WO1982000459A1

WO1982000459A1 - Method and device for purifying waste water

Info

Publication number: WO1982000459A1
Application number: PCT/EP1981/000111
Authority: WO
Inventors: H Apfelbaum
Original assignee: H Apfelbaum
Priority date: 1980-08-04
Filing date: 1981-08-04
Publication date: 1982-02-18
Also published as: EP0057228A1; DE3029541A1; DE3029541C2

Abstract

The purification method of polluted water by dissolved materials which are separable through crystallization, consists in circulating the solution in a heat exchanger where the vaporization temperature is reached, in feeding the solution into a separator in which the vaporization is achieved by expansion. The solution is then fed back to the heat exchanger and the solid materials precipitated by the concentration of the solution are withdrawn from the liquid flow. The apparatus for implementing the method comprises a heat exchanger (14), a separator (16) connected to the exchanger, an extraction device (42) and a means (48) for feeding back the solution to the exchanger.

Description

Waste water treatment process and apparatus

description

The invention relates to a method and a device for cleaning waste water.

The disposal of wastewater contaminated with inorganic pollutants is an environmental problem today. Both wastewater is mainly leachate from special waste dumps and aqueous special waste

and industrial wastewater contaminated with inorganic substances such as sulfates (especially calcium sulfate), chlorides and heavy metals and other pollutants in solution. In the case of such waste water, the number of substances in solution, their concentration and their amount are usually not known, and these values can also vary widely. So far it has only been possible to analyze and then dispose of this waste water at great expense. So far, this waste water can only be disposed of at a very high cost, for example in incineration plants. Another possibility of disposing of the waste water contaminated with inorganic pollutants is crystallization. According to the current state of the art, there are limits to disposal by crystallization. All known crystallization processes (eg surface cooling crystallization, evaporation crystallization, vacuum cooling crystallization and fractional crystallization) have in common that only one salt with a certain grain size and quality is obtained, which is obtained as a high quality product. Material and mass balances are the basis of these processes. When using these known crystallization processes, which are referred to as controlled crystallization, it is therefore a prerequisite that the number of substances in solution, their concentration and quantity of substances must be analyzed before carrying out the crystallization process, which results in high costs. The physical properties of the crystals and the salt yield are then the basis of the calculation for the process parameters of the crystallization, in particular for the evaporation capacity, to which the apparatus parts must be designed.

Another problem that arises when using conventional crystallization processes for wastewater disposal is that the critical wastewater ingredients tend to precipitate and crystallize during evaporation and crust formation. Therefore, it was previously not possible to use evaporator types known per se (e.g. circulation evaporators, falling film evaporators, thin-film evaporators, agitator evaporators and immersion burner server evaporators) for waste water disposal, since these are clogged by the resulting solids. The corrosion of the system parts by the pollutants in the wastewater also creates greater problems, the higher the concentration of the pollutants in the wastewater, which increases with the concentration of the wastewater solutions. Therefore, it has been necessary to use high-quality materials for the system parts.

In contrast, the invention has for its object to provide a method and an apparatus for purifying wastewater, with which all accruing wastewater loaded with inorganic pollutants regardless of the pollutant concentrations or regardless of the balance of pollutants, which are subject to constant change can be disposed of.

For this purpose, the method according to the invention and the device according to the invention are designed in the manner characterized in the first method claim and the first device claim.

In the method according to the invention or in the device according to the invention there is an uncontrolled crystallization and precipitation carried out, in which the constant change and indefinite balances of the pollutants dissolved in the waste water are irrelevant. In other words, the material values and the salt yield can be unknown in the case of uncontrolled crystallization. The only basis for calculation is the maximum evaporation capacity, which is matched to the amount of solution implemented. In the case of uncontrolled crystallization, the salt and pollutant yield change while the evaporation rate is being determined. At the specified evaporation capacity, all inorganic and a large number of ingredients can then be processed continuously and without interference regardless of their concentration in the waste water. The pollutants accumulate in solid or crystalline form with low moisture so that they can be deposited in a special landfill. An economical way of working through automation, the lowest possible personnel costs, low investment and operating costs is advantageously possible with the invention.

As already mentioned; The evaporation of waste water in conventional evaporators is problematic because of the deposits and the formation of crusts. According to the invention, this problem is addressed in that the crystallization and precipitation (in which the risk of crust formation is particularly great) does not take place in the evaporator, but in the downstream separator. A further improvement with regard to this problem results in the design of the device according to the invention, which has a plate heat exchanger with an increasing film as the evaporator. In such a plate heat exchanger with increasing film, two plates form a unit and the waste water or solution flows through the channels formed by the plate unit from bottom to top, while the steam flows through the plate heat exchanger in countercurrent from top to bottom. A high flow velocity of the solution in the channels creates a high flow turbulence, which is caused by a appropriate plate embossing is still supported so that solids carried along by the solution carry away any deposits in the channels and thus flush the channels.

Advantageous embodiments of the invention are characterized in the subclaims, as a result of which the economy in the disposal of the waste water is increased still further.

An embodiment of the invention will now be described with reference to the accompanying drawings. Show it:

Figure 1 is a schematic representation of the device according to the invention;

Figure 2 is a schematic drawing of a plate heat exchanger as it is provided in the device according to the invention.

The device shown in Fig. 1 has a reservoir 2 for the waste water to be treated. An inlet 4 is provided on the reservoir 2 for filling the reservoir with leachate or other inorganically contaminated waste water. The storage container 2 is connected to a feed line 6 with a pump 8, the output of which is connected by an output line 10 to a connecting line 12 which on the one hand opens into the circulation circuit and on the other hand into the storage container. Between the connection point of the outlet line 10 and the connection line 12 and the reservoir 2, a back pressure valve 13 is provided through which the return flow of the waste water from the pump 8 is throttled into the reservoir 2 and thus enables the inflow of the waste water via the line 12 into the circulation circuit . The back pressure valve 13 also makes it possible to feed several of the devices shown here in parallel from the storage container 2.

The circulation circuit has a plate heat exchanger 14, a tangential separator 16 and a pump 18. The Plate heat exchanger 14 is connected to the tangential compressor 16 via a riser 20, and this is connected to the pump 18 through a drain line 22, the outlet line 24 of which leads back to the plate heat exchanger 14. A sampling tap 26 with a valve 28 is provided on the circulation circuit downstream of the pump 18.

The vapor outlet 30 of the tangential separator 16 is connected via an inlet line 32 to a mechanical vapor compressor 34, the outlet line 36 of which leads to the steam inlet 38 of the plate heat exchanger 14. The outlet of the steam flow path system of the plate heat exchanger 14 is a drain line 40.

The device also has a bypass line with a second, static separator 42. The bypass line is provided by an inflow line 44 leading from a branch on the recirculation circuit to the separation chamber 46 of the separator 42 and also a solution drain line 48 which leads from the solution chamber 50 via a pump 52 back to the circulation circuit to one Point leads, which opens into the circulation circuit between the branch of the inflow line 44 and the plate heat exchanger 14. The inflow line 44 also serves as a cooling line in which further amounts of solid precipitate out of the solution. To accelerate the separation, the inflow line 44 opens tangentially into the separator 42. The static separator 42 is longer compared to the otherwise customary design, in that the ratio of diameter to height is about 1: 3, by a sufficient distance to separate solid and solution to obtain. The solids are discharged from the separator 42 via a vertical screw 54 and a horizontal screw 56

Drying the solids is a dryer, for example a

Hot air belt dryer ⁵ , ^{8 is} provided, from which the dried solids are discharged via a discharge 60. The internal structure of the plate heat exchanger 14 is shown schematically in FIG. 2. The vapor from the outlet line 36 is fed into the plate heat exchanger 14 through line 70 and exits the plate heat exchanger through line 72. The waste water or the concentrated solution is fed into the plate heat exchanger via line 74 and leaves the plate heat exchanger via line 76. Between the lines, plates 80, 82, 84, 86, 88, 90 are shown, the following channels for the waste water or form the vapor: the channels between plates 80 and 82, plates 84 and 86 and plates 88 and 90 carry the vapor or vapor condensate, while the channels between plates 82 and 84 and plates 86 and 88 carry the waste water or lead the concentrated solution. As shown by the arrows in Fig. 2, the waste water always flows from bottom to top through the plate heat exchanger 14, while the vapor always flows from top to bottom through the plate heat exchanger 14. Appropriate seals and inlet or outlet openings in lines 70, 72, 74 and 76 form two flow path systems in a manner known per se, which are completely separate from one another. Finally, the plate embossments of the plates are schematically indicated by hatching in FIG. 2. By these embodiments, the plates of the waste water is produced due to the high flow rate through the respective channels exceptionally high flow turbulence (Reynolds number R _e> 2000) so as to flush out the channels from the solution entrained solid components.

The inflow of waste water into the circuit is regulated by a control device which consists of a level controller 92 on the tangential separator 16 and a valve 94 at the mouth of the connecting line 12 in the circulation circuit. The level controller 92 senses the liquid level in the tangential separator 16 and opens the valve when the liquid level falls below a predetermined value, so that wastewater is replenished. In order to regulate the temperature of the vapor which is fed into the plate heat exchanger 14, a temperature control device is provided which consists of a temperature controller 96 and a valve 98 which is located in a water supply line 100 leading to the drain line 36. The vapor leaves the tangential separator 16 at a temperature of approximately 100 °, is brought to a temperature of approximately 160 ° C. in the vapor compressor 34 and regulated back down to approximately 120 ° C. by the temperature control device.

In order to regulate the repulsion of the mixture of solution and solids from the circulation circuit, a density control is provided, which consists of a density controller 102 on the solution chamber 50 of the separator 42 and a valve 104 which is located in the inflow line 44. The inflow into the separator 42 is regulated by the density control device as a function of the density of the solution in the separator 42, the density in the solution chamber of the separator 42 being regulated to approximately 1.25.

Finally, a live steam inflow control device is provided, which has a flow controller 106 at the vapor condensate outlet 40 and a valve 108 in a live steam supply line 110 which opens into the line 36. This control device serves to reduce the supply of live steam which is necessary when the device starts up, if the supply of vapors from the vapour compressor 34 is sufficient to operate the plate heat exchanger 14. In other words, the live steam supply is throttled when the vapor condensate flows sufficiently.

The device described above works as follows. When the device starts up, the circulating circuit is filled with waste water, and live steam is fed via line 110 to the plate heat exchanger 14. The wastewater heated in the plate heat exchanger 14 rises via the riser 20 into the tangential separator 16, where evaporation takes place through expansion. The riser has the purpose to generate a back pressure of about 6 m water column in the plate heat exchanger 14, so that bubble formation in the plate heat exchanger 14 is prevented. The solution is circulated and evaporated in the circulation circuit until the desired density of about 1.25 is reached. This corresponds approximately to a ratio of 1: 5 of the solids content to the solution content in the mixture, which is still flowable in this ratio. The density is initially determined by taking samples through valve 28 and line 26. When the desired density is reached, a mixture of solution and solids is delivered to the separator 42 via the inflow line 44, and from then on the density control device takes over control of the repulsion of the mixture of solution and solids from the circulation circuit. After the start-up phase, the density control device and the level control device establish an equilibrium, since the evaporation capacity of the system is correspondingly high. The evaporation capacity is dimensioned such that the maximum evaporation capacity is equal to the feed-in capacity that the user of the device demands. For example, if the user requires the device to process 10 tons of water per hour, the maximum evaporation capacity is dimensioned to 10 tons of water per hour. However, since the solution contains not only the solution components but also the solid components, more than 10 t of waste water are processed per hour. The level control device ensures that the liquid circuit in the system is constantly maintained, so that there is continuous operation if the interplay between the repulsion of solution and solids from the circulation circuit and the feeding of wastewater has been repeated at ever decreasing intervals, until a state of equilibrium is established with the density of the solution in the solution chamber 50.

This process removes the pollutants one after the other through an uncontrolled crystallization from the wastewater solution separated. First, the solid components are separated, the substances of which have a low solubility and / or a high concentration in the solution. The solid components, which due to their too small amount or too great solubility do not yet precipitate out, remain in the device until they are sufficiently enriched in the solution that they also precipitate out. Therefore, all pollutant components are finally separated.

Claims

Process and device for cleaning wastewater patent claims

1. A process for the purification of waste water, which has a solution with pollutants which can be separated off by crystallization and precipitation, characterized in that the solution in a circulating circuit by means of a heat exchanger in which only the heat exchange takes place to achieve the evaporation temperature, then by a separator, in which the evaporation takes place by expansion of the solution, and is then passed back into the heat exchanger, and that the solid matter, which are obtained when the solution is concentrated, are withdrawn from the circulation circuit.

2. The method according to claim 1, characterized in that a back pressure is generated between the separator and the heat exchanger to prevent bubble evaporation in the heat exchanger.

3. The method according to claim 1, characterized in that the solids are withdrawn from the circulating circuit in that the mixture of the solution and the solids is led out of the circulating circuit through a bypass line, and in that the solids from the mixture in a second Separator separated by the B pass line and the solution the circulation circuit is returned.

4. The method according to claim 3, characterized in that the outflow of the mixture from the circulation circuit into the bypass line is controlled depending on the density of the solution in the second separator.

5. The method according to claim 1, characterized in that the vapors flowing out of the first separator brought to a higher pressure and a higher temperature and the heat exchanger as heat energy, which is required for the evaporation process, is supplied.

6. The method according to claim 5, characterized in that the vapors are brought to a higher pressure and temperature level by compression.

7. Device for the purification of waste water, which has a solution with pollutants that can be separated off by crystallization and precipitation, characterized by a heat exchanger (14) in which only the heat exchange takes place to reach the evaporation temperature, a separator (16) connected downstream of the heat exchanger (14) ), in which the evaporation takes place by expansion of the solution, by a separation device for separating the solids from the mixture of the concentrated solution and the solids, and by a device for returning the solution to the heat exchanger (14).

8. The device according to claim 7, characterized in that the heat exchanger (14) is a plate heat exchanger with only rising film.

9. The device according to claim 8, characterized in that the plates of the plate heat exchanger (14) have a plate embossing to achieve increased turbulence in the solution flowing through.

10. The device according to claim 7, characterized in that the separating device has a second, in a bypass line (44, 48) arranged separator (42).

11. The device according to claim 10, characterized in that the bypass line has an inflow line (44) to the second separator (42) which branches off from the circulation circuit after the first separator (16), and a solution drain line (48) from the second Has separator (42) to the circulation circuit, which opens into the circulation circuit between the branch of the inflow line (44) and the heat exchanger (14).

12. The apparatus according to claim 7, characterized in that the first separator (16) is a tangential separator.

13. The apparatus according to claim 10, characterized in that the second separator (42) is a static separator.

14. The apparatus according to claim 7, characterized by a vapor compressor (34), the inlet line (32) with the vapor outlet (30) of the first separator (16) is connected, and the outlet line (36) with the steam inlet (38) of the heat exchanger ( 14) is connected.

15. The apparatus according to claim 7, characterized by a level control device with a level controller (92) on the first separator (16) and a valve (94) in the connection line (12) provided for the waste water supply, the waste water inlet depending on the level in the first separator (16) is regulated.

16. The apparatus according to claim 14, characterized by a Temperaturregeleinrichtüpg with a temperature controller (96) on the drain line (36) of the vapor compressor (34) and a valve (98) which lies in a water supply line (100) leading to the drain line, the Temperature of the compressed vapors is regulated by water supply.

17. The apparatus according to claim 7, characterized by a density control device with a density controller (102) on the second separator (42) and a valve (104) in the inflow line (44) to the second separator (42), the inflow to the second Separator (42) is regulated depending on the density of the solution in the second separator (42).

18. The apparatus according to claim 13, characterized by a live steam inflow control device which has a flow controller (106) at the vapor condensate outlet (40) of the heat exchanger (14) and a valve (108) in a live steam supply line to the steam inlet of the Has heat exchanger (14), the live steam supply to the heat exchanger (14) being regulated as a function of the flow of vapor condensate.