Multi-effect membrane distillation-multistage flash evaporation seawater desalination system

Abstract

The invention discloses a multi-effect membrane distillation-multistage flash evaporation seawater desalination system. The multi-effect membrane distillation-multistage flash evaporation seawater desalination system comprises a steam jetting pump (9), a concentrated water discharge pump (1), a material liquid circulating pump (2), a vacuum pump (3), a product water pump (4), N membrane assemblies, N freshwater flash evaporation tanks, N+1 heat exchange assemblies and N-1 concentrated water flash evaporation tanks, wherein the plurality of membrane assemblies and heat exchange assemblies are connected in series to form 'multi-effect' distillation in the term of the traditional distillation; the plurality of freshwater flash evaporation tanks and the plurality of concentrated water flash evaporation tanks are connected in series to form 'multistage' flash evaporation in the term of traditional distillation; the multi-effect membrane distillation process and the multistage flash evaporation process are coupled, secondary steam generated by membrane distillation is used for heating material liquid seawater, high-temperature concentrated seawater and product water which are discharged by membrane distillation are subjected to flash evaporation stage by stage, and the flash-off steam is used for heating material liquid seawater, so gradient utilization of energy and double concentration of the material liquid are realized, vaporized latent heat is effectively recovered, and heat efficiency, water making ratio and concentration ratio of a system are increased.

Description

technical field [0001] The invention belongs to the technical field of membrane separation and seawater desalination, and relates to a multi-effect membrane distillation-multistage flash seawater desalination system. Background technique [0002] Water is the source of life. Fresh water is one of the material foundations for the survival and development of human society. With the rapid development of society, population increase and water pollution, fresh water resources are becoming more and more scarce, and the world is facing an increasingly serious water resource crisis. [0003] Seawater desalination is one of the important methods to solve the crisis of freshwater resources. Seawater desalination, also known as seawater desalination, is the technology and process of separating salt and water in seawater, and its essence is "exchanging energy for water source". At present, the three mainstream seawater desalination technologies commercialized are multiple-effect dist...

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Problems solved by technology

[0006] Membrane distillation is a membrane separation process based on evaporation. The heat is transferred from the feed liquid side to the permeate in the form of phase change heat transfer, so the energy consumption is high, which is also one of the key problems limiting its industrial application.

[0007] The Chinese invention patent with the application publication number CN102107119A discloses a "multi-effect membrane distillation device and method". The proposed multi-effect membrane distillation consists of three parts: a heating evaporation zone, a main evaporation zone and a cooling zone. The water vapor condensation in the process is coupled with the raw water heating process, and the latent heat of evaporation is recovered, which is conducive to improving the thermal efficiency of membrane distillation. However, the shortcomings of this device are: the latent heat of vaporization of high-temperature fresh water has not been utilized, and the thermal efficiency of the system is not high; lower

[0008] The Chinese invention patent with the application publication number CN103071388A discloses a "steam thermal compression decompression membrane distillation device". Utilizing the latent heat of steam has certain significance for improving the thermal efficiency of membrane distillation, but the shortcomings of the device are: the latent heat of vaporization of steam has not been utilized in stages, the latent heat of vaporization of concentrated water and fresh water has not been recovered, and the thermal efficiency of the system and the recovery rate of fresh water are relatively low.

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