Key words: 300MW; sub-critical unit steam turbine; flow rate optimization; application ID: Adoi: 10.19311 / j.cnki.16723198.2017.28.084
In this paper, the author of a company turbine steam turbine valve flow optimization test and analysis as an example, through specific analysis, elaborate flow of the entire process of optimization. The steam turbine is a subcritical two-cylinder turbine with two high-pressure main steam valves and six high-pressure regulated steam valves. The existing problem is that after the valve is closed, the load on the left intake valve fluctuates too much. After two times of transformation, it has not been completely solved. Therefore, the article analyzes the problem more specifically to solve the problem of overloading the steam turbine valve, Promote their optimal utilization.
1 Turbine System Brief Introduction Turbine valve management is the core of DEH system management, which determines the operational safety of the system. In the process of operation to ensure the turbine system design is reasonable, in the event of any unreasonable design conditions, will result in the performance of steam turbine units decreased, increased load, and the resulting huge lateral steam flow, resulting in axial position and bearing work The nature of the change, the final result of the bearing asymmetry, decreased stability, severe cases may occur when the tile or trip phenomenon. Turbine use sequential valve operation, but the design will affect its sensitivity and stability. The poor curve of the unit will lead to its performance is affected, showing that there are many influencing factors of the steam turbine. In the process of design and management, all the necessary optimization schemes need to be taken to solve the problems of large swing amplitude and poor performance of primary FM. At present, the 300MW subcritical unit is a relatively common type of steam turbine, and the industry is more concerned with the optimization analysis of the whole process. Some units have valve management failure, high temperature and high wattage, with the two measuring points of the same watt, there is a big temperature difference. The unit has a difficult load to be controlled near the total valve position command. There is a big difference in the overlap degree of the valve opening and thus the economy of operation The overall flow characteristics of the unit as a whole difference between the larger AGC caused the ability to reduce regulation. All of these problems will affect the normal operation of the steam turbine and reduce the overall economic benefits of the power plant. Therefore, how to improve the working efficiency of a 300 MW subcritical unit is very important for reducing the cost of the power plant and increasing the output value.
2 door performance optimization test 2.1 single valve control valve flow characteristics of the test test First detected in a single valve under the premise of control, the unit load is 160MW, the main steam pressure in the normal range. Test process gradually increase unit valve flow instructions, an increase, to determine the stability of the generator and main steam pressure, increase the valve flow to 90% or more can stop the test. The test process records the valve flow value under single valve control.
2.2 Sequence valve control valve flow characteristics of the test exit Single-valve control test, enter the sequence valve control test, this time the unit load of 300MW, to maintain the main steam pressure stability, based on the main steam pressure gradually reduce the stability of the unit valve flow The instruction, for each reduction of one level, confirms that all components will enter the next stage after their normal operation. The purpose of the test is to control the operation load of the unit at about 165MW. The test process records the valve flow value under single valve control.
3 flow test analysis 3.1 flow data analysis This article discusses the single-valve control and sequence valve control valve flow characteristics of the two tests, and record the data. Through several tests, it can be proved that the valve linearity curve of the subcritical unit under single-valve control is better and the degree of non-linearity is higher.
3.2 Unit Valve Activity Test Power Fluctuation Reason According to the above data can be analyzed unit power fluctuations in the valve, the use of flow characteristics through the valve test data to determine the characteristics of the test. In the previous inspection, it was found that the power deviation of the unit was large. The dramatic changes in power caused the stability of the unit to be affected, which posed a potential safety hazard. According to the analysis of the vibration source, the reason for this was that the construction site was not properly selected, demand. In addition, the unit valve activity tests are carried out manually, when the unilateral valve activity, the steam flow is still greater than the other ways, the power increased during the experiment. To build a simulation model of steam turbine unit during valve activity test, a thorough examination of changes of valve power and a comprehensive inspection of working conditions points out that the vapor flow controlled by unilateral valve before and after the experiment is basically the same, The conditions can reduce the power deviation, but can not be completely eliminated. Therefore, I think the main reason for the valve activity is delayed off, and the flow rate is too large reference delay is the main reason. When the flow reference value is close to 162.3MW, the two groups of valves are realized to be turned on or off at the same time. In the case of steady conditions, the power deviation is obviously reduced, but the delay closing time should still be controlled reasonably to avoid violent vibration. Therefore, the final confirmation, the unit in the process of through-flow modification and DHE setting using pure manual shut-down, making the shut-off time is too long, thus affecting the use of equipment, valve flow. Change the control mode of the unit to ensure that the DHE of the unit is set up rationally and perform the test in this mode to ensure the normal operation of the unit. In the DHE power automatic mode valve activity test results and shutdown speed test found that the shutdown speed is large, the device power will have a greater change. Gradually reduce the closing speed and found that the closing speed of 0.1% / s, the unit can be relatively stable, the power fluctuation range will be less than 3.5MW, DHE power automatic valve under the condition of the test test balance and found that the power of the device changes and The total valve position instructions, the total valve position command is about equal to 71.5%, the unit is in a relatively stable state, the simulation results are more reasonable. Can be proven by multiple tests.
4 dynamic adjustment test According to the specific test situation, the crew on the issue to make the following adjustments. First, the single-valve adjustment and sequence valve flow adjustment, so that its parameters in a reasonable range. Valve activity test, exit the AGG and coordination control mode, switch DEH mode to power automatically, keep boiler combustion stability. During the operation of the equipment, the deviation of the unit obviously decreased. 28MW before the experiment, the test is 7.5MW, the stability is greatly improved. Running under this power can meet the normal operation requirements of the unit, which can ensure the stability and the reasonable utilization of the traffic. Finally, do adjustment test analysis. According to this test data, the main problems of the unit are as follows: the nonlinearity of the flow characteristic curve of the single valve is slightly higher, the solution strategy is to adjust the flow function of the relative function, the control mode of the valve is DEH setting, valve flow function setting, Test conditions combined selection of factors, you can use the correct control and improve the working conditions to improve the operational stability of the device. In this experiment, the data dynamic test mode should be calculated and planned reasonably, and the new valve flow characteristic function under the single-valve control mode that can theoretically be consistent with the design condition is designed, so that the unit time can be controlled reasonably, Unit check can modify the parameters, modify the operation of the vote after the operation of the valve equipment, and its full DEH power automatic, the boiler is in a stable and safe combustion environment, are the control mode is switched to DEH power automatic, After a year of comprehensive assessment, you can control the power fluctuations in the equipment within a certain range, to ensure its normal operation.
5 Summary 300MW unit steam turbine is one of the important equipment in power plant, its flow optimization is the key to ensure its normal operation. There are many influencing factors during the operation of steam turbines, which is not conducive to the improvement of the overall efficiency of the steam turbine. Therefore, the influencing factors on the flow rate of steam turbine valves are analyzed and the specific optimization methods are proposed to effectively improve the working efficiency of the steam turbine. The author of the unit test research and analysis, through several test results to analyze the reasons for the instability of the flow. After the conclusion, it is found that the delay of the unit is the main reason causing the excessive flow. The influence of the main steam pressure and other factors on the test point during the test is negligible. Therefore, the author puts forward the suggestions for improvement. It is suggested that the unit can be dynamically optimized to ensure its normal operation, especially to ensure DEH system control under different conditions, to ensure the unit's sustainable operation and to improve the unit's operation efficiency.
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