1、化工进展Chemical Industry and Engineering Progress2023 年第 42 卷第 3 期CO2捕集工艺中热再生气余热的PVDF/BN-OH平板复合膜回收特性尚玉1，2，肖满1，2，崔秋芳1，2，涂特1，2，晏水平1，2（1 华中农业大学工学院，湖北 武汉 430070；2 农业农村部长江中下游农业装备重点实验室，湖北 武汉 430070）摘要：围绕CO2化学吸收工艺中热再生气的余热回收来开展研究。本文在CO2化学吸收系统的再生塔顶增设换热器，利用分流的冷富CO2吸收剂溶液来回收热再生气（CO2和水蒸气混合气体）中的余热，可降低CO2再生能耗，且余热回收性能
2、越优，降耗效果越明显。采用膜换热器替代传统钢制换热器，利用余热回收过程中冷凝水的热质耦合传递，可强化余热回收性能。本文以聚偏氟乙烯（PVDF）为主体，添加羟基化氮化硼（BN-OH）共混改性，以聚酯纤维（PET）无纺布作为支撑层，制备了 PVDF/BN-OH 平板复合膜，并在乙醇胺（MEA）基富液分流化学吸收工艺中，探讨了复合膜的余热回收性能，同时与商业PVDF平板膜进行了对比。结果显示，与不添加BN-OH的M1膜相比，添加质量分数1%BN-OH的M3膜的平均孔径增加了约11.32%，而孔隙率仅下降了约7.14%，且依然保持亲水特性（水接触角为77.1），同时热导率提高了约52.25%，说明M3
3、膜具有强化热质耦合传递特性的潜能。与M1膜相比，在相同的操作参数条件下，M3膜的余热回收通量和热回收率最大可分别增加95.5%和31.6%。与具有更小厚度的商业化PVDF膜相比，M3膜的余热回收通量和热回收率最大可提高54.8%和9.6%，具有更优的余热回收特性。最后，通过拟合得出余热回收率与各试验因素之间的经验关系式。关键词：二氧化碳捕集；传热；传质；跨膜冷凝器；解吸中图分类号：S216.4 文献标志码：A 文章编号：1000-6613（2023）03-1618-11Recovery characteristics of PVDF/BN-OH flat composite membrane
4、for waste heat of hot stripped gas in CO2 capture processSHANG Yu1，2，XIAO Man1，2，CUI Qiufang1，2，TU Te1，2，YAN Shuiping1，2(1 College of Engineering,Huazhong Agricultural University,Wuhan 430070,Hubei,China;2 Key Laboratory of Agricultural Equipment in Mid-lower Yangtze River,Ministry of Agriculture an
5、d Rural Affairs,Wuhan 430070,Hubei,China)Abstract:In this study,the waste heat recovery was concentrated from the hot stripped gas in CO2 chemical absorption process.A heat exchanger could be added on the top of CO2 stripper in the CO2 chemical absorption system to reduce the CO2 regeneration energy
6、 consumption,which was fulfilled by recovering the waste heat from the stripped gas(i.e.,the mixture of water vapor and CO2)using the bypassed cold CO2-rich solvent in the heat exchanger.Generally,a better waste heat recovery performance leaded to a low CO2 regeneration energy consumption.The waste
7、heat recovery performance could be enhanced by adopting the novel membrane heat exchanger to replace the traditional steel heat 研究开发DOI：10.16085/j.issn.1000-6613.2022-0926收稿日期：2022-05-19；修改稿日期：2022-06-17。基金项目：国家自然科学基金（51676080）。第一作者：尚玉（1997），男，硕士研究生，研究方向为碳捕集过程中的余热回收利用。E-mail：shangyy_。通信作者：晏水平，博士，教授，
8、博士生导师，研究方向为碳捕集、利用和储存等。E-mail：。引用本文：尚玉,肖满,崔秋芳,等.CO2捕集工艺中热再生气余热的PVDF/BN-OH平板复合膜回收特性J.化工进展,2023,42(3):1618-1628.Citation：SHANG Yu,XIAO Man,CUI Qiufang,et al.Recovery characteristics of PVDF/BN-OH flat composite membrane for waste heat of hot stripped gas in CO2 capture processJ.Chemical Industry and En
9、gineering Progress,2023,42(3):1618-1628.16182023年3月尚玉等：CO2捕集工艺中热再生气余热的PVDF/BN-OH平板复合膜回收特性exchanger because of the coupled heat and condensate transfer in the membrane heat exchanger.A PVDF/BN-OH flat composite membrane was prepared through the blend modification method using polyvinylidene fluoride(
10、PVDF)and hydroxylated boron nitride(BN-OH).In this composite membrane,the polyester fiber(PET)non-woven fabrics was used as the support layer.The waste heat recovery performance was experimented by using the prepared composite membrane in the monoethanolamine(MEA)-based rich-split process.Additional
11、ly,the commercial PVDF membrane was also adopted as the control.Compared with the prepared composite membrane without adding BN-OH(i.e.,M1 membrane),the membrane adding 1%BN-OH(i.e.,M3 membrane)achieved a higher average pore size by about 11.32%,a relatively lower porosity by about 7.14%and a higher
12、 conductivity by about 52.25%.Notably,M3 membrane still maintained the hydrophilicity with a water contact angle of 77.1.Therefore,M3 membrane may have the potential to enhance the coupled mass and heat transfer performance.Under the same operation conditions,M3 membrane could obtain a waste heat re
13、covery flux up to 95.5%higher than M1,and a heat recovery ratio up to 31.6%higher than those of M1 membrane.Compared to the commercial PVDF membrane with a smaller thickness,M3 membrane still had a maximum 54.8%higher waste heat recovery flux and 9.6%higher heat recovery ratio,suggesting the better
14、waste heat recovery performance of M3 membrane.Finally,the empirical correlations between the waste heat recovery ratio and key operation parameters were proposed,which showed a high accuracy.Keywords:CO2 capture;heat transfer;mass transfer;transport membrane condenser;desorptionCO2化学吸收技术的关键瓶颈之一在于其高
15、系统能耗，尤其是高富 CO2吸收剂溶液再生能耗。在传统CO2化学吸收工艺中，从CO2再生塔顶排出的再生气中含有大量的水蒸气，且再生气温度一般超过90，携带了大量的潜热。如果能对该余热进行回收利用，将有助于降低再生能耗。基于此，研究人员提出了富液分流工艺，利用在贫富液换热器之前分流的部分冷富液与热再生气进行直接接触，从而回收热再生气的余热1-2。为提高余热回收性能，研究者提出了应用陶瓷膜换热器的改进型富液分流工艺3，如图1所示。其中，陶瓷膜换热器由具有纳米级膜孔的亲水陶瓷膜与不锈钢壳体组建而成。在该改进型富液分流工艺中，分流的冷富液与热再生气在陶瓷膜换热器内进行热交换，同时基于陶瓷膜的亲水特性，
16、再生气侧的冷凝水在气液压差、毛细力等作用下被传质到富液侧，实现热质耦合传递4-7，从而使余热回收性能得到强化。前期研究表明，在采用陶瓷膜换热器时，回收的余热主要以再生气中水蒸气冷凝释放的潜热为主，且主要以导热形式传递，由传质引发的对流换热占比较低8。虽然陶瓷膜换热器具有较优的再生气余热回收性能，但陶瓷膜价格高、脆性大、易损坏，导致投资较大。如若采用廉价的有机膜实现热再生气的余热回收，将能有效降低成本。但有机膜自身的导热性能较差，限制了其在余热回收中的应用。如能对有机膜的导热特性进行强化，势必有助于提高其余热回收性能。在众多有机膜中，聚偏氟乙烯（PVDF）是一种应用十分广泛并且具有耐热和高熔融温度等优点的材料9。在铸膜液中添加导热性较好的纳米颗粒，如碳纳米管、氮化铝和氮化硼等，是一种可以有效提升有机膜导热性能的导热改性方式10。但目前并未有导热增强型的多孔PVDF平板膜在再生气余热回收中应用的相关报道。基于此，本文以 N,N-二甲基甲酰胺（DMF）为溶剂，以聚乙烯吡咯烷酮（PVP）作为致孔剂，将羟基化氮化硼（BN-OH）和PVDF共混，采用非溶剂致相分离法在聚酯纤维（PET）无纺布上制备