Operation optimization method for multi-heat-source cascade heat supply system coupled with steam ejector

Abstract

The invention discloses an operation optimization method of a multi-heat-source cascade heat supply system coupled with a steam ejector, which comprises the following steps of: 1, calculating the water supply temperature and the water return temperature of a secondary network of a heat supply area based on the environment temperature; 2, on the basis of the environment temperature, the primary heat supply network water supply temperature and the primary heat supply network water return temperature of the multi-heat-source cascade heat supply system under heat supply network adjusting modes including a quality adjusting mode, a quality adjusting mode for changing flow in stages and a quality-quantity parallel adjusting mode are calculated; step 3, respectively calculating the power consumption of the circulating water pump in each adjusting mode; 4, the variable working condition characteristics of the steam ejector are calculated; 5, according to the principle that the waste heat utilization rate is maximum, the heat supply load of the multi-heat-source cascade heat supply system is distributed, and the power supply coal consumption rate bCHP is made to be minimum; step 6, comparing the power supply coal consumption rate under each adjustment mode, and determining a primary network energy-saving adjustment mode; and 7, the minimum anti-freezing flow is calculated, and the heat supply mode of the double-unit multi-heat-source cascade heat supply system is corrected.

Description

Technical Field

[0001] The invention relates to an operation optimization method for a multi-heat source cascade heating system coupled with a steam ejector, and belongs to the technical field of operation optimization of a multi-heat source cascade heating system. Background Art

[0002] The study "Analysis of Heating Network Regulation Characteristics under High Back Pressure + Ejector + Steam Extraction Heating Mode" selects the optimal heating network regulation mode based on the unit's net power generation and circulating water pump power consumption. However, it only provides the unit's exhaust steam and extraction steam capacities for different heating network regulation modes, and fails to define the key operating parameters of the steam ejector. The study "Performance Analysis of Integrated Steam Ejector Combined Heat and Power Waste Heat Heating System Under All Operating Conditions" studies the thermodynamic performance of the steam ejector by calculating the variable operating conditions of the steam ejector. However, it only provides the unit's exhaust steam and extraction steam capacities for different heating network regulation modes, and fails to define the key operating parameters of the steam ejector. While the steam ejector's operating performance is determined through variable operating condition calculations, the characteristics of each heating network regulation mode and the low-energy operation of the units are not analyzed and optimized. Furthermore, both research methods fail to address the issue of air-cooled island anti-freezing. In particular, during the winter heating season, when the unit operates under low output load conditions, the use of excess exhaust steam for heating can cause the air-cooled island to freeze due to insufficient steam inlet. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide an operation optimization method for a multi-heat source cascade heating system coupled with steam ejectors. The present invention calculates the variable operating characteristics of the steam ejectors and provides specific adjustment parameters under the required operating conditions, such as unit back pressure, ejector nozzle opening, and extraction ratio, to achieve cascade heating load distribution. The power supply coal consumption rate replaces the original net power generation and circulating water pump power consumption indicators, which is more advantageous as a measure of the low coal consumption and energy-saving operation of the unit under different heating network regulation modes. Based on the calculation of the variable operating characteristics of the steam ejectors, the present invention describes the heating load distribution and low coal consumption optimization of the cascade heating system under various heating network regulation modes. In addition, the research methods of the two methods did not pay attention to the anti-freezing problem of the air-cooling island, especially in the winter heating period when the unit is operating under low output power load conditions, the excessive exhaust steam used for heating may cause the air-cooling island inlet steam volume to be too small, resulting in freezing problems. For this reason, the present invention takes into account the safe operation of the air-cooling island on the basis of the two methods, and judges and corrects the heating mode when the operating condition is lower than the minimum anti-freezing flow rate in the heat network regulation mode by calculating the minimum anti-freezing flow rate under the target operating condition, thereby forming an operation optimization method for a multi-heat source cascade heating system that combines anti-freezing and energy saving.

[0004] Preferably, the present invention provides an operation optimization method for a multi-heat source cascade heating system coupled with a steam ejector, comprising:

[0005] Step 1: Based on the ambient temperature tw , calculate the water supply temperature t of the secondary network in the heating area g and return water temperature t h ;

[0006] Step 2: Based on the ambient temperature t w , respectively calculate the supply water temperature τ1 and return water temperature τ2 of the primary heating network of the multi-heat source cascade heating system under the heating network regulation modes including the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode;

[0007] Step 3: Calculate the circulating water pump power consumption W of the primary heating network of the dual-machine multi-heat source cascade heating system in the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode. p ;

[0008] Step 4: Based on the variable operating characteristics of the steam ejector, the ejector performance parameters, namely the ejection coefficient μ and the critical back pressure P, are obtained. * , with the nozzle opening α and the ejection steam pressure P s ;

[0009] Step 5: Based on the principle of maximum waste heat utilization, allocate the heating load of the multi-heat source cascade heating system. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, set the back pressure of Unit 2 to the preset heating back pressure. At this time, the nozzle opening α of the steam ejector is 100%. At this time, the high back pressure of Unit 2 and the steam ejector reach the maximum heating load. Adjust the exhaust steam extraction volume of the intermediate pressure cylinder of Unit 1 to make Unit 1 reach the water supply temperature τ1 of the primary heating network. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, optimize the back pressure P of Unit 2. s With the steam ejector nozzle opening α, the power supply coal consumption rate b CHP smallest;

[0010] Step 6: Calculate the power supply coal consumption rate b of the multi-heat source cascade heating system after heat load distribution under each heat network regulation mode CHP , determine the primary network regulation mode to optimize the low energy consumption operation of the multi-heat source cascade heating system by minimizing the power supply coal consumption rate;

[0011] Step 7: Calculate the minimum antifreeze flow rate D pm , and revise the heating mode of the dual-machine multi-heat source cascade heating system.

[0012] Preferably, step 1 comprises:

[0013] Step 101: Determine the design ambient temperature t' based on the heating network operation data and the heat exchanger end difference during the heating period w Secondary network water supply temperature t' g , return water temperature t'h and heating load Q′, where the heating network operation data during the heating period includes the heating network water supply temperature, return water temperature and circulating water volume;

[0014] Step 102: Calculate the indoor temperature t based on the predetermined heating temperature n , calculate different ambient temperatures t w Relative heat load ratio under

[0015]

[0016] Step 103: Based on the relative heat load ratio Get the ambient temperature t w Corresponding heating load Q, different ambient temperatures t w The water supply temperature t of the secondary network quality regulation method under g and return water temperature t h :

[0017]

[0018] Where b is the characteristic coefficient of the radiator.

[0019] Preferably, step 2 comprises:

[0020] Step 201: Determine the design ambient temperature t' based on the heating network operation data during the heating period w Under the primary network water supply temperature τ'1, return water temperature τ'2 and circulating water volume G', the heating load is equal to the secondary network heating load Q';

[0021] Step 202: A network quality adjustment method at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network Calculate different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 under:

[0022]

[0023] Where, For different ambient temperatures t w Relative heat load ratio under t h is the return water temperature, tg is the supply water temperature, t' g is the secondary network water supply temperature, t' h is the secondary return water temperature;

[0024] Step 203: The primary network changes the flow quality regulation mode in stages at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network According to the heat load demand of different heating periods, the corresponding ambient temperature change range stages are divided, and the average circulating water volume is kept constant in each ambient temperature change range stage. The relative flow ratio of the stage with the average circulating water volume G is calculated.

[0025]

[0026] Where const is a constant;

[0027] Calculate different ambient temperatures t w The following is the supply water temperature τ1 and return water temperature τ2 of the quality regulation method that changes the flow rate in stages:

[0028]

[0029] Step 204: Primary network quality-quantity parallel adjustment mode at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network And the relative flow ratio Equal to the relative heat load ratio Changes:

[0030]

[0031] Calculate different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 of the quality-quantity parallel regulation method are as follows:

[0032]

[0033] Preferably, step 3 comprises:

[0034] Step 301: Calculate the power consumption W of the primary network circulating water pump according to the primary network circulating water volume G. p :

[0035]

[0036] Where G is the circulating water volume under the actual operating conditions of the primary network; q' is the design capacity of the circulating water pump; H is the head of the circulating water pump under the actual operating conditions; H' is the head of the circulating water pump under the design conditions; is the overall efficiency of the circulating water pump;

[0037] Step 302: The circulating water volume in the primary network quality regulation mode is maintained at the circulating water volume G' under the design working condition, and the calculated water pump power consumption is kept constant; the circulating water pump power consumption in the quality regulation mode with staged flow rate changes depends on the circulating water volume G in each stage, and the calculated water pump power consumption is kept constant in each stage; the circulating water pump power consumption in the quality-quantity parallel regulation mode depends on the relative flow ratio

[0038] Preferably, step 4 comprises:

[0039] Step 401: Based on the predetermined steam ejector inlet motive steam pressure P p , the ejection steam pressure P corresponding to the rated back pressure of the unit s And the outlet steam pressure P out The variable operating characteristics of the steam ejector are used to calculate the steam flow rate and ejection coefficient μ under the design operating conditions;

[0040] Step 402: Based on the ejector outlet steam pressure P out , determine the pressure of the injected steam P under any nozzle opening α s , ejection coefficient μ and critical back pressure P * ;

[0041] Step 403: Based on the ejector outlet steam pressure P out , determine the ejected steam pressure P s Under this condition, reduce the nozzle opening α, ejection coefficient μ and critical back pressure P * .

[0042] Preferably, step 5 comprises:

[0043] Step 501: Given the water supply temperature τ1 and circulating water volume under various primary network regulation modes, determine the maximum water supply temperature t that can be achieved at the outlet of the second-stage heat exchanger using the rated back pressure of unit 2 and the variable operating characteristics of the steam ejector;

[0044] Step 502: If the maximum supply water temperature t is less than the supply water temperature τ1, the unit is adjusted to operate at the rated back pressure, the steam ejector nozzle opening α is set to 100%, the steam extraction ratio of unit 1 is adjusted to reach the supply water temperature τ1, and the heating load distribution of the high back pressure exhaust steam, steam ejector, and intermediate exhaust steam is determined;

[0045] Step 503: If the maximum water supply temperature t is greater than the water supply temperature τ1, the saturated steam pressure at the heat exchange end differential ejector outlet is calculated by the IAPWS-IF97 formula P out =f(τ1+2) is determined by the compression ratio P s =P out / 1.8 Determine the ejection steam pressure P s ;

[0046] Step 504: According to the variable working condition characteristics of the steam ejector and a given nozzle opening α, the critical back pressure is determined by the formula P * =f(P s ), judge P * With P out The size relationship;

[0047] Step 505: If the critical back pressure corresponding to the nozzle opening α satisfies the condition P * ≥P out , determine the ejection coefficient μ=f(P s If the opposite is true, the nozzle opening α is repeatedly adjusted according to the steam ejector variable operating characteristics until the condition P is met. * ≥P out ; Determine the heating load distribution of high back pressure exhaust steam and steam ejector.

[0048] Preferably, step 6 comprises:

[0049] Step 601: According to different adjustment methods and ambient temperature t w Calculate the energy consumption index of unit 2, power supply coal consumption rate b, based on the distribution of cascade heating load. CHP :

[0050]

[0051] Where Q t The heat input from the boiler to the turbine; Q s is the heating load; η b is the boiler efficiency; η p is the pipeline efficiency; q net The low calorific value of coal; P e is the output electrical power; wp is the power consumption rate of the plant;

[0052] Step 602: At any ambient temperature t w When comparing the coal consumption rate b of the power generation unit under the primary network quality regulation method, the quality regulation method of changing the flow in stages and the quality-quantity parallel regulation method, the CHP , determine the primary heating network regulation method that is suitable for the lowest energy consumption operation of the unit.

[0053] Preferably, step 7 comprises:

[0054] Step 701: Make the following assumptions about the minimum antifreeze flow rate: 1) Ignore the dirt thermal resistance R f 2) The total heat transfer coefficient is equal to the external air convection heat transfer coefficient; 3) The ambient wind speed value in the natural convection state is 0.2m / s;

[0055] Step 702: Calculate the minimum antifreeze flow rate under target operating conditions including different ambient temperatures and different unit back pressures, and determine that the heat transfer coefficient under the target operating conditions is equal to the air-side convection heat transfer coefficient under natural convection:

[0056]

[0057] Where Km is the convective heat transfer coefficient of the target working condition; K t is the air side convection heat transfer coefficient under natural convection conditions;

[0058] Step 703: Calculate the number of heat transfer units under the target operating conditions:

[0059]

[0060] Where, NTU m is the number of heat transfer units under the target working condition; A is the total area of the air cooling island; A y is the windward surface area; v t is the windward wind speed in the natural state; C m is the specific volume of air at ambient temperature; ρ m is the air density at ambient temperature;

[0061] Step 704: Calculate the heat exchange between steam and air in the air-cooling island under the target operating conditions:

[0062] Q m =(1-exp(1-NTU m ))C m ρ m A y v t (t slm -t alm ),

[0063] Where Q m Heat exchange rate for target working condition, kW; t slm is the condensed water temperature after heat exchange; t alm is the ambient air temperature;

[0064] Step 705: At the end of the heat exchange tube pass, the condensate temperature is set to 0°C as the freezing critical temperature, and the minimum antifreeze flow rate under the target working condition is solved using the steam-air heat exchange rate:

[0065]

[0066] Where D pm is the minimum antifreeze flow rate under target working conditions, kg·s -1 ;h pm is the exhaust enthalpy, kJ·kg -1 ;h slm is the enthalpy value when the condensed water reaches the lowest boundary temperature, kJ·kg -1 ;

[0067] Step 706: Based on different ambient temperatures t w and the unit back pressure P s Minimum antifreeze flow D pmBy comparing the steam volume D0 entering the air cooling island with the minimum antifreeze flow D pm The relationship between the size of the primary network energy-saving regulation mode is used to modify the heating conditions;

[0068] Step 707: When the steam volume D0 entering the air cooling island is less than the minimum antifreeze flow rate D pm , then the system heating mode needs to be modified: if the heating load can be met only by high back pressure heating, the exhaust steam volume of high back pressure heating should be reduced, and the exhaust steam extraction heating by steam ejector should be increased, and the appropriate operating condition of steam ejector (unit back pressure P s , nozzle opening α), so that the unit meets the minimum antifreeze flow D pm Requirements: If high back pressure exhaust steam and steam ejector are used to supply heat together at this time, the amount of high back pressure heating steam must be reduced, the nozzle opening of the steam ejector must be increased, and the exhaust steam extraction volume of the intermediate pressure cylinder of unit 1# must be increased to meet the heating demand.

[0069] The beneficial effects achieved by the present invention are:

[0070] The present invention calculates the variable operating characteristics of the steam ejector and provides specific adjustment parameters under the required operating conditions, such as unit back pressure, ejector nozzle opening, and steam extraction ratio, to achieve cascade heating load distribution. This energy consumption indicator, the power supply coal consumption rate, replaces the original net power generation and circulating water pump power consumption indicators, making it more advantageous as a measure of low-coal consumption and energy-saving operation of the unit under different heating network regulation modes. Based on the calculation of the variable operating characteristics of the steam ejector, the present invention describes the heating load distribution and low-coal consumption optimization of the cascade heating system under various heating network regulation modes. Furthermore, existing research methods do not address the issue of air-cooled island antifreeze. In particular, during the winter heating season, when the unit operates under low output power load conditions, the use of excess exhaust steam for heating may cause the air-cooled island inlet steam volume to be too low, leading to freezing. Therefore, the present invention considers the safe operation of the air-cooled island. By calculating the minimum antifreeze flow rate under the target operating conditions, it determines and corrects the conditions that fall below the minimum antifreeze flow rate in the heating network regulation mode.

[0071] In step 4 of the present invention, the variable operating characteristics of the steam ejector when the ejection steam pressure and the nozzle opening are changed are calculated, providing key adjustment parameters for the specific steam ejector operating conditions adopted when allocating the heating load in step 5, such as the ejection steam (exhaust steam) pressure and the ejector nozzle opening.

[0072] In the prior art, the net power generation and circulating water pump power consumption indicators are used as the standards for measuring the energy-saving regulation mode of the heat network, which cannot specifically determine the size of the corresponding unit coal consumption rate. Moreover, under higher net power generation, the unit energy consumption will be higher due to the lower waste heat utilization rate. Therefore, in step 5 of the present invention, the maximum waste heat utilization rate is taken as the principle. By adjusting the unit back pressure, the steam ejector nozzle opening and the steam extraction ratio, the cascade heating load is distributed to meet the water supply temperature requirements. The unit operation is optimized with the low power supply coal consumption rate as the goal. Compared with the use of net power generation and circulating water pump power consumption, it can more intuitively reflect the unit energy consumption under the regulation of the heat network.

[0073] In step 6 of the present invention, after calculating the unit power supply coal consumption rate corresponding to each heating load, the heat network regulation mode that allows the unit to operate at the lowest power supply coal consumption rate is determined through comparison as the unit low energy consumption operation optimization result.

[0074] When the unit is operating at low load during the winter heating period, the air-cooling island may have an inlet steam volume lower than the minimum antifreeze flow rate due to the influence of the high back pressure heating exhaust steam volume and the ejector inlet ejection steam volume, resulting in freezing of the air-cooling island. Therefore, step 7 of the present invention is to ensure the safe operation of the air-cooling island during the winter heating period, calculate the minimum antifreeze flow rate corresponding to each target operating condition, judge and correct the heating network regulation mode that does not meet the antifreeze requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0076] Figure 1 is a flow chart of some embodiments of the present application; DETAILED DESCRIPTION

[0077] See also Figure 1 The present application discloses an operation optimization method for a multi-heat source cascade heating system coupled with steam ejectors, including: when a dual-unit multi-heat source cascade heating system is used to provide heating to regional heat users in winter: two cogeneration units are connected in series for heating, the 2# unit in the cogeneration unit uses a high back pressure coupled ejector for heating, and the 1# unit in the cogeneration unit performs steam extraction peak heating during the severe cold season. The optimization method is to distribute the heating load at each level based on the principle of maximizing waste heat utilization by adjusting the back pressure of the 2# unit, the nozzle opening of the 2# unit's steam ejector, and the exhaust steam volume of the 1# unit, so as to minimize the power supply coal consumption rate of the multi-heat source cascade heating system, including:

[0078] Step 1: Based on the ambient temperature t w , calculate the water supply temperature t of the secondary network in the heating area g and return water temperature th ;

[0079] Step 2: Based on the ambient temperature t w , respectively calculate the supply water temperature τ1 and return water temperature τ2 of the primary heating network of the multi-heat source cascade heating system under the heating network regulation modes including the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode;

[0080] Step 3: Calculate the circulating water pump power consumption W of the primary heating network of the dual-machine multi-heat source cascade heating system in the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode. p ;

[0081] Step 4: Based on the variable operating characteristics of the steam ejector, the ejector performance parameters, namely the ejection coefficient μ and the critical back pressure P, are obtained. * , with the nozzle opening α and the ejection steam pressure P s ;

[0082] Step 5: Based on the principle of maximum waste heat utilization, allocate the heating load of the multi-heat source cascade heating system. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, set the back pressure of Unit 2 to the preset heating back pressure. At this time, the nozzle opening α of the steam ejector is 100%. At this time, the high back pressure of Unit 2 and the steam ejector reach the maximum heating load. Adjust the exhaust steam extraction volume of the intermediate pressure cylinder of Unit 1 to make Unit 1 reach the water supply temperature τ1 of the primary heating network. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, optimize the back pressure P of Unit 2. s With the steam ejector nozzle opening α, the power supply coal consumption rate b CHP smallest;

[0083] Step 6: Calculate the power supply coal consumption rate b of the multi-heat source cascade heating system after heat load distribution under each heat network regulation mode CHP , determine the primary network regulation mode to optimize the low energy consumption operation of the multi-heat source cascade heating system by minimizing the power supply coal consumption rate;

[0084] Step 7: Considering the safe operation of the air-cooled island of unit 2 during the winter heating period, calculate the minimum antifreeze flow rate D pm , and revise the heating mode of the dual-machine multi-heat source cascade heating system.

[0085] In the embodiment of the present application, step 1 includes:

[0086] Step 101: Determine the design ambient temperature t' based on the heating network operation data and the heat exchanger end difference during the heating period w Secondary network water supply temperature t' g , return water temperature t' hand heating load Q′, where the heating network operation data during the heating period includes the heating network supply water temperature, return water temperature, and circulating water volume derived from the unit DCS. The sampling interval of the data derived from the unit DCS is 1 minute;

[0087] Step 102: Calculate the indoor temperature t based on the predetermined heating temperature n , calculate different ambient temperatures t w Relative heat load ratio under That is, the ratio of indoor heating load Q to design heating load Q'. The calculation formula is as follows:

[0088]

[0089] Step 103: Based on the relative heat load ratio Get the ambient temperature t w Corresponding heating load Q, different ambient temperatures t w The water supply temperature t of the secondary network quality regulation method under g and return water temperature t h :

[0090]

[0091] Where b is the characteristic coefficient of the radiator, and its value is 0.35.

[0092] In the embodiment of the present application, step 2 includes:

[0093] Step 201: Determine the design ambient temperature t' based on the heating network operation data during the heating period w Under the primary network water supply temperature τ'1, return water temperature τ'2 and circulating water volume G', the heating load is equal to the secondary network heating load Q';

[0094] Step 202: A network quality adjustment method at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network Therefore, calculate the different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 under:

[0095]

[0096] Where D is calculated by the following formula:

[0097]

[0098] Where, For different ambient temperatures t w Relative heat load ratio under t h is the return water temperature, tg is the supply water temperature, t' gis the secondary network water supply temperature, t' h is the secondary return water temperature;

[0099] Step 203: The primary network changes the flow quality regulation mode in stages at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network According to the heat load demand of different heating periods, the corresponding ambient temperature change range stages are divided, and the average circulating water volume is kept constant in each ambient temperature change range stage. The relative flow ratio of the stage with the average circulating water volume G is calculated. Satisfies the following relationship:

[0100]

[0101] In the formula, const is a constant;

[0102] Calculate different ambient temperatures t w The following is the supply water temperature τ1 and return water temperature τ2 of the quality regulation method that changes the flow rate in stages:

[0103]

[0104] Where F is calculated by the following formula:

[0105]

[0106] Step 204: Primary network quality-quantity parallel adjustment mode at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network And the relative flow ratio Equal to the relative heat load ratio Changes:

[0107]

[0108] Calculate different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 of the quality-quantity parallel regulation method are as follows:

[0109]

[0110] τ2=τ1-(τ1'-τ'2),

[0111] Where C is calculated by the following formula:

[0112]

[0113] In this embodiment of the present application, step 3 includes:

[0114] Step 301: Power consumption W of the primary network circulating water pumpp Driven by thermal power generation, the power consumption W of the primary network circulating water pump is calculated based on the primary network circulating water volume G p , and has a cubic relationship with the circulating water volume G, and the calculation is shown as follows:

[0115]

[0116]

[0117] Where G is the circulating water volume under the actual operating conditions of the primary network, t·h -1 ; q' is the design capacity of the circulating water pump, t·h -1 ; H is the head of the circulating water pump under actual operating conditions, mH2O; H' is the head of the circulating water pump under design conditions, mH2O; is the comprehensive efficiency of the circulating water pump, and the value is 0.86;

[0118] Step 302: The circulating water volume of the primary network quality regulation mode is maintained at the circulating water volume G' under the design working condition, and the calculated water pump power consumption is kept constant; the circulating water pump power consumption of the quality regulation mode in which the flow rate is changed in stages depends on the circulating water volume G of each stage, and the calculated water pump power consumption is kept constant in each stage, and the whole process changes in a step-by-step manner; the circulating water pump power consumption of the quality-quantity parallel regulation mode depends on the ambient temperature t w Changing relative flow ratio

[0119] In the embodiment of the present application, step 4 includes:

[0120] Step 401: Based on the predetermined steam ejector inlet motive steam pressure P p (Exhaust steam from unit 2), ejection steam pressure P corresponding to the rated back pressure of the unit s (unit exhaust steam) and outlet steam pressure P out The variable operating characteristics of the steam ejector are used to calculate the steam flow rate and ejection coefficient μ under the design operating conditions;

[0121] Step 402: Based on the ejector outlet steam pressure P out , determine the pressure of the injected steam P under any nozzle opening α s , ejection coefficient μ and critical back pressure P * ;

[0122] Step 403: Based on the ejector outlet steam pressure P out , determine the ejected steam pressure P s Under this condition, reduce the nozzle opening α, ejection coefficient μ and critical back pressure P * .

[0123] In the embodiment of the present application, step 5 includes:

[0124] Step 501: Given the water supply temperature τ1 and circulating water volume under various primary network regulation modes, determine the maximum water supply temperature t that can be achieved at the outlet of the second-stage heat exchanger using the rated back pressure of unit 2 and the variable operating characteristics of the steam ejector;

[0125] Step 502: If the maximum supply water temperature t is less than the supply water temperature τ1, the unit is adjusted to operate at the rated back pressure, the steam ejector nozzle opening α is set to 100%, the steam extraction ratio of unit 1 is adjusted to reach the supply water temperature τ1, and the heating load distribution of the high back pressure exhaust steam, steam ejector, and intermediate exhaust steam is determined;

[0126] Step 503: If the maximum water supply temperature t is greater than the water supply temperature τ1, the saturated steam pressure at the heat exchange end differential ejector outlet is calculated by the IAPWS-IF97 formula P out =f(τ1+2) is determined by the compression ratio P s =P out / 1.8 Determine the ejection steam pressure P s ;

[0127] Step 504: According to the variable working condition characteristics of the steam ejector and a given nozzle opening α, the critical back pressure is determined by the formula P * =f(P s ), judge P * With P out The size relationship;

[0128] Step 505: If the critical back pressure corresponding to the nozzle opening α satisfies the condition P * ≥P out , determine the ejection coefficient μ=f(P s If the opposite is true, the nozzle opening α is repeatedly adjusted according to the steam ejector variable operating characteristics until the condition P is met. * ≥P out ; Determine the heating load distribution of high back pressure exhaust steam and steam ejector.

[0129] In the embodiment of the present application, step 6 includes:

[0130] Step 601: According to different adjustment methods and ambient temperature t w Calculate the energy consumption index of unit 2, power supply coal consumption rate b, based on the distribution of cascade heating load. CHP :

[0131]

[0132] Where Q t is the heat input from the boiler to the steam turbine, MW; Qs is the heating load, MW; η b is the boiler efficiency, %; η p is the pipeline efficiency, %; q net is the lower calorific value of coal, kJ·kg -1 ;P e is the output power, MW; wp is the power consumption rate of the plant, %;

[0133] Step 602: At any ambient temperature t w When comparing the coal consumption rate b of the power generation unit under the primary network quality regulation method, the quality regulation method of changing the flow in stages and the quality-quantity parallel regulation method, the CHP , determine the primary heating network regulation method that is suitable for the lowest energy consumption operation of the unit.

[0134] In the embodiment of the present application, step 7 includes:

[0135] Step 701: Make the following assumptions about the minimum antifreeze flow rate: 1) Ignore the dirt thermal resistance R f 2) The total heat transfer coefficient is equal to the external air convection heat transfer coefficient; 3) The ambient wind speed value in the natural convection state is 0.2m / s;

[0136] Step 702: Calculate the minimum antifreeze flow rate under target operating conditions including different ambient temperatures and different unit back pressures, and determine that the heat transfer coefficient under the target operating conditions is equal to the air-side convection heat transfer coefficient under natural convection:

[0137]

[0138] Where K m is the convective heat transfer coefficient of the target working condition, W / (m 2 ·K); K t is the air side convection heat transfer coefficient under natural convection conditions, W / (m 2 K);

[0139] Step 703: Calculate the number of heat transfer units under the target operating conditions:

[0140]

[0141] Where, NTU m is the number of heat transfer units under the target working condition; A is the total area of the air cooling island, m 2 ; A y is the windward surface area, m 2 ;v t is the windward wind speed in the natural state, m / s; C m is the specific volume of air at ambient temperature, kJ / (kg·K); ρ mis the air density at ambient temperature, kg / m 3 ;

[0142] Step 704: Calculate the heat exchange between steam and air in the air-cooling island under the target operating conditions:

[0143] Q m =(1-exp(1-NTU m ))C m ρ m A y v t (t slm -t alm ),

[0144] Where Q m Heat exchange rate for target working condition, kW; t slm is the condensed water temperature after heat exchange, which is the set minimum boundary temperature, ℃; t alm is the ambient air temperature, °C;

[0145] Step 705: At the end of the heat exchange tube pass, the condensate temperature is set to 0°C as the freezing critical temperature, and the minimum antifreeze flow rate under the target working condition is solved using the steam-air heat exchange rate:

[0146]

[0147] Where D pm is the minimum antifreeze flow rate under target working conditions, kg·s -1 ;h pm is the exhaust enthalpy, kJ·kg -1 ;h slm is the enthalpy value when the condensed water reaches the lowest boundary temperature, kJ·kg -1 ;

[0148] Step 706: Based on different ambient temperatures t w and the unit back pressure P s Minimum antifreeze flow D pm By comparing the steam volume D0 entering the air cooling island with the minimum antifreeze flow D pm The relationship between the size of the primary network energy-saving regulation mode is used to modify the heating conditions;

[0149] Step 707: When the steam volume D0 entering the air cooling island is less than the minimum antifreeze flow rate D pm , then the system heating mode needs to be modified: if the heating load can be met only by high back pressure heating, the exhaust steam volume of high back pressure heating should be reduced, and the exhaust steam extraction heating by steam ejector should be increased, and the appropriate operating condition of steam ejector (unit back pressure P s , nozzle opening α), so that the unit meets the minimum antifreeze flow D pmRequirements: If high back pressure exhaust steam and steam ejector are used to supply heat together at this time, the amount of high back pressure heating steam must be reduced, the nozzle opening of the steam ejector must be increased, and the exhaust steam extraction volume of the intermediate pressure cylinder of unit 1# must be increased to meet the heating demand.

[0150] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0151] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention as disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not invented herein, and the description and examples are to be considered merely as exemplary.

[0152] The above specific implementation methods further illustrate the purpose, technical solutions and beneficial effects of this application in detail. It should be understood that the above are only specific implementation methods of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent replacements, improvements, etc. made on the basis of the technical solutions of this application should be included in the scope of protection of this application.

Claims

1. An operation optimization method for a multi-heat source cascade heating system coupled with a steam ejector, characterized in that: include: Step 1: Based on the ambient temperature t w , calculate the water supply temperature t of the secondary network in the heating area g and return water temperature t h ; Step 2: Based on the ambient temperature t w , respectively calculate the supply water temperature τ1 and return water temperature τ2 of the primary heating network of the multi-heat source cascade heating system under the heating network regulation modes including the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode; Step 3: Calculate the circulating water pump power consumption W of the primary heating network of the dual-machine multi-heat source cascade heating system in the quality regulation mode, the quality regulation mode with staged flow rate change, and the quality-quantity parallel regulation mode. p ; Step 4: Based on the variable operating characteristics of the steam ejector, the ejector performance parameters, namely the ejection coefficient μ and the critical back pressure P, are obtained. * , with the nozzle opening α and the ejection steam pressure P s ; Step 5: Based on the principle of maximum waste heat utilization, allocate the heating load of the multi-heat source cascade heating system. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, set the back pressure of Unit 2 to the preset heating back pressure. At this time, the nozzle opening α of the steam ejector is 100%. At this time, the high back pressure of Unit 2 and the steam ejector reach the maximum heating load. Adjust the exhaust steam extraction volume of the intermediate pressure cylinder of Unit 1 to make Unit 1 reach the water supply temperature τ1 of the primary heating network. When the maximum saturated temperature of the steam at the steam ejector outlet is less than the water supply temperature τ1 of the primary heating network, optimize the back pressure P of Unit 2. s With the steam ejector nozzle opening α, the power supply coal consumption rate b CHP smallest; Step 6: Calculate the power supply coal consumption rate b of the multi-heat source cascade heating system after heat load distribution under each heat network regulation mode CHP , determine the primary network regulation mode to optimize the low energy consumption operation of the multi-heat source cascade heating system by minimizing the power supply coal consumption rate; Step 7: Calculate the minimum antifreeze flow rate D pm , and revise the heating mode of the dual-machine multi-heat source cascade heating system.

2. The operation optimization method of a multi-heat source cascade heating system coupled with a steam ejector according to claim 1 is characterized in that: Step 1 includes: Step 101: Determine the design ambient temperature t' based on the heating network operation data and the heat exchanger end difference during the heating period w Secondary network water supply temperature t' g , return water temperature t' h and heating load Q′, where the heating network operation data during the heating period includes the heating network water supply temperature, return water temperature and circulating water volume; Step 102: Calculate the indoor temperature t based on the predetermined heating temperature n , calculate different ambient temperatures t w Relative heat load ratio under Step 103: Based on the relative heat load ratio Get the ambient temperature t w Corresponding heating load Q, different ambient temperatures t w The water supply temperature t of the secondary network quality regulation method under g and return water temperature t h : Where b is the characteristic coefficient of the radiator.

3. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 2 includes: Step 201: Determine the design ambient temperature t' based on the heating network operation data during the heating period w Under the primary network water supply temperature τ'1, return water temperature τ'2 and circulating water volume G', the heating load is equal to the secondary network heating load Q'; Step 202: A network quality adjustment method at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network Calculate different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 under: Where, For different ambient temperatures t w Relative heat load ratio under t h is the return water temperature, tg is the supply water temperature, t' g is the secondary network water supply temperature, t' h is the secondary return water temperature; Step 203: The primary network changes the flow quality regulation mode in stages at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network According to the heat load demand of different heating periods, the corresponding ambient temperature change range stages are divided, and the average circulating water volume is kept constant in each ambient temperature change range stage. The relative flow ratio of the stage with the average circulating water volume G is calculated. In the formula, const is a constant; Calculate different ambient temperatures t w The following is the supply water temperature τ1 and return water temperature τ2 of the quality regulation method that changes the flow rate in stages: Step 204: Primary network quality-quantity parallel adjustment mode at different ambient temperatures t w The relative heat load ratio under the condition is equal to the relative heat load ratio of the secondary network And the relative flow ratio Equal to the relative heat load ratio Changes: Calculate different ambient temperatures t w The supply water temperature τ1 and return water temperature τ2 of the quality-quantity parallel regulation method are as follows: τ2=τ1-(τ1'-τ'2), 4. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 3 includes: Step 301: Calculate the power consumption W of the primary network circulating water pump according to the primary network circulating water volume G. p : Where G is the circulating water volume under the actual operating conditions of the primary network; q' is the design capacity of the circulating water pump; H is the head of the circulating water pump under the actual operating conditions; H' is the head of the circulating water pump under the design conditions; is the overall efficiency of the circulating water pump; Step 302: The circulating water volume in the primary network quality regulation mode is maintained at the circulating water volume G' under the design working condition, and the calculated water pump power consumption is kept constant; the circulating water pump power consumption in the quality regulation mode with staged flow rate changes depends on the circulating water volume G in each stage, and the calculated water pump power consumption is kept constant in each stage; the circulating water pump power consumption in the quality-quantity parallel regulation mode depends on the relative flow ratio 5. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 4 includes: Step 401: Based on the predetermined steam ejector inlet motive steam pressure P p , the ejection steam pressure P corresponding to the rated back pressure of the unit s And the outlet steam pressure P out The variable operating characteristics of the steam ejector are used to calculate the steam flow rate and ejection coefficient μ under the design operating conditions; Step 402: Based on the ejector outlet steam pressure P out , determine the pressure of the injected steam P under any nozzle opening α s , ejection coefficient μ and critical back pressure P * ; Step 403: Based on the ejector outlet steam pressure P out , determine the ejected steam pressure P s Under this condition, reduce the nozzle opening α, ejection coefficient μ and critical back pressure P * .

6. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 5 includes: Step 501: Given the water supply temperature τ1 and circulating water volume under various primary network regulation modes, determine the maximum water supply temperature t that can be achieved at the outlet of the second-stage heat exchanger using the rated back pressure of unit 2 and the variable operating characteristics of the steam ejector; Step 502: If the maximum supply water temperature t is less than the supply water temperature τ1, the unit is adjusted to operate at the rated back pressure, the steam ejector nozzle opening α is set to 100%, the steam extraction ratio of unit 1 is adjusted to reach the supply water temperature τ1, and the heating load distribution of the high back pressure exhaust steam, steam ejector, and intermediate exhaust steam is determined; Step 503: If the maximum water supply temperature t is greater than the water supply temperature τ1, the saturated steam pressure at the heat exchange end differential ejector outlet is calculated by the IAPWS-IF97 formula P out =f(τ1+2) is determined by the compression ratio P s =P out / 1.8 Determine the ejection steam pressure P s ; Step 504: According to the variable working condition characteristics of the steam ejector and a given nozzle opening α, the critical back pressure is determined by the formula P * =f(P s ), judge P * With P out The size relationship; Step 505: If the critical back pressure corresponding to the nozzle opening α satisfies the condition P * ≥P out , determine the ejection coefficient μ=f(P s If the opposite is true, the nozzle opening α is repeatedly adjusted according to the steam ejector variable operating characteristics until the condition P is met. * ≥P out ; Determine the heating load distribution of high back pressure exhaust steam and steam ejector.

7. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 6 includes: Step 601: According to different adjustment methods and ambient temperature t w Calculate the energy consumption index of unit 2, power supply coal consumption rate b, based on the distribution of cascade heating load. CHP : Where Q t The heat input from the boiler to the turbine; Q s is the heating load; η b is the boiler efficiency; η p is the pipeline efficiency; q net The low calorific value of coal; P e is the output electrical power; wp is the power consumption rate of the plant; Step 602: At any ambient temperature t w When comparing the coal consumption rate b of the power generation unit under the primary network quality regulation method, the quality regulation method of changing the flow in stages and the quality-quantity parallel regulation method, the CHP , determine the primary heating network regulation method that is suitable for the lowest energy consumption operation of the unit.

8. The method for optimizing the operation of a multi-heat source cascade heating system coupled with steam ejectors according to claim 1, characterized in that: Step 7 includes: Step 701: Make the following assumptions about the minimum antifreeze flow rate: 1) Ignore the dirt thermal resistance R f 2) The total heat transfer coefficient is equal to the external air convection heat transfer coefficient; 3) The ambient wind speed value in the natural convection state is 0.2m / s; Step 702: Calculate the minimum antifreeze flow rate under target operating conditions including different ambient temperatures and different unit back pressures, and determine that the heat transfer coefficient under the target operating conditions is equal to the air-side convection heat transfer coefficient under natural convection: Where K m is the convective heat transfer coefficient of the target working condition; K t is the air side convection heat transfer coefficient under natural convection conditions; Step 703: Calculate the number of heat transfer units under the target operating conditions: Where, NTU m is the number of heat transfer units under the target working condition; A is the total area of the air cooling island; A y is the windward surface area; v t is the windward wind speed in the natural state; C m is the specific volume of air at ambient temperature; ρ m is the air density at ambient temperature; Step 704: Calculate the heat exchange between steam and air in the air-cooling island under the target operating conditions: Q m =(1-exp(1-NTU m ))C m ρ m A y v t (t slm -t alm ), Where Q m Heat exchange rate for target working condition, kW; t slm is the condensed water temperature after heat exchange; t alm is the ambient air temperature; Step 705: At the end of the heat exchange tube pass, the condensate temperature is set to 0°C as the freezing critical temperature, and the minimum antifreeze flow rate under the target working condition is solved using the steam-air heat exchange rate: Where D pm is the minimum antifreeze flow rate under target working conditions, kg·s -1 ;h pm is the exhaust enthalpy, kJ·kg -1 ;h slm is the enthalpy value when the condensed water reaches the lowest boundary temperature, kJ·kg -1 ; Step 706: Based on different ambient temperatures t w and the unit back pressure P s Minimum antifreeze flow D pm By comparing the steam volume D0 entering the air cooling island with the minimum antifreeze flow D pm The relationship between the size of the primary network energy-saving regulation mode is used to modify the heating conditions; Step 707: When the steam volume D0 entering the air cooling island is less than the minimum antifreeze flow rate D pm , then the system heating mode needs to be modified: if the heating load can be met only by high back pressure heating, the exhaust steam volume of high back pressure heating should be reduced, and the exhaust steam extraction heating by steam ejector should be increased, and the appropriate operating condition of steam ejector (unit back pressure P s , nozzle opening α), so that the unit meets the minimum antifreeze flow D pm Requirements: If high back pressure exhaust steam and steam ejector are used to supply heat together at this time, the amount of high back pressure heating steam must be reduced, the nozzle opening of the steam ejector must be increased, and the exhaust steam extraction volume of the intermediate pressure cylinder of unit 1# must be increased to meet the heating demand.

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