WO2013060712A1

WO2013060712A1 - Method and apparatus for treatment of effluent accumulating in a desalination plant

Info

Publication number: WO2013060712A1
Application number: PCT/EP2012/071029
Authority: WO
Inventors: Frederick Simon Oosthuizen
Original assignee: Frederick Simon Oosthuizen
Priority date: 2011-10-24
Filing date: 2012-10-24
Publication date: 2013-05-02
Also published as: IN2014DN03260A; ZA201402874B; DE102011116699A1

Abstract

The procedure for treatment of effluent first cools the effluent (10) to form a pumpable ice-effluent-concentrate mixture that is subsequently fed to a filter device (13), in which the ice (14) is separated from the concentrate (18), and the ice and/or concentrate are used for heat exchange to precool the effluent.

Description

Process and apparatus for the treatment of waste water from a desalination plant

description

The invention relates to a process for the treatment of wastewater or concentrate as residue of membrane technologies for desalination and to an apparatus for carrying out this process. Typical application of a reverse osmosis system is, for example, the desalination of brackish water, river water and seawater. Desalination is the only way to produce drinking water in many arid regions of the world. In reverse osmosis liquid is concentrated with solutes to z. B. drinking water to win. During the process, a partial stream of clean water and a partial stream of wastewater, in which the solutes concentrate, are separated by means of a membrane. The ratio between the clean partial flow and the wastewater partial flow is typically between 1: 2 and 1:10 and depends on the specific performance of the plant and the chemical composition of the water to be purified. The wastewater contains all pollutants that are in the water to be purified. Typically, the wastewater is contaminated with chlorides, sodium and / or potassium and calcium salts. However, the resulting wastewater can also be contaminated with heavy metals, pesticides, drug residues and other pollutants.

One aim of the method is to create an economical method with as little as possible susceptible installation technology and corresponding procedure-specific devices.

The wastewater with corresponding solutes such as chlorides and / or potassium and calcium salts is typically a highly corrosive liquid. The corrosiveness increases with increasing Temperature of the liquids and it is to be expected with scale deposits. A suitable heat exchanger design is therefore necessary and a prerequisite for reliable operation. This is inventively designed as a cylindrical double-jacket heat exchanger with mechanical scraper system.

The invention has for its object to provide a freezing process that allows cost-effective treatment of wastewater. The aim is to clean the wastewater without pre- and post-treatment. Another goal is to win the ice as pure water without, for example, fresh water being needed for washing.

Attempts to develop such a method have so far failed. An important reason, which has often led to failure, was the attempt to wash ice crystals with fresh water. This approach is fundamentally in conflict with the goal of preparing water, d. H. to clean. The following is the basic representation of the process without the use of chemical additives:

1 . The wastewater is cooled in a chiller. The chiller has one or more cylindrical double-jacket heat exchangers as evaporators, equipped with mechanical

Thermoplastic scraper. Cooling creates a pumpable, liquid ice / concentrate mixture.

2. The ice is filtered, separating the concentrated wastewater filtrate from the ice residue. The ice residue and / or the wastewater filtrate are used to pre-cool the water to be treated as an essential process step.

3. The waste heat of the refrigerant circuit is used by means of a cylindrical double-jacket heat exchanger with mechanical Thermoplastschaber system as a condenser, ie as a condenser. 4. The heated wastewater filtrate is fed to a vacuum evaporator, wherein pollutants are separated in the vacuum evaporator and condensed water is recovered.

The invention is thus based on the idea to use a chiller for working up the wastewater of a membrane process. The use of the generated cold as well as the heat of the refrigerators is an integral part of the treatment process. The generated latent cooling capacity in the form of ice is used to pre-cool the wastewater to be treated.

The generated cooling capacity is merely a waste product, which is returned to the process as directly as possible.

The use of the resulting waste heat of the refrigeration circuit is an essential process step, which greatly influences and increases the efficiency of the overall process.

One of the highest goals of the water treatment industry is cost effective water treatment. This claim is also reflected in the design of the heat exchanger for pre-cooling of the current to be treated.

According to the invention, the problem is solved by collecting the resulting ice and by collecting the concentrate in basins, equipped with a simple plastic tube as a heat exchanger. Another goal is to use the heat generated from the refrigeration process.

According to the invention this is achieved by the use of a double-jacket heat exchanger with rotating, mechanical scraper in heat pump operation. Due to the rotating thermoplastic scraper a possibly scale deposit is prevented. The then heated concentrated wastewater filtrate is then fed to a vacuum evaporator. The evaporation of liquids is usually expensive, since the amount of energy to be applied to the phase change is high. The basic idea is to cover this energy demand with the energy generated in the process and the use of an additional heat source such. B. to avoid a heat pump. This would mean further investment and operating costs.

By using the process heat from the cooling process, the performance of the evaporator depends on the operating condition and the nominal size of the chillers.

Feature of the invention is the use of a double-jacket heat exchanger with mechanical thermoplastic scraper first as an evaporator and secondly in a similar form as a condenser in a refrigerator. A preferred device is described in the application 10 2010 020 908.2.

Ice crystals are formed in the evaporator. These are removed with a rotating scraper mechanism continuously from the inner wall of the double mantle.

In the condenser, the rotating scraper mechanism is inserted along the inner wall to prevent scaling and thus to ensure that the heat exchanger performs optimally in continuous operation.

A feature of the method is the use of the heat generated by a chiller for the evaporation of already concentrated wastewater. Another feature is the use of the resulting ice for cooling in an evaporation process. An important step in the process is to extract clean ice in a suitable filter device. In the filter device, the concentrated wastewater filtrate is separated from the ice. According to the invention, this is achieved by a cylindrical double-jacket filter.

The inner tube is preferably made of plastic, the outer tube preferably made of metal or stainless steel. In the middle of the inner tube is a filter element, in which the concentrated sewage filtrate flows downwards, this process can be supported by a pump. As a pump, a diaphragm pump is preferably used. In the inner tube, ice / concentrate mixture is continuously pumped upwards, resulting in the formation of an ice column whose moisture steadily decreases with height.

Above this, in the center of the double-jacket filter, there is an ice-cutting device consisting of at least three cutting blades, each of which is equipped with a vertically arranged cutting plate and a discharge plate. The blades are preferably curved and ensure a clean cutting or cutting of the ice through a slender Schneideblechkonstruktion.

The extraction of clean water without the use of fresh water is a key feature of the process. According to the invention this is achieved by the construction of several filter devices, which are preferably connected in parallel and are operated sequentially.

As a first step in the first filter, the ice / concentrate mixture is compressed to the extent that an ice column is formed.

If the ice column has grown just below the ice cutter, the supply of the ice / concentrate mixture in the first filter is stopped and passed to the next and the following filter and ff. This filter device is used as an intermediate ice sheet, in which the ice column is further separated from the waste water concentrate and dried. The landfill duration is the control variable of the purity of the ice. The longer the life, the cleaner the water. If the supply of ice / concentrate mixture stopped, the ice column falls down, the water content is drained from the ice and container. In this case, by gravity and coalescence, a further separation of the liquid waste water concentrate from the solid ice.

The basic idea of the process for the treatment of waste water is to cool the waste water to a pumpable ice-sewage concentrate mixture and subsequently feed this to a filter device in which the ice is separated from the concentrate. According to the invention, the ice and / or the concentrate is used in heat exchange for pre-cooling of the wastewater.

Advantageously, the concentrate is heated in a heat exchanger and subsequently fed to a vacuum evaporator, wherein the heat exchanger is heated with the waste heat of the cooling process, which is used for cooling the waste water to the ice-waste concentrate mixture. To condense the water vapor generated in the vacuum evaporator, the ice / water and / or the concentrate is used in heat exchange. In this case, the ice / water and / or the concentrate, which is used in heat exchange for condensing the water vapor generated in the vacuum evaporator, advantageously before used in heat exchange for pre-cooling of the wastewater.

The wastewater is z. As to wastewater from a desalination plant, but it can be treated with the inventive method basically any water-based wastewater. It is particularly advantageous if the wastewater is cooled in a cylindrical jacketed heat exchanger with a rotating mechanical scraper to the ice-waste concentrate mixture and the concentrate is heated in a cylindrical double heat exchanger with a rotating mechanical scraper device, the double-jacket heat exchanger, for cooling the waste water is determined, forms the evaporator of a cooling circuit, the condenser is formed by the double-jacket heat exchanger for heating the concentrate. Such an arrangement is energetically favorable and particularly advantageous because of the self-cleaning effect by the scraper devices.

The inventive apparatus for the treatment of wastewater, in particular a desalination plant, therefore, has a cylindrical double-jacket heat exchanger with a rotating mechanical scraper device as an evaporator, which is connected on the one hand with a cooling circuit and on the other hand input side with a waste water-carrying line and the output side with a filter device , In the filter device, ice is separated from the waste water concentrate. The wastewater-carrying input line of the double-jacket heat exchanger is preceded by a heat exchanger whose other side is line connected to an output of the filter device, in order to pre-cool the wastewater before it enters the double-jacket heat exchanger.

The filter device advantageously has a plurality of filter stages connected in series. The double-jacket heat exchanger are advantageously preceded by two heat exchangers, wherein the one heat exchanger with the ice leading output of the filter device is conductively connected and the another heat exchanger is conductively connected to the concentrate output of the filter device so as to utilize both the ice and the cooled concentrate for pre-cooling the waste water introduced into the system.

The concentrate leading heat exchanger is advantageously connected to a second heat exchanger and subsequently connected to a vacuum evaporator. In this case, the heat exchanger connected to the wastewater-conducting inlet line of the double jacket heat exchanger is formed by a basin, through which a pipeline z. B. meandering or helical is performed. The plastic pipeline carries the waste water, whereas in the pool the ice / water from the filter or in another basin the cooled concentrate is located.

Advantageously, the second heat exchanger forms the condenser of the cooling circuit, wherein the second heat exchanger is advantageously designed as a cylindrical double-jacket heat exchanger with rotating mechanical scraper device and the scraper concentrate is arranged on the concentrate side, to the adhesion of scale or other precipitated salts and deposits from the concentrate avoid. In order to condense the evaporated water in the vacuum evaporator, a heat exchanger is advantageously provided which is on the one hand connected to the ice / water leading output of the heat exchanger for pre-cooling of the waste water and on the other hand thermally connected to the steam side in the vacuum evaporator.

The invention will be explained below with reference to drawings. Showing:

1 is a schematic flow diagram of an embodiment of the method, 2 shows a heat exchanger device for precooling the incoming wastewater to be cleaned, FIG. 3 shows a double-jacket heat exchanger with a mechanical thermoplastic scraper,

Fig. 4 shows a filter device, which concentrated the

Wastewater filtrate separated from ice and

Figure 5 is a schematic flow diagram of one embodiment of the filtering process for obtaining ice as a clean source of water without the use of fresh water to wash the ice.

In the exemplary embodiment illustrated in FIG. 1, the wastewater 10 is pumped from a desalination plant by means of a pump 11 over the ice basin 15 and the concentrate basin 20 into one or more cylindrical double-jacket heat exchangers as evaporators with mechanical scrapers 12.

In the double-jacket heat exchanger, the liquid ice / concentrate mixture is formed. This is then passed on to a filter 13. In the filter 13, the concentrated sewage filtrate 18 is separated from the ice 14.

The ice 14 is deposited in an ice basin 15. In the ice basin 15 is a plastic hose coil 1 6, through which the incoming wastewater 10 is passed. This device serves the purpose of pre-cooling the incoming waste water 10 by existing latent cooling energy in the form of ice 14 or molten ice (water).

The concentrated wastewater filtrate 18 is preferably sucked out of the filter 13 with a membrane pump 19. The concentrated wastewater filtrate 18 is deposited in a concentrate tank 20. In this is a plastic hose coil 21 corresponding to the Principle of the ice basin 15. Again, the device serves the purpose of precooling.

The heated concentrate 18 is supplied by means of a pump 22 from the concentrate tank 20 to the vacuum evaporator 25. The evaporation vessel receiving the concentrate is under vacuum and is heated by a circulation stream via the heat exchanger 23, which consists of at least one double jacket heat exchanger with mechanical scraper and acts as a condenser in the connected cooling process 24.

The vacuum required for evaporation at a low temperature level is preferred and typically generated using the condensate as the propellant by a jet pump. The purified product water 29 condenses in the pump on the propellant jet and is directly available for further use.

The meltwater accumulating in the ice basin 15 is conducted by means of a pump 26 for condensate cooling through heat exchanger 27 in the vacuum evaporator 25 and then discharged as treated product water 28.

Dissolved substances contained in the incoming wastewater 10 are precipitated as solids in the evaporation tank 25 and discharged via a pump 30.

2 shows a heat exchanger device 40 for depositing both ice and concentrated wastewater filtrate. Preferably, the basin 41 is made of plastic or concrete and integrated a plastic spiral 42 for the use of energy recovery.

This design allows a cost-effective and easy to implement heat exchanger.

3 shows the embodiment of a double-jacket heat exchanger 80, via a refrigerant inlet 82 and a cold jacket. With the † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † † This double-jacket heat exchanger construction is used on the one hand as an evaporator 12 and on the other hand as a condenser 23 in the refrigeration process 24. Inside the double-jacket heat exchanger 80 there is a rotor construction 81 with a mechanical scraper 83.

The mechanical scrapers made of thermoplastic are pressed by means of silicone pins 84 to the inner wall of the double jacket. The illustration Fig. 4 shows a possible embodiment of a filter device 50 with a metal outer tube 53 and a plastic inner tube 52, in which the filter element 51 is mounted centrally.

The ice / concentrate mixture is fed to the filter via a port 54 via a pump. The upper end of the filter device 50 forms the cover 58, in which, arranged centrally, an ice cutting device 55 is located. Shown is a possible embodiment of the ice cutting device with three curved cutting blades 56 with corresponding ejection plates 57. The cutting device 55 is driven by a gear motor 59, characteristic is also a tangential ice ejection, possibly similar pos. 60th

Fig. 5 shows an embodiment of the filtering method for obtaining ice as a product water source. If the ice / concentrate mixture is pumped via the supply line 60 into the first filter 63 via the line 61, the valve 62 is opened, the valves 66 and 70 of the further filters 67 and 71 are closed and thus the supply is blocked.

The waste water concentrate is pumped out continuously via the diaphragm pump 64. When the ice column has almost reached the ice cutter 55, the valve 62 closes and inhibits the supply of further ice / concentrate mixture. The valve 66 opens and the ice / concentrate mixture is pumped via line 65 into the second filter. The waste water concentrate is pumped off via the diaphragm pump 68. If, as in the first filter, the ice column has grown as far as the ice cutting device, valve 66 also closes. At the same time, valve 70 opens and the third filter is filled with the ice / concentrate mixture via line 69.

The waste water concentrate is pumped off via the diaphragm pumps 68 and 72. The removal of the concentrated wastewater takes place via line 73. After filling filter 71, the circuit closes and the ice / concentrate mixture is supplied via line 61 and the re-opened valve 62 to the first filter 63. The existing ice column is pushed upwards and harvested via the ice cutter. The duration of the ice deposition is the central standard of ice purity.

LIST OF REFERENCE NUMBERS

10 - incoming wastewater

1 1 - pump

12 - Double jacket heat exchanger (evaporator) 13 - Filter

14 - ice cream

15 - Ice basin

1 6 - Plastic hose spiral

18 - concentrated waste water filtrate (concentrate) 19 - membrane pump

20 - concentrate basin

21 - Plastic hose spiral

22 - pump

23 - Double jacket heat exchanger (condenser) second heat exchanger

24 - refrigeration process

25 - Vacuum evaporator

26 - Pump

27 - Heat exchanger

28 - product water

29 - product water

30 - pump

40 - heat exchanger device

41 - Basin

42 - plastic spiral

43 - Line input

44 - Line output

50 - Filter device

51 - Filter element

52 - plastic inner tube

53 - Metal outer tube

54 - Connection

55 - Ice cutting device

56 - cutting blades

57 - ejection plates

58 - cover ,,

14

59 geared motor

60 tangential ice ejection

61 line

62 valve

63 filters

64 diaphragm pump

65 line

66 valve

67 filters

68 diaphragm pump

69 line

70 valve

71 filters

72 diaphragm pump

73 line

80 double jacket heat exchanger

81 rotor construction

82 refrigerant inlet

83 refrigerant leakage

84 silicone pens

Claims

claims

Process for the ripening of waste water, in which the waste water (10) is cooled to a pumpable ice-waste concentrate mixture, which is subsequently fed to a filter device (13), in which the ice (14) is separated from the concentrate (18) characterized in that the ice (14) and / or the concentrate (18) is used in heat exchange for pre-cooling of the waste water (10).

A method according to claim 1, characterized in that the concentrate is heated in a second heat exchanger (23) and fed to a vacuum evaporator (25), wherein the heat exchanger (23) with the waste heat of the cooling process (24) is heated, for cooling the waste water (10) is used to the EisWwasserkonzenfratgemisch.

A method according to claim 1 or 2, characterized in that for condensing the water vapor generated in the vacuum evaporator (25), the ice / water and / or the concentrate is used in heat exchange.

A method according to claim 3, characterized in that the ice / water and / or the concentrate, which is used in the heat exchange for condensing the steam generated in the vacuum evaporator (25), previously used in heat exchange for pre-cooling of the waste water (10).

5. The method according to any one of the preceding claims, characterized in that it is the waste water (10) is wastewater from a desalination plant.

Method according to one of the preceding claims, characterized in that the waste water (10) is cooled in a cylindrical double-jacket heat exchanger (12) with a rotating mechanical scraper to the ice-waste concentrate mixture and that the concentrate (18) in a cylindrical double-jacket heat exchanger (23) is heated with a rotating mechanical scraper device, wherein the double-jacket heat exchanger (12), which is intended for cooling the waste water (10), the evaporator of a cooling circuit (24) forms, the condenser through the double-jacket heat exchanger (23) for heating the concentrate (18) is formed.

Apparatus for the treatment of wastewater (10), in particular a desalination plant, comprising a cylindrical jacketed heat exchanger (12) with a rotating mechanical scraper device as evaporator which is conductively connected on the one hand to a cooling circuit (24) and, on the other hand, on the inlet side to a conduit carrying waste water and on the output side with a filter device (13) is line connected, in which ice (14) of waste water concentrate (18) is separated, characterized in that the double-jacket heat exchanger (12) on its wastewater-carrying input line at least one heat exchanger (15, 16; 20, 21) is connected upstream, whose other side is conductively connected to an output of the filter device (13).

8. Apparatus according to claim 7, characterized in that the filter device (13) has a plurality of filter stages connected in series.

Device according to one of the preceding claims, characterized in that the two-jacket heat exchanger (12) two heat exchangers (15, 16, 20, 21) are connected upstream, wherein the one heat exchanger (15, 16) with the output leading to the ice (14) the filter device (13) is conductively connected and the other heat exchanger (20, 21) with the concentrate (18) leading output of the filter device (13) is conductively connected.

Device according to one of the preceding claims, characterized in that the concentrate (18) leading heat exchanger (20) with a second heat exchanger (23) and subsequently with a vacuum evaporator (25) is conductively connected.

Device according to one of the preceding claims, characterized in that the heat exchanger connected to the wastewater-carrying input line of the double-jacket heat exchanger (12) comprises a basin (15, 20) and a pipeline (16, 21) leading through the basin.

12. The device according to claim 1 1, characterized in that the basin (15, 20) made of concrete and the pipe (16, 21) consists of plastic.

13. Device according to one of the preceding claims, characterized in that the second heat exchanger (23) forms the condenser of the cooling circuit (24). Apparatus according to claim 13, characterized in that the second heat exchanger (23) is designed as a cylindrical double-jacket heat exchanger (23) with rotating, mechanical scraper concentrate side.

Apparatus according to claim 13 or 14, characterized in that the vacuum evaporator (25) has a heat exchanger (27), on the one hand with the ice / water leading output of the heat exchanger (15, 1 6) conduction connected to the pre-cooling of the wastewater and on the other hand thermally connected to the steam side in the vacuum evaporator (25).