AU2005205757B2

AU2005205757B2 - Process for the treatment of water and thermal treatment system

Info

Publication number: AU2005205757B2
Application number: AU2005205757A
Authority: AU
Inventors: Donald James Nicklin; Peter James Tait
Original assignee: Exergen Pty Ltd
Current assignee: Exergen Pty Ltd
Priority date: 2004-10-15
Filing date: 2005-08-31
Publication date: 2009-12-10
Anticipated expiration: 2025-08-31
Also published as: AU2005205757A1

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Name of Applicant(s): Exergen Pty Ltd, A.C.N. 099 189 , of 141-143 Wilson Street, Burnie, Tasmania 7320, AUSTRALIA Actual Inventor(s): Donald James Nicklin and Peter James Tait Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, of 1 Nicholson Street, Melbourne, Victoria 3000, Australia Invention Title: "Process for the treatment of water and thermal treatment system" Details of Associated Provisional Application No: 2004905999 The following statement is a full description of this invention, including the best method of performing it known to us: Q:\OPER\Axd\2005\Aug\I 2657880.doc - 30/8/05 C:\NR.otb\DCCWAM26904_l.DOC-ZWI U9 PROCESS FOR THE TREATMENT OF WATER AND THERMAL TREATMENT SYSTEM 5 The present invention relates to a process for the treatment of water, particularly a feed water containing organic contaminants. The process involves subjecting the feed water to a catalysed gasification reaction. More particularly, according to certain embodiments, the invention relates to a process and thermal treatment system for the hydrothermal dewatering of coal that includes subjecting a waste water stream emitted from the 10 dewatering process to a catalysed gasification reaction to gasify organic contaminants in the waste water stream. A number of industries require or involve the treatment of water that is laden with organic contaminants. Some examples include the treatment of sewerage sludge or distillery waste 15 (dunder). Likewise, a number of industries involve reactions that produce waste water streams that contain organic contaminants. For example, the hydrothermal dewatering of coal produces a waste water stream that includes organic contaminants that are leached out from the coal during the treatment. 20 The present invention aims to provide a process for the treatment of water containing organic contaminants that advantageously has very low operating costs and that may be operated continuously. Particularly, some embodiments of the invention advantageously provide a process for the treatment of water containing organic contaminants that has application in processes for the hydrothermal dewatering of coal. As a result, some 25 embodiments of the invention also advantageously provide thermal treatment systems and processes for the hydrothermal dewatering of coal where waste water may be treated and recirculated such that extraction of organics from the coal during the hydrothermal dewatering process is maximised. In certain embodiments, gas evolved during the catalysed gasification reaction is also collected and utilised in the hydrothermal dewatering 30 process.

C:\NRnbliCC\WAMU569004.1.DOC-Z0012 I 9 -2 According to one aspect of the invention there is provided a process for the treatment of feed water containing organic contaminants, the process including: feeding the feed water into a reactor; subjecting the feed water to a catalysed gasification reaction at elevated 5 temperature to at least partially gasify the organic contaminants, the majority of pressure required for the catalysed gasification reaction being generated by a hydrostatic head within the reactor; and emitting treated water from the reactor. 10 The reactor may take any suitable form, provided that the majority of pressure required for the catalysed gasification reaction is generated by a hydrostatic head within the reactor. According to a preferred embodiment, the reactor is a deep bore reactor including at least one reaction vessel, preferably two or more reaction vessels, extending to a depth below ground surface sufficient to generate the majority of the pressure, from a hydrostatic head, 15 required for the catalysed gasification reaction. The reactor may be a hydraulic equivalent of a U-tube mounted in a vertical passage, such as that described in United States Patent No. 3,606,999. However, it is preferred that the reactor include an arrangement such as that described in the applicant's International 20 Publication No. WO 02/098553 which is explicitly incorporated herein by reference in its entirety. This document discloses an arrangement for the treatment of materials where at least one vessel is located beneath the surface of the ground and is adapted to receive the materials to be treated. At least one of the vessels extends to a depth below the surface sufficient to generate pressure from a hydrostatic head in an inlet to or outlet from the 25 vessel, the inlet including at least two tubes. It will be appreciated from the disclosure of WO 02/098553 that the reactor may include a number of treatment vessels, such as autoclave vessels or reaction chambers, having any suitable configuration. 30 Preferably the vessels are located beneath the surface of the ground. Furthermore, each C:\NRPotbDCCWAM\569D4L.DOC-2/1 1/7209 -3 vessel may include as its inlet an array of tubes, for example 7 or more, 20 or more, from 20 to 200, between 50 and 200 or more than 200 tubes may form the inlet to each of the vessels. The inlet tubes will generally have a diameter in the range of from 25 to 100 mm, preferably about 50 mm. 5 If one or more of the vessels is located beneath the surface of the ground, it is preferred that the vessel or vessels extends at least 100 metres below the surface of the ground, more preferably at least 500 metres below the surface. 10 Further embodiments of the reactor for use in the process of this invention will be appreciated from the disclosure of WO 02/098553 which is, as previously noted, incorporated herein by reference. The process of the invention utilises a catalysed gasification reaction to gasify organic 15 contaminants within a feed water stream, for example a waste water stream. The gasification reaction may be any reaction that involves elevated temperature and pressure and the use of a suitable catalyst to gasify organic contaminants within a water stream. According to a particularly preferred embodiment, the catalysed gasification reaction is conducted using a Ni-supported carbon catalyst. Such catalysts have been found to be 20 particularly useful in catalysed gasification reactions to remove organic contaminants from waste water streams, such as from waste water streams emitted from processes for the hydrothermal dewatering of coal. Reference is particularly made to a paper "Hydrothermal Dewatering of Brown Coal and Catalytic Hydrothermal Gasification of the Organic Compounds Dissolved in the Water Using a Novel Ni/Carbon Catalyst", 25 Nakagawa et. al., Fuel 83 (2004) 719-725. This paper describes a nickel supported carbon catalyst in the form of a hard spherical particle in which a large amount of nickel is supported in highly dispersed state on a porous carbon. This paper is incorporated herein by reference in its entirety. However, for convenience the description of catalyst preparation provided in that paper is substantially reproduced in the following paragraph. 30 A metacrylic acid type ion exchange resin (Mitsubishi Chemical, WK- 11) was used as a C:WRPonbl\DCCWAM25690O4_LDOC-2/I 112009 -4 starting material. It was spherical in shape and its average diameter was about 0.5 mm. About 20 g of resin as received was treated in a beaker by about 300 ml of aqueous ammonia solution containing 52 g of NiSO 4 .6H 2 0 (0.67 mol/l) at room temperature for 24h. The treated resin was then washed by deionized water, followed by vacuum drying at 5 70*C for 24h. The dried resin was heated in a nitrogen atmosphere at the rate of 10 K/min to 500 *C to prepare the Ni/carbon catalyst. A SEM image of the Ni/carbon catalyst prepared shows it is a very hard particle of 0.2-0.4 mm in diameter, maintaining spherical shape. The X-ray diffraction pattern of the catalyst shows two broad peaks attributed to metallic Ni, indicating that the crystalline size of Ni was very small. The amount of Ni 10 supported by this method, which was estimated from the amount of ash of the catalyst, surprisingly reached as high as 47 wt%. The BET surface area was 170 m 2 /g and most of pores were 1-10 nm in diameter. The apparent density was as high as 1.9 g/cm 3 because of high Ni content. 15 The catalysed gasification reaction involves the evolution of gas, such as H 2 , CO 2 and CH 4 , due to gasification of the organic contaminants within the feed water stream. It is therefore preferred that the process include separating gas that is evolved during the catalysed gasification reaction. More preferably, at least part of the separated evolved gas is burned to fuel the catalysed gasification reaction. This advantageously maximises efficiency of 20 the system on the whole. Alternatively, the gas produced may be used for any desired purpose such as in a gas turbine/combined cycle plant for high efficiency power generation, as a gasification feedstock, or may be treated and supplied as natural gas, etc. In that regard, the gas produced will generally include a methane/carbon dioxide mixture, although it has been found that the composition of the gases can be heavily influenced by 25 the choice of catalyst and the operating pressure. For example, varying the catalyst and/or operating pressure may result in a rise in the proportion of hydrogen and a fall in the proportion of methane. As previously noted, the present invention is particularly suitable for use in a process for 30 the hydrothermal dewatering of coal. As such, according to another aspect of the invention there is provided a process for the hydrothermal dewatering of coal including: C :\RfrtblDCC\WAM2569004_ .DOC-20//1 2009 -5 providing a slurry of coal to be treated; passing the slurry of coal through a hydrothermal treatment zone at elevated temperature and pressure to produce a slurry of dewatered coal; separating excess water from the slurry of dewatered coal to produce a 5 thickened slurry of dewatered coal and a waste water stream; and drying the thickened slurry of dewatered coal to produce a coal product; wherein waste water from at least part of the waste water stream contains organic contaminants and is treated according to the process of the present invention. 10 Once again, the reactor used to treat at least part of the waste water stream is as described above, most preferably a reactor including an assembly as described in WO 02/098553 that is, as previously noted, incorporated herein by reference. In order to maximise efficiency of the process, it is preferred that at least part of the waste 15 water treated according to the process of the present invention is reticulated for slurrying with coal to be treated. In that regard, it is preferred that all of the waste water stream emitted from the dewatering treatment be fed into the reactor and treated to gasify organic contaminants in the waste water so that the waste water fed back for slurrying with the coal to be treated has a low content of organic contaminants. This advantageously encourages 20 more organics to leave the coal during the hydrothermal dewatering process compared to when organic-laden process water is used. Again, it is preferred that gas evolved during the catalysed gasification reaction is separated, more particularly this may be burned to fuel the catalysed gasification reaction 25 and/or the hydrothermal dewatering reaction. The gas evolved may also be used for other purposes as noted above. According to a further aspect of the invention, there is provided a thermal treatment system for the hydrothermal dewatering of coal including: 30 a hydrothermal treatment zone for dewatering a slurry of coal at elevated temperature and pressure to produce a slurry of dewatered coal; C:WRortbnDCC\WAM2569004_.DOC-2011/2009 -6 a settler for receiving the slurry of dewatered coal from the hydrothermal treatment zone, enabling the removal of excess water from the slurry of dewatered coal to produce a thickened slurry of dewatered coal and a waste water stream; a drying zone for solid liquid separation and drying of the thickened slurry 5 of dewatered coal to produce a coal product; and a reactor for receiving at least part of the waste water stream from the settler and catalytically gasifying organic contaminants in the waste water before emitting the waste water, the majority of the pressure required for the catalysed gasification reaction being generated by a hydrostatic head within the reactor. 10 The reactor may once again be as described above and is preferably that described in WO 02/098553. Similarly, although the hydrothermal treatment zone may include any treatment assembly known for the hydrothermal dewatering of coal, preferably includes an arrangement as described in WO 02/098553. 15 In a preferred embodiment, the thermal treatment system provides for heat exchange between waste water emitted from the reactor and waste water entering the reactor. This advantageously establishes heat recovery within the system and assists in maximising the efficiency of the system. In some embodiments, the thermal treatment system may include 20 a heat exchanger for receiving waste water emitted from the reactor and facilitating heat transfer to the wast water entering the reactor. As with the process for hydrothermal dewatering of coal described above, the thermal treatment system may advantageously include reticulation for reticulating waste water 25 emitted from the reactor back to the hydrothermal treatment zone for slurrying with coal to be treated. Similarly, the thermal treatment system may advantageously include gas recovery means for recovering gas evolved in the reactor during the catalysed gasification reaction. The gas recovery means may include at least one conduit for transporting gas evolved in the reactor to the hydrothermal treatment zone and/or to a heater for the reactor 30 such that the gas evolved can be burned as fuel for the hydrothermal dewatering reaction and/or the catalysed gasification reaction.

C:oUonbWCC\WAMJI56904.1.DOC-20/ 1/209 -7 A particular embodiment of the invention will now be described in more detail with reference to Figure 1 which schematically illustrates that embodiment. The embodiment relates specifically to a process for the hydrothermal dewatering of coal which is, as 5 described above, a particular application for the invention. Referring to Figure 1, a thermal treatment system 10 for the hydrothermal dewatering of coal is illustrated. The system includes a hydrothermal dewatering zone A and a catalysed gasification zone B. 10 The hydrothermal dewatering zone A includes a mixer 11 into which as-mined coal X is fed to form a slurry 12. The slurry 12 is fed to a reactor 13 of the kind described in WO 02/098553. The reactor 13 facilitates heat exchange between the slurry 12 being fed into the reactor and the slurry of dewatered coal 14 being emitted from the reactor. 15 Carbon dioxide produced during the reaction is then separated in a gas stream 15 while the slurry of dewatered coal 14 is passed to a settler 16. There, the slurry of dewatered coal is separated into untreated process water 17 that is fed to a holding tank and a thickened slurry of dewatered coal 18 that is transported for drying. 20 The catalysed gasification zone B facilitates the gasification of organic contaminants within the untreated process water 17. The gasification zone includes a reactor 19 including a fluidised bed of catalyst 20 through which the untreated process water 17 passes. Once again, the reactor 19 is one as described in WO 02/098553 and facilitates 25 heat exchange between untreated process water 17 entering the reactor 19 and treated process water 21 emitted from the reactor 19. The treated process water 21 that is emitted from the reactor 19 is then passed to a tank 22 where it is held for reticulation to the initial slurry 12 if necessary, while gases evolved 30 during the gasification reaction are separated through a gas stream 23. The gas stream 23 may be fed to a high efficiency power station 24 or may be fed out for other uses. For C:\NR rbnDCC\WAM\U UD4_L.DUC-ZWI iW -8 example, the gas stream 23 may be fed and burned as fuel for one or both of the reactors 13 and 19. An alternate reticulation stream is illustrated in dashed line in Figure 1. This will be the 5 water path if low methane production is desired. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common. general knowledge in Australia. 10 Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all the steps, features, compositions and 15 compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

Claims

1. A process for the treatment of feed water containing organic contaminants, the process including: 5 feeding the feed water into a reactor; subjecting the feed water to a catalysed gasification reaction at elevated temperature to at least partially gasify the organic contaminants, the majority of pressure required for the catalysed gasification reaction being generated by a hydrostatic head within the reactor; and 10 emitting treated water from the reactor.

2. A process according to claim 1, wherein the reactor is a deep bore reactor with a reaction vessel extending to a depth below ground surface sufficient to generate the majority of the pressure, from a hydrostatic head, required for the catalysed 15 gasification reaction.

3. A process according to claim 2, wherein the deep bore reactor includes two or more reaction vessels extending to a depth below ground surface sufficient to generate the majority of the pressure, from a hydrostatic head, required for the catalysed 20 gasification reaction.

4. A process according to claim 2 or 3, wherein the hydrostatic head is generated in an inlet to or outlet from the reaction vessel, the inlet including at least two tubes. 25

5. A process according to claim 4, wherein the inlet includes an array of from 20 to 200 tubes.

6. A process according to claim 4 or 5, wherein each inlet tube has a diameter in the range of from 25 to 100mm. 30 C:\NRribr\DCCWAM\256904.1.DOC-20Il/2009 -10

7. A process according to claim 5, wherein each inlet tube has a diameter of about 50mm.

8. A process according to any one of claims 2 to 7, wherein the or each reaction vessel 5 that extends to a depth below ground surface sufficient to generate the majority of the pressure, from a hydrostatic head, required for the catalysed gasification reaction extends at least 100m below the surface of the ground.

9. A process according to claim 8, wherein the or each said reaction vessel extends at 10 least 500m below the surface.

10. A process according to any one of claims I to 9, wherein the catalysed gasification reaction is conducted using a Ni-supported carbon catalyst. 15

11. A process according to any one of claims I to 10, wherein evolved gas is separated during the catalysed gasification reaction.

12. A process according to claim 11, wherein at least part of the separated evolved gas is burned to fuel the catalysed gasification reaction. 20

13. A process according to any one of claims I to 12, wherein the feed water is waste water from a hydrothermal dewatering process.

14. A process for the treatment of feed water containing organic contaminants, 25 substantially as hereinbefore described with reference to the accompanying drawing.

15. A process for hydrothermal dewatering of coal including: providing a slurry of coal to be treated; 30 passing the slurry of coal through a treatment zone at elevated temperature and pressure to produce a slurry of dewatered coal; C:\P tnb CC\WAM69004_tDOC-20/11/2009 -11 separating excess water from the slurry of dewatered coal to produce a thickened slurry of dewatered coal and a waste water stream; and drying the thickened slurry of dewatered coal to produce a coal product; wherein waste water from at least part of the waste water stream contains organic 5 contaminants and is treated according to the process of any one of claims 1 to 12 and 14.

16. A process according to claim 15, wherein at least part of the waste water treated according to the process of any one of claims 1 to 12 and 14 is reticulated for 10 slurrying with coal to be treated.

17. A process according to claim 15 or 16, wherein evolved gas is separated during the catalysed gasification reaction and at least part of the separated evolved gas is burned to fuel the hydrothermal dewatering. 15

18. A thermal treatment system for hydrothermal dewatering of coal including: a hydrothermal treatment zone for dewatering a slurry of coal at elevated temperature and pressure to produce a slurry of dewatered coal; a settler for receiving the slurry of dewatered coal from the hydrothermal 20 treatment zone, enabling the removal of excess water from the slurry of dewatered coal to produce a thickened slurry of dewatered coal and a waste water stream; a drying zone for solid liquid separation and drying of the thickened slurry of dewatered coal to produce a coal product; and a reactor for receiving at least part of the waste water stream from the settler 25 and catalytically gasifying organic contaminants in the waste water before emitting the waste water, the majority of pressure required for the catalysed gasification reaction being generated by a hydrostatic head within the reactor.

19. A thermal treatment system according to claim 18, including a heat exchanger for 30 receiving waste water emitted from the reactor and facilitating heat transfer to the waste water entering the reactor. C:\Pwtbl\DCC\WAMU56904LDOC-20/1 II209 - 12

20. A thermal treatment system according to claim 18 or 19, including reticulation for reticulating waste water emitted from the reactor back to the hydrothermal treatment zone for slurrying with coal. 5

21. A thermal treatment system according to claim 18, 19 or 20, including gas recovery means for recovering gas evolved in the reactor during the catalysed gasification reaction. 10

22. A thermal treatment system according to claim 21, wherein the gas recovery means includes at least one conduit for transporting gas evolved in the reactor to the hydrothermal treatment zone and/or to a heater for the reactor such that the gas evolved can be burned as fuel for the hydrothermal dewatering reaction and/or the catalysed gasification reaction. 15

23. A thermal treatment system for hydrothermal dewatering of coal, substantially as hereinbefore described with reference to the accompanying drawing.