【作者】 成怀刚；

【导师】 王世昌；

【作者基本信息】 天津大学 ， 化学工程， 2007， 博士

【摘要】 露点蒸发淡化技术以空气为载体,通过海水或苦咸水对其增湿和去湿来制取淡水,同时将去湿过程的冷凝潜热传递至增湿侧以促进盐水的气化,强化增湿过程。基于露点蒸发过程特定的工艺条件,本文首次将石墨聚丙烯和聚丙烯材质的传热管用于管壳式露点蒸发淡化装置,并通过管内表面的粗糙化处理促进盐水形成液膜,增加气-液两相接触面积。通过一系列工艺实验和传热实验,考察了淡化装置在不同操作条件下的产水能力。结果表明,进口盐水的温度越高,淡水产率越高,而进料盐水、载气和外加蒸汽的流量则应控制在一定的范围之内。在盐水进口温度为70~90°C的条件下,石墨聚丙烯装置的淡水产率为0.05~0.30 kg m-2 h-1,适宜的进料盐水、载气和外加蒸汽的流量分别是0.008~0.012 kg m-1 s-1、0.66~1.00 kg m-2 s-1和0.006~0.014 kg m-2 s-1;聚丙烯装置淡水产率可以达到0.10~0.68 kg m-2h-1,盐水、载气和外加蒸汽适宜操作流量为0.008~0.012 kg m-1s-1、0.70~1.30 kg m-2s-1和0.006~0.014 kg m-2s-1。两套淡化装置的淡水水质优良,含盐量均在10 mg L-1以下。考察了不同的热量回收模式下淡化系统的运行规律。用冷凝回收和载气循环的方式分别实现了露点蒸发过程中尾气的回用,并考察了这两种操作模式对整个淡化系统的影响。对包括冷凝器在内的整个露点蒸发过程而言,结合良好的热量回收措施,淡化系统的造水比可以达到4以上。基于经典的化工传递理论,建立了描述露点蒸发淡化过程的数学模型。在模拟的基础上,对淡化柱内各流体物性参数(气相和水相的温度、壳程载气中不凝气的含量、气相雷诺数、传质系数、传热系数、盐水和淡化水流量)的局部分布进行了理论分析,进一步从理论上讨论了淡化过程中操作条件对淡化柱运行性能的影响。结果表明石墨聚丙烯淡化柱的总传热系数90~430 W m-2°C-1,聚丙烯淡化柱的总传热系数则达到了250~1100 W m-2°C-1,传热效果不低于金属材质的淡化柱。更多还原

【Abstract】 The dewvaporation is a novel desalination process, in which air is used as a carrier gas to carry water vapor from feed saline water and to produce fresh water by the following condensation, and the condensation latent heat is transferred to the evaporation side to provide evaporative latent heat for the saline water.In this work, two baffled shell-tube desalination columns (one was equipped with carbon-filled-polypropylene heat transfer tubes and the other was polypropylene tubes) were designed and built to carry out the dewvaporation process. The inside surfaces of these tubes were roughened, which greatly improved their wetting states.The effects of several operating parameters (feed water temperature, water flow rate, carrier air flow rate and external steam flow rate) on the productivity of the two columns were investigated experimentally. The fresh water productivity of the carbon-filled-polypropylene column was usually 0.05~0.30 kg m-2h-1, and the experimental results showed that the feed water temperature had an positive effect on the productivity, while the flow rates of feed water, carrier air and external steam should be optimized in the range of 0.008~0.012 kg m-1s-1, 0.66~1.00 kg m-2s-1and 0.006~0.014 kg m-2s-1, respectively. As for the polypropylene column, the productivity could be achieved about 0.10~0.68 kg m-2h-1, and the suitable operating ranges for the flow rates of feed water, carrier air and external steam were 0.008~0.012 kg m-1s-1, 0.70~1.30 kg m-2s-1 and 0.006~0.014 kg m-2s-1, respectively.The salinity of the produced water was determined to be fewer than 10 mg L-1, which was comparable to that of the traditional thermal desalting processes.The discharged heat energy of the humid air was recovered by recycling or condensing the exhaust gas. When the carrier gas was condensed, it was found that the gained out ratio of the whole desalination system had been improved to above 4.The modeling investigation of such a desalination process was also presented. A heat-mass transfer model is established in order to study the correlations among productivity, thermal efficiency, physicochemical parameters (gas/liquid phase temperatures, heat/mass transfer coefficients, Reynolds number, etc) and operating conditions (the temperature of feed water, the flow rates of external steam, feed water and air); at the same time, the effects of operating conditions on the productivity and thermal efficiency of the column are investigated both theoretically and experimentally. Furthermore, the heat transfer coefficient of the carbon-filled-polypropylene dewvaporation column is in the range of 90~430 W m-2°C-1, and that of polypropylene column is 250~1100 W m-2°C-1, which demonstrates that the heat transfer performance of the plastic element is not lower than that of the coppery element.更多还原