可逆气态膜过程用于浓海水提溴和废水脱氨

发布时间：2018-04-17 03:12

  本文选题：气态膜 + 可逆型吸收剂　； 参考：《天津大学》2016年硕士论文

【摘要】：气态膜分离技术目前虽已得到广泛研究并正在实现工业化应用,但在处理特定料液体系时仍存在膜易被污染,长期操作稳定性差、无法获得理想目标产物、吸收剂消耗大且产品无法回用等问题。聚四氟乙烯(PTFE)具有优异的疏水性能,耐酸、碱和氧化性强,是理想的微孔疏水膜制作材料。本研究针对海水提溴和废水脱氨提出一种吸收剂可再生气态膜过程,分别选用溴化钠和磷酸二氢铵作可逆吸收剂;同为严格避免料液和吸收液泄露造成相互污染,分别采用PTFE中空纤维双套型膜组件和单膜组件作为实验用膜接触器,考察可逆气态膜法浓海水提溴和废水脱氨过程中料液流速、吸收液流速、温度、料液进口浓度和吸收液浓度对膜传质性能的影响及其操作稳定性,运用相应的数学模型对传质过程进行描述,同时验证吸收液蒸馏再生得到高浓溴水和浓氨水的可行性。浓海水提溴实验结果表明:逆流操作条件下,可逆气态膜总传质系数K和提溴率η随温度的升高而增大,25℃时K可达1.10×10-5 m/s,η可达46.18%,多级膜组件串联η可达95%以上;而料液流量和含溴量、吸收液流量和浓度对K影响不大。对吸收完成液进行分析测定发现,与料液溴含量相比溴素在吸收液中被富集了33倍以上。吸收完成液直接蒸馏后塔顶馏出液经溴-水分离可得浓度75%以上的高浓溴水,这几乎避免了酸碱消耗,蒸汽消耗也不到传统提溴工艺过程的1/5,塔底溴化钠溶液可重新用做提溴吸收液。可逆气态膜长期提溴操作实验显示PTFE膜具有良好的传质稳定性和操作稳定性。废水脱氨实验结果表明:25℃时,传统单膜组件总传质系数K可达1.37×10-5 m/s,单程氨氮脱除率η可达97.5%以上,新型双膜组件总传质系数K可达9.6×10-6 m/s,单程氨氮脱除率η可达93.5%以上。虽然双膜组件总传质系数小于单膜组件,但其组件构型有利于保持料液和吸收液之间形成的负温差,从而有效抑制渗透蒸馏现象,在低酸浓度时也可维持较高传质系数,相比单膜组件其膜性能更加稳定。可逆气态膜过程可以把废水氨氮值降至5 mg/L以下,吸收完成液经蒸馏再生可得到浓度5%~18%的氨水和磷酸二氢铵溶液回用,蒸汽耗量不到单纯蒸馏过程的1/3。可逆气态膜长期脱氨操作实验显示PTFE膜传质性能稳定,能够满足此要求。可逆气态膜过程在提取或脱除挥发性组分的同时能够实现挥发性组分和吸收剂的循环利用,本研究为PTFE可逆气态膜法用于海水提溴和废水脱氨工业化应用提供了新思路和技术基础。
[Abstract]:Although the gaseous membrane separation technology has been extensively studied and is being applied in industry at present, the membrane is still liable to be contaminated in the treatment of specific feed liquid system, and the long-term operation stability is poor, and the ideal target product can not be obtained.Absorbent consumption and products can not be reused and other problems.PTFEs are excellent hydrophobic, acid-resistant, alkali-resistant and oxidizing, and are ideal microporous hydrophobic films.In this study, an absorbent renewable gaseous membrane process was proposed for bromine extraction and wastewater deamination, in which sodium bromide and ammonium dihydrogen phosphate were used as reversible absorbers respectively.Using PTFE hollow fiber double nested membrane module and single membrane module as experimental membrane contactors, the flow rate of feed liquid, absorption liquid flow rate and temperature during bromine extraction from concentrated seawater by reversible gaseous membrane process and ammonia removal from wastewater were investigated.The effects of inlet concentration and absorbent concentration on the mass transfer properties of the membrane and its operational stability were studied. The mathematical model was used to describe the mass transfer process and the feasibility of distillation regeneration of the absorbent to produce high concentration bromine water and concentrated ammonia water was verified.The experimental results of bromine extraction in concentrated seawater show that the total mass transfer coefficient K and bromine extraction rate 畏 of reversible gaseous membrane can reach 1.10 脳 10 ~ (-5) m / s and 46.18 m / s at 25 鈩，

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