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Key words: thermal power valve machinery; application flow; research foreword:
Thermal power generation plays a dominant role in China's power generation industry and is developing towards large-capacity, high-parameter, and energy-efficient units. From the analysis of current domestic and foreign development trends, competitive technologies for thermal power plants in terms of efficiency, economy and environmental adaptability are aimed at super-critical and ultra-supercritical units, integrated gasification combined cycle units and other high-end thermal power machinery. Generally, the thermal efficiency of small and medium-sized units is about 30%, the thermal efficiency of subcritical large thermal power units is below 38%, and the thermal efficiency of supercritical and ultra-supercritical units can reach 42% to 45%. The thermal power high-temperature high-pressure valve used in the ultra-supercritical unit is very different from the thermal high-temperature high-pressure valve used in the subcritical unit. The high-temperature valve of the ultra-supercritical unit is higher in terms of technical parameters, materials and reliability. Claim.
1. Current status of high-end mechanical unit valves for thermal power 1.1 Domestic status At present, domestic high-end units of thermal power have valves with double-sealed structure; seal ring-packing double-sealed valve (providing a sealing ring at the top of the inside of the bonnet, when the valve is full When opened, the valve head will be pressed against the sealing ring, and the sealing joints of the two will be closely matched); the two-way sealing core valve (the valve core moves along the axis to realize the opening and closing of the valve); the composite ram Large-diameter hard-sealed slab gate valve (the structure includes a valve body, a metal hard seal valve seat, a sub-soft seal ring, a composite ram, and a stem member); a combined sealed fixed ball valve using a combination of a hard seal and a soft seal; There are a combination of a soft seal ring and a metal seal ring to form a double-sealed fire butterfly, a two-way metal hard seal butterfly valve, and the like. In addition, through the two-way internal control balance valve, throttle valve, shuttle valve, buffer valve organic cooperation and mutual matching, forming a whole rotary control valve; from the plug valve, globe valve, thermostatic trap and shut-off valve 4 High temperature and high pressure cock type composite valve composed of two parts; adopting two valve heads of main valve head and auxiliary valve head, and high temperature and high pressure composite valve head stop valve with meandering flow passage in the auxiliary valve head; The inner layer is a titanium steel composite valve of titanium or titanium alloy layer; the outer shell is made of ordinary steel, and the inner liner is made of wear-resistant composite valve cast with wear-resistant material; the valve disc and the valve stem are divided into two bodies, and the valve disc is hinged to the valve body The upper swing type composite valve; and the valve body is provided with a valve flap which can slide in the guide sleeve, and an oil and gas conveying composite valve with an orifice on the side of the valve flap.
1.2 Foreign status In foreign countries, there are double-sealed valves, clean and anti-leakage high-temperature double-sealed valves with cleaning function. The valve has an annular circumferential seal groove on the outer casing between the cylindrical limit surfaces of the joint. In the closed position, the two circumferential grooved, double-sealed, high-purity fluid valves of the two-way sealing valve are constructed of a seal that is used to close the valve by a bluff body through a valve seal seat of a pipe. There is a double-sealed welded valve that adjusts the seat pressure through a seat to ensure internal seals. The external seal is achieved by welding the front surface of the sleeve to the cylindrical sealing surface on the front of the valve body. There is also a double-sealed butterfly valve and a double-sealed ball valve. The ball valve has a double-sealed structure, which allows the butterfly plate in the valve to move upward or downward under high temperature and high pressure without instantaneous movement, and is completely sealed by the elastic material on the butterfly plate. .
1.3 The critical state parameter of supercritical water is 22.115MPa, 374.15 °C. When the water parameter reaches this critical point, the complete vaporization of water will be completed in an instant, that is, at the critical point, between saturated water and saturated steam. There is a two-phase zone where steam and water coexist, and there is no longer a difference between the two parameters. When the unit parameters are higher than this critical state parameter, it is usually called a supercritical parameter unit. Supercritical and ultra-supercritical thermal power units have significant energy saving and environmental improvement effects. Compared with supercritical units, ultra-supercritical units can increase thermal efficiency by 1.2% and save 6000 tons of high-quality coal in one year. Future thermal power construction will mainly focus on the development of high-efficiency and high-parameter supercritical (SC) and ultra-supercritical (USC) thermal power units, which have been widely studied and applied in developed countries.
2. Thermal power valve mechanical application process 2.1 Four major pipeline systems and price situation The high working parameters and high-tech valves in the thermal power generation system are mainly distributed in the four major pipeline systems, namely the main steam pipeline, the main water supply pipeline and the reheater. The cold section hot section pipe and the steam turbine various sections of the extraction pipe, in addition to the high and low pressure bypass system. According to the data, a 600,000 kW supercritical thermal power unit only needs to import 60-90 million yuan for all four major pipeline valves. If all localization is only more than 30 million yuan; one 600,000 kW or 300,000 kW subcritical thermal power The total import of the four major pipeline valves of the unit needs to be 50-70 million yuan. If all the localization is only more than 20 million yuan. According to the current construction of thermal power stations, 30 sets of 600,000 kW supercritical units will be built each year, and all supporting valves for supercritical thermal power units will be imported; 25 sets of 600,000 kW and 300,000 kW subcritical units will be built each year, and some subcritical units will be imported. The four major pipeline import valves need to be more than 2 billion to 300 million yuan.
2.2 Increasing steam parameters to improve steam parameters, the increase in efficiency of thermal power plants can reduce operating costs, but to increase investment, there is an optimization figure between the two. According to German statistics, according to the current price level, the supercritical steam parameters are increased, and the thermal power plant can still receive economic benefits when it invests more than 30 million DM (M) in every 1% improvement in plant efficiency.
According to the data, the net efficiency of the power station with steam parameters of 16.7MPa/538°C/538°C subcritical power station is 418%; the net efficiency of the power station with steam parameters of 25MPa/540°C/560°C supercritical power station is 43.3%; the steam parameter is The net efficiency of the power station of 27MPa/585°C/600°C supercritical power station is 44.4%; the net efficiency of the power station with steam parameter of 30MPa/600°C/620°C supercritical power station is 45.1%; the steam parameter is 31.5MPa/620°C/620°C. The net efficiency of the supercritical power station is 45.5%; the net efficiency of the supercritical power station with steam parameters of 35MPa/700°C/720°C is 47.6%. These data can be used to estimate the impact of increased parameters on plant efficiency.
2.3 Energy saving and emission reduction Because China's current energy use is mainly based on coal, this determines that for a long time in the future, the domestic energy development direction is dominated by coal-fired power generation. At present, the proportion of thermal power in the CLP generator set accounts for 78%. At the high-level forum on power science development held on March 28, 2009, Cao Shudong, deputy director of the Power Department of the National Energy Administration, revealed that the National Energy Administration has begun preparations for the preparation of the “Twelfth Five-Year Plan†and has initiated the development of nuclear power. Special plans, such as planning, will accelerate the development of cogeneration and coal-electricity integration, continue to promote upstream and downstream relations, actively adjust thermal power structure, and promote energy conservation and emission reduction.
At present, the National Development and Reform Commission and the Energy Bureau have also determined that the next step will be to shut down the small thermal power units of 125,000 kW and 200,000 kW, and at the same time, they will no longer have 300,000 kW thermal power units, and will have a large number of 600,000 kW and 600,000 kW or more. Thermal power units, supercritical, ultra-supercritical thermal power units, the so-called "upper and lower pressure". According to the data, China's power industry has a high proportion of thermal power units, and both coal consumed and sulfur dioxide emissions account for more than half of the national total. At the same time, the average coal consumption per kWh of thermal power units is about 60g higher than the international advanced level, and the potential for energy conservation and emission reduction is large. In the thermal power unit, the proportion of small thermal power units with high energy consumption and heavy pollution is relatively high. The small thermal power units with a single unit of 100,000 kW and below account for nearly 30% of the installed capacity of thermal power. This is the energy consumption and pollution emission index of China's power industry. An important reason for the large gap in international advanced levels. If small thermal power units are replaced by large units, annual savings of 90 million tons of standard coal and 1.8 million tons of sulfur dioxide emissions will be reduced. According to the data, the total coal consumption and sulfur dioxide emissions of the national power industry will be reduced by 10% and 13.5% respectively. The increase in the shutdown of small thermal power, "on the big pressure" will inevitably lead to the acceleration of the "Eleventh Five-Year" energy-saving steps.
3. Conclusion Through the design and development of supercritical thermal gate valve and the maturity of related product production technology, the application process of thermal power machinery has been optimized, which not only expands the application range of valve products in the field of thermal power, but also enhances the thermal power valve machinery in China. Competitive ability provides a strong backing for future expansion and development in the field of thermal power.
References [1] Xu Yibin, Wang Ju. Innovative Application of Supercritical Thermal Gate Valves[J]. Electric Power General Machinery, 2009, 7: 56-60.
[2]FANG Jingying, LI Zhipeng, KONG Huashan. Research and Application of Hard Seal Composite Valve for Ultra Supercritical Thermal Power Unit[J]. Power System Engineering, 2013(3), 29(2): 39-41.
Analysis on the application process of thermal power valve machinery
Abstract: This paper introduces the application process, design and development of thermal power valve machinery, focusing on the use of valves in supercritical conditions, the use of valve components and materials in supercritical conditions, and the accounting of the overall cost of valve manufacturing. The structure, main parts and materials, heat treatment, main test items and technical requirements are discussed. The practical application results show that the thermal power valve machinery has been successfully applied to domestic related enterprises, and has achieved very good results, providing reference for the development and design of related valves of thermal power units in the future.
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