A kind of salt making method and salt making system

Abstract

The invention relates to the field of water treatment, and discloses a salt production method and a salt production system. The method comprises: (1) adding dianion salt crystal seeds to raw water to obtain a buffer solution; (2) cooling the buffer solution; 3) The cooled buffer solution is subjected to crystallization and separation treatment to obtain a divalent anion salt crystalline salt; the raw material water contains a divalent anion salt and an optional monovalent anion salt, and the mass concentration of the divalent anion salt in the raw material water is not less than the step ( 2) Saturation of the dianion salt at medium cooling temperature, the solubility of the dianion salt at 0-32.4°C decreases as the temperature decreases and the average solubility of the dianion salt in the range of 0-32.4°C decreases The rate is greater than 0.03g / °C. The method of the present invention can effectively slow down the fouling phenomenon in the tube side of the heat exchanger or on the wall of the heat exchanger during the cooling process of the high-concentration brine, and can obtain crystalline salt with high purity and large average particle size, which is beneficial to subsequent separation .

Description

technical field

[0001] The invention relates to the field of water treatment, in particular to a salt production method and a salt production system capable of effectively slowing down heat exchanger fouling. Background technique

[0002] With the continuous improvement of environmental protection requirements, contradictions such as insufficient water resources and limited environmental capacity have become increasingly prominent. In the production processes of petrochemical, coal chemical, electric power, steel and seawater desalination, a large amount of salty wastewater will be produced. In order to reduce the amount of external drainage and improve the efficiency of water use, currently salty wastewater is generally treated by reverse osmosis-based membrane method and then reused, which improves the efficiency of water use to a certain extent. Where zero liquid discharge is required, the concentrated reverse osmosis water is further processed by evaporation and crystal...

Examples

Embodiment 1

[0055] Synthetic brine-containing simulated raw material water is prepared in a buffer tank, wherein the brine is a mixed solution of sodium sulfate and sodium chloride at 10°C (the temperature of the brine is determined by preparing the brine and the crystallization effluent obtained from the subsequent crystallization separation process) heat exchange treatment to control), the massfraction of sodium sulfate is 8%, and the massfraction of sodium chloride is 2%. According to the Phreeqc simulation, the temperature when the sodium sulfate in the brine is saturated is 10°C, so the brine is a saturated solution of sodium sulfate at this time, and there is no salt precipitation. Add solid sodium sulfate to the brine in a buffer tank to obtain a buffer solution, wherein, based on 1L of buffer solution, the amount of sodium sulfate seed crystals added is 1000mg, and the buffer solution is pumped at a flow rate of 3m / s while stirring. Pour into a coil-type stainless steel heat excha...

Embodiment 2

[0057] Synthetic brine-containing simulated raw material water was prepared in a buffer tank, wherein the brine was a mixed solution of sodium sulfate and sodium chloride at 25°C, the mass fraction of sodium sulfate was 10%, and the mass fraction of sodium chloride was 2%. According to the Phreeqc simulation, there is no salt precipitation in the brine at 25°C. Add the solid-liquid mixed saturated solution of the sodium sulfate crystalline salt that subsequent crystallization separation process obtains to this containing brine in buffer tank, obtain buffer solution, wherein, in 1L buffer solution, the addition amount of sodium sulfate seed crystal is 800mg, while While stirring, pump the buffer solution at a flow rate of 4 m / s into a coiled stainless steel heat exchanger with a pipe diameter of 6 mm for cooling. The refrigerant in the heat exchanger is 20% by weight ethylene glycol solution at 0°C. After the buffer solution is cooled by a heat exchanger, the temperature drops ...

Embodiment 3

[0059] Synthetic brine-containing simulated raw material water was prepared in a buffer tank, wherein the brine was a sodium sulfate solution at 20° C., and the mass fraction of sodium sulfate was 9%. According to the Phreeqc simulation, there is no salt precipitation in the brine at 20°C. Add solid sodium sulfate to the brine in a buffer tank to obtain a buffer solution, wherein, based on 1L of buffer solution, the amount of sodium sulfate seed crystals added is 1500 mg, and the buffer solution is pumped at a flow rate of 5 m / s while stirring. Pour into a coil-type stainless steel heat exchanger with a pipe diameter of 6mm for cooling, and the refrigerant of the heat exchanger is frozen brine at -2°C. After the buffer solution is cooled by a heat exchanger, the temperature drops to 2° C. (at this temperature, the degree of saturation of sodium sulfate is 6% by weight), and the cooled buffer solution enters the crystallization tank for crystallization separation. The residence...

technical field

[0001] The invention relates to the field of water treatment, in particular to a salt production method and a salt production system capable of effectively slowing down heat exchanger fouling. Background technique

[0002] With the continuous improvement of environmental protection requirements, contradictions such as insufficient water resources and limited environmental capacity have become increasingly prominent. In the production processes of petrochemical, coal chemical, electric power, steel and seawater desalination, a large amount of salty wastewater will be produced. In order to reduce the amount of external drainage and improve the efficiency of water use, currently salty wastewater is generally treated by reverse osmosis-based membrane method and then reused, which improves the efficiency of water use to a certain extent. Where zero liquid discharge is required, the concentrated reverse osmosis water is further processed by evaporation and crystal...

Examples

Embodiment 1

[0055] Synthetic brine-containing simulated raw material water is prepared in a buffer tank, wherein the brine is a mixed solution of sodium sulfate and sodium chloride at 10°C (the temperature of the brine is determined by preparing the brine and the crystallization effluent obtained from the subsequent crystallization separation process) heat exchange treatment to control), the massfraction of sodium sulfate is 8%, and the massfraction of sodium chloride is 2%. According to the Phreeqc simulation, the temperature when the sodium sulfate in the brine is saturated is 10°C, so the brine is a saturated solution of sodium sulfate at this time, and there is no salt precipitation. Add solid sodium sulfate to the brine in a buffer tank to obtain a buffer solution, wherein, based on 1L of buffer solution, the amount of sodium sulfate seed crystals added is 1000mg, and the buffer solution is pumped at a flow rate of 3m / s while stirring. Pour into a coil-type stainless steel heat excha...

Embodiment 2

[0057] Synthetic brine-containing simulated raw material water was prepared in a buffer tank, wherein the brine was a mixed solution of sodium sulfate and sodium chloride at 25°C, the mass fraction of sodium sulfate was 10%, and the mass fraction of sodium chloride was 2%. According to the Phreeqc simulation, there is no salt precipitation in the brine at 25°C. Add the solid-liquid mixed saturated solution of the sodium sulfate crystalline salt that subsequent crystallization separation process obtains to this containing brine in buffer tank, obtain buffer solution, wherein, in 1L buffer solution, the addition amount of sodium sulfate seed crystal is 800mg, while While stirring, pump the buffer solution at a flow rate of 4 m / s into a coiled stainless steel heat exchanger with a pipe diameter of 6 mm for cooling. The refrigerant in the heat exchanger is 20% by weight ethylene glycol solution at 0°C. After the buffer solution is cooled by a heat exchanger, the temperature drops ...

Embodiment 3

[0059] Synthetic brine-containing simulated raw material water was prepared in a buffer tank, wherein the brine was a sodium sulfate solution at 20° C., and the mass fraction of sodium sulfate was 9%. According to the Phreeqc simulation, there is no salt precipitation in the brine at 20°C. Add solid sodium sulfate to the brine in a buffer tank to obtain a buffer solution, wherein, based on 1L of buffer solution, the amount of sodium sulfate seed crystals added is 1500 mg, and the buffer solution is pumped at a flow rate of 5 m / s while stirring. Pour into a coil-type stainless steel heat exchanger with a pipe diameter of 6mm for cooling, and the refrigerant of the heat exchanger is frozen brine at -2°C. After the buffer solution is cooled by a heat exchanger, the temperature drops to 2° C. (at this temperature, the degree of saturation of sodium sulfate is 6% by weight), and the cooled buffer solution enters the crystallization tank for crystallization separation. The residence...

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