AU2003264182B2 - A system for catalytic combustion - Google Patents
A system for catalytic combustion Download PDFInfo
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- AU2003264182B2 AU2003264182B2 AU2003264182A AU2003264182A AU2003264182B2 AU 2003264182 B2 AU2003264182 B2 AU 2003264182B2 AU 2003264182 A AU2003264182 A AU 2003264182A AU 2003264182 A AU2003264182 A AU 2003264182A AU 2003264182 B2 AU2003264182 B2 AU 2003264182B2
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- 238000007084 catalytic combustion reaction Methods 0.000 title claims description 14
- 239000007789 gas Substances 0.000 claims description 133
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 84
- 239000000446 fuel Substances 0.000 claims description 72
- 238000000034 method Methods 0.000 claims description 49
- 230000003197 catalytic effect Effects 0.000 claims description 36
- 238000009423 ventilation Methods 0.000 claims description 32
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims description 22
- 239000003054 catalyst Substances 0.000 claims description 21
- 239000003245 coal Substances 0.000 claims description 21
- 238000005201 scrubbing Methods 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 13
- 238000002485 combustion reaction Methods 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 12
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims description 11
- 230000006835 compression Effects 0.000 claims description 10
- 238000007906 compression Methods 0.000 claims description 10
- 239000012530 fluid Substances 0.000 claims description 10
- 230000005611 electricity Effects 0.000 claims description 5
- 239000010953 base metal Substances 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 4
- 229910000510 noble metal Inorganic materials 0.000 claims description 4
- 239000002002 slurry Substances 0.000 claims description 4
- 239000000758 substrate Substances 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims 2
- 150000003464 sulfur compounds Chemical class 0.000 claims 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 14
- 238000001816 cooling Methods 0.000 description 9
- 235000010269 sulphur dioxide Nutrition 0.000 description 9
- 239000004291 sulphur dioxide Substances 0.000 description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 6
- 239000005864 Sulphur Substances 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 239000000567 combustion gas Substances 0.000 description 5
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- 239000003345 natural gas Substances 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- 239000010948 rhodium Substances 0.000 description 3
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 239000003915 liquefied petroleum gas Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Description
WO 2004/029433 PCT/AU2003/001275 A SYSTEM FOR CATALYTIC COMBUSTION FIELD OF INVENTION This invention relates to catalytic combustion. 5 BACKGROUND OF THE INVENTION A catalytic combustion gas turbine system has been developed to replace conventional industrial gas turbines, burning natural gas, but with ultra low NOx emissions. One of the features of this turbine is that 10 cooling is required at the inlet of the turbine because of the high inlet temperature (> 850 0 C), arising from combustion of high concentrations of methane. This cooling is achieved by bypassing a substantial amount of the air from the compressor discharge to the turbine inlet 15 and turbine first stage. However, if the air contains methane, this results in a large amount of uncombusted methane passing through the turbine and into the atmosphere. Not only is this an inefficient use of the methane, but it is also damaging to the environment and a 20 waste of energy. Another application of catalytic combustion turbine systems has been to generate electricity from waste gases, which have a lower concentration of methane than natural gas. However, previous attempts of this have 25 run into several difficulties; having to inject support fuel (eg. natural gas) into the catalytic combustor to maintain efficient combustion, not being able to efficiently handle gas streams with less than 2 mole% methane, having to excessively raise the pressure of the 30 gas stream thereby reducing the overall electrical output of the system, and having difficulty in controlling the gas temperature at the outlet of the combustor at a constant value below 800 0 C so that cooling at the inlet of the turbine is not required, and having problems in 35 handling the waste gas, which by its nature has a fluctuating composition. SUDMARY OF THE INVENTION WO 2004/029433 PCT/AU2003/001275 -2 Accordingly, it is desirable, if in one embodiment of the present invention, that there is provided a catalytic combustion gas turbine system which utilises a gas with a substantially constant and low 5 concentration of fuel. According to a first aspect of the present invention there is provided a system for providing fuel to drive a catalytic combustion gas turbine system the system for providing fuel comprising a mixer, having an outlet 10 stream and at least two inlet streams and a compressor, having an inlet stream, the outlet stream of the mixer being connected to the inlet stream of the compressor, wherein, during operation of the system, the at least two inlet streams are controlled so that the outlet stream of 15 the mixer has a substantially constant composition over time. Preferably, the outlet stream of the mixer has a low concentration of hydrocarbons. Preferably, the outlet stream of the mixer is 20 substantially a gas. Preferably, the outlet stream of the mixer has a low concentration of methane. Preferably, the outlet stream has a concentration of methane of 0.5 to 1.5 mole%. 25 Preferably, the outlet stream has a concentration of methane of approximately 1 mole%. Preferably, of the at least two inlet streams of the mixer, at least one inlet stream has a very low concentration of methane and at least one other inlet 30 stream has a high concentration of methane. Preferably, of the at least two inlet streams of the mixer, at least one inlet stream has a concentration of methane of 0 to 1.5 mole%, and at least one other inlet stream has a concentration of methane of over 20 mole%. 35 Preferably, the operating temperature of the mixer is approximately 20'C. Preferably, the operating pressure of the mixer WO 2004/029433 PCT/AU2003/001275 -3 is approximately atmospheric. Preferably, the compressor has a compression ratio of approximately 2. Preferably, the compressor has an outlet stream 5 which has a pressure of less than 3.5 bar (absolute). Preferably, the pressure of the outlet stream of the compressor is approximately 2 bar (absolute). Preferably, the temperature of the outlet stream with the compressor is 100 to 200 0 C. 10 Preferably, the compressor is an axial flow compressor. Alternatively, the compressor is a radial flow compressor. Preferably, at least one of the at least two 15 inlet streams of the mixer is a stream of ventilation air from a coal mine, having very low methane concentration. Preferably, the system further comprises a first scrubber, the first scrubber having an inlet stream and a gas outlet stream, the gas outlet stream being connected 20 to at least one of the at least two inlet streams of the mixer, and the inlet stream being the stream of ventilation air, wherein, the first scrubber removes particles from the ventilation air through a solid outlet stream. 25 Preferably, the first scrubber comprises a wet scrubber and filter. Preferably, the first scrubber removes particles greater than and equal to 0.50 micron in diameter. Preferably, the scrubber also removes sulphur 30 compounds through a sulphur outlet stream. Preferably, the first scrubber removes sulphur compounds, so that the concentration of hydrogen sulphide and sulphur dioxide in the gas outlet stream is no greater than 10ppm and 5ppm respectively. 35 Preferably, at least one other stream of the at least two inlet streams of the mixer is a stream of coal mine drainage gas.
WO 2004/029433 PCT/AU2003/001275 -4 Preferably, the system further comprises a second scrubber, the second scrubber having an inlet stream and a gas outlet stream, the gas outlet stream being connected to at least one other of the at least two inlet streams of 5 the mixer, and the inlet stream being the stream of coal mine drainage gas, wherein, the second scrubber removes particles from the drainage gas through a solid outlet stream. Preferably, the second scrubber comprises a wet 10 scrubber and filter. Preferably, the second scrubber removes particles greater than and equal to 0.50 micron in diameter. Preferably, the scrubber also removes sulphur compounds through a sulphur outlet stream. 15 Preferably, the second scrubber removes sulphur compounds, so that the concentration of hydrogen sulphide and sulphur dioxide in the gas outlet stream is no greater than 10ppm and 5ppm respectively. Preferably, the system further comprises a 20 reservoir, the reservoir having an outlet stream connected to the inlet stream of the compressor, and during operation of the system, the outlet stream of the reservoir has a substantially constant composition over time, wherein, the reservoir stores enough fluid to buffer 25 fluctuations in the composition of at least one inlet stream of the reservoir. Preferably, the reservoir stores a gas. Preferably, the outlet stream of the mixer is connected to the at least one inlet stream of the 30 reservoir, wherein the mixer and the reservoir are separate units. Alternatively, the mixer is large enough to act as the reservoir. Preferably, the operating temperature of the 35 reservoir is approximately 20 0 C. Preferably, the operating pressure of the reservoir is approximately atmospheric.
WO 2004/029433 PCT/AU2003/001275 -5 According to a second aspect of the present invention there is provided a system comprising: a compressor having an inlet stream and an outlet stream, a pre-heater having a process inlet stream and a 5 process outlet stream, a catalytic combustor having an inlet stream and an outlet stream and containing a catalyst, and a turbine having an inlet stream and an outlet stream, wherein, the outlet stream of the compressor is connected to the process inlet stream of the 10 pre-heater, the process outlet stream of the pre-heater is connected to the inlet stream of the catalytic combustor, and the outlet stream of the catalytic combustor is connected to the inlet stream of the turbine, and wherein, during operation of the system, the inlet stream of the 15 compressor has a substantially constant and low concentration of fuel. Preferably, the inlet stream of the compressor has a low concentration of hydrocarbons. Preferably, the inlet stream with the compressor 20 is substantially a gas. Preferably, the inlet stream of the compressor has a low concentration of methane. Preferably, the inlet stream of the compressor has a methane concentration of 0.5 to 1.5 mole%. 25 Preferably, the inlet stream of the compressor has a methane concentration of approximately 1 mole%. Preferably, the inlet stream of the compressor has a temperature of approximately 20*C. Preferably, the inlet stream of the compressor 30 has a pressure of approximately atmospheric. Preferably, the system further comprises a mixer, having an outlet stream connected to the inlet stream of compressor, wherein, during operation of the system at least two inlet streams to the mixer are controlled so 35 that the outlet stream has the substantially constant and low concentration of fuel. Preferably, of the at least two inlet streams of WO 2004/029433 PCT/AU2003/001275 -6 the mixer, at least one inlet stream has a very low concentration of methane and at least one other inlet stream has a high concentration of methane. Preferably, of the at least two inlet streams of 5 the mixer, at least one inlet stream has a concentration of methane of 0 to 1.5 mole% and at least one other inlet stream has a concentration of methane of over 20 mole%. Preferably, the compressor has a compression ratio of approximately 2. 10 Preferably, the outlet stream of the compressor has a pressure of less than 3.5 bar (absolute). Preferably, the pressure of the outlet stream of the compressor is approximately 2 bar (absolute). Preferably, the temperature of the outlet stream 15 of the compressor is 100 to 200 0 C. Preferably, the compressor is an axial flow compressor. Alternatively, the compressor is a radial flow compressor. 20 Preferably, at least one of the at least two inlet streams of the mixer is a stream of ventilation air from a coal mine. Preferably, the system further comprises a first scrubber, the first scrubber having an inlet stream and a 25 gas outlet stream, the gas outlet stream being connected to at least one of the at least two inlet streams of the mixer, and the inlet stream being the stream of ventilation air, wherein, the first scrubber removes particles greater than and equal to 0.50 micron in 30 diameter from the ventilation air through a solid outlet stream, and the first scrubber also removes sulphur compounds from the ventilation air through a sulphur outlet stream, so that the concentration of hydrogen sulphide and sulphur dioxide in the gas outlet stream is 35 no greater than 10ppm and 5ppm respectively. Alternatively, the first scrubber could be connected between the mixer and the compressor.
WO 2004/029433 PCT/AU2003/001275 -7 Preferably, at least one other stream of the at least two inlet streams of the mixer is a stream of coal mine drainage gas. Preferably, the system further comprises a second 5 scrubber, the second scrubber having an inlet stream and a gas outlet stream, the gas outlet stream being connected to at least one of the at least two inlet streams of the mixer, and the inlet stream being the stream of coal mine drainage gas, wherein the second scrubber removes 10 particles greater than and equal to 0.50 micron from the ventilation air through a solid outlet stream and also removes sulphur compounds from the ventilation air through a sulphur outlet stream so that the concentration of hydrogen sulphide and sulphur dioxide in the gas outlet 15 stream is no greater than 10ppm and 5 ppm respectively. Preferably, the system further comprises a reservoir, the reservoir having an outlet stream connected to the inlet stream of the compressor, and during operation of the system, the outlet stream of the 20 reservoir has a substantially constant composition over time, wherein, the reservoir stores enough fluid to buffer fluctuations in the composition of at least one inlet stream to the reservoir. Preferably, the reservoir stores the gas. 25 Preferably, the outlet stream of the mixer is connected to the at least one inlet stream of the reservoir, wherein the mixer and the reservoir are separate units. Alternatively, the mixer is large enough to act 30 as a reservoir. Preferably, the operating temperature of the reservoir is approximately 20 0 C. Preferably, the operating pressure of the reservoir is approximately atmospheric. 35 Preferably, the process outlet stream of the pre heater has a temperature of 475 to 535 0 C. Preferably, there is a very low pressure drop WO 2004/029433 PCT/AU2003/001275 -8 across the pre-heater, such that the pressure of the process outlet stream is substantially the same as the pressure of the process inlet stream. Preferably, the catalytic combustor has a 5 moderate space velocity and a low pressure drop. Preferably, the catalytic combustor contains a catalyst having a high activity and a high reaction surface area. Preferably, the activity of the catalyst is 10 50-20 0x10~ 7 mole/ (m 2 s). Preferably, the reaction surface area of the catalyst is 20-40m 2 /cm 3 . Throughout the specification, the term "activity" is understood to refer to the methane oxidation rate. 15 Preferably, the catalytic combustor is a honeycomb-type monolith reactor. Preferably, the catalyst used in the catalytic combustor is a noble metal catalyst. Preferably, the catalyst used in the catalytic 20 combustor is at least one of either palladium, platinum or rhodium. Preferably, the monolith is a ceramic, which acts as a substrate for a wash coat slurry of base metals on which the noble metal catalyst is placed. 25 Preferably, the catalytic combustor has a maximum continuous bed service temperature of 950*C. Preferably, the outlet stream for the catalytic combustor has a temperature of no more than 800*C. Preferably, the catalytic combustor has a 30 combustion efficiency of greater than 99%. Preferably, there is a very low pressure drop across the catalytic combustor, such that the pressure of the outlet stream is substantially the same as the pressure of the inlet stream. 35 Preferably, the inlet stream of the turbine has a temperature of less than 800*C. Preferably, the inlet stream of the turbine has a WO 2004/029433 PCT/AU2003/001275 -9 temperature of approximately 780*C. Preferably, the outlet stream of the turbine has a temperature of approximately 630 0 C. Preferably, the outlet stream of the turbine has 5 a pressure slightly above atmospheric. Preferably, the turbine does not require cooling air from the outlet stream of the compressor to cool the inlet scroll and the first stage of the turbine. Preferably, the turbine has cooling oil for 10 cooling the shaft and the bearings. Preferably, the turbine is an axial flow turbine. Alternatively, the turbine is a radial flow turbine. Preferably, the turbine is used to drive the 15 compressor. Preferably, the system further comprises a generator, which is connected to the turbine, wherein the generator converts the shaft work produced by the turbine into electrical energy. 20 Alternatively, the turbine comprises two turbines based on a split-shaft cycle such that the first turbine drives the compressor, and the second turbine is connected to the generator. Preferably, the system further comprises a 25 recuperator to recover some of the energy in the outlet stream of the turbine. Preferably, the recuperator and the pre-heater form a single integral unit, wherein, the pre-heater has a heating inlet stream and a heating outlet stream, the 30 heating inlet stream being connected to the outlet stream of the turbine, such that the outlet stream of the turbine is used to heat the outlet stream of the compressor. Preferably, the pre-heater is a plate heat exchanger. 35 Alternatively, the pre-heater is a fin-tube heat exchanger. Alternatively the pre-heater and the recuperator WO 2004/029433 PCT/AU2003/001275 - 10 are separate units such that the outlet stream of the compressor is heated in the pre-heater by heating means other than using the outlet stream of the turbine. Preferably, the system further comprises a heat 5 recovery boiler, the boiler having an inlet stream connected to the heating outlet stream of the pre-heater, wherein the boiler is adapted, in use, to recover energy from the turbine outlet stream. Preferably, the system further comprises a pre 10 burner, having an inlet stream, an outlet stream and a start-up fuel stream, the inlet stream being connected to the process outlet stream of the pre-heater, and the outlet stream being connected to the inlet stream of the catalytic combustor, wherein the pre-burner is used to 15 combust the start-up fuel stream during start-up of the turbine and during low load operation. Preferably, the start-up fuel is a hydrocarbon. Preferably, the start-up fuel is liquid petroleum gas. 20 Preferably, during normal operation of the system, the start-up fuel stream has a flow rate of 0, and the process outlet stream of the pre-heater passes through the pre-burner unreacted. According to a third aspect of the present 25 invention there is provided a method of producing a gas with a substantially constant and low concentration of fuel, the method comprising the steps of specifying a desired concentration of fuel in the outlet stream of a mixer, mixing at least one stream with a very low 30 concentration of fuel with at least one stream with a high concentration of fuel in the mixer and controlling the flow rate of the at least one stream with a high concentration of fuel to meet the desired concentration of fuel in the outlet stream of the mixer. 35 Preferably, the fuel is a hydrocarbon fuel. Preferably, the fuel is methane. Preferably, the desired concentration of methane WO 2004/029433 PCT/AU2003/001275 - 11 is 0.5 to 1.5 mole%. Preferably, the desired concentration of methane is approximately 1 mole%. Preferably, the at least one stream with a very 5 low concentration of fuel, has a concentration methane of 0 to 1.5 mole%. Preferably, the at least one stream with a high concentration of fuel has a concentration methane of over 20 mole%. 10 Preferably, the at least one stream with a very low concentration of fuel is a stream of ventilation air from a coal mine. Preferably, the at least one stream with a high concentration of fuel is a stream of coal mine drainage 15 gas. Preferably, the method further comprises the step of scrubbing the ventilation air to remove particles using a first scrubber. Preferably, the method further comprises the step 20 of scrubbing the ventilation air to remove particles greater than and equal to 0.50 micron in diameter using the first scrubber. Preferably, the method further comprises the step of scrubbing the ventilation air to remove sulphur 25 compounds using the first scrubber. Preferably, the method further comprises the step of scrubbing the ventilation air to remove sulphur compounds using the first scrubber so that the first scrubber has a gas outlet stream which has a concentration 30 of hydrogen sulphide and sulphur dioxide of no greater than l0ppm and 5ppm respectively. Preferably, the method further comprises the step of scrubbing the coal mine drainage gas to remove particles using a second scrubber. 35 Preferably, the method further comprises the step of scrubbing the coal mine drainage gas to remove particles greater than and equal to 0.50 micron in WO 2004/029433 PCT/AU2003/001275 - 12 diameter, using the first scrubber. Preferably, the method further comprises the step of scrubbing the coal mine drainage gas to remove sulphur compounds using the second scrubber. 5 Preferably, the method further comprises the step of scrubbing the coal mine drainage gas to remove sulphur compounds using the second scrubber so that the second scrubber has a gas outlet stream which has a concentration of hydrogen sulphide and sulphur dioxide of no greater 10 than 10ppm and 5ppm respectively. Preferably, the method further comprises the step of storing the gas in a reservoir. Preferably, the mixer is large enough to act as the reservoir. 15 Alternatively, the outlet stream of the mixer is connected to an inlet stream of the reservoir, wherein the mixer and the reservoir are separate units. According to a fourth aspect of the present invention there is provided a method of producing 20 electricity, the method comprising the steps of, mixing at least two gas streams to produce a process gas stream with a substantially constant and low fuel concentration prior to, compressing the process gas stream, preheating the process gas stream, combusting the process gas stream in 25 the presence of a catalyst, expanding the process gas stream in a turbine to produce shaft work, converting the turbine shaft work to electricity using a generator. Preferably, the step of mixing at least two gas streams, comprises the method of producing a gas with a 30 low concentration of fuel in accordance with the third aspect of the present invention. Preferably, the process gas stream is compressed to 1.5 to 3.5 bar (absolute). Preferably, the process gas stream is compressed 35 to approximately 2 bar (absolute). Preferably, the process gas stream is preheated to 475 to 535 0
C.
WO 2004/029433 PCT/AU2003/001275 - 13 Preferably, the catalyst is a noble metal catalyst. Preferably, the catalyst is at least one of either palladium, platinum or rhodium. 5 Preferably, the catalyst is placed on a ceramic monolith, which acts as a substrate for wash coat slurry of base metals. Preferably, a stream includes a fluid in a conduit. 10 The words "comprising, having including" should be interpreted in an inclusive sense, meaning that additional features may also be added. Variations and modifications can be made in respect of the invention described above and defined in 15 the following statement of claim. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 20 Figure 1 is a block diagram of a catalytic combustion gas turbine system. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to Figure 1, a preferred embodiment of a catalytic combustion gas turbine system 25 comprises a compressor 10, a recuperator 11, a pre-burner 12, a catalytic combustor 13, a turbine 14, a generator 15, a mixer 16, and first and second scrubbers 17, 18 thereby forming a power generation system which can be powered with approximately 1 mole% methane (maximum 1.5 30 mole%, minimum 0.5 mole%). The system is predominantly powered by the methane in the ventilation air from a coal mine 21. The ventilation air is scrubbed in the first scrubber 17, to remove dust particles greater than and equal to 0.50 35 micron in diameter. The first scrubber 17 also removes hydrogen sulphide and sulphur dioxide so that the concentration of these compounds does not exceed the -14 maximum allowable concentration in the system, which is l0ppm for hydrogen sulphide and 5ppm for sulphur dioxide. Exceedance of the maximum allowable concentrations can lead to fouling of the system components and deactivation of the 5 catalyst in the catalytic combustor. Having been scrubbed in the first scrubber 17, the ventilation air then enters the mixer 16 through a first inlet 22. Because the concentration of methane in the ventilation air 21 can vary between 0 and 1.5 mole%, it is necessary to 10 mix it with another gas so as to provide a gas with nearly constant methane concentration over time to the compressor 10. This is achieved using coal mine drainage gas 20, which is also subjected to a similar scrubbing operation in the second scrubber 18. 15 The second scrubber 18, removes dust particles and hydrogen sulphide and sulphur dioxide to the same levels as the first scrubber 17, before the drainage gas 20 enters the mixer 16 through a second inlet 23. The drainage gas has a methane concentration of over 20 mole%. 20 The mixer 16 operates at approximately 200C and atmospheric pressure. The amount of drainage gas 20 that is mixed with the ventilation air 21 is controlled so that at the mixer's outlet 24, the concentration of methane in the gas is generally constant over time. 25 The system further comprises a reservoir 70 which is connected to the outlet of the mixer 24. The reservoir 70 stores a large amount of the mixed gas at approximately 20'C and atmospheric pressure. The purpose of the reservoir is to buffer the downstream components of the 30 system from possible fluctuations in the concentration of methane in the gas from the outlet 24 of the mixer 16. The gas flows from the outlet of the reservoir to the inlet 25 of the compressor 10. The compressor 10 has a compressor ratio of approximately 2. This means that the 35 pressure of the gas at the outlet 26 of the compressor 10, will be approximately 2 bar. For efficient operation of the system, the pressure at the outlet 26 of the WO 2004/029433 PCT/AU2003/001275 - 15 compressor 10 should be no greater than 3.5 bar. The compressor 10 can be either an axial flow compressor or a radial flow compressor. The temperature of the gas at the outlet 26 of the compressor 10 will be 100 to 200 0 C. 5 From the outlet 26 of the compressor 10, the gas flows to the primary inlet 27 of the recuperator 11. The recuperator heats the gas so that at the primary outlet 28 of the recuperator 11, the temperature of the gas is between 475 and 535 0 C. The recuperator 11 operates with a 10 very low pressure drop across the primary inlet 27 and the primary outlet 28, so that the pressure of the primary outlet 28 is very similar to the pressure of the primary inlet 27. Whilst any heating means can be used to heat the gas in the recuperator 11, for efficient energy usage, 15 the present invention utilises the gas exiting the turbine 14 through outlet 35. This gas enters the recuperator 11 through a secondary inlet 36, where it transfers energy to the gas entering through the primary inlet 27, before exiting the recuperator 11 through the secondary outlet 20 37. This transfer of energy is achieved without any direct physical contact between the two gases, using either a plate heat exchanger or a fin-tube heat exchanger. The gas exiting the recuperator 11 through 25 primary outlet 28, then flows into the pre-burner 12 through an inlet 29. During normal continuous operation of the system, the gas flows through the pre-burner 12 without any change in its composition, temperature, pressure or other properties, such that the gas exits the 30 pre-burner 12 through outlet 31 unchanged from the gas that entered through inlet 29. The pre-burner 12 is only operated during the start-up of the system and during low load operation. During these instances, start-up fuel such as LPG is injected into the pre-burner through the 35 start-up fuel inlet 30. The pre-burner 12 is then operated to facilitate partial combustion of both the start-up fuel and the gas entering through inlet 29, WO 2004/029433 PCT/AU2003/001275 - 16 before complete combustion occurs in the catalytic combustor 13. The gas exiting the pre-burner 12 through outlet 31 flows into the catalytic combustor 13 through an inlet 5 32. The catalytic combustor 13 is a honeycomb-type monolith reactor. Monoliths have a large open frontal area resulting in a low pressure drop, which is necessary for the required moderate space velocities of the system. Nobel metal catalysts are used in the catalytic combustor 10 13. The ceramic monolith acts as a substrate for a wash coat slurry of base metals, such as alumina and ceria, on which the nobel metal catalyst such as palladium, platinum or rhodium are placed. The maximum continuous bed service temperature can be 950 0 C, but for short periods can reach 15 up to 1050 0 C. The catalytic combustor 13 has a combustion efficiency of over 99%. The gas exiting the combustor 13 through outlet 33 has a temperature of equal to or less than 800 0 C and a pressure which is similar to that of the gas entering the catalytic combustor through inlet 32. 20 The similar pressure of the gas at the outlet 33 to the inlet 32 is a result of the low pressure drop across the catalytic combustor 13. The gas from the outlet 33 of the catalytic combustor 13 enters the turbine 14 through an inlet 34. 25 The temperature of the gas at the inlet 34 should be no greater than 800*C, and is generally controlled to be approximately 780 0 C. If the temperature of the gas becomes elevated above 800 0 C, then cooling of the inlet scroll and the first stage of the turbine using gas from 30 outlet 26 of the compressor 10 would be required. However, it is a feature of the preferred embodiments of the present invention that such cooling is not required. Cooling oil is supplied to cool the shaft and bearings. The gas is expanded in the turbine 14 to produce 35 shaft work, resulting in the gas exiting the turbine 14 through outlet 35 having a temperature of approximately 630 0 C and a pressure of slightly above atmospheric. Some -17 of the shaft work of the turbine 14 is used to drive the compressor 10 through the connection 39. The remaining shaft work is converted into electrical energy by the generator 15 which is connected by 38 to the turbine 14. 5 Alternatively, the turbine 14 may comprise two turbines which operate on a split shaft cycle. The first turbine is used to drive the compressor 10 and the second turbine is connected to the generator 15. The turbine (s) 14 can be either an axial flow turbine (s) or a radial flow turbine (s). 10 The system also includes a heat recovery boiler. The gas exiting the secondary outlet 37 of the recuperator 11 enters the heat recovery boiler 50, where it is processed to recover as much of the remaining energy in the gas as possible. In the specification the term "comprising" shall be 15 understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations 20 on the term "comprising" such as "comprise" and "comprises". The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art forms part of the 25 common general knowledge in Australia.
Claims (33)
1. A method for catalytic combustion of a low concentration fuel comprising: compressing a substantially constant low concentration inlet fuel at a compression 5 ratio of no greater than 3.5 to form a compressed fuel; pre-heating the compressed fuel to form a pre-heated compressed fuel; combusting the pre-heated compressed fuel in the presence of a catalyst at a combustion temperature of no greater than 800 0 C to form a gas stream; expanding the gas stream in a turbine, at least part of said gas stream being ) recirculated, after expansion, for pre-heating of said compressed fuel.
2. A method as claimed in claim 1, wherein said inlet fuel is compressed at a compression ratio of 1.5 to 3.5. 5
3. A method as claimed in claim 1 or 2, wherein said inlet fuel is compressed at a compression ratio of approximately 2.
4. A method as claimed in any one of the preceding claims, wherein said compressed fuel has a temperature of 100 to 200 0 C prior to pre-heating.
5. A method as claimed in any one of the preceding claims, wherein the compressed fuel is pre heated to a temperature of 475 to 535 0 C.
6. A method as claimed in any one of the preceding claims, wherein said gas stream resulting 5 from combustion of said pre-heated compressed fuel has a temperature of approximately 780 0 C and said at least part of said gas stream being recirculated, after expansion, for pre heating of said compressed fuel has a temperature of approximately 630 0 C.
7. A method as claimed in any one of the preceding claims, wherein said inlet fuel comprises a 0 gas with a methane concentration of 0.5 to 1.5 mole%.
8. A method as claimed in any one of the preceding claims, wherein said inlet fuel comprises a gas with a methane concentration of approximately 1 mole%. 15
9. A method as claimed in claim 7 or 8, wherein said inlet fuel comprises a mixture of a first gas and a second gas, said method further comprising mixing said first gas and said second gas to form said substantially constant low concentration inlet fuel.
10. A method as claimed in claim 9, wherein said first gas has a methane concentration of 0 to 1.5 to mole% and said second gas has a methane concentration of over 20 mole%.
11. A method as claimed in claim 9 or 10, wherein said first gas is ventilation air from an underground coal mine and said second gas is drainage gas from an underground coal mine. -19
12. A method as claimed in claim 11, further comprising scrubbing said ventilation air and said drainage gas prior to mixing. 5
13. A method as claimed in claim 12, wherein said scrubbing removes particles of greater than and equal to 0.5 micron in diameter from said ventilation air and said drainage gas.
14. A method as claimed in claim 13, wherein said scrubbing removes sulfur compounds from said ventilation air and said drainage gas respectively, such that the concentration of 3 hydrogen sulfide in said first gas and said second gas after scrubbing is no greater than 10ppm and that the concentration of sulfur dioxide in said first gas and second gas after scrubbing is no greater than 5ppm.
15. A method as claimed in any one of the preceding claims, further comprising converting turbine 5 shaft work resulting from expansion of said gas stream in said turbine to electricity using a generator.
16. A method as claimed in claim 15, wherein at least a portion of said electricity generated is used to power a compressor used for compression of said inlet fuel.
17. A catalytic combustion system comprising: a source of substantially constant low concentration inlet fuel; a compressor for compressing the substantially constant low concentration inlet fuel; a pre-heater in fluid communication with said compressor, said pre-heater receiving 5 compressed fuel from said compressor; a catalytic combustor in fluid communication with said pre-heater, said catalytic combustor receiving pre-heated compressed fuel from said pre-heater and combusting same in the presence of a catalyst; and a turbine in fluid communication with said catalytic combustor and said pre-heater, 30 said turbine receiving a gas stream resulting from combustion of the pre-heated compressed fuel, at least part of said gas stream being recirculated from said turbine to said pre-heater; wherein said compressor operates at a compression ratio of no greater than 3.5 and wherein said gas stream received by said turbine has a temperature of less than 800 0 C. 35
18. A system as claimed in claim 17, wherein said compressor operates at a compression ratio of 1.5 to 3.5.
19. A system as claimed in claim 17 or 18, wherein said compressor operates at a compression ratio of approximately 2. 10 - 20
20. A system as claimed in any one of claims 17 to 19, wherein said inlet fuel comprises a mixture of a first gas and a second gas, said system further comprising a mixer for mixing said first gas and said second gas. 5
21. A system as claimed in claim 20, further comprising a reservoir disposed between said mixer and said compressor, said reservoir containing a mixture of said first and second gases and acting as a buffer to possible fluctuations in fuel concentration of said first and second gases, thereby ensuring the supply of said substantially constant, low concentration inlet fuel to said compressor.
22. A system as claimed in claim 20 or 21, wherein said first gas is ventilation air from an underground coal mine and said second gas is drainage gas from an underground coal mine.
23. A system as claimed in claim 22, further comprising a first scrubber for scrubbing said 5 ventilation air and a second scrubber for scrubbing said drainage gas.
24. A system as claimed in claim 23, wherein said first and second scrubbers remove particles of greater than and equal to 0.5 micron in diameter from said ventilation air and said drainage gas, and wherein said first and second scrubbers remove sulfur compounds from said I ventilation air and said drainage gas respectively, such that the concentration of hydrogen sulfide in gas outlet streams of the first and second scrubbers is no greater than 10ppm and that the concentration of sulfur dioxide in gas outlet streams of the first and second scrubbers is no greater than 5ppm. 5
25. A system as claimed in any one of claims 17 to 24, wherein said catalytic combustor contains a catalyst having an activity of 50x10 7 to 200x10- 7 mole/m 2 s and a reaction surface area of 20 to 40 m 2 /cm 2 .
26. A system as claimed in any one of claims 17 to 25, wherein said catalytic combustor is a W honeycomb-type monolith catalytic combustor.
27. A system as claimed in claim 26, wherein said honeycomb-type monolith catalytic combustor comprises a ceramic monolith which acts as a substrate for a wash coat slurry of base metals on which a noble metal catalyst is placed. 15
28. A system as claimed in any one of claims 17 to 27, further comprising a pre-burner in fluid communication with said pre-heater and said catalytic combustor, said pre-burner having a start up fuel inlet that, during start up of said system, supplies a start up fuel to said pre-burner which is combusted to heat compressed fuel recieved from said compressor, via said pre t0 heater, to provide heated compressed fuel to the catalytic combustor during start up of the system. - 21
29. A system as claimed in any one of claims 17 to 28, wherein said compressed fuel has a temperature of 100 to 200 0 C prior to pre-heating, and wherein the compressed fuel is pre heated to a temperature of 475 to 535 0 C. 5
30. A system as claimed in any one of claims 17 to 29, wherein said gas stream resulting from combustion of said pre-heated compressed fuel has a temperature of approximately 780*C and said at least part of said gas stream being recirculated, after expansion, for pre-heating of said compressed fuel has a temperature of approximately 630*C. 3
31. A catalytic combustion system for combustion of ventilation air and drainage gas from an underground coal mine, said system comprising: a first scrubber for scrubbing ventilation air received from the underground coal mine and a second scrubber for scrubbing drainage gas received from the underground coal mine; a mixer located down stream of said first scrubber and said second scrubber for 5 mixing said drainage gas with said ventilation air; a controller for controlling the amount of drainage gas mixed with said ventilation air such that a fuel mixture comprising a substantially constant concentration of 0.5 to 1.5 mole% methane is emitted from the mixer; a reservoir located down stream of said mixer, said reservoir containing the fuel D mixture emitted from the mixer and acting as a buffer to possible fluctuations in fuel concentration of said ventilation air and said drainage gas, thereby ensuring the supply of a substantially constant low concentration fuel; a compressor for compressing said substantially constant low concentration fuel, said compressor operating at a compression ratio of no greater than 3.5; 5 a pre-heater in fluid communication with said compressor, said pre-heater receiving compressed fuel from said compressor; a catalytic combustor in fluid communication with said pre-heater, said catalytic combustor receiving pre-heated compressed fuel from said pre-heater and combusting same in the presence of a catalyst; and 30 a turbine in fluid communication with said catalytic combustor and said pre-heater, said turbine receiving a gas stream having a temperature of less than 800*C resulting from combustion of the pre-heated compressed fuel, at least part of said gas stream being recirculated from said turbine to said pre-heater. 35
32. A method for catalytic combustion of a low concentration fuel, substantially as hereinbefore described with reference to Figure 1.
33. A catalytic combustion system, substantially as hereinbefore described with reference to Figure 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2003264182A AU2003264182B2 (en) | 2002-09-27 | 2003-09-26 | A system for catalytic combustion |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2002951703 | 2002-09-27 | ||
| AU2002951703A AU2002951703A0 (en) | 2002-09-27 | 2002-09-27 | A method and system for a combustion of methane |
| AU2003264182A AU2003264182B2 (en) | 2002-09-27 | 2003-09-26 | A system for catalytic combustion |
| PCT/AU2003/001275 WO2004029433A1 (en) | 2002-09-27 | 2003-09-26 | A system for catalytic combustion |
Publications (2)
| Publication Number | Publication Date |
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| AU2003264182A1 AU2003264182A1 (en) | 2004-04-19 |
| AU2003264182B2 true AU2003264182B2 (en) | 2009-05-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2003264182A Expired AU2003264182B2 (en) | 2002-09-27 | 2003-09-26 | A system for catalytic combustion |
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| AU (1) | AU2003264182B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3957464A (en) * | 1974-04-25 | 1976-05-18 | Teller Environmental Systems, Inc. | Process for removing particulates from a gas |
| US4067190A (en) * | 1975-09-29 | 1978-01-10 | Westinghouse Electric Corporation | Catalytic gas turbine combustor with a fuel-air premix chamber |
| US5216876A (en) * | 1990-11-05 | 1993-06-08 | Consolidated Natural Gas Service Company, Inc. | Method for reducing nitrogen oxide emissions from gas turbines |
| US5407647A (en) * | 1994-05-27 | 1995-04-18 | Florida Scientific Laboratories Inc. | Gas-scrubber apparatus for the chemical conversion of toxic gaseous compounds into non-hazardous inert solids |
| EP1040947A2 (en) * | 1999-04-01 | 2000-10-04 | Otto Egelhof GmbH & Co. | Vehicle air conditioner |
| WO2001042636A1 (en) * | 1999-12-13 | 2001-06-14 | Exxon Chemical Patents Inc. | Method for utilizing gas reserves with low methane concentrations for fueling gas turbines |
| WO2001042400A1 (en) * | 1999-12-13 | 2001-06-14 | Exxon Chemical Patents Inc. | Method for utilizing gas reserves with low methane concentrations and high inert gas concentrations for fueling gas turbines |
| US6393821B1 (en) * | 1998-08-21 | 2002-05-28 | Edan Prabhu | Method for collection and use of low-level methane emissions |
-
2003
- 2003-09-26 AU AU2003264182A patent/AU2003264182B2/en not_active Expired
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3957464A (en) * | 1974-04-25 | 1976-05-18 | Teller Environmental Systems, Inc. | Process for removing particulates from a gas |
| US4067190A (en) * | 1975-09-29 | 1978-01-10 | Westinghouse Electric Corporation | Catalytic gas turbine combustor with a fuel-air premix chamber |
| US5216876A (en) * | 1990-11-05 | 1993-06-08 | Consolidated Natural Gas Service Company, Inc. | Method for reducing nitrogen oxide emissions from gas turbines |
| US5407647A (en) * | 1994-05-27 | 1995-04-18 | Florida Scientific Laboratories Inc. | Gas-scrubber apparatus for the chemical conversion of toxic gaseous compounds into non-hazardous inert solids |
| US6393821B1 (en) * | 1998-08-21 | 2002-05-28 | Edan Prabhu | Method for collection and use of low-level methane emissions |
| EP1040947A2 (en) * | 1999-04-01 | 2000-10-04 | Otto Egelhof GmbH & Co. | Vehicle air conditioner |
| WO2001042636A1 (en) * | 1999-12-13 | 2001-06-14 | Exxon Chemical Patents Inc. | Method for utilizing gas reserves with low methane concentrations for fueling gas turbines |
| WO2001042400A1 (en) * | 1999-12-13 | 2001-06-14 | Exxon Chemical Patents Inc. | Method for utilizing gas reserves with low methane concentrations and high inert gas concentrations for fueling gas turbines |
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| AU2003264182A1 (en) | 2004-04-19 |
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