WO1989008492A1

WO1989008492A1 - Method for eliminating volatile impurities in gas

Info

Publication number: WO1989008492A1
Application number: PCT/SE1989/000143
Authority: WO
Inventors: Lars Nilsson
Original assignee: App Armerade Plastprodukter Ab
Priority date: 1988-03-17
Filing date: 1989-03-17
Publication date: 1989-09-21
Also published as: DK220790D0; EP0404813A1; SE462702B; AU3437889A; SE8800972D0; DK220790A; SE8800972L

Abstract

For eliminating environmental problems and health problems caused by e.g. styrene in air and other volatile organic compounds, a method is suggested which aims at the polluted gas, e.g. air, being introduced under pressure into a reagent liquid (3) being contained in a container (1) and brought into contact with reagents contained in the reagent liquid, which are of such kind that the compound in question e.g. styrene, oxidizes and remains in the reagent liquid as a water soluble, dialcoholic compound, and that from the container (1) purified gas is carried off to a subsequent separation device (26), e.g. a cyclone, for removing of possible liquid particles accompanying the outflowing gas and returning of these to the reagent liquid in the container (1).

Description

METHOD FOR ELIMINATING VOLATILE IMPURITIES IN GAS.

The present invention relates to a method for removing volatile impurities from gas. An example of such volatile impurity is styrene, which already at contents as low as slightly above 1 ppm in air, can, thanks to its characteristic odour, be identified by the sense of smell. Because of this, many people find it very disagreeable to be in the vicinity of small as well as large plastics industries, where styrene is used as solvent and/or cross-linking reagent at polymerization of unsaturated polyester plastics, also because styrene is generally considered hazardous to health and carcinogenic.

Styrene is used i.a. for manufacturing of boats, tubes and many other plastic products and such manufacture can take place in open as well as in closed moulds on small and large premises. Especially such production in open moulds causes considerable working environment problems and health risks due to the fact that styrene is set free during the hardening process and is allowed to mix with the air in the factory. Such working environment problems have up to now been solved by vigorous ventilation of the premises and in that way a satisfactory environment on the factory premises has been achieved, but not in the surroundings receiving the exhausted styrene-containing air, which, as previously mentioned, is regarded as quite unhealthy. This circumstance, as well as other problems connected with styrene discharge, has led to a situation where the authorities issuing permits can no longer allow the setting up of new plastics industries in densely built-up areas, and many small, already established plastics industries have their permits withdrawn for enviromental reasons and have, thus, to close their business. The increasing use of styrene and other organic solvents coupled with the steadily decreasing limits for accepted air pollution has also resulted in great problems of a technical as well as of an economic nature also for established, large plastic manufacturerε.

The purpose of the present invention is, therefore, to solve these problems through a method for eliminating volatile organic impurities in air, being such that it eliminates styrene found in air by rendering this harmless also in each subsequent step, so that no secondary pollution problems arise either. The incentive or the reason for the prevailing misgivings concerning the survival and establishing of styrene using industries will thereby disappear and the potential danger of the styrene , i.e. that styrene absorbed in the body can be converted into styrene oxide, which by some research scientists is supposed to be the styrene metabolite that can be carcinogenic, will at the same time be effectively prevented.

The object of the present invention is obtained thereby that the method shows the characteristics defined in the patent claims and a characteristic feature of the present invention can be described as follows. Styrene-containing air is introduced under pressure into a reagent liquid in a vessel and is brought into contact with reagents contained in the reagent liquid of such type, that the styrene is brought to oxidize and remain in the reagent liquid as a dialcoholic product which by nature is harmless. This inventional kemosorbental method gives, in other words, reaction products that are not classified as toxic and can from strictly toxicological criteria even be let out into the sewage without any complications. Neither does the present method cause the disadvantage of burdening the user with a great volume of used absorbent which is the case at known methods for removing or eliminating of organic solvents, i.e. by means of active carbon as absorbent of the styrene. It is true that such absorbents can be regenerated, but not at a cost acceptable to the user.

The present invention is not only useful for the elimination of styrene in air but also for other volatile organic compounds that range under the group unsaturated hydrocarbons that are not aromatic.

The invention is more closely described in the following with reference being made to the accompanying drawings, in which Figure 1 shows an embodiment of a device for carrying out the method according to the invention, Figure 2 shows part of said device, partly in cross section, Figure 3 is an end view of the device in Figure 2 and Figure 4 shows schematically and in section a nozzle arrangement contained in the device.

In Figure 1 an embodiment of an inventional device for carrying out the method according to this invention, is schematically shown. According to this embodiment the device comprises a container 1 with a closed space 2 containing a reagent liquid 3 containing water and reagents, in which at least potassium permanganate dissolved and/or suspended in the liquid is an essential part. The liquid can possibly contain also small amounts of commercially available chemicals for achieving surface tension reduction and/or for facilitating sedimentation of salts formed.

For supplying of reagent liquid the container 1 is provided with a closable supply pipe 4, which is placed at the outside of the container and which can also act as a glass gauge provided with a level indicator for keeping the level of the reagent liquid constant within the container 1. This supply pipe opens out under said liquid level in the space 2 and preferably in an area where the container is turned into a downwards narrowing draining pocket 5, in which formed salts are collected and which ends in an outlet connection piece 6, with one, two or more preferably remote controllable draining valves 7 for draining the contents of the container of reagent liquid and precipitated salts, e.g. to the sewage, a vehicle-based slurry tank or the like.

The container is at its upper end provided with a closed, building-up 8, preferably removably connected to the container 1, e.g. by means of bolt connections 9, which building-up 8 contains an inlet part 10 and an outlet part 11. The inlet part shows an inlet opening 12 which is connected to a fan 13 for sucking out styrene-containing air from the .factory premises. On existing, ventilated premises this fan 13 can consist of an available ventilation. fan and the inlet opening 12 can also be connected to an available ventilation system after its fan.

Said inlet opening 12 opens into a channel 15 separated from the space 2 by a wall 14, at the wall 14 of which are suspended one or more nozzles 16 emerging into the space 2. Each of these contains a nozzle pipe 17 which has a from the inlet part 10 decreasing cross section area in order to give the polluted air fed from the fan an increased rate before leaving the nozzles 16. The number of nozzles 16 and, thus, the total opening area of the nozzles in the partition wall 14 should be adjusted to the capacity of the fan, so that said rate increase is always obtained and the air to be purified is injected under pressure and with high rate. Each nozzle 16 can, within the scope of the present invention, have its outlet opening 18 below or somewhat above the level of the reagent liquid present in the space 2 and preferably on or slightly below said level as shown in the embodiment illustrated in the drawings. The fairly concentrated air flow or air jet from each nozzle opening 18 will, thus, hit the reagent liquid with force and at high rate and so press reagent liquid concentrically outwards from the centre of the air flow or air jet so as to create a crater and the start of a wave that is caught by a splash screen 19 provided outside and extending all about the nozzle opening 18 at the same time as the air flow from the nozzle opening 18 is redirected by the concave arched liquid surface of the crater and is forced upwards towards the splash screen 19 and thereby brings the reagent liquid along in its upward motion, which is guided not only by the splash screen 19 but also by a horizontal screen20, which is placed above the splash screen and like this fastened to the nozzle tube 17, which horizontal screen 20 redirects the air flow outwards and downwards through the space between the two screens 19 and 20. The reagent liquid brought along by the air flow is also brought into contact with these two screens 19 and 20 and is atomized when it hits the screens 19 and 20, whereby the oxygenous air is brought to mix effectively with the reagent liquid.

The splash screen 19 can, further, in the part 21 located above the level of the reagent liquid, which preferably terminates in an inwardly bent edge portion 22, be provided with continuous slots or openings through which reagent liquid as well as air is pressed out like cascades and atomized before it hits the liquid level and is, thus, brought into contact with the air being redirected from the screen 20. The circumstance that the continuous air flow from and through each nozzle, which is schematically illustrated in Figure 4 by means of arrows 23, continuously brings along reagent liquid from the bottom of the crater, means that liquid flows are created in the reagent liquid, as schematically shown in Figure 4 by means of arrows 24, which see to it that "unused" reagent liquid is continually supplied to the crater bottom in order to be sucked along by the air flow.

By this arrangement the injected air as well as the reagent liquid is atomized and thereby a very large active contact area is obtained to bring the styrene carried with the air into contact with the suspended and/or dissolved reagent or reagent chemicals in the reagent liquid. The styrene present in the air is thereby brought to oxidize and to change through said reaction with the reagent chemicals to a water soluble compound which remains in the reagent liquid as a totally harmless dialcoholic product.

The reaction takes place in accordance with the formula:

R = H, alkyl

R' = H', alkyl, aryl

The air, thus rendered harmless and purified of styrene, passes out from the space 2 through an outlet opening 25 and passes therefrom to a subsequently connected cyclone 26 or other separation device for separation of possible liquid particles that can accompany air flowing out from the space 2 in the container 1. Separated liquid is directed to a well or container 27, preferably with an overflow discharge 28, whereafter the liquid is returned to the space 2 via a conduit 29 by a pump 30, which can also be used for leading in the liquid, e.g. water, which is a principal ingredient in the reagent liquid, via a pipe 31.

The present invention is not restricted to what has been described above and shown in the drawings but can be amended and modified in many different ways within the scope of the inventive idea defined in the following claims.

Claims

1. Method for removing volatile organic impurities from gas, e.g. air, C h a r a c t e r i z e d in that the polluted gas is introduced under pressure into a reagent liquid (3) contained in a container (1) and is brought into contact with reagents contained in the reagent liquid, which are of such kind that the organic compound or compounds in the gas oxidize and remain in the reagent liquid as a water soluble, dialcoholic compound, and that from the container (1) purified gas is led to a subsequent separation device (26), e.g. a cyclone, for removing of possible liquid particles accompanying the outflowing gas and returning thereof to the reagent liquid in the container (1).

2. Method according to claim 1, wherein the volatile organic compound consists of unsaturated hydrocarbons which are not aromatic, e.g. styrene, and the gas of air, c h a r a c t e r i z e d therein that at least one oxidation agent, e.g potassium permanganate, is used as reagent in the reagent liquid and the liquid being water.

3. Method according to claim 1 or 2, c h a r a c t e r i z e d therein that the polluted gas is brought at high rate into contact with the reagent liquid.

4. Method according to claim 3, c h a r a c t e r i z e d in that the polluted gas is brought into contact with the reagent liquid from above via rate increasing nozzles.

5. Method according to claim 3, c h a r a c t e r i z e d in that the polluted air is brought into contact with a reagent liquid via an atomizing nozzle