LNG冷能用于海水淡化和浓缩的关键影响因素研究

发布时间：2018-05-17 01:16

本文选题：LNG冷能 + 海水淡化　；参考：《北京建筑大学》2016年硕士论文

【摘要】：LNG含有宝贵的冷能,且近些年来LNG市场飞速发展,为响应节能减排、资源回收再利用号召,将LNG再气化过程释放的冷收集并加以利用。目前国内外对LNG的冷能的应用研究形式很多,LNG冷能的回收再利用已经成为必然的趋势。LNG冷能在低温发电、冷库制冷、空调、空分和低温粉碎方面的研究已经很多,且有的已经开始实际应用。冷冻法在海水淡化和浓缩方面的研究也越来越多,但是受到脱盐率不高和人工制冷需要消耗高品位电能的制约,冷冻法海水淡化在实际生产中还难以应用。本论文进行了基础实验的研究,在实验的基础上,提出了基于LNG冷能的高脱盐率海水淡化的工艺流程,并设计搭建了冷冻法海水淡化工艺模拟实验台。在研究中得到了下面一些结论:1)在基础实验研究部分,研究了传热方式对冷冻脱盐及浓缩效果的影响、重力作用对脱盐和浓缩效果的影响、离心作用对脱盐和浓缩效果的影响。通过基础实验研究得出,尽管单向传热的脱盐效果要比多向传热的脱盐效果好,但单纯的冷冻脱盐的效果有限,要想进一步提高脱盐效果,还需对冷冻所得冰产物进行重力和离心的作用;在重力脱盐过程,排出溶液量越多,冰块的纯度越高,这需要我们在实际过程中根据需求来控制重力作用的溶液排出量;环境温度是影响重力脱盐的重要因素,环境温度越高,脱盐所消耗的时间越短,且有助于重力脱盐率的提高;粉碎离心作用能够大大提高离心脱盐效果,转速是影响离心脱盐的关键因素,但当转速足够快时,再继续增加转速,对脱盐率的影响开始弱化;进行粉碎离心之前对样品冰进行微融,使冰质疏松,有助于离心脱盐率的提高;2)重力和离心的作用能够很好的弥补冷冻脱盐的不足,弱化传热方式的对脱盐效果的影响,这个结论指导我们,在冷冻阶段要尽可能的提高冷量的利用效率,生产更多的冰,然后再通过重力和离心的作用来进一步提高产物冰的脱盐效果;在进行联合作用脱盐实验时,脱盐率最高达到99.33%,此时融冰水NaCl的浓度为200mg/L,可以满足国家饮用水标准中对氯化物的浓度要求,但此时联合脱盐对应的流程相对复杂,且淡水产率较低;而且在对重力脱盐和离心脱盐的对比中发现离心脱盐是重力脱盐的加速过程,而且离心脱盐过程更加省时节能;3)在进行冷冻、重力、离心脱盐的过程中,除了得到低浓度的冰产物,同时还有高浓度的浓缩水产生,作为冷冻法海水淡水过程的副产品,这部分浓缩水可以用作盐化工的原料;4)实验台制冰脱盐率较低,冷冻脱盐的效果并不是很好,因此需通过重力、离心等方式对冰样进行进一步脱盐处理。
[Abstract]:LNG contains valuable cold energy, and in recent years, the LNG market has developed rapidly. In response to the call of energy saving and emission reduction, resource recovery and reuse, the LNG regasification process is released from the cold collection and utilization. At present, there are many research forms on the application of LNG cold energy at home and abroad. The recovery and reuse of LNG cold energy has become an inevitable trend. There has been a lot of research on LNG cold energy in low temperature power generation, cold storage refrigeration, air conditioning, air separation and low temperature comminution. And some have already started practical application. There are more and more researches on seawater desalination and concentration by freezing method, but it is restricted by the low desalination rate and the need to consume high grade electric energy by artificial refrigeration, so it is difficult to apply frozen seawater desalination in practical production. In this paper, the basic experimental research is carried out. On the basis of the experiment, the process flow of high desalinization rate seawater desalination based on LNG cold energy is put forward, and the simulation test bench of freezing seawater desalination process is designed and built. In the part of basic experimental research, the effects of heat transfer on freezing desalination and concentration, gravity on desalination and concentration, centrifugation on desalination and concentration are studied. The basic experimental results show that although the desalination effect of unidirectional heat transfer is better than that of multi-directional heat transfer, the effect of pure freezing desalination is limited, so if we want to further improve the desalination effect, In the process of gravity desalination, the more the solution is discharged, the higher the purity of ice is, which requires us to control the volume of gravity solution according to the demand in the actual process. Environmental temperature is an important factor affecting gravity desalination. The higher the ambient temperature, the shorter the desalination time is, and the higher the gravity desalination rate is, the higher the centrifugal effect is. Rotational speed is the key factor affecting centrifuge desalination, but when the rotational speed is fast enough, the effect on desalinization rate will be weakened by increasing rotational speed, and the sample ice will be slightly melted before comminuting centrifugation, and the ice will become loose. The effect of gravity and centrifugation can make up the deficiency of freezing desalination and weaken the effect of heat transfer on the desalination effect. This conclusion guides us. In the freezing stage, the utilization efficiency of cold capacity should be increased as much as possible, more ice should be produced, and then the desalination effect of the product ice should be further improved by gravity and centrifugation. The highest desalinization rate was 99.33, and the concentration of NaCl in melted water was 200mg / L, which could meet the requirement of chloride concentration in the national drinking water standard, but the process of combined desalination was relatively complex, and the yield of fresh water was relatively low. In the comparison of gravity desalting and centrifugal desalting, it is found that centrifugal desalination is an accelerated process of gravity desalination, and the centrifugal desalting process saves more time and energy.) during the process of freezing, gravity, centrifugal desalination, In addition to the low concentration of ice products, there is also a high concentration of concentrated water, which, as a by-product of the freshwater process of the freezing process, can be used as the raw material for salt chemical industry.) the desalinization rate of ice is relatively low on the experimental bench. The effect of freezing desalination is not very good, so it is necessary to further desalinate the ice sample by gravity and centrifugation.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P747

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