WO2009086598A1

WO2009086598A1 - Gas scrubber

Info

Publication number: WO2009086598A1
Application number: PCT/AU2009/000016
Authority: WO
Inventors: Glen Thomas A Hewson
Original assignee: Glen Thomas A Hewson
Priority date: 2008-01-08
Filing date: 2009-01-08
Publication date: 2009-07-16

Abstract

A gas scrubber for removal of unwanted gas components and particulates from a flow of gas. The gas scrubber includes a centrifuge (4, 5) having a plurality of passages for the flow of gas to pass through, the centrifuge (4, 5) having a shape which diverges from its upstream extent to its downstream extent in order to produce a zone of low pressure there within. The centrifuge (4, 5) houses a plurality of ionizers (6) for ionizing the flow of gas to cause the unwanted gas components and particulates to electrically precipitate onto the centrifuge. The centrifuge (4, 5) also houses one or more atomizers (7) located inside the centrifuge for atomizing a scrubber liquid and spraying said liquid transverse the flow of gas for scrubbing the flow of gas and removing the precipitate from the centrifuge. The gas scrubber removes greenhouse gases and particulates produced in industrial flu waste.

Description

"Gas Scrubber" FIELD OF THE INVENTION

This invention generally relates to a process for the removal of unwanted gas components and particulates pollutants from flows of gas; in particular gas components and particulates commonly found in industrial flu gases. More specifically, this invention relates to a gas scrubber for the removal of Carbon Dioxide (CO₂), Nitrogen Oxides (N_XO_X) and Sulphur Dioxide (SO₂) as generated from electrical power stations that utilize fossil fuels which contribute to greenhouse gas initiated climate change. BACKGROUND TO THE INVENTION

Uncontrolled or inefficient filtering of industrial flu gas have long been the cause of acid rain and air pollution problems which today are the subject of worldwide focus and concern.

Methods to prevent these "anhydride" industrial flu gases and particulates from entering the atmosphere are technically complex and very costly.

Traditional thinking over recent decades has slowly progressed from conventional water scrubbers to chemical solutions both individually and combined.

More recently, processes involving air-cooling, oxidization, and the use of water soluble and chemically absorbed ingredients which can be recycled, have shown some measure of success.

However, it remains that most methods, processes or mechanical technologies are too slow, too inefficient, too complex and/or too costly. This invention is designed to treat anhydride industrial flu gases very efficiently at high volume speed with a target removal of more than 75% and preferably more than 90% of unwanted gas components and/or particulates.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a gas scrubber for removal of unwanted gas components and particulates from a flow of gas, the gas scrubber including: a centrifuge having a plurality of passages for the flow of gas to pass through, the centrifuge having a shape which diverges from its upstream extent to its downstream extent in order to produce a zone of low pressure therewithin; an ionizer operable within the centrifuge for ionizing the flow of gas to cause the unwanted gas components and particulates to electrically precipitate onto the centrifuge; and, an atomizer located inside the centrifuge for atomizing a scrubber liquid and spraying said liquid transverse the flow of gas for scrubbing the flow of gas and removing the precipitate from the centrifuge.

In accordance with another aspect of the present invention there is provided a process for the removal of unwanted gas components and particulates from a flow of gas, the process including the steps of: creating a flow of the gas which includes the unwanted gas components and particulates, the flow of gas being confined into a plurality of channels each located at a distance from a central axis of rotation; rotating the flow of gas for applying a centrifugal force thereto and producing a low-pressure zone; ionizing the flow of gas to cause electrical precipitation of the unwanted gas components and particulates; atomising a scrubber liquid; and, spraying the atomised liquid transverse the flow of gas for scrubbing the flow of gas and removing the precipitate.

Typically, the scrubber liquid is water or a solution of ammonium hydroxide or the like. The latter chemically reacts with the unwanted gas components and particulates in an acid-base reaction to neutralise them and produce a stable salt. Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word "preferably" or variations such as "preferred", will be understood to imply that a stated integer or group of integers is desirable but not essential to the working of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

The nature of the invention will be better understood from the following description of a specific embodiment of the gas scrubber of the present invention, given by way of example only, with reference to the accompanying drawing which is a cross sectional side view.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the drawing there is shown a gas scrubber in accordance with one embodiment of the present invention. The gas scrubber includes components bearing labels 1 to 11 , as follows: The item labelled as 1 designates 2 low power motors (typically about 2 kW each). One of the motors 1 drives an outer rotor 4 in an inner rotor 5 at a speed sufficient to produce a centrifugal force adequate to propel a flow of atomized scrubber liquid transverse to a flow of gas (such as, for example, industrial flu gas) for treatment. The other motor 1 drives a centrifugal fan 3 for drawing a flow of gas through the gas scrubber.

The item labelled as 2 is a set of two electrical transformers with high voltage leads connected to each disc 6. The transformers typically operating at less than 60,000 volts - but at a high enough voltage to be able to form a corona field into a stream of air. More particularly, the transformers operate at around 48,000 volts. The voltage is chosen so as to avoid arcing when the gas scrubber is not is operation, yet high enough to ionise the gas stream between the outer rotor 4 and the inner rotor 5. One of the transformers delivers power to corona forming discs 6 and the other delivers power to electrify water droplet forming discs 7.

The item labelled as 3 a high volume pressure fan - for producing a stream of gas flowing through the gas scrubber.

The item labelled as 4 is a rotor outer which is typically frustoconical with its widest extent uppermost. The rotor outer 4 is typically in the form of a metal cone joumalled to an outer casing 10. The rotor outer 4 typically has insulating vanes mounted substantially parallel to the central axis of rotation. The vanes divide the flow of gas into segments. Typically, the vanes are made of PVC. Typically, 32 such vanes are used. The vanes have the effect of forming smaller flows of gas which can be more precisely processed. The item labelled as 5 is a rotor inner disposed within the rotor outer 4. The rotor inner 5 includes a plurality of insulating discs, such as, for example, 3 PVC discs, positioned inside the rotor outer 4. Typically, the rotor inner 5 is attached to and rotates with the rotor outer 4. In the exemplary embodiment there is an air gap of greater than 10 mm between the rotor inner 5 and the rotor outer 4. More particularly there is an air gap of 14 mm from ioniser points on ioniser discs 6 and the rotor outer 5. The vanes connect the inner rotor 5 to the outer rotor 4.

It is to be understood that the size of the air gap depends upon the voltage of the transformers. It has been found that a transformer voltage of 48,000 volts requires an air gap of about 14 mm. If the air gap is smaller there is constant electrical sparking between the rotor inner 5 and the rotor outer 4 when no gas flow is being processed and stops the generation of corona. An air gap greater than 14 mm is permissible.

The items labelled as 6 are ioniser discs. In the exemplary embodiment there are two ioniser discs 6 each having central electrical slip rings directly connected to an outer band of metal in which is mounted multiple ion discharge points to produce corona into the air stream between the rotor outer 4 and the rotor inner 5.

The item labelled as 7 is an atomiser disc with a slip ring connected to an outer band of stainless steel mesh designed to electrify droplets of scrubber liquid introduced centrally and energized centrifugally to pass through mesh. The atomiser disc 7 is, in the exemplary embodiment, disposed upstream of the ioniser discs 6. The stainless steel mesh functions as an atomizer for the scrubber liquid. Typically, the mesh has angular apertures with dimensions less than about 2 mm, such as, for example, about 1 mm. The item labelled as 8 is a distributor located upstream of the disc 7. The distributor is fed with water or scrubber liquid for the purpose of cooling the flow of gas and starting the scrubbing process. The distributor is a downward facing cone having vanes radiating outwardly upon its downstream surface. Water or scrubber liquid is trained onto the downstream surface and the rotation of the rotor 4,5 causes the liquid to be distributed outwardly into the flow of gas.

The item labelled as 9 is a pump located in the bottom reservoir supplies scrubber liquid to each disc 6 and 7 as required.

The item labelled as 10 is an outer casing for mounting into or above an industrial gas flu.

The item labelled as 11 is a scrubber liquid reservoir.

Typically, the scrubber liquid is water or a weak solution of ammonium hydroxide or the like. The latter chemically reacts with the unwanted gas components and particulates in an acid-base type reaction to neutralise them and produce a stable salt to sequester the unwanted gas components and particulates emitted form the industrial flu.

When assembled the gas scrubber is in the form of a cylindrical shaped machine that has an internal rotor 4 driven by a two kilo-watt motor disposed in a vertical position above the centrifuge rotor 4.

The rotor 4 is designed and built to enable air containing flu gas emissions and particulates to flow upwards through a plurality of air canals, typically 32 air canals, within the perimeter of the rotor body 4.

The rotor 4 has a number of separate discs, typically four or more, within the 32 air canals which carry the high voltage slip rings to receive the voltage from the transformer mounted above.

Each disc of the rotor 4 consists of a non-conductive PVC (or the like) disc with the first slip ring around the centre perimeter and also electrically connected to an outer mounted band of metal which is in turn fitted with a multiple of ionizing points. The outer most skin of the rotor consists of a steel cone which is fitted over the insulating PVC components to become one rotating member with a positive earth. The outer steel core is fitted with a bearing assembly at each end which is also mounted on a central axis.

The central axis is hollow which allows scrubber liquid tubing to be directed in the lower end to supply said scrubber liquid to each disc as required.

The hollow central axis in the upper end allows the high voltage electrical leads to be mounted at each disc to provide high tension power to all the discs 6 except the lowermost disc which carries the cone 8.

Adjoining, but not fixed to the upper open end of the rotor 4 is positioned a centrifuged fan 3 driven by the second motor 1. The fan design moves a large flow of pressurised air out of the machine which then creates a vacuum condition within the cleaning area of the rotor.

The vacuum condition greatly assists the separation of particulate and flu gas emissions from the flow of gas which is being treated.

Whilst the present embodiment has been described with reference to two ioniser discs 6 and one atomiser disc 7, the gas scrubber could have more ioniser and atomiser discs. In the latter case it is envisaged that the ioniser and atomiser discs 6 and 7 could be interspersed vertically - provided there is sufficient vertical spacing to avoid the scrubber liquid discharging the electric charge of the ioniser discs 6.

Also, it is envisaged that the rotor inner 5 could rotate with respect to the rotor outer 4. In this case the 32 vanes rotate about the central axis and so increase the path length of the flow of gas through the gas scrubber - and hence increase the residency time of the flow of gas in the gas scrubber.

In use, the gas scrubber is plumbed into the gas exhaust line of an industrial process upstream of a conventional gas flu. A flow of gas is induced through the gas scrubber by the vacuum created by the fan 3. The flow of gas enters the gas scrubber upstream of the distributor 8 which sprays water and/or scrubber liquid into the flow of gas for cooling and scrubbing of the gas. The atomiser disc 7 adds further scrubber liquid to the flow of gas and the ioniser discs 6 create a corona which travels across the flow of gas from the inner rotor 5 to the outer rotor 4. The corona ionises the scrubber liquid and the flow of gas which removes the unwanted gases and particulates from the flow of gas and precipitates them onto the outer rotor 4. The scrubber liquid further spreads out over the inner surface of the outer rotor 4 and washes the precipitate off the outer rotor 4 and carries it downstream towards the downstream end of the centrifuge for further processing. In one embodiment the gas scrubber has a diameter of about 600 mm and the rotor 4 operates at greater than 1 ,000 rpm, more particularly about 2,800 rpm. It is to be understood that for larger diameter gas scrubbers the rotational speed would be reduced. It is important to balance the rotor 4 in order to efficiently operate at these speeds. In another embodiment it is envisaged that the gas scrubber could have a diameter of around 10 metres of more.

The following are important observations in relation to the present invention. 1. Separation of unwanted gases and particulates from a flow of industrial waste gas can be efficiently achieved by using a combination of a centrifuge principal, electrostatic precipitation and atomised scrubbing liquid.

2. Of immense importance in this concept is the nesting of each component together and in the right order thereby assisting and complementing the successful action of each process to a whole result.

3. a) Water distributor cooling intake air; b) Centrifugal force applied to each method; c) Vacuum condition throughout working area; d) Water scrubbing using vacuum and centrifugal force; e) Electric precipitation combines with centrifugal force; and, f) Electrically charged droplets assisted by centrifugal force.

4. The process simultaneously removes air born particulate and anhydride flue gases by moving a large volume of emissions at high speed. 5. The machine contains many components each working for specific causes and each positioned to work in harmony.

6. Centrifugal force assists and boosts the process at each disc.

7. A vacuum condition throughout the working area of the machine rotor creates greater efficiencies in air cleaning and scrubbing. 8. Water scrubbing with the aid of both a vacuum condition and centrifugal force boosts emissions cleaning efficiencies greatly.

9. Electric precipitation combined with centrifugal force can generate positive air cleaning.

10. Electrically charged water droplets assisted with centrifugal force permits a high concentration of airborne emissions capture at super speeds.

11. Residue from the total cleaning process can be dewatered (dried or centrifuged) then sold as fertilizer, water can be filtered (cleaned) and recycled. 12. As little or no chemical additives are used, running costs are minimal, the main ingredient is water.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in j addition to those already described, without departing from the basic inventive concepts of the present invention. For example, the system and process could be used in relation to other unwanted gases - such as, for example, including methane. Also, alkaline salts other than ammonium hydroxide could be used as the scrubber liquid.

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Claims

CLAIMS:

1. A gas scrubber for removal of unwanted gas components and particulates from a flow of gas, the gas scrubber including: a centrifuge having a plurality of passages for the flow of gas to pass through, the centrifuge having a shape which diverges from its upstream extent to its downstream extent in order to produce a zone of low pressure there within; an ionizer operable within the centrifuge for ionizing the flow of gas to cause the unwanted gas components and particulates to electrically precipitate onto the centrifuge; and, an atomizer located inside the centrifuge for atomizing a scrubber liquid and spraying said liquid transverse the flow of gas for scrubbing the flow of gas and removing the precipitate from the centrifuge.

2. A gas scrubber according to Claim 1 , in which a vacuum means is provided at the downstream end of the centrifuge, the vacuum means being in fluidic communication with the centrifuge for creating a low pressure zone in the centrifuge to assist in removal of the particulates from the flow of gas.

3. A gas scrubber according to Claim 1 , in which the scrubber liquid is a solution of ammonium hydroxide.

4. A process for the removal of unwanted gas components and particulates from a flow of gas, the process including the steps of: creating a flow of the gas which includes the unwanted gas components and particulates, the flow of gas being confined into a plurality of channels each located at a distance from a central axis of rotation; rotating the flow of gas for applying a centrifugal force thereto and producing a low-pressure zone; ionizing the flow of gas to cause electrical precipitation of the unwanted gas components and particulates; atomising a scrubber liquid; and, spraying the atomised liquid transverse the flow of gas for scrubbing the flow of gas and removing the precipitate.

5. A process according to Claim 4 also including the step of electrically charging the atomised scrubbing liquid to assist in the capture of airborne emissions.