采用高效纳滤—低压反渗透集成膜工艺的海水淡化研究

发布时间：2018-05-14 14:02

本文选题：高效纳滤 + 低压反渗透　；参考：《宁波大学》2015年硕士论文

【摘要】：在海水淡化系统中引入纳滤(NF)技术是降低系统能耗的一个方向。然而,常规的纳滤-反渗透海水淡化(NF-SWRO)系统,由于第一级NF脱盐率不够高,往往导致其第二级RO的操作压力大和整体的能耗过高。为了得到降低系统的设备要求和能耗的方法,本文提出并探讨了高效纳滤-低压反渗透(HRNF-LPRO)的集成膜的新型海水淡化工艺,即第一级采用高脱盐的纳滤,第二级用适合苦咸水脱盐的低压反渗透。实验中选用NF90型纳滤膜和BW30型低压反渗透膜搭建小型实验装置,对HRNF-LPRO工艺进行了实验验证研究,并在实验的基础上,使用陶氏反渗透设计软件(ROSA)对HRNF-LPRO工艺进行模拟,以验证HRNF-LPRO工艺应用于大型海水淡化装置的可行性和能耗问题。在NF脱盐的实验研究中,膜的通量和截留性能,是受操作压力、给水浓度、给水温度等条件的影响。实验表明:操作压力升高,NF90膜通量升高,溶质截留率增加;给水浓度增加,膜通量大幅降低,溶解固体总量(TDS)和一价离子截留率也稳定下降,对二价离子截留率的影响很小或下降不多;给水温度增加,膜通量近似线性增加,TDS和一价离子截留率则稳定下降,对二价离子截留率的影响很小或降幅不大。在常温20°C、标准人工海水(34998ppm)给水和2.6MPa时,膜通量和TDS截留率分别可达到9.61L/m2·h和82.73%。LPRO的实验中,同样考察操作压力和给水浓度、温度对BW30膜通量和截留性能的影响,实验表明:压力升高,BW30的通量近似线性增加,给水浓度增加则通量稳定下降;压力增加,LPRO的截留率随之增加,给水浓度增加时,截留率下降,低压时降幅大,压力增加后降幅小。在小规模的实验中,采用HRNF和LPRO联用的两极系统,可脱除人工海水中99.84%的盐分而淡化海水。HRNF-LPRO工艺能显著降低第二级脱盐操作压力和产水能耗,即第二级脱盐压力从6.6MPa左右降至小于3.0 MPa,同时第一级操作压力相差不大。在没有使用变频器和能量回收涡轮等节能装置时能耗至少降低1k Wh/m3。在ROSA的模拟中,两级分别采用1280支NF和480支LPRO膜元件,选用常温和3.5%太平洋海水的典型给水条件,即20°C和34967.39ppm,模拟的最终产水TDS为231.17ppm,盐截留率99.34%,淡水产量为44.65 m3/h,总回收率44.65%,在没有使用变频技术和涡轮能量回收装置的条件下,综合产水能耗为4.527k Wh/m3。采用能量回收装置(90%回收),综合产水能耗可降至3.264 k Wh/m3,低于现有的NF-SWRO工艺在采用了节能技术的能耗,3.7-5.8 k Wh/m3。HRNF-LPRO除了海水淡化工艺有显著的节能优势外,其231.17ppm的产水TDS含量与NF-LPRO工艺差距不大,并且,与NF-SWRO工艺相比,都是采用的两级脱盐工艺,不会增加工艺的复杂性。因此,HRNF-LPRO是一种有发展前途的低能耗的海水淡化工艺。实验和模拟研究表明,HRNF-LPRO集成膜海水淡化工艺在降低设备要求和降低产水成本上有实际意义。
[Abstract]:The introduction of NFN in seawater desalination system is a direction to reduce the energy consumption of the system. However, the conventional nanofiltration reverse osmosis seawater desalination (NF-SWRO) system, because the first stage NF desalination rate is not high enough, often lead to the second stage RO operation pressure and the overall energy consumption is too high. In order to reduce the equipment requirement and energy consumption of the system, a new seawater desalination process with high efficiency nanofiltration and low pressure reverse osmosis (HRNF-LPROP) integrated membrane is proposed and discussed in this paper, that is, the first stage is high desalination nanofiltration. The second stage is suitable for desalting brackish water under low pressure reverse osmosis. In the experiment, NF90 nanofiltration membrane and BW30 low pressure reverse osmosis membrane were selected to build a small experimental device. The HRNF-LPRO process was tested and studied. On the basis of the experiment, Dow reverse osmosis design software was used to simulate the HRNF-LPRO process. In order to verify the feasibility and energy consumption of HRNF-LPRO process applied to large seawater desalination plant. In the experimental study of NF desalting, membrane flux and retention performance are affected by operating pressure, feed water concentration and feed water temperature. The experimental results show that the flux of NF90 increases with the increase of operating pressure, the retention rate of solute increases with the increase of feed water concentration, the flux of membrane decreases significantly, the total dissolved solids (TDSs) and the rejection rate of monovalent ions also decrease steadily. The effect on the bivalent ion rejection rate is very little or small, while the membrane flux increases linearly with the increase of feed water temperature, TDs and monovalent ion retention rate decrease steadily, and the effect on the bivalent ion rejection rate is very little or little. At 20 掳C at room temperature, the membrane flux and the TDS retention rate can reach 9.61L/m2 h and 82.73%.LPRO respectively under the conditions of standard artificial seawater water supply and 2.6MPa. The effects of operating pressure, feed water concentration and temperature on the membrane flux and retention performance of BW30 were also investigated. The experimental results show that the flux of BW30 increases linearly and the flux decreases steadily with the increase of feed water concentration, and the rejection rate of LPRO increases with the increase of pressure, and decreases with the increase of feed water concentration. The pressure increases after the decline is small. In a small scale experiment, the two-pole system combined with HRNF and LPRO can remove 99.84% of the salt in artificial seawater and desalinate seawater. HRNF-LPRO process can significantly reduce the second stage desalination operation pressure and water production energy consumption. The desalination pressure of the second stage is reduced from about 6.6MPa to less than 3. 0 MPA, and the first stage operation pressure is not different. Reduce energy consumption by at least 1 k / m 3 without the use of energy-efficient devices such as inverters and energy recovery turbines. In the simulation of ROSA, 1280 NF and 480 LPRO membrane elements were used in the two stages, and the typical water supply conditions of normal temperature and 3.5% Pacific water were selected. That is, 20 掳C and 34967.39 ppm, the simulated final water production TDS is 231.17 ppm, salt rejection rate is 99.34, fresh water output is 44.65 m3 / h, total recovery rate is 44.65 ppm, and without frequency conversion technology and turbine energy recovery device, the energy consumption of integrated water production is 4.527 k / m ~ (3). With 90% energy recovery unit, the comprehensive energy consumption of water production can be reduced to 3.264 kWhs / m3, which is lower than that of the existing NF-SWRO process. In addition to seawater desalination process, the energy consumption of 3.7-5.8k Wh/m3.HRNF-LPRO with energy saving technology has obvious advantages in energy saving. The water TDS content of 231.17ppm is not far from that of NF-LPRO process, and compared with NF-SWRO process, the two-stage desalination process is adopted, and the complexity of the process will not be increased. So HRNF-LPRO is a promising and low energy consumption desalination process. Experimental and simulation results show that HRNF-LPRO integrated membrane seawater desalination process has practical significance in reducing equipment requirements and water production cost.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P747.5

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