摘要
针对目前反渗透(reverse osmosis,RO)浓水的零排放以及膜蒸馏产生的蒸汽冷凝及相变热回收问题,该文设计了一套适用于寒冷地区的太阳能减压膜蒸馏RO浓水淡化系统。系统主要由太阳能集热器、膜蒸馏组件、冷凝装置及真空泵等部分组成。该系统在宁夏银川市贺兰县的苦咸水地区进行了试验,对太阳能的集热效果、减压膜蒸馏的RO浓水淡化效果、冷凝装置的冷凝效果及对温室作物的加热效果进行了测试分析。试验表明:所选的太阳能集热器面积基本可以满足全年的膜蒸馏用热,在反渗透淡水池中设计的不锈钢散热盘管长度可以满足蒸汽冷凝要求,在地表以下30~40cm处铺设地热盘管可以满足蒸汽冷凝要求和温室加热需求。在浓水进水温度为80℃、渗透侧真空压力为-0.080MPa时,减压膜蒸馏系统产水量可以达到37.62L/h,但随着膜蒸馏系统运行时间的加长,膜污染加重,产水量逐渐降低,在系统运行了近240h以后,对膜组件进行清洗,清洗后的系统产水量比清洗前提高了近1.5倍。通过试验验证,该系统基本能够满足寒冷地区温室的使用要求。该研究对降低膜蒸馏系统能耗、解决膜蒸馏的蒸汽冷凝及相变热回收、实现RO浓水零排放、减少浓水对环境污染具有重要意义。
In order to solve the problems of zero discharge of reverse osmosis(RO)brine,the coupling matching of solar collector and membrane distillation,the cooling water reduction and phase change heat recovery in the steam condensation process of membrane distillation system,the RO brine desalination system by solar vacuum membrane distillation in cold area was designed and verified in the test.The system consists of RO concentrated tank,membrane distillation module,solar collector,condensing unit,circulation pump,vacuum pump,fresh water tank,and so on.The condensing devices are self-made stainless steel heat exchange coil placed in the RO freshwater pool and geothermal coil placed in the underground of the greenhouse.The components of the system are designed in detail,and the self-made condensing device is the focus in the design.The system is placed in a greenhouse in Xinrong Village,Helan County,Yinchuan City,Ningxia.The front end of the system is an RO system for greenhouse irrigation.Since RO concentrated water cannot be discharged,it is further diluted by vacuum membrane distillation.In order to reduce energy consumption,the RO concentrated water treated by membrane distillation is heated by a solar collector.The fresh water vapor produced by membrane distillation is cooled by the stainless steel heat exchange coil in the RO fresh water tank and the greenhouse geothermal coil,which solves the problem of cooling water reduction in the steam condensation process of the membrane distillation system,and realizes phase change heat recovery and heats the greenhouse.Through measuring the relevant parameters of each component of the system,the solar collector effect,the RO brine desalination effect of the vacuum membrane distillation,the condensation effect of the condensing device and the heating effect of the greenhouse crop were tested and analyzed.The tests show that under the test conditions,the selected collector area can basically meet the heat requirement of membrane distillation for the whole year,the length of the stainless steel heat-dissipating coil designed in the greenhouse fresh-water tank can meet the steam condensation requirement,and the geothermal coils laid in 30-40 cm depth below the surface can meet condensation requirements and greenhouse heating requirements.The amount of freshwater produced by membrane distillation increases with the increase of the inlet temperature of the RO brine on feeding side and the vacuum pressure on the permeate side.When the inlet temperature of the RO brine on feeding side is 80°C and the vacuum pressure of permeate side is-0.080 MPa,the water production is 37.62 L/h.When the operating time of the vacuum membrane distillation system reaches 240 h,the membrane fouling increases and the water production decreases.When the hollow fiber membrane is cleaned,the water production after washing is increased by nearly 1.5 times compared with that before washing.It has been verified by experiments that the RO concentrated water desalination system by solar vacuum membrane distillation in cold area can basically meet the requirements for use.This study has important significance for reducing the energy consumption of membrane distillation system,realizing the zero discharge of RO brine,and reducing the concentration of brine in the environment.
作者
刘娟
田军仓
Liu Juan;Tian Juncang(School of Civil and Hydropower Engineering,Ningxia University,Yinchuan 750021,China;Ningxia Research Center on Technology of Water-Conservation Irrigation and Control of Water Resources Utilization,Yinchuan 750021,China;Project Research Center of China Ministry of Education on Utilization of Water Resources for Agricultural Purposes in the Dry Areas,Yinchuan 750021,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2018年第15期238-245,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(51469027)
公益性行业(农业)科研专项经费项目(201203003-4)
宁夏高等学校一流学科建设项目(NXYLXK2017A03)联合资助。
关键词
太阳能
温室
反渗透
减压膜蒸馏
RO浓水淡化
寒冷地区
solar energy
greenhouse
reverse osmosis
membrane distillation
RO brine desalination
cold area
