目前短时间控制燃煤电站CO2排放最为有效的方法。在其中,基于中空纤维膜技术的CO2吸收和解吸工艺由于具有较高的吸收传质通量和低CO2再生能耗,被认为是具有前景的技术。但是对于CO2膜吸收和膜解吸来说,如何选择合适的吸收剂和提高运行的稳定性是当前亟待解决的问题。本文从吸收剂的角度出发,分别对膜吸收／解吸过程的吸收剂的开发、过程的模拟优化和膜的运行稳定性等问题进行系统深入的探讨。 在单一吸收剂方面,首先对有机胺吸收剂化学结构与CO2膜吸收／解吸的关系进行了系统研究。具体通过吸收剂结构中氨基数目、氨基上活性H原子数目、碳链长度、官能团位置和大小等对CO2吸收／解吸特性的影响进行分析。该分子结构与性能的关系研究可为未来胺类吸收剂的选择和结构预测提供经验指导。此外,建立了吸收剂综合评价体系,研究发现：TEPA和EDA为CO2膜吸收推荐的最优吸收剂；MDEA是CO2膜解吸中最为推荐的吸收剂,其次为TETA、DEA和EDA。此外,提出高温CO2膜吸收概念,对24种氨基酸盐吸收剂进行一系列的遴选实验,以寻找最适合高温CO2膜吸收的CO2吸收剂。在高温CO2膜吸收实验中,研究发现肌氨酸钾吸收剂表现最优的CO2吸收性能。 在混合吸收剂方面,建立二元混合胺吸收剂的理论传质模型,并对混合胺吸收剂的配比准则和机制进行研究。该理论的传质模型预测的总传质系数与实验值具有较高的吻合度。研究发现,推荐的最优的混合吸收剂组成为：对MEA/MDEA,MEA主体浓度为30wt%,MDEA的比例在0.1-0.3之间；对DEA/AMP, DEA主体的浓度为15wt%,AMP的比例在0.5-0.8之间；对MDEA/PZ, MDEA的主体浓度为20wt%,PZ的比例在0.3左右。 以CO2反应动力学、MEA-H2O-CO2气液平衡(VLE)模型和流体传质理论为基础,建立了MEA吸收剂富液的CO2膜解吸的二维数学模型。该模型模拟结果与文献报道的实验结果吻合度良好。基于该模型,对膜解吸过程中关键操作因素例如温度、压力、液相流速和吹扫蒸汽,以及膜接触器的参数影响进行了敏感度分析。最后对CO2膜解吸运行条件进行了优化,最优的运行压力在20kPa左右。 在膜的稳定性方面,选择MEA、THAM和KS三种吸收剂,在60℃下分别研究其对PP膜的湿润机理以及长期膜吸收运行中膜阻力的变化。研究发现跨膜压差对总传质系数有着非常大的影响,跨膜压差越大,将会导致更高的膜湿润程度。在研究的3种吸收剂当中,KS吸收剂由于具有高表面张力,因此相对其它吸收剂,其对膜的湿润程度要更弱。 最后对CO2膜解吸的运行能耗进行分析和优化评估。对MEA吸收剂来说最优的再生能耗运行工况为再生压力20kPa左右。在此运行压力下MEA吸收剂具有的最低CO2膜解吸再生能耗,与传统热再生进行比较,可以发现相对于热再生可以降低能耗28%。在研究的所有单一有机胺吸收剂当中,MDEA具有最低的C02膜解吸再生能耗,其次为EDA和DEA。此外发现,如果在C02膜解吸中能够避免采用吹扫蒸汽或电厂具有丰富的低品位废热提供C02膜解吸的所需的热耗,再生能耗的优势将会更加明显,存在更好的工业应用前景。
[Abstract]:The CO2 absorption and desorption process based on liquid absorbent is the most effective way to control the CO2 emission of coal - fired power plant in a short time . In this paper , the CO2 absorption and desorption process based on hollow fiber membrane technology is considered to be a promising technology . However , it is urgent to solve the problem of how to select suitable absorbent and improve the stability of operation because of the higher absorption and mass transfer flux and low CO2 regeneration energy consumption .

In the aspect of single absorbent , the relationship between the chemical structure of the organic amine absorbent and the absorption / desorption of CO2 is studied . The influence of the number of amino groups , the number of active H atoms on the amino group , the length of the carbon chain , the position and the size of the functional groups on the absorption / desorption characteristics of the CO2 is analyzed . The relationship between the molecular structure and the performance can provide empirical guidance for the selection and the structure prediction of the future amine absorbent . In addition , the comprehensive evaluation system of the absorbent is established , and it has been found that TEPA and EDA are the best absorbent recommended for the absorption of CO2 films ;
MDEA is the most recommended absorbent in CO2 film desorption , followed by TETA , DEA and EDA . In addition , the concept of high temperature CO2 film absorption is proposed . A series of selection experiments are carried out on 24 amino acid salt absorbent to find the best CO2 absorbent suitable for high temperature CO2 absorption .

In this paper , the theoretical mass transfer model of binary mixed amine absorber is established in the aspect of mixing absorbent , and the proportioning criterion and mechanism of mixed amine absorber are studied . The mass transfer coefficient predicted by mass transfer model has a higher agreement with the experimental value . It is found that the optimum composition of mixed absorbent is : the concentration of MEA / MDEA and MEA main body is 30 wt % , and the ratio of MDEA is 0.1 - 0.3 ;
the concentration of DEA / AMP and DEA main body is 15 wt % , and the ratio of AMP is between 0.5 and 0.8 ;
The main concentration of MDEA / Pz and MDEA is 20 wt % , and the ratio of pz is about 0.3 .

A two - dimensional mathematical model for desorption of CO2 film from MEA absorber rich liquid is established based on CO2 reaction kinetics , MEA - H2O - CO2 gas - liquid equilibrium ( VLE ) model and fluid mass transfer theory . The model simulation results are in good agreement with the experimental results reported in the literature . Based on this model , the sensitivity analysis of key operating factors , such as temperature , pressure , liquid phase flow rate and purge steam , and parameters of membrane contactor , are carried out on the basis of this model . Finally , the conditions for desorption operation of CO2 membrane are optimized , and the optimum operating pressure is about 20 kPa .

In the aspect of film stability , three absorbents of MEA , THAM and KS were selected , the wetting mechanism of PP film and the change of membrane resistance during long - term film absorption were studied at 60 鈩，

本文编号：2113807