A calculation method for coal consumption of extraction steam heating for thermal power units

Abstract

The present invention discloses a method for calculating the coal consumption of extraction steam heating in a thermal power unit. Starting from the concept of equivalent enthalpy drop and based on the data in the thermal characteristics book of the steam turbine, the method calculates the ratio of extraction steam enthalpy drop to main steam equivalent enthalpy drop, main steam flow rate and reheat coefficient under different motor powers. The mathematical regression method is used to fit the functions respectively, and a calculation model is established in which the ratio of extraction steam enthalpy drop to main steam equivalent enthalpy drop, main steam flow rate and reheat coefficient change with motor power. The grid-connected unit controls the generator power P unchanged according to the dispatching requirements. After the steam turbine extracts steam for heating, due to the heating extraction steam D C Failure to achieve the exhaust steam parameters results in insufficient actual work, necessitating an increase in the main steam flow rate D0 to maintain constant output power P. The increase in main steam flow rate after extraction steam heating represents the cost of extraction steam heating. Calculating the increase in main steam flow rate yields the heating coal consumption. This method allows for simple calculation of heating coal consumption for different extraction steam stages after reheating.

Description

Technical Field

[0001] The present invention relates to the technical field of energy consumption calculation of coal-fired power plants, and in particular to a method for calculating coal consumption of thermal power units using steam extraction for heating. Background Art

[0002] The country is implementing a strategy for high-quality energy development, with reducing carbon emissions and improving comprehensive energy utilization efficiency as the development direction for energy companies. Cogeneration units can simultaneously provide heat and electricity, representing a thermodynamically efficient use of fuel. Therefore, they are widely used in power generation and heating. Cogeneration is an important and effective way for thermal power plants to improve energy utilization, reduce carbon emissions, and increase profitability.

[0003] Currently known calculations of heating costs in cogeneration are still limited to the sharing of cogeneration revenues, rather than calculating the specific costs of heating when the original power generation is simply switched to both power and heat. In actual work, this results in power generation companies being unable to distinguish between costs and revenues, leading to confusion and inaccuracies in the statistical calculation of heating costs.

[0004] Currently, only the power industry standard DL / T 904-2015, "Calculation Methods for Technical and Economic Indicators of Thermal Power Plants," defines heating coal consumption as follows:

[0005] Refers to the amount of standard coal consumed by the unit for every 1GJ of heat supplied to the outside during the statistical period.

[0006] This calculation method is essentially a heat method, but the heat method calculation does not distinguish between the energy levels of the heating steam and cannot correctly reflect the cost of steam of different energy levels. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for calculating the coal consumption of extraction steam for heating in thermal power units, so as to solve the problem that the existing coal consumption calculation method cannot distinguish the energy level of heating steam and cannot correctly reflect the cost of steam of different energy levels.

[0008] To solve the above technical problems, the present invention provides a method for calculating the coal consumption of extraction steam heating for a thermal power unit, which is based on the thermal characteristics of the steam turbine as a basic data source and includes the following steps:

[0009] (1) Based on the concept of equivalent enthalpy drop, calculate the equivalent enthalpy drop of main steam:

[0010] Main steam equivalent enthalpy drop = motor power / main steam flow / mechanical efficiency / generator efficiency;

[0011] (2) Calculate the extraction enthalpy drop using the extraction enthalpy and exhaust enthalpy of the turbine using the turbine thermodynamic characteristics:

[0012] Extraction enthalpy drop = extraction enthalpy - turbine exhaust enthalpy;

[0013] (3) The grid-connected unit controls the generator power P unchanged according to the dispatching requirements; after the steam turbine extracts steam for heating, due to the heating extraction steam D C Failure to perform work to the exhaust parameters results in insufficient actual work, and the main steam flow rate D0 must be increased to maintain the output power P unchanged. The increase in main steam after extraction steam heating is the price paid for extraction steam heating. The heating coal consumption can be calculated by calculating the increase in main steam. According to the power balance:

[0014] Heating extraction steam volume × extraction steam enthalpy drop = main steam increase × main steam equivalent enthalpy drop;

[0015] Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume D C ;

[0016] (5) The ratio of the extraction steam enthalpy drop to the main steam equivalent enthalpy drop at different motor powers is used to fit a function using the mathematical regression method; this function calculation formula reflects the relationship between the turbine extraction steam enthalpy drop (work done) and the main steam equivalent enthalpy drop (work done), and changes with the motor power;

[0017] (6) Using the data from the steam turbine thermal characteristics book, calculate the main steam flow rate and reheat coefficient at different motor powers, and use the mathematical regression method to fit the function;

[0018] (7) Substitute the actual on-site data and calculate other required parameters;

[0019] Unit main steam heat absorption = (main steam enthalpy - feed water enthalpy) + reheat coefficient × (hot reheat steam enthalpy - cold reheat steam enthalpy)

[0020] Heating capacity = (heating extraction steam enthalpy - heating drainage enthalpy) × heating extraction steam volume D C ; or the heat supply shall be based on the heat meter reading during the statistical period;

[0021] Heating steam extraction volume D C = (heating network water outlet temperature - heating network water return temperature) × water specific heat × heating network water flow / (heating extraction steam enthalpy - heating drainage enthalpy); or according to the steam flow meter reading during the statistical period;

[0022] (8) Calculate the coal consumption for steam extraction heating (heating fuel cost)

[0023] Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume D C ;

[0024] Heat absorption = main steam increase × unit main steam heat absorption;

[0025] Heating standard coal quantity = heat absorption / pipeline efficiency / boiler efficiency / standard coal calorific value;

[0026] Heating coal consumption = heating standard coal quantity / heating amount;

[0027] (9) Calculate the heating ratio, which can be used to allocate other costs;

[0028] Heating ratio = main steam increase / (main steam increase + main steam flow before heating).

[0029] The thermal characteristics of the steam turbine are heat balance diagrams of pure condensing conditions under different loads.

[0030] Wherein, the power of different motors in step (5) is 100%, 75%, 50% and 40% respectively.

[0031] Wherein, the power of different motors in step (6) is 100%, 75%, 50% and 40% respectively.

[0032] In step (7), the boiler efficiency is taken as the actual efficiency on site, and the pipeline efficiency is taken as 99%. Beneficial effects

[0033] The present invention provides an automatic logistics cargo conveying system, which has the following beneficial effects:

[0034] The calculation data required by this method are all derived from the heat balance diagram of the heating condition. Based on the principle of equivalence, the heating extraction steam volume is equivalently restored to the change in the main steam volume for calculation. The calculation results can be obtained using on-site operation data. The calculation method is simple and the accuracy meets on-site needs. This method avoids the uncertainty of tedious calculations in complex intermediate processes.

[0035] The proposed method can provide reference for operators, realize engineering application, and provide convenient technical support for the actual operation of cogeneration units. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the thermal balance diagram for the operating condition when the motor power is 40%;

[0037] Figure 2 This is the thermal balance diagram for the operating condition when the motor power is 50%;

[0038] Figure 3 This is the thermal balance diagram for the operating condition when the motor power is 75%;

[0039] Figure 4 This is the thermal balance diagram for the operating condition when the motor power is 100%;

[0040] Figure 5 The figure is the fitting function diagram of the ratio of extraction steam enthalpy drop to main steam equivalent enthalpy drop at different motor powers;

[0041] Figure 6The figure is the fitting function diagram of main steam flow at different motor powers;

[0042] Figure 7 This is the fitting function diagram of the reheat system at different motor powers. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] This embodiment provides a method for calculating the coal consumption of thermal power generation unit extraction steam heating. Taking the four-stage extraction steam of a 300MW unit as an example, the basic data source is the thermal characteristics book of the steam turbine. Figures 1-4 The heat balance diagrams under different working conditions are the data source, which includes the following steps:

[0045] (1) Using the heat balance diagram data: motor power, main steam flow, reheat steam flow, main steam enthalpy, hot reheat steam enthalpy, cold reheat steam enthalpy, turbine exhaust enthalpy, and four-stage extraction steam enthalpy;

[0046] (2) Based on the concept of equivalent enthalpy drop, calculate the equivalent enthalpy drop of main steam: Main steam equivalent enthalpy drop = motor power / main steam flow / mechanical efficiency / generator efficiency;

[0047] Calculation of main steam equivalent enthalpy drop (equivalent work) at 100% motor power:

[0048] 100% motor power: 300MW, main steam flow: 899.99t / h, mechanical efficiency: 99%, generator conversion efficiency: 99%.

[0049] Main steam equivalent enthalpy drop = 300*1000 / (899.99 / 3.6) / 0.99 / 0.99=1224.38

[0050] Calculation of main steam equivalent enthalpy drop (equivalent work) at 75% motor power:

[0051] 75% motor power: 225MW, main steam flow: 652.75t / h, mechanical efficiency: 99%, generator conversion efficiency: 99%.

[0052] Main steam equivalent enthalpy drop = 225*1000 / (652.75 / 3.6) / 0.99 / 0.99=1266.10

[0053] Calculation of main steam equivalent enthalpy drop (equivalent work) at 50% motor power:

[0054] 50% motor power: 150MW, main steam flow: 439.57t / h, mechanical efficiency: 99%, generator conversion efficiency: 99%.

[0055] Main steam equivalent enthalpy drop = 150*1000 / (439.57 / 3.6) / 0.99 / 0.99=1253.42

[0056] Calculation of main steam equivalent enthalpy drop (equivalent work) at 40% motor power:

[0057] 40% motor power: 120MW, main steam flow: 358t / h, mechanical efficiency: 99%, generator conversion efficiency: 99%.

[0058] Main steam equivalent enthalpy drop = 120*1000 / (358 / 3.6) / 0.99 / 0.99=1231.20

[0059] (3) Calculate the extraction enthalpy drop using the extraction enthalpy and exhaust enthalpy of the turbine using the turbine thermodynamic characteristics:

[0060] Extraction enthalpy drop = extraction enthalpy - turbine exhaust enthalpy;

[0061] Calculation of enthalpy drop (equivalent work) of four-stage extraction steam at 100% motor power:

[0062] Enthalpy of exhaust steam from the fourth extraction stage: 3134.7 kj / kg, enthalpy of exhaust steam from the turbine: 2336.4 kj / kg

[0063] Extraction steam enthalpy drop = 3134.7 - 2336.4 = 798.3 kj / kg

[0064] Calculation of enthalpy drop (equivalent work) of four-stage extraction steam at 75% motor power:

[0065] Enthalpy of exhaust steam from the fourth extraction stage: 3134.7 kj / kg, enthalpy of exhaust steam from the turbine: 2359.8 kj / kg

[0066] Extraction steam enthalpy drop = 3134.7-2359.8 = 784.4 kj / kg

[0067] Calculation of enthalpy drop (equivalent work) of four-stage extraction steam at 50% motor power:

[0068] Enthalpy of exhaust steam from the fourth extraction stage: 3111.4 kj / kg, enthalpy of exhaust steam from the turbine: 2385.5 kj / kg

[0069] Extraction steam enthalpy drop = 3111.4 - 2385.5 = 725.9 kj / kg

[0070] Calculation of enthalpy drop (equivalent work) of four-stage extraction steam at 40% motor power:

[0071] Enthalpy of exhaust steam from the fourth extraction stage: 3090.5 kj / kg, enthalpy of exhaust steam from the turbine: 2403 kj / kg

[0072] Extraction steam enthalpy drop = 3090.5-2403 = 687.5 kj / kg

[0073] (4) The grid-connected unit controls the generator power P unchanged according to the dispatching requirements; after the steam turbine extracts steam for heating, due to the heating extraction steam D C Failure to perform work to the exhaust parameters results in insufficient actual work, and the main steam flow rate D0 must be increased to maintain the output power P unchanged. The increase in main steam after extraction steam heating is the price paid for extraction steam heating. The heating coal consumption can be calculated by calculating the increase in main steam. According to the power balance:

[0074] Heating extraction steam volume × extraction steam enthalpy drop = main steam increase × main steam equivalent enthalpy drop;

[0075] Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume D C ;

[0076] (5) The ratio of the extraction steam enthalpy drop to the main steam equivalent enthalpy drop at different motor powers is fitted using a mathematical regression method. The fitting function is as follows: Figure 5 As shown;

[0077] At 100% motor power, extraction steam enthalpy drop / main steam equivalent enthalpy drop = 798.3 / 1224.38*100 = 65.20

[0078] At 75% motor power, extraction steam enthalpy drop / main steam equivalent enthalpy drop = 784.4 / 1266.10*100 = 61.95

[0079] At 50% motor power, extraction steam enthalpy drop / main steam equivalent enthalpy drop = 725.9 / 1253.42*100 = 57.91

[0080] At 40% motor power, extraction steam enthalpy drop / main steam equivalent enthalpy drop = 687.5 / 1231.20*100 = 55.84

[0081] This function calculation formula reflects the relationship between the turbine extraction steam enthalpy drop (work done) and the main steam equivalent enthalpy drop (work done), and changes with the motor power.

[0082] (6) Using the data from the steam turbine thermal characteristics book, calculate the main steam flow rate and reheat coefficient at different motor powers, and use the mathematical regression method to fit the function.

[0083] The main steam flow fitting function at different motor powers is as follows: Figure 6 shown.

[0084] The reheat coefficient fitting function at different motor powers is as follows: Figure 7 shown.

[0085] (7) Substitute the actual on-site data and calculate other required parameters;

[0086] When the motor power is calculated to be 50%, substituting the fitting function in step (5), the extraction steam enthalpy drop / main steam equivalent enthalpy drop is obtained to be 57.83%, the original main steam flow rate is 437.5t / h, and the reheat coefficient is 0.865.

[0087] When the motor power is 50%, the heating extraction steam capacity is 100t / h, the heating extraction enthalpy is 3088kj / kg, the heating drainage enthalpy is 315 kj / kg, the main steam enthalpy is 3429 kj / kg, the feed water enthalpy is 1047.58 kj / kg, the hot reheat steam enthalpy is 3539.75 kj / kg, and the cold reheat steam enthalpy is 3054.83 kj / kg

[0088] Unit main steam heat absorption = (main steam enthalpy - feed water enthalpy) + reheat coefficient × (hot reheat steam enthalpy - cold reheat steam enthalpy) = (3429-1047.58) + 0.865* (3539.75-3054.83) = 2801.55;

[0089] Heating capacity = (heating extraction steam enthalpy - heating drainage enthalpy) × heating extraction steam volume D C

[0090] = (3088-315) * 100 = 277.3;

[0091] Heating steam extraction volume D C According to the steam flow meter reading during the statistical period, it is 100t / h;

[0092] (8) Calculate the coal consumption for steam extraction heating (heating fuel cost)

[0093] Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume Dc

[0094] =57.83%*100=57.83;

[0095] Heat absorption = main steam increase × unit main steam heat absorption = 57.83*1000*2801.55=162017109.9

[0096] Heating standard coal quantity = heat absorption / pipeline efficiency / boiler efficiency / 29308

[0097] =162017109.9 / 0.99 / 0.92 / 29308=6069.5;

[0098] Heating coal consumption = heating standard coal / heating amount = 6069.5 / 277.3;

[0099] Note: Boiler efficiency is based on the actual boiler efficiency of the thermal power unit, which is 92% in this embodiment; pipeline efficiency is 99%; standard coal calorific value is 29308kj / kg;

[0100] (9) Calculate the heating ratio, which can be used to allocate other costs;

[0101] Heating ratio = main steam increase / (main steam increase + main steam flow before heating)

[0102] =57.86 / (57.83+437.50)=11.68%.

[0103] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating coal consumption for steam extraction heating of thermal power units, characterized in that The steam turbine thermal characteristics book is the basic data source, including the following steps: (1) Based on the concept of equivalent enthalpy drop, calculate the equivalent enthalpy drop of main steam: Main steam equivalent enthalpy drop = motor power / main steam flow / mechanical efficiency / generator efficiency; (2) Calculate the extraction enthalpy drop using the extraction enthalpy and exhaust enthalpy of the turbine using the turbine thermodynamic characteristics: Extraction enthalpy drop = extraction enthalpy - turbine exhaust enthalpy; (3) The grid-connected unit controls the generator power P unchanged according to the dispatching requirements; after the steam turbine extracts steam for heating, due to the heating extraction steam D C Failure to perform work to the exhaust parameters results in insufficient actual work, and the main steam flow rate D0 must be increased to maintain the output power P unchanged. The increase in main steam after extraction steam heating is the price paid for extraction steam heating. The heating coal consumption can be calculated by calculating the increase in main steam. According to the power balance: Heating extraction steam volume × extraction steam enthalpy drop = main steam increase × main steam equivalent enthalpy drop; Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume D C ; (5) Use the mathematical regression method to fit the function of the ratio of the extraction steam enthalpy drop to the main steam equivalent enthalpy drop at different motor powers; (6) Using the data from the steam turbine thermal characteristics book, calculate the main steam flow rate and reheat coefficient at different motor powers, and use the mathematical regression method to fit the function; (7) Substitute the actual on-site data and calculate other required parameters; Unit main steam heat absorption = (main steam enthalpy - feed water enthalpy) + reheat coefficient × (hot reheat steam enthalpy - cold reheat steam enthalpy); Heating capacity = (heating extraction steam enthalpy - heating drainage enthalpy) × heating extraction steam volume D C ; Heating steam extraction volume D C = (heating network water outlet temperature - heating network water return temperature) × water specific heat × heating network water flow / (heating steam extraction enthalpy - heating drainage enthalpy); (8) Calculation of coal consumption for extraction steam heating Main steam increase = (extraction steam enthalpy drop / main steam equivalent enthalpy drop) × heating extraction steam volume D C ; Heat absorption = main steam increase × unit main steam heat absorption; Heating standard coal quantity = heat absorption / pipeline efficiency / boiler efficiency / standard coal calorific value; Heating coal consumption = heating standard coal quantity / heating amount; (9) Calculate the heating ratio, which can be used to allocate other costs; Heating ratio = main steam increase / (main steam increase + main steam flow before heating).

2. The method for calculating coal consumption for steam extraction heating of a thermal power unit according to claim 1, characterized in that: The steam turbine thermal characteristics book is a heat balance diagram of pure condensing conditions under different loads.

3. The method for calculating coal consumption for steam extraction heating of a thermal power unit according to claim 1, characterized in that: The power of the different motors in step (5) are 100%, 75%, 50% and 40% respectively.

4. The method for calculating coal consumption for steam extraction heating of a thermal power unit according to claim 1, characterized in that: The power of the different motors in step (6) are 100%, 75%, 50% and 40% respectively.

5. The method for calculating coal consumption for steam extraction heating of a thermal power unit according to claim 1, characterized in that: In step (7), the boiler efficiency is the actual efficiency on site.

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