阅读说明：本技术 利用气体水合脱水生产精盐制备方法 (Preparation method for producing refined salt by gas hydration and dehydration ) 是由 李寒羿 杨相益 李刚 王英杰 陈潮清 于 2021-10-28 设计创作，主要内容包括：一种利用气体水合脱水生产精盐制备方法,将卤水送到水合反应器中与液化气这样的小分子气体发生水合反应,生成似冰状气体水合物晶体,并析出氯化钠结晶。气体水合物结晶在解析塔中解析,析出的液化气循环利用,析出的水可用于溶盐制卤；析出的氯化钠结晶经离心脱水、干燥得产品精制盐。与现有技术相比,本发明的优点在于：无需真空蒸发操作,能耗低；在一套设备内完成水合物生成和食盐析出,工艺流程简单,设备要求低,固定资产投资少。(A process for preparing refined salt by gas hydration and dehydration includes such steps as delivering bittern to hydration reactor, hydrating with liquefied gas to generate ice-like gas hydrate crystal, and separating out sodium chloride crystal. The gas hydrate crystals are resolved in a resolving tower, the resolved liquefied gas is recycled, and the resolved water can be used for dissolving salt to prepare brine; the separated sodium chloride crystal is centrifugally dehydrated and dried to obtain the refined salt product. Compared with the prior art, the invention has the advantages that: vacuum evaporation operation is not needed, and energy consumption is low; the hydrate generation and the salt precipitation are completed in a set of equipment, the process flow is simple, the equipment requirement is low, and the investment of fixed assets is low.)

1. A preparation method for producing refined salt by utilizing gas hydration dehydration is characterized by relating to a hydration reactor (1), a crystallization liquid-solid separator (2), a crystallization liquid-solid separation and analysis tower (3), a heater (4), a centrifuge (8), a gas compressor (5), a first temperature regulator (6), a second temperature regulator (7), a liquefied gas inlet pipe (1b) and a brine pipeline (1a), wherein the brine pipeline (1a) enters the hydration reactor (1) through the first temperature regulator (6), the liquefied gas inlet pipe (1b) enters the hydration reactor (1) through the second temperature regulator (7), the gas outlet end at the top of the hydration reactor (1) is connected with the gas inlet of the gas compressor (5), the bottom of the hydration reactor is provided with a first slurry outlet, the middle part of the hydration reactor is provided with a second slurry outlet, the upper part of the hydration reactor is provided with a brine inlet, the lower part of the crystallization liquid-solid separation and analysis tower is provided with a liquefied gas inlet, the crystallization liquid separator is provided with a top gas outlet connected with the liquefied gas inlet of the hydration reactor (1), a bottom inlet connected with a brine outlet of the hydration reactor (1), a feed inlet connected with a second slurry outlet of the hydration reactor and a discharge outlet in the middle, the crystallization liquid-solid separation and analysis tower (3) is provided with a feed inlet connected with the discharge outlet of the crystallization liquid separator and a top gas outlet connected with a gas inlet of a gas compressor (5), a spray (41) is arranged in the crystallization liquid-solid separation and analysis tower (3), and the bottom of the crystallization liquid-solid separation and analysis tower is provided with a pipeline entering a heater (4); the heater (4) heats the water in the spray (41), the feed end of the centrifuge (8) is connected with the first slurry outlet of the hydration reactor (1) and is provided with a first discharge end which is returned to the brine pipeline and a second discharge end which can produce wet product salt;

saturated brine is sent into a first temperature regulator (6) through a brine pipeline (1a), the temperature of the brine is regulated to a required temperature according to the change condition of the hydration reaction temperature in a hydration reactor (1), and the saturated brine is sent into the hydration reactor (1) through a brine inlet; pressurizing the liquefied gas in a gas compressor (5) to the pressure required by the hydration reaction, then sending the liquefied gas into a second temperature regulator (7) to regulate and control the temperature required by the hydration reaction, and blowing the liquefied gas from the bottom of the hydration reactor (1); in the hydration reactor (1), the liquefied gas and the water component in the saturated brine are subjected to hydration reaction to generate gas hydrate crystals; the dissolved salt corresponding to the consumed water amount is separated out by sodium chloride crystallization; sending the crystal salt slurry discharged from the bottom of the hydration reactor (1) into a centrifugal separator for separation and dehydration, and obtaining wet product salt after centrifugal dehydration for preparing refined salt; saturated brine obtained by centrifugal dehydration and new raw material saturated brine are mixed and then sent into a first temperature regulator (6) for cyclic utilization; gas hydrate crystal slurry discharged from the liquid surface enters a crystal liquid-solid separator (2), unreacted liquefied gas in the crystal liquid-solid separator (2) returns to the hydration reactor (1) from the top of the hydration reactor (1) to be integrated with the unreacted liquefied gas in the system, and the unreacted liquefied gas is mixed with raw material liquefied gas and then enters a gas compressor (5) again for recycling; the saturated brine separated by the crystal liquid-solid separator (2) returns to the hydration reactor (1) for cyclic utilization; the separated gas hydrate crystals are sent into a crystallization liquid-solid separation and analysis tower (3) for analysis; gas hydrate crystals in the crystallization liquid-solid separation and analysis tower (3) exchange heat with water sprayed (41) at the top of the crystallization liquid-solid separation and analysis tower (3) and with the temperature of more than 20 ℃, the gas hydrate crystals are decomposed under normal pressure, the decomposed gas is mixed with unreacted liquefied gas, and the gas is compressed by a gas compressor (5) to the pressure required by the hydration reaction for recycling; at least one part of decomposed water enters a heater (4) to be heated to more than 20 ℃, and enters a crystallization liquid-solid separation desorption tower (3) through a spray (41) to desorb gas hydrate;

the reaction temperature in the hydration reactor (1) is not lower than 0.5-5 ℃, and the reaction pressure is 2.5-6.0 MPa.

2. Method according to claim 1, characterized in that the content of propane and butane in the liquefied gas inlet line (1b) is not less than 60%.

3. The method according to claim 1, characterized in that the bottom of the crystallization liquid-solid separation and desorption tower (3) is also provided with a part of water for sending dissolved salt in a dissolved salt brine-making section.

4. The method of claim 1, wherein the saturated brine is cooled to a temperature not exceeding 5 ℃ by heat exchange with the outside in the atmosphere before entering the first temperature regulator (6).

5. A method according to claim 1, characterized in that the liquefied gas is cooled to a temperature not exceeding 5 ℃ by air before entering the second temperature regulator (7).

6. The process according to claim 1, characterized in that the brine inlet is located at a position below the reaction level of the hydration reactor (1).

Technical Field

The invention relates to a salt preparation method.

Background

Most of Chinese edible salt is produced by using refined salt as base salt, and the refined salt is generally produced by adopting salt dissolving brine preparation, brine refining and vacuum evaporation. Among them, the vacuum salt-making technology has been developed to adopt the most advanced five-effect vacuum evaporation technology. The five-effect vacuum evaporation production process can be divided into four types, namely parallel flow (concurrent flow), countercurrent flow, advection and cross flow according to the flowing direction of the materials and steam. The four flows have the lowest energy consumption and stable operation, and are beneficial to the current advective feeding, effect-separated preheating, forward flow mother liquor conversion and effect-separated salt discharge flows of controlling the solid-liquid ratio and the mother liquor concentration in the evaporation tank. The material trend of this procedure is: the brine is preheated to about 47 ℃ by mixed condensate water, and then is subjected to effect-division preheating by a preheater, and feed liquid is nearly subjected to effects of V, IV, III, II and I after being preheated by a preheater, so that the temperature rise of the brine in an evaporation tank is reduced; salt slurry system: salt is discharged from each effect of salt feet, and elutriation water is added to the salt feet to improve the salt quality and reduce the salt discharging temperature to about 55 ℃; mother liquor system: the effect I is changed into the effect II, the effect II is changed into the effect III, the effect III is changed into the effect IV, the effect IV is changed into the effect V, and the effect V is intensively discharged. Although the steam consumption of the evaporation of the salt per ton is only 0.72 ton, the energy consumption of all vacuum evaporation processes is low, but the energy consumption is still considerable due to the evaporation nature of the salt per ton. From the above description of the material trend, it can be seen that the process is rather complicated and various equipments are numerous, which makes the investment of the fixed assets of the vacuum evaporation section high. Vacuum evaporation is a very energy-consuming operation, which not only consumes steam to raise the temperature of saturated brine to about 110 ℃, but also consumes a large amount of steam and electric energy (five-effect vacuum evaporation consumes about 0.72t/t of salt per unit of steam and about 56KWh/t of salt per unit of electricity).

Salt lakes in China are mostly distributed in northwest areas such as Qinghai and Nemeng, the annual average temperature of the areas is generally lower than 10 ℃, particularly the whole-day temperature of the areas in spring and winter is close to or lower than 0 ℃, and how to develop a salt making method suitable for the local climate by utilizing the local climate is imperative.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method for producing refined salt by utilizing gas hydration and dehydration, which has low energy consumption and is suitable for low temperature.

The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method for producing refined salt by utilizing gas hydration dehydration is characterized in that the method relates to a hydration reactor, a crystallization liquid-solid separator, a desorption tower, a heater, a centrifuge, a gas compressor, a first temperature regulator, a second temperature regulator, a liquefied gas inlet pipe and a brine pipeline, wherein the brine pipeline enters the hydration reactor after passing through the first temperature regulator, the liquefied gas inlet pipe enters the hydration reactor after passing through the second temperature regulator, the gas outlet end at the top of the hydration reactor is connected with the gas inlet of the gas compressor, the bottom of the hydration reactor is provided with a first slurry outlet, the middle of the hydration reactor is provided with a second slurry outlet, the upper of the hydration reactor is provided with a brine inlet, the lower of the hydration reactor is provided with a liquefied gas inlet, the crystallization liquid separator is provided with a top gas outlet connected with the liquefied gas inlet of the hydration reactor, a bottom inlet connected with the brine outlet of the hydration reactor, a feed inlet connected with the second slurry outlet of the hydration reactor and a discharge outlet in the middle of the hydration reactor, the desorption tower is provided with a feed inlet connected with the discharge outlet of the crystallization liquid separator and a top gas outlet connected with the gas inlet of the gas compressor, spraying is arranged in the desorption tower, and a pipeline entering the heater is arranged at the bottom of the desorption tower; the heater heats the water in the spray, and the feed end of the centrifuge is connected with the first slurry outlet of the hydration reactor and is provided with a first discharge end which returns to the brine pipeline and a second discharge end which can produce wet product salt;

after saturated brine is sent into a first temperature regulator through a brine pipeline, the temperature of the brine is regulated to a required temperature according to the change condition of the hydration reaction temperature in a hydration reactor, and the saturated brine is sent into the hydration reactor through a brine inlet; pressurizing the liquefied gas in a gas compressor to the pressure required by the hydration reaction, then sending the liquefied gas into a second temperature regulator to regulate and control the temperature required by the hydration reaction, and blowing the liquefied gas from the bottom of the hydration reactor; in the hydration reactor, the liquefied gas and the water component in the saturated brine are subjected to hydration reaction to generate gas hydrate crystals; the dissolved salt corresponding to the consumed water amount is separated out by sodium chloride crystallization; because the specific gravity of the gas hydrate crystals is less than that of the saturated brine, the gas hydrate crystals float up to the reaction liquid surface under the action of buoyancy, and because the specific gravity of the sodium chloride crystals is greater than that of the saturated brine, the sodium chloride crystals sink to the bottom of the hydration reactor under the action of gravity; sending the crystal salt slurry discharged from the bottom of the hydration reactor into a centrifugal separator for separation and dehydration, and obtaining wet product salt after centrifugal dehydration for preparing refined salt; mixing saturated brine obtained by centrifugal dehydration with new raw material saturated brine, and sending the mixture into a first temperature regulator for cyclic utilization; gas hydrate crystal slurry discharged from the liquid level enters a crystal liquid-solid separator, unreacted liquefied gas in the crystal liquid-solid separator returns to a hydration reactor from the top of the hydration reactor to be integrated with the unreacted liquefied gas in the system, and the unreacted liquefied gas is mixed with raw material liquefied gas and then enters a gas compressor again for recycling; the saturated brine separated by the crystallization liquid-solid separator returns to the hydration reactor for cyclic utilization; the separated gas hydrate crystals are sent into a desorption tower for desorption; exchanging heat between the gas hydrate crystals in the desorption tower and water with the temperature of more than 20 ℃ sprayed by a spray head at the top of the desorption tower, decomposing the gas hydrate crystals at normal pressure, mixing the decomposed gas with unreacted liquefied gas, and compressing the mixture by a gas compressor to the pressure required by the hydration reaction for recycling; at least one part of decomposed water enters a heater to be heated to more than 20 ℃, and enters an analysis tower to analyze the gas hydrate; the reaction temperature in the hydration reactor is not lower than 0.5-5 ℃, and the reaction pressure is 2.5-6.0 MPa.

Hydration reaction of nonpolar gas with molecular size between neon and butane and CO₂、H₂S and other few weakly polar gas components, partial substitutes of hydrocarbon gas molecules (such as methyl bromide and Freon) and non-gaseous substances such as TBAB, THF and the like react with water at high pressure and low temperature, water molecules are combined through hydrogen bonds to form a cage-shaped lattice structure, and small gas molecules are filled in cavities among lattices to generate non-stoichiometric cage-shaped hydrates.

Preferably, the content of propane and butane in the liquefied gas inlet pipe is not lower than 60%.

Furthermore, a part of water at the bottom of the desorption tower is used for conveying the dissolved salt in the salt dissolving and halogen making section.

Further, heat exchange is carried out on the saturated brine and the outside in the atmospheric environment before the saturated brine enters the first temperature regulator, and the temperature of the saturated brine is reduced to be not more than 5 ℃.

Further, the liquefied gas is cooled to a temperature not exceeding 5 ℃ by air before entering the second temperature regulator.

Further, the brine inlet is positioned below the reaction liquid level of the hydration reactor.

Compared with the prior art, the invention has the advantages that: vacuum evaporation operation is not needed, and energy consumption is low; hydrate generation and salt precipitation are completed in a set of equipment, the process flow is simple, the equipment requirement is low, and the investment of fixed assets is low; the micro-molecular gas required by the generated gas hydrate can be recycled, and the environment pollution is avoided. Is particularly suitable for salt production in northwest China.

Drawings

FIG. 1 is a schematic flow chart of an embodiment.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

As shown in fig. 1, the preparation method of refined salt by gas hydration and dehydration in this embodiment relates to a hydration reactor 1, a crystallization liquid-solid separator 2, a crystallization liquid-solid separation and analysis tower 3, a heater 4, a centrifuge 8, a gas compressor 5, a first temperature regulator 6, a second temperature regulator 7, a liquefied gas inlet pipe 1b and a brine pipeline 1a, the brine pipeline 1a enters the hydration reactor 1 through the first temperature regulator 6, the liquefied gas inlet pipe 1b enters the hydration reactor 1 through the second temperature regulator 7, the top gas outlet end of the hydration reactor 1 is connected to the gas inlet of the gas compressor 5, the bottom of the hydration reactor 1 is provided with a first slurry outlet, the middle of the hydration reactor is provided with a second slurry outlet, the upper of the hydration reactor is provided with a brine inlet, the lower of the hydration reactor 1 is provided with a top gas outlet connected to the liquefied gas inlet of the hydration reactor 1, and the crystallization reactor is provided with a bottom inlet connected to the brine outlet of the hydration reactor 1, a bottom of the hydration reactor 1 is provided with a top gas outlet connected to the liquefied gas-liquid separator, and a bottom of the hydration reactor 1 is connected to the bottom of the hydration reactor, A feed inlet connected with a second slurry outlet of the combined reactor and a discharge outlet at the middle part, wherein the crystallization liquid-solid separation and analysis tower 3 is provided with a feed inlet connected with a discharge outlet of a crystallization liquid separator and a top gas outlet connected with a gas inlet of a gas compressor 5, a spray 41 is arranged in the crystallization liquid-solid separation and analysis tower 3, and the bottom is provided with a pipeline entering a heater 4; the heater 4 heats the water in the spray 41, and the feed end of the centrifuge 8 is connected with the first slurry outlet of the hydration reactor 1 and is provided with a first discharge end which is refluxed to a brine pipeline and a second discharge end which can produce wet product salt;

after saturated brine is sent into the first temperature regulator 6 through the brine pipeline 1a, the temperature of the brine is regulated to a required temperature according to the change condition of the hydration reaction temperature in the hydration reactor 1, and the saturated brine is sent into the hydration reactor 1 through a brine inlet; pressurizing the liquefied gas in a gas compressor 5 to the pressure required by the hydration reaction, then sending the liquefied gas into a second temperature regulator 7 to regulate and control the temperature required by the hydration reaction, and blowing the liquefied gas from the bottom of the hydration reactor 1; in the hydration reactor 1, the liquefied gas and the water component in the saturated brine are subjected to hydration reaction to generate gas hydrate crystals; the dissolved salt corresponding to the consumed water amount is separated out by sodium chloride crystallization; sending the crystal salt slurry discharged from the bottom of the hydration reactor 1 into a centrifugal separator for separation and dehydration, and obtaining wet product salt after centrifugal dehydration for preparing refined salt; the saturated brine obtained by centrifugal dehydration is mixed with the saturated brine of the new raw material and then sent into a first temperature regulator 6 for cyclic utilization; gas hydrate crystal slurry discharged from the liquid surface enters a crystal liquid-solid separator 2, unreacted liquefied gas in the crystal liquid-solid separator 2 returns to a hydration reactor 1 from the top of the hydration reactor 1 to be integrated with the unreacted liquefied gas of the system, and the unreacted liquefied gas is mixed with raw material liquefied gas and then enters a gas compressor 5 again for recycling; the saturated brine separated by the crystal liquid-solid separator 2 returns to the hydration reactor 1 for cyclic utilization; the separated gas hydrate crystals are sent into a crystallization liquid-solid separation and analysis tower 3 for analysis; gas hydrate crystals in the crystallization liquid-solid separation and analysis tower 3 exchange heat with water sprayed at the top of the crystallization liquid-solid separation and analysis tower 3 at the temperature of more than 20 ℃ by spraying 41 ℃, the gas hydrate crystals are decomposed under normal pressure, and the decomposed gas is mixed with unreacted liquefied gas and compressed by a gas compressor 5 to the pressure required by the hydration reaction for recycling; at least one part of decomposed water enters a heater 4, the temperature is raised to be higher than 20 ℃, and the decomposed water enters a crystallization liquid-solid separation desorption tower 3 through a spray 41 to desorb gas hydrate;

the reaction temperature in the hydration reactor 1 is not lower than 0.5-5 ℃, and the reaction pressure is 2.5-6.0 MPa.

The content of propane and butane in the liquefied gas inlet pipe 1b is not lower than 60%. And a part of water at the bottom of the crystallization liquid-solid separation and analysis tower 3 is used for conveying the dissolved salt to a salt dissolving and halogen making section. The saturated brine is subjected to heat exchange with the outside in the atmospheric environment before entering the first temperature regulator 6, and the temperature of the saturated brine is reduced to be not more than 5 ℃. The liquefied gas is cooled to a temperature not exceeding 5 c by air cooling before entering the second temperature regulator 7. The brine inlet is positioned below the reaction liquid level of the hydration reactor 1.

In the embodiment, natural climate advantages of northwest China are utilized, saturated brine in salt dissolving brine or salt lake is naturally cooled to the ambient temperature in the atmospheric environment, the brine is sent to a hydration reactor to perform hydration reaction with small molecule gas such as liquefied gas (mainly comprising propane and butane), ice-like gas hydrate crystals are generated, and sodium chloride crystals are separated out. The gas hydrate crystals are resolved in a resolving tower, the resolved liquefied gas is recycled, and the resolved water can be used for dissolving salt to prepare brine; the separated sodium chloride crystal is centrifugally dehydrated and dried to obtain the refined salt product. The brine is cooled to the generation temperature of the gas hydrate by utilizing the atmospheric temperature, the vacuum evaporation operation is not needed, and the energy consumption is low; the hydrate generation and the salt precipitation are completed in a set of equipment, the process flow is simple, the equipment requirement is low, and the investment of fixed assets is low; the gas needed by the gas hydrate can be recycled, and the method has no environmental pollution, and is a refined salt production method with low energy consumption, low investment and no pollution.

The gas hydration reaction is primarily carried out at low temperature, and the reaction gas and the brine are cooled by water, which requires a large amount of cold energy. Most of the salt lakes in China are located in the high and cold regions in the northwest of China, and the common characteristic of the regions is low temperature. For example, the annual average temperature of the Tibetan autonomous state of the city of the Mongolia, western and western provinces, where the tea Ka salt lake of China is located, is only about 4 ℃, and the 1971 to 2000 years of the state have average temperature data as shown in the following table 1.

TABLE 1 temperature conditions (. degree. C.) of the Haisizhou area where the tea Ka salt lake is located

	1 month	2 month	3 month	4 month	Month 5	6 month	7 month	8 month	9 month	10 month	11 month	12 month
													Mean temperature	-10.9	-6.6	-0.5	5.6	11.0	14.2	16.5	16.1	11.2	3.9	-3.8	-9.2
Average maximum temperature	-3.7	0.7	6.7	12.9	17.8	20.7	23.1	23.0	18.3	11.5	3.7	-1.6
													Mean minimum temperature	-16.8	-12.3	-7.0	-1.2	4.5	8.2	10.7	10.2	5.2	-2.0	-9.4	-14.9

From the above table, it can be seen that the brine can be easily cooled to below 5 ℃ to reach the generation temperature of the gas hydrate by fully contacting the saturated brine in the brine storage tank or the saturated brine in the salt lake with the atmosphere or cooling the saturated brine by an air cooler. Even in seasons with average temperature higher than 5 ℃, the temperature of the brine can be reduced and then stored in a heat-preservation storage tank for daytime production in the evening to the early morning when the temperature is lower. In different production seasons, the hydration reaction temperature should be properly adjusted according to the temperature change condition, so as to make full use of the climate condition and reduce the production energy consumption. The hydration temperature cannot be too low during the production season with the lowest atmospheric temperature. When the hydration reaction temperature is lower than 0.15 ℃, sodium chloride crystals with 2 crystal water, namely NaCl & 2H, can be separated out from the hydration reactor₂And O is crystallized, and the crystallization enters a drying section, so that the operation of the drying section is influenced, and the energy consumption of the product salt during drying is increased. The hydration reaction temperature cannot be too high, and when the hydration reaction temperature is too high, the hydration pressure required for generating the gas hydrate is increased, and the energy consumption of gas compression is increased. The range of hydration temperature control considered suitable by research is 0.5 ℃ to 5 ℃.

The formation of gas hydrate is a gas-liquid-solid three-phase reaction, and the pressure of the gas has a great influence on the reaction. The hydrate needs to reach a critical pressure during the formation process to initiate nucleation of the hydrated phase. The critical pressures at which hydrates are formed from different gases vary. Table 2 shows the pressures at 0 ℃ at which hydrates of the main components of liquefied gas are formed.

TABLE 2 hydrate formation pressure of each component in liquefied gas at 0 deg.C

Components	Generating pressure P/MPa	Boiling point or liquefaction temperature, DEG C
			C3H6	0.48	-47.4
C3H8	0.17	-42.09
			C4H8	Without data	-6.9
i-C4H10	0.11	-11.7

Table 2 shows the equilibrium pressure at 0 ℃ for gas hydrate formation, i.e., the system pressure must be maintained at a pressure greater than the equilibrium pressure in the table in order to hydrate a gas with water to form gas hydrate crystals. The difference between the system pressure and the equilibrium pressure is the overpressure, which is the driving force for hydrate growth. The greater the overpressure, the faster the hydrate will grow. 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 2 are the equilibrium pressures for the hydration of pure water with liquefied gas to form gas hydrates. The present invention discusses the hydration reaction of water in saturated brine with liquefied gas. The activity of solutions with different concentrations varies, and decreases in multiple curves with increasing concentration. The activity of pure water was 1.0, the activity of a 26% sodium chloride solution was 0.72, and the temperature had substantially no effect on the activity of the solution. Due to the reduced activity, a greater driving force is required for the hydration reaction of water in brine with liquefied gas, i.e. a greater pressure is required for the hydration reaction of brine with liquefied gas at the same temperature than for the hydration reaction of pure water.

The formation pressure in Table 2 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 still higher. The invention mainly depends on the atmosphere for cooling, and because of different seasons and different atmospheric environment temperatures, the reaction temperature in the hydration reactor is adjusted according to the environmental temperature, so as to fully utilize the climate conditions and reduce the production energy consumption. 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 equilibrium pressure data in the table 2, the butane generates gas hydrate at 0 ℃ with the pressure of only 0.11MPa, and the butane generates hydration reaction with water in brine, and the energy consumption of compressed gas is 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 reactor. Because the hydration reactor is not suitable for being provided with a tube heat exchanger for heat transfer, the invention utilizes the temperature of the brine supplemented in the reaction process to maintain the temperature in the hydration reactor to be stable. When the reaction temperature in the hydration reactor is raised due to the heat release of the hydration reaction, the temperature of brine replenished into the hydration reactor is reduced; when the reaction temperature in the hydration reactor is reduced due to the speed of the hydration reaction, the temperature of the brine supplemented into the hydration reactor is appropriately raised, so that the temperature in the hydration reactor can be easily controlled to be stabilized within an optimum range.

The liquefied gas in the hydration reactor and the water component in the brine are subjected to hydration reaction to generate ice-like cage-shaped gas hydrate crystals. The corresponding dissolved salts in the water consumed by the hydration reaction will precipitate as sodium chloride crystals. The two types of crystals formed in the hydration reactor can be separated according to their density differences. The density of the gas hydrate generated from propane was 0.866g/cm³The density of butane-derived gas hydrate was 0.951g/cm³(ii) a The saturated brine in the hydration reactor had a density of 1.197g/cm³(ii) a The density of the sodium chloride crystals was 2.165g/cm³. Because the density of the sodium chloride crystals is greater than that of the liquid-phase brine and the gravity of the sodium chloride crystals is greater than the buoyancy, the crystals can settle downwards under the action of gravity and are collected to the bottom of the hydration reactor; and the gas hydrate crystals can float upwards under the action of buoyancy because the density of the gas hydrate crystals is less than that of saturated brine, and finally the gas hydrate crystals are collected on the liquid surface of a hydration reactor, so that the two types of crystals are effectively separated.

Besides, before starting, saturated brine with a certain liquid level is injected into the hydration reactor, during normal hydration and salt precipitation operation, brine consumed by hydration reaction is continuously supplemented into the system so as to maintain stable operation of the hydration reaction. The point of addition of brine to the hydration reactor is not preferred to the conventional top spray because top spray, while contacting saturated brine with the rising gas, produces gas hydrate crystals with concomitant precipitation of corresponding sodium chloride crystals. The two kinds of crystals generated above the liquid surface are mixed together and fall to the liquid surface, are mixed with gas hydrate crystals generated in a liquid phase and float upwards, enter a liquid-solid separator together, are dehydrated and then enter an analysis tower for analysis, and sodium chloride crystals which cannot be analyzed are dissolved after the generated water is analyzed, so that the yield of refined salt is reduced, and therefore, the position for supplementing brine is preferably arranged below the liquid surface of a hydration reaction.

The decomposition method of the gas hydrate includes a chemical reagent method, a pressure reduction method, a hot water injection method, an electromagnetic heating method, a microwave heating method, and the like. The advantages and disadvantages of the various methods are compared as shown in Table 3.

TABLE 3 analysis of crystal hydrate analysis method

The method takes full consideration of various factors such as environmental protection, low investment, simple technology and the like, selects the hot water injection method as the excitation mode of hydrate decomposition, and designs the reaction condition of resolving and decomposing the crystalline hydrate by the hot water injection method to be 20 ℃ and normal pressure. The device adopts a sloping plate type desorption tower, gas hydrate crystals are fed from the upper part of the desorption tower and are scattered on a sloping plate in the tower during desorption, hot water is sprayed onto the sloping plate from the top of the desorption tower, the temperature of the gas hydrate on the sloping 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 reactor for recycling after being pressurized by the compressor; liquid water is discharged from the bottom of the desorption tower, one part of the liquid water is heated to the desorption temperature by a heat exchanger and sent to the desorption tower for recycling, and the redundant water is sent to a salt dissolving and brine making working section for salt dissolving.