基于机械热泵的海水淡化零排放研究

发布时间：2018-07-31 08:05

【摘要】：海水淡化是一种高能耗产业,目前,市场上主流的海水淡化方法主要有反渗透海水淡化,多级闪蒸海水淡化,低温多效海水淡化等。反渗透海水淡化对于海水的品质有较高的要求,适应性能比较弱,多级闪蒸海水淡化系统的能耗较高,低温多效方法现在已经日趋成熟,得到广泛应用。然而热法海水淡化实现零排放时能耗大,传统的膜法海水淡化方法无法实现零排放,而是将海水盐浓度浓缩至6%后,直接排入大海。长此以往,高盐浓度的海水直接排入大海对周围海域的生态环境会造成不良影响。随着世界能源危机和环境危机问题的日益显著,设计并开发新型低能耗清洁的海水淡化系统迫在眉睫。本文以机械热泵技术为背景,设计出了海水淡化的零排放系统,将盐浓度为3%的海水浓缩至28.92%,结晶之后系统产物为淡水和盐。通过对单级、两级和三级系统的能耗比较,在此基础上,针对一级系统进行能量分析,主要做出口海水盐浓度变化对系统火用损的影响,其中可以达到零排放效果的只有出口浓度为28.92%。分析结果表明,随着出口浓度的不断增加,系统的火用损呈缓慢上升趋势。针对两级海水淡化系统进行火用分析,建立系统主要部件的火用模型。两级海水淡化零排放系统具体分析了一级闪蒸出口的海水盐浓度对整个系统火用损的影响,结果表明,系统火用损随着一级闪蒸出口的海水浓度的升高,并不呈单一趋势变化,而是先下降后升高。故以一级闪蒸出口的盐浓度为自变量,拟合出系统火用损的函数,并根据拟合结果可以得到系统火用损的曲线,通过对函数的求导,可以得出最具节能效果的浓度分配,结果表明,一级闪蒸出口的海水盐浓度在10%的时候,整个系统的火用损达到最小值。此外,通过本实验室既有的处理高浓度含盐废水的工程实践结果,即采用同样的方法对高浓度含盐废水的处理实验进行分析,得到的结果与工程实践结果进行对比,可以证明此种分析方法具有较强的适用性和可靠性。最后,针对三级系统,本文采用多变量优化分析的方法,针对系统中一级和二级的出口海水盐浓度的变化,分析了系统总的能耗变化,介绍了多变量分析理论,并将其运用到海水淡化系统分析中去。本文从经济和耗能角度对一级、二级和三级海水淡化系统进行分析。
[Abstract]:Seawater desalination is a kind of high energy consumption industry. At present, the main desalination methods in the market include reverse osmosis desalination, multi-stage flash desalination, low-temperature multi-effect seawater desalination and so on. Reverse osmosis seawater desalination has higher requirements for seawater quality, weak adaptability, high energy consumption of multi-stage flash desalination system, and has become increasingly mature and widely used in low-temperature multi-effect desalination system. However, the traditional membrane desalination method can not achieve zero discharge when the thermal desalination achieves zero discharge. Instead, the concentration of seawater salt is concentrated to 6% and discharged directly into the sea. In the long run, sea water with high salt concentration will have adverse effects on the ecological environment of the surrounding sea. With the world energy crisis and environmental crisis increasingly prominent, it is urgent to design and develop a new low energy consumption and clean desalination system. Under the background of mechanical heat pump technology, a zero discharge system for desalination of seawater is designed. The salt concentration of 3% seawater is concentrated to 28.92%. After crystallization, the products of the system are fresh water and salt. By comparing the energy consumption of single-stage, two-stage and three-stage systems, on the basis of this, the energy analysis of the primary system is carried out, and the influence of salt concentration change at the outlet on the exergy loss of the system is mainly done. Only the export concentration of 28.92% can achieve zero emission effect. The results show that the exergy loss of the system increases slowly with the increasing of outlet concentration. The exergy analysis of two-stage seawater desalination system is carried out and the exergy model of the main components of the system is established. The effect of seawater salt concentration at the primary flash outlet on the exergy loss of the whole system is analyzed in detail in a two-stage desalination zero discharge system. The results show that the exergy loss of the system does not change with the increase of seawater concentration at the primary flash outlet. But first down and then up. Therefore, the function of exergy loss of the system is fitted with the salt concentration at the outlet of the first stage flash, and the curve of the exergy loss of the system can be obtained according to the fitting results. Through the derivation of the function, the concentration distribution with the most energy saving effect can be obtained. The results show that the exergy loss of the whole system reaches the minimum when the salt concentration at the outlet of the first stage flash is 10%. In addition, through the existing engineering practice results of the treatment of high concentration salt-containing wastewater in our laboratory, that is, using the same method to analyze the treatment experiment of the high-concentration salt-containing wastewater, the results obtained are compared with the engineering practice results. It can be proved that this analytical method has strong applicability and reliability. Finally, aiming at the three-level system, this paper uses the method of multivariable optimization analysis to analyze the total energy consumption change of the system, and introduces the theory of multivariable analysis, aiming at the change of salt concentration in the first and second level of the system. It is applied to the analysis of seawater desalination system. In this paper, the primary, secondary and tertiary desalination systems are analyzed from the point of view of economy and energy consumption.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P747
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本文编号：2154953