Indirect combustion type biomass gas turbine starting method

Abstract

The invention belongs to the technical field of gas turbine control and heat management, and relates to an indirect combustion type biomass gas turbine starting method, which comprises the following steps: acquisition, shafting traction, flow field establishment, heat invasion temperature equalization, wall temperature stabilization, ignition control, constraint over-limit, dynamic freezing, and first climbing and grid connection. According to the method, flow field establishment is judged by taking the key pneumatic quantity and the shafting rotating speed as criteria, the rapidity of starting regulation and control and the operation safety margin are considered, meanwhile, the wall temperature stability is judged by taking the wall temperature of the high-temperature heat exchanger as the criterion, and the problem of tube wall transient temperature difference surge caused by sudden change of a heat exchange coefficient in the flow establishment process is relieved; the wall temperature multi-dimensional constraint quantity is compared with a corresponding threshold value to achieve starting and stopping of dynamic freezing control and limited climbing of a fuel instruction, the unsteady state characteristic of biomass fuel combustion is adapted, transient thermal stress and local hot spot generation are restrained in time, and orderly regulation and control of the starting process and thermal safety protection of a high-temperature heat exchanger are achieved in the whole process.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine control and thermal management technology, and relates to a start-up method for an indirect combustion biomass gas turbine. Background Technology

[0002] EFGT, or indirect combustion gas turbine, is an important technological approach connecting solid fuels such as biomass and waste with clean power generation. Its core advantage lies in achieving physical isolation between the "combustion side" and the "working fluid side" through a high-temperature heat exchanger. The dusty and corrosive flue gas generated during combustion flows only through the external heat exchanger, while clean compressed air circulates independently as the turbine's working fluid. This significantly reduces the risk of damage to the compressor and turbine blades caused by ash deposition, high-temperature corrosion, and particulate erosion. This technology has been demonstrated in small-scale distributed energy stations, microgrids in remote areas, and industrial waste heat coupled power generation systems. Typical systems include boilers, high-temperature heat exchangers made of high-temperature resistant metal materials, compressors, and turbine units.

[0003] Currently, in the practical application of EFGT, the startup phase is a critical link in its operational reliability. Due to the unique properties of EFGT itself, with its multi-stage heat transfer links and high heat capacity heat exchange structure, significant thermo-mechanical coupling problems are easily triggered during startup. If these problems cannot be effectively controlled, they will directly affect the service life and operational safety of the equipment. To address the core issues in the startup phase, existing technologies have developed corresponding startup control strategies, which mainly include three points: First, a closed-loop fuel regulation method is adopted, using feedback quantities such as engine speed, turbine exhaust temperature, or turbine inlet working fluid temperature to achieve basic control of fuel supply; Second, to reduce operational instability caused by cold ignition or low-temperature heat exchange efficiency, a "preheat first, then increase speed" approach is adopted, that is, the heat exchanger is preheated to a certain extent before reaching a suitable temperature, and then the turbine speed is increased to establish a stable compressor flow rate; Third, limiting the upper limit of working fluid temperature, such as turbine inlet temperature, is used as a core safety protection condition, supplemented by ramp control of fuel supply and turbine speed to avoid safety hazards caused by sudden changes in operating conditions.

[0004] However, the existing start-up control strategies mentioned above still have many shortcomings when applied to the start-up conditions of EFGT, making it difficult to effectively solve the thermo-mechanical coupling problem during the start-up phase. Specific defects are as follows: First, the mismatch between thermal inertia and dynamic response causes feedback lag. Conventional closed-loop control cannot balance rapid regulation with operational safety margins, easily leading to abnormal increases in combustion-side temperature, thereby increasing the heat load risk of the heat exchanger and affecting its service life. Second, a sudden change in the heat transfer coefficient during flow establishment can cause a sharp increase in the transient temperature difference of the heat exchanger tube wall, generating adverse thermal stress impacts, thus increasing the risk of low-cycle fatigue of components, coating damage, and sealing failure at connection points. Third, the lack of an active control mechanism with wall temperature change rate and wall thickness direction temperature difference as core constraints makes it difficult to adapt to the unsteady-state characteristics of biomass fuel combustion, and it cannot promptly suppress the generation of transient thermal stress and local hot spots. Ultimately, this leads to a deterioration in the stress state of key components such as the heat exchanger tube bundle, tube sheet, seals, and connection structures, resulting in decreased equipment reliability and even serious problems such as leakage and performance degradation. Summary of the Invention

[0005] The purpose of this invention is to provide a startup method for an indirect combustion biomass gas turbine, which can achieve time-series matching between the establishment of the working fluid flow field and the heating of the thermal field during startup, and effectively constrain the wall temperature change rate and temperature gradient, which are closely related to transient thermal stress, thereby reducing the risk of thermal shock and fatigue of the heat exchanger and related structures while ensuring startup efficiency.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A startup method for an indirect combustion biomass gas turbine, applied to an indirect combustion biomass gas turbine system including a compressor, turbine, biomass boiler, and high-temperature heat exchanger, includes the following steps: Real-time data collection includes compressor outlet pressure, compressor loop flow rate, compressor pressure ratio, and hot and cold end temperatures of the high-temperature heat exchanger. Apply traction torque to the connecting shaft system between the compressor and the turbine, causing the compressor to accelerate with the shaft system and keeping the fuel command of the biomass boiler at zero; The collected compressor outlet pressure, compressor loop flow rate, and compressor pressure ratio are used as key aerodynamic quantities to form the stability criterion for flow field establishment. The shaft speed is used as the speed criterion for flow field establishment. If either of the two conditions is met, the flow field can be determined to be established. Under the premise of maintaining the flow field, hot immersion temperature equalization is carried out by using a low heat input method that does not cause a sudden rise in the hot end of the high-temperature heat exchanger without ignition. The hot end temperature and cold end temperature of the high-temperature heat exchanger are used as the wall temperature criterion. If the wall temperature criterion is valid, the wall temperature is determined to be stable. Under the premise of establishing the flow field and stabilizing the wall temperature, ignition control is performed to bring the biomass boiler into combustion state and gradually increase the fuel command with a restricted ramp strategy. At the same time, the hot and cold end temperatures of the high-temperature heat exchanger are continuously collected within the preset control cycle. The set of multi-dimensional wall temperature constraints is determined using the hot and cold end temperatures of the high-temperature heat exchanger. Any multi-dimensional wall temperature constraint is compared with the entry threshold and exit threshold. If the multi-dimensional wall temperature constraint is greater than the entry threshold, dynamic freeze control is entered to suppress the increase of fuel command. If all multi-dimensional wall temperature constraints are less than the exit threshold, dynamic freeze control is exited, and the fuel command continues to be increased for restricted ramping. When the grid connection conditions are met, grid connection operation is performed.

[0007] The invention is further characterized by: When collecting the hot and cold end temperatures of the high-temperature heat exchanger, multiple axial stations are symmetrically set at the hot and cold ends along the flow direction of the high-temperature heat exchanger. Multiple circumferential measuring points are symmetrically set at each axial station, and the temperatures of each axial station and each circumferential measuring point are collected respectively.

[0008] The conditions for the speed criterion to be met are that the shaft speed is greater than or equal to the minimum speed threshold and the state continues for a preset flow field establishment period. The conditions for the stability criterion to be met are that the relative fluctuation amplitude of the key aerodynamic quantity is less than or equal to the preset stability tolerance and the state continues for a preset flow field establishment period.

[0009] The conditions for establishing the wall temperature criterion are any one or a combination of the following: The first method is that within a continuous preset wall temperature stabilization period, the absolute value of the wall temperature change rate between the hot end and the cold end of the high-temperature heat exchanger is less than or equal to a preset wall temperature change rate threshold; The second method is that within a continuous preset wall temperature stabilization period, the difference between the wall temperature of the hot end and the cold end of the high-temperature heat exchanger in the axial or circumferential direction is less than or equal to a preset wall temperature spatial non-uniformity threshold.

[0010] The set of multidimensional constraints on wall temperature includes at least the constraint on the maximum rate of change of wall temperature, the constraint on the maximum through-wall gradient, the constraint on the maximum axial gradient, and the constraint on the maximum circumferential gradient.

[0011] If the multidimensional constraint of wall temperature is greater than the entry threshold, an over-limit judgment period needs to be continuously preset. If the multidimensional constraint of wall temperature is less than the exit threshold, a release judgment period needs to be continuously preset.

[0012] The preset release determination period is greater than or equal to the preset over-limit determination period.

[0013] The dynamic freeze control adopts any of the following methods or a combination thereof: the first method is to force the fuel command change rate to be zero, so that the fuel command remains unchanged; the second method is to force the fuel command change rate to be less than zero, so that the fuel command decreases slowly.

[0014] The grid connection conditions include at least the relative fluctuation amplitude of key aerodynamic quantities being less than or equal to the preset stability tolerance and this state being maintained for a preset flow field establishment period, the shaft rotation speed being greater than or equal to the minimum rotation speed threshold and being maintained for a preset flow field establishment period, and all wall temperature multidimensional constraints being less than the exit threshold and being maintained for a preset release determination period.

[0015] The indirect combustion biomass gas turbine start-up method of the present invention has the following advantages: This invention can collect real-time data on compressor outlet pressure, loop flow rate, pressure ratio, and hot and cold end temperatures of the high-temperature heat exchanger. By applying traction torque to the compressor-turbine connecting shaft system and maintaining the biomass boiler fuel command at zero, it uses key aerodynamic quantities and shaft speed as criteria to determine flow field establishment, balancing rapid start-up control with operational safety margins. Simultaneously, while maintaining flow field establishment, it employs non-ignition or low heat input methods for hot immersion temperature equalization, using the high-temperature heat exchanger wall temperature as a criterion to determine wall temperature stability. This mitigates the problem of sudden surges in tube wall temperature caused by abrupt changes in the heat transfer coefficient during flow establishment. Furthermore… After the flow field and wall temperature stability conditions are met, the biomass boiler is ignited and the fuel command is gradually increased using a restricted slope strategy. The wall temperature of the high-temperature heat exchanger is continuously collected and the set of multi-dimensional wall temperature constraints is determined. By comparing the multi-dimensional wall temperature constraints with the corresponding thresholds, the start-up and shutdown of dynamic freeze control and the restricted ramping of fuel commands are realized. This adapts to the unsteady characteristics of biomass fuel combustion and timely suppresses transient thermal stress and the generation of local hot spots. Finally, grid connection is completed. The entire start-up process is orderly regulated and the thermal safety protection of the high-temperature heat exchanger is achieved, ensuring the operational reliability of the indirect combustion biomass gas turbine during the start-up phase. Attached Figure Description

[0016] Figure 1 This is a flow chart of a typical indirect combustion biomass gas turbine system.

[0017] Figure 2 This is a schematic diagram of the process of the present invention.

[0018] Figure 3 This is a schematic diagram of the multidimensional constraint calculation and dynamic freezing control logic for wall temperature in this invention.

[0019] Figure label: 1. Air compressor, 2. Turbine, 3. Biomass boiler, 4. High-temperature heat exchanger. Detailed Implementation

[0020] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0021] like Figure 1 As shown, the existing indirect combustion biomass gas turbine system includes a compressor 1, a turbine 2, a biomass boiler 3, and a high-temperature heat exchanger 4. The system uses indirect combustion to achieve turbine work, that is: fuel is burned in the biomass boiler 3 to form high-temperature flue gas, which enters the hot-end channel of the high-temperature heat exchanger 4 as the hot-end working fluid; the compressed air output from the compressor 1 enters the cold-end channel of the high-temperature heat exchanger 4 as the cold-end working fluid. Indirect heat exchange is achieved between the hot-end flue gas and the cold-end compressed air through the high-temperature heat exchanger 4, thereby heating the compressed air before it enters the turbine 2 to expand and do work. Since the temperature rise of the cold end (compressed air) of the high-temperature heat exchanger 4 is relatively slow while that of the hot end (combustion flue gas) is relatively fast, the system is prone to a significant increase in the temperature difference and temperature gradient of the heat exchanger wall during startup. Therefore, in the subsequent implementation of the method, constraints and controls will be implemented around the wall temperature gradient and its rate of change.

[0022] The indirect combustion biomass gas turbine system also includes actuators, which at least include: a boiler fuel supply actuator (corresponding to fuel mass flow rate or equivalent fuel command) and a shaft traction actuator (e.g., generator / motor torque control). In subsequent embodiments, the control cycle Δ t The wall temperature sequence is collected and processed, and fuel commands and / or torque commands are generated accordingly to achieve limited temperature rise and protection control during the start-up process.

[0023] like Figure 1 , Figure 2 As shown, the present invention provides a starting method for an indirect combustion biomass gas turbine, applied to the above-mentioned system, comprising the following steps: The outlet pressure of compressor 1, the loop flow rate of compressor 1, the pressure ratio of compressor 1, and the hot and cold end temperatures of high-temperature heat exchanger 4 are collected in real time.

[0024] A traction torque is applied to the connecting shaft system of compressor 1 and turbine 2, causing compressor 1 to accelerate with the shaft system and keeping the fuel command of biomass boiler 3 at zero.

[0025] The collected outlet pressure of compressor 1, the loop flow rate of compressor 1, and the pressure ratio of compressor 1 are used as key aerodynamic quantities to form the stability criterion for flow field establishment. The shaft speed is used as the speed criterion for flow field establishment. If either of the two conditions is met, the flow field can be determined to be established.

[0026] Under the premise of maintaining the flow field, the hot immersion temperature is uniformly measured by using a low heat input method that does not cause a sudden rise in the hot end of the high-temperature heat exchanger 4 without ignition. The hot end temperature and cold end temperature of the high-temperature heat exchanger 4 are used as the wall temperature criterion. If the wall temperature criterion is valid, the wall temperature is determined to be stable.

[0027] Under the premise of satisfying the flow field establishment and wall temperature stability, ignition control is performed to put the biomass boiler 3 into combustion state and gradually increase the fuel command with a restricted slope strategy. At the same time, the hot end temperature and cold end temperature of the high-temperature heat exchanger 4 are continuously collected within the preset control cycle. The set of multi-dimensional wall temperature constraints is determined using the hot end temperature and cold end temperature of the high-temperature heat exchanger 4. Any multi-dimensional wall temperature constraint is compared with the entry threshold and exit threshold. If the multi-dimensional wall temperature constraint is greater than the entry threshold, dynamic freeze control is entered to suppress the increase of fuel command. If all multi-dimensional wall temperature constraints are less than the exit threshold, dynamic freeze control is exited and the fuel command continues to be increased for restricted ramping. When the grid connection conditions are met, grid connection operation is performed.

[0028] In summary, this invention can collect real-time data on compressor 1 outlet pressure, loop flow rate, pressure ratio, and hot and cold end temperatures of high-temperature heat exchanger 4. By applying traction torque to the shaft connecting compressor 1 and turbine 2 while keeping the fuel command of biomass boiler 3 at zero, the flow field is established using key aerodynamic quantities and shaft speed as criteria. This approach balances the speed of start-up control with operational safety margins. Simultaneously, while maintaining the established flow field, hot immersion homogenization is performed using no-ignition or low-heat-input methods, with the high-temperature heat exchanger wall temperature used as a criterion to determine wall temperature stability. This mitigates the problem of sudden surges in tube wall temperature caused by abrupt changes in the heat transfer coefficient during flow establishment. Furthermore, after satisfying the flow field and wall temperature stability conditions, the biomass boiler is ignited and fuel commands are gradually increased using a restricted slope strategy. The high-temperature heat exchanger wall temperature is continuously collected and the set of multi-dimensional wall temperature constraints is determined. By comparing the multi-dimensional wall temperature constraints with the corresponding thresholds, the start-up and shutdown of dynamic freeze control and the restricted ramping of fuel commands are realized. This adapts to the unsteady characteristics of biomass fuel combustion and timely suppresses transient thermal stress and local hot spots, ultimately completing grid connection. The entire startup process achieves orderly regulation and thermal safety protection of the high-temperature heat exchanger, ensuring the operational reliability of the indirect combustion biomass gas turbine during the startup phase.

[0029] When applying traction torque to the connecting shaft system of compressor 1 and turbine 2, the generator / motor device is controlled to enter electric traction mode, and traction torque is applied to the shaft system. Thus, without introducing combustion heat load, the compressor 1 establishes stable loop flow and pressure ratio conditions through shaft traction, providing the necessary aerodynamic basis for subsequent hot soaking homogenization and ignition combustion.

[0030] In this process, under the premise of maintaining the flow field, a low heat input method that does not cause a sudden rise in the hot end of the high-temperature heat exchanger 4 is adopted for heat immersion temperature equalization. For example, the biomass boiler 3 is in a preheating / insulation state but does not form a significant high-temperature flue gas impact, or the effective heat load entering the hot side of the heat exchanger is controlled by bypass and dilution methods that are permitted by the project. At this stage, the principle is still to avoid rapid temperature rise at the hot end of the high-temperature heat exchanger 4, so that the cold end and wall temperature of the high-temperature heat exchanger 4 change slowly, thereby reducing the risk of wall penetration temperature difference and thermal shock during subsequent ignition and heating, and making the wall temperature distribution enter a controllable range.

[0031] Among them, under the premise of satisfying the establishment of the flow field and the stability of the wall temperature, ignition control is carried out to bring the biomass boiler 3 into the combustion state and gradually increase the fuel command with a restricted slope strategy. In order to avoid the sudden rise of the hot end temperature of the high-temperature heat exchanger 4, the fuel command adopts a restricted slope strategy to gradually increase, and the upper limit of the initial slope is set according to the system's allowable heat load change capability.

[0032] Among them, the set of multidimensional wall temperature constraints is determined by using the hot end temperature and cold end temperature of the high-temperature heat exchanger 4. When comparing any multidimensional wall temperature constraint with the entry threshold and exit threshold, the constraint over-limit judgment is adopted, that is, the "continuous over-limit" rule suppresses misjudgment caused by noise or transient disturbance.

[0033] To achieve the startup control of the subsequent "hot immersion temperature equalization - wall temperature multi-dimensional constraint - dynamic freezing", when collecting the hot end temperature and cold end temperature of the high-temperature heat exchanger 4, multiple axial stations are symmetrically set along the flow direction of the high-temperature heat exchanger 4 at the hot end and cold end respectively. Each axial station is symmetrically set with multiple circumferential measuring points, and the temperature of each axial station and each circumferential measuring point is collected respectively. Preferably, it can be configured as 3 axial stations (e.g., the hot end / cold end inlet area, the hot end / cold end middle area, and the hot end / cold end outlet area) and each axial station is configured with 4 circumferential side points (e.g., up, down, left, and right), and each side point is equipped with a temperature sensor.

[0034] Among them, the condition for the speed criterion to be valid is the shaft speed. n ≥Minimum speed threshold n min Furthermore, this state continues for a preset flow field establishment period. N f The stability criterion is valid when the relative fluctuation amplitude of the critical aerodynamic quantity is less than or equal to the preset stability tolerance. εf Furthermore, this state continues for a preset flow field establishment period. N f Preferably, the flow field can be determined by either or a combination of the rotational speed criterion and the stability criterion.

[0035] The conditions for establishing the wall temperature criterion can be any one or a combination of the following: The first method is that the wall temperature stabilizes within a continuous preset period. N s Inside, the absolute value of the wall temperature change rate between the hot and cold ends of the high-temperature heat exchanger 4 is less than or equal to the preset wall temperature change rate threshold. R s (Unit: temperature / time), i.e., |d T / d t |≤ R s The second method involves continuously stabilizing the wall temperature over a preset period. N s Inside, the difference in wall temperature between the hot and cold ends of the high-temperature heat exchanger 4 in the axial or circumferential direction is less than or equal to the preset wall temperature spatial non-uniformity threshold Δ. T The above criteria can be adjusted based on the heat exchanger structure, the allowable thermal stress margin of the materials, and engineering experience.

[0036] Among them, the set of multidimensional constraints on wall temperature includes at least the constraint on the maximum rate of change of wall temperature, the constraint on the maximum wall penetration gradient, the constraint on the maximum axial gradient, and the constraint on the maximum circumferential gradient.

[0037] like Figure 2 As shown, the entry threshold is used to determine when a risk has entered, and the exit threshold is used to determine when a risk has been eliminated. If the multidimensional constraint of the wall temperature exceeds the entry threshold, an over-limit determination period needs to be continuously preset. N h If the constraint exceeds the limit, it is determined as "yes". When the multidimensional constraint values ​​of wall temperature are all less than the exit threshold, the release judgment period needs to be continuously preset. N r If the risk is deemed resolved, the dynamic freeze is lifted and the restricted ramping is resumed, gradually increasing the ramp rate according to the preset ramping strategy. m f This is to achieve system temperature increase and speed / power increase.

[0038] Among them, the preset release determination period N r Greater than or equal to the preset over-limit judgment period N h .

[0039] The dynamic freeze control adopts any one or a combination of the following methods: the first method is to force the change rate of fuel command. Zero, making the fuel command mf The second approach is to keep it unchanged; the third approach is to enforce the change rate of the fuel directive. Less than zero, triggers fuel command m f The temperature is gradually reduced, thereby suppressing the further expansion of the wall temperature change rate and temperature difference of the high-temperature heat exchanger 4.

[0040] Among them, the grid connection conditions include at least that the relative fluctuation amplitude of the key aerodynamic quantities is less than or equal to the preset stability tolerance. ε f Furthermore, this state continues for a preset flow field establishment period. N f , n ≥Minimum speed threshold n min Furthermore, this state continues for a preset flow field establishment period. N f And all wall temperature multidimensional constraints are less than the exit threshold and the preset release judgment period continues. N r .

[0041] like Figure 3 As shown, determining the set of multidimensional constraint quantities for wall temperature using the hot and cold end temperatures of a high-temperature heat exchanger involves the following steps: S1. Outlier removal and limiting.

[0042] For each measuring point on the hot and cold ends of the high-temperature heat exchanger In the Periodically obtain raw samples Then, an anomaly jump determination is performed. Preferably, if the following formula is satisfied, the sample is determined to be an anomaly: .

[0043] In the formula, For the first The measuring point at the ... The original sampling temperature value for each cycle, This is the physically achievable temperature jump threshold, used to determine whether the temperature jump within a single cycle exceeds the physically possible range. Indicates the measuring point. .

[0044] When an outlier is identified, it is preferable to use "keeping the previous period's value" or "neighborhood interpolation" to replace the outlier. For example, we can let... Alternatively, if nearby measurement points are available, neighborhood interpolation can be used to improve robustness. It can be adjusted according to the sensor sampling frequency, metal thermal inertia, and the possible maximum rate of change of thermal load.

[0045] S2, causal low-pass filtering, yields .

[0046] After S1 processing Causal low-pass filtering is performed to reduce the risk of measurement noise falsely triggering subsequent "maximum-value-type constraint quantities". First-order causal filtering is preferred.

[0047] .

[0048] in, for Temperature value after anomaly handling and causal low-pass filtering. , This is the filtering time constant. The settings can be tuned based on the typical thermal inertia timescale of the sensor noise level and the heat exchanger wall temperature. In another alternative implementation, a higher-order causal filter or moving average filter can also be used, but the filter should be causal to meet the requirements of online real-time calculation.

[0049] S3. Calculate the wall temperature change rate at each measuring point and further filter to obtain... .

[0050] Based on the filtered temperature sequence Calculate the discrete wall temperature change rate: .

[0051] In the formula, For the first The measuring point is at the 1st Estimated rate of change of wall temperature over the period, To control the periodic time interval.

[0052] To further suppress the amplification effect of differential operations on high-frequency noise, it is preferable to... Perform a causal low-pass filter of the same form as S2 to obtain .For example:

[0053] .

[0054] In the formula, To Further causal low-pass rate of change (used to suppress false triggering caused by noise). , The filtering time constant is It can be tuned the same as or independently of S2.

[0055] S4, Maximum wall temperature change rate constraint (Hard constraint 1).

[0056] In the For the period, the absolute value of the rate of change of all measuring points is taken as the maximum to construct the constraint quantity for the maximum rate of change of wall temperature: .

[0057] In the formula, This is the constraint for the maximum wall temperature change rate. This is used to characterize the risk of the maximum heating / cooling rate of the heat exchanger wall temperature in the current cycle, and can subsequently be compared with a preset threshold as one of the criteria for constraint triggering. To Further causal low-pass rate of change, k Indicates the discrete control cycle number. Indicates the measuring point. .

[0058] S5. Calculation of wall-penetrating temperature difference and wall-penetrating gradient (for paired points in the wall thickness direction) (intermediate quantity of hard constraint quantity 2).

[0059] For each set of paired measuring points in the wall thickness direction Its hot end measuring point is The cold end measuring point is Calculate the temperature difference through the wall:

[0060] .

[0061] And according to the effective wall thickness Convert the gradient across the wall: .

[0062] In the formula, For the temperature difference through the wall, For the wall gradient, The temperature value after hot-end anomaly handling and causal low-pass filtering. The temperature value after cold-end anomaly handling and causal low-pass filtering. The equivalent heat transfer wall thickness of the corresponding cross section or the effective thickness after engineering correction can be taken.

[0063] S6, Maximum Through-Wall Gradient Constraint (Hard constraint 2).

[0064] In the k-th period, the maximum gradient across the wall is obtained by maximizing the gradient across all pairs of points: .

[0065] In the formula, The maximum through-wall gradient constraint is used to characterize the worst-case scenario of thermal mismatch in the wall thickness direction and reflects the risk level of through-wall thermal stress.

[0066] S7. Calculate the extreme value envelope of the station to obtain the upper / lower bound of the temperature represented by the station.

[0067] To construct the axial and circumferential non-uniformity constraints, it is preferable to consider the following for each axial station. Construct the extreme value envelope of the station. For axial stations. Its circumferential measurement point set is ,definition:

[0068] .

[0069] .

[0070] In the formula, This is an axial positioning. , The purpose of using the extreme value envelope for the circumferential measurement point set is to improve the ability to capture local hot spots and local cold spots, and to avoid the loss of extreme value information caused by using only the average value.

[0071] S8. Calculate the axial temperature difference and axial gradient, and take the maximum value (hard constraint 3).

[0072] For adjacent stations (in The upper bound of the "maximum possible axial temperature difference" is constructed based on the extreme value envelope of the station. Preferred definition:

[0073] .

[0074] And convert it to axial gradient: .

[0075] Taking the maximum value yields the maximum axial gradient constraint: .

[0076] In the formula, To maximize the axial temperature difference, For axial gradient, The maximum axial gradient constraint is used to characterize the most unfavorable temperature non-uniformity and thermal mismatch risk along the flow direction of the heat exchanger.

[0077] S9. Calculate the circumferential temperature difference and circumferential gradient, and take the maximum value (hard constraint 4).

[0078] For each station Calculate the circumferential temperature difference at the same station based on the station's extreme value envelope: .

[0079] And according to the equivalent radius With effective angle difference Calculate the circumferential gradient. Preferred definition:

[0080] .

[0081] In the formula, The circumferential temperature difference at the same station For the circumferential gradient at the same station, For the first The equivalent radius corresponding to each station can be taken as the equivalent radius of the tube bundle or shell of the high-temperature heat exchanger 4 corresponding to that station. For the effective angle difference, The circumferential gradient constraint can be defined based on the angular distribution of the station's measuring points, for example, by taking the maximum angular span or the equivalent angular difference corresponding to the minimum angular interval between adjacent measuring points. The specific determination depends on the sensor arrangement. Then, the maximum value is taken to obtain the maximum circumferential gradient constraint.

[0082] .

[0083] In the formula, The maximum circumferential gradient constraint is used to characterize the most unfavorable non-uniformity risk caused by circumferential hot spots.

[0084] Through the steps S1 to S9 described above, in each control cycle Output wall temperature multidimensional constraint set In subsequent implementations, this set can be compared with the corresponding thresholds and combined with the continuous over-limit criterion to generate a control decision for dynamic freezing or restricted ramping.

[0085] It should be noted that the specific form of the above-mentioned constraint quantities can be equivalently replaced without departing from the overall idea of ​​this invention. For example, the wall-penetrating constraint can also be the wall-penetrating temperature difference. Instead of gradient form; axial and circumferential constraints can also be converted between "temperature difference" and "gradient" representations; in addition to the extreme value envelope, the station-represented temperature can also use the percentile envelope or a validated robust extreme value estimate to balance noise and extreme value capture capability. Furthermore, the number of sensors... Number of stations Number of paired points as well as , The definition can be adjusted according to changes in engineering structure and layout, and this patent is not limited to it.

[0086] Specifically, any multidimensional wall temperature constraint is compared with the entry threshold and the exit threshold. If the multidimensional wall temperature constraint is greater than the entry threshold, dynamic freeze control is initiated to suppress the increase of fuel commands. If all multidimensional wall temperature constraints are less than the exit threshold, dynamic freeze control is exited, and fuel commands continue to be increased. During restricted ramping, the specific steps are as follows: For ease of description, in addition to the symbols defined in "General Symbols and Terminology", the following additional definitions are provided: 1) , , , They represent the first time. The wall temperature multidimensional constraint quantity obtained from periodic calculation, The constraint for the maximum wall temperature change rate, For the maximum through-wall gradient constraint, For the maximum axial gradient constraint, This is the maximum circumferential gradient constraint; its calculation method is described above.

[0087] 2) For any constraint quantity ( Desirable , , , (any one of the items), define its entry threshold. With exit threshold ,in To form a hysteresis band.

[0088] 3) Indicates the number of periods for determining continuous over-limit conditions; This indicates the number of periods for lifting the judgment.

[0089] 4) F[k] represents the frozen state flag. F[k]=1 indicates that it is in a dynamic frozen state, and F[k]=0 indicates that it is in a non-frozen state (normal restricted climbing state).

[0090] 5) This indicates the maximum allowable fuel rise slope (positive value) in a non-frozen state. This represents the upper limit (positive value) of the allowable fuel reduction slope when active load reduction is required. Under frozen conditions, it is generally required that fuel consumption not increase further, which can be expressed as... .

[0091] The following is in conjunction with the appendix Figure 3 The logic shown illustrates the steps of the dynamic freeze control method. For ease of understanding... Figure 3 Correspondingly, the following mainly describes the control decision and output generation of S10 to S12, and explains their cyclic execution mode within the control cycle.

[0092] S10, Threshold setting and hysteresis design.

[0093] For each of the multidimensional constraints on wall temperature, entry and exit thresholds are set to form a hysteresis band, thereby suppressing jittery switching near the threshold. Preferably, the threshold group can be expressed as:

[0094] (1) Threshold for maximum wall temperature change rate: , ,and ; (2) Maximum wall penetration gradient threshold: , ,and ; (3) Maximum axial gradient threshold: , ,and ; (4) Maximum circumferential gradient threshold: , ,and .

[0095] The aforementioned threshold can be adjusted based on the allowable thermal stress margin of the heat exchanger structure and materials, the allowable start-up heating rate, and the engineering safety margin. In another alternative embodiment, the threshold can also be set as a function of operating conditions (e.g., varying with the average wall temperature level or rotational speed), but the exit threshold should still be kept lower than the entry threshold to create hysteresis.

[0096] S11, Continuous over-limit judgment and freeze flag generation.

[0097] In each control cycle k First, the set of multidimensional wall temperature constraint quantities is read or calculated, and a determination is made as to whether the limit is exceeded. To avoid false triggering caused by instantaneous noise or short-term disturbances, a continuous limit-exceeding determination rule is adopted. Preferably, it can be implemented as follows:

[0098] (1) Determine the continuous over-limit judgment before entering the freeze state, and define the logic condition for entering the over-limit state. A tendency to enter an overlimit state is considered to exist when any of the following conditions are met: A) .

[0099] B) .

[0100] C) .

[0101] D) .

[0102] when Continuous true and persistent If the cycle is repeated, then set the freeze flag. Optionally, in the engineering implementation, a counter can be set for each type of constraint, and the condition "when any counter reaches..." can be set. "Freeze" or set a unified counter for determining "any continuous over-limit"; both are equivalent in control effect and do not deviate from the idea of ​​this invention.

[0103] (2) Determination of continuous decline after unfreezing: In the frozen state, to avoid premature unfreezing leading to another over-limit, a retracement threshold and a continuous decline determination are used. Define the unfreezing logic conditions. The risk is considered to be "within a resolvable range" when all of the following conditions are met:

[0104] A) .

[0105] B) .

[0106] C) .

[0107] D) .

[0108] when Continuous true and persistent If the cycle is repeated, then set the freeze flag. Exit dynamic freezing and restore to the unfrozen state. If in frozen state... If not continuously satisfied, then maintain. .

[0109] It should be noted that, and They can be the same or different. Preferably, Can be greater than or equal to This is to improve the conservatism of the lifting decision and further reduce the frequent back-and-forth of "freezing-lifting-refreezing".

[0110] S12, Fuel Command Slope Selection and Dynamic Freeze Execution.

[0111] In each control cycle k According to the freeze indicator F [ k The rate of change of the fuel command is selected and constrained to generate the final fuel command. Preferably, the control output generation can be implemented according to the following rules:

[0112] (1) Non-frozen state ( Limited ramp output When no freeze is triggered, the fuel command increases according to a limited ramp strategy to achieve start-up warm-up and power increase, but its ramp rate should be limited. Preferably, it can be set as follows: .

[0113] And update in discrete form: .

[0114] in The target value can be provided by the upper-level climbing target, and then limited by the limiter. Within the range. If the upper-level objective requires a reduction in fuel, then it is permitted. It is negative, and its decrease does not exceed This is to avoid causing excessively rapid disturbances to combustion stability or hot-end temperature.

[0115] (2) Frozen state ( F [ k =1): Fuel slope freeze / suppression output. Once freeze is triggered, the fuel command is no longer allowed to increase to prevent further increases in wall temperature risk. Preferably, any one or a combination of the following methods can be used:

[0116] A) Slope Freeze: Forced Order ,thereby .

[0117] B) Suppressing the rise: Forced satisfaction ,thereby No increase, and allow for a slow decline if necessary to accelerate the risk recovery.

[0118] C) Discrete limiting implementation: Directly set... .

[0119] in The initial fuel command is given for upper-level restricted climbing or power control; by taking the minimum value, it can be ensured that the fuel does not increase during freezing.

[0120] The above freezing strategy can be selected based on the boiler combustion stability and system response characteristics. For scenarios that are more sensitive to combustion stability, slope freezing (A) is preferred; for scenarios that allow for a moderate drop to quickly eliminate risks, suppression of the rise or setting a small negative slope lower limit during freezing is preferred to achieve a gentle load reduction.

[0121] (3) Smooth recovery after freeze is lifted, when S11 determines to exit freeze ( F [ k When changing from 1 to 0, the preferred pair is... A gradual recovery or a smooth transition in fuel commands can be implemented to avoid a sudden, excessively rapid increase in the release rate, which could trigger a re-triggering. Optionally, this can be done before the release. Within a certain period, the upper limit of the upward slope will gradually recover from a smaller value to a normal value, among which... To smooth the recovery cycle number.

[0122] Through steps S10 to S12 above, the dynamic freeze control method completes the following closed loop in each control cycle: reading constraint quantities → generating a freeze flag based on hysteresis and continuity determination → selecting the fuel slope and updating the fuel command according to the freeze flag. Therefore, when the multidimensional wall temperature constraint quantities continuously exceed limits, the system can automatically enter freeze mode to limit the growth of thermal risk; when the constraint quantities fall back and stabilize, it automatically defreezes and resumes the restricted ramp-up, thereby improving the heat exchanger's thermal safety and control stability while ensuring startup efficiency.

[0123] It should be noted that the above dynamic freeze control method can be applied not only to fuel mass flow commands. It can also be applied equivalently to control quantities related to fuel supply (such as fuel valve opening commands, feeder speed commands, or equivalent heat load commands), simply by... Simply replace it with the appropriate control variable while maintaining the constraint principle of "no increase when frozen". Additionally, the freeze flag... F It can also be used in conjunction with other control measures, such as limiting the temperature rise target, limiting the rate of temperature rise at the boiler hot end outlet, or limiting the loading rate before grid connection; however, the above-mentioned linkage is optional and does not constitute a limitation of the present invention.

[0124] The following are other advantages of the indirect combustion biomass gas turbine start-up method of the present invention: This invention achieves controlled matching of heat input and flow rate increase during the startup phase by coordinating the working fluid flow field establishment with the thermal field temperature rise during the startup process, and by limiting key constraints such as wall temperature change rate, wall-to-wall temperature difference, and temperature non-uniformity that are directly related to transient thermal stress. This reduces the risk of thermal shock and low-cycle fatigue of the heat exchanger and its connection / sealing structure, suppresses structural reliability problems caused by local overheating or rapid cooling, and improves the stability and controllability of the startup process while meeting safety constraints.

[0125] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A method for starting an indirect combustion biomass gas turbine, characterized in that, For indirect combustion biomass gas turbine systems that include compressors, turbines, biomass boilers, and high-temperature heat exchangers, the following steps are included: Real-time data collection includes compressor outlet pressure, compressor loop flow rate, compressor pressure ratio, and hot and cold end temperatures of the high-temperature heat exchanger. Apply traction torque to the connecting shaft system between the compressor and the turbine, causing the compressor to accelerate with the shaft system and keeping the fuel command of the biomass boiler at zero; The collected compressor outlet pressure, compressor loop flow rate, and compressor pressure ratio are used as key aerodynamic quantities to form the stability criterion for flow field establishment. The shaft speed is used as the speed criterion for flow field establishment. If either of the two conditions is met, the flow field can be determined to be established. Under the premise of maintaining the flow field, hot immersion temperature equalization is carried out by using a low heat input method that does not cause a sudden rise in the hot end of the high-temperature heat exchanger without ignition. The hot end temperature and cold end temperature of the high-temperature heat exchanger are used as the wall temperature criterion. If the wall temperature criterion is valid, the wall temperature is determined to be stable. Under the premise of establishing the flow field and stabilizing the wall temperature, ignition control is performed to bring the biomass boiler into combustion state and gradually increase the fuel command with a restricted ramp strategy. At the same time, the hot and cold end temperatures of the high-temperature heat exchanger are continuously collected within the preset control cycle. The set of multi-dimensional wall temperature constraints is determined using the hot and cold end temperatures of the high-temperature heat exchanger. Any multi-dimensional wall temperature constraint is compared with the entry threshold and exit threshold. If the multi-dimensional wall temperature constraint is greater than the entry threshold, dynamic freeze control is entered to suppress the increase of fuel command. If all multi-dimensional wall temperature constraints are less than the exit threshold, dynamic freeze control is exited, and the fuel command continues to be increased for restricted ramping. When the grid connection conditions are met, grid connection operation is performed.

2. The method for starting an indirect combustion biomass gas turbine according to claim 1, characterized in that, When collecting the hot end temperature and cold end temperature of the high-temperature heat exchanger, multiple axial stations are symmetrically set at the hot end and cold end along the flow direction of the high-temperature heat exchanger. Multiple circumferential measuring points are symmetrically set at each axial station, and the temperature of each axial station and each circumferential measuring point is collected respectively.

3. The method for starting an indirect combustion biomass gas turbine according to claim 1, characterized in that, The condition for the speed criterion to be met is that the shaft speed is greater than or equal to the minimum speed threshold and this state continues for a preset flow field establishment period. The condition for the stability criterion to be met is that the relative fluctuation amplitude of the key aerodynamic quantity is less than or equal to the preset stability tolerance and this state continues for a preset flow field establishment period.

4. The starting method for an indirect combustion biomass gas turbine according to claim 1, characterized in that, The conditions for establishing the wall temperature criterion are any one or a combination of the following: The first method is that within a continuous preset wall temperature stabilization period, the absolute value of the wall temperature change rate between the hot end and the cold end of the high-temperature heat exchanger is less than or equal to a preset wall temperature change rate threshold; The second method is that within a continuous preset wall temperature stabilization period, the difference between the wall temperature of the hot end and the cold end of the high-temperature heat exchanger in the axial or circumferential direction is less than or equal to a preset wall temperature spatial non-uniformity threshold.

5. The method for starting an indirect combustion biomass gas turbine according to claim 1, characterized in that, The set of multidimensional constraints for wall temperature includes at least the constraint for maximum wall temperature change rate, the constraint for maximum wall penetration gradient, the constraint for maximum axial gradient, and the constraint for maximum circumferential gradient.

6. The starting method for an indirect combustion biomass gas turbine according to claim 1, characterized in that, If the multidimensional constraint of wall temperature is greater than the entry threshold, the over-limit judgment period needs to be continuously preset. When the multidimensional constraint of wall temperature is less than the exit threshold, the release judgment period needs to be continuously preset.

7. The starting method for an indirect combustion biomass gas turbine according to claim 1, characterized in that, The preset release determination period is greater than or equal to the preset over-limit determination period.

8. The starting method for an indirect combustion biomass gas turbine according to claim 1, characterized in that, The dynamic freeze control adopts any of the following methods or a combination thereof: the first method is to force the fuel command change rate to be zero, so that the fuel command remains unchanged; the second method is to force the fuel command change rate to be less than zero, so that the fuel command decreases slowly.

9. The starting method for an indirect combustion biomass gas turbine according to claim 1, characterized in that, The grid connection conditions include at least the relative fluctuation amplitude of key aerodynamic quantities being less than or equal to a preset stability tolerance and this state being maintained for a preset flow field establishment period, the shaft rotation speed being greater than or equal to a minimum rotation speed threshold and being maintained for a preset flow field establishment period, and all wall temperature multidimensional constraints being less than an exit threshold and being maintained for a preset release determination period.

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