Feasibility Analysis of Condenser Half Condensing Half-low Vacuum Heat Supply

Feasibility Analysis of Condenser Half Condensing Half-low Vacuum Heat Supply
Core Tips: (Inner Mongolia Linfa Te 2nd Power Plant, Yulinhaote, Inner Mongolia 026000) Yulinhaote II Power Plant transforms pure condensing steam turbine units into low-vacuum heating units, using condensate: steamer half pure condensation half-surface low-vacuum heating Operation mode, test and actual operation, all indicators of the unit are within the specified range.

(Inner Mongolia Linfate Second Power Plant, Yulinhaote, Inner Mongolia 026000) Yulinhaote Second Power Plant transformed a pure condensing steam generating unit into a low-vacuum heating unit, and used a condensing steamer half-side pure condensation half-surface low-vacuum heating operation mode. After testing and actual operation, all the indicators of the unit are within the stipulated range, and the heating parameters have also met the design requirements, and have achieved good social and economic benefits.

Condenser; Half-surface low vacuum; Circulating water heating With the development of thermal power generating units to helium-parameter large-capacity units, medium-low parameter units may be eliminated, but changing them to heating units not only reduces the level of automation. Poor economic benefits and other unfavorable factors also provide a new way for the development of enterprises.

Xilinhot Second Power Plant changed three 12MW pure condensing steam generating units to low-vacuum heating units in 2000-08 respectively. The total design heating area is 1 million m2, and the return pressure is 0.56 Sichuan. 12MPa, the supply and return water temperature is 65/50 for the return flow of 3185t/h, the heat network pump has the flow rate of 3x2 and the thermal area is about 560,000m2. The maximum electric load when the single machine is heating is 1 The existing problems are One generator provides heat and the return water temperature is 65/55. As the return temperature of the heating network rises, the exhaust pressure of the rear cylinder increases, the turbine drop decreases, and the power is reduced. The power of the generator is only 7MW, which reduces the unit efficiency.

In the cold season (September 9 weather), heating from one generator and two heaters fails to meet the design requirements for heating; if two generators are used to supply heat at the same time, the return temperature of the heating network is too low. The power is only 13MW. With this mode of operation, not only the load on the unit is limited, but also there is no cooling water for the auxiliary machines of the 2 machines, and the water tower has no good antifreeze measures.

2 Operation mode 2.1 Operation mode Condenser half surface pure condensation Half surface low vacuum heating operation mode is to switch the condenser half surface of low-vacuum heating unit to low-vacuum circulating water heating, and the other half is connected to the circulating water system, ie A 75MW circulating pump is started, and part of the circulating water is supplied to the auxiliary machines of the two machines for cooling. A part of the condenser is heated by the half of the condenser to serve as supplementary water for the heating network, and the remaining direct pipes on the pool are used to dissipate heat. This will not only improve the replenishment temperature of the heating network, but also solve the freezing problem of the water tower.

The difference between the inlet water temperature on both sides of the condenser shall not exceed 35. If the temperature difference is too large, the inlet water temperature difference on both sides of the condenser may be reduced by adjusting the through gate of the water tower, and the temperature of the circulating water on the pure condensation side shall be 2.2. Advantages: In the initial and final stage of heating, by adjusting the temperature and flow rate of the condensate side condensate of the condenser, the parameters of the heating network can be guaranteed, and the power generation load of the heating unit will not be limited.

In the middle and cold seasons of heating, when a single machine is used for low-vacuum heating, and the water supply temperature of the heating net does not meet the design requirements, the condensation half-surface low-vacuum heating of the condenser half of one unit can be increased. Meeting the requirements, it also reduces the time required to invest in spike heaters, thereby saving a lot of new steam.

Under the condition that the normal heating of the heating network is ensured, the low-vacuum heating unit can perform half-side cleaning of the condenser without stopping the machine.

The main supply and return pipe of the heating system is about 4100t/h for 1million m1 return flow, and 2850t/h for the rated flow rate of the condenser. Such a large volume of water passes through the condenser to make the water in the condenser. The side pressure is reduced, the flow rate is increased, the backwater pressure of the heat network rises, and the pressure difference between the supply and return water decreases. If the heating system increases the operation of the half-surface condenser of one machine, the flow area of ​​the return flow of the heating network will increase, the pressure difference between the supply and return water will increase, and the heating quality can be improved.

Zhang Guohua (1969-), male, Inner Mongolian, graduated from the thermal power professional and assistant engineer of North China Electric Power University, and is currently working from a steam turbine.

3 Safety analysis and verification 3.1 Condenser body expansion The condenser of the low-vacuum heating unit adopts half-side pure condensation half-surface heating, which may cause vibration of the unit and looseness of the copper tube expansion port of the condenser.

The following is a quantitative analysis of the thermal expansion of the condenser.

When the steam turbine uses low-vacuum heating, the condensate temperature is increased from 42.7 SC to 80 condensor and the expansion of the exhaust cylinder increases, which may cause vibration of the unit. Especially during the start-up of the rushing car, the temperature of the exhaust cylinder will become even more turbulent. More likely. The initial state of room temperature is 20T, the bottom of the condenser to the throat is 4m, due to the friction of the exhaust steam when rushing. The influence of blast loss caused the exhaust steam temperature to rise to 90t. Calculated according to the linear expansion (ZL linear expansion, L metal length, - temperature change, r-linear expansion coefficient h, the above data can be substituted into: ZL = 3.36mm (based on Technical Regulations for Design of Steam Water Pipes in Thermal Power Plants (KfUxIO4/t).

Condenser half-side pure condensation half-surface low-vacuum heating unit and low-vacuum heating unit, if the same vacuum in the condenser, the exhaust temperature of the rear cylinder is also the same. Therefore, when the condenser is half-side condensation and half-surface low-vacuum heating, the expansion volume of the condenser body is the same as the expansion volume of the condenser of the low-vacuum heating unit.

From the above calculations, it can be seen that the maximum expansion of the condenser body is about 3.36mm. Since the connecting piece of the condenser and the rear cylinder adopts a cold-pull connection method, the cold-drawn value is 3mm, and the condenser is at the bottom during normal operation. It is supported by eight springs, which can completely eliminate the stress on the rear cylinder caused by the expansion of the condenser. Therefore, it does not cause vibration of the unit.

3.2 Condenser Expansion Difference Condenser Copper Tube Linear Expansion Coefficient = 20) (1 (/ (based on coefficient of expansion 012x10/1: Condenser brass length L = 4570mm, steam turbine exhaust temperature 80t, condenser Pure condensation side of the circulating water out of the population temperature of 25/15 low vacuum heating side of the return water temperature of 65/50 condenser copper tube temperature than the circulating water temperature of about 2 condenser shell temperature ratio of exhaust The temperature is lower than 5: the expansion difference between the condensate side shell and the copper tube of the condenser: the expansion difference at the outlet side is 4L=a/f=2.74mm for the expansion of the population side. Condenser low-vacuum heating side shell Difference of expansion with copper pipe: expansion difference at the water supply side is soil=-2.00mm; expansion difference at the return water side is 41=0/=-0.46mm. From the above results, it can be seen that the condenser shell and the copper pipe The maximum expansion difference is 2.74nun. Due to the arcuate arrangement of the copper tubes in the condenser, supported by the spacers, the middle lift 篼 4mm, the elongation of the copper tube is 30%, the stress generated by this differential expansion can be along the two side of the fistula Expanding in the middle does not have much effect on the bulge.

Through the above analysis, the use of condenser half-side condensation half-low vacuum heat supply will not affect the safe operation of the unit.

3.3 Test Results “05-07” The condenser of No. 2 heating unit was tested. The vibration and various indicators of the unit were within the specified range, and the heating parameters also met the design requirements. At the end of May, when the minor repair was performed on the No. 2 machine, the connection of the condenser expansion port and the condenser and the rear cylinder were examined, and no abnormalities were found.

4 Actual Operation 2001-10-01―10-09, the No. 1 engine condenser is operated with half-side pure condensation half-surface low-vacuum heating mode, and the supply and return water temperature of the heating network is 55/451, and the feedwater pressure is 0.45. /0.14MPa. By adjusting the flow rate of the heating network, the maximum electric power of No.1 generator can still reach 2MW while satisfying the demand of thermal users. At both the 10-09-11-11 and No.1 machine condensers The human heating network operates with low vacuum heating.

The machine is equipped with low-vacuum heating, and No. 2 condenser is operated with half-side condensation and low-vacuum heating. The temperature of the heating network is 65/51 for the return pressure of 0.56/0.12 MPa. While the parameters meet the design requirements, the maximum electric power of the two generators can reach 21MW. In the same period of 2000, the maximum electric power of the two machines was only 13MW when the No. 1 and No. 2 machines were connected to a heating network for low-vacuum heating. Due to the relative increase in spare capacity of Ximeng Online, it greatly eased the power shortage at the peak of electricity consumption.

5 Benefit Analysis 5.1 Social Benefits After entering the heating period, the condenser of the heating unit adopts a half surface pure condensation half-surface low-vacuum heating operation mode, which can adjust the temperature and flow of the condensate side circulating water according to the heating temperature and the online The load determines the load of the unit, and the maximum power of the generator can reach 12MW. Therefore, while ensuring the quality of heating, the demand for power supply and heating during the peak period of electricity consumption in Xilinhot is greatly eased, and the road limit is reduced. Electricity times.

5.2 The economic benefit is single unit heating, instead of half condenser semicondensing and low vacuum heating of condenser, the daily peaking time is 8 hours, the average generating capacity is increased by 3000kW per hour, and the cost of power generation is 0.275 yuan/kWh. The generating capacity is: (212-60)x8hx3 equivalent to RMB 1.003 million. ) In 2001, the time spent on heating network heaters was 43 days later than in 2000, saving about 1 800 tons of new steam, delaying the investment of heating network heaters.

6 It is recommended to use low-vacuum circulating water for small units in isolated power grids. Although heat loss can be effectively used, the quality of heating should be ensured while considering whether the unit achieves the best economic load because the unit is providing heat to the outside. It is at the cost of reducing electricity generation. Therefore, during the heating period, the flow rate and heat required by the heating network should be comprehensively considered so that the heating unit can operate in a reasonable mode of operation.

Zheng Tikuan. Thermal power plant. Chongqing University Press, 1998. Guidelines for the selection of condenser tubes for thermal power plants. Water Conservancy and Electric Power Publishing House, 1984. Editor: Wang Jinli Leng Yu Gu Power (Group) Co., Ltd. Guiding Directors in 2002 Work Guidelines and Views I. The guiding ideology of work is based on Deng Xiaoping Theory and the "Three Represents" thinking. Implement the important speech of July 1st, the 5th and 6th Plenum of the 15th CPC Central Committee, the 7th Party Congress of the autonomous region, and the spirit of the Central Economic Work Conference, and firmly grasp the historical opportunities of Western Development, West-to-East Electricity Transmission, and effectively transform the work The style of work is to meet the party’s 16th convened as an opportunity to closely integrate China’s strategy of adding WTO to the process of accelerating the industrialization and urbanization of the autonomous region. It adheres to the principle of safe production, uses economic efficiency as the center, and develops the overall situation. We will solidly build first-class power companies as carriers, accelerate informationization, fully implement technological innovation as a breakthrough point, deepen reforms, advance with the times, pursue excellence, and be bold in pioneering, and strive to achieve the leap-forward development of Inner Mongolia Electric Power in the new century.

II. Constitutional production in 2001 In 2001, under the guidance of corporate restructuring, commercialized operation, and legalized management business strategy, the completed electricity sales amounted to 23.58 billion kW-h, a year-on-year increase of 7.53%, and completed 101.64% of the economic and trade assessment targets; Industrial added value reached 2.674 billion yuan; total profits and taxes exceeded 1 billion yuan for the first time, of which profit was 180 million yuan, an increase of 2.2% year-on-year, completing an assessment value of 100.56%; asset-liability ratio was 64.87%, 0.13 percentage points lower than the control value of 65%; The value-added rate of maintenance was 100.2%; the total labor productivity of production companies was 128,690 yuan/person-year, an increase of 7.09% year-on-year. III. Production target in 2002 The company's production target in 2002 was: Electricity generation completed 26.49 billion kWh, an increase of 3.9% year-on-year. Line loss rate of 6.98%, power supply coal consumption 395g/kWh, electricity tariff recovery rate of 100%. Electricity sales 25.54 billion kWh, an increase of 8.3%. The business objectives are: to achieve profits of 1.12 billion yuan, an increase of 7.4%, profit of 200 million yuan, The year-on-year increase was 11.7%, taxes were 922 million yuan, a year-on-year increase of 6.5%, and labor productivity of industrial enterprises was 135,125 yuan/person-year. The basic construction goal is to arrange fixed-asset investment of 5.48 billion yuan and put into operation an installed capacity of 423,400 kW. The new variable-capacity child 220kV 1.173 million kVA, 110kV 813,500 kVA, added 220kV transmission line 431km, new heating area 929 Million m2. rely on science and technology development step by step.

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