Flame control in oxyfuel combustion process

Abstract

To improve flame propagation in a combustor, particularly in a combustor for use in a power production system and method.SOLUTION: At least one stream being fed into the combustor (e.g., a fuel, an oxidant, a diluent, a coolant, a working fluid, water, or steam) may be independently heated to a temperature that is about the autoignition temperature of the fuel or higher. Further, flame stabilization, including promoting ignition, may be improved through controlled addition of one or more NOx species into the combustor or combustion chamber.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to flame control in an oxy-fuel combustion process. More specifically, the present disclosure provides systems and methods for oxy-fuel combustion for power generation.

Background Art

[0002] In an oxy-fuel combustion cycle, it is desirable to promote and maintain ignition before the temperature and pressure of the entire system rise to a point where the flame in the combustor can be easily maintained. Thus, until the combustor reaches at least the required temperature, the flame can be extremely unstable. Further, once ignition is achieved, the flame must maintain an ignited state through the transient state of the system, which can involve an extended operating time at low temperatures. At these low temperatures, it can be difficult to maintain the flame without blowout.

[0003] A variety of methods have been considered for ignition in combustors. Spark igniters have been used in gas turbines, but the spark igniters themselves are considered to be prone to failure at high pressures, so there are problems with the compatibility of such elements in high-pressure oxy-fuel systems, and the release of components into the power generation cycle can cause damage to the power generation cycle. It is also known to use spark igniters only during the initial start-up phase of conventional gas turbines so that the igniter can be withdrawn from the combustor after ignition. On the other hand, in some aircraft combustors, continuous igniter operation is known to be used to reduce the risk of blowout or to increase the likelihood of re-ignition if blowout occurs. However, implementing such a solution using a high-pressure oxy-fuel combustion system increases complexity, so the solution is not practical. Laser ignition systems have become popular in known combustion systems in recent years, but there are potential problems with the placement of the device and the power that must be supplied to the laser to initiate ignition. In addition, the laser requires an optical path to the center of the combustion chamber, which can introduce complexity and potential points of failure by using options such as sapphire windows. Furthermore, self-igniting chemicals are used when testing rocket motors and add energy during ignition, but the products of the chemical reaction are solids, and their use in a closed power cycle where the solids can clog the combustor itself, the turbine, and / or the heat exchanger is not permitted. In systems that utilize air as an oxidizer in combustion turbines, it has been recognized that the presence of NOx species can be useful in promoting the combustion process. However, due to regulations regarding NOx emissions, the intentional addition of NOx species to the combustion process for discharge to the atmosphere is still not preferred.

[0004] These known potential ignition sources only correspond to points within the space in the combustor where ignition occurs and not to the overall flow parameters entering the combustor, so they are insufficient for use in many cases related to the current problem. Improving or adjusting the bulk flow rate entering the combustor as well as all other factors related to the start-up of the system can have a positive impact on multiple processes including combustion. For example, in many cases, it is desirable to raise the processes and temperatures of the rest of the plant at a fairly slow rate (much slower than the temperature changes seen at ignition) while maintaining the flame. In such cases, a more robust and comprehensive solution is required in addition to simply generating an ignition spark.

[0005] In addition to the foregoing considerations, adding additional catalysts to ensure the continuous progress of the reaction and to lower the energy hurdle for initiating the reaction is very common in chemical reactions. This can be achieved further by adding a solid catalyst or promoter to the reaction zone or by supplying an additional flow of catalyst or promoter that freely flows through the process stream in a continuous process. For this reason, as described above, it is already known that the addition of NOx can promote combustion in the flame using air as an oxidant, but regulations regarding NOx emissions and important requirements for preventing such emissions have made the addition of NOx an impractical solution. Therefore, in the art, there is still a need to improve combustion processes and systems that facilitate the start-up and / or maintenance of oxy-fuel combustion processes. SUMMARY OF THE INVENTION

[0006] The present disclosure provides systems and methods suitable for improving the start-up and continuous operation of power plants. The systems and methods of the present disclosure can be implemented in various power generation cycles and can be particularly beneficial for use with oxy-fuel combustion cycles intended for high-pressure operation.

[0007] In one or more embodiments, the present disclosure may provide a method for propagating a flame within a combustor of a power generation plant. Propagating flame or flame propagation, as used herein, is for improving the ability to initially ignite a flame, such as at startup of a power generation plant, for improving the ability to re-ignite a flame after blowout, and / or for maintaining a flame during operation when the combustor temperature is below normal operating conditions and / or the output of the power generation plant is below normal operation (e.g., during a transient period) to avoid blowout. The operating period below normal operating parameters can be defined as operating at a combustor temperature that is less than 90%, less than 80%, less than 75%, less than 60%, or less than 50% of the typical temperature at which the power generation plant operates at normal output. Similarly, the transient period can be defined as operating the power generation plant at an output that is less than 90%, less than 80%, less than 75%, less than 60%, or less than 50% of the output from the power generation plant when operating under normal conditions. Under such conditions, the flame within the combustor can be prone to blowout, and flame ignition can be more difficult under such conditions. Thus, the present disclosure provides methods and systems for improving flame propagation, as is apparent from the ease of flame ignition or re-ignition and / or from the improvement in blowout resistance.

[0008] In some embodiments, the method of the present disclosure includes introducing a fuel having a defined auto-ignition temperature into the combustor, further introducing at least one non-fuel stream into the combustor, and sufficiently heating the at least one non-fuel stream such that the total flow of the streams entering the combustor is at a temperature higher than the auto-ignition temperature of the fuel or at a temperature that is no more than 20% lower than the auto-ignition temperature of the fuel, and heating the at least one non-fuel stream is performed using heat generated from combustion. In one or more embodiments, the method can be further defined with respect to one or more of the following descriptions that can be combined in any number and order.

[0009] The method can be implemented at startup of the power generation plant or during a transient period of operation of the power generation plant.

[0010] The start-up of a power plant or the transient period of operation of a power plant may be defined in relation to the power plant operating at an output of less than 75% of its normal operating output.

[0011] The non-fuel stream(s) can be one or more of an oxidant stream, a working fluid stream, a dilution stream, and a water / steam stream.

[0012] Heating at least one non-fuel stream can include using one or more line heaters to heat at least a portion of the line through which the non-fuel stream flows to the combustor.

[0013] One or more line heaters can be configured to receive a heating stream and transfer heat therefrom to the line.

[0014] Heating at least one non-fuel stream can include directly heating at least one non-fuel stream.

[0015] Directly heating at least one non-fuel stream can include compressing at least one non-fuel stream.

[0016] Heating at least one non-fuel stream can include passing at least one non-fuel stream through a heat exchanger to contact another heating stream.

[0017] At least one non-fuel stream can be introduced into the combustor through a line that includes a branch line separable from the line.

[0018] Heating at least one non-fuel stream can include heating at least a portion of the branch line.

[0019] The branch line can be separable from the line using one or more valves that selectively enable or disable the flow of at least one non-fuel stream through the branch line.

[0020] The method may further include controllably operating a heating member present in the combustor or its combustion chamber.

[0021] The heating member may be controlled such that it is effective to add sufficient heat to raise the overall temperature in the combustor or combustion chamber above the auto - ignition temperature of the fuel when the total flow of the flow entering the combustor is at a temperature lower than the auto - ignition temperature of the fuel.

[0022] The method may further include introducing into the combustor a chemical catalyst comprising at least one NOx species in an amount sufficient to reduce the activation energy level required to achieve or maintain a flame in the combustor or its combustion chamber.

[0023] In one or more embodiments, the present disclosure may provide a power generation plant. Such a plant may be configured to improve the control of flame propagation as described elsewhere herein. For example, the power generation plant may include a combustor, a fuel line configured to introduce a fuel having a defined auto - ignition temperature into the combustor, at least one inlet line configured to deliver at least one non - fuel flow to the combustor, a turbine in fluid communication with the combustor, and at least one heater operably arranged with the at least one inlet line to sufficiently heat the at least one non - fuel flow such that the total flow of the flow entering the combustor is at a temperature above the auto - ignition temperature of the fuel or at a temperature that is at most 20% lower than the auto - ignition temperature of the fuel. In further embodiments, the power generation plant can be defined in relation to one or more of the following descriptions that can be combined in any number and order.

[0024] The combustor may further include a heating member positioned in the combustor or its combustion chamber.

[0025] The heating member can be configured to heat the combustor or combustion chamber separately from heating from the total flow of the flow entering the combustor.

[0026] The heating member can be a resistance heater.

[0027] The heating member can be controllable such that it is effective to add sufficient heat so that when the total flow of the flow entering the combustor is at a temperature lower than the auto-ignition temperature of the fuel, the overall temperature in the combustor becomes higher than the auto-ignition temperature of the fuel.

[0028] At least one heater can be a line heater.

[0029] The line heater can be configured to receive a heating flow and transfer heat from it to the line.

[0030] At least one heater can include a compressor.

[0031] At least one heater can include a heat exchanger in which at least one non-fuel flow can be heated by contacting the heating flow.

[0032] At least one input line can further include a branch line separable from the at least one input line, and at least one heater is positioned on the branch line.

[0033] The branch line can be separable from the at least one input line using one or more valves that selectively enable or disable the flow of at least one non-fuel flow through the branch line.

[0034] In one or more embodiments, a method for propagating a flame in a combustor of a power generation plant can include introducing fuel into the combustor, introducing an oxidizer into the combustor, and introducing into the combustor a chemical catalyst containing at least one NOx species in an amount sufficient to reduce the activation energy level necessary to achieve or maintain a flame in the combustor or in its combustion chamber. In further embodiments, the method can be further defined with respect to one or more of the following disclosures that can be combined in any number and order.

[0035] A chemical catalyst containing at least one NOx species can be introduced into a combustor in combination with one or both of a fuel and an oxidant.

[0036] The method may further include reacting at least ammonia in a reactor to produce at least one NOx species.

[0037] Introducing a chemical catalyst containing at least one NOx species can be substantially continuous during operation of a power plant, and the method may further include adjusting the content of the chemical catalyst containing at least one NOx species based on changes in one or more further operating parameters of the power plant.

[0038] Introducing a chemical catalyst containing at least one NOx species can be done until a specified threshold value is reached.

[0039] The specified threshold value can be the combustor operating temperature or the output of the power plant.

[0040] A chemical catalyst containing at least one NOx species can be introduced in a sufficient amount such that the amount of at least one NOx species present in the exhaust flow exiting the combustor is from about 5 ppm to about 1000 ppm.

[0041] A power plant according to the present disclosure may include a combustor, a turbine or expander in fluid communication with the combustor and arranged to receive exhaust from the combustor, and a plurality of lines configured to introduce at least fuel, an oxidant, and a chemical catalyst containing at least one NOx species into the combustor. In a further embodiment, the power plant may further include a reactor configured to receive at least ammonia and discharge a stream containing at least one NOx species.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0043] Exemplary embodiments of the subject matter of the present disclosure will be described in more detail hereinafter. These exemplary embodiments are described so that the present disclosure will be thorough and complete, and to fully convey the scope of the subject matter of the present disclosure to those skilled in the art. In fact, the subject matter of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are presented so as to meet applicable legal requirements. As used herein and in the appended claims, the singular forms ( "a", "an", "the") include plural referents unless the context clearly dictates otherwise.

[0044] In one or more embodiments, the present disclosure relates to systems and methods for improving the operation of at least a combustor configured to operate in a power generation system. Such a system may be particularly configured to execute an oxy-fuel combustion cycle, and the systems and methods of the present disclosure may be particularly useful for improving the operation of a system for power generation. By way of non-limiting example, the present disclosure may be effective in promoting one or more of ignition, combustion, and flame stability within a combustor, particularly within the combustor of the power generation system. Additionally, the present disclosure may be effective in maintaining an appropriate bulk temperature in various regions of the facility at moments before and after ignition of the combustor. In some embodiments, the improvements described herein may be particularly realized when the power generation system, particularly the combustor, is operating at startup and / or at any time when the combustor is operating at a temperature below its normal operating temperature.

[0045] As used herein, the normal operating temperature means, in particular, the temperature (±10%) at which the combustor is typically operated when the power generation is operating at full power generation. For example, an oxy-fuel combustion process such as that described in U.S. Patent No. 8,596,075, the disclosure of which is incorporated herein by reference, may have a normal operating temperature of about 800°C. Thus, the normal operating temperature can be in the range of about 600°C to about 1000°C, or about 600°C to about 900°C, depending on the particular configuration of the power generation system, although such temperature ranges are not intended to limit the ability to implement the various embodiments disclosed herein. Further, the exact temperature selected will be a function of the expected auto-ignition temperature range of the fuel, as well as the desired inlet conditions for downstream conditions. However, it is important to recognize that the normal operating temperature is not immediately achieved at startup of the power generation plant. Rather, the temperature of the operating power generation cycle must be raised from ambient temperature to the normal operating temperature. Similarly, in some cases, it may be desirable to significantly lower the cycle temperature below the normal operating temperature in order to perform maintenance or for other reasons without completely stopping the cycle. The period during which such an operating temperature is lowered may be referred to as a transient period.

[0046] As described above, it can be difficult to achieve a stable flame in the combustor, more specifically in the combustion chamber, at startup. Also, when the cycle temperature is lowered during a transient period, the flame may become unstable again. The present disclosure improves the ability to achieve startup of the combustor and / or improves the ability to maintain a stable combustor flame during periods when the operating temperature is lowered by implementing one or more features further described herein. Thus, the present disclosure relates specifically to propagating a flame within a combustor of a power generation plant at startup or when the power generation plant is operating below normal operating conditions (e.g., combustor temperature and / or plant output).

[0047] As already mentioned, the present disclosure provides improvements that can be implemented using existing power generation systems and methods, or future systems and methods, that utilize a combustor, combustion chamber, or similar element where fuel is burned with an oxidizer to form an exhaust stream. The present disclosure can complement such configurations by adding one or more additional members and / or by adding one or more inputs to the combustion members. If the present disclosure is implemented in an existing power cycle, other members of the power cycle can be used substantially unchanged.

[0048] An exemplary power plant 100 suitable for implementing the power generation process according to the present disclosure is shown in FIG. 1. As shown in FIG. 1, the combustor 120 is configured to receive fuel through line 109, an oxidizer through line 103, and a diluent through line 184. The oxidizer can be an air stream and / or substantially pure oxygen that can be formed (e.g., using an air separation unit 102 suitable for forming oxygen from the air stream 101). The air separation unit 102 can include a compressor necessary to supply the oxidizer at a desired pressure, or a separate compressor can be provided in series between the air separation unit 102 and the combustor 120. Similarly, optionally, any compressor connected to the fuel line 109 can be present to compress the fuel to a desired pressure before it enters the combustor 120. The diluent can be any suitable material such as water (e.g., steam), carbon dioxide, etc. As shown, the recirculated carbon dioxide stream is sent through line 184 to the combustor 120 and serves as the diluent stream. In some embodiments, a portion of the recirculated carbon dioxide stream from line 184 can be withdrawn and mixed with the oxidizer stream in line 103 to form a diluted oxidizer stream having a desired O2 / CO2 ratio.

[0049] The fuel is burned with oxygen in combustor 120 to form a combustor exhaust stream 130, which passes through turbine 135 or other expander where it expands to generate power in generator 136. The turbine exhaust stream 137 passes through heat exchanger 140 where it is cooled to form stream 142, which is further cooled in cooler 144 to near ambient temperature. The cooled turbine exhaust stream 146 is then processed in water separator 150 to produce a water stream 152 (which may contain some content of nitric acid and / or sulfuric acid if SOx species and / or NOx species are present in the exhaust stream 130 from the fuel or any additives that may be added to combustor 120). A substantially pure carbon dioxide stream 155 exits separator 150 and is compressed in compressor 160 to form an intermediate compressed stream 165. The intermediate compressed stream 165 is cooled in cooler 170 to increase the density of the carbon dioxide, forming a carbon dioxide stream 171 with increased density, and the carbon dioxide stream 171 is pressurized to a high pressure in pump 175 for introduction into combustor 120. A carbon dioxide product stream 180 is withdrawn from the high-pressure carbon dioxide stream 177, leaving a carbon dioxide recycle stream 182, which can be returned to heat exchanger 140 to contact the turbine exhaust stream 137 and be heated. The heated recycled carbon dioxide stream 184 is then returned to combustor 120 for use as a diluent. The control unit 190 may be included with the power generation plant 100 and may be configured to receive one or more inputs 192 and provide one or more outputs 191 that may be effective for automatic control of one or more functions of the power generation plant.

[0050] During normal operation, combustor 120 can be operated at a fairly high temperature so that flame stability is maintained and it does not constantly encounter problems such as blowout. However, during startup or transient periods, it can be difficult to achieve and / or maintain ignition and / or flame ignition.

[0051] In one or more embodiments, such problem(s) can be addressed by including one or more line heaters having an appropriate size and heat generating capacity at one or more locations within the power generation plant. During operation, the heater(s) can be used to raise the temperature of the flow(s) within one or more lines to a temperature above the autoignition temperature of the fuel being burned within the combustor so that no separate ignition source is required. For example, the autoignition temperature of substantially pure methane is about 600°C, and such temperature can be achieved by a variety of heating techniques including reheat heating, combustion heating, mechanical heating (e.g., compression heat), etc. Thus, the fuel will spontaneously ignite within the combustor or combustion chamber when an appropriate temperature is achieved in the presence of an oxidizer. Maintaining a temperature above the autoignition temperature of the fuel results in flame stability that would otherwise have to be achieved aerodynamically, which is not possible if the cycle pressure and temperature are too low. Thus, heating can be performed to achieve a target temperature within the combustor and / or combustion chamber. Such target temperature is typically higher than the autoignition temperature of the fuel being burned and can be, for example, at least 2%, at least 5%, at least 10%, at least 20%, or at least 25% higher than the autoignition temperature of the fuel. Although not essential, the heating can be limited so that the target temperature does not exceed 100% higher than the autoignition temperature of the fuel. For example, the target temperature can be about 2% to about 75%, about 3% to about 60%, about 4% to about 50%, or about 5% to about 25% higher than the autoignition temperature of the fuel. In some embodiments, such target temperature may refer to the temperature within the combustor or combustion chamber. In other embodiments, such target temperature may refer to the temperature of the flow being sent to the combustor through the inlet line (e.g., the flow temperature is measured just upstream of the combustor).

[0052] In some embodiments, the heating can be performed on at least one non-fuel stream such that the total flow of the stream flowing into the combustor is at a temperature that is higher than the auto-ignition temperature of the fuel or at most 20% lower than the auto-ignition temperature of the fuel. When the temperature of the total flow of the stream flowing into the combustor is higher than the auto-ignition temperature of the fuel, the flame can propagate more easily and blowout can be avoided. In some embodiments, although it is possible to operate in accordance with the present disclosure, when the temperature of the total flow of the stream flowing into the combustor is less than the auto-ignition temperature of the fuel, additional operations are similarly performed to otherwise increase the activation energy in the combustor or combustion chamber. For example, as further described herein, a chemical catalyst can be introduced into the combustor and / or a heating member can be directly included in the combustor or combustion chamber. In such embodiments, an operation can be carried out in which the total flow of the stream flowing into the combustor is at a temperature that is at most 20%, 15%, 10%, or 5% lower than the auto-ignition temperature of the fuel. In such ranges, the heating in the combustor can be sufficient such that additional methods for improving the activation energy can overcome the shortage of the heating stream(s) flowing into the combustor.

[0053] The heating of one or more flows being sent to the combustor / combustion chamber can be done in various ways. In some embodiments, one or more heaters can be arranged in communication with one or more input lines to the combustor or combustion chamber. For example, FIG. 2 shows a combustor 220 including a combustion chamber 222 configured to receive at least fuel through a fuel line 209. An input line 205 is further shown, and the input line 205 can be a line for introducing any additional material from a flow source 206. The flow passing from the flow source 206 through the line 205 can be required for the combustion of the fuel and / or can be useful for managing the combustion and / or can be useful for supplying material to the exhaust flow 230 flowing out of the combustor 220 and can include any material that can be useful. Such material can be referred to as a non-fuel flow to distinguish it from the fuel flow. Further, although only one input line 205 is shown in FIG. 2, it is understood that the combustor 220 can include two, three, four, five or more input lines, including the fuel line 209. As further described herein, any number of input lines can be heated. Similarly, any input line for supplying material to the combustor 220 as described herein can be explicitly excluded from additional heating.

[0054] The following are exemplary embodiments of materials that can be supplied to the combustor 220 individually or in any combination through the input line 205 (which can be heated by one or more methods as described elsewhere in this specification), namely an oxidizer stream, a fuel stream, a diluent stream, a working fluid stream, a coolant stream, and / or a water or steam stream. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, and a working fluid line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, and a diluent line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, and a coolant line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, and a water / steam line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, a working fluid line, and a diluent line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, a working fluid line, and a coolant line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, a working fluid line, and a water / steam line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, a diluent line, and a coolant line, and one or more of the lines described above are heated as described herein. In some embodiments, the combustor 220 can be configured to include a fuel line, an oxidizer line, a diluent line, and a water / steam line, and one or more of the lines described above are heated as described herein.In some embodiments, the combustor 220 may be configured to include a fuel line, an oxidizer line, a coolant line, and a water / vapor line, and one or more of the above lines are heated as described herein.

[0055] In some embodiments, the heated stream may specifically include one or both of oxygen and carbon dioxide. When the oxidizer stream is heated, the temperature at which the oxidizer is heated may vary as needed to improve reactivity according to the oxidation potential including the partial pressure of oxygen. The amount of fuel, and thus the oxidizer, may also be affected by residual oxygen or oxidation compounds that may be present in the recirculation flow if they interact directly with the flame zone or adjacent combustion activity.

[0056] As shown in FIG. 2, the line heater 207 corresponds to the input line 205 and provides heating effective to heat the flow passing through the input line to a temperature above the autoignition temperature of the fuel introduced into the combustor at line 209. The line heater 207 may be a single heater or may be provided as a plurality of heaters (207a, 207b). Two heaters (207a, 207b) are shown in FIG. 2, but any number of heaters may be used on a single input line as needed, and individual heaters (even on the same input line) may utilize the same heat source and / or type of heating or may use different heat sources and / or types of heating, it is understood.

[0057] In one or more embodiments, one or more line heaters utilized to heat one or more input lines may be configured to heat the line itself. For example, FIG. 3 shows a portion of an input line 305 for the input of a flow to a combustor, the input line including a line heater 307 configured to wrap, surround, or enclose at least a portion of the outer surface 305a of the wall defining the input line. The input line 305 is typically configured as a tube or similar piping having an outer wall formed of a metal (e.g., stainless steel) or similar material suitable for operation under the temperature and pressure conditions required for input lines within a power plant. Such materials are typically moderately good heat conductors, so the line heater 307 in direct contact with the outer surface 305a of the input line can transfer heat through the wall defining the line and thereby be effective in heating the flow passing through the internal space of the line. Thus, it may be beneficial for the input line 305 to include one or more insulation layers 305b along at least a portion of any part of the input line between the line heater 307 and the combustor 220. Thus, the heating transferred to the passing material is maintained within the flow up to the input of the flow to the combustor. A line heater configured to be in direct contact with the surface of the input line wall to transfer heat to the flow through the input line wall may correspond to a particular input line along a defined length of the input line. For example, referring to FIG. 2, the input line 205 may have an overall length measured as the length between the flow source 206 and the combustor 220. In various embodiments, the line heaters (207, 307) may be present along a range of from about 1% to about 99% of the overall length of a particular input line. The particular relative length may depend on the nature of the heat source used in some embodiments. For example, when a high-temperature heat source is used, the line heaters (207, 307) may surround from about 5% to about 60%, from about 5% to about 50%, from about 10% to about 40%, or from about 15% to about 35% of the overall length of the input lines (205, 305). When a low-temperature heat source is used, the line heaters (207, 307) may surround from about 25% to about 95%, from about 25% to about 90%, from about 30% to about 80%, or from about 35% to about 75% of the overall length of the input lines (205, 305).

[0058] The high-temperature heat source can be a heat source that supplies heat at a temperature above the target temperature (e.g., at least 5%, at least 10%, at least 20%, or at least 30% higher than the target temperature). The low-temperature heat source can be a heat source that supplies heat at a temperature below the target temperature (e.g., preferably within 50%, within 30%, within 20%, or within 10% of the target temperature). The target temperature is the temperature as already described above and can be based on the desired temperature in the combustor or can be based on the desired flow temperature in the input line. In some embodiments, for example, when multiple different input lines are heated separately, it may be desirable to heat each flow to a different target temperature. For example, when an oxidizer line and a diluent line are utilized, it may be desirable to heat the diluent line to a higher temperature than the oxidizer line. The heating can also vary based on the total mass flow through a given line, and an input line supplying a larger mass flow can be heated to a different target temperature than a separate input line supplying a smaller mass flow, such that the temperature in the combustor is appropriately adjusted so that the temperature in the combustor or combustion chamber exceeds the auto-ignition temperature of the fuel. Thus, the first, second, third, or more flows can be heated to their respective first, second, third, or more target temperatures so that they can appropriately reach the combustor target temperature based on the respective temperature of the flows, the relative mass flow of the flows, and similar factors recognized by one of ordinary skill in the art. Such variability can enable the use of different heat sources to heat individual input lines to appropriate target temperatures in order to achieve a combustor target temperature that exceeds the auto-ignition temperature of the fuel.

[0059] Returning to FIG. 3, the line heater 307 can be any type of heater suitable for performing the desired heating on the input line. As shown, the line heater 307 can be configured as a circulation heating jacket with a heating fluid inlet 311a and a heating fluid outlet 311b, such that a high-temperature heat transfer fluid 312a is received from the heat source 313, and the heat-depleted heat transfer fluid 312b can be returned to the heat source for reheating and recirculated. The heat source 313 can be any member or unit effective to generate heat within the desired temperature range. For example, referring to FIG. 1, the ASU 102, heat exchanger 140, compressor 160, and coolers (144, 170) can each be suitable for generating heat that can be captured in a heat transfer fluid for transfer to the input line heaters (207, 307). The ASU can include, for example, one or more compressors used to compress air that can generate sufficient heat to transfer to the line heaters (207, 307). Similarly, heat can be removed from the heat exchanger 140 at various temperature ranges as needed, and a working fluid (e.g., carbon dioxide) or any commonly utilized heat transfer fluid can be utilized as the circulating fluid for heat transfer to the line heater.

[0060] In some embodiments, the heating utilized can be performed such that the flow itself is directly heated rather than transferring heat through the wall of the line to the flow. Optionally, the direct heating of the flow can be used in combination with the use of a line heater as described above. Thus, in such embodiments, lower temperature heating can be utilized for at least one of the heating units. For example, the flow can be directly heated using a lower temperature heat source, and then a higher temperature heat source can be utilized in the line heater to further heat the flow to the target temperature. By effectively preheating using a direct flow heater, the line heater can be made smaller and / or the total energy required to achieve the target flow temperature can be less.

[0061] The use of direct heating is shown in FIG. 4A. As shown in FIG. 4A, a flow (e.g., an oxidizer, a working fluid, a diluent, or water / vapor) can be sent from a flow source 406 through a first flow line 404 to a heater 407, and the flow can be directly heated by any suitable method. Thus, the heated flow exits through a second flow line 405 for introduction into a combustor 420. As described above, the second flow line 405 can further include a line heater for additional heating. Alternatively or additionally, a line heater can be utilized for the first line 404 for stepwise heating prior to direct heating within the heater 407.

[0062] The direct heater 407 can be any member configured to heat the passing fluid flow. In an exemplary embodiment, as shown in FIG. 4B, the heater can specifically be a compression unit 407b configured to compress the flow and thereby heat the flow. The compression unit 407b can include one compressor or a plurality of compressors. Preferably, the compression unit 407b operates without intermediate cooling such that substantially all of the heat of compression can be transferred to the flow being compressed. However, if compression is effective in raising the temperature of the flow above the desired temperature, intermediate cooling can be utilized, and the heat 499 removed by the intermediate cooling can be transferred to another heater within the power generation cycle and / or to another flow within the power generation cycle to increase the efficiency of the entire power generation cycle. In another exemplary embodiment, as shown in FIG. 4C, the heater can specifically be a heat exchange unit 407c configured to transfer heat from a hotter flow to the flow sent through the first flow line 404 from the flow source 406. The high-temperature heat transfer fluid 412a can be received from a heat source (see element 313 in FIG. 3), and the heat transfer fluid 412b deprived of heat can be returned to the heat source for reheating and recycled. The heat source can, again, be any member or unit effective to generate heat within the desired temperature range. The heat exchange unit 407c and the compression unit 407b are merely exemplary and should not be regarded as limiting the types of heating units that can be utilized. Further, the use of one direct heater does not limit the use of another heater, and combinations of direct heating can be utilized separately from any line heaters or in combination with one or more line heaters.

[0063] As described herein, the heating member utilized to heat the flow can be configured directly in series such that the flow through the heating member (or a part of the input line) is heated using the heating member. In such embodiments, the heater can be configured to be adjusted automatically or manually during operation. For example, the amount of heat supplied by the heater can be adjustable such that the heating can be increased and / or decreased as needed. Similarly, the heater can be turned off during one or more operating periods if desired. For example, the heater(s) can be operable in a first temperature range at startup of the power plant and / or during a transient period to avoid frame out, and the heater(s) can have a heating output that can be gradually or slightly reduced over a given period, or can simply be turned off when heating is no longer required, such as when the power plant is operating under normal conditions. As shown in FIG. 1, the controller 190 can be included within the power plant 100, and the controller can be configured to provide one or more outputs 191 based on the receipt of one or more inputs 192. For example, one or more sensors (e.g., temperature, pressure, flow rate, etc.) can be included within the power plant and can be configured to provide their respective outputs to the controller 190, and the controller 190 can provide one or more outputs to automatically adjust the heating by one or more heaters 207. Similarly, when heating is being performed on multiple flows, the inputs and outputs can be utilized to control the heat output by various heaters and also to control the flow through the input line leading the flow to the combustor. As shown in FIG. 2, the temperature sensors T1, T2, T3 can be arranged at various positions such as near the flow source 206 or its outlet, upstream of a given heater 207, and downstream of a given heater. Thus, the output from the controller 190 can control the opening and closing of one or more valves, splitters, etc., to control the mass flow through a given input line, and / or to control the flow of the heat exchange fluid through the heater, and / or to perform further operations that can affect the temperature within the combustor 220.Furthermore, a temperature sensor 225 or the like may be present in the combustor 220 (or combustion chamber 222) to ensure that the temperature therein is within the target temperature range.

[0064] In some embodiments, the control of heating may utilize various valves, splitters, etc. to enable bypassing of one or more heaters as needed. This allows the use of materials in the heating member that may not necessarily meet all of the requirements for normal operation of the combustor. For example, during startup, transient periods, etc., a lower pressure operation may be possible. The heater(s) required during such operation may be provided in an alternative path that can be used for lower pressure operation, and the flow can be switched to return to the main input line when normal operation is achieved.

[0065] For example, FIG. 5 shows a configuration according to some embodiments in which the input line 505 includes a branch line 505a and a heater 507 corresponds to the branch line. One or more valves may be included so that the flow passing through the input line 505 can be routed through the branch line 505a. Valve 508 is present within the input line 505, and valves 518a, 518b are present upstream and downstream of the heater 507 within the branch line 505a, respectively. It is understood that similar valves or equivalent members may be present anywhere within the power generation plant to direct the flow appropriately to the appropriate members as needed. Similarly, any of valves 508, 518a, 518b (or similar members) may be automatically controlled using one of the output signals 191 from the controller 190, and the opening and closing of such valves may depend on the receipt of a specific input signal 192 to the controller. It is understood that the valves shown in the figures above may be implemented similarly in any embodiment of the present disclosure. For example, lines 311a, 311b of FIG. 3 for passing the heat transfer fluid may include valves as needed. Similarly, it is understood that similar lines for passing the heat transfer fluid are included in the embodiment shown in FIG. 5. Control of the heating process may also be achieved using an electric heater, whereby the power supplied to the heater is controlled to maintain a desired process setpoint (e.g., flow temperature, member temperature, or desired output).

[0066] In one or more embodiments, the heat utilized to heat the input stream directed to the combustor may be considered external heating or heat external to the power generation cycle. Such heating may be considered external heating to the power generation cycle since the heating thus performed does not directly result from the combustion stream. Further, such heating is utilized in addition to the heat generated by the combustion of fuel within the combustor and in addition to the heat that may be transferred from the recuperative heat exchanger(s), and may thus be considered additional heating added to the power generation cycle. Of course, if desired, the heating (at least in part) may utilize internal heating. For example, referring to FIG. 4C, the heat exchanger 407c may be the same as or a part of the heat exchanger 140 from the power generation cycle, or the stream introduced to the heat exchanger 407c through line 412a may transfer heat from the heat exchanger 140 from the power generation cycle. Thus, it may be possible to select whether to apply internal or external heating, or to combine heating sources for heating the stream(s) introduced to the combustor as described herein.

[0067] In one or more embodiments, the additional heating may be supplied directly to the combustor or combustion chamber as an alternative to, or in addition to, the heating methods described elsewhere herein. Such heating may be achieved, for example, by providing one or more elements adapted or configured to provide constant or substantially constant heating within the combustor or combustion chamber. Preferably, such a substantially constant heat source may be an externally supplied type separate from gas heat transfer. For example, as shown in FIG. 1, the heating member 226 is present within the combustor 220 (and in some embodiments within its combustion chamber 222). Non-limiting examples of such heating members are resistance coils (e.g., heat plugs or similar members) that can be electrically or otherwise powered and thus heat the combustor separately from the gas flux for heat transfer.

[0068] When such a heating member is present, the operation of the power plant, particularly the combustor, can be carried out such that the heating member is operated controllably. This may include the use of a controller 190 via one or more outputs 191 and inputs 192. For example, the heating member 226 can be controlled such that when the total flow of the flow entering the combustor is at a temperature lower than the auto-ignition temperature of the fuel, it is effective to add sufficient heat so that the overall temperature in the combustor or combustion chamber becomes higher than the auto-ignition temperature of the fuel. The heating member can increase the activation energy required in the combustor or combustion chamber to compensate for the lack of heating not done by the heating flow entering the combustor by directly raising the temperature in the combustor or combustion chamber.

[0069] Accordingly, as can be seen from the above, the present disclosure provides a member suitable for improving flame stabilization in a combustor of a power generation cycle and / or flame ignition in a combustor and a method of using the same. In addition to or as an alternative to the foregoing disclosure, there are also provided a member that provides similar benefits by adding one or more chemical species as a catalyst and a method of using the same. In particular, the present disclosure provides the use of one or more NOx species for promoting flame ignition and / or stabilization in an oxy-fuel system that can supply only a small amount of NOx species and preferably can remove NOx before discharging or releasing the emissions to the pipeline by chemically contacting any exhaust gas.

[0070] Combustion in the presence of NOx species can be advantageously promoted via one or more of the following pathways. HO2+NO=NO2+OH (1) CH3OO+NO=CH3O+NO2(2) CH3+NO2=CH3O+NO (3) In the above reactions, NO is only involved in fuel combustion by generating intermediate species (such as OH groups, CH3O, etc.) and is not consumed during combustion. In this way, NO (nitrous oxide) acts as a gas-phase catalyst.

[0071] Accordingly, by utilizing NOx species, the present disclosure can further address the issue of how to ignite an oxy-fuel combustor that will ultimately operate at high pressure. As described above, at the relatively low temperatures and / or pressures during the startup or transient periods of the combustor, it can be difficult to maintain a flame without blowout. By supplying additional catalysts to reduce the required ignition kernel energy and to help sustain ignition by reducing the reaction potential, the flame can be brought to an ignited state. Further, NO or other NOx species can be readily removed at the back end of the power generation cycle through various processes such as those disclosed in the system and process of U.S. Patent No. 9,919,268 to Allam, the disclosure of which is incorporated herein by reference.

[0072] Accordingly, according to embodiments of the present disclosure, the ignition process can be simplified in several ways. Advantageously, ignition promotion can be improved without the need for the addition of expensive equipment that adds significant additional cost to the system and without the formation of solid soot that should be avoided in a closed process that cannot protect the turbine blades. Such use of NOx as a catalyst can be used in combination with or separately from other embodiments disclosed herein. Further, by adding such a gaseous catalyst, the amount of heat that can already be added as described above can be reduced, yet the ignition ability and / or flame stability can be improved. Accordingly, the present disclosure serves as a way to reduce the igniter load, improve its reproducibility, and then maintain flame stability before the temperature and / or pressure can rise. Further, other gas-phase catalysts can be thus supplied to the flame by injection into one of the recirculation flows entering the combustor.

[0073] Accordingly, in one or more embodiments, the present disclosure may include controllably injecting NOx species, particularly NO, into a combustor, particularly a combustor within a power generation plant. The injection may occur at approximately the time of ignition in the combustor and / or at the start of the combustor (e.g., before the autoignition temperature is reached). Typically, in the case of a gas turbine, it is desirable to avoid introducing NO or other NOx species into the gas turbine (i.e., a low NOx burner). The present disclosure overcomes this recognized limitation by adding NOx species such as NO in a controlled manner.

[0074] In some embodiments, the controlled addition of NOx to the combustor may be defined in relation to adding only a specified amount of NOx species to the combustor. For example, the NOx species may be injected into the combustor such that in the bulk exhaust flow exiting the combustor, there is a total amount of NOx in the range of about 5 ppm to about 1000 ppm, about 10 ppm to about 750 ppm, about 25 ppm to about 500 ppm, about 50 ppm to about 250 ppm, or about 75 ppm to about 150 ppm based on the mass of the exhaust flow. Accordingly, the NOx species are introduced in an amount suitable for reducing the required ignition kernel energy and shortening the ignition delay time.

[0075] NOx can be an undesirable byproduct in a power generation process that utilizes air as an oxidizer, but the NOx in the present disclosure relates to a chemically present species (chemically present as NOx prior to combustion) that is intentionally added and is not actually a combustion byproduct resulting from nitrogen oxidation. In particular, in the context of what is claimed herein, combustion may be carried out such that the flow entering the combustor is sufficiently nitrogen-deficient to form NOx. Further, the oxidizer can be substantially pure oxygen and the use of air as an oxidizer can be excluded, so it is understood that the NOx species present in the combustor exhaust are intentionally added NOx and not combustion byproducts.

[0076] The injection of NOx species into the combustor can be substantially continuous throughout the operation of the power plant. In this way, the presence of the catalyst material can be effective in reducing the activation energy of the process (e.g., the auto-ignition temperature of the fuel), and thus the required amount of energy needed to achieve and / or maintain a flame within the combustor. Further, to the extent that the fuel composition can vary during the operation of the power plant, the content of the NOx species injected into the combustor can be varied to substantially balance the combustion. For example, if the oxidant concentration and / or the calorific value of the fuel decreases, the NOx content can be increased taking into account the loss of available activation energy. Similarly, if the oxidant concentration and / or the calorific value of the fuel increases, the NOx content can be reduced taking into account the increase in available activation energy. Thus, NOx can function as a control component that can be automatically adjusted by monitoring downstream parameters (e.g., combustor exhaust flow rate and / or temperature) and / or upstream parameters (e.g., oxidant flow rate, fuel flow rate, or known changes in fuel chemical composition).

[0077] In a further embodiment, the injection of NOx species into the combustor can be carried out for a certain period of time. For example, the NOx injection may be executed until a defined threshold is reached. For example, when the combustor operates at a defined minimum temperature, when the power plant achieves a defined output level, or when the combustor exhaust flow reaches a defined composition, the NOx injection can be reduced or completely eliminated. Further, monitoring can be carried out to ensure that the NOx injection can be increased or restarted if one of the defined parameters is below the required threshold, as this can ensure that potential blowouts are avoided or can be effective in generally normalizing the operation of the power plant.

[0078] An exemplary embodiment of a combustion device suitable for use in a power generation plant as described herein is shown in FIG. 6. As shown in FIG. 6, the combustor 620 may be substantially configured as already described with respect to FIGS. 1 and / or 2, and such a configuration may be combinable in certain embodiments to be able to inject NOx simultaneously with the heating of one or more lines as already described above. In FIG. 6, the combustor 620 includes a combustion chamber 622 and generates an exhaust stream 630. The combustor 620 includes a fuel line 609 for fuel input and one input line 605 or a plurality of input lines (605, 605a, 605b, 605c, etc.) for the input of one or more non-fuel streams. One or more lines 685 may similarly be provided for supplying one or more streams each containing one or more NOx species. As shown, the line(s) 685 may be configured to add one or more NOx species to either the fuel line 609 or one or more of the line(s) (605 - 605c) supplying the non-fuel stream(s). Alternatively or additionally, the line(s) 685 may be configured to directly inject one or more NOx species into the combustor 620 (including directly into the combustion chamber 622).

[0079] In some embodiments, the control addition of NOx to the combustor can be defined in relation to a specific chemical pathway. For example, in one or more embodiments, the present disclosure can specifically include adding nitrous oxide (NO) via the electrocatalytic reduction of ammonia. For example, as shown in FIG. 6, a dedicated reactor 696 is included within the power plant, and such a reactor can be configured to receive the input streams (695a, 695b) necessary to convert ammonia to NO. At least a portion of the NO formed can be passed through a dedicated line 697 and utilized as at least a portion of the NOx species sent directly to the combustor and / or to one or more other input lines (609, 605 - 605c). Through such reactions, the local NO concentration in one or more of the streams flowing into the combustor or combustion chamber (e.g., within a gas turbine) can be adjusted as needed to be within a desired range, as described elsewhere herein. The streams within lines 695a, 695b can be, for example, ammonia, catalyst, oxidizer, etc. useful for carrying out the reactions necessary for the conversion. Reactor 696 can be a heating reactor, if necessary.

[0080] In some embodiments, the control addition of NOx to the combustor can be defined in relation to a specific location of NOx injection. For example, a dedicated NOx injection nozzle can be disposed in the combustor or combustion chamber such that NOx can be directly injected into the fuel-oxidizer mixing zone under design conditions. In another exemplary embodiment, the NOx can be mixed with one or both of the fuel stream and the oxidizer stream before being injected into the combustor or combustion chamber under ignition and startup conditions. In a further exemplary embodiment, the NOx can be injected into one or more recirculation streams flowing into the combustor or combustion chamber. In particular, the NOx can be injected into a plurality of streams being sent to the combustor or combustion chamber and optionally further directly injected into the primary flame zone within the combustor or combustion chamber. In a preferred embodiment, the NO can be injected as close as possible to the flame mixing zone of the combustor. In some embodiments, this can involve adding the NOx directly to the combustor through a dedicated line. In other embodiments, this can involve adding the NOx to another inlet line immediately upstream of the combustor through a union, valve, etc. Further, this can include a configuration in which the combustor includes one or more nozzles configured such that a catalyst directly enters in the flame mixing zone.

[0081] In one or more embodiments, the present disclosure may further include means for removing NOx at the back end of the cycle in processes such as those separately described above. For example, separator 150 may be configured to remove NOx by reaction with one or both of SOx and water and / or by addition of one or more oxidizing components, in particular materials recognized as improved oxidants (e.g., peroxides, superoxides, ozone, and / or halogen oxides). Additionally, NOx injection can preferably be controlled in such a way that not only can NOx be injected at any position within the cycle, but it can be carefully increased in local NOx concentration and easily decreased when it is no longer necessary to exert a catalytic effect on flame control. Thus, NOx species (in particular, NO) can be supplied in any one of the following ways, or a combination thereof: by direct injection into the combustor or combustion chamber, by mixing with the fuel stream flowing into the combustor or combustion chamber, by mixing with the oxidant stream flowing into the combustor or combustion chamber, by mixing with the diluent stream (e.g., CO2 stream) flowing into the combustor or combustion chamber, by mixing with the working fluid stream flowing into the combustor or combustion chamber, by mixing with the water or steam stream flowing into the combustor or combustion chamber, or by mixing with the cooling stream flowing into the combustor or combustion chamber.

[0082] An oxy-fuel combustion cycle suitable for use in accordance with one or more embodiments of the present disclosure may further include various members suitable for implementing a power generation method. Exemplary embodiments of the members of the systems and methods that may be realized in the present disclosure are described in U.S. Patent No. 8,596,075, U.S. Patent No. 8,776,532, U.S. Patent No. 8,869,889, U.S. Patent No. 8,959,887, U.S. Patent No. 8,986,002, U.S. Patent No. 9,062,608, U.S. Patent No. 9,068,743, U.S. Patent No. 9,410,481, U.S. Patent No. 9,416,728, U.S. Patent No. 9,546,815, U.S. Patent No. 10,018,115, U.S. Patent Application Publication No. 2012 / 0067054, and U.S. Patent Application Publication No. 2018 / 0133647, the disclosures of which are incorporated herein by reference.

[0083] Those skilled in the art who benefit from the teachings presented in the above description and the associated drawings will envision many modifications and other embodiments of the subject matter of the present disclosure. Accordingly, it is to be understood that the present disclosure is not limited to the specific embodiments described herein and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a general and descriptive sense and are not intended to be limiting.

Claims

1. A method for propagating a flame in a combustor of a power generation plant, the method comprising: feeding a fuel having a defined autoignition temperature into the combustor; further feeding at least one non-fuel stream into the combustor; feeding into the combustor a chemical catalyst comprising at least one NOx species in an amount sufficient to reduce the activation energy level necessary to achieve or maintain a flame in the combustor or its combustion chamber, wherein the at least one NOx species is not derived from combustion in the combustor; A method comprising the above.

2. A method for propagating a flame in a combustor of a power generation plant, the method comprising: feeding a fuel having a defined autoignition temperature into the combustor; further feeding at least one non-fuel stream into the combustor, wherein the feeding is through a line, the line includes a branch line, and the branch line is separable from the line using one or more valves that selectively enable or disable the flow of at least one non-fuel stream through the branch line; heating the at least one non-fuel stream sufficiently so that the total flow of the stream flowing into the combustor is at a temperature higher than the autoignition temperature of the fuel; Including The method of heating the at least one non-fuel stream is carried out using heat not derived from combustion.

3. The method according to claim 1 or claim 2, wherein the method is carried out at startup of the power generation plant or during a transient period of operation of the power generation plant.

4. The method according to claim 3, wherein the startup of the power generation plant or the transient period of operation of the power generation plant is defined in relation to the power generation plant operating at an output less than 75% of its normal operating output.

5. The method according to claim 1 or claim 2, wherein the non-fuel stream is one or more of an oxidant stream, a working fluid stream, a dilution stream, and a water / steam stream.

6. The method according to claim 1, further comprising feeding an oxidant into the combustor, and the chemical catalyst comprising at least one NOx species is fed into the combustor in combination with one or both of the fuel and the oxidant.

7. The method according to claim 1, further comprising reacting at least ammonia in a reactor to produce the at least one NOx species.

8. The introduction of the chemical catalyst containing the at least one NOx species is substantially continuous during the operation of the power plant, and the method further includes adjusting the content of the chemical catalyst containing the at least one NOx species based on changes in one or more further operating parameters of the power plant, the method according to claim 1.

9. The introduction of the chemical catalyst containing the at least one NOx species is carried out until a specified threshold value is reached, the method according to claim 1.

10. The specified threshold value is the combustor operating temperature or the output of the power plant, the method according to claim 9.

11. The chemical catalyst containing the at least one NOx species is introduced in a sufficient amount such that the amount of at least one NOx species present in the exhaust flow exiting the combustor is from about 5 ppm to about 1000 ppm, the method according to claim 1.

12. Heating the at least one non-fuel stream includes heating at least a portion of the line using one or more line heaters, the non-fuel stream flowing through the line to the combustor, the method according to claim 2.

13. Heating at least a portion of the line includes heating at least a portion of the branch line, the method according to claim 12.

14. A power plant, a combustor, a fuel line configured to introduce a fuel having a specified auto-ignition temperature into the combustor, an input line configured to deliver a non-fuel stream to the combustor, the input line including an input branch line, the input branch line being separable from the input line using one or more valves that selectively enable or disable the flow of the non-fuel stream through the input branch line, the input line a turbine or expander in fluid communication with the combustor, a line heater operably arranged with the input line to sufficiently heat the non-fuel stream such that the total flow of the stream flowing into the combustor is at a temperature higher than the auto-ignition temperature of the fuel, the line heater being configured to heat the non-fuel stream using heat not derived from combustion, the line heater comprising a power plant.

15. The line heater is configured to receive a heating stream and transfer heat therefrom to the input line, the power plant according to claim 14.

16. The power generation plant according to claim 14, wherein the line heater is operatively arranged on the input branch line. **Claim 17** The power generation plant according to claim 14, wherein the input branch line is separable from the input line by using one or more valves that selectively enable or disable the flow of the non-fuel stream through the input branch line. **Claim 18** The power generation plant according to claim 14, further comprising a catalyst line configured to introduce a chemical catalyst containing at least one NOx species into the combustor. **Claim 19** The power generation plant according to claim 18, further comprising a reactor configured to receive at least ammonia and discharge a stream containing the at least one NOx species into the catalyst line.

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