Evaporation crystallization method for treating salt-containing wastewater and device for implementing method

Abstract

The invention discloses an evaporation crystallization method for treating salt-containing wastewater. The method comprises the following steps: allowing the salt-containing wastewater to sequentially pass through an electromagnetic wave emitting device and a primary preheater, and then feeding the wastewater into a two-effect falling film evaporator for evaporation; feeding the primary concentrated liquid after evaporation in the two-effect falling film evaporator into a gas-liquid separator for separation, and then feeding the primary concentrated liquid after the separation of the gas-liquid separator into a one-effect falling film evaporator for evaporation crystallization, thus obtaining a secondary concentrated liquid in a supersaturated state; feeding the secondary concentrated liquid into a crystallization separator for crystallization, and then feeding the liquid obtained in the crystallization separator into the one-effect falling film evaporator for circulating evaporation, and discharging crystals obtained in the crystallization separator through a solid discharging device. According to the invention, the evaporation crystallization process of high-concentration brine is divided into an unsaturated evaporation process and a supersaturated crystallization process, thereby ensuring that a part of water is evaporated out firstly from the material at a relatively low concentration and reducing the influences of reduced heat transfer temperature difference in the evaporator, reduction of evaporation effect and accordingly energy consumption increase due to the elevation of boiling point of the supersaturated brine.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of MVR evaporative crystallization system for recovery and treatment of industrial waste water, and in particular relates to an evaporative crystallization method for treating salty waste water and a device for realizing the method. [0003] Background technique: [0004] In the resource utilization process of waste water produced in food, chemical and pharmaceutical fields, the MVR evaporation method is widely used at present. This method has the advantages of large processing capacity, high efficiency, and wide application range, but the evaporation temperature is low and heat exchange The small temperature difference is also a notable feature. However, the boiling point of high-concentration brine is 8°C-10°C higher than that of tap water in a supersaturated state. When the conventional method is used for single-effect evaporation, the material is in a saturated state for a long time. decrease, co...

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Problems solved by technology

However, the boiling point of high-concentration brine is 8°C-10°C higher than that of tap water in a supersaturated state. When the conventional method is used for single-effect evaporation, the material is in a saturated state for a long time. decrease, corresponding to the increase in system energy consumption, and at the same time, the evaporation of high-concentration brine in the traditional MVR system will cause problems such as easy scaling and frequent shutdowns for maintenance. Research on Scale Resistance

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