Method and system for determining flue gas turbine stage number in flue gas turbine

Abstract

The invention discloses a method and system for determining the flue gas turbine stage number in a flue gas turbine, and belongs to the field of catalytic cracking waste heat energy recovery, the turbine pressure ratio, the inlet temperature and the corresponding flue gas turbine stage number of the flue gas turbine are obtained, and each turbine pressure ratio, the inlet temperature and the flue gas turbine stage number form a data set; all the turbine pressure ratios and the corresponding inlet temperatures are utilized to fit a relational expression Q for calculating the inlet temperatures through the turbine pressure ratios, and then the inlet temperatures and the flue gas turbine series in each data set are combined to fit a corresponding relation between a criterion value Np and the flue gas turbine series; the criterion value Np is determined according to the turbine pressure ratio and the inlet temperature of the flue gas turbine, the corresponding flue gas turbine stage number is determined according to the corresponding relation between the criterion value Np and the flue gas turbine stage number, and the efficiency and reliability of the flue gas turbine are improved on the premise that the overall pressure and temperature performance index requirements of a flue gas turbine unit are met.

Description

Technical Field

[0001] The invention belongs to the field of catalytic cracking waste heat energy recovery, and in particular relates to a method and a system for determining the number of flue gas turbine stages in a flue gas turbine. Background Art

[0002] The catalytic cracking waste heat energy recovery unit of petrochemical industry is a key equipment in the oil refining industry. It plays an important role in the safe operation of the unit and energy saving and consumption reduction. The catalytic cracking unit will produce high-temperature flue gas during operation, which contains a large amount of energy. The energy recovery unit can recover the energy in the high-temperature flue gas and convert it into mechanical energy or electrical energy, thereby achieving the purpose of energy saving and consumption reduction. At present, the flue gas turbine widely used in the catalytic cracking waste heat energy recovery unit of petrochemical industry is the core device of the entire unit. After the high-temperature flue gas enters the flue gas turbine, part of the heat energy of the flue gas flow passing through the flue gas turbine turbine can be converted into kinetic energy, driving the blades of the flue gas turbine to rotate, and then driving the gearbox and steam turbine to rotate, achieving the effect of energy recovery. During the rotation process, the smoke turbine will drive the generator to generate electricity or provide power for other equipment.

[0003] According to the work capacity of the flue gas turbine, turbines are generally divided into single-stage turbines and two-stage turbines. Single-stage turbines have a simple structure and relatively low manufacturing costs, but the power they can generate is limited; if more work is required, two-stage turbines can only be used, and the efficiency is also improved accordingly. As the work done increases, the increase in the number of turbine stages will also bring some negative effects, which will cause additional increase in flow losses due to the increase in stage load and flow velocity.

[0004] Under the conditions of the provided pressure ratio and efficiency, the number of turbine stages can only be appropriately increased to a certain limit. Beyond this limit, the efficiency gain is very small. At the same time, as the number of stages increases, the structure becomes more complex, the size and weight of the unit also increase, and the sealing and leakage losses also increase, which increases the maintenance cost of the unit and has a certain impact on the reliability of use.

[0005] The selection of flue gas turbine stages is a process that comprehensively considers multiple factors. Different working fluids have different flow characteristics and energy conversion efficiencies in turbines. It is necessary to select the appropriate turbine stages based on factors such as flue gas temperature and pressure, working fluid characteristics, turbine efficiency and structure, and operating conditions and requirements to ensure efficient and stable operation of the turbine. Currently, the flue gas turbine stages are selected based on experience or reference to data from other similar models. The selection is somewhat subjective and lacks a unified standard, resulting in the inability to fully utilize the unit's work capacity. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention proposes a method and system for determining the number of flue gas turbine stages in a flue gas turbine, which improves the efficiency and reliability of the flue gas turbine while meeting the overall pressure and temperature performance index requirements of the flue gas turbine unit.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for determining the number of flue gas turbine stages in a flue gas turbine comprises the following steps:

[0009] S1, obtaining the operating parameters of the flue gas turbine and the corresponding flue gas turbine stages, wherein the operating parameters include turbine pressure ratio and inlet temperature, wherein the unit of the inlet temperature is thermodynamic temperature, wherein each turbine pressure ratio and the corresponding inlet temperature and flue gas turbine stage constitute a data group;

[0010] S2, using all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group, fitting to obtain the relationship Q for calculating the inlet temperature from the turbine pressure ratio, and then combining the corresponding inlet temperature and the flue gas turbine stage in each data group, fitting to obtain the corresponding relationship between the criterion value Np and the flue gas turbine stage, the criterion value Np is determined by the relationship Q and the inlet temperature;

[0011] S3, determining a criterion value Np using the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine stage is to be determined, and determining the corresponding flue gas turbine stage based on the corresponding relationship between the criterion value Np and the flue gas turbine stage.

[0012] Preferably, the turbine pressure ratio described in S1 is obtained by the turbine inlet pressure P1 and the actual turbine outlet pressure P0.

[0013] Furthermore, the actual turbine outlet pressure P0 is the sum of the turbine outlet pressure P2 and the outlet loss pressure P3.

[0014] Further, the turbine pressure ratio described in S1 is obtained by the following formula:

[0015] ΔP=P1 / (P2+P3), where ΔP is the turbine pressure ratio.

[0016] Preferably, S2 uses the least squares method to fit all turbine pressure ratios and the inlet temperatures corresponding to each turbine pressure ratio in the corresponding data group to obtain a relationship Q for calculating the inlet temperature from the turbine pressure ratio.

[0017] Further, the relationship Q is as follows:

[0018] T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP) 4 -1.318×103 (ΔP) 3 +3.135×10 3 (ΔP)2-3.622×1

[0019] 0 3 ΔP+2.540×10 3 , where T is the calculated inlet temperature.

[0020] Further, the criterion value Np described in S2 is determined by the following formula:

[0021] Np = [T1-273.15] / T.

[0022] Furthermore, the corresponding relationship between the criterion value Np in S2 and the number of flue gas turbine stages is as follows:

[0023] When Np>1, the flue gas turbine stage is double-stage; when Np<1, the flue gas turbine stage is single-stage.

[0024] A system for determining the number of flue gas turbine stages in a flue gas turbine comprises a data acquisition unit, a data acquisition system and a data processing unit;

[0025] The data acquisition unit includes a temperature sensor and a pressure gauge, the temperature sensor is used to collect the inlet temperature of the flue gas turbine, and the pressure gauge is used to collect the turbine inlet pressure and turbine outlet pressure of the flue gas turbine;

[0026] The data acquisition system is used to receive the inlet temperature, turbine inlet pressure, turbine outlet pressure and outlet loss pressure of the flue gas turbine;

[0027] The data processing unit includes a first data processing unit, a second data processing unit, a third data processing unit and a fourth data processing unit:

[0028] The first data processing unit is used to calculate the turbine pressure ratio through the turbine inlet pressure, the turbine outlet pressure and the outlet loss pressure;

[0029] The second data processing unit is used to fit the relationship Q for calculating the inlet temperature from the turbine pressure ratio by using all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group;

[0030] The third data processing unit is used to combine the relationship Q, the corresponding inlet temperature and the flue gas turbine stage in each data group to fit the corresponding relationship between the criterion value Np and the flue gas turbine stage;

[0031] The fourth data processing unit is used to determine the criterion value Np using the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine stage is to be determined, and determine the corresponding flue gas turbine stage according to the corresponding relationship between the criterion value Np and the flue gas turbine stage.

[0032] Furthermore, the temperature sensor is a thermocouple.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] The present invention provides a method for determining the number of flue gas turbines in a flue gas turbine. In a data group formed by a large number of turbine pressure ratios, inlet temperatures and flue gas turbine numbers, from the overall turbine pressure ratio, inlet temperature and turbine number analysis, there is a certain mutual relationship between the turbine pressure ratio, inlet temperature and the corresponding flue gas turbine number of the flue gas turbine. Based on this, these data can be first obtained, and then the number of flue gas turbines in the flue gas turbine is determined in steps using this relationship; first, all turbine pressure ratios and corresponding inlet temperatures are used to fit a relationship for calculating the inlet temperature from the turbine pressure ratio, and then the relationship is applied to the corresponding inlet temperature and flue gas turbine number in each data group. A criterion value can be first fitted by the relationship and the inlet temperature, and then the corresponding relationship between the criterion value and the flue gas turbine number is further clarified. Therefore, the criterion value can be first determined using the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine number is to be determined, and then the flue gas turbine number is determined by the corresponding relationship between the criterion value and the flue gas turbine number. The present invention changes the method of giving the flue gas turbine stage based on experience to gradually obtaining the corresponding relationship between the criterion value and the flue gas turbine stage based on a fitting method, which facilitates the judgment and giving of the flue gas turbine stage, improves the design method of the flue gas turbine stage, provides a standard for defining the flue gas turbine stage, improves the design method, provides a definition standard, forms a design specification, and provides a convenient, fast and highly reliable reference technology for designers. It can be applied to the flue gas turbine device of the catalytic cracking waste heat energy recovery unit in the petrochemical industry, and can greatly shorten the design calculation time, improve the design efficiency, and enhance the design technology level.

[0035] The present invention discloses a system for determining the number of flue gas turbine stages in a flue gas turbine. The data acquisition system can receive the inlet temperature, turbine inlet pressure, turbine outlet pressure and outlet loss pressure of the flue gas turbine. The first data processing unit can calculate the turbine pressure ratio through the turbine inlet pressure, turbine outlet pressure and outlet loss pressure. The second data processing unit can use all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group to fit a relationship formula for calculating the inlet temperature from the turbine pressure ratio. The third data processing unit can combine the relationship formula, the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group, and the outlet loss pressure of the flue gas turbine. The corresponding inlet temperature and flue gas turbine order are fitted to obtain the corresponding relationship between the criterion value and the flue gas turbine order; the fourth data processing unit can use the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine order is to be determined to determine the criterion value, and the corresponding flue gas turbine order can be conveniently determined by the corresponding relationship between the criterion value and the flue gas turbine order. A more reasonable implementation method for determining the flue gas turbine order in a smoke gas turbine is provided, which improves the efficiency and reliability of the smoke gas turbine while meeting the overall pressure and temperature performance index requirements of the smoke gas turbine unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The figure is a schematic diagram of the process of the method of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0038] The present invention designs a method for determining the number of flue gas turbines in a flue gas turbine. The design idea is: firstly, the operating parameters (turbine pressure ratio and inlet temperature) of the flue gas turbine and the corresponding number of flue gas turbines are obtained. Specifically, the unit of the inlet temperature is thermodynamic temperature. Each turbine pressure ratio and the corresponding inlet temperature and the number of flue gas turbines constitute a data group. Then, all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group are used to fit a relationship for calculating the inlet temperature from the turbine pressure ratio, which is recorded as the relationship Q, and then apply the relational expression Q to the corresponding inlet temperature and flue gas turbine stage in each data group. Combined with the corresponding inlet temperature and flue gas turbine stage in each data group, the criterion value is first obtained by fitting the relational expression Q and the inlet temperature, recorded as Np, and then the corresponding relationship between Np and the flue gas turbine stage is further clarified. In this way, the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine stage is to be determined can be used to determine Np. The corresponding relationship between Np and the flue gas turbine stage determined previously can facilitate the determination of the corresponding flue gas turbine stage. The specific implementation plan is as follows Figure 1 As shown, the following steps are included:

[0039] Step 1. Determine basic data

[0040] According to the basic technical data of the overall design of the flue gas turbine, the turbine inlet pressure P1 (unit Pa), outlet pressure P2 (unit Pa), and inlet temperature T1 (unit K) can be obtained.

[0041] Step 2. Estimation of pressure loss

[0042] According to the use of the flue gas turbine, the current empirical method is adopted to give the outlet loss pressure P3 (Pa) of the flue gas turbine.

[0043] Step 3. Turbine pressure ratio calculation

[0044] The turbine pressure ratio is the ratio of the pressure at the turbine inlet to the pressure at the turbine outlet. It reflects the work capacity of the turbine and can be calculated by the following formula.

[0045] Calculated turbine pressure ratio ΔP = P1 / (P2+P3)

[0046] Each turbine pressure ratio and the corresponding inlet temperature and flue gas turbine stage number constitute a data set, and a large number of data sets can be obtained.

[0047] Step 4. Calculation of the relationship between inlet temperature and turbine pressure ratio

[0048] Turbine operation must ensure high efficiency and safety and reliability. The work done by a single-stage turbine has a certain limit. If the turbine is required to do more work, the number of turbine stages must be increased to reduce flow losses. Since there is a certain relationship between the turbine pressure ratio, inlet temperature and turbine stage number, according to the needs of calculation, a relationship Q is first introduced to characterize the relationship between the inlet temperature and the turbine pressure ratio. According to the statistics of all turbine pressure ratios and the inlet temperature data corresponding to each turbine pressure ratio in the corresponding data group, the following relationship Q is obtained through fitting using the least squares method. The fitted inlet temperature T can be calculated by the turbine pressure ratio.

[0049] T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP) 4 -1.318×10 3 (ΔP) 3 +3.135×10 3 (ΔP)2-3.622×1

[0050] 0 3 ΔP+2.540×10 3

[0051] Step 5. Calculation of guideline value

[0052] According to the needs of calculation, a dimensionless criterion value Np is introduced to characterize the comprehensive relationship between turbine pressure ratio, inlet temperature and turbine stage number. According to the fitting relationship Q combined with the corresponding inlet temperature data in each data group, the following formula is obtained through fitting to calculate the judgment criterion value Np.

[0053] Np=[T1-273.15] / T

[0054] Step 6. Criterion value determination

[0055] The criterion value comprehensively represents the relationship between turbine pressure ratio, inlet temperature and turbine stage number. According to statistical data analysis, when it is greater than 1, the turbine stage number is two-stage; when it is less than 1, the turbine stage number is single-stage.

[0056] The corresponding relationship between the criterion value Np and the flue gas turbine stage can be obtained from the above rules. According to the judgment criterion value, the judgment result of the flue gas turbine stage of the flue gas turbine to be determined can be given.

[0057] Np>1, the turbine stage is double-stage.

[0058] Np<1, the turbine stage is single.

[0059] The present invention also provides a specific implementation method of the above method, namely, a system for determining the number of flue gas turbine stages in a flue gas turbine, which specifically includes a data acquisition unit, a data acquisition system and a data processing unit (a first data processing unit, a second data processing unit, a third data processing unit and a fourth data processing unit).

[0060] The data acquisition unit is generally a thermocouple and a pressure gauge. The thermocouple is used to collect the inlet temperature of the flue gas turbine, and the pressure gauge is used to collect the turbine inlet pressure and turbine outlet pressure of the flue gas turbine. The data acquisition system in the computer can receive the inlet temperature, turbine inlet pressure, turbine outlet pressure and outlet loss pressure of the flue gas turbine, wherein the outlet loss pressure is an empirical value given based on experience and is automatically input into the data acquisition system. The turbine inlet pressure, turbine outlet pressure and outlet loss pressure can be further calculated using the computer's calculation function (for ease of description, recorded as the first data processing unit and the subsequent fourth data processing unit) to obtain the turbine pressure ratio, forming an Excel table including thousands of data groups, each group including a turbine pressure ratio, inlet temperature, and flue gas turbine stage.

[0061] The second data processing unit is specifically Minitab software, which can use all turbine pressure ratios in the above Excel table and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group to fit the relationship Q for calculating the inlet temperature from the turbine pressure ratio.

[0062] The third data processing unit is also Minitab software, which can combine the relationship Q and the corresponding inlet temperature in each data group to fit the criterion value Np, and combine the flue gas turbine stage to give the corresponding relationship between the above criterion value Np and the flue gas turbine stage.

[0063] The fourth data processing unit may determine the criterion value Np by using the turbine pressure ratio and the inlet temperature of the flue gas turbine whose flue gas turbine order is to be determined, and then determine the corresponding flue gas turbine order according to the corresponding relationship between the criterion value Np and the flue gas turbine order.

[0064] Embodiment 1:

[0065] Determination of Flue Gas Turbine Stage Number of a Certain Type of Flue Gas Turbine

[0066] The overall technical requirements for the flue gas turbine unit of a petrochemical company are that the turbine inlet pressure P1 (unit Pa) is 2.995×10 5 , the outlet pressure P2 (unit Pa) is 1.059×10 5 , inlet temperature T1 (unit K) is 1180.15, flue gas flow (unit m 3 / min) is 950. Calculate the number of turbine stages according to the overall technical requirements.

[0067] Step 1. Determine basic data

[0068] According to the basic technical data of the overall design of the flue gas turbine, the turbine inlet pressure P1 (unit Pa) can be obtained to be 2.995×10 5 , the outlet pressure P2 (unit Pa) is 1.059×10 5 , the inlet temperature T1 (unit K) is 1180.15.

[0069] Step 2. Estimation of pressure loss

[0070] According to the use of flue gas turbine, the unit outlet loss pressure P3 (Pa) is 0.041×10 5 .

[0071] Step 3. Turbine pressure ratio calculation

[0072] Calculate the turbine pressure ratio, ΔP = P1 / (P2+P3) = 2.723

[0073] Step 4. Calculation of the fitted inlet temperature

[0074] Calculate T using the formula below.

[0075] T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP)4 -1.318×10 3 (ΔP) 3 +3.135×10 3 (ΔP) 2 -3.622×1

[0076] 0 3 ΔP+2.540×10 3 =522.04

[0077] Step 5. Calculation of guideline value

[0078] The judgment criterion value Np is calculated according to the following formula.

[0079] Np=[T1-273.15] / T=1.737

[0080] Step 6. Criterion value determination

[0081] According to the judgment criterion value, the judgment result is given.

[0082] Np>1, the turbine stage is double-stage.

[0083] Example 2

[0084] Determination of Flue Gas Turbine Stage Number of a Certain Type of Flue Gas Turbine

[0085] The overall technical requirements for the flue gas turbine unit of a petrochemical company are that the turbine inlet pressure P1 (unit Pa) is 2.4×10 5 , the outlet pressure P2 (unit Pa) is 1.0869×10 5 , inlet temperature T1 (unit K) is 923.15, flue gas flow (unit m 3 / min) is 2000. Calculate the number of turbine stages according to the overall technical requirements.

[0086] Step 1. Determine basic data

[0087] According to the basic technical data of the overall design of the flue gas turbine, the turbine inlet pressure P1 (unit Pa) can be obtained to be 2.4×10 5 , the outlet pressure P2 (unit Pa) is 1.0869×10 5 , the inlet temperature T1 (unit K) is 923.15.

[0088] Step 2. Estimation of pressure loss

[0089] According to the use of flue gas turbine, the unit outlet loss pressure P3 (Pa) is 0.031×10 5 .

[0090] Step 3. Turbine pressure ratio calculation

[0091] Calculate the turbine pressure ratio, ΔP = P1 / (P2+P3) = 2.147

[0092] Step 4. Calculation of the fitted inlet temperature

[0093] Calculate T using the formula below.

[0094] T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP) 4 -1.318×10 3 (ΔP) 3 +3.135×10 3 (ΔP) 2 -3.622×1

[0095] 0 3 ΔP+2.540×10 3 =721.9

[0096] Step 5. Calculation of guideline value

[0097] The judgment criterion value Np is calculated according to the following formula.

[0098] Np=[T1-273.15] / T=0.9

[0099] Step 6. Criterion value determination

[0100] According to the judgment criterion value, the judgment result is given.

[0101] Np<1, the turbine stage is single.

[0102] Example 3

[0103] Determination of Flue Gas Turbine Stage Number of a Certain Type of Flue Gas Turbine

[0104] The overall technical requirements for the flue gas turbine unit of a petrochemical company are that the turbine inlet pressure P1 (unit Pa) is 3.1×10 5 , the outlet pressure P2 (unit Pa) is 1.08×10 5 , inlet temperature T1 (unit K) is 943.15, flue gas flow (unit m 3 / min) is 3800. Calculate the number of turbine stages according to the overall technical requirements.

[0105] Step 1. Determine basic data

[0106] According to the basic technical data of the overall design of the flue gas turbine, the turbine inlet pressure P1 (unit Pa) can be obtained to be 3.1×10 5, the outlet pressure P2 (unit Pa) is 1.08×10 5 , the inlet temperature T1 (unit K) is 943.15.

[0107] Step 2. Estimation of pressure loss

[0108] According to the use of flue gas turbine, the unit outlet loss pressure P3 (Pa) is 0.04×10 5 .

[0109] Step 3. Turbine pressure ratio calculation

[0110] Calculate the turbine pressure ratio, ΔP = P1 / (P2+P3) = 2.768

[0111] Step 4. Calculation of the fitted inlet temperature

[0112] Calculate T using the formula below.

[0113] T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP) 4 -1.318×10 3 (ΔP) 3 +3.135×10 3 (ΔP) 2 -3.622×10 3 Δ

[0114] P+2.540×10 3 =508.75

[0115] Step 5. Calculation of guideline value

[0116] The judgment criterion value Np is calculated according to the following formula.

[0117] Np=[T1-273.15] / T=1.32

[0118] Step 6. Criterion value determination

[0119] According to the judgment criterion value, the judgment result is given.

[0120] Np>1, the turbine stage is double-stage.

Claims

1. A method for determining the number of flue gas turbine stages in a flue gas turbine, characterized in that: The following steps are involved: S1, obtaining the operating parameters of the flue gas turbine and the corresponding flue gas turbine stages, wherein the operating parameters include turbine pressure ratio and inlet temperature, wherein the unit of the inlet temperature is thermodynamic temperature, wherein each turbine pressure ratio and the corresponding inlet temperature and flue gas turbine stage constitute a data group; S2, using all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group, fitting to obtain the relationship Q for calculating the inlet temperature from the turbine pressure ratio, and then combining the corresponding inlet temperature and the flue gas turbine stage in each data group, fitting to obtain the corresponding relationship between the criterion value Np and the flue gas turbine stage, the criterion value Np is determined by the relationship Q and the inlet temperature; S3, determining a criterion value Np using the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine stage is to be determined, and determining the corresponding flue gas turbine stage based on the corresponding relationship between the criterion value Np and the flue gas turbine stage.

2. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 1, characterized in that: The turbine pressure ratio described in S1 is obtained by the turbine inlet pressure P1 and the actual turbine outlet pressure P0.

3. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 2, characterized in that: The actual turbine outlet pressure P0 is the sum of the turbine outlet pressure P2 and the outlet loss pressure P3.

4. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 3, characterized in that: The turbine pressure ratio described in S1 is obtained by the following formula: ΔP=P1 / (P2+P3), where ΔP is the turbine pressure ratio.

5. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 1, characterized in that: S2 uses the least squares method to fit all turbine pressure ratios and the inlet temperatures corresponding to each turbine pressure ratio in the corresponding data set, and obtains the relationship Q for calculating the inlet temperature from the turbine pressure ratio.

6. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 5, characterized in that: The relationship Q is as follows: T=-1.775×10 1 (ΔP) 5 +2.523×10 2 (ΔP) 4 -1.318×10 3 (ΔP) 3 +3.135×10 3 (ΔP)2-3.622×1 0 3 ΔP+2.540×10 3 , where T is the calculated inlet temperature.

7. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 6, characterized in that: The criterion value Np described in S2 is determined by the following formula: Np = [T1-273.15] / T.

8. The method for determining the number of flue gas turbine stages in a flue gas turbine according to claim 7, characterized in that: The corresponding relationship between the criterion value Np and the number of flue gas turbine stages is as follows: When Np>1, the flue gas turbine stage is double-stage; when Np<1, the flue gas turbine stage is single-stage.

9. A system for determining the number of flue gas turbine stages in a flue gas turbine, characterized in that: It includes a data acquisition unit, a data acquisition system and a data processing unit; The data acquisition unit includes a temperature sensor and a pressure gauge, the temperature sensor is used to collect the inlet temperature of the flue gas turbine, and the pressure gauge is used to collect the turbine inlet pressure and turbine outlet pressure of the flue gas turbine; The data acquisition system is used to receive the inlet temperature, turbine inlet pressure, turbine outlet pressure and outlet loss pressure of the flue gas turbine; The data processing unit includes a first data processing unit, a second data processing unit, a third data processing unit and a fourth data processing unit: The first data processing unit is used to calculate the turbine pressure ratio through the turbine inlet pressure, the turbine outlet pressure and the outlet loss pressure; The second data processing unit is used to fit the relationship Q for calculating the inlet temperature from the turbine pressure ratio by using all turbine pressure ratios and the inlet temperature corresponding to each turbine pressure ratio in the corresponding data group; The third data processing unit is used to combine the relationship Q, the corresponding inlet temperature and the flue gas turbine stage in each data group to fit the corresponding relationship between the criterion value Np and the flue gas turbine stage; The fourth data processing unit is used to determine the criterion value Np using the turbine pressure ratio and inlet temperature of the flue gas turbine whose flue gas turbine stage is to be determined, and determine the corresponding flue gas turbine stage according to the corresponding relationship between the criterion value Np and the flue gas turbine stage.

10. The system for determining the number of flue gas turbine stages in a flue gas turbine according to claim 9, characterized in that: The temperature sensor is a thermocouple.

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