A method for optimizing the integrated operation of gas-steam combined cycle cogeneration units from source to grid

Abstract

The present invention provides a method for optimizing the integrated source-network operation of a gas-steam combined cycle cogeneration unit, comprising: establishing a hydraulic and thermal calculation model for the steam heating pipe network based on the layout of the steam heating pipe network and hydraulic and thermal design parameters; establishing a variable operating condition thermal calculation model for the underlying steam cycle of the gas-steam combined cycle cogeneration unit based on the design parameters of the underlying steam cycle of the gas-steam combined cycle cogeneration unit; establishing a source-network integrated operation optimization model for the gas-steam combined cycle cogeneration unit by combining the hydraulic and thermal calculation models for the steam heating pipe network and the variable operating condition thermal calculation model for the underlying steam cycle of the gas-steam combined cycle cogeneration unit; and performing heating control valve opening optimization calculation based on the source-network integrated operation optimization model for the gas-steam combined cycle cogeneration unit to obtain an optimal heating control valve opening, thereby enabling the combined cycle cogeneration unit to operate at optimal efficiency. By determining the optimal heating valve opening under different heating steam flow rates, the present invention ensures that the heating steam pressure operates at the combined optimal source-network value, thereby improving the operating efficiency of the combined cycle heat and power unit.

Description

Technical Field

[0001] The present invention belongs to the field of gas-steam combined cycle cogeneration units, and in particular relates to a source-grid integrated operation optimization method for gas-steam combined cycle cogeneration units. Background Art

[0002] Gas-steam combined cycle cogeneration units offer advantages such as cleanliness, environmental friendliness, high overall efficiency, and a small footprint. They are used not only as the primary heat source for centralized heating in large northern cities like Beijing, but also as a heat source for industrial steam in economically developed regions such as Guangdong and Jiangsu in the south. However, due to a lack of operational personnel to conduct online, integrated source-network optimization, the heating operation of gas-steam combined cycle cogeneration units, which serve as heat sources for steam heating networks, has room for further optimization and energy reduction. A typical example is the inability to determine the steam pressure and temperature at the start of the steam heating network in real time based on the steam pressure and temperature required by end-users of the steam heating network. This results in the unit's heating regulating valve being in a constant pressure-blocked state. Consequently, when the unit is operating under certain operating conditions, the actual steam pressure and temperature at end-users of the steam heating network far exceed their actual requirements, resulting in significant energy waste. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to accurately guide the source-grid comprehensive operation optimization of a gas-steam combined cycle cogeneration unit, the present invention provides a source-grid comprehensive operation optimization method for a gas-steam combined cycle cogeneration unit. By determining the optimal heating regulating valve opening under different heating steam flow rates, the heating steam pressure is ensured to operate at the source-grid comprehensive optimal value, thereby improving the operating efficiency of the combined cycle cogeneration unit.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] The integrated source-grid operation optimization method for gas-steam combined cycle cogeneration units includes:

[0006] Based on the layout of the steam heating pipe network and the hydraulic and thermal design parameters, a hydraulic and thermal calculation model for the steam heating pipe network is established;

[0007] Based on the design parameters of the bottom steam cycle of the gas-steam combined cycle cogeneration unit, a variable operating condition thermal calculation model of the bottom steam cycle of the gas-steam combined cycle cogeneration unit is established;

[0008] Combine the hydraulic and thermal calculation models of the steam heating network and the variable-operating-condition thermal calculation model of the underlying steam cycle of the gas-steam combined cycle cogeneration unit to establish a comprehensive source-grid operation optimization model for the gas-steam combined cycle cogeneration unit.

[0009] Based on the source-grid integrated operation optimization model of the gas-steam combined cycle cogeneration unit, the heating control valve opening optimization calculation is carried out to obtain the optimal heating control valve opening, so that the combined cycle cogeneration unit can operate at the best efficiency.

[0010] A further improvement of the present invention is that the hydraulic and thermal calculation models of the steam heating network are expressed as follows:

[0011] (P hea，inlet , T hea，inlet )=f steam pipe (P hea，outlet , T heat，outlet ,m heat )

[0012] Where: P heat,inlet is the steam pressure at the starting end of the steam heating network, MPa;

[0013] T heat,inlet is the steam temperature at the starting end of the steam heating network, °C;

[0014] f steam pipe Provide hydraulic and thermal calculation models for steam heating pipe networks;

[0015] P heat,outlet The steam pressure required by the end users of the steam heating network, MPa;

[0016] T heat,outlet The steam temperature required by the end user of the steam heating network, °C;

[0017] m heat is the heating steam flow rate of the steam heating network, t / h.

[0018] A further improvement of the present invention is that the variable operating condition thermal calculation model of the bottom steam cycle of the gas-steam combined cycle cogeneration unit is expressed as follows:

[0019] (P heat，supply , T hea，supply ,W st )=f bottomcycle (P a , T a ,RH,LOAD GT , m heat , valve_p heat )

[0020] Where: P heat,supply Steam pressure for heating the unit, MPa;

[0021] T heat,supply The steam temperature for heating the unit, ℃;

[0022] W st is the steam turbine power of the combined cycle cogeneration unit, MW;

[0023] f bottomcycle It is a variable operating condition thermal calculation model for the bottom steam cycle of a gas-steam combined cycle cogeneration unit;

[0024] P a is the atmospheric pressure, kPa;

[0025] T a is the atmospheric temperature, °C;

[0026] RH is relative humidity, %;

[0027] LOAD GT is the gas turbine load;

[0028] m heat is the heating steam flow rate of the steam heating network, t / h;

[0029] valve_p heat Adjust the valve opening for heating.

[0030] A further improvement of the present invention is that the expression of the source-grid integrated operation optimization model of the gas-steam combined cycle cogeneration unit is as follows:

[0031]

[0032] Where: f CCPP&pipe It is a source-grid integrated operation optimization model for gas-steam combined cycle cogeneration units.

[0033] A further improvement of the present invention is that the atmospheric pressure Pa, the atmospheric temperature T a and relative humidity RH are the actual operating data of the gas-steam combined cycle cogeneration unit.

[0034] A further improvement of the present invention is that the engine load LOAD GT , Heating steam flow rate of steam heating network m heat and heating valve opening valve_p heat All data are actual operating data of gas-steam combined cycle cogeneration units and steam pipeline networks.

[0035] A further improvement of the present invention is that the steam pressure P required by the end user of the steam heating network is heat,outlet Determined based on the requirements of end users.

[0036] A further improvement of the present invention is that the steam temperature T required by the end user of the steam heating network is heat,outletDetermined based on the requirements of end users.

[0037] The present invention has at least the following beneficial technical effects:

[0038] The present invention provides a method for optimizing the source-network comprehensive operation of a gas-steam combined cycle cogeneration unit. The method regards the combined cycle cogeneration unit and the steam heating pipeline network as a whole, and determines in real time the steam pressure and temperature parameters required at the starting end of the steam heating pipeline network, i.e., the unit side, based on the steam parameters required by the end users of the steam heating pipeline network and the heating steam flow of the pipeline network. Then, based on the real-time operation status of the bottom steam cycle of the combined cycle unit, the optimal heating regulating valve opening is determined, thereby achieving the source-network comprehensive operation optimization of the gas-steam combined cycle cogeneration unit, so that the bottom steam cycle of the combined cycle cogeneration unit operates at the best efficiency, and avoiding the huge energy waste of the unit caused by the unit's heating regulating valve being in a pressure-blocking state under some operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of the method for optimizing the source-grid integrated operation of a gas-steam combined cycle cogeneration unit.

[0040] Figure 2 Schematic diagram of the optimization results of source-grid online integrated operation under 100% unit load.

[0041] Figure 3 Schematic diagram of the optimization results of source-grid online integrated operation under 75% unit load. DETAILED DESCRIPTION

[0042] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present invention and the features within the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0043] like Figure 1 As shown, the present invention provides a method for optimizing the source-grid integrated operation of a gas-steam combined cycle cogeneration unit, comprising:

[0044] The pipeline pressure drop of the steam heating network is caused by the resistance loss along the pipeline and the local resistance loss, namely:

[0045] ΔP s，pipe =ΔP s，pipe,m +ΔP s，pipe,d

[0046] Where: ΔP s,pipe is the pressure loss of the steam pipe, Pa;

[0047] ΔP s,pipe,m is the resistance loss along the steam pipeline, Pa;

[0048] ΔP s,pipe,d is the local resistance loss of the steam pipe, Pa.

[0049] ΔP s,pipe,m =R s,pipe L s,pipe

[0050] Where: R s,pipe is the specific friction resistance of the steam pipe, Pa / m;

[0051] L s,pipe is the length of the steam pipe, m.

[0052]

[0053] Where: s,pipe is the friction coefficient of the steam pipe;

[0054] m s,pipe is the steam flow rate of the steam pipeline, t / h;

[0055] D n,s,pipe is the diameter of the steam pipe, m;

[0056] P s,pipe is the density of steam in the steam pipe, kg / m 3 .

[0057]

[0058] Where: K d,s,pipe is the absolute roughness of the steam pipe wall, mm.

[0059] ΔP s，pipe,d =α s，pipe ×ΔP s,pipe,m

[0060] Where: α s,pipe It is the ratio of the local resistance to the longitudinal resistance of the steam pipe.

[0061] The heat loss of a steam pipeline per unit length is calculated using the heat transfer coefficient, which is mainly calculated by the convection heat transfer coefficient between steam and the pipe wall, the thermal conductivity of the pipe wall, insulation layer and outer casing, and the thermal conductivity of the soil (direct burial) or the convection heat transfer coefficient between air and the outer wall of the pipe (overhead or trench), namely:

[0062]

[0063] Where: K s,pipe is the total heat transfer coefficient of the steam pipe, W / m 2 .℃;

[0064] h 1p is the heat transfer coefficient of steam to the inner wall of the pipe, W / m 2 .℃;

[0065] d i,p is the distance from each layer of material to the center of the steam pipe, m;

[0066] λ i,p is the thermal conductivity of each layer of material in the steam pipe, W / m 2 .℃;

[0067] α p is the heat transfer coefficient of the steam pipe to the soil (direct burial) or the convection heat transfer coefficient between the steam pipe and the air (overhead or trench), W / m 2 .℃.

[0068] Based on the hydraulic and thermal calculation formulas of the steam pipeline, the layout of the steam heating network and the hydraulic and thermal design parameters, a hydraulic and thermal calculation model of the steam heating network is established. According to the steam parameters required by the end users of the steam heating network and the heating steam flow of the network, the steam pressure and temperature parameters required at the starting end of the steam heating network, i.e., the unit side, can be determined.

[0069] (P heat，inlet , T heat，inlet )=f steam pipe (P hea，outlet , T hea，outlet ,m heat )

[0070] Where: P heat,inlet is the steam pressure at the starting end of the steam heating network, MPa;

[0071] T heat,inlet is the steam temperature at the starting end of the steam heating network, °C;

[0072] f steam pipe Provide hydraulic and thermal calculation models for steam heating pipe networks;

[0073] P heat,outlet The steam pressure required by the end users of the steam heating network, MPa;

[0074] T heat,outlet The steam temperature required by the end user of the steam heating network, °C;

[0075] m heatis the heating steam flow rate of the steam heating network, t / h;

[0076] For combined cycle cogeneration units that supply external industrial steam, their operating efficiency depends on the ambient meteorological conditions, gas turbine load, fuel composition and external heat supply. Among them, the ambient meteorological conditions, gas turbine load and fuel composition will determine the flue gas flow rate, flue gas temperature and flue gas composition at the inlet of the waste heat boiler, while the ambient meteorological conditions will determine the turbine back pressure. When the combined cycle cogeneration unit is operating at a lower gas turbine load or a larger heat supply, the unit needs to adjust the opening of the heating control valve to maintain a certain heating steam pressure and temperature. Therefore, the operating efficiency of the combined cycle cogeneration unit is also affected by the opening of the heating control valve. Since the combined cycle cogeneration unit mainly operates in a sliding pressure mode, the steam parameters of the unit's external heat supply are also directly related to the operating efficiency of the combined cycle cogeneration unit, and are also affected by the ambient meteorological conditions, gas turbine load, fuel composition, heat supply, and the opening of the heating control valve, that is,

[0077] (P heat，supply , T heat，supply ,W st )=f bottomcycle (P a , T a ,RH,LOAD GT , m heat , valve_p heat )

[0078] Where: P heat,supply Steam pressure for heating the unit, MPa;

[0079] T heat,supply The steam temperature for heating the unit, ℃;

[0080] W st is the steam turbine power of the combined cycle cogeneration unit, MW;

[0081] f bottomcycle It is a variable operating condition thermal calculation model for the bottom steam cycle of a gas-steam combined cycle cogeneration unit;

[0082] P a is the atmospheric pressure, kPa;

[0083] T a is the atmospheric temperature, °C;

[0084] RH is relative humidity, %;

[0085] LOAD GT is the gas turbine load;

[0086] m heat is the amount of steam supplied to the outside, t / h;

[0087] valve_p heat Adjust the valve opening for heating.

[0088] The source-network online integrated operation optimization considers the combined cycle cogeneration unit and the steam heating network as a whole. Based on the steam parameters required by the end users of the steam heating network and the heating steam flow rate of the network, the steam pressure and temperature parameters required at the starting end of the steam heating network, i.e., the unit side, are determined in real time. Then, based on the real-time operation of the bottom steam cycle of the combined cycle unit, the optimal heating valve opening is determined to ensure that the bottom steam cycle of the combined cycle cogeneration unit operates at the best efficiency. The objective function is:

[0089]

[0090] Where: f CCPP&pipe It is a source-grid integrated operation optimization model for gas-steam combined cycle cogeneration units.

[0091] Based on the source-grid integrated operation optimization model of the gas-steam combined cycle cogeneration unit, the heating control valve opening optimization calculation is carried out to obtain the optimal heating control valve opening, so that the combined cycle cogeneration unit can operate at the best efficiency.

[0092] Example:

[0093] If a power plant does not carry out source-network online comprehensive operation optimization, the external steam supply pressure parameters of the combined cycle cogeneration unit are generally maintained at the required heating steam pressure of 1.6MPa at the starting end of the pipeline network, that is, the unit side, under the maximum heat supply, to ensure that the heat network can meet the steam parameter requirements required by the end users of the pipeline network under various steam supply amounts. If source-network online comprehensive operation optimization is carried out, the external steam supply pressure of the unit side will be adjusted in time according to the required heating steam pressure at the starting end of the pipeline network, that is, the unit side. Compared with the case where source-network online comprehensive operation optimization is not carried out, the external steam supply pressure of the unit side at 100% load and 75% load and the net income power of the unit after operation optimization are as follows respectively. Figure 2 and Figure 3 As shown. At 100% unit load, when the heating steam flow is low, the unit's steam pressure reaches 1.87 MPa with the heating control valve fully open (no pressure buildup). However, as the heating steam flow increases, the heating control valve opening must be adjusted to maintain the unit's steam pressure at 1.6 MPa, unless integrated online source-grid operation optimization is implemented. Through integrated online source-grid operation optimization, the unit's external steam pressure is adjusted according to the required heating steam pressure at the network's starting point, i.e., the unit's maximum net revenue power reaches nearly 900 kW. At 75% unit load, through integrated online source-grid operation optimization, the unit's maximum net revenue power reaches nearly 1500 kW.

[0094] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for optimizing the integrated operation of a gas-steam combined cycle cogeneration unit from source to grid, characterized in that: include: Based on the layout of the steam heating pipe network and the hydraulic and thermal design parameters, a hydraulic and thermal calculation model for the steam heating pipe network is established. The expression is as follows: (P heat，inlet ,T heat，inlet )=f steam pipe (P heat，outlet ,T heat，outlet ,m heat ) Where: P heat,inlet is the steam pressure at the starting end of the steam heating network, MPa; T heat,inlet is the steam temperature at the starting end of the steam heating network, °C; f steam pipe Provide hydraulic and thermal calculation models for steam heating pipe networks; P heat,outlet The steam pressure required by the end users of the steam heating network, MPa; T heat,outlet The steam temperature required by the end user of the steam heating network, °C; m heat is the heating steam flow rate of the steam heating network, t / h; Based on the design parameters of the bottom steam cycle of the gas-steam combined cycle cogeneration unit, a variable operating condition thermal calculation model of the bottom steam cycle of the gas-steam combined cycle cogeneration unit is established. The expression is as follows: (P heat，supply ,T heat，supply ,W st )=f bottomcycle (P a ,T a ,RH,LOAD GT ,m heat ,value_p heat ) Where: P heat,supply Steam pressure for heating the unit, MPa; T heat,supply The steam temperature for heating the unit, ℃; W st is the steam turbine power of the combined cycle cogeneration unit, MW; f bottomcycle It is a variable operating condition thermal calculation model for the bottom steam cycle of a gas-steam combined cycle cogeneration unit; P a is the atmospheric pressure, kPa; T a is the atmospheric temperature, °C; RH is relative humidity, %; LOAD GT is the gas turbine load; m heat is the heating steam flow rate of the steam heating network, t / h; valve_p heat Adjust the valve opening for heating; The unit's heating steam temperature and pressure are equal to the steam temperature and pressure at the starting end of the steam heating network, that is, P heat，inlet =P heat,supply T heat,inlett =T heat,supply The hydraulic and thermal calculation models of the steam heating network and the variable-operating-condition thermal calculation model of the underlying steam cycle of the gas-steam combined cycle cogeneration unit are combined to establish a source-grid integrated operation optimization model for the gas-steam combined cycle cogeneration unit. The expression is: Where: f CCPP&pipe Developed a source-grid integrated operation optimization model for gas-steam combined cycle cogeneration units; Based on the source-grid integrated operation optimization model of the gas-steam combined cycle cogeneration unit, the heating control valve opening optimization calculation is carried out to obtain the optimal heating control valve opening, so that the combined cycle cogeneration unit can operate at the best efficiency.

2. The method for optimizing the source-grid integrated operation of a gas-steam combined cycle cogeneration unit according to claim 1, characterized in that: Atmospheric pressure Pa, atmospheric temperature T a and relative humidity RH are the actual operating data of the gas-steam combined cycle cogeneration unit.

3. The method for optimizing the source-grid integrated operation of a gas-steam combined cycle cogeneration unit according to claim 1, characterized in that: Gas turbine load LOAD GT , Heating steam flow rate of steam heating network m heat and heating valve opening valve_p heat All data are actual operating data of gas-steam combined cycle cogeneration units and steam pipeline networks.

4. The method for optimizing the source-grid integrated operation of a gas-steam combined cycle cogeneration unit according to claim 1, characterized in that: Steam pressure P required by the end user of the steam heating network heat,outlet Determined based on the requirements of end users.

5. The method for optimizing source-grid integrated operation of a gas-steam combined cycle cogeneration unit according to claim 1, characterized in that: Steam temperature T required by the end user of the steam heating network heat,outlet Determined based on the requirements of end users.

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