CN105736071A - Valve management optimization method based on steam distribution mode switchover for 200MW heat supply unit - Google Patents

Abstract

A valve management optimization method for a 200MW heating unit based on steam distribution mode switching relates to a switching method, in particular to a valve management optimization method for a 200MW heating unit based on steam distribution mode switching. In order to solve the problem that the current steam distribution optimization scheme for 200MW heating units does not consider the influence of the deviation of the optimal valve position caused by the change of steam extraction volume, that is, the same steam distribution optimization curve is adopted under different steam extraction volumes, and the efficiency of the high-pressure cylinder of the steam turbine The optimal problem cannot be achieved. The specific steps of the present invention are as follows: according to the actual situation of the power plant equipment, set two steam distribution modes; carry out load raising and lowering experiments on the heating unit, obtain relevant experimental data, and calculate the efficiency of the high-pressure cylinder of the unit under different steam distribution modes ;According to the efficiency curves of high-pressure cylinders under different steam distribution modes; determine the corresponding steam distribution mode according to the relative flow of main steam; judge whether the change of main steam flow exceeds the margin. The invention belongs to the field of steam turbine power generation.

Description

Valve management optimization method for 200MW heating unit based on switching of steam distribution mode

technical field

The invention relates to a switching method, in particular to a valve management optimization method of a 200MW heating unit based on switching of steam distribution modes, and belongs to the field of steam turbine power generation.

Background technique

A steam turbine is a rotating machine powered by steam and converts the energy of steam into mechanical work. It is widely used in modern large-scale power generation systems. In order to meet the user's actual demand for electricity consumption, the steam turbine must frequently adjust its power to keep the motor power in balance with the changing load of the outside world. The most direct and effective way to change the power of the steam turbine is to control its steam intake. When the steam intake changes, the power of the steam turbine will also change accordingly, that is, the steam distribution of the steam turbine.

Generally speaking, there are two ways to distribute steam to a steam turbine, namely, single valve and multi-valve (multi-valve can also be called sequence valve). Single valve refers to the way that when steam enters the high-pressure cylinder of the steam turbine, each high-pressure regulating valve enters steam at the same time. At this time, the command and opening of each high-pressure regulating valve are the same. Multi-valve refers to the way that a single high-pressure regulating valve is used to gradually enter steam when the steam turbine enters. The command and opening of each high-pressure regulating valve are different. Inlet area. Due to the non-linear characteristics of the valve flow, adjust the valve opening speed, opening sequence, opening overlap, etc. In theory, the single-valve steam distribution and multi-valve steam distribution methods each derive infinitely many steam distribution methods. Considering various restrictions in practice, in order to make the unit operate safely, stably, or with the highest efficiency, there are usually only limited steam distribution methods.

During the actual operation of the unit, according to different requirements such as safety, stability, and economy, it is necessary to switch between these limited steam distribution methods in time. For example, under normal circumstances, the unit operates in a single-valve mode when starting up to ensure that the cylinder rotor is heated evenly and the unit operates flexibly; in daily operation, the unit adopts a multi-valve mode to ensure higher efficiency and economy of the unit. In the multi-valve mode, different steam distribution modes correspond to different efficiency curves. In order to maximize the efficiency of the high-pressure cylinder and the economical operation of the unit, it is necessary to switch between various multi-valve steam distribution methods.

Integrating the various demands of unit operation, the optimal steam distribution mode corresponding to the different power of the unit and the switching point between each steam distribution mode can be obtained, that is, the switching curve of steam turbine steam distribution mode, as shown in Figure 3.

In order to maintain the stability of the heat load provided by the unit and the safety and stability of the unit operation during the heating period of the 200MW heating unit, and some 200MW heating units do not have a high-pressure bypass system, the unit maintains constant pressure operation in principle.

The total load of the unit is the sum of the electrical load and the heating load of the unit. Under normal circumstances, the electric load of the unit is basically in a stable state, so there is a phenomenon that determining the heat load means determining the total load. If the steam extraction volume of the unit changes, the total load of the unit will also change with the trend of the steam extraction volume. For example, when the steam extraction heat supply increases, the comprehensive flow command of the unit will increase accordingly, and the high-profile door will also respond accordingly. action to increase the main steam flow into the turbine.

The usual working range of a 200MW heating unit is about two valve points to three valve points. In this working range, the efficiency of the high-pressure cylinder of the unit varies greatly under different steam distribution methods, which affects the overall thermal economy of the unit. . Due to the change of steam extraction, the opening of each valve of the unit will also change. According to the characteristics of the efficiency of the sequence valve, the unit may work at the optimal valve position before the steam extraction changes, but when the steam extraction changes Finally, if the valve command of the unit changes, the throttling loss of a certain valve may increase, and the efficiency of the high-pressure cylinder will drop significantly.

The steam turbines in modern large and medium-sized power plants are controlled by a digital electro-hydraulic control system (DEH). Each steam inlet valve is controlled by an electric signal and driven by a high-pressure oil motor. The management of the steam inlet valve is an important function of the DEH system. The concept of valve management is proposed based on the consideration of improving the thermal efficiency of the unit under partial load. Since the power of the unit is directly proportional to the steam intake, the power output must be changed by adjusting the opening of the steam intake valve at partial load.

Contents of the invention

The present invention aims to solve the problem that the current steam distribution optimization scheme for 200MW heating units does not consider the influence of the deviation of the optimal valve position due to the change of steam extraction volume, that is, the same steam distribution optimization curve is used under different steam extraction volumes, and the high-pressure cylinder of the steam turbine The problem that the efficiency cannot be optimal, and then a valve management optimization method for the 200MW heating unit based on the switching of steam distribution mode is proposed.

The technical scheme that the present invention takes for solving the above problems is: the specific steps of the switching method described in the present invention are as follows:

Step 1. According to the actual situation of the power plant equipment, set two steam distribution methods: the set steam distribution method is diagonal steam distribution, and the setting principle is: the first valve group is two diagonal valves, and the second valve group is another The lower cylinder valve, the third valve group is another upper cylinder valve;

Step 2. Carry out load-up and down-load experiments on the heating unit, obtain relevant experimental data, and calculate the efficiency of the high-pressure cylinder of the unit under different steam distribution methods:

The high pressure cylinder efficiency is defined as Among them, the main steam enthalpy value h ₀ can be found through the main steam temperature T ₀ and pressure P ₀ , the exhaust enthalpy value h ₁ can be found through the high-pressure cylinder exhaust temperature T ₁ and pressure P ₁ , and the ideal state exhaust enthalpy value h _1s can be used The main steam entropy S ₀ obtained through the main steam temperature T ₀ and pressure P ₀ and the exhaust temperature T ₁ of the high-pressure cylinder are found;

Step 3. According to the high-pressure cylinder efficiency curves under different steam distribution modes, obtain the switching boundary of the steam distribution mode, so that the application of each steam distribution mode can be extended to each area;

Step 4. Determine the corresponding steam distribution method according to the relative flow of the main steam: when the determined point of the relative flow of the main steam falls within the area of the first steam distribution method, select the first steam distribution method; when the relative flow of the main steam is determined When the point falls in the area of the second steam distribution mode, the second steam distribution mode is selected, and the relative flow rate of the main steam is defined as

Step 5. Determine whether the change of the main steam flow exceeds the margin. If it exceeds the margin, the new steam distribution mode is determined by the main steam flow rate; if it does not exceed the margin, the original steam distribution mode remains unchanged.

The beneficial effects of the present invention are: 1. On the basis of the existing steam turbine steam distribution mode, the present invention considers the optimization of the steam turbine steam distribution mode under the flow rate of heat supply and air extraction, and further improves the high-pressure cylinder efficiency during the operation of the steam turbine; 2. , the present invention can realize on the basis of satisfying specific performance requirements (such as safety and stability under a certain heating and extraction steam flow rate), and optimize the combination of different steam distribution modes, so that the high-pressure cylinder efficiency when the steam turbine is running Further improvement; 3. The present invention sets the main steam flow margin, which avoids fluctuations in the main steam flow value, and frequent switching of steam distribution modes leads to frequent actions of valves; 4. The present invention extends the application range of each steam distribution mode to specific In the region, the problem of insufficient data (unable to obtain the temperature and pressure data of the main steam and the exhaust temperature and pressure of the high-pressure cylinder under all main steam flow rates) was overcome.

Description of drawings

Figure 1 is a schematic diagram of the steam structure layout of the four regulating valves of the steam turbine. In Figure 1, 1-No. 1 valve, 2-No. 2 valve, 3-No. 3 valve, 4-No. 4 valve, 5-steam pipeline, 6-control valve;

Figure 2 is a schematic diagram of the nozzle structure layout of the four regulating valves. In Figure 2, 1-No. 1 valve, 2-No. 2 valve, 3-No. 3 valve, 4-No. 4 valve, 7-No. 1 valve nozzle group, 8- No. 2 valve nozzle group, 9-No. 3 valve nozzle group, 10-No. 4 valve nozzle group;

Figure 3 is a schematic diagram of valve opening rules for multi-valve steam distribution, 1-No. 1 valve, 2-No. 2 valve, 3-No. 3 valve, 4-No. 4 valve;

Figure 4 is a schematic diagram of the valve nozzle layout of the 200MW heating unit, that is, No. 1 nozzle group has 13 nozzles, No. 2 nozzle group has 13 nozzles, No. 3 nozzle group has 12 nozzles, and No. 4 nozzle group has 14 nozzles;

Figure 5a is a schematic diagram of the valve opening process of the 200MW heating unit steam distribution mode 1 in the load increase and decrease experiments;

Figure 5b is a schematic diagram of the valve opening process of the 200MW heating unit steam distribution mode 2 in the load-up and down-load experiments;

Figure 6a is the valve opening sequence diagram of the steam distribution mode 1 of the 200MW heating unit. Due to the missing part of the experimental data, the valve opening sequence diagram after the missing data is corrected is Figure 6b;

Figure 7a is the valve opening sequence diagram of the steam distribution mode 2 of the 200MW heating unit. Due to the missing part of the experimental data, the valve opening sequence diagram after correcting the missing data is shown in Figure 7b;

Figure 8 is the efficiency curve of the high-pressure cylinder under the two steam distribution modes of the 200MW heating unit;

Figure 9 is a schematic diagram of the intersection points of the high-pressure cylinder efficiency curves under the two steam distribution modes of the 200MW heating unit, where A, B, and C are the intersection points of the high-pressure cylinder efficiency curves under the two steam distribution modes;

Figure 10 is a schematic diagram of the switching boundary of the two steam distribution modes of the 200MW heating unit, in which the steam distribution mode 1 is adopted in the I area, and the steam distribution mode 2 is adopted in the II area;

Figure 11 is a layout diagram of high-profile nozzle nozzles of a supercritical 350MW heating unit, that is, No. 1 nozzle group has 25 nozzles, No. 2 nozzle group has 24 nozzles, No. 3 nozzle group has 24 nozzles, and No. 4 nozzle group has 25 nozzles. nozzles;

Figure 12 is a schematic diagram of the high-pressure cylinder efficiency under two steam distribution modes of a supercritical 350MW heating unit.

detailed description

Specific implementation mode 1: This implementation mode is described with reference to Figures 1 to 4. The valve management optimization method for 200MW heating units based on the switching of steam distribution mode described in this implementation mode is realized through the following steps:

Step 1. According to the actual situation of the power plant equipment, set two steam distribution methods: the set steam distribution method is diagonal steam distribution, and the setting principle is: the first valve group is two diagonal valves, and the second valve group is another The lower cylinder valve, the third valve group is another upper cylinder valve;

Step 2. Carry out load-up and down-load experiments on the heating unit, obtain relevant experimental data, and calculate the efficiency of the high-pressure cylinder of the unit under different steam distribution methods:

The high pressure cylinder efficiency is defined as Among them, the main steam enthalpy value h ₀ can be found through the main steam temperature T ₀ and pressure P ₀ , the exhaust enthalpy value h ₁ can be found through the high-pressure cylinder exhaust temperature T ₁ and pressure P ₁ , and the ideal state exhaust enthalpy value h _1s can be used The main steam entropy S ₀ obtained through the main steam temperature T ₀ and pressure P ₀ and the exhaust temperature T ₁ of the high-pressure cylinder are found;

Step 3. According to the high-pressure cylinder efficiency curves under different steam distribution modes, obtain the switching boundary of the steam distribution mode, so that the application of each steam distribution mode can be extended to each area;

Step 4. Determine the corresponding steam distribution method according to the relative flow of the main steam: when the determined point of the relative flow of the main steam falls within the area of the first steam distribution method, select the first steam distribution method; when the relative flow of the main steam is determined When the point falls in the area of the second steam distribution mode, the second steam distribution mode is selected, and the relative flow rate of the main steam is defined as

Step 5. Determine whether the change of the main steam flow exceeds the margin. If it exceeds the margin, the new steam distribution mode is determined by the main steam flow rate; if it does not exceed the margin, the original steam distribution mode remains unchanged.

In step 2 of this embodiment, the load lifting and lowering tests are to perform the load lowering process first under the determined sequence valve opening sequence: the unit closes the third valve group to fully closed under the fully open state of the four valves, and then closes the The second valve group is closed to fully closed, and then the first valve group is partially closed; in the process of increasing the load: the first valve group is opened to fully open, and then the second valve group is opened to fully open, and then the third valve group is opened. Turn on the group to fully open, and keep it for a period of time until the parameters of the unit are stable.

During the load-up and down-load test, the load change of the unit generally should not exceed 0.5% of the rated load of the unit per minute. For a 200MW heating unit, the load change during the load-up and down-load test should not exceed 1MW/min, because There is an obvious dynamic effect in the steam turbine unit. If the load changes too fast, the high-pressure cylinder efficiency calculated from the measured results will have a phenomenon that the efficiency curves of the process of raising and lowering the load do not overlap. In order to ensure the implementation effect of this method , so the load change is limited. Carry out load-up and down-load tests on the unit, and record the main steam temperature and pressure, high-pressure cylinder exhaust temperature and pressure data during the whole process; the schematic diagram of the specific experimental process is shown in Figure 5a and Figure 5b.

In step 3, the steam distribution optimization curves of different steam turbines are known, and the switching point of the steam distribution mode is obtained, which represents the relative flow at the switching point of the steam distribution mode. In theory, n=2, but the actual working condition of the unit is different from the ideal state deviation, the final number of switching points needs to be determined by actual data;

Divide the working range of the heating unit, and the two high-pressure cylinder efficiency curves appear to rise alternately in the image with the relative flow as the abscissa and the high-pressure cylinder efficiency as the ordinate. If a certain steam distribution method in a certain area The efficiency of the lower high-pressure cylinder is higher than that of the high-pressure cylinder under another steam distribution method, so the steam distribution method with higher efficiency of the high-pressure cylinder is adopted in this area.

In step 4, set the relative flow margin △G _c , with the change of the relative flow, the switching rules of the steam distribution mode are as follows:

1. If the relative flow G<G _n +△G _c →G>G+△G _c ①, the steam distribution mode does not correspond to the current area, then the steam distribution mode is switched to the corresponding steam distribution mode in the area, G in the formula ① Indicates the actual relative flow of the main steam in the DEH system of the unit, and G _n indicates the selected nth switching point;

2. If the relative flow G>G _n -△G _c →G<G-△G _c ②, the steam distribution mode does not correspond to the current area, then the steam distribution mode is switched to the corresponding steam distribution mode in the area, G in the formula ② Indicates the actual relative flow of the main steam in the DEH system of the unit, and G _n indicates the selected nth switching point.

Since the relative flow values between switching points are not much different, and it is necessary to ensure that the valve group will not move frequently due to the fluctuation of the relative flow of the main steam, the relative flow margin △G _c is generally taken to be no more than 1%-1.5%.

Specific implementation mode 2: This implementation mode is described in conjunction with Fig. 1 to Fig. 4 . The two steam distribution modes in step 1 of the valve management optimization method for a 200MW heating unit based on the switching of steam distribution mode described in this embodiment mode are:

The first steam distribution method: the first valve group is No. 1 valve 1 and No. 3 valve 3, the second valve group is No. 2 valve 2, and the third valve group is No. 4 valve 4;

The second steam distribution method: the first valve group is No. 2 valve 2 and No. 4 valve 4, the second valve group is No. 1 valve 1, and the third valve group is No. 3 valve 3.

The efficiency curve of the high-pressure cylinder is calculated by using the temperature and pressure of the main steam and the exhaust temperature and pressure data of the high-pressure cylinder collected in the load-up and down-load tests under the above two steam distribution methods.

According to the obtained high-pressure cylinder efficiency curves under the two steam distribution modes, three switching points A, B, and C of the two steam distribution modes are obtained, as shown in Figure 9. According to the method in step 3, A, B, and C The relative flow points corresponding to the three intersection points are used as the switching boundary of steam distribution mode, and I and II are the areas where steam distribution mode 1 and steam distribution mode 2 are adopted, respectively, as shown in Figure 10.

In this embodiment, the steam distribution mode optimization curve of the steam turbine under each relative flow rate is obtained through experiments, and the switching point of the steam distribution mode is determined;

According to the switching point, two basic rules are applied to determine the optimization scheme of the steam distribution mode of the steam turbine considering the influence of the steam extraction;

Design switching logic in DEH to realize the optimization scheme of steam distribution mode of steam turbine considering the influence of steam extraction

Other components and connections are the same as those in the first embodiment.

Example

Combining with the transformation example of a 200MW heating unit and Figures 4 to 10, the steam distribution mode switching method is described. The two steam distribution modes in the first step of the 200MW heating unit valve management optimization method based on the steam distribution mode switching in the implementation mode for:

The first steam distribution method: the first valve group is No. 1 valve 1 and No. 3 valve 3, the second valve group is No. 2 valve 2, and the third valve group is No. 4 valve 4;

The second steam distribution method: the first valve group is No. 2 valve 2 and No. 4 valve 4, the second valve group is No. 1 valve 1, and the third valve group is No. 3 valve 3.

Use the above two steam distribution methods to do the load increase and decrease tests. The specific experimental process is shown in Figure 5a and Figure 5b. The valve opening sequence diagrams of the two steam distribution methods are shown in Figure 6b and Figure 7b. The two steam distribution methods The sequential valve function blocks are shown in Table 1 and Table 2, where Fx represents the comprehensive flow command (%), and Fy represents the opening degree (%) of each high-profile door.

Table 1 Steam distribution mode 1 sequence valve function block

Table 2 Steam distribution mode 2 sequence valve function block

Through the data of main steam temperature and pressure and high pressure cylinder exhaust temperature and pressure data collected during the experiment, the efficiency curve of the high pressure cylinder is calculated, as shown in Figure 8.

According to the obtained high-pressure cylinder efficiency curves under the two steam distribution modes, three switching points A, B, and C of the two steam distribution modes are obtained, as shown in Figure 9. According to the method in step 3, A, B, and C The relative flow points corresponding to the three intersection points are used as the switching boundaries of the steam distribution mode, which are G ₁ , G ₂ , and G ₃ , respectively. Areas I and II are the areas using steam distribution mode 1 and steam distribution mode 2, respectively, as shown in Figure 10 Show.

According to the high-pressure cylinder efficiency curve, G ₁ = 79%, G ₂ = 86%, G ₃ = 90.7%, flow margin △G _c = 1%, compared with the basic steam distribution mode switching principle, the specific steam distribution mode switching principle for:

1. If the relative flow rate G<80%→G>80%, if the steam distribution method does not correspond to the steam distribution method 2 adopted in the current area, the steam distribution method will be switched to the steam distribution method 2;

2. If the relative flow G>78%→G<78%, if the steam distribution mode does not correspond to the steam distribution mode 1 adopted in the current area, the steam distribution mode will be switched to steam distribution mode 1;

3. If the relative flow G<87%→G>87%, if the steam distribution method does not correspond to the steam distribution method 1 adopted in the current area, the steam distribution method will be switched to the steam distribution method 1;

4. If the relative flow rate G>85%→G<85%, if the steam distribution method does not correspond to the steam distribution method 2 adopted in the current area, the steam distribution method will be switched to the steam distribution method 2;

5. If the relative flow G<91.7%→G>91.7%, if the steam distribution method does not correspond to the steam distribution method 2 adopted in the current area, the steam distribution method will be switched to the steam distribution method 2;

6. If the relative flow G>89.7%→G<89.7%, if the steam distribution method does not correspond to the steam distribution method 1 adopted in the current area, the steam distribution method will be switched to the steam distribution method 1;

After the 200MW heating unit was transformed by switching the steam distribution mode, under the same relative flow rate, the power after the transformation of the unit has been significantly improved compared with the power before the transformation, indicating that the overall efficiency of the heating unit has been significantly improved. See Table 3 for specific power data.

Table 3 Comparison of effects before and after optimization

The 350MW heating unit was tested for load increase and decrease, and after data processing, it was found that the efficiency curves of high-pressure cylinders under different steam distribution methods also have the characteristics of high-pressure cylinder efficiency curves similar to those of 200MW heating units. This method can also be applied to 350MW heating unit, that is, this method has certain versatility. The schematic diagram of unit nozzle layout and the efficiency diagram of high-pressure cylinder under different steam distribution methods are shown in Figure 11 and Figure 12.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but as long as they do not depart from the technical solution of the present invention, according to the technical content of the present invention Within the spirit and principles of the present invention, any simple modifications, equivalent replacements and improvements made to the above embodiments still fall within the scope of protection of the technical solutions of the present invention.

Claims (2)

1. based on the 200MW thermal power plant unit management valve optimization method of distribution way of steam switching, it is characterised in that: the described 200MW thermal power plant unit management valve optimization method based on distribution way of steam switching realizes as follows:

Step one, according to electric power factory equipment practical situation, set two kinds of distribution way of steam: the distribution way of steam set joins vapour as diagonal angle, setting principle is: the first valve group is two diagonal angle valves, and the second valve group is another lower cylinder valve door, and the 3rd valve group is another upper cylinder half valve；

Step 2, thermal power plant unit is carried out ascending, descending load test, it is thus achieved that relevant experimental data, the high pressure cylinder efficiency of unit under different distribution way of steam is calculated:

High pressure cylinder efficiency is defined asWherein main steam enthalpy h₀By main steam temperature T₀, pressure P₀Check in, aerofluxus enthalpy h₁By high pressure cylinder delivery temperature T₁, pressure P₁Check in, perfect condition aerofluxus enthalpy h_1sUtilize by main steam temperature T₀, pressure P₀The main steam entropy S checked in₀With high pressure cylinder delivery temperature T₁Check in；

Step 3, according to the high pressure cylinder efficiency curve under different distribution way of steam, obtain distribution way of steam handoff boundary, make the application extension of each distribution way of steam in regional；

Step 4, determine corresponding distribution way of steam according to main steam relative discharge size: when the point that main steam relative discharge is determined drops in the region of the first distribution way of steam, then select the first distribution way of steam；When the point that main steam relative discharge is determined drops in second in the region of distribution way of steam, then selecting the second distribution way of steam, main steam relative discharge is defined as

Step 5, judge that main steam flow changes and whether exceed nargin, if it exceeds nargin, then determined new distribution way of steam by main steam flow；If less than nargin, then keep original distribution way of steam constant.

2. according to claim 1 based on the 200MW thermal power plant unit management valve optimization method of distribution way of steam switching, it is characterised in that: two kinds of distribution way of steam in step one are:

The first distribution way of steam: the first valve group is a valve (1) and No. three valves (3), and the second valve group is No. two valves (2), and the 3rd valve group is No. four valves (4)；

The second distribution way of steam: the first valve group is No. two valves (2) and No. four valves (4), and the second valve group is a valve (1), and the 3rd valve group is No. three valves (3).