Multi-stage series membrane distillation strong brine desalting method and device

Abstract

The invention relates to a method for treating strong brine by using multi-stage series membrane distillation. The method comprises three steps of: preheating before performing strong brine membrane distillation, performing membrane distillation and condensing distilled steam to obtain desalted water, and is characterized in that: during membrane distillation, 3 to 5 stages of membrane distillation units are adopted; a membrane component (a membrane area) of each stage of the membrane distillation unit is different according to an operating scale; and the membrane components are connected in series with one another. In the multi-stage membrane distillation unit mode for treating the strong brine, the strong brine distilled by the previous stage is directly used as material inlet liquid in the next stage; as the whole process is continuous, the temperature required by the process is low; the temperature of the strong brine of the previous stage of the membrane distillation unit meets the requirement on the water inlet temperature of the next stage of the membrane distillation, so that heat sources required by the later stages of membrane distillation are saved, and the heat utilization rate during membrane distillation is increased; the heat sources for heat exchange can be low-level heat sources, such as raw stream, solar energy, terrestrial heat, factory waste heat and the like, so that energy can be saved effectively; and the comprehensive cost of the membrane distillation method for treating the liquid is reduced.

Description

technical field [0001] The invention belongs to the technical field of seawater desalination, and relates to membrane separation technology, in particular to a method for desalination of concentrated brine by multi-stage serial membrane distillation and a device for desalination of concentrated brine. Background technique [0002] As we all know, fresh water is one of the basic materials for the survival and development of human society. With the rapid development of economy, the increase of population and the increasingly serious water pollution, the world is facing a serious crisis of fresh water resources, especially in coastal cities. my country is a country seriously short of fresh water resources, and the per capita water resources are only 1 / 6 of the world average. [0003] Seawater desalination is the main way to solve the crisis of freshwater resources, but the cost of seawater desalination has always been the main problem restricting the development of seawater des...

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Problems solved by technology

[0007] The existing technology uses a first-stage membrane distillation unit to treat seawater. The concentration of concentrated water after distillation is very small. From an industrial point of view, the concentration of brine after treatment basically does not change much, and the high-temperature concentrated water comes out directly Discharge will cause a certain amount of heat loss, which is not economically reasonable

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