基于LNG冷能的海水脱盐实验研究

发布时间：2018-06-08 15:13

本文选题：海水淡化 + 冷冻脱盐　；参考：《北京建筑大学》2017年硕士论文

【摘要】：海边LNG接收站内LNG气化所产生的冷能目前只有20%~30%被利用,造成了能源浪费并对环境形成冷污染,与此同时,淡水资源缺乏使海水淡化产业发展迅速。海水淡化方法中冷冻法没有用于商业推广的主要原因是冷能成本高和脱盐率低。若能将LNG冷能用于海水淡化,并结合其他脱盐方式提高脱盐率,对基于冷冻法的海水淡化技术发展是很有意义的。本文针对基于冷冻过程和LNG冷能的海水淡化问题开展了两部分实验研究工作,即基于冰箱内静态制冰过程的实验和基于LNG冷能的海水淡化工艺模拟实验。本文实验目的在于构建基于冷冻过程的复合脱盐方法并研究影响总体脱盐率的主要因素。冰箱内实验主要是研究了冷冻过程中结冰速率和结冰率以及冷冻、冷冻+重力脱盐、冷冻+粉碎+离心脱盐三种脱盐方式对脱盐和浓缩效果的影响。实验得到以下结论:(1)冷冻脱盐的脱盐率随结冰速率的增大而减小,随结冰率的增大先增大后减小。相同条件下,单向传热的脱盐效果比多向传热的脱盐效果好。冷冻+重力脱盐效果明显优于单纯冷冻脱盐的效果。冷冻+离心相结合可以提高脱盐效果,并且其效果优于冷冻+重力的脱盐效果。冷冻+重力+离心脱盐,脱盐率大于95%,若把条件优化,有望达到国家饮用水的质量浓度标准。基于冰箱内静态制冰过程的实验,设计了基于LNG冷能的海水淡化工艺模拟实验方案,主要开展了冷媒算术平均温度对脱盐效果的影响实验,并得到以下主要结论:(2)在实验装置冷冻制得的冰,随冷媒算术平均温度的增加,冰质地的松散程度越来越大;冰的脱盐率随冷媒算术平均温度的增加而降低,原因可能是冷媒温度高所制得的冰质疏松,容易携带更多的原海水。冷冻+重力脱盐、冷冻+离心脱盐、冷冻+重力+离心脱盐的脱盐率随冷媒算术平均温度的增加而增加,与冰箱内静态制冰实验一致。(3)采用冷冻+离心脱盐与冷冻+重力+离心脱盐方法对Mg2+、Ca2+、Cl-的脱除率随冷媒算术平均温度的增加而升高,而冷冻+重力脱盐中Mg2+、Cl-的脱除率随冷媒算术平均温度的增加而升高,Ca2+的脱除率随冷媒算术平均温度的增加而降低。(4)在本文实验中得到的浓盐水(浓海水)的浓度不能直接到到日晒制卤所达到的盐度17.7%的标准,但大部分浓盐水浓度都高于6%,可以节约占地面积,加快制盐速度,有生产意义。(5)浸泡与粉碎都能提高冷冻离心的脱盐率,但会降低冷冻脱盐过程的产水率,其他影响因素还需进一步研究。(6)不同条件下形成的冰体微观结构不同,需要进一步研究探究其规律。
[Abstract]:At present, only 20% of the cold energy generated by LNG gasification in the LNG receiving station by the sea has been utilized, which has caused energy waste and cold pollution to the environment. At the same time, the lack of fresh water resources has made the desalination industry develop rapidly. The main reasons for the lack of commercial application of freezing method in seawater desalination are high cold energy cost and low desalinization rate. If LNG cold energy can be used in seawater desalination and other desalination methods can be used to increase desalination rate, it will be of great significance to the development of seawater desalination technology based on freezing method. In this paper, two parts of experimental research on seawater desalination based on freezing process and LNG cold energy are carried out, that is, the static ice making process in refrigerator and the simulation experiment of seawater desalination process based on LNG cold energy. The purpose of this paper is to construct a composite desalination method based on freezing process and to study the main factors affecting the total desalination rate. The effects of freezing rate, freezing rate and freezing, gravity desalination and centrifugal desalination on desalination and concentration were studied in refrigerator. The following conclusions are obtained: (1) the desalinization rate decreases with the increase of freezing rate and increases first and then decreases with the increase of freezing rate. Under the same conditions, the desalination effect of unidirectional heat transfer is better than that of multidirectional heat transfer. The effect of freezing gravity desalting is better than that of pure freezing desalination. Combined freezing centrifugation can improve the desalting effect, and its effect is better than that of freezing gravity. The desalination rate of freezing gravity centrifugal desalination is greater than 95. If the conditions are optimized, it is expected to reach the national drinking water quality concentration standard. Based on the experiment of static ice making process in refrigerator, the simulation scheme of seawater desalination process based on LNG cold energy was designed, and the effect of arithmetic average temperature of refrigerant on desalination effect was mainly carried out. The main conclusions are as follows: (1) with the increase of the arithmetic mean temperature of refrigerant, the looseness of ice texture increases, and the desalinization rate of ice decreases with the increase of arithmetic mean temperature of refrigerant. The reason may be that the ice produced by the high temperature refrigerant is loose and easy to carry more raw seawater. The desalination rate of freezing gravity desalination, freezing centrifugal desalination and freezing gravity centrifuge desalination increases with the increase of the arithmetic mean temperature of refrigerant. The desalination rate of mg _ 2 ~ (2 +) Ca ~ (2 +) Cl ~ (-) increased with the increase of the arithmetic mean temperature of refrigerant by freezing centrifugal desalination and freezing gravity centrifugation desalination. However, the removal rate of Mg2 + Cl- in freezing gravity desalination increased with the increase of the arithmetic mean temperature of refrigerant. The removal rate of Ca 2 + decreased with the increase of arithmetic mean temperature of refrigerant. The degree of salinity cannot be reached directly to the standard of 17.7% of the salinity of the brine made by the sun, But the concentration of most of the concentrated brine is higher than 6, which can save land area, accelerate the speed of salt making, have productive significance. Soaking and crushing can increase the desalinization rate of freezing centrifugation, but it will reduce the water production rate in the process of freezing desalination. Other influencing factors need to be further studied. (6) the microstructure of ice body formed under different conditions is different, and the law of ice body formation needs to be further studied.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P747

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