CN103058303B - Method for separating inorganic salt substances from high-salt liquid waste - Google Patents

Abstract

A method for separating and treating inorganic salt substances in high-salt waste liquid belongs to the field of environmental protection of waste water treatment. The system includes the following equipment in turn: evaporator, vaporizer, thin-film evaporator, cooling screw pusher; use a pump to send high-salt waste liquid from the lower end of the evaporator for heating, and then enter the vaporizer through the pipeline for vaporization and flash separation; The steam is condensed from the upper outlet of the evaporator; the high-salt waste liquid entering the evaporator is evaporated, flashed and separated to obtain a concentrated liquid; the concentrated liquid is circulated through the pipeline from the lower end of the evaporator to the discharge port and then enters from the feed port at the lower end of the evaporator , mixed with high-salt waste water, heated again, vaporized, evaporated, and further concentrated to obtain a concentrated liquid, which enters a thin-film evaporator through a pipeline from the lower end of the vaporizer to obtain a salt slurry; the salt slurry enters a cooling screw feeder to obtain salt mud, thereby Realize the effective separation of inorganic salts. The method has high efficiency and low energy consumption.

Description

A method for separating and treating inorganic salts in high-salt waste liquid

technical field

The invention relates to the separation and treatment of inorganic salts in high-salt waste liquid, and belongs to the field of environmental protection of waste water treatment.

Background technique

High-salt waste liquid refers to waste water containing organic matter and at least a mass fraction of total dissolved solids TDS greater than twice the concentration of seawater, that is, more than 6%. Usually this type of wastewater contains not only a large amount of inorganic salts, such as Cl ^- , Na ⁺ , SO ₄ ^2- , Ca ²⁺ , but also organic pollutants. Main sources: (1) Chemical production: Incomplete chemical reaction or chemical reaction by-products, especially pesticides, dyes and other chemical products, produce a large amount of toxic wastewater with high COD and high salt. (2) Produced by waste water treatment and recycling. In the wastewater treatment process, the addition of water treatment agents, acids and alkalis will increase the salt content of the wastewater itself; after the wastewater is treated, the concentrated solution with high salinity will be produced during the recycling process of COD up to standard water. All of these are referred to as high salinity effluents. This kind of high-salt waste liquid is not only more polluting than ordinary sewage, but also salinizes the soil and forms saline-alkali land, thereby destroying the vegetation of the soil.

The high-salt and high-COD wastewater produced in the chemical production process of pesticides and dyes is usually treated by direct incineration. This method is to spray waste water into a high-temperature combustion furnace in the form of mist, so that the water mist is completely vaporized, and the organic matter in the waste water is oxidized in the furnace, and decomposed into carbon dioxide, water and inorganic salt ash, which are complete combustion products. It is generally believed that incineration is more economical and reasonable than other methods for high-salt waste liquid with COD ≥ 100,000 mg/L and calorific value ≥ 2500 kcal/kg or saline organic waste liquid with organic component mass fraction ≥ 10%. Obviously, it is very uneconomical to directly incinerate other high-salt wastewater. After all, incineration consumes a lot of energy and easily produces flue gas, which pollutes the atmosphere.

Usually, the principle of evaporation is used to evaporate and concentrate high-salt wastewater to obtain high-salt concentrated waste liquid. Finally, the deep cooling technology is adopted to separate the inorganic salts through the cooling and crystallization process. At the same time, reclaimed water and a concentrate with a still high salt content are obtained. Among them, the concentrated solution is returned to the previous process for evaporation, concentration, cooling and crystallization to realize further separation of inorganic salts. However, since most of the salts in wastewater are soluble chlorides, the solubility is very large and is less affected by temperature. Therefore, the efficiency of separating inorganic salts from concentrated saline waste liquid by cooling crystallization technology is very low. In particular, the crystallization mother liquor is returned to the previous process for reheating and evaporation. Cause the whole technological process to be long, energy consumption is high. Therefore, it is urgent to develop a high-efficiency, low-energy-consumption separation method for inorganic salt substances in high-salt waste liquid.

Contents of the invention

The purpose of the invention is to develop a method for separating inorganic salt substances in high-salt waste liquid with high efficiency and low energy consumption.

A method for separating and treating inorganic salt substances in high-salt waste liquid, characterized in that:

The applied system includes the following equipment in order: evaporator, evaporator, thin film evaporator, cooling screw pusher;

Use a pump to send high-salt waste liquid from the lower end of the evaporator for heating, and control the outlet temperature of the evaporator to 105-120°C. The heated high-salt waste liquid enters the vaporizer from the upper end of the evaporator through a pipeline for vaporization and flash separation ; Among them, 60-70% of the water turns into water vapor, and enters the condenser from the upper outlet of the vaporizer to condense and become recycled water;

The high-salt waste liquid entering the vaporizer is vaporized and flashed and separated, leaving 30-40% of the concentrated liquid; the concentrated liquid is circulated through the pipeline from the lower end of the vaporizer to the outlet and then enters from the feed port at the lower end of the evaporator. Mix with high-salt waste water, heat again, vaporize, evaporate, and further concentrate to obtain a concentrated solution, so that the specific gravity of the concentrated solution reaches 1.4 to 1.6;

The concentrated liquid enters the upper end of the thin-film evaporator from the lower end of the vaporizer through the pipeline, and performs thin-film evaporation to evaporate 70-80% of the water in the concentrated liquid. The temperature of the water vapor outlet is controlled at 100-110°C, leaving 20-30% of the salt slurry; The salt slurry enters the cooling screw feeder, and is cooled during the screw conveying process to reduce its temperature to 30-40°C. Finally, it is discharged from the cooling screw feeder to obtain salt mud, thereby realizing the separation of inorganic salts. effective separation;

In the whole process flow, the induced draft fan is used to maintain the system to operate and run under the micro-negative pressure state of 85-95kpa.

Key equipment and process control parameters

1. Thin film evaporator

(1) The thin film evaporator is made of 316L stainless steel, titanium alloy or anti-corrosion and high-temperature resistant graphite material. It is a vertical device and is heated by steam. The height-to-diameter ratio of the thin-film evaporator is greater than 2. The upper end head is arranged with a concentrated liquid inlet, a water vapor outlet and a clean water flushing port, and the lower end head is arranged with a salt slurry outlet. A rotating shaft with a scraper is installed inside, and a liquid receiving plate for concentrated liquid is installed on the upper part of the rotating shaft. The concentrated liquid first enters the liquid receiving pan from the feed inlet of the upper end head. The liquid receiving plate rotates together with the rotating shaft, and its rotation speed is controlled at 45-60 rpm. The concentrated liquid is sprinkled on the inner wall of the thin film evaporator and evaporated by heating. During this process, the concentrated liquid gradually turns into a salt slurry as the water evaporates, and is discharged from the bottom of the thin-film evaporator under the action of the scraper on the rotating shaft. Wherein, the water vapor is discharged from the water vapor outlet at the upper end of the surface evaporator. During this period, control the water vapor outlet temperature to 100-110°C.

(2) Key process control parameters

1) The outlet temperature of the evaporator is controlled at 105-120°C; the evaporation rate of the concentrated liquid entering the evaporator is 60-70%;

2) The salt slurry is evaporated in a thin film evaporator, the temperature of the water vapor outlet is controlled at 100-110°C, and the water in the salt slurry evaporates by 70-80%;

3) The specific gravity of the concentrated liquid entering the thin film evaporator at the lower end of the vaporizer is controlled at 1.4 to 1.6;

4) Use the induced draft fan to maintain the operation and operation of the system in the state of slight negative pressure.

The invention utilizes thin-film evaporation equipment and adopts a flash evaporation-thin-film evaporation-salt slurry cooling process technology to realize the separation and treatment method of inorganic salts in high-salt waste liquid. The method has high efficiency and low energy consumption.

Detailed ways

Example 1

A high-salt wastewater produced by pesticide production, with a salt content of 10-15% and a COD of 300-500mg/L. The wastewater is pumped from the lower end of the evaporator for heating, and the outlet temperature of the evaporator is controlled to 115°C. The heated high-salt wastewater enters the vaporizer from the upper end of the evaporator through a pipeline for vaporization and flash separation. Among them, 70% of the water turns into water vapor, and exits from the upper end of the evaporator into the condenser for condensation to become recycled water.

The high-salt waste liquid entering the vaporizer is vaporized and flash-separated, leaving 30% of the concentrated liquid. The concentrated liquid enters through the pipeline from the outlet of the lower end of the evaporator to the feed port at the lower end of the evaporator, mixes with the high-salt waste water, heats again, vaporizes, evaporates, and further concentrates so that the specific gravity of the concentrated liquid reaches 1.3, and then puts The concentrated liquid enters the upper end of the thin-film evaporator from the lower end of the vaporizer through the pipeline, and then evaporates again. The temperature of the water vapor outlet is controlled at 100°C, so that 80% of the water in the concentrated liquid is evaporated again, leaving 20% of the salt slurry. The salt slurry enters the cooling screw feeder, and is cooled during the screw conveying process to reduce its temperature to 30°C. Finally, it is discharged from the cooling screw feeder to obtain salt mud.

Under the action of the cooling screw pusher, the salt mud is sent from the upper end of the rotary incinerator for incineration. The incineration temperature is controlled at 450°C, and the residence incineration time is 3 minutes. Finally, the high-temperature solid salt slag is discharged from the lower end of the rotary incinerator under the action of rotation. During the incineration process, the high-temperature flue gas produced is washed, cooled, and purified before being discharged.

In the whole process flow, the induced draft fan is used to maintain the system to operate and run under the state of slight negative pressure.

Example 2

The wastewater of a wastewater treatment plant has been treated, and the COD is less than 100mg/L. In order to achieve "zero" discharge, the qualified discharge water is treated with reverse osmosis membrane, and 80% of the water is recovered for recycling. The remaining 20% of the concentrated wastewater is evaporated through multi-effect flash evaporation and 80% of the water is recovered. The remaining 20% concentrated waste. The waste liquid is sent from the lower end of the evaporator to be heated by a pump, and the outlet temperature of the evaporator is controlled to 105°C. The heated concentrated waste liquid enters the vaporizer from the upper end of the evaporator through a pipeline for vaporization and flash separation. Among them, 60% of the water turns into water vapor, and exits from the upper end of the vaporizer into the condenser for condensation to become recycled water.

The high-salt waste liquid entering the vaporizer is vaporized and flash-separated, leaving 40% of the concentrated liquid. The concentrated liquid enters through the pipeline from the lower end of the evaporator to the lower end of the evaporator, and then enters from the lower end of the evaporator, mixes with high-salt waste water, heats again, vaporizes, evaporates, and further concentrates to make the specific gravity of the concentrated liquid reach 1.3. The concentrated liquid enters the upper end of the thin-film evaporator from the lower end of the evaporator through the pipeline to perform thin-film evaporation. The temperature of the water vapor outlet is controlled at 110°C, so that 70% of the water in the concentrated liquid is evaporated again, leaving 30% of the salt slurry. The salt slurry enters the cooling screw feeder, and is cooled during the screw conveying process to reduce its temperature to 30°C. Finally, it is discharged from the cooling screw feeder to obtain salt mud, which realizes the effective separation of inorganic salts.

Claims (1)

1. the method for separating and processing of inorganic salt material in a high salt bearing liquid wastes is characterized in that:

The system of application comprises following equipment successively: vaporizer, vaporizer, thin-film evaporator, cooling spiral pushing device;

Use pump that high salt bearing liquid wastes is sent into and heated from the vaporizer lower end, control 105～120 ℃ of evaporator outlet temperatures; Heated high salt bearing liquid wastes enters vaporizer from the vaporizer upper end by pipeline, is vaporized, flash separation; Wherein, 60～70% water becomes water vapour, and is exported out by the vaporizer upper end and enter condenser and carry out condensation, becomes recycle-water;

Enter the high salt bearing liquid wastes in vaporizer, after overflash, flash separation, remaining 30～40% concentrated liquid; Concentrated liquid enters from the opening for feed of vaporizer lower end from vaporizer lower end circulation discharge port again by pipeline, mixes again with high slat-containing wastewater and heats, vaporizes, evaporates, and further concentrates and obtains concentrated solution, makes the proportion of concentrated solution reach 1.4～1.6;

This concentrated solution enters the thin-film evaporator upper end by pipeline from the vaporizer lower end, carries out thin film evaporation, makes the water evaporation 70～80% in concentrated solution, and the steam temperature out is controlled at 100～110 ℃, the salt slurry of remaining 20-30%; This salt slurry enters the cooling spiral pushing device, cooling by obtaining in the helical feed process, makes its temperature be reduced to 30～40 ℃; Finally, by the cooling spiral pushing device, discharged, obtain salt slurry, thereby realize effective separation of inorganic salts material;

In whole technical process, all adopt induced draft fan to maintain operation under the micro-vacuum state of system in 85～95kpa, operation.

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