WO1998047603A1

WO1998047603A1 - Purification arrangement

Info

Publication number: WO1998047603A1
Application number: PCT/SE1998/000728
Authority: WO
Inventors: Yngve SÄWSTRÖM
Original assignee: Ekonomivärme I Skaraborg Ab
Priority date: 1997-04-22
Filing date: 1998-04-22
Publication date: 1998-10-29
Also published as: SE9701519L; EP0977623A1; SE9701519D0; AU7242398A; CA2287273A1; SE506745C2

Abstract

The present invention relates to a purification arrangement for purification of a contaminated gaseous medium comprising an ionising equipment (3) for ionising air and at least one mixing chamber (2) wherein the contaminated medium is fed through the mixing chamber (2) in a main flow therethrough and ionised air is added to the main flow from the side. A main feature of the arrangement according to the invention is that the ionised air is fed into the mixing chamber with a flow velocity which substantially exceeds the flow velocity of the main flow.

Description

TITLE: PURIFICATION ARRANGEMENT

TECHNICAL FIELD:

The present invention relates to a purifying arrangement for purifying of contaminated gaseous medium comprising an ionising equipment for ionising air and at least one ixing^{^} chamber whereby the contaminated medium is fed through the mixing chamber in a main flow therethrough and ionised air is added to the main flow from the side.

BACKGROUND:

The demands on purifying affluents from industries and the like are becoming larger as environmental consciousness increases in society.

A way to purify gaseous media from, for example, solvent- based gases, paints etc such as benzine, paraffin, propene and other hydrocarbons occurs by means of ionising. In this form of purifying, the contaminated air is mixed with ionised air. The charged particles cause the contaminating molecules to be combined and precipitated out.

An arrangement for exhaust gas purifying conforming with the preamble to the enclosed patent claims is for example known from AT 387 158 B whereby in a mixing chamber there is a main flow of contaminated air and a smaller flow of ionised air is added from the side.

However, such a known arrangement is burdened with several problems. The most serious problem is that the cost for obtaining the desired degree of purification is far too large or that the desired degree of purification is not possible to obtain at all. OBJECT OF THE INVENTION

It is accordingly an object of the present invention to bring about a purification arrangement which is effective but still relatively cheap with regard to both investment costs and operation costs.

SUMMARY OF THE INVENTION

This object has been obtained by a purification arrangement according to claim 1.

By feeding the ionised air into the mixing chamber with a velocity which substantially exceeds the flow velocity of the main flow the ionised air will quickly penetrate down into the main flow and thus the probability that a contami- nating molecule of the main flow shall be hit by an ionised particle is substantially increased.

According to an aspect of the invention, the ionised air is supplied further via several successively arranged openings in the flow direction of the main flow. In this way said probability increases further and thereby also the degree of purification.

According to a further aspect of the invention the ionised air is added to the main flow with a flow direction which has at least an angle of 40° in relation to the flow direction of the main flow. By this means, the mixing is further improved.

SHORT DESCRIPTION OF THE DRAWINGS

The invention shall now, by way of example, be described more in detail by means of an embodiment example and in connection with the enclosed drawing which shows a schematical picture of a purification arrangement according to the invention. DESCRIPTION OF PREFERRED EMBODIMENT EXAMPLES A purification arrangement according to the invention comprises a supply pipe 1 for the supply of contaminated air, a purification part comprising three mixing chambers 2 and an outlet pipe 6 for removing of purified air. In the embodiment example three mixing chambers 2 are used but of- course even other numbers, such as one or two can be used.

Through the mixing chambers 2 a main flow of contaminated air occurs. From the side, however, a further feed-flow of ionised air occurs. This air is ionised in an ionising equipment 3 which comprises an electrically charged surface which by corona-discharges gives off electrons to the surrounding air. This air which shall be ionised must be relatively clean (Air Quality 1) to allow ionising in a desired degree which, however, is the case with usual fresh air. The air is conducted after it has been ionised via pipes 4 to openings 5 in the sidewalls of the mixing- chambers. Every mixing chamber is in this embodiment example provided with four openings 5 which are arranged successively after each other in the flow direction of the main flow. Other numbers of openings are, however, all of course possible but it is preferable to have more than one opening per chamber. More inlet openings give a better mixing but at the same time the speed (and the amount of gas) of the main flow increases which makes the purification process more difficult downstream.

The flow velocity of the feeding ionised air is preferably appreciably much higher than the flow velocity of the main flow. The velocity relationship is suitably at least 3/1 and preferably at least 5/1. The velocity difference is important for allowing the ionised air to penetrate into the main flow. How great the optimal velocity relationship is will however depend on the contamination concentration and the density of the gas which is to be purified. Higher density means that the speed should be higher and lower density that the speed should be lower. Usually a velocity relation of about 10/1 is to be preferred. The flow velocity of the ionised air should however be at least 0,5 m/s so that the laws of mass inertia shall be applicable instead of the gas laws. Further, there is an upper critical velocity which is dependent on the shape of the openings. This upper velocity limit depends however on the total pressure but is usually about 18 m/s.

The openings should further be arranged so that the direction of flow for the ionised air has an angle in relation to the flow direction of the main flow. This angle should be at least 40° and the addition of ionised air occurs preferably perpendicularly to the main flow. How great the angle should be depends however on the difference of density between the gases and the ionising energy.

The purification arrangement according to the invention further comprises a control system. The control system comprises a sensor 8 and 9 for measuring the degree of contamination in the incoming contaminated air and the purified outgoing air respectively. The difference between these values, for example given as a purification degree in the form of incoming contamination amount minus outgoing contamination amount and divided with the incoming contamination amount, can later be used for conducting the purification arrangement. The result from the sensors 8, 9 is therefore sent via conduits to the ionising equipment and is used for conducting the ionising degree and the flow velocity of the ionised air. Normally, an admixture of 20- 30% ionised air in the main flow is desirable. The sensors may, for example, be commercially available photo-ionising instruments such as Photovac PID 2020 or Photovac 10S Plus. Further parameters can also be used for the regulation such as the direct amount of impurities in the starting-air, the number of ions in the outgoing air, etc.

It is also an advantage to let the flow-pipe for the main flow expand before the mixing chambers, as occurs in the embodiment example, to thus decrease the flow velocity of the main flow through the mixing chambers.

It is further possible to combine the purification arrangement according to the invention with other types of purification such as filers of different kinds, etc. to further improve the purification effect in that way.

The invention has been described above by means of an embodiment example. It is however realised by a person skilled in the art that more variants are possible, some of which have been mentioned, without losing the invention idea. Such obvious variants must therefore be regarded to be included in the present invention such as it is delimited by the following claims.

Claims

CLAIMS :

1. Purification arrangement for purifying a contaminated gaseous medium comprising an ionising equipment (3) for ionising air and at least a mixing chamber (2) whereby the contaminated air is fed through the mixing chamber (2) in a main flow therethrough and ionised air is added to the main flow from the side, c h a r a c t e r i z e d i n that the ionised air is fed into the mixing chamber with a flow velocity which substantially exceeds the flow velocity of the main flow.

2. Purification arrangement according to claim 1 c h a r a c t e r i z e d i n that the ionised air is supplied via several openings (5) arranged successively after each other in the flow direction of the main flow.

3. Purification arrangement according to claim 2 c h a r a c t e r i z e d i n that at least three such openings (5) are arranged after each other.

4. Purification arrangement according to any of the above patent claims c h a r a c t e r i z e d i n that the flow velocity for the ionised air is at least 3 times as large as the flow velocity of the main flow.

5. Purification arrangement according to any of the above patent claims c h a r a c t e r i z e d i n that the flow velocity of the ionised air is at least 5 times as large as the flow velocity of the main flow.

6. Purification arrangement according to any of the above patent claims c h a r a c t e r i z e d i n that the flow' velocity of the ionised air is about 10 times larger than the flow velocity of the main flow.

7. Purification arrangement according to any of the above patent claims c h a r a c t e r i z e d i n that the ionised air is added to the main flow in a flow direction of at least an angle of 40┬░ in relation to the flow direction of the main flow.

8. Purification arrangement according to any of the above patent claims c h a r a c t e r i z e d i n that the ionised air is added to the main flow with a flow direction which is substantially perpendicular to the flow direction of the main flow.