SE531709C2 - Process for purification and evaporation of liquid under vacuum - Google Patents

Description

531? ÜE f) Description of the invention In the process according to the invention mainly known parts are used such as heat exchangers, vacuum pumps and pumps for transporting liquid.

With reference to fi g. Essential components of the construction and application of the invention will be described in more detail.

Fig. 1 shows a diagram of the flows of liquids in the apparatus used Contaminated liquid 1 is fed via the valve 2 and the line 3 to a thirsty heat exchanger 4 of any type. The liquid into the heat exchanger is heated by purified liquid, which is drained from the line 5 and which is supplied to the heat exchanger through the line 6 via the valve 7, which is controlled by the liquid level in a mixing condenser 8. The liquid heated and contaminated in the heat exchanger is through the pipes 9. heat exchanger 11. To this second heat exchanger is also supplied via the line 12 the upper layer of circulating and partially contaminated liquid from the separation vessel 13. To the second heat exchanger (II) heated liquid from condenser (8) is supplied by means of the line 14. This heat dissipating liquid can be heated externally supplied energy through the element 15. The element can be heated via direct-acting electricity or by using a heat pump. Furthermore, hot liquid is supplied to the heat exchanger by means of the line 16 from a third heat exchanger 17. From the second heat exchanger (11), heat-emitting liquid is passed on through the lines 18 and 19 by means of the pump 20 to the previously mentioned mixing condenser (8). The liquid heated and contaminated in the second heat exchanger (II) is led by the line 21 to the third heat exchanger (17) and is passed further through the line 22 to an evaporator vessel 23.

Due to the negative pressure created by the vacuum pump 24, water is evaporated in the evaporating vessel (23). Thereby steam is evacuated through the pipe 25 to the mixing condenser (8) in which the steam is condensed on contact with liquid supplied via line 9. Characteristic of the invention is that slightly volatile gases are removed by means of line 26 and the vacuum pump 24.

Another characteristic part of the invention is that the negative pressure in the evaporation vessel and the mixing condenser are equivalent. Suitable negative pressures vary between 5 and 400 mbar and preferably from 50 to 300 mbar. At a negative pressure of 200-300 mbar, for example, an evaporation is obtained at 60-70 ° C depending on components in the liquid.

ESV! Heating in the third heat exchanger (17) is obtained by expanding and condensing part of the steam from the evaporator vessel (23), which steam is passed via line 27 to the vacuum pump 28 and further through line 29 to the heat exchanger. The steam so partially compressed by the vacuum pump expands and thus emits heat in the heat exchanger, whereby the temperature of the pure water is raised, which then causes indirect heating of the temperature of the impure liquid inside the tubes of the heat exchanger. The water heated by steam is passed from the heat exchanger (17) by means of the line 16 s a s backwards to the second heat exchanger (1 1). Non-condensable gases are passed through line 30 to the mixing condenser. By creating a relatively higher pressure by means of the vacuum pump (28) in the third heat exchanger (17), the circulation of the heat-emitting liquid is facilitated.

Temporarily, a self-circulation of the heat-emitting liquid is obtained.

A further characteristic part of the invention is that the liquid levels in the evaporation vessel and mixing condenser are kept at the same level, i.e. at comparable hydrostatic pressures.

This is achieved by using known control systems (eg level indication control). Liquid collected in the evaporation vessel (23) is passed via line 31 to the separation vessel (13) from where a concentrate of contaminants is removed via line 32, valve 33 and line 34. Draining of the concentrate can performed batchwise or continuously. Partially contaminated liquid is passed through line 35 to pump 36 and through line 12 to the first heat exchanger (4). Thus, the described course of the contaminated liquid is repeated.

As far as the liquid used for heating in continuous operation is concerned, its volume is in principle equivalent to condensed steam from contaminated liquid. In other words, no liquid is supplied from an external source. In ideal conditions, only refilling with clean water is required at the start of the process. However, externally heated liquid can be supplied at start-up.

Advantages of the invention.

When applying the invention, an efficient and relatively energy-efficient purification of contaminated liquid is obtained. Thus, the operation is easy to operate and requires few control units and moving parts. Furthermore, the plant can be built in a container and thus it can be moved to places where there is a need to clean liquid. Components such as mixing condenser, dry evaporator and separation vessel are easy to clean.

Heating in the third heat exchanger (17) is obtained by expanding and condensing part of the steam from the evaporating vessel (23), which steam is conveyed via the line 27 to the vacuum pump 28 and further through the line 29 to the heat exchanger. The steam so partially compressed by the vacuum pump expands and thus emits heat in the heat exchanger, whereby the temperature of the pure water is raised, which then indirectly heats the temperature of the impure liquid inside the tubes of the heat exchanger. The water heated by steam is passed from the heat exchanger (17) by means of the line 16 s a s backwards to the second heat exchanger (II). Non-condensable gases are passed through line 30 to the mixing condenser. By creating a relatively higher pressure by means of the vacuum pump (28) in the third heat exchanger (17), the circulation of the heat-emitting liquid is facilitated.

Temporarily, a self-circulation of the dehydrating fluid is obtained.

A further characteristic part of the invention is that the liquid levels in the evaporator and mixing condenser are kept at the same level, i.e. at comparable hydrostatic pressures.

This is achieved by using known control systems (eg level indication control). Liquid collected in the evaporation vessel (23) is passed via line 31 to the separation vessel (13) from where a concentrate of pollutants is removed via line 32, valve 33 and line 34. Draining the concentrate can performed batchwise or continuously. Polluted liquid is passed through line 35 to pump 36 and through line 12 to the second heat exchanger (1 l). Thus, the described course of the contaminated liquid is repeated.

As for the liquid used for heating in continuous operation, its volume is in principle equivalent to condensed steam from contaminated liquid. In other words, no liquid is supplied from an external source. In ideal conditions, only refilling with clean water is required at the start of the process. However, externally heated liquid can be supplied at start-up.

Advantages of the invention.

When applying the invention, an efficient and relatively energy-efficient purification of contaminated liquid is obtained. Thus, the operation is easy to operate and requires few control units and moving parts. Furthermore, the plant can be built in a container and thus it can be moved to places where there is a need to clean liquid. Components such as mixing condenser, evaporation vessel and separation vessel are easy to clean.

Claims (1)

1. 531 FÜE f? A method for purifying and evaporating liquid, wherein contaminated liquid (1) is caused to be partially evaporated in a vapor deposition vessel (23) after passage through one or more heat exchangers (4.1, 1.17) and by lowering the vapor deposition temperature by means of production of of vacuum pumps (24, 28) characterized in that part of the steam formed in the dry vapor vessel is led to a mixing condenser (8) in which the steam is caused to condense by supply of partially purified liquid while another part of the steam is caused to condense in a heat exchanger (17) and that part of the contaminated liquid (22) in the dry vapor vessel (23) is led to a separation vessel (13). Process according to Claim 1, characterized in that the hydrostatic pressure in the steaming vessel and the mixing condenser are equivalent. Method according to claims 1 and 2, characterized in that the negative pressure in dry vapor vessels and mixing condenser are equivalent corresponding to the selected hydrostatic liquid level. Process according to claims 1-3, characterized in that the liquids in dry vapor vessels and mixing condenser are kept at the selected and the same level by filling with contaminated liquid and / or by draining purified liquid from one or more heat exchangers. Method according to Claims 1 to 4, characterized in that part of the steam from the steaming vessel is compressed by means of a vacuum pump (28) before the entry into a heat exchanger (17). Method according to Claims 1 to 5, characterized in that non-condensable gases in the mixing condenser and in a heat exchanger (17) are wiped off by means of a vacuum pump (24). Method according to claims 1-6, characterized in that condensed liquid in one heat exchanger (17) is caused to self-circulate and emit heat in another heat exchanger (1 1). Method according to claims 1-7, characterized in that concentrate of contaminants is drained from the bottom zone of the separation vessel via a line (32). Method according to Claims 1 to 8, characterized in that the surface layer of the partially contaminated liquid in the surface layer of the separation vessel is led to a heat exchanger (11). 53? ÃFÜÉ. Method according to Claims 1 to 5, characterized in that partially contaminated liquid is mixed with supplied contaminated liquid before the entry into the heat exchanger (11).