System for desalinating seawater by waste heat from power plant

Abstract

The invention discloses a system for desalinating seawater by waste heat from a power plant. The system comprises a condenser circulating seawater taking branch system, a seawater multi-stage fresh evaporation branch system and a boiler smoke waste heat heating seawater circulating branch system which are divided according to the flow direction of seawater to be desalinated, and also comprises a vacuum pumping branch system, and a fresh water and seawater pollution discharge branch system, wherein the vacuum pumping branch system and the fresh water and seawater pollution discharge branch system are used as auxiliary systems connected with the seawater multi-stage fresh evaporation branch system. A multi-stage fresh evaporation method is adopted by the system. Because the waste heat of a condenser and boiler smoke of a power plant is utilized, energy sources needed for desalinating the seawater in a conventional distillation method are omitted, the operating cost in desalinating the seawater in a distillation method is reduced, and simultaneously the prepared fresh water is distilled water which can be partially used as supplementing water for the boiler of the power plant, the treatment cost for softening water in the power plant is saved, energy is saved, and the environment is protected.

Description

technical field [0001] The invention relates to the field of seawater desalination, in particular to a system for desalinating seawater by using waste heat from a power plant. Background technique [0002] There are many methods for desalination of seawater, and the main ones that can achieve large-scale and industrialization are membrane method and thermal method. The membrane method is also called the reverse osmosis method, which utilizes the principle of osmotic pressure. This method uses a semi-permeable membrane to separate the fresh water from the salt. Under normal circumstances, a semipermeable membrane allows the solvent in the solution to pass through, but does not allow the solute to pass through. Due to the high salt content of seawater, if a semipermeable membrane is used to separate seawater from freshwater, the freshwater will diffuse to one side of the seawater through the semipermeable membrane, thereby raising the liquid level on the seawater side until ...

AI Technical Summary

Problems solved by technology

The large amount of water used in thermal power plants includes two parts, one part is the pure water for burning steam required by the boiler and the water used by the system itself, this part is treated fresh water; the other part is the circulating water for cooling the exhaust steam of the steam turbine, this part can be It is river water or sea water; the circulating water condenses the waste steam of the steam turbine after doing work into water in the condenser after the steam turbine, and the latent heat released by the condensation of the exhaust steam is taken away by this part of the circulating water. For thermal power plants on the seaside, this part The heated circulating water is directly discharged into the sea, causing a great waste of energy. However, there is no good and feasible method for the utilization of this low-temperature heat source.

[0005] The seawater circulating water from the condenser is about 40°C. If fresh water is produced by flash evaporation at this temperature, both the output and your efficiency are very low. Assuming that the fresh water is produced by flash evaporation with a temperature difference of 10°C, the enthalpy drop It is only 42kj / kg, so the amount of flash fresh water per kilogram of 40°C seawater is only about 0.017kg. If you consider the cost of electricity consumption, it is undoubtedly uneconomical to produce fresh water

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