DE102013225607A1 - System, apparatus and method for purifying a gas stream - Google Patents

Abstract

The present invention relates to a device for purifying a gas stream and a method for operating the device. The device comprises a carrier assembly having a liquid feed and outlet, the carrier assembly being configured to direct the liquid between the feed and outlet over a number of carriers and to form a flowing liquid film on the surface of the carriers comprise an electrically conductive part. A gas flow guide directs the gas flow to contact the flowing liquid film on the surface of the number of carriers. In addition, the electrically conductive part is electrically charged. The components of the gas stream which come into contact with the flowing liquid film can be removed therefrom. In addition, charged components of the gas stream can be attracted via a Coulomb force through the electrically conductive part and in this way also come into contact with the flowing liquid film and are thus removed from the gas stream.

Description

The invention relates to a system, apparatus and method for purifying a gas stream.

In the production of paints or in paint mixing plants pigments and resins are often suspended or dissolved by means of volatile solvents and then spent in the actual paint mixture. The volatile solvents such as methyl ethyl ketone or acetone can outgas. Therefore, mixing and stirring tanks of production plants are continuously sucked off to locally remove the volatile solvents dissolved in the ambient air. When filling or emptying the aforementioned containers, high solvent concentrations in the environment of the containers occur for a short time, which can only be removed inadequately with conventional exhaust air cleaning devices from the extracted air.

In printing shops, paper webs are subject to high air flow rates with very high levels of volatile organic compounds (VOC) during the drying process. The concentration of the VOCs is temporally substantially constant, so that at a drying plant z. B. typically 60000 m ³ / h exhaust air with a typical VOC concentration of about 2-10 g / m ³ incurred in operation. At least in packaging gravure usually toluene is used as a solvent that can be recovered with ordinary systems difficult from the exhaust air to use it again after further processing steps in the printing process.

In paint shops, the offset with solvents exhaust air, which is produced when painting, for example, vehicles or other parts, sucked and fed to an exhaust air purification device. In the exhaust air purification device, the solvents dissolved in the exhaust air are separated in order to purify the exhaust air and to separate off the solvents, in order to prepare them, for example, in a usable state.

Such an ordinary exhaust air purification device may for example be an electrostatic precipitator in which a potential difference is generated to deposit charged components of the exhaust air by means of electrostatic attraction to a separator and thus to remove it from the exhaust air. To increase the efficiency of the electrostatic precipitator is usually preceded by an ionization to ionize the components to be removed from the exhaust air and thus make it separable for the electrostatic precipitator. The separator can, however, z. B. are coated by Lackaerosole with paint particles that are difficult to remove.

In order to avoid the disadvantages described above and to achieve a more efficient cleaning of gas streams of any kind, such as the abovementioned exhaust air streams, a device for purifying a gas stream according to claim 1 is proposed in a first aspect. Further advantageous embodiments are given in the dependent claims.

The device according to the invention for purifying a gas stream comprises:
a carrier assembly having a supply and an outlet for a liquid mixture, wherein the carrier assembly is designed such that the liquid mixture between the supply and outlet is passed over a number of carriers and forms a flowing liquid film on the surface of the carrier, wherein the carrier is an electrically conductive Part that is electrically charged include; and
a gas flow guide configured such that the gas flow comes into contact with the flowing liquid film on the surface of the number of supports.

The carriers are preferably porous knitted plastic tubes which have been subjected to a heat treatment for mechanical stabilization.

In a first embodiment, the electrically conductive part is wound around the carrier. In a first alternative, the electrically conductive part is an integral part of the carrier and in a second alternative, the electrically conductive part is shot through the carrier. The electrically conductive part may in particular be an electrically conductive wire. In a preferred embodiment of the invention, the electrical charge of the electrically conductive part is variable.

The liquid used may be a mixture and preferably consists essentially of water. The liquid may also comprise at least one glycol.

According to a second aspect of the invention, a method for operating the aforementioned device is proposed, comprising the following steps:
Producing a flowing liquid film on the surface of the number of carriers;
Generating an electric charge on the electrically conductive part; and
Passing the gas flow past the number of carriers so that the gas flow contacts the flowing liquid film on the surface of the number of carriers.

In a preferred embodiment of the method, the electrical charge on the changed conductive part. Particularly preferably, the electrical charge on the conductive part is changed depending on the gas flow. In a further embodiment, the electrically conductive part is switched off at predetermined intervals.

According to a third aspect of the invention, there is provided a system for purifying a gas stream having at least one ionization device capable of ionizing components of the gas stream; and at least one of the above-described devices for purifying a gas stream, wherein the at least one ionization device is connected upstream of the at least one device for purifying a gas stream.

Preferably, the system further comprises an arrangement for preparing the liquid mixture and is arranged such that the spent liquid mixture is passed from the device for purifying a gas stream to the arrangement for processing and is returned to the device after processing in the arrangement for processing.

According to the invention, a gas stream, which may be, for example, an exhaust air stream from a painting operation, is passed into an ionization apparatus and ionized there. Such ionization devices are known in the art. The (ionized) gas stream is introduced into the device according to the invention for purifying a gas stream, in which the gas stream is guided past the flowing liquid film on the surface of the carrier. On the one hand, the gas stream comes into direct contact with the liquid mixture and components of the gas stream, such as solvents, can be absorbed by the liquid mixture and thus removed from the gas stream. On the other hand, the electrically conductive part, which is preferably designed as an electrically conductive wire, is electrically charged and thereby exerts an electrostatic attraction force (Coulomb force) on the ionized constituents of the gas stream. The ionized components, due to the electrostatic attraction force, move toward the charged electrically conductive portion, thereby coming into contact with the liquid mixture flowing over the carrier and the electrically conductive portion, and can be efficiently removed from the gas flow. Compared to conventional exhaust air purification systems, an increase in efficiency of 20 to 30% is possible.

The components now dissolved or suspended in the liquid mixture can be supplied to a treatment arrangement in a further method step, in order to be removed from the liquid mixture there, so that the liquid mixture can be returned to the device after the preparation and reused. Thus, a closed circuit for the liquid mixture can be achieved, which allows an efficient, low-maintenance and cost-effective operation of the system according to the invention. The components removed from the liquid mixture can be collected and, for example, treated or reused immediately.

Hereinafter, concrete embodiments of the invention will be explained in more detail with reference to the drawings. Identical or equivalent elements are identified by the same reference numeral.

Show it:

1 a schematic representation of a section of the device according to the invention;

2 a schematic representation of the system according to the invention.

The in the 1 illustrated device 10 for cleaning a gas stream has a carrier assembly 1 on (in the 1 only indicated) comprising a supply and an outlet for a liquid mixture. The liquid mixture serves as an absorbent for the components of the gas stream to be removed. As a liquid mixture, hereinafter also referred to as absorbent, any liquid mixture can serve, which can absorb the components to be removed and release again (desorb). Suitable absorbents are, for example, water, mixtures of water and at least one glycol and in particular polyethylene glycol dialkyl ethers.

The gas stream can be, for example, an exhaust air stream from a paint booth, a paint production plant or a printing plant or a drying plant for printed products. In such a gas stream, for example volatile organic compounds are dissolved, such as solvents such as aliphatic and aromatic hydrocarbons, alcohols, aldehydes, ketones, ethers or esters. Depending on the substances dissolved in the gas stream, a suitable absorbent can be selected.

The liquid mixture becomes between feed and outlet via a number of carriers 2 passed, so that on the surface of the carrier 2 a flowing liquid film 4 forms. As a carrier 2 For example, profiles, hoses or pipes can be used. In the illustrated embodiment knitted plastic hoses are shown, which are preferably made of thermoplastics, such as Polyester, polyamide, polyethylene or polypropylene. In particular, polyester is suitable for the knitted plastic hoses. The knitted plastic tubes may be formed from one or more filaments, preferably from a plurality of filaments. The knitted plastic tubes are rendered more mechanically stable by a thermal treatment such as partial melting together or sintering together of the filaments, optionally with shrinkage. The treated plastic hoses are dimensionally stable and show a certain inherent rigidity and bending elasticity. But they remain porous, so that it comes in the operation of the device to an advantageous fluid exchange between the inside and the outside of the knitted plastic tubing, both the flow rate of the liquid film 4 reduces as well as a good mixing of the liquid and a self-cleaning of the carrier 2 causes.

The number of carriers 2 For example, it can be arranged side by side in a straight or curved row parallel to each other with equal or varying spacing. Several rows, for example 10 to 20, can be arranged one behind the other or laterally offset, preferably staggered, arranged parallel to one another. The gas stream is preferably guided perpendicular to these rows, ie in cross-flow, so that the liquid film on the surface of the carrier 2 As completely contacted by the gas stream. The velocity of the gas stream is chosen such that a generation and entrainment of liquid droplets is avoided.

In addition, the carriers have 2 an electrically conductive part 3 on. The electrically conductive part 3 is in the 1 as electrically conductive wire 3 designed. The electrically conductive wire 3 can do it like in the 1 however, may also be part of the carrier wrapped around the carrier 2 be, ie the wire 3 may instead of one or more filaments in the preparation of the carrier 2 be used and so in the carrier 2 may be incorporated or it may conductive carriers, eg. B. of metal wire or conductive plastic. Alternatively, the wire may also be through the carrier 2 to be shot.

Like in the 1 shown is the electrically conductive wire 3 electrically charged so that it exerts an attractive force A on the charged components P of the gas stream. The voltage may be in particular in a range of 500 to 1000 volts, a range of 1000 to 5000 volts or a range of 5000 to 10,000 volts. The voltage is chosen depending on the absorbent used and the components of the gas stream.

Like in the 2 shown, a laden exhaust air flow is first through an ionization device 20 directed to ionize ionizable components of the exhaust air stream and then into the device 10 initiated for cleaning. In the 1 enters the, from the left side, introduced exhaust air to the individual carriers 2 the device 10 , wherein charged and uncharged components P of the exhaust air flow through the flowing liquid film 4 in the case of direct contact of the exhaust air flow with the liquid film 4 can be removed from the exhaust air stream. In addition, the loaded wire exercises 3 an attractive Coulomb force on the charged components P of the exhaust air flow and causes a movement of the charged components P of the exhaust air flow toward the carrier 2 with the liquid film flowing on its surface 4 , In this way, also remove, ionized components P of the exhaust air flow in contact with the liquid film 4 and can thus be removed from the exhaust air stream, By the upstream of the ionization device 20 For example, individual components of the gas stream can be effectively ionized and thus by the downstream device 10 be removed from the gas stream. The charge of the electrically conductive part is preferably matched to the ionization effect of the ionization device.

Like in the 2 2, the absorbent mixed with the components P removed from the exhaust air flow may be in a circulation tank 30 be collected and via a circulation pump 60 a desorption device 40 are supplied to separate the dissolved components P from the absorbent. A suitable desorption device is for example in the DE 20 2010 006 567 U1 which uses a further gas stream to separate the dissolved components P from the absorbent and by means of a condensation device 50 deposit. The deposited components P can be collected and, in the case of the abovementioned solvents, for example, processed in order to enable an efficient and multiple use of the solvents. That in the desorption device 40 Purified absorbent can be placed over the circulation tank 30 again the device 10 be supplied for cleaning. Thus, a closed Absorbenskreislauf can be realized, which allows a simple, effective and inexpensive cleaning of a gas stream.

An inventive system can also be several devices 10 for cleaning and several ionization devices 20 comprising, wherein the filter devices 10 may be connected in series, for example, to subsequently separate various components from the exhaust air. The separated components may be in one or more downstream devices 10 be removed from the liquid mixture for cleaning. Consequently In turn, one or more closed absorbent circuits may be implemented to ensure effective operation of the system.

As mentioned above, the load of an exhaust air stream with, for example, solvents can be constant in time as well as having concentration peaks. It is therefore preferred that the electrical charge of the electrically conductive wire 3 to change, in particular depending on the exhaust air flow. It is particularly advantageous the wire 3 de-energize at intervals to adhering components P through the flowing liquid film 4 from the wire 3 to solve.

With the present invention, an exhaust gas stream to be cleaned compared to the prior art can be cleaned particularly effectively and thus cost-effectively. With the system according to the invention, the components to be removed (individually) can be removed from the gas stream to be purified and collected, for example, to be disposed of or treated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202010006567 U1 [0028]

Claims (15)

Contraption ( 10 ) for purifying a gas stream, comprising: a carrier assembly ( 1 ) with a supply and an outlet for a liquid, wherein the carrier arrangement ( 1 ) is designed such that the liquid between supply and outlet via a number of carriers ( 2 ) and on the surface of the carrier ( 2 ) a flowing liquid film ( 4 ), the supports ( 2 ) an electrically conductive part ( 3 ) which is electrically charged; and a gas flow guide that is configured such that the gas flow with the flowing liquid film ( 4 ) on the surface of the number of carriers ( 2 ) comes into contact. Contraption ( 10 ) according to claim 1, wherein the supports ( 2 ) are porous knitted plastic hoses which have been subjected to a heat treatment for mechanical stabilization. Contraption ( 10 ) according to claim 1 or 2, wherein the electrically conductive part ( 3 ) around the carrier ( 2 ) is wound. Contraption ( 10 ) according to claim 1 or 2, wherein the electrically conductive part ( 3 ) Part of the carrier ( 2 ). Contraption ( 10 ) according to claim 1 or 2, wherein the electrically conductive part ( 3 ) by the carrier ( 2 ) is shot. Contraption ( 10 ) according to one of claims 1 to 5, wherein the electrically conductive part ( 3 ) is an electrically conductive wire. Contraption ( 10 ) according to one of claims 1 to 6, wherein the electrical charge of the electrically conductive part ( 3 ) is changeable. Contraption ( 10 ) according to any one of the preceding claims, wherein the liquid consists essentially of water. Contraption ( 10 ) according to any one of claims 1 to 8, wherein the liquid comprises at least one glycol. System for purifying a gas stream with at least one ionization device ( 20 ) which is capable of ionizing components of the gas stream; and at least one device ( 10 ) according to one of claims 1 to 9, wherein the at least one ionization device ( 20 ) of the at least one device ( 10 ) is connected upstream. The system of claim 10, wherein the system further comprises an arrangement for processing ( 30 . 40 . 50 ) the liquid mixture comprises; and the system is arranged such that the liquid mixture used by the device ( 10 ) to the arrangement for processing ( 30 . 40 . 50 ) and after processing in the preparation arrangement ( 30 . 40 . 50 ) to the device ( 10 ) is returned. Process for purifying a gas stream with a device ( 10 ) according to one of claims 1 to 9, comprising the following steps: producing a flowing liquid film ( 4 ) on the surface of the number of carriers ( 2 ); Generating an electrical charge on the electrically conductive part ( 3 ); and passing the gas flow on the number of carriers ( 2 ), so that the gas flow the flowing liquid film ( 4 ) on the surface of the number of carriers ( 2 ) contacted. A method according to claim 12, wherein the electrical charge on the conductive part ( 3 ) is changed. The method of claim 13, wherein the electrical charge on the conductive part ( 3 ) is changed depending on the gas flow. Method according to one of claims 12 to 14, wherein the electrically conductive part ( 3 ) is switched off at predetermined intervals.

Images