CN113233676A - Method for separating and recovering inorganic salt and water in high-salinity wastewater - Google Patents
Method for separating and recovering inorganic salt and water in high-salinity wastewater Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F2001/5218—Crystallization
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/06—Pressure conditions
- C02F2301/066—Overpressure, high pressure
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
Abstract
The invention relates to a method for separating and recovering inorganic salt and water in high-salinity wastewater, which utilizes relatively low atmospheric temperature and is assisted with a cooling system to cool the pretreated high-salinity wastewater to the temperature near 0 ℃, utilizes small molecular gas such as liquefied gas to perform hydration reaction with the high-salinity wastewater at low temperature and high pressure to generate ice-like gas hydrate crystals, concentrates the high-salinity wastewater and enables sodium sulfate in the wastewater to be separated out in the form of sodium sulfate decahydrate crystals, thereby finishing the purposes of concentrating the high-salinity wastewater, separating the sodium sulfate decahydrate crystals and recovering industrial water; the method utilizes gas hydration and inorganic salt sodium sulfate crystallization hydration at low temperature and high pressure, and simultaneously completes the concentration of the salt-containing wastewater and the separation of sodium sulfate in one set of equipment, thereby eliminating the problems of complex process flow, large equipment investment, high wastewater pretreatment requirement, high energy consumption, easy scaling and the like caused by membrane concentration and thermal evaporation concentration, and realizing the wastewater zero discharge treatment with low energy consumption, low investment and no secondary pollution.
Description
Technical Field
The invention relates to a method for separating and recovering inorganic salt and water in high-salinity wastewater.
Background
Wastewater generated in the processes of coal chemical industry, petrochemical industry and the like mainly comprises oily wastewater, sulfur-containing wastewater, salt-containing wastewater and high-concentration ammonia nitrogen wastewater, and if the wastewater is discharged into the environment, serious damage is generated to the water environment. The national environmental protection department released "environmental admission conditions (trial) for modern coal chemical engineering construction projects in 2015, wherein it is clearly specified that areas lacking a nano-wastewater area should take effective treatment measures for high-salinity wastewater, so that groundwater, atmosphere, soil and the like cannot be polluted. Because water resources and coal resources in China are distributed in a reverse direction, modern coal chemical engineering projects are mostly built in regions with water resource shortage and ecological weakness, such as inner Mongolia, Ningxia, Shaanxi, Xinjiang and the like, and the regions lack sewage receiving bodies and environmental capacity, so that zero emission treatment of high-salinity wastewater becomes a necessary choice. The traditional high-salinity wastewater zero-discharge technology considers little about the recycling of inorganic salt with lower value, and generally evaporates and crystallizes high-salinity wastewater into mixed salt. The mixed miscellaneous salt usually contains organic matters and even heavy metals, is difficult to treat as common solid waste, is treated as dangerous waste, and has large treatment capacity and high cost. If the water is stored in a heap, the water is easy to leach and seep out when meeting water, and the risk of secondary pollution exists.
With the continuous improvement of the industrial wastewater discharge standard in China, the realization of zero discharge of salt-containing wastewater becomes a necessary choice for modern enterprises. At present, the relatively advanced domestic salt-containing wastewater zero-discharge treatment technology generally comprises the steps of pretreatment, membrane concentration, evaporation, crystallization and the like. The pretreatment is to remove suspended matters, hardness, fluoride, heavy metals, silicon, COD and the like in the saline wastewater by adopting a conventional coagulating sedimentation, softening and hardness removal and filtering process so as to ensure the stable operation of a downstream process unit. The membrane concentration and evaporation steps are mainly to dehydrate and concentrate high-salinity wastewater with TDS about 10000mg/L to a saturated state for crystallization and salting out. In the two working procedures, evaporation concentration is a key link, but because the energy consumption is high, the equipment is complex and the investment is large, in order to reduce the waste water amount of thermal evaporation treatment, reduce the scale of evaporation equipment and save the energy consumption, a membrane concentration working section of low-concentration waste water is generally additionally arranged before a thermal evaporation working section. The addition of a membrane concentration working section needs to increase the investment of fixed assets, and in the concentration operation process, the pH, hardness, organic matters, colloidal suspended matters and the like of inlet water must be strictly controlled, so that the efficiency of the concentration membrane is reduced and even serious pollution is caused by carelessness, and the membrane which plays a key role can not be continuously used, thereby causing great loss. The membrane concentration operation process also requires a higher frequency of chemical cleaning, resulting in a reduction in net water production. The replacement frequency of the membrane is high, so that the operation cost of membrane concentration is high. Furthermore, membrane concentration has a limitation on the concentration of the raw wastewater, and high-salinity wastewater with too high TDS is not suitable for concentration by membrane concentration.
The zero-emission scheme of converting high-salinity wastewater into solid-state salt products and recycling water products by adopting a salt separation crystallization technology is a development direction for properly treating the high-salinity wastewater at the present stage. The salt-separating crystallization technology adopts a salt-separating crystallization process by a heat-separating method and a membrane salt-separating crystallization process. In both processes, high-salinity wastewater with TDS of 10000mg/L after pretreatment is concentrated to be saturated by inorganic salt by adopting an evaporation and thickening technology or a membrane concentration technology, and then the high-salinity wastewater is continuously evaporated or cold precipitated to crystallize and separate inorganic salt products. The high-salt wastewater with such low content is concentrated to a saturated state, and then the evaporation is continued to separate the inorganic salt in the solution by crystallization, so that the energy consumption required by the whole process is very large. In order to reduce the scale of an evaporative crystallization device and reduce the energy consumption of evaporation, the high-salinity wastewater treatment is generally a combined process of selective membrane concentration and evaporative crystallization. By adopting the combined process, although the energy consumption is low, the membrane concentration equipment and the membrane loss cost are required to be increased, and the requirements on pH, hardness, organic matters, colloidal suspended matters, TDS and the like of the feed wastewater by adding the membrane concentration are high, so that the salt separation and crystallization treatment is carried out on the high-salinity wastewater by adopting the combined process of the membrane concentration and the evaporative crystallization, and the operation cost is considerable.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art and provides a method for separating and recovering inorganic salt and water in high-salinity wastewater, which utilizes gas hydration reaction and inorganic salt hydration crystallization reaction to concentrate and crystallize high-salinity wastewater so as to reduce equipment investment, energy consumption and operation cost.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for separating and recovering inorganic salt and water in high-salinity wastewater comprises the following steps:
sending the pretreated high-salinity wastewater into a high-salinity wastewater pool, cooling to the ambient temperature, adjusting to the gas hydration reaction temperature through a wastewater temperature regulator, and spraying the wastewater from the top of a hydration crystallization reactor;
the raw material liquefied gas, unreacted liquefied gas returned from the top of the hydration crystallization reactor and liquefied gas resolved by the gas hydrate resolving tower are compressed to the pressure required by the hydration reaction by a liquefied gas compressor and sent to a liquefied gas temperature regulator, and the temperature of the liquefied gas is regulated to the temperature required by the hydration reaction;
the liquefied gas with the regulated temperature enters the hydration crystallization reactor from the bottom of the hydration crystallization reactor through a gas distributor and undergoes hydration reaction with high-salinity wastewater in the liquid phase of the hydration crystallization reactor; the density of the gas hydrate generated by the hydration reaction is less than that of the liquid-phase high-salinity wastewater, and the buoyancy overcomes the gravity and floats upwards together with the liquefied gas moving upwards to reach the liquid level of the liquid phase;
spraying falling high-salt wastewater from the top of the hydration crystallization reactor, carrying out hydration reaction with rising liquefied gas components in the falling process to generate gas hydration reaction crystals, allowing the generated gas hydrate crystals and unreacted high-salt wastewater to fall, allowing unreacted liquefied gas components to continuously rise, combining the unreacted gas hydrate crystals with liquefied gas components escaping from a gas hydrate crystallization liquid-solid separator to form unhydrated liquefied gas, and returning the unhydrated liquefied gas to a liquefied gas compressor for recycling;
after the high-salinity wastewater falling together with the gas hydrate crystals enters a high-salinity wastewater water phase, the high-salinity wastewater continues to perform hydration reaction with liquefied gas rising in a liquid phase, the generated gas hydrate crystals also float up to the liquid surface, and gas hydrate slurry formed by the gas hydrate crystals gathered on the liquid surface and part of the high-salinity wastewater is sent into a gas hydrate crystal liquid-solid separator from an outlet at the liquid surface for liquid-solid separation;
returning the gas escaped from the gas hydrate crystallization liquid-solid separator to a hydration crystallization reactor, returning the separated high-salt wastewater to the hydration crystallization reactor from the lower part, and feeding the separated gas hydrate crystals to a gas hydrate desorption tower;
the gas hydrate crystals entering the gas hydrate analysis tower fall on an inclined plate in the gas hydrate analysis tower and contact with warm water sprayed from the top to be decomposed into liquefied gas and water, the decomposed liquefied gas is returned to a compressor for recycling, most of the decomposed water is sent to an industrial water storage tank for standby, and a small part of the water is heated to be more than or equal to 20 ℃ by a liquid phase water heater and then sent to the gas hydrate analysis tower to analyze the gas hydrate;
the high-salt wastewater in the hydration crystallization reactor is concentrated while generating gas hydrate, when the high-salt wastewater is concentrated to be saturated by sodium sulfate, sodium sulfate molecules in the wastewater are combined with ten water molecules to generate sodium sulfate decahydrate crystals, the sodium sulfate decahydrate crystals sink under the action of gravity because the density of the sodium sulfate decahydrate crystals is higher than that of the high-salt wastewater, the high-salt wastewater is further concentrated while generating the sodium sulfate decahydrate, the concentration of sodium chloride in the high-salt wastewater at the lower part of the hydration crystallization reactor is controlled, when the concentration reaches or approaches 25 percent by weight, the concentrated high-salt wastewater at the bottom of the hydration crystallization reactor and the sodium sulfate decahydrate crystals deposited at the bottom of the hydration crystallization reactor form sodium sulfate decahydrate crystal slurry to be discharged together, and the sodium sulfate decahydrate crystal slurry is sent to a sodium sulfate decahydrate crystal centrifugal separator for liquid-solid separation;
dehydrating wet sodium sulfate decahydrate crystals separated from a sodium sulfate decahydrate crystal centrifugal separator to obtain anhydrous sodium sulfate products or weathering to obtain anhydrous sodium sulfate products, heating separated liquid high-salt wastewater through a heat exchanger, then feeding the liquid high-salt wastewater into an evaporative crystallizer for evaporative crystallization, feeding crystal slurry into a sodium chloride centrifugal separator for liquid-solid separation, drying the separated wet sodium chloride products to obtain refined salt products, and feeding the centrifugally separated liquid into a solidification process for dehydration and solidification to obtain miscellaneous salts according to the composition condition of the miscellaneous salts or directly feeding the miscellaneous salts back to a high-salt wastewater pool for recycling; the water vapor evaporated from the evaporation crystallizer is mixed with cold water pumped from an industrial water storage tank in a vapor condenser, condensed into liquid water, and discharged into the industrial water storage tank for later use, and non-condensable gas is discharged into the atmosphere from the top of the vapor condenser.
Preferably, in the evaporation crystallizer, the evaporation end point is controlled to be that the content of sodium sulfate in the liquid phase is not higher than 4.0 wt%, and after the control point is reached, the crystal slurry is sent to a sodium chloride centrifugal separator for liquid-solid separation.
Preferably, the temperature of the gas hydration reaction is 0.5-5 ℃, and the pressure is 2.5-6.0 MPa.
Preferably, in the hydration crystallization reactor, the concentration end point is controlled by the concentration of sodium chloride in the mother liquor, and the content of sodium chloride in the mother liquor is not more than 25 wt%.
Preferably, in the evaporative crystallizer, the end point of evaporative crystallization of sodium chloride is controlled by the concentration of sodium sulfate in mother liquor, and the percentage content of sodium sulfate in the mother liquor is not higher than 4.0%.
Preferably, the weight percentage of sodium sulfate in the residual mother liquor in the slurry discharged from the lower part of the hydrate crystallization reactor is 1.25-1.22%.
Preferably, the liquefied gas is a mixed gas of propane and/or butane and/or propylene.
Preferably, the density of the gas hydrate crystals formed by the components of the liquefied gasAre all less than 1.0g/cm3(ii) a The density of the high-salt wastewater in the hydration crystallization reactor is 1.043g/cm3～1.185g/cm3(ii) a The density of the sodium sulfate decahydrate crystal is 1.48g/cm3。
In the invention, the gas hydration reaction is a reaction for combining water in the high-salinity wastewater with the micromolecule nonpolar gas under the conditions of low temperature and high pressure to generate the ice-like gas hydrate crystals. The gas hydrate crystals generated in the reaction are separated out of the high-salinity wastewater body, and simultaneously, corresponding water molecules are carried out, so that the aim of concentrating the high-salinity wastewater is fulfilled.
The gas hydration reaction is required to be carried out under the conditions of low temperature and high pressure, and the two reaction conditions have a certain correlation. When the hydration reaction temperature is high, the reaction pressure required for generating the gas hydrate is high; when the hydration reaction temperature is low, the pressure required for the reaction to form the gas hydrate is low. The hydrate reaction belongs to an exothermic process, and the low temperature is favorable for forming a cage-shaped structure lattice by the combination of water molecules depending on hydrogen bonds, so that the growth of gas compounds can be promoted. However, the hydration temperature is lower than the freezing point, and special conditions such as icing exist, uncertainty exists, and energy consumption is high, so the suitable temperature range of the hydration reaction is 273.15K-278.85K, and the optimal temperature is 273.85K. Cooling the high salinity wastewater to the hydration reaction temperature also requires a higher consumption of cold energy. However, most of the production places of the coal chemical industry and petrochemical industry wastewater in China are in the northwest areas of Shanxi, Shaanxi and Nemont, and the annual average temperature of the areas is generally lower than 10 ℃ (for example, the annual average temperature of the areas is 5.3-8.7 ℃ in the Nemont Eldos city which is one of coal chemical industry project centralization areas), the average temperature of the areas is close to or even lower than 0 ℃ in two seasons of spring and winter, and thus, a natural temperature condition is provided for the generation of gas hydrate. The invention firstly utilizes the open high-salinity wastewater pool arranged in the open air to cool the high-salinity wastewater to the temperature close to the environmental temperature, and then adopts the cooling equipment to adjust the temperature of the high-salinity wastewater to the hydration reaction temperature, thereby greatly reducing the cold energy consumed by cooling the high-salinity wastewater.
The gas hydration reaction is a gas-liquid-solid three-phase reaction, and the gas pressure has a great influence on the reaction. The hydrate needs to reach a certain pressure in the process of generating so as to initiate the nucleation of the hydrate phase. The pressure required for the gas to hydrate at different temperatures varies. Table 1 below is the minimum pressure required for the main components in the liquefied gas to form hydrates at 0 c.
TABLE 1 minimum pressure required for hydrate formation at 0 deg.C for each component in liquefied gas
| Components | Generating pressure P/MPa | Boiling point or liquefaction temperature, DEG C |
| C3H6 | 0.48 | -47.4 |
| C3H8 | 0.17 | -42.09 |
| i-C4H10 | 0.11 | -11.7 |
Table 1 shows the minimum pressure required for gas hydrate formation at 0 deg.C, i.e. to hydrate a gas with water to form gas hydrate crystals, the system pressure must be kept higher than the pressure in the table. The difference between the system pressure and the minimum generated pressure is the overpressure, which is the driving force for hydrate growth. The greater the overpressure, the greater the hydrate growth rate. In addition, the initial formation pressure of the hydrate is also an important factor influencing the progress of the hydration reaction. The larger the initial pressure is, the larger the driving force for generating the hydrate is, the more orderly the arrangement of water molecules on the adsorption surface is, and the easier the nucleation and the growth of the gas hydrate are promoted.
The data in table 1 is the minimum pressure at which pure water hydrates with liquefied gas to form gas hydrates. The invention discusses the hydration reaction of water molecules in high-salinity wastewater and liquefied gas. The activity of the high-salinity wastewater with different concentrations is different, and the high-salinity wastewater with different concentrations is reduced in a plurality of curves along with the increase of the concentration. For example, pure water has an activity of 1.0 and a 26% sodium chloride solution has an activity of 0.72. Because the activity of the high-salt wastewater is lower than that of pure water, a larger driving pressure is required for the hydration reaction of water molecules in the wastewater and the liquefied gas, that is, the pressure required for the high-salt wastewater and the liquefied gas to generate gas hydrate is higher than the pressure required for the generation of hydrate by pure water at the same temperature.
The formation pressure in Table 1 is only the hydrate formation pressure at 0 ℃ for the hydration reaction, and if the hydration reaction temperature is higher than 0 ℃, the hydrate formation pressure is increased accordingly. The invention mainly depends on atmospheric cooling, and because of different seasons and different atmospheric environment temperatures, the reaction temperature in the hydration crystallization reactor needs to be adjusted according to the environmental temperature so as to fully utilize the climatic conditions and reduce the energy consumption for production. The hydration reaction temperature and the reaction pressure are a set of relevant data, and when the hydration reaction temperature is high, the required reaction pressure is also high; when the hydration reaction temperature is low, the required hydration reaction pressure is also low.
The research shows that the suitable hydration reaction pressure is 2.5 MPa-6.0 MPa, and the hydration reaction pressure is regulated and controlled according to the variation condition of the hydration reaction temperature in different seasons in the production process.
Analyzing the gas hydrate generation pressure in the table 1, the gas hydrate generation pressure of butane at 0 ℃ is only 0.11MPa, the butane and water in the high-salinity wastewater generate a hydration reaction, and the energy consumption required for compressing the gas is the lowest; propane has a slightly higher pressure at 0 ℃ to form gas hydrate, but the difference is not significant. The liquefied gas is a gas produced and recovered in refining of oil refining, and its main components are propane, butane, propylene and butylene, wherein the content of propane and butane is not less than 60%. The liquefied gas has wide source, low cost and easy obtaining, and the technology selects the liquefied gas as the hydration reaction gas.
The hydration reaction is exothermic and the exothermic heat of hydration must be removed to maintain a stable hydration reaction temperature in the hydration crystallization reactor. Because a shell and tube heat exchanger (gas hydrate crystals which are easily adhered to the wall of the heat exchanger) is not suitable for being configured in the hydration crystallization reactor to transfer heat, the temperature in the hydration crystallization reactor is kept stable by regulating and controlling the temperature of the blown liquefied gas in the reaction process. As can be seen from the boiling point or liquefaction temperature data of the components of the liquefied gas in table 1, the boiling points (liquefaction temperatures) of several gases are far from 0 ℃, so that the temperature of the liquefied gas is adjusted around 0 ℃ without causing any phase change in the liquefied gas. When the reaction temperature in the hydration crystallization reactor is increased due to the aggravation of hydration and heat release, the temperature of bubbling liquefied gas is reduced; when the reaction temperature in the hydration crystallization reactor is lowered due to the decrease of the hydration reaction speed, the temperature of the bubbling liquefied gas is appropriately increased, so that the temperature in the hydration crystallization reactor can be easily controlled to be stabilized within an optimum range.
The dehydration of inorganic salt by hydration crystallization is to concentrate the solution and separate the inorganic salt forming the compound with crystal water by utilizing the property that some inorganic salt molecules can combine with water molecules in saturated solution to form the compound with crystal water at a certain temperature. Anions in high-salt wastewater in coal chemical industry and the like are mainly chloride ions and sulfate ions, and cations are mainly sodium ions (originally existing divalent cations can be replaced into sodium ions in chemical softening or ion exchange and other processes after a series of pretreatment), so that salt components dissolved in the high-salt wastewater can be regarded as mainly sodium sulfate and sodium chloride. The solubility of sodium sulfate in water varies significantly with temperature, as shown in table 2 below.
TABLE 2 solubility of sodium sulfate in Water
| Temperature/. degree.C | 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
| Solubility (g/100 g water) | 4.9 | 9.1 | 19.5 | 40.8 | 48.8 | 46.2 | 45.3 | 44.3 | 43.7 | 42.7 | 42.5 |
As can be seen from table 2, the solubility of sodium sulfate in water is maximum at 40 ℃, and 48.8 grams of sodium sulfate per 100 grams of water are soluble. The solubility of sodium sulfate slowly decreased with increasing temperature to 42.5 g at 100 ℃. The solubility of sodium sulfate in water decreases rapidly from 40 c, and when the temperature is lowered to 0 c, the solubility of sodium sulfate in water is only 4.9 grams. Therefore, when the high-salinity wastewater is concentrated at low temperature, the sodium sulfate in the wastewater can quickly reach saturation, and is combined with water molecules in the wastewater to be separated out in the form of sodium sulfate decahydrate. Since ten molecules of water are bound when one molecule of sodium sulfate is precipitated, the high-salinity wastewater is further concentrated along with the precipitation and separation of sodium sulfate decahydrate.
TABLE 3 solubility of sodium chloride in Water
Table 3 shows the solubility of sodium chloride at different temperatures, and from the data in table 3, it can be seen that the solubility of sodium chloride in water increases with increasing temperature, but the increase is small, which indicates that the solubility of sodium chloride in water changes insignificantly with temperature. The solubility of sodium chloride in water at 0 ℃ was as high as 35.7 grams, and sodium chloride was not easily saturated at 0 ℃ compared to sodium sulfate, which had a solubility of only 4.9 grams, indicating that separation of sodium chloride and sodium sulfate at 0 ℃ is fully feasible using gas hydration and inorganic salt crystallization concentration.
NaCl-Na at 0 deg.C2SO4-H2In the O ternary water salt system, disalt (Na)2SO4·10H2O + NaCl) is composed of the following components in percentage by weight: NaCl: 25.61 percent; na (Na)2SO4：1.22％；H2O: 73.17 percent, and the specific gravity of the solution is 1.185. NaCl-Na at 100 deg.C2SO4-H2In the O ternary water salt system, disalt (Na)2SO4+ NaCl) saturated Point in weight percentComprises the following components: NaCl: 25.9 percent; na (Na)2SO4：4.4％；H2O: 69.7 percent. The specific gravity of the solution was 1.194. And controlling the reaction end point of separating the sodium sulfate and the sodium chloride according to the group of data, namely controlling the weight percentage content of the sodium chloride in the concentrated high-salinity wastewater to be not higher than 25%. The sodium chloride in the gas hydration crystallization reactor can be prevented from being separated out; and separating the slurry discharged from the lower part of the hydration crystallization separator, wherein the weight percentage of the sodium sulfate in the residual mother liquor is 1.25-1.22%, preheating the slurry to 100 ℃ for evaporation, separating out the sodium chloride in the wastewater, and controlling the percentage of the sodium sulfate in the mother liquor of the evaporation tank not to be higher than 4.0%, so that the sodium sulfate can be prevented from being separated out in the evaporation crystallizer. Two treatment methods are provided for separating mother liquor left after sodium chloride crystallization after evaporation is finished, and when the content of miscellaneous salt in the mother liquor is high, the mother liquor is dehydrated to generate mixed salt which is treated according to danger waste; and when the content of miscellaneous salt in the mother liquor is low, returning the mother liquor to the high-salinity wastewater pool for recycling.
The method comprises the steps of firstly, hydrating and concentrating the pretreated high-salinity wastewater by using gas until sodium sulfate is saturated, then combining the sodium sulfate with water to generate sodium sulfate decahydrate, crystallizing and separating out the further concentrated high-salinity wastewater, and separating out the sodium sulfate in the wastewater. The invention adopts a hydration crystallization reactor to finish the concentration of high-salinity wastewater and the separation of sodium sulfate decahydrate in one step. In the hydration crystallization reactor, besides high-salt waste water with a certain liquid level is injected into the hydration crystallization reactor before starting, waste water required by hydration reaction is continuously supplemented into the system during normal hydration and salt precipitation operation so as to maintain stable operation of the hydration reaction. The position for supplementing the wastewater into the hydration crystallization reactor is top spraying, so that the high-salinity wastewater can contact with the rising gas when falling in a drop shape, and the nucleation and crystallization of the gas hydrate are accelerated.
The liquefied gas blown into the hydration crystallization reactor is a mixed gas mainly composed of propane, butane, propylene and the like. After being blown in, the liquefied gas is firstly combined with water in the high-salinity wastewater to generate ice-like gas hydrate crystals and simultaneously concentrate the high-salinity wastewater. When the sodium sulfate in the high-salinity wastewater is saturated, one sodium sulfate molecule is combined with ten water molecules in the wastewater to generate sodium sulfate decahydrateAnd (4) crystal precipitation. Gas hydrate crystals and sodium sulfate decahydrate crystals are simultaneously generated in the hydration crystallization reactor. These two types of crystals can be separated according to their density differences. The density of gas hydrate crystals generated by each component in the liquefied gas is less than 1.0g/cm3(e.g., gas hydrate from propane has a density of 0.866g/cm3The density of butane-derived gas hydrate was 0.951g/cm3. ) (ii) a The density range of the high-salt wastewater in the hydration crystallization reactor is 1.043g/cm3～1.185g/cm3(ii) a The density of the sodium sulfate decahydrate crystal is 1.48g/cm3. Because the density of the sodium sulfate decahydrate crystals is greater than that of the high-salinity wastewater, the gravity of the sodium sulfate decahydrate crystals is greater than the buoyancy, and the crystals can settle downwards under the action of gravity and are converged to the bottom of the hydration crystallization reactor; the gas hydrate crystals float upwards under the action of buoyancy because the density of the gas hydrate crystals is less than that of the high-salinity wastewater, and finally the gas hydrate crystals are collected on the liquid surface of the hydration crystallization reactor, so that the two types of crystals are effectively separated.
Sodium sulfate decahydrate crystals discharged from the bottom of the gas hydration crystallization reactor and saturated mother liquor enter a solid-liquid separator together for liquid-solid separation, and the separated sodium sulfate decahydrate crystals are weathered (or evaporated) for dehydration to obtain an anhydrous sodium sulfate product. The separated liquid is sent to a vacuum evaporation process to recover sodium chloride. And (3) the mother liquor with high content of miscellaneous salts is dehydrated and solidified according to the content of other components in the mother liquor left after the sodium chloride is separated, and the mother liquor with low content is returned to the air cooling process for recycling.
Gas hydrate solid removed from the liquid surface of the gas hydration crystallization reactor is sent to a gas hydrate desorption tower after liquid carried by the gas hydrate solid is separated; the separated liquid is returned to the gas hydration crystallization reactor to continue to participate in the hydration reaction. Examples of the decomposition of the gas hydrate include a chemical method, a reduced pressure method, a hot water injection method, an electromagnetic heating method, and a microwave heating method. The method takes full consideration of various factors such as environmental protection, low investment, simple technology and the like, selects the injected hot water as the excitation mode of hydrate decomposition, and designs the reaction condition of the injected hot water for hydrolyzing, absorbing and decomposing the crystalline hydrate to be 20 ℃ and normal pressure. The equipment adopts an inclined plate tower, gas hydrate crystals are fed from the upper part of the inclined plate tower and are scattered on an inclined plate in the tower during desorption, hot water is sprayed onto the inclined plate from the top of the inclined plate tower, the temperature of the gas hydrate on the inclined plate is raised, and the gas hydrate is desorbed and decomposed under normal pressure. The resolved liquefied gas is discharged from the top of the inclined plate, and returns to the hydration crystallization reactor for recycling after being pressurized by the compressor; liquid water is discharged from the bottom of the inclined plate tower and is recycled as industrial water.
Compared with the prior art, the invention has the advantages that: the invention utilizes relatively low atmospheric temperature and is assisted with a cooling system to cool the pretreated high-salt wastewater to the temperature near 0 ℃, utilizes micromolecular gas such as liquefied gas to perform hydration reaction with the high-salt wastewater at low temperature and high pressure to generate ice-like gas hydrate crystals, concentrates the high-salt wastewater and separates out sodium sulfate in the wastewater in the form of sodium sulfate decahydrate crystals, thereby finishing the purposes of concentrating the high-salt wastewater, separating the sodium sulfate decahydrate crystals and recovering industrial water; the invention fully utilizes natural climate conditions, utilizes gas hydration and inorganic salt sodium sulfate crystallization hydration at low temperature and high pressure, and simultaneously completes the concentration of the salt-containing wastewater and the separation of sodium sulfate in a set of equipment, thereby eliminating the problems of complex process flow, more equipment, large investment, high wastewater pretreatment requirement, high energy consumption, easy scaling and the like caused by adopting membrane concentration and thermal evaporation concentration, and realizing the wastewater zero discharge treatment with low energy consumption, low investment and no secondary pollution.
Drawings
FIG. 1 is a schematic diagram of an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
As shown in fig. 1, the apparatus used in this embodiment includes a high-salt wastewater pool 1, a wastewater temperature controller 2, a hydration crystallization reactor 3, a gas hydrate crystallization liquid-solid separator 4, a sodium sulfate decahydrate crystallization centrifugal separator 5, a gas hydrate desorption tower 6, a liquid water heater 7, a heat exchanger 8, an evaporative crystallizer 9, a sodium chloride centrifugal separator 10, a steam condenser 11, an industrial water storage tank 12, a liquefied gas compressor 13, a liquefied gas temperature controller 14, a water pump 15, and a water pump 16. The specific system flow is consistent with the method described below.
The method for separating and recovering inorganic salt and water in the high-salinity wastewater comprises the following steps:
sending the pretreated high-salinity wastewater 1' into a high-salinity wastewater pool 1, cooling to the ambient temperature, adjusting to the gas hydration reaction temperature through a wastewater temperature regulator 2, and spraying and falling from the top of a hydration crystallization reactor 3;
the raw material liquefied gas 11', together with unreacted liquefied gas returned from the top of the hydration crystallization reactor 3 and liquefied gas resolved by the gas hydrate resolving tower 6 are compressed to the pressure required by the hydration reaction by a liquefied gas compressor 13, and sent to a liquefied gas temperature regulator 14 to regulate the temperature of the liquefied gas to the temperature required by the hydration reaction;
the liquefied gas 13' with the regulated temperature enters the hydration crystallization reactor 3 from the bottom of the hydration crystallization reactor 3 through a gas distributor and is subjected to hydration reaction with high-salinity wastewater in a liquid phase of the hydration crystallization reactor 3; the density of the gas hydrate generated by the hydration reaction is less than that of the liquid-phase high-salinity wastewater, and the buoyancy overcomes the gravity and floats upwards together with the liquefied gas moving upwards to reach the liquid level of the liquid phase;
the falling high-salinity wastewater is sprayed from the top of the hydration crystallization reactor 3 and is subjected to hydration reaction with the rising liquefied gas component in the falling process to generate gas hydration reaction crystals, the generated gas hydrate crystals fall together with the unreacted high-salinity wastewater, the unreacted liquefied gas component continues rising and is combined with the liquefied gas component 4 ' escaping from the gas hydrate crystal liquid-solid separator 4 to form the non-hydration reaction liquefied gas 10 ', and the non-hydration reaction liquefied gas 10 ' returns to the liquefied gas compressor 13 for recycling;
after entering a high-salinity wastewater water phase, the high-salinity wastewater falling together with the gas hydrate crystals continuously performs hydration reaction with liquefied gas rising in a liquid phase, the generated gas hydrate crystals also float up to the liquid surface, and gas hydrate slurry 3' formed by the gas hydrate crystals gathered on the liquid surface and part of the high-salinity wastewater is sent into a gas hydrate crystal liquid-solid separator 4 from an outlet at the liquid surface for liquid-solid separation;
returning the gas escaped from the gas hydrate crystallization liquid-solid separator 4 to the hydration crystallization reactor 3, returning the separated high-salt wastewater to the hydration crystallization reactor 3 from the lower part, and feeding the separated gas hydrate crystals 6' into a gas hydrate desorption tower 6;
the gas hydrate crystals entering the gas hydrate analysis tower 6 fall on an inclined plate in the gas hydrate analysis tower 6 to be contacted with warm water sprayed from the top, the crystals are decomposed into liquefied gas and water, the decomposed liquefied gas 9 'returns to a compressor for recycling, most of the decomposed water is sent to an industrial water storage tank for standby, and a small part of the water 7' is heated to be more than or equal to 20 ℃ by a liquid phase water heater 7 and then sent to the gas hydrate analysis tower 6 for analyzing the gas hydrate;
the high-salt wastewater in the hydration crystallization reactor 3 is concentrated while generating gas hydrate, when the high-salt wastewater is concentrated to be saturated by sodium sulfate, sodium sulfate molecules in the wastewater are combined with ten water molecules to generate sodium sulfate decahydrate crystals, the sodium sulfate decahydrate crystals sink under the action of gravity because the density of the sodium sulfate decahydrate crystals is higher than that of the high-salt wastewater, the high-salt wastewater is further concentrated while generating the sodium sulfate decahydrate, the concentration of sodium chloride in the high-salt wastewater at the lower part of the hydration crystallization reactor 3 is controlled, when the concentration reaches or approaches 25 percent by weight, the concentrated high-salt wastewater at the bottom of the hydration crystallization reactor 3 and the sodium sulfate decahydrate crystals deposited at the bottom of the hydration crystallization reactor 3 form sodium sulfate decahydrate crystal slurry 14' to be discharged together, and the sodium sulfate decahydrate crystal slurry is sent to a sodium sulfate decahydrate crystal centrifugal separator 5 for liquid-solid separation;
dehydrating wet sodium sulfate decahydrate crystals 16 'separated from a sodium sulfate decahydrate crystal centrifugal separator 5 to obtain anhydrous sodium sulfate products or weathering to obtain anhydrous sodium sulfate products, heating separated liquid high-salt wastewater 15' by a heat exchanger 8, then feeding the heated liquid high-salt wastewater into an evaporative crystallizer 9 for evaporative crystallization, feeding crystal slurry 17 'into a sodium chloride centrifugal separator 10 for liquid-solid separation, drying separated wet sodium chloride products 18' to obtain refined salt products, and feeding the centrifugally separated liquid into a solidification process for dehydration and solidification according to the composition condition of the miscellaneous salts to obtain miscellaneous salts or directly feeding the miscellaneous salts back into a high-salt wastewater pool 1 for recycling; the water vapor 21 ' evaporated from the evaporative crystallizer 9 is mixed with cold water pumped in the industrial water storage tank 12 in the steam condenser 11, condensed into liquid water 23 ' and discharged into the industrial water storage tank 12 for standby, and the non-condensable gas 22 ' is discharged into the atmosphere from the top of the steam condenser 11.
In this embodiment, in the evaporative crystallizer 9, the evaporation end point is controlled to be a point where the sodium sulfate content in the liquid phase is not higher than 4.0% wt, and after this control point is reached, the crystal slurry 17' is sent to a sodium chloride centrifuge 10 to be subjected to liquid-solid separation. The temperature of the gas hydration reaction is 0.5-5 ℃, and the pressure is 2.5-6.0 MPa. In the hydration crystallization reactor, the concentration end point is controlled by the concentration of sodium chloride in the mother liquor, and the content of the sodium chloride in the mother liquor is not more than 25 wt%. In the evaporative crystallizer, the end point of sodium chloride evaporative crystallization is controlled by the concentration of sodium sulfate in mother liquor, and the percentage content of sodium sulfate in the mother liquor is not higher than 4.0%. And separating the slurry discharged from the lower part of the hydration crystallization separator, wherein the weight percentage of sodium sulfate in the residual mother liquor is 1.25-1.22%. The liquefied gas is a mixed gas of propane and/or butane and/or propylene. The density of gas hydrate crystals generated by each component in the liquefied gas is less than 1.0g/cm3(ii) a The density of the high-salt wastewater in the hydration crystallization reactor is 1.043g/cm3～1.185g/cm3(ii) a The density of the sodium sulfate decahydrate crystal is 1.48g/cm3。
An example of the treatment of wastewater produced by a synthetic oil industry in the northwest region is provided below. After the wastewater is pretreated by chemical softening, membrane concentration and the like, the mass concentration of TDS is 88500mg/L, wherein Na+The mass concentration is 25620mg/L, Cl-The mass concentration is 13510.0mg/L, SO4 2-The mass concentration is 31520.0 mg/L. The wastewater is sent into a high-salinity wastewater tank for natural cooling, so that the wastewater is cooled to the ambient temperature.
Cooling the high-salinity wastewater in the wastewater tank to about 1.0 ℃ through a heat exchanger, then sending the high-salinity wastewater into the top of a hydration crystallization reactor to be uniformly sprayed and fall, carrying out hydration reaction with rising raw material liquefied gas at 1.0 ℃ and 3.5MPa, and leading generated gas hydrate and unreacted high-salinity wastewater to fall together and merge into a gas-liquid two-phase reaction zone;
the raw material liquefied gas is cooled to about 0 ℃ by a heat exchanger, compressed to about 3.5MPa by a compressor, sent into a gas distributor at the bottom of a hydration crystallization reactor, enters a gas-liquid phase reaction zone of the hydration crystallization reactor in a bubbling mode, and is subjected to hydration reaction with high-salinity wastewater in the gas-liquid phase reaction zone; gas hydrate generated in the gas-liquid two phases floats upwards due to the density of the gas-liquid two phases being less than that of the high-salinity wastewater, and together with the gas hydrate generated in the gas phase falling on the liquid surface, the gas hydrate generated in the gas-liquid two phases is removed out of the hydration crystallization reactor from the side surface close to the liquid surface, the gas hydrate generated in the gas-liquid two phases is sent to a gas hydrate analysis tower for analysis after centrifugal dehydration, the analyzed liquefied gas is recycled, and the analyzed water is sent to a gas chemical section to be used as industrial water;
the high-salt wastewater in the hydration crystallization reactor is continuously concentrated along with the continuous generation of the gas hydrate, when the high-salt wastewater is concentrated to be saturated by sodium sulfate, sodium sulfate molecules in the wastewater are combined with ten water molecules to generate sodium sulfate decahydrate crystals, and the sodium sulfate decahydrate crystals can sink to the bottom of the hydration crystallization reactor under the action of gravity because the density of the sodium sulfate decahydrate crystals is higher than that of the high-salt wastewater; removing sodium sulfate decahydrate crystal from the bottom, washing and dehydrating NaSO in the sodium sulfate decahydrate crystal4·10H2The mass fraction of O is more than or equal to 90 percent, and meets the industrial standard of sodium sulfate decahydrate (Q/1600BHG 073-2015);
while generating sodium sulfate decahydrate, the high-salinity wastewater is further concentrated, and the high-salinity wastewater in the hydration crystallization reactor is continuously concentrated along with the proceeding of the hydration reaction and the precipitation of the sodium sulfate decahydrate; sampling and analyzing at regular time, when the weight percentage of sodium chloride in the high-salt wastewater is close to 25 percent and the weight percentage of sodium sulfate is about 1.25 percent, removing the high-salt wastewater concentrated at the bottom of the hydration crystallization reactor together with sodium sulfate decahydrate crystals deposited at the bottom, sending the high-salt wastewater to a centrifugal separator for liquid-solid separation, and washing and dehydrating the separated sodium sulfate decahydrate crystals to obtain an industrial sodium sulfate decahydrate product; preheating, heating and evaporating the separated liquid high-salinity wastewater to saturate and separate out sodium chloride; sampling and analyzing at regular time, controlling the evaporation end point to be that the content of sodium sulfate in the liquid phase is lower than 4.0 wt%, sending the crystal slurry into a sodium chloride centrifugal separator for liquid-solid separation after the control point is reached, and drying and dehydrating the separated wet sodium chloride to obtain a sodium chloride product, wherein the mass fraction of NaCl is more than or equal to 97.5 percent and meets the standard of refined industrial salt (the standard of GBT 5462-2016 industrial salt);
mother liquor and washing liquor obtained by solid-liquid separation at each stage are returned to the high-salinity wastewater tank for recycling.
Claims (8)
1. A method for separating and recovering inorganic salt and water in high-salinity wastewater is characterized by comprising the following steps:
sending the pretreated high-salinity wastewater into a high-salinity wastewater pool (1), cooling to the ambient temperature, adjusting to the gas hydration reaction temperature through a wastewater temperature regulator (2), and spraying the wastewater from the top of a hydration crystallization reactor (3) to fall;
the raw material liquefied gas, unreacted liquefied gas returned from the top of the hydration crystallization reactor (3) and liquefied gas resolved by the gas hydrate resolving tower (6) are compressed to the pressure required by the hydration reaction by a liquefied gas compressor (13), and are sent to a liquefied gas temperature regulator (14) to regulate the temperature of the liquefied gas to the temperature required by the hydration reaction;
the liquefied gas with the regulated temperature enters the hydration crystallization reactor (3) from the bottom of the hydration crystallization reactor (3) through a gas distributor and is subjected to hydration reaction with high-salinity wastewater in the liquid phase of the hydration crystallization reactor (3); the density of the gas hydrate generated by the hydration reaction is less than that of the liquid-phase high-salinity wastewater, and the buoyancy overcomes the gravity and floats upwards together with the liquefied gas moving upwards to reach the liquid level of the liquid phase;
the falling high-salinity wastewater is sprayed from the top of the hydration crystallization reactor (3) and is subjected to hydration reaction with the rising liquefied gas component in the falling process to generate gas hydration reaction crystals, the generated gas hydrate crystals fall together with the unreacted high-salinity wastewater, the unreacted liquefied gas component continues rising, and the gas hydrate crystals and the liquefied gas component escaped from the gas hydrate crystal liquid-solid separator (4) form the unhydrated liquefied gas together, and the liquefied gas is returned to the liquefied gas compressor (13) for recycling;
after the high-salinity wastewater falling together with the gas hydrate crystals enters a high-salinity wastewater water phase, the high-salinity wastewater continues to perform hydration reaction with liquefied gas rising in a liquid phase, the generated gas hydrate crystals also float up to the liquid surface, and gas hydrate slurry formed by the gas hydrate crystals gathered on the liquid surface and part of the high-salinity wastewater is sent into a gas hydrate crystal liquid-solid separator (4) from an outlet at the liquid surface for liquid-solid separation;
returning the gas escaped from the gas hydrate crystallization liquid-solid separator (4) to the hydration crystallization reactor (3), returning the separated high-salt wastewater to the hydration crystallization reactor (3) from the lower part, and sending the separated gas hydrate crystals to a gas hydrate desorption tower (6);
the gas hydrate crystals entering the gas hydrate analysis tower (6) fall on an inclined plate in the gas hydrate analysis tower (6) and contact with warm water sprayed from the top to be decomposed into liquefied gas and water, the decomposed liquefied gas returns to a compressor for recycling, most of the decomposed water is sent to an industrial water storage tank for standby, and a small part of the water is heated to be more than or equal to 20 ℃ by a liquid phase water heater (7) and then sent to the gas hydrate analysis tower (6) for analyzing the gas hydrate;
the high-salt wastewater in the hydration crystallization reactor (3) is concentrated while generating gas hydrate, when the high-salt wastewater is concentrated to be saturated by sodium sulfate, sodium sulfate molecules in the wastewater are combined with ten water molecules to generate sodium sulfate decahydrate crystals, the sodium sulfate decahydrate crystals sink under the action of gravity because the density of the sodium sulfate decahydrate crystals is higher than that of the high-salt wastewater, the high-salt wastewater is further concentrated while generating sodium sulfate decahydrate, the concentration of sodium chloride in the high-salt wastewater at the lower part of the hydration crystallization reactor (3) is controlled, when the concentration reaches or approaches 25 percent by weight, the concentrated high-salt wastewater at the bottom of the hydration crystallization reactor (3) and the sodium sulfate decahydrate crystals deposited at the bottom of the hydration crystallization reactor (3) form sodium sulfate decahydrate crystal slurry to be discharged together, and the sodium sulfate decahydrate crystal slurry is sent to a sodium sulfate decahydrate crystal centrifugal separator (5) for liquid-solid separation;
dehydrating wet sodium sulfate decahydrate crystals separated from a sodium sulfate decahydrate crystal centrifugal separator (5) to obtain anhydrous sodium sulfate products or weathering to obtain anhydrous sodium sulfate products, heating separated liquid high-salt wastewater through a heat exchanger (8), then feeding the heated liquid high-salt wastewater into an evaporative crystallizer (9) for evaporative crystallization, feeding crystal slurry into a sodium chloride centrifugal separator (10) for liquid-solid separation, drying the separated wet sodium chloride products to obtain refined salt products, and feeding the centrifugally separated liquid to a solidification process for dehydration and solidification according to the composition condition of miscellaneous salts in the liquid high-salt wastewater to obtain miscellaneous salts or directly feeding the miscellaneous salts back to a high-salt wastewater pool (1) for recycling; the water vapor evaporated from the evaporative crystallizer (9) is mixed with cold water pumped in an industrial water storage tank (12) in a steam condenser (11), condensed into liquid water and discharged into the industrial water storage tank (12) for standby, and non-condensable gas is discharged into the atmosphere from the top of the steam condenser (11).
2. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: in the evaporation crystallizer (9), the evaporation end point is controlled to be that the content of sodium sulfate in the liquid phase is not higher than 4.0 percent wt, and after the control point is reached, the crystal slurry is sent into a sodium chloride centrifugal separator (10) for liquid-solid separation.
3. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: the temperature of the gas hydration reaction is 0.5-5 ℃, and the pressure is 2.5-6.0 MPa.
4. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: in the hydration crystallization reactor (3), the concentration end point is controlled by the concentration of sodium chloride in the mother liquor, and the content of sodium chloride in the mother liquor is not more than 25 wt%.
5. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: in the evaporative crystallizer (9), the end point of evaporative crystallization of sodium chloride is controlled by the concentration of sodium sulfate in the mother liquor.
6. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: and the weight percentage content of sodium sulfate in the residual mother liquor of the slurry discharged from the lower part of the hydrate crystallization reactor is 1.25-1.22%.
7. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: the liquefied gas is a mixed gas of propane and/or butane and/or propylene.
8. The method for separating and recovering inorganic salts and water in high-salinity wastewater according to claim 1, characterized in that: the density of gas hydrate crystals generated by each component in the liquefied gas is less than 1.0g/cm3(ii) a The density of the high-salt wastewater in the hydration crystallization reactor is 1.043g/cm3～1.185g/cm3(ii) a The density of the sodium sulfate decahydrate crystal is 1.48g/cm3。
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| CN113663356A (en) * | 2021-08-23 | 2021-11-19 | 广西埃索凯新材料科技有限公司 | Crystallization impurity removal monitoring system applied to manganese sulfate production |
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