Application of Senlan SBH High-voltage Frequency Converter in Boiler Feedwater Pump of 350MW Unit in a Power Plant in Xinjiang
I. Introduction
In the past 10 years, the large-scale promotion of high-voltage variable frequency speed control technology has made tremendous contributions to the energy saving and consumption reduction of the power industry. Domestic thermal power plants have entered the popularization stage in terms of energy-saving auxiliary work machines, and most thermal power companies have begun to change. Ideas, daring to try, made breakthroughs in the reduction of production self-consumption, auxiliary power consumption has been further contained after the use of high-voltage frequency control technology, most of the application of mature loads such as the introduction of fans, circulation Pumps, condensate pumps, etc. have all been transformed, so how to further tap the energy saving potential of auxiliary boilers has become the focus of power companies. In this case, as a large consumer of electricity, frequency conversion energy-saving renovation of the feed pump has become the direction of thinking. ! The temptation to transform:
1 The power of the feed pump is large and the energy consumption is high.
2 Great potential for energy saving. In terms of existing retrofit experience, for units that are not fully loaded, the power saving rate is usually around 20% (there is a direct link with the power generation load).
Although temptation is enough, most companies are cautious and cautious, and they dare not do something. The main reasons are:
1 The load is too important, there is no case, or there is no experience in the guidance. No user dares to make a decision to reform and try. Because once the problem arises, the impact will be very large. This is the main reason.
2 The transformation not only involves the frequency converter, but also involves the mechanical transformation, the frequency conversion manufacturers do not understand, and the machinery manufacturers will not consider. Coupled with the mechanical aspects of the hydraulic coupler transformation and pre-pump transformation is difficult, the reform program is difficult to determine, causing no one to move to the pump.
However, the data show that the world's developed countries have long been the boiler feed pump system as one of the key projects to promote variable frequency speed energy-saving transformation, there are companies in the country to dare to try, which Senlan has the honor to become a user highly-recognized inverter system provider. This paper proposes a new idea for the transformation of the feedwater pump load for the high-power boiler water pump energy-saving retrofit project of Senlan in a power plant in Xinjiang.
Second, project overview
A 5×350MW large-scale coal-fired generating unit was put into operation by a power plant in Xinjiang. The transformation of 10 high-pressure and high-power electric-powered feed pumps in the power plant has become a landmark project for the conversion of the Shenlan feedwater pump. The boiler feed water pump of No. 5 boiler was reformed. After the reform, its high yield and stable performance allowed the customer to make up its mind to renovate the feed pumps of the remaining four units at one time. The project has a total of 10 high-power boiler feed pumps. .
The unit configuration is as follows: a single unit boiler feed water system is equipped with 3 sets of 50% boiler feed pumps, using 2 to 1 standby mode. The feed pump system uses a fluid coupling as a speed control method, in which the feed pump uses the 300TSBII-JB type of the Zhengzhou Power Machinery Plant and the hydraulic coupling is the R16K400M of the German VOITH company. The front pump is a YnKn350/250J pump manufactured by Zhengzhou Electric Power Machinery Plant. The overall system diagram is as follows:
The system consists of a pre-pump, a motor, a fluid coupling (including working oil and lube oil), and a feed pump. The system adjusts the amount of water supplied to the pump through the fluid coupling to meet the boiler according to the unit load changes. The need for production system water supply.
It can be seen that if frequency conversion speed regulation and energy saving reform are required, it is necessary to consider the operation mode of the pre-pump after the speed regulation, whether the liquid couple after transformation of the frequency conversion is reformed, and the problem of DCS control after transformation.
Third, the system transformation program
In the face of complex systems and difficult reforms, Senlan conducted a field research for nearly a month. Combined with many years of experience in power plant applications, he conducted numerous on-site exchanges and technical communication with users, and finally confirmed a set of best practices. Actual transformation solution at the site, while providing technical support throughout the process, guide the user to complete the entire system frequency conversion transformation, the transformation program is: a single unit will change the two operating pumps to variable frequency drive, the remaining one standby pump without modification, still using liquid Even speed control. The transformation of the mechanical part includes the transformation of the fluid coupling and the forward pump, the electrical part including the motor side and the transformation of the DCS control system. The contents of the transformation are many. There are many details to be considered. The scheme is as follows:
3.1 Converter Retrofit Program
The project adopts a drag-and-restriction scheme:
This scheme is a typical one-by-one solution. QS1 and QS2 are isolation switches. The function of the isolation cabinet: There are obvious breakpoints for easy maintenance and ensure the safety of people and equipment.
3.2 Mechanical Transformation Program
3.21. Pre-pump retrofit: According to on-site data collection statistics, and carefully analyze the analysis of the water supply system operation data collected on site, and finally determine the pre-pump without the need for transformation of the program, to break the original "change frequency will change the pre-pump" Arbitrary strategy, and ultimately proved by practice, the power plant's front-mounted pump has not been changed, the frequency conversion drive can still meet the current requirements of the inverter under various operating conditions after the conversion, no cavitation. Save a large part of the cost for the user and the greatest possible change is not the original mature design, reduce the risk of transformation.
3.2.2 For the disadvantages of the liquid coupling speed regulation, the liquid coupling speed control function is cancelled and the speed increaser box is connected to ensure that the system energy-saving rate is maximized. The transformation includes the transformation of the liquid coupler body and the transformation of the lubricating oil road. Finally, on the premise of ensuring the stable operation of the motor and the feed pump, it maximizes the energy saving potential.
3.3 Control System Reconstruction Program
Combining the original control features, the inverter control system adopts a dedicated controller, analyzes the possible risks of various adjustment states of the boiler, and seamlessly connects with the original system, and uses logic strategies to circumvent every possible unexpected situation. The system risk was controlled to a minimum, and the site passed several tests to finally ensure the stability and reliability of the entire system.
Fourth, the transformation effect
1. After one month of on-site construction, the project was formally put into operation. At the beginning of the investment, it received the expected energy-saving effect. The energy-saving rate was as high as more than 20%, and the plant electricity rate was reduced by 1 percentage point. Received the user's consistent high praise.
2. Extensive tests on the site's control and reliability have been conducted. Finally, it is proved that the system can still maintain the original standby mode after the transformation and does not affect the reliability of the water supply system, and it does not trigger any possible transformation risks. The project is implemented successfully. End.
Rebuild the scene:
V. Summary
The breakthrough transformation of the high-power boiler feed pump marks the new height of the frequency conversion energy-saving transformation of large-scale thermal power generating units. Its remarkable energy-saving effect, stable and reliable product performance, and perfect solution are the driving forces for the successful implementation of the transformation and are the domestic power. The company has provided new ideas for energy saving and consumption reduction. The project has played a benchmark role in the Xinjiang region. Senlan has once again confirmed the strong technical strength as a domestic leading inverter company.
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