WO2015185136A1

WO2015185136A1 - System and method for conditioning a washing liquid

Info

Publication number: WO2015185136A1
Application number: PCT/EP2014/061638
Authority: WO
Inventors: Mark REDMANN
Original assignee: Dr.-Ing. K. Busch Gmbh
Priority date: 2014-06-04
Filing date: 2014-06-04
Publication date: 2015-12-10

Abstract

The invention relates to a system and to a method for conditioning a washing liquid from a washer for a plastic processing plant, wherein the washing liquid is conducted from a washing tank (2) into a centrifugal unit (11) through a first line section (9) from the washing tank (2) to the centrifugal unit (11), wherein there is an operating pressure p₀ in the washing tank (2). Upon transitioning, the pressure in the washing liquid is increased to a pressure p1 which is present in the centrifugal unit (11) and which is higher than the operating pressure p₀. By means of the centrifugal unit (11), contaminants are separated from the washing liquid and the washing liquid is conveyed back from the centrifugal unit (11) to the washing tank (2) through a second line section (10).

Description

System and method for treating a washing liquid

The present invention relates to a system and a method for treating a scrubbing liquid from a scrubber, in particular for the treatment of a scrubbing liquid when washing a medium such as gas or steam from a plastics processing plant.

The continuous processing of plastics is in many cases in processing units, in which liquid or solid plastics are supplied. The processing of plastics within the processing units releases gaseous substances, the z. As a degradation product of the plastic, hydrocarbons, solvents from the manufacturing process and substances such as water or air escape. To stabilize the production process and to reproduce the production parameters, a vacuum, i. H. a negative pressure, applied to degassing zones of the processing units and the gaseous substances are passed through a gas scrubber. The gas scrubber has a scrubbing liquid which is injected into the substances which are thereby purified. In the washing process, condensable and crystallizable gas components are separated from the substances and deposited in the washing liquid. Depending on the substances to be washed, different washing media are used. The washing media can z. B. be cleaned in a treatment system with a closed circuit for the washing media. For processing z. B. filters are used.

From the technical field of internal combustion engines for vehicles or shipping, emission control systems are known which use centrifuges for cleaning exhaust gases from the internal combustion engines. In EP 2364760 A1 is z. For example, a system is shown in which an exhaust pipe passes through a scrubber with washing liquid, whereby the exhaust gas is treated. The scrubber may be connected to a reservoir for the scrubbing liquid so that the scrubbing liquid is pumped from the reservoir through the scrubber and back into the reservoir. A treatment circuit for the treatment of the washing liquid has a Zentrifugeabscheider, in which the washing liquid is pumped out of the scrubber. Out the separator, the treated washing liquid is returned to the reservoir or directly back into the scrubber. The washing liquid can be pumped by a pump of the centrifuge or a separate pump in the scrubber. In this system, the treated scrubbing liquid from the treatment circuit can be mixed with the contaminated scrubbing liquid from the scrubber in the reservoir. The scrubber supplied washing liquid therefore has a low degree of purity. Furthermore, additional pumping units are required, or the Zentrifugenabscheider must be designed according to the required pump power. Such a system is not very suitable for washing media, as they are used for the purification of gas-vapor mixtures from the plastics processing.

It is the object of the present invention to provide a system and a method for treating a scrubbing liquid from a scrubber, which are suitable for use in the washing of gas or steam from a plastics processing plant, require low design effort, work reliably and can be operated energy-saving ,

This object is achieved by the invention by a system and a method for treating a washing liquid according to claims 1 and 10. Furthermore, the object is achieved by a plastics processing system according to claim 14. Advantageous embodiments and embodiments are described in the dependent claims.

A scrubber scrubbing system according to the invention comprises a scrubbing tank with scrubbing liquid, a centrifuge unit for scrubbing contaminants from the scrubbing liquid, and a conduit loop in which scrubbing liquid is passed from the scrubbing tank to the centrifuge unit and back into the scrubbing tank. The wash tank can be part of the scrubber. The scrubber may include other units, such as a reservoir for additives, a packed bed, and the like. The washing liquid may be a low-viscosity medium, such as oils and glycols (mono-, di- or triethylene glycol), or else water. Depending on the medium to be washed and the holding impurities and substances, a suitable washing liquid is selected. Essentially, the conduit loop forms a closed loop in which the wash liquid can be used over several cycles.

According to the invention, there is an operating pressure p ₀ in the wash tank and a pressure pi in the centrifuge unit which is higher than the operating pressure p ₀ . This results in the line section of the line circuit from the centrifuge unit to the wash tank a pressure drop, so that the washing liquid can be injected into the wash tank. For the return of the washing liquid essentially no further components in the line circuit are required. In a variant of the treatment system, therefore, no control units for regulating the flow of the washing liquid are provided in the line section from the centrifuge unit to the wash tank. In another variant, in this line section, a control unit, for. B. in the form of a throttle, be provided to regulate the injection quantity of washing liquid in the wash tank. For example, it is advantageous to synchronize the injection quantity into the wash tank with the feed quantity into the centrifuge unit. In both variants, an operating pressure p ₀ is present in the wash tank and a pressure pi in the centrifuge unit which is higher than the operating pressure p ₀ .

According to the process for treating a scrubbing liquid from a scrubber with such a treatment system, an operating pressure p ₀ is therefore applied in the scrubbing tank. The washing liquid is transferred from the wash tank of the scrubber through a first line section from the wash tank into the centrifuge unit. When passing the pressure in the washing liquid is increased to a pressure pi, which rests in the centrifuge unit and is higher than the operating pressure p ₀ . In the centrifuge unit, the deposition of impurities and undesired substances from the washing liquid takes place. The recycled washing liquid is returned from the centrifuge unit to the wash tank through a second line section extending from the centrifuge unit to the wash tank by the increased pressure p-, compared to a pressure p ₂ applied in the second line section. in the centrifuge unit. In the second Line section is advantageously a pressure p ₂ less than the pressure p-, the centrifuge unit, so that the treated washing liquid is sucked out of the centrifuge unit. Advantageously, the pressure p ₂ , the operating pressure p ₀ , as it is present in the wash tank. Thus, the washing liquid can be directed to save energy without the use of other active drive devices in the wash tank.

In a variant, the system for treating a washing liquid in the first line section of the line circuit from the wash tank to the centrifuge unit comprises a pressure generator, for. B. in the form of a pump on, in the washing liquid the pressure p- generated. Furthermore, the treatment system can be connected to a vacuum generator, generally referred to as a vacuum generator, to which in turn the wash tank for generating the operating pressure p _{0 is connected} in the wash tank.

Advantageously, a vacuum generator is used, as it is used in a plastics processing plant, to aspirate a medium to be washed from a processing unit of the plant in which the gas is formed. The medium to be washed can be sucked out of the processing unit by a discharge at the operating pressure p ₀ . The treatment system, in particular the wash tank of a scrubber, is connected to the vacuum generator, z. B. the system is provided in the derivative, so that the operating pressure p _{0 is} also present there. Thus, the treatment system according to the invention does not require its own pressure generator, but can use the vacuum generator of the plant, from which the medium to be washed comes.

An efficient operation of the treatment system is achieved when a pressure difference is at least 700 mbar. In a preferred embodiment of the treatment system in combination with a plastics processing plant, an operating pressure p ₀ in the range of 0.5-300 mbar, particularly preferably in the range of 1 .0 - 100 mbar, driven. The temperature of the washing liquid is in the range of -15 ° C to 60 ° C and is adjusted to the washing liquid used. The pressure p- in the centrifuge unit preferably corresponds to an atmospheric ambient pressure of the treatment system. Thus, there is no need to make provision for maintaining a pressure different from the ambient pressure in the centrifuge unit.

In a variant of the treatment system according to the invention, the centrifuge unit comprises at least one, but preferably two or more, centrifuges which are fed by the first line section coming from the wash tank. The design of the centrifuges is z. B. matched to the type of washing liquid. Furthermore, the centrifuge unit may comprise a collecting container for collecting treated washing liquid. The collecting container may be connected to the second line section, wherein in the collecting container the pressure p-, the centrifuge unit is applied. The second line section with the pressure p ₂ or p ₀ adjoins the collecting container, so that the washing liquid is sucked out of it. The impurities and residues deposited in the centrifuges are discarded as usual from the centrifuges. Centrifuges with automatic cleaning can be used. By using two or more centrifuges, a continuous operation of the treatment system can be ensured.

According to a further aspect, the invention relates to a plastics processing plant with a system for the treatment of a washing liquid, as shown above. Advantageously, the treatment system is a module of the plastics processing plant, as well as the processing unit for the plastic, and uses the generation of a negative pressure to suck the media to be washed for the generation of the operating pressure p ₀ in the wash tank.

The invention has been illustrated by means of embodiments. The individual technical features of an embodiment may well be used in combination with another embodiment with the stated advantages. The description of the technical features according to the invention is therefore not limited to the respective embodiment. An advantageous embodiment of the invention is illustrated below with reference to the drawing, which is merely illustrative and not restrictive interpreted. Features of the invention which will become apparent from the drawing are to be considered individually and in any combination as belonging to the disclosure of the invention. In the drawing, Figure 1 shows a schematic representation of a system for the treatment of a washing liquid in combination with a plastics processing plant.

The system for the treatment of a washing liquid according to FIG. 1 is intended for the treatment of a washing liquid with which a gas-vapor mixture has been washed out of a processing unit 1 of a plastics processing plant. The gas-vapor mixture accumulates as contaminated exhaust gas in the processing of plastics in the processing unit 1 and is introduced via a discharge from the processing unit 1 in a washing tank 2 of the treatment system.

With the wash tank 2, a passage container 3 is connected, the lower region 4 is filled with a packed bed and disposed within the wash tank 2. The passage container 3 is permeable in the lower region 4 for the gas-vapor mixture, for example, this area is perforated. The upper region 5 has an outlet 6, possibly with a shut-off valve and a demister, or filter 8, on. At the outlet 6, a vacuum generator 7 closes. The washing tank 2 and the transit container 3 can be considered as scrubbers for the gas-vapor mixture.

The negative pressure generator 7 generates an operating pressure p ₀ to suck the gas-vapor mixture from the processing unit 1 through the washing tank 2 and the passage tank 3. In this case, the gas-vapor mixture flows through the washing liquid in the wash tank 2 and the Füllkörpermischung in the lower region 4 of the passage container 3, wherein an intense energy exchange with the washing liquid takes place. The gas-vapor mixture leaves the passage container 3 in the direction of the vacuum generator through the outlet 6. To the wash tank 2, a line circuit is connected, comprising a first line section 9 of the wash tank 2 to a centrifuge unit 1 1 and a second line section 10 of the centrifuge unit 1 1 back to the wash tank 2. The second line section 10 opens into the upper region 5 of the passage container 3. In the first line section 9, a stopcock 12 and a pump 13 is arranged.

The centrifuge unit 1 1 has two centrifuges 14 and 14 ', which are each fed by a supply line with a valve 15 and 15' through the first line section 9 with washing liquid. By means of the valves 15 and 15 ', the centrifuges 14 and 14' can be filled simultaneously or successively with washing liquid. In the flow direction behind the centrifuges 14 and 14 ', the centrifuge unit 1 1 has a collecting container 16, in which the washing liquid prepared in the centrifuges 14 and 14' is collected. From the collecting container 16, the second line section 10 of the line circuit goes off.

In operation, an operating pressure p _{0 is} generated by the suction of the gas-vapor mixture from the processing unit 1 by the vacuum generator 7 in the wash tank 2, which is below the pressure applied in the region of the processing unit 1. The operating pressure p ₀ is below the ambient atmospheric pressure and thus forms a vacuum, which by definition is to be understood as vacuum any pressure below the ambient pressure. Preferably, the operating pressure p _{0 is} at an absolute pressure between 1 .0 and 100 mbar. The operating pressure p ₀ in the wash tank is thus given by a suction pressure with which a gas-vapor mixture to be washed or another medium is sucked through the wash tank.

For the treatment of the washing liquid in the wash tank 2, this is sucked through the first line section 9 by means of the pump and to a pressure p-, brought, which is higher than the operating pressure p ₀ , preferably to the ambient pressure. With this pressure p-, the washing liquid is introduced into the centrifuge unit 1 1, which also has the pressure p-. In the centrifuge unit 1 1, the washing liquid is introduced into one or both of the centrifuges 14 and 14 '. In centrifuges 14 and 14 ', impurities are from the washing liquid in a conventional manner. The treated washing liquid flows freely into the collecting container 16.

In the second line section 10 is a pressure p ₂ , which is smaller than the pressure p-, the centrifuge unit, preferably, the pressure p ₂ corresponds to the operating pressure p ₀ in the wash tank 2, or in the passage tank 3. By this pressure difference between the Centrifuge unit 1 1 and the line section 10, the treated washing liquid is sucked into the second line section 10 and fed into the wash tank 2. In the upper region 5 is at a low flow rate and the demister, or filter 8 prevents carryover of the washing liquid.

In summary, in the illustrated plastics processing plant in the processing unit 1, a medium to be washed, such as the gas-vapor mixture, is produced. The vacuum generator 7 sucks the medium to be washed from the processing unit by a discharge at an operating pressure p ₀ . The washing tank 2 and thus the system for the treatment of the washing liquid is provided between the processing unit 1 and the vacuum generator 7. As a result, the pressure generation of the vacuum generator can be used for the treatment system and at the same time the vacuum generator can be operated fail-safe.

reference numeral

Processing unit 9 first line section

Wash tank 10 second line section

Passage container 1 1 centrifuge unit lower portion 12 stopcock

upper section 13 pump

Outlet 14, 14 'centrifuge

Vacuum generator 15, 15 'valve

Filter 16 collection containers

Claims

claims

1 . A system for treating a scrubbing liquid from a scrubber comprising:

a wash tank (2) with washing liquid,

- A centrifuge unit (1 1) for the separation of impurities from the washing liquid and

- A conduit circuit (9, 10), in the washing liquid from the wash tank (2) to the centrifuge unit (1 1) and back into the wash tank (2) is passed, characterized in that in the wash tank (2) an operating pressure po is applied and in the centrifuge unit (1 1) a pressure p-, is applied, which is higher than the operating pressure p ₀ .

2. System for the treatment of a washing liquid according to claim 1, characterized in that in a first line section (9) of the line circuit from the wash tank (2) to the centrifuge unit (1 1), a pressure generator (13) is provided which in the washing liquid the pressure p -, generated.

3. A system for treating a washing liquid according to claim 1 or 2, characterized in that in a second line section (10) of the line circuit from the centrifuge unit (1 1) to the wash tank (2) no control unit for controlling the flow of the washing liquid are provided.

4. System for the treatment of a washing liquid according to claim 1 or 2, characterized in that in the first line section (9) and / or in a second line section (10) of the line circuit from the centrifuge unit (1 1) to the wash tank (2) a control unit for synchronizing an inflow amount in the centrifuge unit (1 1) and a Eindüsmenge in the wash tank (2) is provided.

5. A system for treating a washing liquid according to any one of the preceding claims, characterized in that in the second line section (10) from the centrifuge unit (1 1) to the wash tank (2) a pressure p ₂ less than the pressure p-, the centrifuge unit ( 1 1) is provided, preferably a pressure p ₂ , which corresponds to the operating pressure p ₀ .

6. System for the treatment of a washing liquid according to one of the preceding claims, characterized in that the wash tank (2) to a vacuum generator (7), in particular a vacuum generator, for generating the operating pressure p _{0 is connected} in the wash tank.

7. System for the treatment of a washing liquid according to one of the preceding claims, characterized in that the operating pressure Po in the wash tank (2) 0.5 - 300 mbar, in particular 1 .0 - 100 mbar.

8. A washing liquid treatment system according to any one of the preceding claims, characterized in that the centrifuge unit (11) comprises at least one, preferably two or more, centrifuges (14, 14 ') fed by the first line section (9) ,

A scrubbing liquid processing system according to any one of the preceding claims, characterized in that the centrifuge unit (11) comprises a collecting vessel (16) for collecting treated scrubbing liquid connected to the second conduit section (10), wherein 16) the pressure p-, the centrifuge unit (1 1) is present.

10. A system for treating a washing liquid according to any one of the preceding claims, characterized in that in the centrifuge unit (1 1) is applied an atmospheric ambient pressure.

1 1. Process for the treatment of a scrubbing liquid from a scrubber, comprising the following steps: Passing the washing liquid from a washing tank (2) of the scrubber into a centrifuge unit (11) through a first line section (9) from the washing tank (2) to the centrifuge unit (11),

- Separation of impurities from the washing liquid by means of the centrifuge unit (1 1) and

- Returning the washing liquid from the centrifuge unit (1 1) in the wash tank (2) through a second line section (10) from the centrifuge unit (1 1) to the wash tank (2), characterized in that

- In the wash tank (2) an operating pressure p _{0 is} applied, and

- When passing the pressure in the washing liquid is increased to a pressure pi, which rests in the centrifuge unit (1 1) and is higher than the operating pressure p ₀ .

12. A method for treating a washing liquid according to claim 1 1, characterized in that when returning the washing liquid in the second line section (10) a pressure p _{2 is} smaller than the pressure p-, the centrifuge unit (1 1) is applied, so that the processed Washing liquid from the centrifuge unit (1 1) is sucked off.

13. A method for treating a washing liquid according to claim 1 1 or 12, characterized in that in the second line section (10) a pressure p ₂ is applied, which corresponds to the operating pressure p ₀ in the wash tank (2), so that the treated washing liquid in the Washing tank (2) is fed.

14. A process for the preparation of a washing liquid according to any one of claims 1 1 to 13, characterized in that the operating pressure p ₀ in the wash tank (2) is given by a suction pressure, with a medium to be washed through the wash tank (2) is sucked.

15. Plastic processing plant with a system for the treatment of a washing liquid according to one of claims 1 to 10.

16. Plastic processing system according to claim 15, characterized by a processing unit (1), in which a medium to be washed is produced in the plastics processing, and a vacuum generator (7), which sucks the medium to be washed from the processing unit (1) with an operating pressure po, wherein the system for treating a washing liquid between the processing unit (1) and the vacuum generator (7) is provided.