Patent Application
20150233294
The present invention relates to apparatus (and a corresponding method) for delivering heat to a process, and particularly but not exclusively to a heat engine and a method of operating a heat engine.
Efficient heat engines tend to become bulky for a given power output unless the engine components are made to operate in extreme temperature conditions. Examples of this are large gas turbines which may achieve thermal efficiencies of the order of 60% when coupled with a bottom cycle that recovers some of the energy from the exhaust gas stream. Large diesel engines may achieve efficiencies exceeding 50%. Other types, such as the Stirling engine, appear to offer high efficiency due to the form of the theoretically ideal cycle but are limited in reality by the impossibility of approaching this ideal due to the nature of the real processes within such an engine.
The 1st and 2nd Ericsson cycles offer real engine processes that more closely match the ideal, the 1st cycle being better known as “the Brayton cycle with recuperation”. These cycles are characterised by the implementation of much of the internal engine heat exchange taking place at constant pressure. This allows the heat exchange process to be performed slowly and hence more efficiently than in other cycles. The 2nd Ericsson cycle couples constant pressure recuperation with isothermal expansion and compression, and approaching these conditions within a real engine is exceptionally difficult. However, as the compression and expansion ratios are reduced the 1st and 2nd cycle theoretical efficiencies converge making efforts to achieve isothermal conditions less important.
Reducing compression and expansion ratios has some unfortunate side effects in that, if an engine is naturally aspirated (i.e. minimum cycle pressure is close to one atmosphere), a thermally efficient engine will generally be extremely bulky for a given power output (i.e. have a low power density). Moving parts will be correspondingly large and mechanical efficiency will be poor. A further disadvantage is that pressure losses through internal flow passages and valves will represent a higher proportion of engine internal pressure and will have a correspondingly detrimental effect on efficiency.
The means by which heat is added to, or removed from, an engine cycle are also critical to both power density and efficiency. If heat is added externally as in a Stirling engine or steam plant, then the necessities of heat transfer through a wall result in the thermal cycle being exposed to temperatures limited by the strength of the heat transfer wall. Heat rejection is similarly important and in the case of internal combustion engines is achieved exceptionally effectively via the exhaust stream. Heat addition by internal combustion is also very effective but is limited in most small engine types by the speed of combustion required. This results in incomplete use of the added fuel and also in the generation of undesirable products of combustion.
The present applicant has identified the need for an improved heat engine offering the possibility of increased power density and efficiency over the prior art.
In accordance with a first aspect of the present invention, there is provided a engine comprising: a feeder stage comprising: a first compressor for compressing first gas received at pressure P1 from a gas source to an elevated pressure and temperature; and a reactor (e.g. combustion chamber) for receiving gas compressed by the first compressor and combining the compressed gas with fuel to generate an exothermic reaction (e.g. combustion); and a primary stage comprising: a circuit for recirculating a gas flow comprising a second gas; a mixing chamber in fluid communication with the circuit for combining (e.g. entraining) the products of the exothermic reaction from the feeder stage with the gas flow in the circuit at pressure P2, wherein P2 is greater than P1; an expander for expanding gas received from the mixing chamber to generate mechanical work; and a second compressor for compressing gas expanded by the expander.
In this way, a heat engine in which preheating and pressurisation of an initially low pressure gas in a feeder stage (e.g. feeder cycle) delivers gas (e.g. air or other gas containing non-reacted components for reaction) at an efficient temperature and pressure for the exothermic reaction (e.g. combustion) to take place, whereupon the heated products of the exothermic reaction (e.g. products of combustion) are mixed with a primary cycle gas stream in order to deliver heat direct to the primary cycle. If the feeder cycle is configured as a thermal cycle in its own right and the primary cycle is also a thermal cycle then the part cycle within both cycles in which the mass flow of the mixed streams is the sum of the two cycle mass flows represents a superimposition of the two cycles. This superimposed cycle concept results in very effective heat delivery to the primary cycle, allows the primary cycle to operate at a minimum pressure above that of the feed cycle and also allows the exothermic reaction (e.g. combustion) to take place under near ideal steady state conditions to allow substantially complete use of the fuel.
This principle of the superimposition cycles may be applied to many engine thermal cycles but may be particularly advantageous in the context of the combination of two Brayton (or 1st Ericsson) cycles in which the primary cycle is recuperated. This combination offers real processes that may approach the performance of theoretical processes and hence high efficiency in combination with high power density. In its ideal form it has the same thermal efficiency as a large gas turbine but within a much smaller engine and whilst avoiding the need for engine components operating at the extremes of temperature found within gas turbines. As part of the thermal cycle is shared between the two cycles, the combination results in a new form of cycle which can display characteristics of exceptionally effective addition of heat but with a moderate peak temperature combined with a high power density.
In one embodiment, P2 is at least 5 times greater than P1 (e.g. at least 10 times greater than P1, e.g. at least 20 times greater than P1).
In one embodiment, the reactor is located within the mixing chamber.
In one embodiment, the reactor comprises a vessel defining an opening for venting a continuous flow of the products of the exothermic reaction.
In one embodiment, the reactor is configured (e.g. in at least one mode of operation) to combine gas and fuel continuously (e.g. to achieve a continuous exothermic reaction (e.g. continuous combustion)).
In one embodiment, the reactor is configured to combine gas and fuel in a substantially stoichiometric or near-stoichiometric ratio.
In one embodiment, the first gas is air (e.g. atmospheric air).
In one embodiment, the first compressor is configured to raise the temperature of the first gas to above a self-ignition temperature of the fuel.
In one embodiment, the primary stage comprises a recuperator for transferring heat from gas expanded by the expander to gas compressed by the second compressor.
In one embodiment, the primary stage comprises a heat exchanger for transferring heat from gas expanded by the expander to a heat sink (e.g. ambient or a colder heat sink if available). In the case of a primary stage comprising a recuperator, the heat exchanger may be located between the recuperator and the second compressor to transfer heat from gas cooled by the recuperator prior to compression of the gas by the second compressor.
In one embodiment, the heat engine further comprises means (e.g. an outlet) for removing gas from the circuit. In this way, the gas content in the gas circuit may be controlled to take account of gas added to the primary flow in the mixing chamber (e.g. to maintain a substantially constant mass in the primary cycle for a given pressure and temperature ratio). In one embodiment, the removed gas may be vented to atmosphere.
In one embodiment, the means for removing gas is located between the mixing chamber and the expander. In another embodiment the means for removing gas is located after the expander (e.g. between the expander and the recuperator).
In one embodiment, the means for removing gas from the circuit comprises a further expander for expanding the removed gas.
In one embodiment, the flow of gas through the primary stage has a mass flow rate greater than the flow of gas through the feeder stage (e.g. at least 5 times greater, at least 10 times greater, at least 20 times greater).
In one embodiment, the expander has an expansion ratio that this less than the reciprocal of the compression ratio of the first compressor.
In the case that the further expander is located between the mixing chamber and the expander, the expander may have an expansion ratio that is less than the expansion ratio of the further expander.
In one embodiment, the expander has an expansion ratio of less than 5 (e.g. less than 4 or less than 2).
In one embodiment, the primary stage has a minimum gas pressure Pmin that is greater than P1.
In one embodiment, the expander and/or further expander are coupled (e.g. directly mechanically coupled (e.g. by means of a connecting shaft) or indirectly coupled (e.g. via a generator driving an electrically driven compressor) to at least one of the first and second compressors whereby the work of expansion is used to assist the work of compression.
The first and/or second compressor may be a rotary compressor, reciprocating compressor or any other form of compressor.
In one embodiment, the compression by the first and/or second compressors is substantially isentropic or adiabatic.
In one embodiment, the exothermic reaction occurs under substantially isobaric conditions.
The expander and/or further expander may be a rotary expander, reciprocating expander or any other form of expander.
In one embodiment, the expansion by the expander and/or further expander is substantially isentropic or adiabatic.
In one embodiment, the second compressor is a positive displacement compressor and the expander is a dynamic expander (e.g. turbo-expander). In this way, operation of the second compressor and the expander may be optimised for apparatus in which volumetric gas flow through the second compressor is lower (e.g. significantly lower) than volumetric gas flow through the expander.
In accordance with a second aspect of the present invention, there is provided a method of operating a heat engine, comprising: in a feeder stage: using a first compressor to compress a first gas received at pressure P1 from a gas source to an elevated pressure and temperature; transferring the compressed gas to a reactor (e.g. combustion chamber) and combining the compressed gas with fuel to generate an exothermic reaction (e.g. combustion); and in a primary stage: recirculating a gas flow comprising a second gas around a circuit; in a mixing chamber in fluid communication with the circuit combining (e.g. entraining) the products of the exothermic reaction from the feeder stage with the gas flow in the circuit at pressure P2, wherein P2 is greater than P1; using an expander to expand gas received from the mixing chamber to generate mechanical work; and using a second compressor to compress gas expanded by the expander for recirculation to the mixing chamber.
In one embodiment, P2 is at least 5 times greater than P1 (e.g. at least 10 times greater than P1, e.g. at least 20 times greater than P1).
In one embodiment, the reactor is located within the mixing chamber.
In one embodiment, the reactor comprises a vessel defining an opening for venting a continuous flow of the products of the exothermic reaction.
In one embodiment, compressed gas and fuel are combined continuously (e.g. to achieve a continuous exothermic reaction (e.g. continuous combustion)).
In one embodiment, compressed gas and fuel are combined in a substantially stoichiometric or near-stoichiometric ratio.
In one embodiment, the first gas is air (e.g. atmospheric air).
In one embodiment, the step of compressing the first gas using the first compressor comprises raising the temperature of the first gas to above a self-ignition temperature of the fuel.
In one embodiment, the method further comprises passing gas expanded by the expander through a recuperator to transfer heat from the expanded gas to gas compressed by the second compressor.
In one embodiment, the method further comprises transferring heat from gas expanded by the expander to a heat sink (e.g. ambient or a colder heat sink if available). In the case of a primary stage comprising a recuperator, the heat exchanger may be located between the recuperator and the second compressor to transfer heat from gas cooled by the recuperator prior to compression of the gas by the second compressor.
In one embodiment, the method further comprises removing gas from the circuit. In this way, the gas content in the gas circuit may be controlled to take account of gas added to the primary flow in the mixing chamber (e.g. to maintain a substantially constant mass in the primary cycle for a given pressure and temperature ratio). In one embodiment, the removed gas may be vented to atmosphere.
In one embodiment, gas is removed from the circuit after combining the products of the exothermic reaction from the feeder stage with the gas flow and before the gas expansion step. In another embodiment, gas is removed after passing through the expander (e.g. between the expander and the recuperator).
In one embodiment, gas removed from the circuit is expanded by a further expander.
In one embodiment, the flow of gas through the primary stage has a mass flow rate greater than the flow of gas through the feeder stage (e.g. at least 5 times greater, at least 10 times greater, at least 20 times greater).
In one embodiment, the expander has an expansion ratio that this less than the reciprocal of the compression ratio of the first compressor.
In the case that gas is removed from the circuit before the gas expansion step, the expander may have an expansion ratio that is less than the expansion ratio of the further expander.
In one embodiment, the expander has an expansion ratio of less than 5 (e.g. less than 2).
In one embodiment, the primary stage has a minimum gas pressure Pmin that is greater than P1.
In one embodiment, the expander and/or further expander are coupled (e.g. directly mechanically coupled (e.g. by means of a connecting shaft) or indirectly coupled (e.g. via a generator driving an electrically driven compressor) to at least one of the first and second compressors whereby the work of expansion is used to assist the work of compression.
The first and/or second compressor may be a rotary compressor, reciprocating compressor or any other form of compressor.
In one embodiment, the compression by the first and/or second compressors is substantially isentropic or adiabatic.
In one embodiment, the exothermic reaction occurs under substantially isobaric conditions.
The expander and/or further expander may be a rotary expander, reciprocating expander or any other form of expander.
In one embodiment, the expansion by the expander and/or further expander is substantially isentropic or adiabatic.
In accordance with a third aspect of the present invention, there is provided apparatus for delivering heat to a process, comprising: a feeder stage comprising: a compressor for compressing a first gas received at pressure P1 from a gas source to an elevated temperature and pressure; and a reactor (e.g. combustion chamber) for receiving gas compressed by the first compressor and combining the compressed gas with fuel to generate an exothermic reaction (e.g. combustion); and a primary stage comprising: a mixing chamber for combining (e.g. entraining) the products of the exothermic reaction from the feeder stage with a fluid flow (e.g. gas flow) at pressure P2, wherein P2 is greater than P1.
In this way, apparatus for efficiently delivering heat to a process is provided in which preheating and pressurisation of an initially low pressure gas in a feeder stage (e.g. feeder cycle) delivers gas (e.g. air or other gas containing non-reacted components for reaction) at an efficient temperature and pressure for the exothermic reaction (e.g. combustion) to take place, whereupon the heated products of the exothermic reaction (e.g. products of combustion) are mixed with fluid stream intended for a process in order to deliver heat direct to the fluid stream. The apparatus may be used for delivering heat to any process in which a high temperature fluid steam (e.g. gas stream) is required or may be utilised. For example, the process may be selected from the non-exhaustive list of: a molten metal process at elevated pressure (e.g. to ensure densification on solidification); chemical process that benefit from elevated pressures; surfaces treatments.
In one embodiment, P2 is at least 5 times greater than P1 (e.g. at least 10 times greater than P1, e.g. at least 20 times greater than P1).
In one embodiment, the reactor is located within the mixing chamber.
In one embodiment, the reactor comprises a vessel defining an opening for venting a continuous flow of the products of the exothermic reaction.
In one embodiment, the reactor is configured to combine gas and fuel continuously (e.g. to achieve a continuous exothermic reaction (e.g. continuous combustion)).
In one embodiment, the reactor is configured to combine gas and fuel in a substantially stoichiometric or near-stoichiometric ratio.
In one embodiment, the first gas is air (e.g. atmospheric air).
In one embodiment, the compressor is configured to raise the temperature of the first gas to above a self-ignition temperature of the fuel.
In one embodiment, the fluid flow has a mass flow rate greater than the flow of gas through the feeder stage (e.g. at least 5 times greater, at least 10 times greater, at least 20 times greater).
The compressor may be a rotary compressor, reciprocating compressor or any other form of compressor.
In one embodiment, the compression by the compressor is substantially isentropic or adiabatic.
In one embodiment, the exothermic reaction occurs under substantially isobaric conditions.
A method of delivering heat to a process, comprising: in a feeder stage: using a compressor to compress a first gas received at pressure P1 from a gas source to an elevated temperature and pressure; transferring the compressed gas to a reactor (e.g. combustion chamber) and combining the compressed gas with fuel to generate an exothermic reaction (e.g. combustion); and in a primary stage: in a mixing chamber combining (e.g. entraining) the products of the exothermic reaction from the feeder stage with a fluid flow (e.g. gas flow) at pressure P2, wherein P2 is greater than P1.
In one embodiment, P2 is at least 5 times greater than P1 (e.g. at least 10 times greater than P1, e.g. at least 20 times greater than P1).
In one embodiment, the reactor is located within the mixing chamber.
In one embodiment, the reactor comprises a vessel defining an opening for venting a continuous flow of the products of the exothermic reaction.
In one embodiment, compressed gas and fuel are combined continuously (e.g. to achieve a continuous exothermic reaction (e.g. continuous combustion)).
In one embodiment, compressed gas and fuel are combined in a substantially stoichiometric or near-stoichiometric ratio.
In one embodiment, the first gas is air (e.g. atmospheric air).
In one embodiment, the step of compressing the first gas using the compressor comprises raising the temperature of the first gas to above a self-ignition temperature of the fuel.
In one embodiment, the fluid flow has a mass flow rate greater than the flow of gas through the feeder stage (e.g. at least 5 times greater, at least 10 times greater, at least 20 times greater).
The compressor may be a rotary compressor, reciprocating compressor or any other form of compressor.
In one embodiment, the compression by the compressor is substantially isentropic or adiabatic.
In one embodiment, the exothermic reaction occurs under substantially isobaric conditions.
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
Feed stage 20 comprises: a gas inlet 22 for receiving the first gas (e.g. air or other gaseous reactant) from a first gas source at pressure P1; a small compressor 24 (e.g. rotary or reciprocating or other form) configured to compress gas received from gas inlet 22 to a peak pressure; and a reactor 28 (e.g. combustion chamber or combustor) contained within a larger mixing chamber 44 forming part of primary stage 40.
Reactor 28 comprises a vessel 30 defining an opening 32 for venting a continuous flow of the products of reaction (e.g. products of combustion) and is configured to receive gas compressed by small compressor 24 via path 26 at elevated pressure and temperature together with fuel 33 supplied by means of fuel inlet 34 and combine the compressed gas and fuel to generate at region 35 a continuous exothermic reaction (e.g. combustion in the case that the gas includes an oxidant). The heated products of the exothermic reaction are then directed into mixing region 45 in mixing chamber 44 for entrainment in a gas flow through circuit 42 at pressure P2 in order to add heat direct to the primary cycle gas reducing its density and increasing its temperature. The reactant mixture fed to reactor 28 is selected to result in an exothermic reaction at a higher temperature than the temperature at which the primary cycle gas enters mixing chamber 44 and may be in a ratio such as to allow very high temperature combustion (e.g. substantially stoichiometric, near-stoichiometric or another ratio). The temperature of the resulting mixture is thus above that of the primary cycle gas as it enters mixing chamber 44 but below that of the products of reaction of the reactants supplied to reactor 28. Some of the mixture within the mixing chamber is diverted via path 36 to a small expander 38 (either reciprocating, rotary or some other form) where the gas is expanded to the original pressure of the inlet stream P1 where it is exhausted at outlet 39 to the environment (e.g. in the case that the first gas is air) or other waste receiver. The remainder of the gas mixture within the mixing chamber 44 passes via path 46 to a large expander 48 (either reciprocating, rotary or some other form) within which the gas is expanded to a pressure above that of the inlet stream P1 such that the expansion ratio of small compressor 24 and small expander 34 of the feed cycle is greater than that of the ratio within the large expander 48, typical ratios for an air-breathing machine being greater than 15 and less than 2 respectively although other ratio ranges are possible.
After leaving the large expander 48, the gas is passed via path 50 to a recuperator 52 where it is cooled in by a warming stream and then passes to a cooler 54 which further cools the gas to a temperature as close as is practicable to the environment temperature, or cooler if a colder heat sink is available. The gas leaves cooler 54 and passes via path 56 to a large compressor 58 which re-compresses the gas to approximately the pressure P2 of the mixing chamber 44. The gas leaves the large compressor 58 via path 60 and enters recuperator 52 in which it is warmed by the opposed cooling flow to an approximately similar temperature as the reactant gas feed to reactor 28. The gas is then passed via path 62 to mixing chamber 44 and mixes with the products of reaction downstream of reactor 28 and continues downstream of mixing chamber 44 as previously described in a continuous cycle.
The mass flow within the primary cycle therefore substantially recirculates and is everywhere above the pressure P1 of the feeder cycle inlet flow. The primary cycle mass flow is also typically much greater than that of the feed cycle. As illustrated, compressors 24, 58 and expanders 38, 48 are mechanically linked by a shaft 64 (although other methods are possible) and since the work of the two expanders is greater than that of the two compressors, the whole represents a power producing engine cycle.
While this cycle offers an extremely effective way of adding heat to a pressurised engine cycle (the primary cycle), the products of combustion within reactor 28 are likely to contain some elements that are subject to phase change on cooling and so liquid waste may be generated at some point within the cycle. This may be removed by placing a collector (not shown) on the gas path downstream of the cold side of recuperator 52 or cooler 54 from which this residue may be scavenged, either under engine pressure or via a pump (again not shown).
The working fluid of the primary cycle will ultimately be products of combustion if a gas cycle is used. A vapour cycle is also possible in which the vapour condenses to liquid in recuperator 52 and/or the cooler 54 allowing any gas and excess liquid content to be scavenged via a release valve (not shown). Re-vapourisation would then take place in recuperator 52 and heat would be supplied by mixing with products of combustion within mixing chamber 44 as before. The inlet side of the feed cycle would process only reactants for combustion (being natural air for example) although small expander 38 (notionally the expansion side of the feed cycle) would expand the same working fluid as the primary cycle.
Although there are some superficial similarities of this illustrated cycle with a supercharged engine there are some important differences:
1. The primary cycle recycles most of the working fluid
2. The combustion process only uses gas and fuel fed to the feed cycle
3. Heat addition to the primary cycle is primarily through mixing with the products of reaction of the feed cycle
4. The primary cycle is everywhere above the lowest pressure of the feed cycle
5. The primary cycle mass flow is greater than that of the feed cycle (often 10 to 20 or more times greater)
6. Any unburnt reactants that remain within the primary cycle will return to the combustion chamber as the cycle repeats and, if a small surplus of oxygen (for example) is supplied by the feed cycle, as combustion temperatures are achieved these unburnt reactants will have further opportunities to react and generate heat.
Advantageously, the heat engine 10 of the present invention offers the potential for a device that is extremely compact for a given power output, whose moving components and valves are not required to operate at extreme temperatures, and that can be efficient in small (e.g. around 100 kW) sizes. Furthermore, given that the superimposed cycle engine performs the bulk of its work in a pressurised state, heat engine 10 will be particularly suitable for aviation applications as it can be made insensitive to the effects of high altitude operation. As it offers a similar efficiency to a large gas turbine but within the envelope of a small reciprocating machine it can have applicability to lower power uses such as light aircraft, small generators and vehicles. The continuous combustion in the preferred implementation also allows the use of many different fuels including gaseous, liquid and solid forms. Its high efficiency in small scale may also be of use in distributed power generation and combined heat and power systems.
Although described in terms of simple compressors and expanders, the devices used in heat engines 10 and 10′ may be of either positive displacement or aerodynamic (turbo-machine) form or any appropriate combination of these as demanded by the specific application. Furthermore, all heat exchange processes occur at approximately constant pressure and so the processes may take place slowly in large heat exchange devices. This will result in low pressure losses and efficient heat exchange.
In one embodiment, heat engines 10 and 10′ may be configured such that volumetric gas flow through large compressor 58, 58′ is significantly lower than volumetric gas flow through large expander 48, 48′ (e.g. as illustrated in
The plotting of primary and feed cycles on pressure-specific volume coordinates shows an area per unit mass of working fluid (and hence work) of the primary cycle that is similar to that of the feed cycle, however, the mass of working fluid in this cycle is much greater than that of the feed cycle and the actual work of the idealised primary plus feed cycles (the superimposed cycle) depicted here is identical to that of the “equivalent Brayton cycle” depicted by points 1e, 2e, 3e, 4e, le. This equivalent cycle is the cycle that would result if the feed cycle flow was not mixed with another flow between points 2, 2e and 3, 3p, i.e., it is a Brayton cycle with a mass flow equal to that of the feed cycle and with a peak temperature equal to the post exothermic reaction temperature (e.g. post combustion temperature). As this point the exothermic reaction temperature (e.g. combustion temperature) may be of the order of 2300K, however, as it has the same heat input as the superimposed cycle and the same work output it is therefore apparent that the thermal efficiency of this cycle is identical to that of the superimposed cycle. The peak temperature of the superimposed cycle is, however very much lower than that of the equivalent Brayton cycle and so this is a practical cycle that may be closely approximated by a physical engine.
The analysis upon which
Feed stage 120 comprises: a gas inlet 122 for receiving the first gas (e.g. air or other gaseous reactant) from a first gas source at pressure P1; a small compressor 124 (e.g. rotary or reciprocating or other form) configured to compress gas received from gas inlet 122 to a peak pressure; and a reactor 128 (e.g. combustion chamber or combustor) contained within a larger mixing chamber 144 forming part of primary stage 140.
Reactor 128 comprises a vessel 130 defining an opening 132 for venting a continuous flow of the products of reaction (e.g. products of combustion) and is configured to receive gas compressed by small compressor 124 via path 126 at elevated pressure and temperature together with fuel 133 supplied by means of fuel inlet 134 and combine the compressed gas and fuel at region 135 to generate a continuous exothermic reaction (e.g. combustion in the case that the gas includes an oxidant). The heated products of the exothermic reaction are then directed into mixing chamber 144 for entrainment in a fluid flow through primary stage 140 at pressure P2 in order to add heat direct to the primary cycle gas reducing its density and increasing its temperature. The reactant mixture fed to reactor 128 is selected to result in an exothermic reaction at a higher temperature than the temperature at which the primary stage fluid flow enters mixing chamber 144 and may be in a ratio such as to allow very high temperature combustion (e.g. substantially stoichiometric, near-stoichiometric or another ratio). The temperature of the resulting mixture is thus above that of the primary cycle fluid as it enters mixing chamber 144 but below that of the products of reaction of the reactants supplied to reactor 128.
Apparatus 100 may be used for delivering heat to any process in which a high temperature fluid steam (e.g. gas stream) is required or may be utilised.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1218611.0 | Oct 2012 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2013/052711 | 10/17/2013 | WO | 00 |
