RU2311347C2 - Method of purification of the water - Google Patents

Abstract

FIELD: petrochemical industry; gas-processing industry; other industries; methods of purification and desalination of the water and the water solutions of the salts in the industry and household.

SUBSTANCE: the invention is pertaining to the production process of purification and desalination of the water and the water solutions of the salts in the industry and household activities and may be used for purification of the drinking water and the industrial waste waters. The method provides for cooling of the water, formation of the gaseous hydrates and their subsequent decomposing into the gas and the purified water. Previously the purified water is saturated with the hydrate-forming gas, and then in the reactor it is exposed to the dispersion up to the water particles sizes less than 1 micron in the flow of the hydrate-forming gas in the conditions of the intensive hydrate-forming. In the capacity of the hydrate-forming gas it is preferable to use propane, carbon dioxide, freon. For improvement of the production process parameters in the capacity of the hydrate-forming gas use the mixture of the indicated gases. The conditions of formation of the gaseous hydrates - the temperature and the pressure are set depending on the selected hydrate-forming gas. The preliminary saturation of the purified water with the hydrate-forming gas is conducted at the pressure, which is less than the pressure of the selected hydrate-forming gas. Formation of the gaseous hydrates conduct preferentially in the presence of that hydrate-forming gas, which is used for saturation of the being purified water. The method ensures at the minimal power inputs production of the water of the high degree of purification.

EFFECT: the invention ensures production of the water of the high degree of purification at the minimal power inputs.

7 cl, 6 tbl, 5 ex

Description

The invention relates to a technology for purification and desalination of water, aqueous solutions of salts in industry and at home, and can be used to purify drinking water, industrial effluents.

A known method of desalination of sea water [patent RU No. 2239602, C02F 1/00, publ. 11/10/2004], including mixing ammonia with the specified water to form an effective amount of ammonium hydroxide, to react with the NaCl salt molecules present in the specified water, and weakening the bonds in the indicated NaCl molecules, spraying the specified water in the form of fine sprays in closed process chamber near the top thereof, the impact on the water spray effective amount of combustion exhaust gas (CO ₂₎ to react with said softening molecules and formation and removal TBE gut substances sodium carbonate and ammonium chloride in a sump located below said process chamber, settling and removing solids through lower outlet pipe and discharging desalinated water discharge as an overflow from said clarifier.

The disadvantages of this invention are the energy consumption of the device, the complexity and duration of the process, insufficient degree of water purification, the use of a chemical reagent.

A known method of desalination, selected as a prototype [Yu.F. Macogon. Hydrates of natural gases. M .: Nedra, 1974, p. 192-193]. Mineralized water enters the deaerator, where dissolved gases are removed from it. Then it is fed into the reactor, pre-cooled in heat exchangers by streams of fresh water and brine. At the same time, liquefied propane from the receiver is introduced through the throttle valve into the reactor. Propane and water are mixed at a pressure of about 5 kgf / cm ² and a temperature of 1.7 ° C, i.e. under conditions of intense hydrate formation. The degree of subcooling in this case reaches 1.5-2 ° C. The hydrate flakes formed, together with the brine, are sent to the separation column, after which the hydrates washed with fresh water (up to 10% of fresh water are used to wash the sorbed salts from the hydrate) are fed to the hydrate decomposition tank, where the pressure is maintained at about 6 kgf / cm ² and temperature 7. 5 ° C. Hydrate decomposes into liquefied propane and water. As a result of the difference in densities, gas and water are separated. Water is supplied to the consumer, and the gas after compression by the compressor, is fed back to the reactor through the condenser, heat exchanger and receiver.

The disadvantages of this invention include the fact that the formation of crystalline hydrates occurs on the surface of the granules of gas hydrate, which leads to the appearance of impurities in purified water. It is necessary to spend 10-20% of purified water for washing crystalline hydrates, otherwise the degree of water purification will be low.

The objective of the invention is to develop a method of purifying water, in particular its desalination, which allows, like the prototype, to use the minimum energy costs, but, unlike the prototype, to get cleaner water.

The specified technical result is achieved in that the method of water purification includes its cooling, the formation of gas hydrates and their subsequent decomposition into gas and purified water.

A feature of the proposed method is that the purified water is preliminarily saturated with a hydrate-forming gas, and then it is dispersed in the reactor to a particle size of water of less than 1 μm in a stream of hydrate-forming gas under conditions of intensive hydrate formation.

In addition, propane, carbon dioxide, freon are used as a hydrate-forming gas.

In addition, to improve process parameters, a mixture of the above gases is used as a hydrate-forming gas.

In addition, the conditions for the formation of gas hydrates, namely temperature and pressure, are selected depending on the selected hydrate-forming gas.

In addition, pre-saturation of the purified water with a hydrate-forming gas is carried out at a pressure lower than the hydrate pressure of the selected gas.

In addition, the formation of gas hydrates is carried out, preferably, in the presence of the hydrate-forming gas, which saturates the purified water.

In addition, to bring the hydrate-forming gas content in purified water to the level of maximum permissible concentration (MPC), purified water is saturated with a gas that is harmless to human health, for example, CO ₂ or O ₂ .

The problem is achieved in that gas hydrates are formed in a stream of hydrate-forming gas by the interaction of the latter with finely dispersed drops of water pre-saturated with hydrate-forming gas, while water disperses and gas hydrates form continuously, which eliminates the formation of salt hydrates both on the surface and inside the granules gas hydrate. Therefore, in the proposed method, in contrast to the prototype, the need for washing operations disappears and the degree of water purification sharply increases. Preliminary saturation of the purified water with a hydrate-forming gas is carried out at a pressure less than the hydrate pressure of the selected gas. Pre-saturation and dispersion of water to a particle size of less than 1 μm in a stream of hydrate-forming gas makes it possible to start the formation of gas hydrates from the center of a drop of water, and not on its surface, as in the prototype, which eliminates the appearance of impurities in purified water.

As a hydrate-forming gas, propane, carbon dioxide, and freon are used.

To improve process parameters, a mixture of the above gases can be used as a hydrate-forming gas. This leads at a set temperature to a decrease in pressure or at a set pressure to an increase in the temperature of formation of gas hydrates, which reduces energy costs when implementing the proposed method.

A preferred embodiment of the water purification method is that the same gas is used in the pre-saturation and hydrate formation processes.

To bring the hydrate-forming gas content in purified water to the level of maximum permissible concentration (MPC), purified water is saturated with a gas that is harmless to human health, for example, CO ₂ or O ₂ . This must be done to ensure the safety of the health of water consumers.

The proposed method is as follows.

Purified water containing various salts (sodium, calcium, magnesium, etc.) is fed into a sealed container, where it is saturated with a hydrate-forming gas at a pressure lower than the hydrate pressure of the selected gas, preferably (0.7-0.8) P, where P is the hydrate pressure selected gas. The water is cooled to a temperature of 268-283K. Further, in the reactor, which is a device for mixing gas and water, the above water is dispersed to a particle size of water less than 1 μm in a stream of hydrate-forming gas and gas hydrates are formed as a result of its interaction with the gas at a set temperature, pressure and mixing intensity. Gas hydrates are separated from the gas and water flow in a cyclone, where after their decomposition get water suitable for domestic and technical use. To reduce the hydrate-forming gas in purified water to MPC, it is saturated with a gas that is harmless to human health, for example, CO ₂ or O ₂ .

Examples of specific performance.

For examples, aqueous solutions of sodium chloride of various concentrations were used.

Example 1

Purified water is fed into a sealed container, where it is saturated with propane under a pressure of 320 kPa, to the boundary of gas hydrate formation. The water is cooled to a hydrate formation temperature of 277 K and fed to the reactor. Water is finely dispersed in the reactor in a propane stream, which is supplied at a pressure of 454 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 277K. Gas hydrates are separated from gas and water streams in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

Table 1.
Propane gas hydrate formation conditions T, K R, kPa The degree of purification without saturation (%) The degree of purification with saturation (%) 174 323 454 515 554 ≈84 ≈95 268 + + + + + 273 + + + + + 277 - - + + + 279 - - - + + 283 - - - - - "+" - hydrates are formed; "-" - hydrates are not formed.

Example 2

Purified water is fed into a sealed container, where it is saturated with Freon 11 under a pressure of 16 kPa. The water is cooled to a hydrate formation temperature of 279K and fed to the reactor. Water is finely dispersed in the reactor in a gas stream of Freon 11, which is supplied at a pressure of 22 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 279 K. Gas hydrates are separated from gas and water streams in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

Table 2.
The conditions for the formation of freon gas hydrates 11. T, K R, kPa The degree of purification without saturation (%) The degree of purification with saturation (%) 5.1 9.1 21.8 35.5 62.3 ≈85 ≈96 268 + + + + + 273 - + + + + 277 - - + + + 279 - - + + + 283 - - - - - "+" - hydrates are formed; "-" - hydrates are not formed.

Example 3

Purified water is fed into a sealed container, where it is saturated with Freon 22 under a pressure of 53 kPa. The water is cooled to a hydrate formation temperature of 268K and fed to the reactor. Water is finely dispersed in the reactor in a stream of Freon 22, which is supplied at a pressure of 71 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 268K. Gas hydrates are separated from gas and water flows in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

Table 3.
Conditions for the formation of Freon gas hydrates 22. T, K R, kPa The degree of purification without saturation (%) The degree of purification with saturation (%) 71 98.5 149 198 332 ≈83 ≈95 268 + + + + + 273 - + + + + 277 - - + + + 279 - - - + + 283 - - - - + "+" - hydrates are formed; "-" - hydrates are not formed.

Example 4

Purified water is fed into a sealed container, where it is saturated with Freon 12, at a pressure of 63 kPa. Then the water is cooled to a hydration temperature of 277K and fed to the reactor. Water is finely dispersed in the reactor in a stream of Freon 12, which is supplied under a pressure of 88.2 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 277 K. Gas hydrates are separated from gas and water flows in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

Table 4.
Conditions for the formation of freon gas hydrates 12. T, K R, kPa The degree of purification without saturation (%) The degree of purification with saturation (%) 28.9 38.6 88.2 123 280 ≈87 ≈98 268 + + + + + 273 - + + + + 277 - - + + + 279 - - - + + 283 - - - - + "+" - hydrates are formed; "-" - hydrates are not formed.

Example 5

Purified water is fed into a sealed container, where it is cooled to a hydrate formation temperature equal to 277K, saturated with a gas mixture: propane with the addition of Freon 12, under a pressure of 183 kPa. The water is cooled to a hydrate formation temperature of 277K and fed to the reactor. Water is finely dispersed in the reactor in the stream of the above gas mixture, which is supplied at a pressure of 244.1 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 277K. Gas hydrates are separated from gas and water flows in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

Table 5.
The conditions for the formation of gas hydrates of the gas mixture: propane + freon 12. T, K R, kPa The degree of purification without saturation (%) The degree of purification with saturation (%) 101,4 180.8 244.1 319 418.5 ≈85 ≈98 268 + + + + + 273 - + + + + 277 - - + + + 279 - - - + + 283 - - - - + "+" - hydrates are formed; "-" - hydrates are not formed.

Example 6

Purified water is fed into a sealed container, where it is cooled to a hydrate formation temperature equal to 279K, saturated with Freon 22, under a pressure of 120 kPa and fed to the reactor. Water is finely dispersed in the reactor in a stream of Freon 12, which is supplied at a pressure of 123 kPa, resulting in the formation of gas hydrates in the reactor at a set temperature of 279 K. Gas hydrates are separated from gas and water flows in a cyclone, where, after their decomposition, water is purified from sodium chloride salts.

The advantages of the proposed method of water purification - the gases used for the formation of gas hydrates can be used in a closed cycle, the heat is generated during the formation of gas hydrates, and is absorbed during decomposition, so the whole process requires minimal energy, the productivity of the method can vary widely and depends on from the performance of the compression equipment, the main apparatuses for carrying out the process of water purification by the gas-hydrate method have insignificant dimensions ≈1.2 m ³ when productivity 200 m ³ / h, the degree of water purification reaches up to 95-98%.

Claims (7)

1. The method of water purification, including its cooling, the formation of gas hydrates and their subsequent decomposition into gas and purified water, characterized in that the purified water is pre-saturated with hydrate-forming gas, and then it is dispersed in the reactor to a particle size of water less than 1 μm in a stream hydrate-forming gas under conditions of intense hydrate formation. 2. The method according to claim 1, characterized in that propane, carbon dioxide, freon are used as a hydrate-forming gas. 3. The method according to claim 2, characterized in that to improve the technological parameters as a hydrate-forming gas using a mixture of these gases. 4. The method according to claim 1, characterized in that the conditions for the formation of gas hydrates, namely temperature and pressure, are set depending on the selected hydrate-forming gas. 5. The method according to claim 1, characterized in that the preliminary saturation of the purified water with a hydrate-forming gas is carried out at a pressure less than the pressure of hydrate formation of the selected gas. 6. The method according to claim 1, characterized in that the formation of gas hydrates is carried out, preferably, in the presence of the hydrate-forming gas, which saturates the purified water. 7. The method according to claim 1, characterized in that to bring the hydrate-forming gas content in the purified water to the level of maximum permissible concentration (MPC), the purified water is saturated with a gas that is harmless to human health, for example, CO ₂ or O ₂ .