Segment water-water preheating multiple-effect distillation sea water desalination technical process

Abstract

The invention relates to a sectional multiple-effect distillation seawater desalination process by supplementing preheated seawater via a water-water heat exchanger, and belongs to the technology field of multiple-effect distillation seawater desalination. The process comprises the steps of dividing an evaporator into a plurality of sections, leading out the final-effect condensed products fresh water and concentrated seawater in a high-temperature section, and supplementing preheated seawater via a water-water heat exchanger to reduce the degree of supercooling of the supplemented water entering into the high-temperature section of the evaporator, so as to solve the key restriction factor troubling the MED system design, and effectively improve the heat economical efficiency of the system. The final-effect secondary steam from the high-temperature section of the evaporator is introduced into an adjacent low temperature section of the evaporator as a heating steam, so as to recycle the latent heat of the steam. Therefore, the inventive process can adopt more effects, larger operating temperature range, and higher water generation ratio.

Description

technical field [0001] The invention belongs to the technical field of multiple-effect distillation (MED for short) desalination of seawater, and in particular relates to a multi-effect distillation seawater desalination process flow with segmental water-water preheating. It can effectively solve the adverse effects of the increase of seawater supercooling brought by the widely used MED system without steam preheater at present, expand the parameter selection range of the MED system, effectively improve the thermal economy of the MED system, and reduce the cost of fresh water . Background technique [0002] China is a country seriously short of water. For many years, the per capita fresh water resources have been less than 1 / 4 of the world average level, especially in coastal areas. According to the National Bureau of Statistics, the 11 coastal provinces, municipalities and districts in China feed 40% of the country's population and create 67% of the country's GDP with 15% ...

AI Technical Summary

Problems solved by technology

If the seawater peak temperature of the MED system (evaporation temperature of the first effect) and the effect number of the evaporator are increased, the influence of the subcooling degree will be significantly increased

However, increasing the seawater temperature range (the difference between the first effect and the final effect evaporation temperature) and the number of effects is an important step to increase the water production ratio of the system (the fresh water output per unit of input heating steam), and the increase of seawater subcooling limits the system. Improved thermodynamic performance

The products of the French SIDEM company are faced with such problems, and it is difficult to meet the higher requirements of users for the water production ratio of the system

[0009] In order to solve this problem, IDE Company in Israel mixed the concentrated seawater from several effect evaporators in the low temperature section. The problem of increasing the coldness, but it also brings about the problem of increasing the boiling point of seawater caused by the high seawater concentration in the high temperature section. The rising boiling point of seawater leads to a decrease in the effective heat transfer temperature difference of each effect. Device cost

Images