Patent Description:
Combustion turbines combust a mixture of compressed air and fuel to produce combustion gases. The combustion gases may flow through one or more turbine stages to generate rotational energy for use by a load (such as a generator). The combustion gases may include various combustion by-products, such as carbon monoxide (CO), nitrogen oxides (NOx), carbon dioxide (CO2), and so on. These by-products, or emissions, are generally subject to stringent regulations. In some cases, operating combustion turbines with an extended output power range may increase operational flexibility and efficiency of a power generation system. However, the cost of add-on emission controls to meet emission targets while maintaining the extended output power range of combustion turbines may become excessive. <CIT> suggests a method in which, in a combustion turbine operating at low load, to reduce carbon monoxide emissions, the combustion temperature is increased. Said increase in combustion temperature is achieved in operating variable compressor inlet guide vanes for reducing the air mass flow and/or by increasing a flow rate of fuel supplied to the combustion chamber. <CIT> teaches that in a combustion turbine, during turndown operation, emission levels increase and suggests a method for reducing the formation of NOx. According to the teaching of <CIT>, said reduction in NOx formation is achieved by bleeding air from the compressor, and/or energizing a fuel injector to inject fuel or a fuel/air mixture into the combustion gases so as to reduce NOx emissions. <CIT> further suggests to inject diluents for reducing NOx production. <CIT> is directed towards a system including a gas turbine engine, a selective catalytic reduction system, and a control system configured to regulate operation of the selective catalytic reduction system based at least partially on preset variations in an emissions compound of exhaust gases produced by the gas turbine engine. <CIT> suggests a system and method for tuning the operation of a turbine and optimizing the mechanical life of a heat recovery steam generator. Provided therewith is a turbine controller, sensor means for sensing operational parameters, control means for adjusting operational control elements. The controller is adapted to tune the operation of the gas turbine in accordance to preprogrammed steps and in response to operational priorities selected by a user. The operational priorities preferably comprise optimal heat recovery steam generator life. <CIT> discloses systems and methods for controlling compressor extraction air flows from a compressor of a turbine system during engine turn down are provided. In one embodiment, a method for controlling compressor extraction air flows from a compressor of a turbine system during turn down includes a control unit monitoring one or more operating parameters of a turbine system associated with an exit temperature of a combustor of the turbine system. The method further includes the control unit detecting one or more operating parameters meeting or exceeding a threshold associated with a decrease in the exit temperature of the combustor. In response to detecting one or more operating parameter meeting or exceeding the threshold, a control signal is transmitted to at least one variable orifice located in the turbine system causing at least one variable orifice to alter at least one extraction air flow from the compressor.

Accordingly, it should be understood that these statements are to be read in this light and not as admissions of any kind.

It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of the invention, as defined in the appended claims.

In a first aspect, a method as set forth in claim <NUM> is provided.

In a second aspect, a system as set forth in claim <NUM> is provided.

Furthermore, any numerical examples in the following discussion are intended to be nonlimiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments. Furthermore, the phrase A "based on" B is intended to mean that A is at least partially based on B. Moreover, the term "or" is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase A "or" B is intended to mean A, B, or both A and B.

Combustion turbine generators (CTGs) in power plants create emission gases from their combustion processes during operations. The emission gases contain toxic gases and pollutants (such as nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbon), which are treated (e.g., by catalytic assemblies in exhaust systems of the CTGs) to meet emission regulations. In some instances, the catalytic assemblies are selective catalytic reduction (SCR) systems, which operate optimally at certain concentrations of emissions. Based on given operating constraints (such as load conditions and emission regulations), a combustion turbine controller may execute corresponding actions to control certain gas concentrations and/or gas mass flows in the emission gases in compliance with emission regulations.

The present disclosure relates generally to operating combustion turbines in wide range of power outputs (e.g., partial and/or no load) while meeting emission targets under environmental regulations. Using the disclosed technologies herein may improve operational performance of the CTGs. In an embodiment, NOx emissions compliance may be achieved at reduced hardware-cost, complexity, and enhanced reliability of a CTG due to a narrower inlet NOx flow range to the SCR than approaches with SCR modifications, which would otherwise be used to post-process inlet NOx conditions with a wider inlet NOx flow range to the SCR. CO emissions compliance may be achieved due to a higher combustion-temperature at low load operations as compared to approaches with added CO catalyst expenses, which would otherwise be necessary to post-process high CO flows at low load operations that often have lower combustion temperatures.

Using the disclosed technologies herein may improve operability of the CTGs. In an embodiment, at low-load steady-state and/or during transient operations (e.g., transient to lower load operations), a better or equal compressor stall margin in the CTGs may be achieved as compared to CTG operations using reduced compressor pressure ratios for a given operating point via bleeds. The increased compressor stall margin may reduce the likelihood of CTG component distress and damage during steady-state or transient operation. Using the disclosed technologies herein may also improve component life and durability of the CTGs. In an embodiment, combustion engine hot-section life may be improved due to reduced water injection (e.g., in CTGs using water as a diluent).

Besides improvements in operability and durability of the CTGs and their components as described above, the disclosed technologies herein may broaden CTG applications in power generation systems. In some applications, certain electricity markets may financially compensate CTG power plants for a wider power operating range that extends to lower loads, which are achievable by implementing the disclosed technologies (such as simple ammonia (NH<NUM>) injection systems sized for high NH<NUM> flows and SCR systems with small and more efficient CO catalysts). Such implementations facilitate low load CTG operations for less cost than upsized and complex modifications (e.g., SCR system modifications). Therefore, added revenue of the enhanced operating range may generate a larger profit for the CTG power plant as compared to using the upsized and complex modifications. In an embodiment, a vendor (e.g. a power distributor) may sell electricity generated from the CTGs implemented with the disclosed technologies, which provide the same or similar operating range as the CTGs facilitated with expensive modifications, thereby increasing the price, profit margin, and/or incentives for selling electricity.

In certain cases, hybrid power plants containing energy storage systems (ESS) and/or thermal generation assets, which provide a wide power operating range (e.g., extending to low loads), may be designed with equivalent or lower cost and with greater flexibility than those without using the disclosed technologies. For example, to operate at loads lower than a threshold load of a thermal asset, the ESS may consume excessive power beyond a desired plant power operating point. Consuming this power may require increasing the power output and/or energy capacity of the ESS, thereby adding capital and operating costs. To avoid such additional cost, hybrid power plants may implement thermal modifications to facilitate low load thermal operation and a smaller ESS. As a comparison, with the disclosed technologies, the minimum load of the thermal asset may be higher than the thermal modifications, but the total cost with the larger ESS may be the same or lower. The use of the ESS may add flexibility and potential revenue sources that may scale with the ESS size. As ESS prices may reduce over time, the added cost of the ESS may reduce accordingly, thereby reducing the total cost. Such increased flexibility may be helpful to increase profit margins, reduce the price, or add large amounts of energy storage to increase the value and potentially increase the profit margins.

With the preceding in mind, turning now to the drawings, <FIG> is a block diagram of an embodiment of a combustion turbine system <NUM>. As an example, the combustion turbine system <NUM> may be part of a combined cycle system or combined with other combustion turbine systems <NUM> to power one or more loads <NUM>. Specifically, the combustion turbine system <NUM> is generally configured to drive the load <NUM> by combusting a mixture of compressed air <NUM> and fuel <NUM> (e.g., natural gas, light or heavy distillate oil, naphtha, crude oil, residual oil, or syngas). The combustion is performed within a combustor <NUM>, which may include one or more combustion chambers. A fuel sensor (FS) <NUM> may be used to monitor the fuel injection rate to the combustor <NUM>. Air <NUM> goes into an air intake at the compressor <NUM>, is filtered, and then is compressed in the compressor <NUM> via one or more compression stages. A compressed air stream <NUM> generated from the compressor <NUM> is directed into the combustor <NUM>.

As illustrated, the compressor <NUM> may include one or more bleed valves (BVs) <NUM>. The degree of valve opening or closing of the bleed valves <NUM> may be adjustable. For example, when the combustion turbine system <NUM> is operating during shutdown or at low power operation, the bleed valves <NUM> may be adjusted to certain degree(s) to reduce the air flow rate. The bleed valves <NUM> are installed at different locations on the compressor <NUM> or between compressors in a multi-compressor system.

To begin the combustion process within the combustor <NUM>, the compressed air stream <NUM> is mixed with fuel <NUM>. Using the mixture of the fuel <NUM> and the compressed air stream <NUM>, ignition may occur within the combustion chamber(s). The ignition produces hot combustion gases <NUM> that power the combustion turbine system <NUM>. More specifically, the hot combustion gases <NUM> flow through a turbine <NUM> with one or more compression stages that drives the load <NUM> via a shaft <NUM>. For example, the combustion gases <NUM> may apply motive forces (e.g., via convection, expansion, and the like) to turbine rotor blades within the turbine <NUM> to rotate the shaft <NUM>. In an example process, the hot combustion gases <NUM> force turbine blades in the turbine <NUM> to rotate the shaft <NUM> along an axis of the combustion turbine system <NUM>. As illustrated, the shaft <NUM> may be connected to various components of the combustion turbine system <NUM>, including the compressor <NUM> or the load <NUM>.

In some embodiments, various controlling and monitoring devices may be used to control and monitor the combustions in the combustor <NUM>. In the embodiment of <FIG>, the combustor <NUM> includes one or more fuel nozzles (FNs) <NUM>, which may be at different locations on the combustor <NUM>. Fuel flow to the fuel nozzles <NUM> is adjustable so that the fuel injections to the combustor <NUM> are controllable. For instance, the controller <NUM> may utilize fuel flow circuits coupled to the fuel nozzles <NUM> to adjust a fuel-to-air ratio in the combustor <NUM>. Adjusting the fuel nozzles <NUM> may enable controlling the fuel split between the fuel injection ports (e.g., fuel nozzles <NUM>) on the combustor <NUM>. The controllable fuel split may change certain physical properties of a combustion flame <NUM>, such as the temperature and the location of the combustion flame <NUM>. In some embodiments, the controller <NUM> may utilize the fuel flow circuits to adjust one or more fuel delivery valves to direct fuel flow into passages in one or more fuel nozzles <NUM> and in the combustor <NUM>. In some embodiments, additional monitoring device(s) may be used to monitor certain physical properties of the combustion flame <NUM>. For example, temperature sensor(s) (TSs) <NUM> may be used to measure the temperature of the combustion flame <NUM>. In certain embodiments, flame detector(s) (FDs) <NUM> may be used to detect the presence and/or location of the combustion flame <NUM>.

As illustrated in <FIG>, a diluent injection (DI) system <NUM> is coupled to the combustor <NUM>. The diluent injection system <NUM> may inject specific diluent (such as water or steam) into the combustor <NUM> to change certain physical properties (e.g., temperature) of the combustion flame <NUM>, therefore maintaining specific emission(s) in the exhaust gases <NUM> in compliance with emission regulations. For example, the water or steam injection may be used by the diluent injection system <NUM> to cool the temperature of the combustion flame <NUM> to reduce the formation of NOx.

As previously noted, the shaft <NUM> may connect the turbine <NUM> to the compressor <NUM> to form a rotor. The compressor <NUM> includes compressor blades coupled to the shaft <NUM>. Thus, rotation of turbine blades in the turbine <NUM> may cause the shaft <NUM> connecting the turbine <NUM> to the compressor <NUM> to rotate the compressor blades within the compressor <NUM>. This rotation of compressor blades in the compressor <NUM> causes the compressor <NUM> to compress air <NUM> to generate the compressed air stream <NUM>. As previously noted, the compressed air stream <NUM> is then fed to the combustor <NUM> and mixed with other combustion components. The shaft <NUM> may drive the compressor <NUM> in addition to or in lieu of the load <NUM>. As an example, the load <NUM> may be a generator of the combustion turbine system <NUM>. Additionally or alternatively, the load <NUM> may include a propeller, a transmission, a drive system, or any other mechanism that is configured to receive mechanical force through rotation of the shaft <NUM>.

Once the turbine <NUM> extracts work from the hot combustion gases <NUM>, a stream of exhaust gas <NUM> is provided to an exhaust section <NUM>, where the exhaust gas <NUM> may be further processed and/or cooled. For example, in the illustrated embodiment, the exhaust section <NUM> includes a catalyst assembly <NUM>. The catalyst assembly <NUM> is an exhaust emission control device that reduces toxic gases and pollutants in the exhaust gas <NUM> by using various after-treatment emission control technologies, such as oxidation catalysts and/or selective catalytic reduction (SCR).

The catalyst assembly <NUM> may use one or more oxidation catalysts to treat specific emission(s) in the exhaust gas <NUM>. The oxidation catalysts may include CO catalyst, NOx catalyst, unburned hydrocarbon catalyst, and/or any similar metal-based (e.g., platinum-based) catalyst. For example, the catalyst assembly <NUM> may include NOx catalysts to destroy NOx gases within the stream of exhaust gas <NUM>. The stream of exhaust gas <NUM> may then exit the exhaust section <NUM> after treatment provided by the catalyst assembly <NUM>.

The catalyst assembly <NUM> may also include a selective catalytic reduction (SCR) system. The SCR system converts NOx with the aid of catalyst(s) (e.g., titanium oxide) into diatomic nitrogen (N<NUM>) and water (H<NUM>O). A gaseous reductant (such as anhydrous ammonia), aqueous ammonia, or urea, may be added to the exhaust gas <NUM> and be adsorbed onto the catalyst(s). For example, an ammonia (NH<NUM>) injection system may be used to inject the ammonia into the exhaust gas <NUM>. The exhaust gas <NUM> mixes with the ammonia and enters a reactor containing the catalyst(s), where the ammonia reacts selectively with the NOx within a specific temperature range and in the presence of the catalyst(s).

The exhaust section <NUM> includes various monitoring device(s) to monitor the physical properties (e.g., temperature of the exhaust gas <NUM>) and/or chemical properties (e.g., emission gas concentrations). For example, the exhaust section <NUM> may include one or more temperature sensors (TSs) <NUM> to measure the temperature of the exhaust gas <NUM>. In some embodiments, the exhaust section <NUM> may include one or more emission sensors (ESs) <NUM> to measure the concentrations and/or mass flows of specific emission gases (e.g., CO and NOx).

As illustrated, combustion turbine system <NUM> includes one or more controllers <NUM>. The controller <NUM> may include one or more processors <NUM> and memory <NUM>, which may be used collectively to support an operating system, software applications and systems, and so forth, useful in implementing the techniques described herein. Particularly, the controller <NUM> may include code or instructions stored in a non-transitory machine-readable medium (e.g., memory <NUM>) and executed, for example, by the one or more processors <NUM> that may be included in the controller <NUM>. The processor(s) <NUM> may receive parameters of operation from the various components of the combustion turbine system <NUM> including rotation speed of the shaft <NUM>, frequency and/or voltage of electric power generated by the combustion turbine system <NUM> via a generator (e.g., load <NUM>) driven by the shaft <NUM>, a demand from one or more load(s) <NUM>, or other suitable parameters. In some embodiments, some parameters are measured directly while other parameters are determined indirectly from other measurements. For example, in certain embodiments, the controller <NUM> may utilize an algorithmic model or look-up table (e.g., stored in memory <NUM>) to derive various parameters, such as the operating speed of the shaft <NUM> or a connected generator using electrical parameters such as frequency or voltage of the electric power generated by the generator.

Further, the controller <NUM> may monitor operation of various parts of the combustion turbine system <NUM> via specific monitoring devices. The monitored parameters may include, but are not limited to, the following: injection rate of the fuel <NUM> (e.g., via the fuel sensor <NUM>), temperature and location of the combustion flame <NUM> in the combustor <NUM> (e.g., via a temperature sensor <NUM> and a flame sensor <NUM>), temperature of the exhaust gas <NUM> in the exhaust section <NUM> (e.g., via the temperature sensors <NUM>), concentrations and/or mass flows of specific emission gases (e.g., CO and NOx) of the exhaust gas <NUM> in the exhaust section <NUM> (e.g., via emission sensors <NUM>), or other relevant parameters. The monitored parameters may be used to control (e.g., adjust) operating parameters of one or more aspects of the combustion turbine system <NUM>. For example, during the operation of the combustion turbine system <NUM>, the temperature of the exhaust gas <NUM> inside the exhaust section <NUM> may be measured by the one or more temperature sensors <NUM>. Based on the measured temperature of the exhaust gas <NUM>, the controller <NUM> may cause the one or more bleed valves <NUM> to adjust the degree of valve opening, and/or may control the fuel split between the fuel nozzles <NUM>, therefore changing (e.g., increasing) the temperature of the exhaust gas <NUM>.

As illustrated, the controller <NUM> may include a catalyst controller <NUM>. The catalyst controller <NUM> is configured to communicatively couple to the catalyst assembly <NUM>. In one example, the catalyst controller <NUM> is configured to receive signals representative of a temperature of an exhaust flow upstream of the catalyst assembly <NUM> and the temperature of a treated exhaust flow downstream of the catalyst assembly <NUM>. The one or more temperature sensors <NUM> may be disposed upstream of the catalyst assembly <NUM> and downstream of the catalyst assembly <NUM>. The catalyst controller <NUM> may determine a target temperature, which is based at least in part on suitable emission level(s) (e.g., NOx, and/or CO level). The catalyst controller <NUM> may generate (e.g., via the one or more processors <NUM>) control signals that correspond to the target temperature. For example, the control signals may include instruction(s) to increase the temperature of the exhaust gas <NUM> before the exhaust gas <NUM> flows into the catalyst assembly <NUM>. The control signals corresponding to the target temperature may be sent to the one or more bleed valves <NUM> on the compressor <NUM> to adjust the degree of valve opening, or to the one or more fuel supply lines (not separately shown) to the combustor to control the fuel split between the fuel nozzles <NUM>, therefore regulating the temperature of the exhaust gas <NUM> to the target temperature. By controlling the temperature of the exhaust gas <NUM> flowing into the catalyst assembly <NUM>, certain emission gases (such as NOx and CO) may be controlled to achieve suitable levels in compliance with emission regulations, regardless of the operating load of the combustion turbine system <NUM>.

It should be noted that the components described above with regard to the combustion turbine system <NUM> are example components. For instance, some embodiments of the combustion turbine system <NUM> may include additional or fewer components than those shown. For example, various embodiments of the combustion turbine system <NUM> may include multiple shafts, multiple combustors, multiple catalyst assemblies, and/or other suitable turbine system components.

As stated previously, exhaust emission control devices (e.g., the catalyst assembly <NUM>) may be used to reduce toxic gases and pollutants, such as NOx and CO gases, before expelling the exhaust gas into atmosphere through the exhaust section <NUM>. In operation, a combustion turbine (e.g., the combustion turbine system <NUM>) may produce large amounts of emissions, which are treated (e.g., by the catalysts and/or SCR) before expelling into atmosphere to meet emission regulations.

With the preceding in mind, material related to exhaust gases (e.g., NOx and CO gases) expelled from combustion engines in a power plant is provided below to impart some familiarity with such exhaust gases and provide useful real-world context for other aspects of the disclosure.

The term "NOx" refers to nitrogen oxides that are classified as air pollution, such as nitric oxide (NO) and nitrogen dioxide (NO<NUM>). NOx gases may be produced from the reaction among nitrogen and oxygen during combustion of fuels (e.g., hydrocarbons) in combustion turbines (e.g. the combustion turbine system <NUM>). In some cases, CTG power plants may have operating permits that set limits on NOx emissions as a limit on air pollution. Carbon monoxide (CO) is a colorless, odorless, and tasteless flammable gas that is also a regulated atmospheric pollutant.

The NOx and CO gases produced during combustion may lead to an emission increase without readjustment of operational settings of the CTG power plant operation and maintenance. For instance, in some embodiments, the NOx emission may increase in high combustion flame temperatures often used at high load operation. In other embodiments, the CO emission may restrict partial/no load operation, which may be used more frequently due to the increasing involvement of intermittent renewable power (such as wind power and solar power).

CTG power plants may be designed to operate in a specific power range to maintain emissions compliance (e.g., meeting certain emission targets). The emissions targets may include instantaneous and/or integrated exhaust gas concentrations or masses for specific constituent gases such as NOx and CO. The operating power range of a CTG power plant is specified by a minimum operating power (Pmin) and a maximum operating power (Pmax). A power plant operating at a lower Pmin provides larger dispatch flexibility and electrical grid efficiency. However, operating in an extended power range (e.g., with a Pmin that is less than <NUM>% of a CTG power plant full load) may not align with the existing combustion turbine designs (such as exhaust emissions controls including diluent injection, precise fuel injection, and combustion control), which were originally made for a limited power range (e.g., with a Pmin that is higher than <NUM>% of the CTG power plant full load).

To operate in an extended power range, a combustion turbine (CT) in a power plant may be modified to meet the emission targets across the CT's operating range. For example, the CT modifications may include implementing advanced combustion control technologies (e.g., fuel injection hardware for precise fuel control). Additionally, or alternatively, the CT modifications may be related to post-processing of the exhaust gases, such as increasing CO catalyst, modifying ammonia injection system for lower NOx flow range, advanced SCR control, or a combination thereof. However, such modifications may result in excessive cost, which may inhibit the CTG power plant operational flexibility. For example, a CTG power plant initially designed with a predetermined cost may limit the minimum operating power to a specific threshold (e.g., a power output that is <NUM>% of CTG power plant full load). As such, the CTG power plant may be inhibited from a lower power operation mode (e.g., an operation with output power lower than <NUM>% of CTG power plant full load) due to excessive cost (e.g., cost related to CO catalyst usage and/or SCR modification).

The technologies described in the present disclosure provide a suitable approach for CTs to operate in a wider power range in emissions compliance while avoiding expensive CT modifications (e.g., upsizing the SCR system and/or modifying the fuel injection system). <FIG> shows a flow chart depicting an emission control process <NUM> that may be used to operate CTs (e.g., the combustion turbine system <NUM>) in an extended power range without experiencing costly modifications.

The emission control process <NUM> is initiated when a combustion turbine (CT) enters an operating state (block <NUM>) that is different from a previous operating state. The CT receives an indication that the combustion turbine is to operate at a load lower than a full-load (e.g., partial or no load). The indication may include a processor-generated signal (e.g., from the controller <NUM>), an analog signal, a sensor signal from a sensor, an artificial intelligence inference made using a neural network, a user input, and/or other suitable signals or inputs. For example, the CT may receive an instruction (e.g., from a CT operator via a certain user interface that may be communicatively coupled to the controller <NUM>) to switch from a high load operation (e.g., higher than <NUM>% of CT full load) to a low load operation (e.g., lower than <NUM>% of CT full load), to switch from the low load operation to the high load operation, to shut down from an active state, and to startup from inactive state.

As discussed below, when switching from a high load operation to a low load operation, the controller <NUM> may determine emission targets (e.g., output target emission from exhaust section <NUM>) for different by-products based on the new load and other operation-related information. According to the new emission targets, the CT may perform a variety of operations to control emissions through regulating certain gas concentrations and/or gas mass flows in the exhaust gases in compliance with the emission targets. As load reduces, total exhaust gas mass flow reduces accordingly. To maintain a consistent NOx rate between high and low loads, the controller <NUM> increases a combustion temperature to raise NOx concentration in the reduced total exhaust gas mass flow when operating in a low load mode. With consistent NOx flow rates, the SCR may consistently handle the NOx in both high and low loads. Furthermore, by increasing the combustion temperature, the CO concentration is reduced below the CO concentration at lower temperatures. In some embodiments, the controller <NUM> may change a fuel type (e.g., switch to another fuel such as hydrogen gas) or change a mixture ratio of different fuel types to utilize an increased combustion temperature to maintain a consistent NOx rate between high and low loads.

After the CT enters a new operating state (e.g., a low load operation), the controller <NUM> may determine CT emission targets and operation parameters for the new state (block <NUM>). The emission targets may include, but are not limited to, the following: instantaneous and/or integrated exhaust gas concentrations, the instantaneous and/or integrated exhaust gas masses or mass flows, and constraints for certain exhaust gases (e.g., NOx and CO gases) in a CT exhaust flow (e.g., a treated exhaust flow downstream of the catalyst assembly <NUM>). As discussed previously, the CT is designed to operate in a specific power range in emissions compliance (e.g., meeting certain emission targets listed above).

Determining CT emission targets and operation parameters may be conducted by the controller <NUM>, via the one or more processors <NUM> and memory <NUM>. For instance, based on the new operating state of the CT (e.g., <NUM>% of CT full load), the controller <NUM> may access certain CT operation-related code or instructions stored in a non-transitory machine-readable medium (e.g., memory <NUM>). The controller <NUM> may execute accessed code or instructions by the one or more processors <NUM> to determine the emission targets and operation parameters corresponding to the new operating state of the CT. The operating parameters are related to CT operation and performance, which may be collected and/or derived empirically during CT manufacturing, on-site performance tests during operation, and/or the like.

In some embodiments, the controller <NUM> may receive, from a different source, additional/supplemental information (e.g., CT operating constraints) that may be used in determining the emission targets and operation parameters (block <NUM>). For instance, the controller <NUM> may receive, via a user interface (e.g., a CT control interface controlled using a keyboard, mouse, or keypad), information related to given CT operating constraints. Examples of the given CT operating constraints may include specific gas concentration or mass flow limits of the exhaust gas <NUM> flowing into the catalyst assembly <NUM>, and/or specific gas concentration or mass flow limits of treated exhaust gas exiting from the exhaust section <NUM>, and other operating constraints.

Additionally, or alternatively, the controller <NUM> may use a look-up table stored in a non-transitory machine-readable medium (e.g., memory <NUM>) to search the CT emission targets and operation parameters corresponding to the new operating state of the CT, with or without the additional/supplemental information that relates to given CT operating constraints. In some cases, the controller <NUM> may use a simulation model stored in a non-transitory machine-readable medium (e.g., memory <NUM>) or a remote network (e.g., a cloud) to determine the CT emission targets and operation parameters based at least in part on the additional/supplemental information. For example, the simulation model may take inputs, such as certain operating parameters/settings related to the new operating state of CT and/or the operator-provided additional/supplemental information that relates to given CT operating constraints to run simulation(s) to determine CT emission targets and operation parameters. In certain cases, a CT operator may directly provide, via the user interface, the CT emission targets and operation parameters based on the new operating state of the CT.

Based on at least the determined operation parameters, the controller <NUM> may perform emission control operations (block <NUM>). The emission control operations may be used to regulate certain gas concentrations and/or gas mass flows in the exhaust gases in compliance with the determined emission targets. Such operations may be performed by the controller <NUM> automatically or with certain instruction(s) provided by the CT operator during operations. Operation examples are provided below to impart some familiarity with the CT emission control operations.

For example, the controller <NUM> may perform an operation to control air supply to the compressor <NUM> (block <NUM>). For instance, when the CT <NUM> enters a low load operation, the controller <NUM> may utilize the one or more bleed valves <NUM> on the compressor <NUM> to adjust the degree of valve opening. In some embodiments, the CT <NUM> may include one or more compressors <NUM>. The controller <NUM> may partially open one or more bleed valves <NUM> in or between the one or more compressors <NUM> of the CT <NUM>. The adjustment of valve opening may cause the bleed valves <NUM> to open further to reduce the air flow rate, resulting in a higher fuel-to-air ratio that will increase the combustion temperature in the combustor <NUM>. As mentioned previously, increased combustion temperature may lower CO concentration in the exhaust gas <NUM>. As such, the CT may operate at the low load (e.g., lower than <NUM>% of CT full load) while meeting a CO emission target from the combustor <NUM> (e.g., a CO mass flow level below a predefined threshold at a low load operation).

Additionally, or alternatively, the controller <NUM> may perform a fuel supply management operation to increase the combustion temperature. That is, the controller <NUM> may perform an action to control fuel supply to the CT combustor (block <NUM>). For instance, when the CT enters a low load operation, the controller <NUM> may utilize the one or more fuel nozzles <NUM> in the combustor <NUM> to increase fuel injections to the combustor <NUM>. The increased fuel injection may increase the temperature of the combustion flame <NUM>, thereby lowering CO concentration in the exhaust gas <NUM>.

As the combustion temperature of the combustion flame <NUM> increases (e.g., after performing operations described in blocks <NUM> and <NUM>), the formation of NOx in the exhaust gas <NUM> may increase. To meet the NOx emission target(s) from the combustor <NUM>, the diluent injection system <NUM> may be utilized by the controller <NUM> to adjust diluent injection to the combustor <NUM> (block <NUM>). The diluent injection may include injecting a diluent (such as water or steam) into the combustor <NUM>. The diluent injection may be used to reduce the formation of NOx while maintaining an allowable range of CO concentration. For instance, the diluent may be used to reduce the NOx flow to a mass similar to that arriving at the SCR during high/full load operation of the CT <NUM>. Alternatively, the flow of diluent may be reduced to increase a combustion temperature in the combustor <NUM>, for example, by at least partially closing a diluent valve to reduce a diluent in the combustor <NUM>.

Additionally, or alternatively, the controller <NUM> may perform one or more operations to adjust the catalyst assembly <NUM> in the exhaust section <NUM> (block <NUM>). For example, the controller <NUM> may cause the catalyst assembly <NUM> to utilize one or more oxidation catalysts to treat specific emission(s) in the exhaust gas <NUM> to meet an overall emission target. Such oxidation catalysts may include a CO catalyst, a NOx catalyst, unburned hydrocarbon catalyst, and/or other suitable catalysts. In some embodiments, the catalyst assembly <NUM> may utilize a NOx catalyst to destroy NOx gases within the stream of exhaust gas <NUM>. In some embodiments, a CO catalyst may be used to reduce the CO gas concentration and/or mass flow within the stream of exhaust gas <NUM>. In certain embodiments, the controller <NUM> may cause the catalyst assembly <NUM> to selectively change the temperature of one or more components of the catalyst assembly <NUM> or inputs to the catalyst assembly <NUM> to increase catalyzation of the catalyst assembly <NUM>. For instance, the controller <NUM> may selectively change the temperature of components of the catalyst assembly <NUM> or its inputs (e.g., air, ammonia, or a mixture of air and ammonia) to compensate for increased emission gases during the partial or no load condition.

In some cases, the catalyst assembly <NUM> may include a selective catalytic reduction (SCR) system. For example, the SCR system may convert NOx with the aid of catalyst(s) (e.g., a metal-based oxide such as titanium oxide) into diatomic nitrogen (N<NUM>) and water (H<NUM>O). A gaseous reductant (e.g., ammonia or urea) may be added to the exhaust gas <NUM> and adsorbed onto corresponding catalyst(s) to treat emission gases of a first emission gas type (e.g., NOx gases). The exhaust gas <NUM> mixed with the gaseous reductant may enter a catalyst reactor (or chamber). Increasing the amount of reductant can dynamically increase catalyzation in the catalyst assembly. The gaseous reductant may react selectively with the NOx within a specific temperature range and in the presence of the corresponding catalyst(s). As such, the SCR system may control the NOx emissions in compliance with an output NOx emission target.

It should be noted that, while at least some of the operations described above are discussed as performed separately, the controller <NUM> may perform multiple operations, including at least a portion of the example operations described above and/or other suitable operations that may help to control CT emissions, sequentially, simultaneously, or a combination thereof. For instance, the controller <NUM> may utilize the bleed valves <NUM> to adjust the degree of valve opening to increase fuel-to-air ratio while also increasing a rate of injection of fuel (e.g., partially opening a fuel valve). Such combined operations may increase the combustion temperature more efficiently than using one operation alone. In some embodiments, certain operations may be performed in a sequence to balance specific gas emissions generated in different operations. For instance, with an increased combustion temperature, the formation of NOx in the exhaust gas <NUM> may increase. To compensate for the NOx increase in the exhaust gas <NUM>, an ammonia (NH<NUM>) injection may be used by the SCR system to reduce the NOx emission in the treated exhaust gas exiting from the exhaust section <NUM>.

During and/or after the emission control operations performed by the controller <NUM>, the controller <NUM> may utilize various sensing and monitoring devices to measure CT performance-related parameters including emissions and/or temperatures (block <NUM>). Such sensing and monitoring devices may be deployed among multiple CT components including the combustor <NUM> and the exhaust section <NUM>.

In some embodiments, the controller <NUM> may utilize the temperature sensors <NUM> deployed in the combustor <NUM> to measure the temperature of the combustion flame <NUM>. Additionally, the flame detectors <NUM> deployed in the combustor <NUM> may be used to detect the presence and the location of the combustion flame <NUM>. The temperature sensors <NUM> and flame detectors <NUM> may be distributed in different locations of the combustor <NUM>. Such distributed temperature and flame sensing may provide a detailed profile of the combustion flame <NUM> for enhanced combustion monitoring and controlling using at least one of the previously discussed control mechanisms.

In some embodiments, at the exhaust section <NUM>, the controller <NUM> may utilize one or more temperature sensors <NUM> to measure the temperature of the exhaust gas <NUM>. Further, emission sensors <NUM> may be used to measure the concentrations and/or mass flows of specific emission gases (e.g., CO and NOx). The temperature sensors <NUM> and emission sensors <NUM> may be distributed in different locations of the exhaust section <NUM>. For instance, some of the temperature sensors <NUM> and emission sensors <NUM> may be deployed before the exhaust gas <NUM> enters the catalyst assembly <NUM>, while other temperature sensors <NUM> and emission sensors <NUM> may be deployed after the exhaust gas <NUM> exits from the catalyst assembly <NUM> after being treated. Such distributed temperature and emission sensing may provide temperature and emission variations before and after the treatment provided by the catalyst assembly <NUM> (e.g., using the oxidation catalysts and/or SCR system).

The measured CT performance-related parameters (e.g., the concentrations and mass flows of specific emission gases including CO and NOx) may be analyzed by the controller <NUM>, via one or more processors <NUM>, to determine whether the performed operations (e.g., the blocks <NUM>, <NUM>, <NUM> and <NUM>) in response to the new operating state of the CT yield allowable levels of emission gases (e.g., CO and NOx concentrations and mass flows) that meet the CT emission targets (block <NUM>).

The measured CT performance-related parameters may also be sent to one or more monitoring devices to allow the CT operator to monitor CT performance (block <NUM>). The monitoring may be conducted by the CT operator locally (e.g., via a display panel on the controller <NUM>, a user interface on a computer communicatively linked to the controller <NUM> from an on-site CT control room, a Bluetooth device that is configured to receive the measured CT performance-related parameters, and the like), and/or remotely (e.g., via a smart phone or a virtual machine in a cloud that may access the measured CT performance-related parameters). This external monitoring may be used to fine-tune, repeat, and/or continue the emission controls operations <NUM>.

Additionally, or alternatively, the various sensing and monitoring devices to measure CT performance-related parameters may be fed back to the controller <NUM> to enable the controller <NUM> to dynamically determine emission targets based at least in part on the CT performance-related parameters. For example, <FIG> illustrates a flow diagram of an emission control process <NUM> that may be used to feedback the CT performance-related parameters. Specifically, the emission control process <NUM> is similar to the emission control process <NUM> except that the emission control process <NUM> includes sending the CT performance-related parameters back to the controller <NUM> (block <NUM>). That is, the controller <NUM>, the various controllable devices (e.g., the bleed valves <NUM>, the fuel nozzles <NUM>, the diluent injection system <NUM>, the catalyst assembly <NUM>, and the like), and the various sensing and monitoring devices (e.g., the fuel sensor <NUM>, the temperature sensors <NUM> and flame detectors <NUM> on the combustor <NUM>, the temperature sensors <NUM> and emission sensors <NUM> on the exhaust section <NUM>, and the like) may form a closed loop combustion turbine control system with feedbacks to dynamically determine the emission levels, relative to the emissions targets during operation of the CT <NUM>.

For example, feedback data sent to the controller <NUM> may include temperature measurements acquired by the temperature sensors <NUM> in the combustor <NUM> and/or by the temperature sensors <NUM> in the exhaust section <NUM>, combustion flame location detected by the flame detectors <NUM> in the combustor <NUM>, emission measurements acquired by the emission sensors <NUM> of the exhaust section <NUM>, and so on. Such feedback data may be analyzed by the controller <NUM>, via the one or more processors <NUM> and the memory <NUM>, to determine whether the performed operations <NUM> in response to the new operating state of the CT <NUM> yield allowable levels of emission gases (e.g., CO and NOx concentrations and mass flows). If certain emission gas levels exceed the CT emission targets, the controller <NUM>, via one or more processors <NUM> and memory <NUM>, may determine adjusted operation parameters to perform further operations <NUM> to control emissions in order to meet the CT emission targets.

In some embodiments, a model may be used by the controller <NUM> to determine the CT emission targets and operation parameters. The model may include a computer simulation model, physics-based model, an empirical model, and/or the like. Furthermore, the model may be stored in a non-transitory machine-readable medium (e.g., memory <NUM>) or a remote network (e.g., a cloud via suitable computing and communication devices, such as servers and routers).

For example, a simulation model may use at least a portion of the feedback data, certain operating parameters/settings related to the current operating state of CT, and/or the operator-provided additional/supplemental information that relates to given CT operating constraints to run simulations to determine whether certain implemented operation parameters should be adjusted to provide improved emission control to meet the CT emission targets. Moreover, such a model-based CT emission control mechanism, as part of the combustion turbine control system, may be implemented in real-time or offline manner depending on the CT operation environment.

The disclosed embodiments in preceding sections are related to combustion turbine control systems that may be used to operate CTs in partial or no load while meeting emission targets. Such combustion turbine control systems may enable the CTs to perform a variety of operations to control CT emissions through regulating certain gas concentrations and/or gas mass flows in the exhaust gases. As previously discussed, the variety of operations may include, but are not limited to, controlling fuel and/or diluent injection(s) to combustor(s) to control combustion temperature, controlling compressor bleed valve(s) to control the combustion temperature, controlling the catalyst assembly (e.g., the SCR system) to process exhaust gases before release into the environment, or a combination thereof. As previously noted, these operations may enable the CT to maintain somewhat consistent exhaust conditions even in a low load operation.

For instance, an increased exhaust gas temperature (e.g., through controlling fuel or diluent injections) at a low load operation may enable controlling NOx and/or CO exhaust conditions (e.g., mass flow) to approximate the NOx and/or CO exhaust conditions at a high load operation. As the NOx mass flow is used to determine a size for a reductant (e.g., NH<NUM>) injection system, maintaining NOx mass flow consistency between low loads and higher loads may enable the CT <NUM> to operate at a wider range of load levels while avoiding potentially costly modifications (i.e. reductant injection valve, manifold, vaporizer, and/or nozzle sizing) that otherwise may be necessary to allow for a wider variety of reductant flows. Similarly, because the CO mass flow and temperature are used to size the CO reduction catalyst within the SCR system, reducing CO concentration at low loads permits the size or design of the CO catalyst to be unchanged from SCRs that operate only with CTs running at relatively high loads (e.g., above <NUM>%). In other words, CTs <NUM> equipped with simpler reductant injection systems sized for higher reductant flows and SCR systems with smaller and/or more efficient CO catalyst may have lower operational cost than CTs with complex reductant injection systems (e.g. having wider reductant flow range) and SCR systems with larger and/or less efficient CO catalyst. With such approaches, wider ranges of operation (e.g., close to <NUM> MW) may be available without upsizing the SCR and/or modifying the reductant injection system.

With the preceding in mind, at partial or no load operation, the CT <NUM> may use the controller <NUM> to perform advanced operations. Simulations quantify a lower limit that the CT load can achieve while maintaining exhaust conditions similar to those of a standard CT at a baseline load. The baseline is the existing minimum load while remaining in emissions compliance. The simulation results demonstrate that the CT can be configured to operate at a lower minimum load (e.g., a minimum load equal to <NUM>% of the baseline) than the baseline without expensive SCR modifications.

During each simulation, the compressor variable bleed valves (VBVs) were biased open, and the NOx water injection was reduced from standard values until the objectives (exhaust temperature, NOx mass flow, and CO concentration) were met. Some simulation results are shown in <FIG>.

<FIG> is a plot of normalized power <NUM> versus ambient temperature <NUM> showing that enhanced CT controls may sustain a lower baseline <NUM>, which is a portion (e.g., <NUM>%) of the baseline power <NUM>, across the temperature range. Points along the plot of the unmodified baseline power level <NUM> are filled circles, while the points along the plot of the adjusted baseline power level <NUM> are open circles.

<FIG> is a plot of normalized exhaust temperature <NUM> versus ambient temperature <NUM>, which shows that the enhanced CT controls may keep exhaust temperature <NUM> approximately the same as baseline temperature <NUM>, while the enhanced CT controls operate the CT at a lower load (e.g., <NUM>% of the baseline power <NUM>).

<FIG> is a plot of normalized NOx flow <NUM> versus ambient temperature <NUM>, which shows that the enhanced CT controls may keep exhaust NOx mass flow rate <NUM> approximately equal to baseline NOx mass flow rate <NUM>, while the enhanced CT controls operate the CT at a lower load than the baseline power <NUM>.

<FIG> is a plot of normalized CO exhaust mass flow <NUM> versus ambient temperature <NUM>, which shows that the enhanced CT controls may keep exhaust CO mass flow <NUM> equal to or less than baseline CO mass flow <NUM>, while the enhanced CT controls operate the CT at a lower load than the baseline power <NUM>. The baseline NOx mass flow rate <NUM> and the baseline CO mass flow <NUM> may be components of the exhaust emissions profile of the CT <NUM> at a minimum load condition in which the combustion temperature is not increased. In other words, the exhaust emissions profile may include the mass flow and/or concentrations of various exhaust emissions gasses, such as NOx and CO.

Claim 1:
A method, comprising:
receiving an indication that a combustion turbine (<NUM>) is to operate in a partial or no load condition;
responsive to receiving the indication, operating the combustion turbine (<NUM>) in the partial or no load condition, thereby generating exhaust emissions; and
increasing a combustion temperature in the combustion turbine (<NUM>) in the partial or no load condition to increase a concentration of nitrous oxides (NOx) in the exhaust emissions and to reduce a concentration of carbon monoxide (CO) in the exhaust emissions while maintaining an exhaust gas temperature and an exhaust emissions profile of operating at a baseline load which is defined as a minimum load while remaining in emissions compliance without increasing the combustion temperature in the partial or no load condition,
characterized in that increasing the combustion temperature in the combustion turbine (<NUM>) in the partial or no load condition comprises at least one of:
at least partially reducing diluent flow into a combustor of the combustion turbine (<NUM>) by at least partially closing a diluent valve; or
at least partially opening one or more bleed valves (<NUM>) in a compressor (<NUM>) of the combustion turbine (<NUM>), or between compressors of the combustion turbine (<NUM>).