WO2010119254A1

WO2010119254A1 - Carbon dioxide sequestration using aqueous hydroxide solution of alkali and alkaline earth metals

Info

Publication number: WO2010119254A1
Application number: PCT/GB2010/000758
Authority: WO
Inventors: David Joseph Philip Hogg
Original assignee: Csl Patents Limited
Priority date: 2009-04-15
Filing date: 2010-04-15
Publication date: 2010-10-21
Also published as: GB2481756A; GB201117914D0; GB0906390D0

Abstract

A method of carbon dioxide sequestration, the method including providing an aqueous solution of a group 1 metal hydroxide such as sodium and a group 2 metal hydroxide such as calcium in an elongate receptacle (10). A source material containing gaseous carbon dioxide (is) continuously passed into the receptacle (10), and the carbonate product formed by reaction of the carbon dioxide with the hydroxide is removed as a slurry or solution from one end of the receptacle (10).

Description

CARBON DIOXIDE SEQUESTRATION USING AQUEOUS

HYDROXIDE SOLUTION OF ALKALI AND ALKALINE

EARTH METALS

This invention concerns a method of carbon dioxide sequestration, and apparatus usable with such a method.

There is significant concern about the large quantity of carbon dioxide produced by human activity, and particularly the effects this may have on the earth's climate. A number of proposals have been provided for sequestrating carbon dioxide rather than allowing it to be emitted to the atmosphere, but such proposals have often not proved feasible.

The term 'carbonate product' when used in this specification is to be understood as including carbonates, bicarbonates and hydrogen carbonates.

According to the present invention there is provided a method of carbon dioxide sequestration, the method including providing an aqueous solution of a group 1 metal hydroxide and a group 2 metal hydroxide in a receptacle, continuously passing a source material containing gaseous carbon dioxide into the receptacle, and removing the carbonate product formed by reaction of the carbon dioxide with the hydroxide.

The group 1 metal may be sodium, and the group 2 metal may be calcium.

The source material may also include nitrogen oxides, and nitrates may be formed by reaction of the nitrogen oxides with the hydroxide, and the nitrates formed may be removed from the receptacle.

The source material may include sulphur oxides, and sulphates may be formed by reaction of the sulphur oxides with the hydroxide, and the sulphates formed may be removed from the receptacle.

The source material may include non aqueous soluble gases, which gases may be any of methane, nitrogen or oxygen. The source material may be supplied at above ambient pressure, and may be supplied at a pressure of up to 50 bar.

The source material may be warm, and may be at a temperature of between ambient temperature and 60⁰C.

The source material may be obtained from any of power station flue gases, oil or gas fuel combustion gases, cement manufacture, brewing, or from the waste stream of other chemical or biochemical processes.

Some or all of the hydroxide material may be obtained from fly ash, or as by-products from industrial processes.

The carbonate product thus formed may be removed from the receptacle as a slurry or a solution. The removal of carbonate product from the receptacle may be controlled.

The carbonate product removed from the receptacle may be dried. Insoluble calcium carbonate in a slurry in the carbonate product may be separated from the water in the slurry, and may be separated using a wiped film evaporation. Alternatively, the carbonate product may be separated from the water in the slurry using a Soxhlet extraction thimble.

The supply of each of the hydroxides into the receptacle may be controlled.

The supply of the source material into the receptacle may be controlled.

Conditions within the receptacle may be monitored, and the supply of the source material, the hydroxide materials, and/or the removal of the carbonate product may be controlled in response to the monitored conditions. In particular, the pressure in the receptacle may be monitored, and not allowed to exceed a predetermined maximum level, and the pressure may be reduced when required by removing material from the receptacle.

A pressure release valve may be provided on the receptacle to prevent the pressure therein exceeding a predetermined maximum value. The pressure release valve may be automatically operable and may be computer controlled.

The pressure release valve may permit non aqueous soluble gases to be evacuated from the receptacle, and the non aqueous soluble gases may be evacuated to a collector receptacle.

Some or all of the following conditions may be monitored: temperature, carbon dioxide concentration, pH, the amount of agitation.

One or more of these conditions may be monitored at several different locations in the receptacle.

The receptacle may be elongate. The carbonate product formed may be removed from one end of the receptacle, with the hydroxide being supplied into the other end of the receptacle. The source material may be supplied part way along the length of the receptacle.

Material within the receptacle may be agitated, and a flat blade radial turbine agitator may be used.

The receptacle may have a substantially non reactive interior, which may be formed of plastics material.

The receptacle may be in modular form such that different lengths of receptacle can be used as required. In some instances a greater proportion of group 2 hydroxide to group 1 hydroxide may be provided, there may be more than five times as much group 2 hydroxide than group 1 hydroxide, and there may be more than ten times as much group 2 hydroxide than group 1 hydroxide.

In other instances a greater proportion of group 1 hydroxide to group 2 hydroxide may be provided.

The invention also provides an apparatus usable with a method according to any of the preceeding twenty five paragraphs.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:-

Fig. 1 is a diagrammatic side view of apparatus according to the invention;

Fig. 2 is a diagrammatic side view of further apparatus according to the invention; and

Fig. 3 is a plan view of the apparatus of Fig. 2.

Fig. 1 of the drawings shows apparatus in the form of an elongate receptacle 10, which could for instance be in the order of 1m long. The receptacle 10 is made of steel and includes an inner non reactive plastics material liner 12. At the left hand end of the receptacle 10 as shown, an outlet 14 is provided which is controllable by an outlet valve 16, which may be of a sleeve or diaphragm type. A vent 18 is provided towards the left hand of the receptacle 10 as is a first monitoring arrangement 20. A similar second monitoring arrangement 22 is provided towards the right hand end of the receptacle 10 as shown. The monitoring arrangements 20, 22 measure inter alia pressure using a pressure transducer, and also pH. An agitator 24 which is shown diagrammatically, is provided towards the left hand end of the receptacle 10. The agitator 24 may be a flat blade radial turbine, with four or more vertical blades equally spaced around a disk. This agitator 24 allows a net flow of reaction mixture in a desired direction. The blades cause gas dispersion, allowing introduction of gas into the liquid phase effecting reaction.

An inlet 26 for source material extends through the right hand end of the receptacle and finishes towards the centre of the receptacle 10. The inlet 26 is controlled by a valve 28 located outside of the receptacle 10. First and second hydroxide inlets 30, 32 are provided extending into the right hand end of the receptacle 10 as shown, and are provided with respective control valves 34, 36. A pressure gauge 38 is provided on the receptacle 10 towards the right hand end thereof. The method of gas introduction is currently via a sparge tube and porous vitreous/glass frit, though other methods of gas introduction may be possible.

In use the receptacle 10 is filled with an aqueous solution of a group 1 hydroxide such as sodium hydroxide through the inlet 30, and a group 2 hydroxide aqueous solution such as is provided by calcium hydroxide through the inlet 32. A warmed supply of gaseous carbon dioxide is supplied at a temperature of up to 60⁰C under pressure at a pressure of up to 2.5bar through the inlet 26. The mixture within the receptacle 10 is mixed using the agitator 24.

Respectively sodium and calcium carbonate are formed and can be removed through the outlet 14. The carbonate may be a slurry or a solution dependent largely on the hydroxide material initially present and the proportions thereof, with calcium carbonate being largely insoluble. Where the pH of the solution drops below around 10.5, bicarbonate will be formed. The solution's pH may be controlled by monitoring the reagent addition rate, concentration of reagents, and/or mixing efficiency to provide a uniform solution. In particular, one or both of the control valves 34, 36 may be opened when the pH is between 8.0 and 11.00. The outlet valve 16 may be opened when the pH is between 7.0 and 7.4. These pH values may though be altered as required in particular situations. It is sought to maintain an equal displacement of material from the outlet 14, relative to material entering through the inlets 26, 30, 32. This is achieved in conjunction with measuring pressure in the receptacle 10 by the monitoring arrangements 20, 22.

The source material may also include nitrogen and/or sulphur oxides. The aqueous hydroxide solution can react with the nitrogen and sulphur oxides, and on a simultaneous and continuous basis as well as with the carbon dioxide, to form nitrates and sulphates in varying oxidation states of nitrogen or sulphur. These can be removed with the carbonate product.

The source material may also include non aqueous soluble gases such as methane, nitrogen and/or oxygen. A pressure release valve is provided for the receptacle which is computer controlled and can be used to evacuate the non aqueous soluble gases from the receptacle, and these gases can be collected in a separate collection receptacle.

Figs. 2 and 3 shows apparatus in the form of a wiped film evaporator 40. The evaporator 40 has three inlets 42 for receiving slurry from the outlet 14. The inlets 42 are each directed onto a respective belt 44 which passes respectively around three spaced vertical rollers 46. The configuration of how the belt 44 is looped around the outer two rollers 46 and passes to one side of the middle roller 46 is best seen in Fig. 3.

The evaporator 40 may be provided in a chamber to which a reduced pressure of say IOOmBar may be applied to reduce the boiling point of the water. Scrapers 48 are provided engageable with each of the belts 44 adjacent the right hand roller 46 as shown in Fig. 2, to urge material off the belts 44 to drop into a collecting receptacle 50. A distillation weir arrangement with three weirs 52 is provided above the belts 44 and rollers 46. In use, the slurry which will be calcium carbonate and/or calcium bicarbonate which is substantially free of sodium carbonate and sodium bicarbonate, will be passed onto the belts 44 and water will be evaporated therefrom. This will lead to substantially dry and sodium free calcium carbonate and/or bicarbonate being collected in the receptacle 50.

The solid collected material can thus be washed, to remove the soluble group 1 material, which can be quantitatively followed by in-line emission spectroscopy such as inductively coupled plasma (ICP). This then effects the separation of the two mineral streams, and allows recycling of the liquids.

As an alternative to the wiped film evaporator, carbonate solids could be removed from the output using a Soxhlet extraction thimble. The aqueous dilute slurry output is passed through the thimble to remove the insoluble carbonate. Once a thimble is full, it can be replaced by another on a rotating carousel, allowing the full thimble to be emptied for reuse.

The conditions within the receptacle are monitored at each end, and the respective inputs and output are controlled accordingly. For instance the rate of carbon dioxide input is controlled to correspond to the proportion of carbonate being removed. This can be monitored by pH control, and/or agitation. In many instances a significantly greater proportion of calcium hydroxide may be provided relative to sodium hydroxide.

Parameters which could be measured for example by infrared spectroscopy, can be used to detect the proportion of carbon dioxide present at each end of the apparatus. The pH control is important to provide the desired reaction to form carbonates. This can be controlled by the proportion of hydroxide being introduced into the receptacle. Agitation can be controlled to achieve efficient removal of carbon dioxide.

The carbon dioxide source can be from a wide range of sources for example power station flue gases, from combustion of oil and gas fuel, from cement manufacture, from brewing processes, or from other chemical or biochemical processes that generate carbon dioxide as a waste stream.

The invention is particularly usable for instance with coal mining. The coal can be burnt at a power station and the emissions can be captured using the above process to form a carbonate such as calcium carbonate. Such material could be transported back down and stored in the mine. The calcium carbonate formed is a stable product. Alternatively the carbonate material may be used in other processes, and could replace for instance the quarrying and mining of calcium carbonate as limestone.

Some or all of the hydroxide material may be obtained from fly ash, or other mineral sources such as by-products from industrial processes.

There is thus described a method and apparatus for sequestrating carbon dioxide, and therefore permitting various processes to be carried out without producing carbon dioxide emissions.

It is to be realised that a wide range of modifications can be made dependent on the source of the carbon dioxide. Conditions can be chosen as the processes and materials involved dictate. The receptacle could be any required size dependent on particular applications and the volume of source material. For instance significantly longer receptacles may be used in particular circumstances. The apparatus may be made to suit appropriate conditions and can be modular such that the length of the receptacle can be chosen as required.

A different type of agitator may be used. The pressure release valve may be automatically operable but not computer controlled. Other methods may be used for separating the carbonate materials from the slurry. Gas could be introduced into the receptacle in a different manner, and for instance a micro bubble generator could be used. This could be achieved by bubbling the gas through a frit or other suitable porous support. As the reaction which forms the basis for this invention is not catalytic, the cleanliness and source of the carbon dioxide reactant is not important. This means that the invention is usable in a very wide range of applications, with widely differing degrees of purity of carbon dioxide source and consequent compositions formed. The invention is therefore applicable to long term wide spread reductions in carbon dioxide emissions across a wide number of fields.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method of carbon dioxide sequestration, the method including providing an aqueous solution of a group 1 metal hydroxide and a group 2 metal hydroxide in a receptacle, continuously passing a source material containing gaseous carbon dioxide into the receptacle, and removing the carbonate product formed by reaction of the carbon dioxide with the hydroxide.

2. A method according to claim 1 , characterised in that the group 1 metal is sodium.

3. A method according to claims 1 or 2, characterised in that the group 2 metal is calcium.

4. A method according to any of the preceding claims, characterised in that the source material also includes nitrogen oxides, and nitrates are formed by reaction of the nitrogen oxides with the hydroxide.

5. A method according to claim 4, characterised in that the nitrates formed are removed from the receptacle.

6. A method according to any of the preceding claims, characterised in that the source material includes sulphur oxides, and sulphates are formed by reaction of the sulphur oxides with the hydroxide.

7. A method according to claim 6, characterised in that the sulphates formed are removed from the receptacle.

8. A method according to any of the preceding claims, characterised in that the source material includes non aqueous soluble gases.

9. A method according to claim 8, characterised in that the non aqueous souble gases are any of methane, nitrogen or oxygen.

10. A method according to any of the preceding claims, characterised in that the source material is supplied at above ambient pressure.

11. A method according to claim 10, characterised in that the source material is supplied at a pressure of up to 50 bar.

12. A method according to any of the preceding claims, characterised in that the source material is warm.

13. A method according to claim 12, characterised in that the source material is at a temperature of between ambient temperature and 60⁰C.

14. A method according to any of the preceding claims, characterised in that the source material is obtained from any of power station flue gases, oil or gas fuel combustion gases, cement manufacture, brewing, or from the waste stream of other chemical or biochemical processes.

15. A method according to any of the preceding claims, characterised in that some or all of the hydroxide material is obtained from fly ash, or as byproducts from industrial processes.

16. A method according to any of the preceding claims, characterised in that the carbonate product thus formed is removed from the receptacle as a slurry or a solution.

17. A method according to claim 16, characterised in that the removal of carbonate product from the receptacle is controlled.

18. A method according to claims 16 or 17, characterised in that the carbonate product removed from the receptacle is dried.

19. A method according to any of claims 16 to 18, characterised in that insoluble calcium carbonate in a slurry in the carbonate product is separated from the water in the slurry.

20. A method according to claim 19, characterised in that insoluble calcium carbonate in a slurry in the carbonate product is separated from the water in the slurry using a wiped film evaporation.

21. A method according to claim 19, characterised in that insoluble calcium carbonate in a slurry in the carbonate product is separated from the water in the slurry using a Soxhlet extraction thimble.

22. A method according to any of the preceding claims, characterised in that the supply of each of the hydroxides into the receptacle is controlled.

23. A method according to any of the preceding claims, characterised in that the supply of the source material into the receptacle is controlled.

24. A method according to any of the preceding claims, characterised in that conditions within the receptacle are monitored.

25. A method according to claim 24, characterised in that the supply of the source material, the hydroxide materials, and/or the removal of the carbonate product are controlled in response to the monitored conditions.

26. A method according to any of the preceding claims, characterised in that the pressure in the receptacle is monitored.

27. A method according to claim 26, characterised in that the pressure in the receptacle is not allowed to exceed a predetermined maximum level.

28. A method according to claim 27, characterised in that the pressure is reduced when required by removing material from the receptacle.

29. A method according to any of the preceding claims, characterised in that a pressure release valve is provided on the receptacle to prevent the pressure therein exceeding a predetermined maximum value.

30. A method according to claim 29, characterised in that the pressure release valve is automatically operable.

31. A method according to claim 30, characterised in that the pressure release valve is computer controlled.

32. A method according to any of claims 29 to 31, characterised in that the pressure release valve permits non aqueous soluble gases to be evacuated from the receptacle.

33. A method according to claim 32, characterised in that the non aqueous soluble gases are evacuated to a collector receptacle.

34. A method according to claim 24, or any of claims 25 to 33 when dependent on claim 24, characterised in that some or all of the following conditions are monitored: temperature, carbon dioxide concentration, pH, the amount of agitation.

35. A method according to claim 34, characterised in that one or more of these conditions are monitored at several different locations in the receptacle.

36. A method according to any of the preceding claims, characterised in that the receptacle is elongate.

37. A method according to claim 36, characterised in that the carbonate product formed is removed from one end of the receptacle, with the hydroxide being supplied into the other end of the receptacle.

38. A method according to claims 36 or 37, characterised in that the source material is supplied part way along the length of the receptacle.

39. A method according to any of the preceding claims, characterised in that material within the receptacle is agitated.

40. A method according to claim 39, characterised in that a flat blade radial turbine agitator is used

41. A method according to any of the preceding claims, characterised in that the receptacle has a substantially non reactive interior.

42. A method according to claim 41 , characterised in that the non reactive interior is formed of plastics material.

43. A method according to any of the preceding claims, characterised in that the receptacle is in modular form such that different lengths of receptacle can be used as required.

44. A method according to any of the preceding claims, characterised in that a greater proportion of group 2 hydroxide to group 1 hydroxide is provided.

45. A method according to claim 44, characterised in that there is more than five times as much group 2 hydroxide than group 1 hydroxide.

46. A method according to claim 45, characterised in that there is more than ten times as much group 2 hydroxide than group 1 hydroxide.

47. A method according to any of claims 1 to 43, characterised in that a greater proportion of group 1 hydroxide to group 2 hydroxide is provided.

48. An apparatus usable with a method according to any of the preceeding claims.