阅读说明：本技术 一种主汽机和小汽机分设凝汽器下的循环水系统优化方法 (Method for optimizing circulating water system under condenser with main steam turbine and small steam turbine arranged separately ) 是由 蔡兴初 梁涛 唐小锋 朱一鸣 陈彬 施文勇 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种主汽机和小汽机分设凝汽器下的循环水系统优化方法,方法通过采用主汽机部分冷端设备单独优化、小汽机部分校核计算确定个别参数、设置虚拟凝汽器和综合冷却倍率、主汽机冷却塔和合用冷却塔匹配、按水力平衡原理优化小汽机凝汽器其他参数等步骤,将主汽机和小汽机冷端设备,包括凝汽器面积、冷却塔面积、循环水冷却倍率以及供排水管径等几个可变参数进行不同的组合和水力、热力及经济计算并比较分析,得到一个与工程条件吻合的最经济的冷端配置组合方案。(The invention discloses a method for optimizing a circulating water system under a condenser respectively arranged on a main steam turbine and a small steam turbine.)

1. A method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine is characterized by comprising the following steps:

acquiring engineering information, main steam turbine parameters and small steam turbine parameters;

according to the engineering information and the main steam turbine parameters, optimizing and calculating cold end parameters of the main steam turbine with the minimum annual cost as a target to obtain a recommended main steam turbine cold end parameter combination scheme;

according to the recommended main steam turbine cold end parameter combination scheme and the small steam turbine parameters, determining the condenser area and the cooling rate of the small steam turbine through checking calculation;

calculating the comprehensive cooling rate of the condenser shared by the main turbine and the small turbine according to the recommended main turbine cold end parameter combination scheme and the condenser area and the cooling rate of the small turbine;

obtaining an optimal cold end parameter combination of the condenser shared by the main turbine and the small turbine through a shared condenser optimization algorithm according to the comprehensive cooling rate, and determining the cooling tower configuration shared by the main turbine and the small turbine according to the optimal cold end parameter combination of the condenser shared by the main turbine and the small turbine;

and acquiring other parameters of the small steam turbine condenser through a small steam turbine condenser optimization algorithm according to the configuration of the cooling tower shared by the main steam turbine and the small steam turbine, wherein the other parameters of the small steam turbine condenser comprise the backpressure type, the flow type, the type and the length of the cooling pipe bundle and the design flow rate of the small steam turbine condenser.

2. The circulating water system optimization method of claim 1, wherein the engineering information comprises: engineering overview, meteorological conditions, economic indicators; the main steam engine parameters comprise type, rated power, exhaust pressure, thermodynamic data of the main steam engine under different working conditions and the relationship between the micro-increase power and the back pressure of the main steam engine.

3. The method for optimizing the circulating water system according to claim 1, wherein the method for obtaining the recommended main steam engine cold end parameter combination scheme by performing optimization calculation on the main steam engine cold end parameters with the aim of minimum annual cost according to the engineering information and the main steam engine parameters comprises the following steps:

the method comprises the steps that sensitivity analysis is conducted on main steam turbine parameters, a steam turbine parameter optimization algorithm of thermal power plant design software is used for independently optimizing main steam turbine parts, and an optimal calculation result of a main steam turbine water supply system is obtained;

the method comprises the steps that annual total cost sequencing is conducted on the optimization calculation results of a main steam turbine water supply system, and a recommended main steam turbine cold end parameter combination scheme is obtained and comprises cold end parameters matched with a main steam turbine part; the cold end parameters matched with the main steam turbine part comprise: the area of a cooling tower, the area of a condenser, the cooling rate and the tower outlet water temperature of the cooling tower in each season are matched with the main steam turbine part.

4. The circulating water system optimization method of claim 3, wherein the method for determining the condenser area and the cooling rate of the small turbine through checking calculation according to the recommended main turbine cold end parameter combination scheme and the small turbine parameters comprises the following steps:

taking the tower outlet water temperature of the cooling tower in each season matched with the main steam turbine part as the input of a small steam turbine check algorithm of thermal power plant design software to obtain parameters of a small steam turbine condenser;

taking the small steam turbine condenser parameter and the small steam turbine parameter as the input of a condenser check algorithm of thermal power plant design software to obtain the condenser area and the cooling multiplying power of the small steam turbine; the small steam turbine parameters comprise the design backpressure of the small steam turbine, equipment arrangement and thermal data of the small steam turbine under different working conditions.

5. The method for optimizing the circulating water system according to claim 3, wherein the method for calculating the comprehensive cooling rate of the condenser shared by the main turbine and the small turbine according to the recommended main turbine cold end parameter combination scheme, the condenser area of the small turbine and the cooling rate comprises the following steps:

and taking the recommended main steam turbine cold end parameter combination scheme and the condenser area, the cooling rate and the design backpressure of the small steam turbine as the input of a comprehensive cooling rate optimization algorithm of thermal power plant design software, and obtaining the comprehensive cooling rate of the condenser shared by the main steam turbine and the small steam turbine and the sum of the condensing capacities of the main steam turbine and the small steam turbine.

6. The method for optimizing the circulating water system according to claim 3, wherein the method for obtaining the preferred cold end parameter combination of the shared condenser for the main turbine and the small turbine by the shared condenser optimization algorithm according to the comprehensive cooling rate comprises the following steps:

taking the comprehensive cooling multiplying power and the sum of the condensing capacities of the main steam turbine and the small steam turbine as the input of a shared condenser optimization algorithm of the design software of the thermal power plant to obtain the optimal cold end parameter combination of the shared condenser of the main steam turbine and the small steam turbine; the preferable cold end parameter combination of the condenser for sharing the main steam turbine and the small steam turbine comprises the cooling tower area, the tower outlet water temperature, the specification of a circulating water pipe ditch and the pipe diameter of a circulating water pipe of the condenser for sharing the main steam turbine and the small steam turbine.

7. The method for optimizing a circulating water system as claimed in claim 6, wherein the step of determining the configuration of the cooling tower for both the main turbine and the small turbine based on the preferred combination of the cold end parameters of the condenser for both the main turbine and the small turbine comprises: and according to the tower outlet water temperature of the cooling tower in each season matched with the main steam turbine part, searching a cold end configuration with basically equivalent water temperature and high fire proximity in the preferred cold end parameter combination of the condenser for the main steam turbine and the small steam turbine, and determining the configuration as the cooling tower configuration for the main steam turbine and the small steam turbine.

Technical Field

The invention relates to a method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine, and belongs to the field of design of circulating water systems of thermal power plants.

Background

In the design process of a thermal power plant, cold end (circulating water system) optimization is an extremely important link: different combinations are carried out on the variable parameters of the cold end equipment, such as condenser area, cooling tower area, circulating water cooling rate, water supply and drainage pipe diameter and the like, and a most economical cold end configuration combination scheme which is consistent with the engineering conditions is obtained through hydraulic power, thermal power and economic calculation and comparative analysis.

The optimization calculation of the circulating water system needs to compare various schemes of different combinations of variable parameters through hydraulic, thermal and economic calculation, and the calculation process is complicated and is mainly completed through a calculation program of design software of a thermal power plant (the optimization calculation program of the circulating water system). The 'circulating water system optimization calculation program' adopted by the domestic electric power design industry is optimization software identified by the industry, and each unit is provided with 1 condenser as an optimization object: that is, the steam turbine (hereinafter, referred to as a main steam turbine) and the steam turbine for driving the boiler feed pump (hereinafter, referred to as a small steam turbine) share 1 condenser.

However, the prior art is not suitable for the optimization of the circulating water system with the main steam turbine and the small steam turbine respectively provided with the condensers, the optimization of the circulating water system with the main steam turbine and the small steam turbine respectively provided with the condensers in China at present belongs to the technical blank, in the design of the main steam turbine and the small steam turbine which are actually operated together, design parameters caused by specific thermal data of the small steam turbine cannot be obtained in the initial setting stage, so that the design is inaccurate, the optimization of the circulating water system with most of the steam turbines and the small steam turbine respectively provided with the condensers is directly carried out along with the cold end configuration of the main steam turbine or is simply estimated by technical personnel, a cold end configuration combination scheme which is not in accordance with engineering conditions is obtained, serious construction waste and resource loss are caused, and certain potential safety hazards are buried.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine, which can optimize the circulating water system under the condensers respectively arranged on the main turbine and the small turbine.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

a method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine comprises the following steps:

acquiring engineering information, main steam turbine parameters and small steam turbine parameters;

according to the engineering information and the main steam turbine parameters, optimizing and calculating cold end parameters of the main steam turbine with the minimum annual cost as a target to obtain a recommended main steam turbine cold end parameter combination scheme;

according to the recommended main steam turbine cold end parameter combination scheme and the small steam turbine parameters, determining the condenser area and the cooling rate of the small steam turbine through checking calculation;

calculating the comprehensive cooling rate of the condenser shared by the main turbine and the small turbine according to the recommended main turbine cold end parameter combination scheme and the condenser area and the cooling rate of the small turbine;

obtaining an optimal cold end parameter combination of the condenser shared by the main turbine and the small turbine through a shared condenser optimization algorithm according to the comprehensive cooling rate, and determining the cooling tower configuration shared by the main turbine and the small turbine according to the optimal cold end parameter combination of the condenser shared by the main turbine and the small turbine;

and acquiring other parameters of the small steam turbine condenser through a small steam turbine condenser optimization algorithm according to the configuration of the cooling tower shared by the main steam turbine and the small steam turbine, wherein the other parameters of the small steam turbine condenser comprise the backpressure type, the flow type, the type and the length of the cooling pipe bundle and the design flow rate of the small steam turbine condenser.

Further, the engineering information includes: engineering overview, meteorological conditions, economic indicators; the main steam engine parameters comprise type, rated power, exhaust pressure, thermodynamic data of the main steam engine under different working conditions and the relationship between the micro-increase power and the back pressure of the main steam engine.

Further, according to the engineering information and the main steam turbine parameters, the cold end parameters of the main steam turbine are optimized and calculated with the minimum annual cost as a target, and the method for obtaining the recommended main steam turbine cold end parameter combination scheme comprises the following steps:

the method comprises the steps that sensitivity analysis is conducted on main steam turbine parameters, a steam turbine parameter optimization algorithm of thermal power plant design software is used for independently optimizing main steam turbine parts, and an optimal calculation result of a main steam turbine water supply system is obtained;

the method comprises the steps that annual total cost sequencing is conducted on the optimization calculation results of a main steam turbine water supply system, and a recommended main steam turbine cold end parameter combination scheme is obtained and comprises cold end parameters matched with a main steam turbine part; the cold end parameters matched with the main steam turbine part comprise: the area of a cooling tower, the area of a condenser, the cooling rate and the tower outlet water temperature of the cooling tower in each season are matched with the main steam turbine part.

Further, the method for determining the condenser area and the cooling rate of the small turbine through checking calculation according to the recommended main turbine cold end parameter combination scheme and the small turbine parameters comprises the following steps:

taking the tower outlet water temperature of the cooling tower in each season matched with the main steam turbine part as the input of a small steam turbine check algorithm of thermal power plant design software to obtain parameters of a small steam turbine condenser;

taking the small steam turbine condenser parameter and the small steam turbine parameter as the input of a condenser check algorithm of thermal power plant design software to obtain the condenser area and the cooling multiplying power of the small steam turbine; the small steam turbine parameters comprise the design backpressure of the small steam turbine, equipment arrangement and thermal data of the small steam turbine under different working conditions.

Further, the method for calculating the comprehensive cooling rate of the condenser shared by the main turbine and the small turbine according to the recommended main turbine cold end parameter combination scheme and the condenser area and cooling rate of the small turbine comprises the following steps:

and taking the recommended main steam turbine cold end parameter combination scheme and the condenser area, the cooling rate and the design backpressure of the small steam turbine as the input of a comprehensive cooling rate optimization algorithm of thermal power plant design software, and obtaining the comprehensive cooling rate of the condenser shared by the main steam turbine and the small steam turbine and the sum of the condensing capacities of the main steam turbine and the small steam turbine.

Further, the method for obtaining the optimal cold end parameter combination of the main steam turbine and the small steam turbine shared condenser through the shared condenser optimization algorithm according to the comprehensive cooling multiplying power comprises the following steps:

taking the comprehensive cooling multiplying power and the sum of the condensing capacities of the main steam turbine and the small steam turbine as the input of a shared condenser optimization algorithm of the design software of the thermal power plant to obtain the optimal cold end parameter combination of the shared condenser of the main steam turbine and the small steam turbine; the preferable cold end parameter combination of the condenser for sharing the main steam turbine and the small steam turbine comprises the cooling tower area, the tower outlet water temperature, the specification of a circulating water pipe ditch and the pipe diameter of a circulating water pipe of the condenser for sharing the main steam turbine and the small steam turbine.

Further, the method for determining the configuration of the cooling tower shared by the main turbine and the small turbine according to the preferred combination of the cold end parameters of the condenser shared by the main turbine and the small turbine comprises the following steps: and according to the tower outlet water temperature of the cooling tower in each season matched with the main steam turbine part, searching a cold end configuration with basically equivalent water temperature and high fire proximity in the preferred cold end parameter combination of the condenser for the main steam turbine and the small steam turbine, and determining the configuration as the cooling tower configuration for the main steam turbine and the small steam turbine.

Compared with the prior art, the invention has the following beneficial effects:

1. the method of the invention adopts the steps of independent optimization of the cold end equipment of the main steam turbine part, check calculation and determination of individual parameters of the small steam turbine part, setting of comprehensive cooling multiplying power, matching of the cooling tower of the main steam turbine and the shared cooling tower and the like, different combinations and hydraulic, thermal and economic calculation and comparative analysis are carried out on the cold end equipment of the main steam turbine and the small steam turbine, including the area of a condenser, the area of the cooling tower, the cooling multiplying power of circulating water, the pipe diameter of water supply and drainage and the like, so as to obtain the most economic cold end configuration combination scheme which is consistent with engineering conditions, therefore, the configuration of a circulating water system under the condenser is optimized when the main turbine and the small turbine are respectively arranged, the problem of inaccurate design in the design of the combination of the main turbine and the small turbine in actual operation is solved, the blank of the method for optimizing the design of the circulating water system for the combination of the main turbine and the small turbine in the prior art is made up, and the construction waste and the resource loss of a thermal power station are reduced;

2. the invention obtains a most economical cold end configuration combination scheme which is consistent with engineering conditions by solving various main steam turbine cold end parameter combination schemes, and through hydraulic, thermal and economic calculation and comparative analysis, thereby minimizing the annual cost related to the investment and the operating cost of cold end equipment, simultaneously ensuring the maximum output of a steam turbine unit, namely ensuring that the back pressure of a steam turbine does not exceed the maximum allowable value during full load operation under the condition of the highest cooling water temperature, and improving the safety of thermal power station construction.

Drawings

FIG. 1 is a flow chart of the present invention;

fig. 2 is the main steam turbine back pressure-power curve of the second embodiment.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The first embodiment is as follows:

the embodiment provides a method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine, which comprises the following steps as shown in fig. 1:

acquiring engineering information, main steam turbine parameters and small steam turbine parameters;

according to the engineering information and the main steam turbine parameters, optimizing and calculating cold end parameters of the main steam turbine with the minimum annual cost as a target to obtain a recommended main steam turbine cold end parameter combination scheme;

according to the recommended main steam turbine cold end parameter combination scheme and the small steam turbine parameters, determining the condenser area and the cooling rate of the small steam turbine through checking calculation;

calculating the comprehensive cooling rate of the condenser shared by the main turbine and the small turbine according to the recommended main turbine cold end parameter combination scheme and the condenser area, the cooling rate and the design backpressure of the small turbine;

according to the comprehensive cooling rate, obtaining a preferred cold end parameter combination of the condenser for the main steam turbine and the small steam turbine through optimization calculation, and determining the configuration of a cooling tower for the main steam turbine and the small steam turbine according to the preferred cold end parameter combination of the condenser for the main steam turbine and the small steam turbine;

and obtaining other parameters of the condenser of the small turbine through optimization calculation according to the configuration of the cooling tower shared by the main turbine and the small turbine.

Example two:

the embodiment provides a method for optimizing a circulating water system under condensers respectively arranged on a main turbine and a small turbine. In this embodiment, the calculation program ("optimal calculation program for circulating water system") based on design software of a thermal power plant on the market at least includes a shared condenser optimization algorithm, a small steam turbine condenser optimization algorithm, a steam turbine parameter optimization algorithm, a small steam turbine check algorithm, and an integrated cooling rate optimization algorithm.

The principle of the general circulating water system optimization method is as follows: the steam condenser is supplied with water through a water supply system in the thermal power plant so as to achieve the purpose of condensing steam. From the turbine point of view, the water supply system corresponds to the cooling system. From a thermodynamic point of view, the condensing unit and the water supply system function as cold sources. The condenser is used as a core, the low-pressure cylinder of the steam turbine is connected in the condenser, and the water supply system is connected outside the condenser, so that a cold end of the thermodynamic system of the power station is formed.

The back pressure Pk of the condenser can be determined from its saturated steam temperature tc, which is calculated as follows:

tc＝t_w1+δt+Δt

the temperature rise delta t of the circulating cooling water is related to the enthalpy difference delta h of the exhaust steam and the condensed water and the circulating cooling multiplying power m, delta t is delta h/(4.1868 m), and the heat transfer end difference delta t is delta t/[ exp (KA/1163W) -1 ].

As can be seen from the above formula, the back pressure of the condenser and the inlet water temperature t of the cooling water_w1The relationship also relates to the circulating water amount W, that is, the cooling rate m, the condenser area a, the material of the condenser pipe, and the low-pressure cylinder type. The above parameters jointly determine the cold end parameters of the steam turbine.

The main ways of improving the heat efficiency of the unit are to improve the initial parameters of the steam and reduce the cold end parameters (the exhaust temperature and the exhaust pressure) of the steam turbine. When the initial parameters of the steam turbine are fixed, the cold end parameters of the steam turbine are reduced, the ideal steam enthalpy drop of the steam turbine can be increased, the cold source loss is reduced, and the heat efficiency of circulation is improved.

The back pressure P of the condenser is reduced to obtain low steam parameters_kThe temperature of the outlet water of the cooling tower (the inlet water temperature (t) of the cooling water) can be reduced_w1) And reducing the temperature difference (circulating water temperature rise delta t) between the inlet and the outlet of the condenser and the heat transfer end difference delta t of the condenser to realize the following steps:

(1) by increasing the cooling tower area, the cooling tower exit water temperature tw1 may be reduced. However, the area of the cooling tower is increased, the geometric height of the water supply is correspondingly increased, and the power consumption of the circulating water pump is increased; meanwhile, the area of the cooling tower is increased, which leads to the increase of the manufacturing cost of the cooling tower.

(2) Increasing the cooling rate m, i.e. increasing the amount of circulating water, can reduce the temperature difference Δ t, which, however, will result in an increase in the power consumption of the circulating water pump motor, the cost of equipment, the cost of circulating water pipe ditches and the cost of buildings (structures).

(3) The end difference can be reduced by increasing the heat exchange area of the condenser, but the manufacturing cost of the condenser is improved.

Therefore, it is easy to see that the design of the cold end parameters of the steam turbine is related to the design and selection of the condenser and the water supply system. The design and selection of any one of the equipment and system parameters in the "cold end" cannot be isolated from the design and selection of the other factors. A reasonable parameter is a combination of the parameters that are just right in terms of each factor. This right combination of parameters is obtained only by "cold end" (circulating water system) optimization.

The optimization calculation method adopts an annual cost minimum method recommended by the design specifications of the water conservancy projects of the thermal power plant. The method integrates two factors of investment and production cost, and calculates by combining time factor, namely, the capital construction investment of each scheme is considered into the profit factor, and is converted into the cost of equal payment at the end of each year within the service life, and the annual running cost is added to form the annual cost of the scheme. The least annual cost among the various solutions is an economically desirable solution.

The objective function established at the minimum annual cost is as follows:

NF＝P·AFCR+AP-AT

in the formula: NF is annual cost (ten thousand yuan), P is total investment current value (ten thousand yuan), AFCR is annual fixed cost rate (%), AP is annual circulating water pump electric charge (ten thousand yuan), AT is annual micro-power gain electric charge (ten thousand yuan); the P & AFCR is the cost converted into the equal payment AT the end of each year in the economic service life by the capital investment of the water supply system of the power plant, and can also be called as the annual fixed allocation cost, and the AP-AT is the annual operating cost.

Sensitivity analysis is mainly to calculate some important but uncertain factors in the set variation range so as to research and analyze the degree of influence of the factors on the scheme. The sensitive economic indexes in the cold end optimization design mainly comprise a reduction coefficient of a micro-increase power fee price, power generation cost (coal price) and annual fixed allocation rate (investment profit rate).

The method includes the steps of carrying out different combinations on variable parameters of cold end equipment, such as condenser area, cooling tower area, circulating water cooling rate, water supply and drainage pipe diameter and the like, and obtaining the most economical cold end configuration combination scheme which is consistent with engineering conditions through hydraulic power, thermal power and economic calculation and comparative analysis. Under the combined scheme, the annual cost related to the investment and the operation cost of cold end equipment can be minimized, and the maximum output of the steam turbine unit can be ensured, namely, the backpressure of the steam turbine is ensured not to exceed the maximum allowable value in full-load operation under the condition of the highest cooling water temperature.

The embodiment is further described below with reference to engineering examples, and the specific steps are as follows:

step 1: acquiring engineering information, wherein the engineering information comprises: engineering overview, meteorological conditions, economic indexes, main steam turbine parameters and thermal data of small steam turbines under different working conditions.

Overview of the engineering: A2X 1000MW ultra-supercritical unit is newly built in a certain power plant, a main steam turbine and a small steam turbine in a main plant are respectively provided with condensers, wherein the small steam turbine is configured in 2X 50%, each small turbine is independently provided with a condenser, and the maximum continuous power is not less than 20.1 MW. The main workshop external circulation cooling water supply system comprises a natural ventilation cooling tower, a circulation water pump room, a water inlet and return pipe ditch and the like, wherein each unit is provided with an ultra-large natural ventilation cooling tower, and 1 circulating water inlet pipe and 1 circulating water return pipe are respectively arranged.

Meteorological conditions: the historical observation data of the weather station in the administrative area where the plant is located are shown in table 1.

TABLE 1 weather parameters for each season

The wet bulb temperature of 10% in summer is 27.5 ℃, and the corresponding meteorological parameters are as follows: the dry bulb temperature is 30.8 ℃, the relative humidity is 79 percent, and the atmospheric pressure is 1006.2 hPa.

Economic indexes are as follows:

1. service power fee: 0.26 yuan/degree (780 yuan/ton coal price)

2. Slightly increasing unit price of electric power fee: 0.221 yuan/degree (0.85 is calculated according to the reduction coefficient)

3. Condenser unit area price: 600 yuan/m²

4. The cost of the cooling tower is shown in table 2.

TABLE 2 Cooling tower cost table

5. The economic service life of the power plant: 20 years old

6. And (3) capital recovery rate: 10.2% (based on 8% recovery on investment.)

7. Annual maintenance charge rate: 2 percent of

8. Annual fixed share rate: 12.20 percent

9. Annual utilization hours: 5500 hours

Main steam engine parameters:

(1) the type: ultra supercritical, twice intermediate reheating double back pressure and condensing type;

(2) rated power: 1000 MW;

(3) the exhaust pressure: 4.8 kPa;

(4) the thermal data of the main steam turbine under different working conditions are shown in tables 2-3;

(5) the relationship graph of the micro-power and the back pressure of the main steam turbine is shown in figure 2.

TABLE 3 summary of thermodynamic data of main engine under different working conditions

The main steam turbine and the small steam turbine condenser are different in form, the main steam turbine condenser is generally double-backpressure and single-flow, the small steam turbine condenser is single-backpressure and double-flow, and the specification and the length of the pipe bundle are different, so that 2 types of condensers cannot be regarded as 1 type of condenser. Thermal data of small steam turbine under different working conditions:

the small steam turbines are configured according to 2 x 50%, each small steam turbine is independently provided with a steam condenser, and the thermal data of the small steam turbines under different working conditions are shown in a table 4.

Table 4 thermal data summary table for different working conditions of small steam turbine

Step 2: the method comprises the steps of performing sensitivity analysis on main steam engine parameters, and utilizing a circulating water system optimization calculation program to independently optimize a main steam engine part to obtain an optimal calculation result of a main steam engine water supply system; and sequencing annual total cost of the optimization calculation results of the water supply system to obtain a recommended main steam turbine cold end parameter combination scheme, wherein the main steam turbine circulating water system design scheme comprises optimal cold end parameters such as cooling tower area, condenser area, cooling multiplying power, cooling tower outlet water temperature in each season and the like matched with the main steam turbine.

The results of the optimization calculations are shown in table 5.

TABLE 5 Main steam turbine Water supply System optimization calculation result ranking

Through sensitivity analysis, a recommended main steam turbine cold end parameter combination scheme is as follows:

the design cooling multiplying power is 54 times, each unit is provided with 1 natural ventilation cooling tower with the water spraying area of 11500 square meters, and each unit is provided with 1 square meter condenser. The condenser is double back pressure and single flow, the cooling tube bundle adopts 304 stainless steel tube D22X 0.5, the tube bundle length is 13.4m, the designed flow rate is 1.9m/s, and the water head loss of the condenser is 7.5 m. Under the recommended working condition, the water temperature of each season of the cooling tower is shown in a table 3-2.

TABLE 5 Water temp. gauge for cooling tower outlet equipped with host

Water spray area of cooling tower	11500m2
		10% of the summer conditions water temperature (DEG C) out of the tower	31.50
Temperature of water leaving the tower in summer (DEG C)	28.86
		Water temperature (DEG C) in spring and autumn	20.62
Winter water temperature (DEG C) of tower outlet	12.30
		Mean temperature of water leaving the column (. degree.C.)	20.59

And step 3: the annual average tower outlet water temperature and the tower outlet water temperature in 10% of conditions in summer of the table 5 are utilized, the condenser parameters of the small steam turbine are determined through checking calculation, and the condenser area and the cooling water quantity of the small steam turbine are determined through checking calculation in combination with the designed backpressure and the equipment arrangement of the small steam turbine: the design cooling multiplying power is 65 times, the design backpressure is 5.5kPa, and the small steam turbine condenser area is 2500m²。

And 4, step 4: 1 set of virtual condensers (a main steam turbine and a small steam turbine share the condenser), a comprehensive cooling rate (the cooling rate of the virtual condenser) is calculated to be 55 according to a recommended main steam turbine cold end parameter combination scheme and small steam turbine condenser parameters, and the calculation results are shown in a table 6.

TABLE 6 Cooling multiplying factor calculation Table

Item	Steam quantity (t/h)	Enthalpy difference (kJ/kg)	Cooling rate	Amount of Cooling Water (m)3/h)
					Main steam engine	1412.75	2279.86	54	76288
Small steam engine (2 pieces total)	149.15	2370.20	65	9695
					Merging	1561.90	2288.49	55	85983

And 5: setting 1 virtual condenser by utilizing a circulating water system optimization calculation program, wherein the condensed steam discharged into the condenser is the sum of the condensed steam of a main steam turbine and a small steam turbine, and the cooling rate adopts the comprehensive cooling rate, so that the optimal calculation result of the full water supply system is calculated and obtained and comprises the optimal cold end parameter combination of the condenser shared by the main steam turbine and the small steam turbine; the preferable cold end parameter combination of the condenser for sharing the main turbine and the small turbine comprises the area of the cooling tower, the temperature of the water discharged from the tower and the specification of a circulating water pipe ditch.

Table 7 shows the total water supply system optimization calculation results calculated by the "circulating water system optimization calculation program". This step has confirmed the optimum pipe diameter of the circulating water system at the same time: at this time, it can be seen that, under the comprehensive cooling rate of 55 times, the optimal circulating water pipe diameter is DN 3800.

TABLE 7 Total Water supply system optimization calculation results

Step 6: comparing and recommending the main steam turbine cold end parameter combination scheme (table 5), and in the total water supply system optimization calculation result (table 7)Finding the cooling tower configuration with basically equivalent or approximate water temperature, namely the scheme of the serial number 3, determining the cooling tower water spraying area 13000m shared by the main steam turbine and the small steam turbine²。

And 7: and optimizing other parameters of the condenser of the small turbine according to the hydraulic balance principle. According to the principle that the resistance of the pipe section of the main steam condenser is equal to that of the pipe section of the small steam condenser, the parameters of the small steam condenser are derived by pushing down the cooling water amount of each part: the condenser is single-backpressure and double-flow, a cooling tube bundle adopts 304 stainless steel tubes D20 multiplied by 0.5, the length of the tube bundle is 7.7m, and the designed flow speed is about 2 m/s. The invention optimizes the resistance of each section to distribute water according to the respective water quantity requirement by respectively arranging the condensers on the main steam turbine and the small steam turbine and arranging the water inlet and outlet pipelines, thereby overcoming the functional defect of uneven water distribution of the existing design software of the thermal power plant.

And 8: to summarize: determining the configuration of the circulating water system according to the relevant conclusions of the steps: the design cooling multiplying power of a main steam turbine is 54 times, the design cooling multiplying power of a small steam turbine is 65 times, and the comprehensive cooling multiplying power is 55 times; ② each unit is provided with 1 water spraying area of 13000m²The natural draft cooling tower of (1); the diameter of the water supply and drainage pipe of the circulating water is DN 3800; fourthly, 1 main engine of each unit is provided with 61000m²Each small steam turbine is provided with 1 2500m condenser²A condenser. Wherein the main steam condenser is double-backpressure and single-flow, the cooling tube bundle adopts a 304 stainless steel tube D22 multiplied by 0.5, the length of the tube bundle is 13.4m, and the designed flow rate is about 1.9 m/s; the small steam turbine condenser is single-backpressure and double-flow, a cooling tube bundle adopts 304 stainless steel tubes D20 multiplied by 0.5, the length of the tube bundle is 7.7m, and the designed flow speed is about 2 m/s.

The optimization calculation process of the circulating water system of the thermal power plant at the present stage is relatively complicated and is mainly completed through a calculation program. The 'optimization calculation program of a circulating water system' commonly adopted in the domestic power design industry cannot be directly used for the optimization calculation of a water supply system with condensers respectively arranged on a large steam turbine and a small steam turbine. The method comprises the steps of independently optimizing cold end equipment of a main steam turbine part, checking and calculating a small steam turbine part to determine individual parameters, setting a virtual condenser and comprehensive cooling rate, matching a cooling tower of the main steam turbine with a shared cooling tower, optimizing other parameters of the small steam turbine condenser according to a hydraulic balance principle and the like, and performing different combinations and hydraulic, thermal and economic calculation and comparative analysis on the cold end equipment of the main steam turbine and the small steam turbine, including the area of the condenser, the area of the cooling tower, the cooling rate of circulating water, the diameter of water supply and drainage and the like, so as to obtain the most economical cold end (circulating water system) configuration which is consistent with engineering conditions.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.