【作者】 王越；

【导师】 王世昌；

【作者基本信息】 天津大学 ， 化学工程， 2004， 博士

【摘要】 反渗透海水（和高浓度苦咸水）淡化系统中，高压浓盐水的余压能量回收装置按工作原理可分为离心式和正位移式两种类型。离心式又称为水力透平式，其能量回收效率相对较低（30%~50%）。正位移式能量回收效率高达90%以上，目前在淡化市场上被较多采用，也成为研究的重点和热点。本文工作中设计和研究的阀控余压能量回收装置（VC-ERD）即采用正位移式原理，利用阀和水压缸来实现能量交换。论文首次提出了研究VC-ERD的工艺流程，并建立了相应的实验装置、阀门控制系统和计算机数据采集系统等。实验流程包括两个水平放置的由有机玻璃制作的水压缸，长度为1米，内径为50mm，最高工作压力1.0MPa。另外，实验流程中还包括一个高压离心泵、一个低压离心泵和两个贮罐，以及安装在水压缸端部的阀门和系统管件等。采用PLC和光电开关相结合的方式来实现阀门的程序控制。开发了与手动操作、单缸操作、双缸操作和两个单缸耦合操作过程相对应的阀门控制方案。首次对不同控制方案下VC-ERD的动态特性进行了测试和分析。结果表明，过程等待时间为0秒时，无论单缸操作或双缸操作都存在部分高压盐水与泄压盐水之间的串水（或称短路）问题。对本实验装置而言，当等待时间为1.5秒时，串水问题可得到解决。此时对单缸操作而言，高压盐水、低压海水的流量和压力均呈矩形波的变化规律；增压海水的流量变化与高压盐水的流量变化相似，但其压力始终保持不变。对双缸操作而言，高压盐水、低压海水和增压海水的流量均呈周期性向下波动的变化；高压盐水、低压海水的压力呈周期性向上波动的变化，而增压海水的压力则保持在一个稳定的水平上。与双缸操作相比，两个单缸耦合操作时流量和压力的变化频率降低约一半左右。水压缸端部压力在上述三种控制方案下都呈矩形波的变化。在实验工况下对装置能量传递效率的研究结果表明：阀控余压能量回收装置的容积效率可近似为100%；压力效率与盐水压力呈正比的变化关系，与海水压力呈反比的变化关系；当盐水压力约为0.9MPa时，压力效率为90%。研究结果还表明该类型能量回收装置用于海水或苦咸水淡化时，能量传递效率达将在90%以上。论文同时也对活塞惯性距离、过程循环频率及装置在工作过程中的阻力分布等问题进行了研究和讨论。 <WP=3>论文首次建立了水压缸运行中高压浓盐水和原料海水混合的模拟方法。通过流体力学模拟计算，对水压缸中浓盐水与原料海水的混合段长度及其影响因素系统研究的结果表明：增加盐水入口管直径与水压缸直径之比或增大盐水入口流速均能增加混合长度；形成的混合长度随着累积时间的增加而增大，降低了水压缸的容积利用率；提高海水排出浓度或降低系统的回收率均会提高容积利用率；增加水压缸长度有利于大幅度提高容积利用率。论文首次提出了VC-ERD的设计步骤，并完成天津市1000吨/天反渗透海水淡化示范工程用VC-ERD的技术方案设计。更多还原

【Abstract】 Hydraulic energy recovery device for application in the reverse osmosis desalination system can be clasified into two categories by their working principle, the centrifugal type and the positive displacement type. The centrifugal type, also named hydraulic turbine type has an efficiency between 30% and 50%. The efficiency of the positive displacement type which is more used in desalination plants now is as high as 90% or above. It has become a research focus of this field. The valve-controlled energy recovery device (VC-ERD) designed in our research project is of the positive displacement type. It uses valves and cylinders to accomplish the energy exchange process. The flow diagram to test the VC-ERD was given for the first time. Corresponding experimental apparatus with valve controlling system and data acquisition system was set up. Two cyclinders made of organic glass with a length of 1000mm, internal diameter of 50mm were included in the experimental diagram. A high pressure centrifugal pump and a low pressure centrifugal pump were used to supply water from two corresponding tanks. The programmable logic controller (PLC) combining the photoelectric switches was used to control the movements of the valves sequentially. The controlling schemes of the manual operation, the single-cylinder operation, the double-cylinder operation, and two single-cylinder coupling operation were developed respectively. Dynamic characteristics of the unit under different controlling schemes were measured and analyzed for the first time. The experimental results indicate that there always exists colluding problem between the high pressure (HP) concentrate and the depressed concentrate, whether it is under single-cylinder or double-cylinder operation with the standing time remaining zero seconds. In our experiments, the colluding problem can be dealt with successfully when standing time of the process is 1.5 seconds. At this time, for the single-cylinder operation, the flow and the pressure curves of the HP concentrate and the low pressure (LP) seawater vary like a rectangular wave. The flow rate variation of the pressurized seawater is similar to that of the HP concentrate, while its pressure keeps constant mostly. For the double-cylinder operation, the flow curves of the HP concentrate, the LP seawater and the pressurized seawater present a downward variation periodically, while their <WP=5>pressure curves show an upward variation periodically for the former two and a horizontal linear variation for the later. Comparing to the double-cylinder operation, the changing frequencies of the flow and the pressure curves of the HP concentrate, the LP seawater and the pressurized seawater reduce to about a half under the two single-cylinder coupling operation. Pressure curves of the cylinder end show a rectangular wave variation under the three controlling schemes mentioned above. Studies on the energy transfer efficiency of the unit under the experimental conditions indicate that the volumetric efficiency of the VC-ERD keeps 100% mostly, the pressure of the concentrate has a positive effect and that of the seawater a negative effect on the hydraulic efficiency. The hydraulic efficiency will be 90% when the concentrate pressure gets to 0.9 MPa. It is believed that the energy transfer efficiency is sure to be over 90% when the VC-ERD is used in seawater or brackish water reverse osmosis desalination processes. Other aspects such as the slip distance of the piston, the cyclic frequency and the pressure differential distributions of the process were studied and discussed at the same time. The method to simulate the mixing processes in the cylinder between the high pressure concentrate and the seawater feed was established for the first time. The mixing length in the cylinder which is the basic data for the design of the fluid piston, and its influencing factors were studied and analyzed through the fluid dynamis analog calculation. It has been found that the mixing length can be added by increasing the diameter ratio or the concentrat更多还原