WO2009117781A1

WO2009117781A1 - Extraction and recovery of gases

Info

Publication number: WO2009117781A1
Application number: PCT/AU2009/000376
Authority: WO
Inventors: Roger Davies; Brett Turner
Original assignee: Intex Holdings Pty Ltd
Current assignee: Intex Holdings Pty Ltd
Priority date: 2008-03-28
Filing date: 2009-03-30
Publication date: 2009-10-01
Anticipated expiration: 2010-09-28

Abstract

A method of separating a gas for example carbon dioxide from others such as exhaust gases from a combustion process including the steps of introducing at (1) an appropriate liquid such as water in fine droplet form into a gas mixture at spray chamber (4) so that a significant solution of the gas into the liquid is first achieved then subsequently treating the droplets so that there is a coalescing of these at heat exchanger (3) so that some of the gas being targeted can be separated by being forced out of solution from the liquid and having the coalesced liquid separately located at 6 so the released gas can then be kept separate in storage (8).

Description

EXTRACTION AND RECOVERY OF GASES

TECHNICAL FIELD

The invention has particular application to a method and also an apparatus for extraction of carbon dioxide from flue gases or exhaust gases but is not intended to be limited in its broadest concept to either this gas as such or to the source of gases from which extraction is to be effected.

BACKGROUND ART

It is a known problem that it is costly to extract selected gases to reduce environmental concerns for instance to extract carbon dioxide which is considered by many to be a noxious green house gas.

It is an object of this invention to provide the public with a useful alternative.

DISCLOSURE OF THE INVENTION

We have discovered that if there is introduced an appropriate liquid in fine droplet form into a gas mixture so that a significant solution of the gas into the liquid is first achieved then subsequently treat the droplets so that there is a coalescing of these some of the gas being targeted can be separated by being forced out of solution and by having the coalesced liquid separately located the released gas can then be kept separate and appropriately dealt with.

This technique has particular advantage in that it can be used in a way that allows for its application to a gas stream which may in some cases then allow for ongoing continuous processing. Further it has advantage in that it can used in several ways at least that will keep back pressure to an incoming gas stream being excessive in the circumstances. This is particularly the case where gas stream is originating from an exhaust outlet of some internal combustion engines.

In one further form then the invention can be said to reside in a method of separating carbon dioxide from a mixture of gases which includes the steps of inserting water or another fluid with a sufficiently high solubility coefficient or affinity with the selected gas or gases at an insertion location into the gas solution contained in a chamber or passing along a passageway, the insertion being from one or more positions into or from within the passageway so that the fluid is substantially distributed through the gas mixture, and then cooling the gas fluid mixture by heat exchange and/or by injection of additional fluid effecting coalescing of the fluid droplets containing dissolved gases forming a fluid solution and then transferring the coalesced liquid to a further location to effect release of the dissolved gas or gases.

In preference the method is to then effect a lowering of pressure applying to the fluid containing dissolved gas and /or in the case of some fluids lowering of temperature or in the case of some fluids raising of temperature in each or either case to effect release therefrom of dissolved gases and the depleted gas solution is discharged or passed a further time through the process of fluid injection and removal of the fluid solution for the purpose of further removal of the selected gas or gases from the gas solution.

In a further alternative the invention can be said to reside in a method of effecting separation of gases Including a solution of gases containing anyone or more of the following; carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, benzene, formaldehyde and /or polycydic hydrocarbons and or particulate matter including carbon and other sub-100 micron particulates from the flue or exhaust gases of a hydrocarbon combustion process which includes the steps of inserting water as steam and/or water droplets and/or water vapour at one or more than one location in a passageway containing the flue or exhaust gases before or after or before and after compression by a piston or turbine compressor or other compression process the insertion being from one or more than one position into or from within the passageway so that the injected water is substantially mixed within the flue gases then effecting cooling by passage through a heat exchanger and/or injection of further water as droplets then the water mixture including dissolved gases, emulsions and solid particulates is removed as a condensate mixture from one point or more than one point in the passageway where the condensate mixture contains any of dissolved carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, benzene, formaldehyde and or polycyclic hydrocarbons and or emulsions and or an admixed suspension of particulate matter including carbon and other sub-100 micron particulates which has accumulated and the condensate/emulsion/suspension is removed to a further location where the carbon dioxide and other gases are recovered by lowering the pressure and or agitating the condensate to effect the release of dissolved carbon dioxide and other gases and the solid particulates and emulsions are removed by passage of the fluid through a centrifuge device and or filtration process and weak acids are removed by chemical reaction with an alkali or alkalis which are consumed to produce insoluble salts which are removed by filtration or by passage of an electrical current through the solution and formation of an insoluble salt or insoluble salts by use of sacrificial electrodes and after removal of the condensate mixture the flue gas solution is then expanded by passage through an expansion turbine or expansion nozzle and as a result of cooling of the flue gas solution, further condensate mixture forms and this condensate mixture is removed and subjected to the same process of recovery of gases and particulates and the whole process of passage through the compression and water Injection passageway can be repeated one or more times to increase the percentage of recovery and/or removal of the selected gas or gases including carbon dioxide,

In a further form the invention can be said to reside in a method for separately capturing carbon dioxide from a gas stream and then recovering carbon dioxide in separated gaseous form comprising:

injecting water as a micro mist into a gas stream containing CO2 and being in a heated environment, the shape of the passageway and/or the direction of the injection of water being arranged to limit back pressure to any oncoming gas Stream,

coalescing water droplets in a high pressure environment then collecting such coalesced water so as to be separate from remaining gas fluid mixture,

then lowering pressure and thus cooling the gas stream and collect any further condensate,

exposing the collected water to a partial pressure less than 1 Bar to release the otherwise dissolved CO2 into gaseous form.

collect and compress the CO2 gas for reprocessing.

It has been found that mere introduction of water into an exhaust system tends to increase back pressure presented to exhaust gas entering the system from upstream and in many cases this is disadvantageous to the source providing the exhaust gas stream.

In one alternative form simply providing an expanding passageway for the down- streaming gases and introducing water in the vicinity of the expanding passageway has provided that such water when introduced into the heated area will, when temperatures are above the boiling point of water, expand into steam or a mixture of water vapour and steam and will because of the expanding shape of the passageway be directed at the least in a downstream direction. This implicitly then means that there will be less back-pressure as a result of this expanding passageway. With adjustments of the expanding shape and the volume and quantity of water and temperatures involved, this means that significant quantities of water can be introduced without undue increase in back pressure but also then the water can be directed into a separate location so that it can be subjected to treatment to effect coalescence of the droplets which have been previously exposed to the gases and would have transiently held dissolved gases therein.

However, as a separate approach, the water can be introduced into a passageway in a downstream direction through a nozzle which can induce by Bernoulli effect further suction that can indeed assist in extraction of exhaust or flue gases. This effect is improved if we use a nozzle of the type known as a de Laval nozzle and position this in the passageway and directed downstream. If a liquid in the form of wet vapour is directed into the De laval nozzle at appropriate temperatures and pressures, the effect has been discovered that the nozzle may cause a prandtl- gauert singularity. Such an effect may cause then a significant further translation of heat into velocity of liquid directed downstream which then can improve the effect and efficiency of the process both in relation to additional suction and also in relation to additional energy that can be used for a downstream turbine rf this is to be used in conjunction. This effect can also be used in conjunction with a further downstream repetition of the same effect.

This effect is particularly apparent thus far with carbon dioxide where the percentage of carbon dioxide has In one case been reduced in the exhaust gases by 50% from 13.4% to 6.7%.

The absorption is a result of the close intermixing of oarfoon dioxide rich exhaust gases during the passage of the steam from its formation to a downstream location where it will be caused to at least significantly condense or coalesce for instance by interacting with a turbine extracting energy from the kinetic energy of the gases.

Our results thus far suggest that this absorption effect also results in absorption of other gases such as carbon monoxides, nitrogen based gases and other contaminant gases and particulate matter.

The invention in a further form then can be said to reside in a method for separating gases from a gas mixture including steam water vapour and carbon dioxide which includes effecting introduction of water into the gases at least as steam and effecting a condensation or a coalescing subsequently of the resultant mixture.

In preference introducing the mixture into a turbine effects such a condensation.

In preference such a turbine can be a conventional turbine with many radially positioned shaped blades and single rotor turbine but in alternative configurations it could be a Tesla or prandtl effect type turbine.

Downstream of this can then be further extraction of energy either by a one or more turbines or otherwise.

An initial or further extraction of carbon dioxide from the exhaust gas stream can be performed in further apparatus as described herein. This apparatus permits removal of a percentage of carbon dioxide and other pollutant gases from the exhaust gas stream at one or more than one stage so that there can be sequential arrangements to effect further additional capture and removal of targeted gases.

In a further form of this invention it can be said to reside in an arrangement for assisting in absorption of at least carbon dioxide where this is found in a source of incoming gases with a means to introduce water into a chamber with a further downstream condensation and removal of water containing a component of dissolved carbon dioxide,

An additional demonstrated effect from the technology is the trapping of a percentage of other substances such as the pollutants contained in a source of gas including carbon monoxide and oxides of nitrogen and sulphur.

The invention therefore comprises or includes the injection of a fluid as a mixture containing fine droplets and/or fluid in gaseous form into a carbon dioxide containing gas stream; with further evaporation of some or all of the mixture of injected fluid to gaseous vapour by the thermal energy of the gases and/or by compression of the gas before introduction of the fluid, then condensation or coalescing of the fluid into larger droplets in a heat exchanger and/or across a turbine thereby capturing the carbon dioxide in the fluid condensate.

The process uses capture and removal of carbon dioxide directly from a gas stream by utilising varying conditions of pressure and temperature.

Carbon dioxide and other pollutant gases and particulates are absorbed from a gas stream into the gaseous and more readily into the liquid phase of water. As the temperature of the water falls the solubility of carbon dioxide increases, reaching a maximum value at 4 degrees Celsius. By reducing the temperature of the mixture containing fluid water and gaseous carbon dioxide, the equilibrium between dissolved and gaseous carbon dioxide favours transition of gaseous to aqueous carbon dioxide.

The solubility of carbon dioxide in a fluid such as water increases with increasing partial pressure as well as reducing temperature. Transition of carbon dioxide from gaseous to dissolved aqueous form is therefore favoured by a reduction in temperature and an increase in pressure.

The apparatus described produces conditions of increased pressure and falling temperature, in a gas stream containing carbon dioxide and saturated with a fluid such as water in the form of steam and small water droplets. Conditions favour increased concentration of carbon dioxide in the fluid droplets as the gas stream mixture passes though one or more than one stage.

The rate at which carbon dioxide passes in and out of solution is dependant on the surface area of the water in contact with the carbon dioxide.

The apparatus described produces conditions in one or more than one stage such that there is a gas stream containing carbon dioxide in contact with water as steam or water vapour or water droplets, with a relatively larger surface area presented by small droplets at the time of introduction or condensation. Conditions within the apparatus favour initial creation of small water droplets with progressive coalescing of droplets into larger cooler droplets such that egress of carbon dioxide back to gaseous form is delayed, even if the equilibrium favours a return to gaseous form.

The apparatus described permits removal of large water droplets as these are formed, and thus removal of dissolved carbon dioxide from the gas stream water droplet mixture.

In summary, the progressive cooling and condensation of a fluid such as steam into small liquid water droplets enhance absorption of carbon dioxide into an aqueous solution. Egress of carbon dioxide back into gaseous form from water droplets is minimised by coalescing of smaller droplets into larger droplets. In a preferred case the fluid consists substantially of water or water which includes water containing one or more contaminants or additives.

A portion of the carbon dioxide present in steam having a steam quality of less than 100 weight percent dissolves in the liquid phase of the steam and forms carbonic acid according to the following reaction: CO₂ +H₂ O in equilibrium with H₂ CO₃ (aq)

A much larger portion of the carbon dioxide dissolves to form an aqueous solution of carbon dioxide in equilibrium with the concentration of carbon dioxide in gaseous form.

The total solubility of the carbon dioxide in the steam liquid phase can be calculated; by techniques known to those skilled in the art. See, for example Ellis, American Journal of Science, 257: 217-234 (1959) and Ellis et al., American Journal of Science, 261 : 47-60 (1963), these publications being incorporated herein in their entirety by reference.

A simple and effective process for the removal of significant volumes of carbon dioxide from the exhaust gas has been demonstrated in a 4 litre internal combustion engine prototype.

The carbon dioxide can be collected and stored in compressed form for later disposal or commercial re-use.

Approximately 50% carbon dioxide recovery from the exhaust gas has been demonstrated (exhaust gas concentration of CO2 falling from 13.4% to 6.7%), with a net recovery of energy also. There was also >50% reduction of unburnβd hydrocarbons and particulates. Removal of oxides of nitrogen has been observed but not yet quantified.

An additional demonstrated effect from the technology is the trapping of a percentage of other pollutants including carbon monoxide and oxides of sulphur.

Steam is known to become contaminated with amounts of CO 2 as an unwanted effect in various steam boiler applications and pipes or ducts particularly where steam condenses. The discovery therefore is a set of conditions that promotes increasing concentrations of dissolved carbon dioxide and small concentrations of carbonic acid to form in an exhaust gas steam/water droplet mixture. Of the total concentration of carbon dioxide solubilized in the steam liquid phase, about 99.63 percent is present in the form of carbon dioxide molecules and only about 0.37 percent is carbonic acid.

For a better understanding of this invention it will now be described with relation to an embodiment described with the assistance of drawings wherein

FIG 1 Is a schematic of a first embodiment.

Source of CO2 containing gas is shown as 1.

Common shaft compressor-turbine consists of a compression stage 1a and Expansion stage 2a rotating on a common shaft.

1a, 2a are linked by a common shaft 2 with work derived from the expansion turbine stage contributing to the operation of the compression stage.

Work from the velocity and/ or pressure of the exiting gas passing through the turbine stage 2a is one source of energy to drive the compression stage 1 a of the apparatus. Additional work to drive the compressor stage depends on pressure available from the gas source at 1.

The gas stream gives up energy to the expansion turbine at 2a and separately transfers thermal energy by heat exchanger to ambient environment at 3.

Incoming gas is compressed at 1 a and directed into the spray chamber 4.

Fine droplets of a fluid such as water are sprayed into the compressed gas mixture at 4.

Under increased partial pressure the solubility of CO2 in water is increased. As fine spray water droplets are added at 4 gaseous CO2 passes into aqueous CQ2 solution.

Heat is released to the surrounding environment at the heat exchanger 3. Cooling of the gas stream causes water droplets to condense and coalesce into progressively larger droplets.

Separation of water droplets from remaining exhaust gases occurs at 5 by a water separator. Water is removed and delivered to the holding chamber at 6. The depleted gas stream is directed to the expansion turbine stage 2a. CQ2 and particulates as well as other pollutant gases soluble in water are removed.

A partial vacuum scavenge pump 7 applies a pressure of less than 1 Bar to the holding tank 6. The reduced pressure in 6 causes CO2 to return to gaseous form bubbling from the surface in 6, leaving a mixture of water and carbon derivative particulate solids.

Gaseous CO2 scavenged from 6 is compressed to liquid from and stored in 8 for later disposal into long-term storage reservoirs. The mixture of water and particulates is filtered at 9 for re-circulation to 4 by pump/controller 10.

Example 2

In a further example the test bed is a 3.9 litre straight 6 cylinder Australian ford engine sold in Australia as a falcon - 1992 model. Exhaust manifolds were expanding manifolds, A turbine used is a turbine using a plurality of planar plates defining between them slots and is thereby a velocity turbine, constructed in a 4 inch diameter and geared to the engine crank shaft through a drive belt at a 16 to 1 gear ratio.

Exhaust from the velocity turbine exit was plumbed in a sealed configuration to an inlet (compressor)of a Toyota CT 12 turbocharger being of a centrifugal flow construction. The compressed gas then was piped to a heat exchanger that is a air to air construction and in one of an end chamber of the heat exchanger, 6 nozzles spraying 10 micron water droplets at a flow rate of 5 litres a minute were positioned and with fluid pressure of 1500 pounds per square inch. At the other end of the heat exchanger a drain was placed in order to extract the coalesced mist which is cooled and coalesced with dissolved carbon dioxide, NOx and particulate matter under pressure for subsequent treatment. Residual gas mixture now stripped of a portion of the gases is passed to the Toyota Ct 12 turbine section from the heat exchanger forming what is conventionally described as a "Bootstrap" turbine system or a mass flow air cooling circuit.

This system was trialθd both with and without water injected.

The system under pressure ran at 8 pounds per square inch above atmospheric measured at the point of water injection, inside of the heat exchanger.

The percentage of CO2 without the water being added was a consistent 13.4% of gas stream

With constant pressure and water flow being added we were able to stabilize constant CO2 reading between 11.5% and 12.5% of gas stream.

Subsequent resulting concentrations as a percentage of CO2 during varying pressure / water flows were as low as 7,2% CO2 but slightly higher in other runs so that a slightly less than 50% is considered to be an amount of reduction that can be achieved.

Testing of the pressurized water sample showed the sample displaying similar effervescence characteristics to soda water, marked discoloration and when the water sample was tested for CO2, the reading was 80% CO2 of atmosphere within the gas space above the water after agitation. When pressure was released to atmosphere from the water sample the CO 2 rapidly boiled out and when again agitated it no longed bubbled.

What we have found therefore is a different technique for separating gases which is especially useful where CO2 is a predominant gas. in exhaust gases as in carbon based fuel driven engine exhausts or carbon or hydro carbon based burning furnaces.

Claims

1. A method of separating some gases from others including the steps of introducing an appropriate liquid in fine droplet form into a gas mixture so that a significant solution of the gas Into the liquid is first achieved then subsequently treating the droplets so that there is a coalescing of these so that some of the gas being targeted can be separated by being forced out of solution from the liquid and having the coalesced liquid separately located so the released gas can then be kept separate and appropriately dealt with.

2. A method of separating carbon dioxide from a mixture of gases which comprises the steps of inserting water or another liquid or liquids with a high solubility coefficient or affinity with the selected gas or gases as droplets at an insertion location into the gas solution contained in a chamber or passing along a passageway, the insertion being from one or more positions into or from within the passageway so that the fluid is substantially distributed through the gas mixture, and then cooling the gas liquid mixture by heat exchange and/or by injection of additional fluid effecting coalescing of the fluid droplets containing dissolved gases forming a fluid solution and then transferring the coalesced liquid to a further location to effect release of the dissolved gas or gases.

3. The method as in the immediately preceding claim further comprising the steps of then effect a lowering of pressure applying to the fluid containing dissolved gas and /or in the case of some fluids lowering of temperature or in the case of some fluids raising of temperature in each or either case to effect release therefrom of dissolved gases and then causing the depleted gas solution to be discharged or passed a further time through the process of fluid injection and removal of the fluid solution for the purpose of further removal of the selected gas or gases from the gas solution.

4. A method of effecting separation of gases including a solution of gases containing any one or more of the following; carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, benzene, formaldehyde and /or polycyclic hydrocarbons and/ or particulate matter including carbon and other sub-100 micron particulates from the flue or exhaust gases of a hydrocarbon combustion process which method comprises the steps of inserting water as steam and/or water droplets and/or water vapour at one or more than one location in a passageway containing the flue or exhaust gases before or after or before and after compression by a piston or turbme compressor or other compression process the Insertion being from one or more than one position into or from within the passageway so that the injected water is substantially mixed within the flue gases then effecting cooling by passage through a heat exchanger and/or injection of further water as droplets then the water mixture including dissolved gases, emulsions and solid particulates being removed as a condensate mixture from one point or more than one point in the passageway where the condensate mixture contains any of dissolved carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, benzene, formaldehyde and or polycyclic hydrocarbons and/or emulsions and/ or an admixed suspension of particulate matter including carbon and other sub-100 micron particulates which has accumulated and the condensate/emu « lsion/suspension is removed to a further location where the carbon dioxide and other gases are recovered by lowering the pressure and /or agitating the condensate to effect the release of dissolved carbon dioxide and other gases and then effecting that the solid particulates and emulsions are removed.

5. The method as in the immediately preceding claim further comprising the steps of effecting by passage of the fluid through a centrifuge device and/or filtration process and causing weak acids to be removed by chemical reaction with an alkali or alkalis which are consumed to produce insoluble salts which are removed by filtration or by passage of an electrical current through the solution and formation of an insoluble salt or insoluble salts by use of sacrificial electrodes and after removal of the condensate mixture the flue gas solution is then expanded by passage through an expansion turbine or expansion nozzle and as a result of cooling of the flue gas solution, further condensate mixture forms and this condensate mixture is removed and subjected to the same process of recovery of gases and particulates and the whole process of passage through the compression and water injection passageway can be repeated one or more times to increase the percentage of recovery and/or removal of the selected gas or gases including carbon dioxide.

6. A method for separately capturing carbon dioxide from a gas stream and then recovering carbon dioxide in separated gaseous form comprising injecting water as a micro mist into a gas stream containing CO2 and being in a heated environment, the shape of the passageway and/or the direction of the injection of water being arranged to limit back pressure to any oncoming gas stream, coalescing water droplets in a high pressure environment then collecting such coalesced water so as to be separate from remaining gas fluid mixture, then lowering pressure and thus cooling the gas stream and collect any further condensate, exposing the collected water to a partial pressure less than 1 Bar to release the otherwise dissolved CO2 into gaseous form, collect and compress the CO2 gas for reprocessing.

7. A method for separately capturing carbon dioxide from a gas stream and then recovering carbon dioxide in separated gaseous form further comprising providing an expanding passageway for down-streaming gases and introducing water in the vicinity of the expanding passageway whereby such water when introduced into the heated area will, when temperatures are above the boiling point of water, expand into steam or a mixture of water vapour and steam and will because of the expanding shape of the passageway be directed at the least in a downstream direction.

8. This implicitly then means that there will be less back-pressure as a result of this expanding passageway. With adjustments of the expanding shape and the volume and quantity of water and temperatures involved, this means that significant quantities of water can be introduced without undue increase in back pressure but also then the water can be directed into a separate location so that it can be subjected to treatment to effect coalescence of the droplets which have been previously exposed to the gases and would have transiently held dissolved gases therein.

9. A method comprising the steps of introducing water into a passageway in a downstream direction through a nozzle to induce by Bernoulli effect further suction that assists in extraction of exhaust or flue gases the nozzle being a a de Laval nozzle and positioned in a passageway and directed downstream the liquid being in the form of wet vapour being directed into the De laval nozzle at appropriate temperatures and pressures, whereby to effect and cause a prandtl-gauert singularity whereby to effect a significant further translation of heat into velocity of liquid directed downstream.

10. A method for separating gases from a gas mixture including steam water vapour and carbon dioxide which includes effecting introduction of water into the gases at least as steam and effecting a condensation or a coalescing subsequently of the resultant mixture.

11. A method as in any one of the preceding claims further comprised in that the mixture is introduced into a turbine to effect a or the condensation.

12. A method as in the immediately preceding claim further comprised in that the turbine is a Tesla or prandtl effect type turbine.

13. A method comprising or including the steps of effecting an injection of a fluid as a mixture containing fine droplets and/or fluid in gaseous form into a carbon dioxide containing gas stream; with further evaporation of some or ail of the mixture of injected fluid to gaseous vapour by the thermal energy of the gases and/or by compression of the gas before introduction of the fluid, then condensation or coalescing of the fluid into larger droplets in a heat exchanger and/or across a turbine thereby capturing the carbon dioxide in the fluid condensate.

14. The method as in any one of the preceding claims where the fluid consists substantially of water or water which includes water containing one or more contaminants or additives.

15. An arrangement for assisting in absorption of at least carbon dioxide where this is found in a source of incoming gases with a means to introduce water into a chamber with a further downstream condensation and removal of water containing a component of dissolved carbon dioxide.