Abstract: Various water-saving and energy-saving measures are widely implemented in power project construction. Especially in the preliminary design phase of power plant, from technical scheme design to equipment model selection, from environmental protection to labor safety, water conservation, energy saving and environmental protection are always emphasized. In order to ensure that the power plant from the beginning of construction to the power plant put into operation the design of advanced technology. Environmental protection and energy saving, power plant development to create the necessary conditions. This paper mainly discusses the design of power plant water supply system energy-saving measures to promote the application of energy-efficient circulating water pump
Key words: high efficiency, energy saving, economical flow rate, pump performance curve
Natural ventilation cooling tower, circulating water pump, circulating water pipeline and pipeline attachments are important components of circulating water system in power plant. It is of great significance to study the system plan to determine the optimal system configuration in the preliminary design of power plant, which can reduce the construction cost.
The most important part of the design of circulating water system is the reasonable choice and configuration of natural ventilation cooling tower and circulating water pump. In the construction of circulating water system, they have the highest investment cost, the most complex construction and the greatest impact on the total investment of the power plant. Directly affect the unit cost of power engineering construction and plant investment recovery period.
The optimal design of the water supply system is the basis for the selection of the system solution. Among them, the annual cost of the circulating pump motor is the most important factor affecting the design of the water supply system. Under the premise of ensuring the safety of turbine running at full capacity, how to reduce the annual cost of electric motor is worth every engineering designer's thinking.
This article will face the above issues for research. Starting from reducing the annual cost of the motor, the working efficiency of the circulating pump and the motor is studied. Under the premise of meeting the various operating conditions of the turbine (including the pure condensing condition, the maximum pumping condition and the rated pumping condition), the circulating pump Equipped with motor reactive power, improve motor efficiency.
In recent years, with the advent of the country's new round of economic construction climax, a large number of 135MW domestic EHV and intermediate reheat units have been built all over the country. In Gansu Jinchuan Company Thermal Power Plant, Shandong Huatai Thermal Power Plant, Shandong Liyan Power Plant, Xuzhou Power City Power Plant and Shandong Binzhou Weiqiao Thermal Power Plant, we have designed 16 135MW units to select the circulating water pump in circulating water system of 135MW unit. Long-term economic security operation for the purpose of promoting the use of energy-efficient circulating pump.
1, efficient energy-saving circulating pump profile
1.1 High-efficiency energy-saving circulating pump Overview:
Most domestic circulating water supply systems of 100MW, 125MW and 135MW units adopt the conventional arrangement of one unit with two circulating pumps, and this configuration mode conforms to the technical regulations and norms of thermal power plants and also meets the requirements of power system industry "Hydraulic Technical Regulations", widely used in power plant design.
Economic analysis of power plant construction projects found that thermal power plants using a conventional two-pump circulating water system layout of the higher operating costs, there are some shortcomings in the design mainly in:
Circulating pump design point deviation from the system operating parameters, the pump efficiency is not high.
The circulating pump that has been put into operation and found that the circulating power plant is generally existed in the power plant operating efficiency except for part of the time most of the time circulating pump is not running high efficiency, most of the time the pump efficiency is only about 60%, it is clear that it does not belong to the pump High efficiency range.
Pump operation is less sensitive to changes in the flow of the circulatory system
For a turbine with a single working condition, the cooling water volume of the turbine condenser fluctuates greatly with the annual seasons. For the steam turbine running in a variable working condition, the cooling water quantity of the system is greatly reduced along with the increase of steam turbine extraction volume. The thermal power plant using a conventional two-pump mode setting exists for most of the year running a water pump insufficient water supply capacity of two pumps is too large, the pump is difficult to regulate the operation is not conducive to the formation of the most favorable steam turbine vacuum , In vain to waste electricity, in order to fundamentally solve the problem of circulating water pump configuration and system flow changes, improve the operating efficiency of circulating water pump, production and development of energy-efficient water pump is inevitable.
1.2 efficient energy-saving circulating pump features
In this paper, starting from the high efficiency and energy saving of circulating water pump, this paper introduces the characteristics of a new type of G series circulating water pump, and gives an example of the application of G48Sh new circulating water pump in 135MW unit design.
G48Sh new circulating pump design parameters and plant circulating water system, the actual resistance parameters and kiss, the pump running more efficient. More than 100 G48Sh circulating pumps put into operation were sampled and tested. The actual efficiency of G48Sh pumps was 84-88%. Compared with the conventional mode of 135MW units, the actual efficiency of one machine with two pumps of the same model 48Sh-22 was improved 25%.
G48Sh new circulating pump with motor using bipolar number, double speed operation. According to the annual season different steam turbine condenser cooling water volume changes drastically, by adjusting the motor motor pole number and speed motor output power changes, so that the circulating pump water supply, water pressure changes. Increased the flexibility of the system adjustment, to minimize plant electricity load.
For example, a G48Sh high-efficiency energy-saving pump runs in high speed in summer and 3000 tons / hour more than two 48Sh-22 pumps at the same pump power. In winter, one G48Sh high efficiency energy-saving pump runs at low speed, Under the condition that the system water supply is quite high, the power of the pump equipped motor is reduced from 1080KW to 680KW, the power drop is over 30%, equivalent to 2.3 million kWh saved per pump per year.
The introduction of G48Sh high efficiency and energy saving circulating water pump optimizes the hydraulic conditions of the circulating water system and widens the range of the high efficiency section of the pump to ensure that the actual operating efficiency of the circulating water pump at two different rotational speeds is not less than 85% The efficiency of work.
The introduction of the G48Sh high efficiency and energy saving circulating water pump has changed the conventional design concept of capacity configuration mode of two turbines with two circulating pumps (hereinafter referred to as "one machine and two pumps") and proposed the design concept of large capacity and small pump configuration. Large pumps have high speed, low speed, small pumps also have high speed, low speed, which combined a variety of pump operating conditions, and each other standby. Basically meet the steam turbine working conditions change conditions. High efficiency and energy saving circulating pump horizontal pump casing, operation, maintenance is very convenient.
1.3 efficient energy-saving circulating pump configuration
In Gansu Jinchuan Thermal Power Plant, Shandong Huatai Thermal Power Plant, Shandong Liyan Power Plant, Xuzhou Power City Power Plant and Shandong Binzhou Weiqiao Thermal Power Plant, we have designed 18 sets of 135MW domestic ultra-high pressure and intermediate reheat units. These power plants have a common characteristic, basically enterprises spontaneous use, enterprises in addition to a stable power demand but also have a certain heating load, heating load fluctuations in large enterprises. Making the circulating water system in the power plant circulating water drastically changed. In the absence of heating load, the heating unit is basically operating in pure condensing conditions, which often occur in the summer of each year. With the advent of winter, the heating load and living heating load increase, so that the unit heating load greatly increased, in extreme cases, the unit will exceed the rated pumping conditions. Most of these enterprises are located in North China, Northeast China and Northwest China, heating longer, with a fixed heating period of 4-6 months each year, a few years longer heating period. For such a long period of time, the unit operates with steam extraction and heating, which makes the circulating flow of power plants run at a lower time for a long time. Considering the long-term economic operation requirements of the power plants, the water supply flow of the circulating water pump and the high efficient range of the lift require a long time.
Taking 135MW heating unit as an example: When steam turbine VWO condition is in summer, steam condensing capacity of steam turbine is 324.17t / h and circulating capacity of one unit is 19640t / h; when steam turbine rated extraction condition, Steam condensate volume of 223.36t / h, a unit of 12274 t / h of circulating water; steam turbine at maximum extraction conditions, condensing steam turbine capacity of 142.66t / h, the unit of circulating water is 4700 t / h. Circulating water system flow from 4700t / H - 19000T / H changes, according to the conventional capacity of the pump is arranged to meet the minimum heat load of the cooling water unit configuration circulating pump flow 9800T / H-11700T / H, water supply head about 18.0- 21.5 meters, two pumps run in parallel.
In the rated extraction conditions, a pump running, due to the reduction of circulating water, the system's water resistance drops, the pump flow 12274T / H, head will drop to 15.0-16.0 meters, the steam turbine in the maximum extraction conditions, To meet the requirements of circulating water system to run a pump, due to a substantial reduction in water supply, the pump head greatly increased, resulting in a cooling tower water directly to increase the water flow device with a sink, water flow in the filler on the heat exchange The reduction of time reduces the cooling effect of the cooling tower. Of course, the effect of reducing the heat exchange between the filler and the filler does not draw too much attention in the winter, but the pump operation will definitely move out of the efficient range of the pump. The working efficiency of the pump is reduced and the reactive power of the motor is wasted. As circulating pump motor power 710KW, long-term operation is not conducive to power plant energy conservation. In this case requires a new pump configuration mode, it is necessary to meet the large flow, high lift requirements but also to meet the low flow requirements of low lift, large and small pumps and high and low speed mode of operation. This configuration mode emphasizes large pumps high flow, high speed in accordance with the system maximum flow of choice, water flow and head to meet the system requirements. Small pumps, high flow rate, high speed in accordance with the system flow of 60% of the choice, as a large pump standby pump; Large pump low flow, low speed selection Small pumps in accordance with the high flow rate, high speed selection, as a small pump speed reserve Pump; small pump low flow, low speed in full accordance with the system minimum flow, and system requirements of the supply lift choice, this time no other spare pump. This pumping unit through the changes in conditions, automatically adjust the pump size, small and high-speed pumps, low-speed operation, so that the pump water supply basically meet the requirements of the system of circulating water.
2 efficient energy-saving circulating pump usage
Shandong Shiliquan Power Plant 2 125MW units equipped with four 48SH-22 with the same type of circulating pump operation. Most of the time in a year there is a single water supply system does not run enough water supply flow, 2 sets of parallel operation of the pump power plant has increased too much, the inefficient pumps affect the economic operation of the unit. In October 1998, the 4 # pump (48SH-22) was replaced with the G48SH high-efficiency energy-saving pump. After the high-efficiency energy-saving pump was put into operation, the power plant commissioned the Guangdong Electric Power Research Institute to conduct the energy-efficient pump performance test. The test results show that: The actual operating efficiencies at high and low speeds were as high as 87.78% and 86.11%, respectively, which were 28.26% and 26.5% higher than those of the other unopened 48SH-22 pumps respectively. The power consumption was significantly reduced and the operation of the new pump was flexible.
Two sets of 125MW units in Yunfu Power Plant in Guangdong use a secondary circulation water supply system. Four 48SH-22 circulating pumps of the same type are arranged in the system. The operation modes of the pumps are three pumps in summer and two in other seasons. Because of the low flow rate and low efficiency of a single pump during operation, the circulating pump was changed into an efficient G48SH pump in June 1998. High efficiency G48SH pump put into operation, the power plant commissioned by the Guangdong Electric Power Research Institute of the new pump efficiency test, the test results show that: the new pump at high speed flow of up to 16537t / h, the actual operating efficiency as high as 87.78%, the motor power 1002KW; Low-speed flow of 13080t / h, the actual operating efficiency of 86.12%, the motor power 646KW, pump operating conditions and operating conditions basically consistent with the unit. The actual operation of the original pump flow 14400t / h, efficiency 59.62%, motor power 1089KW; the maximum efficiency of 70% when the flow 11540t / h, pump operating conditions and operating conditions do not match the unit. This shows that the new pump 2117 t / h larger than the old pump, high efficiency, the motor power is low 87.7KW; new pump low speed operation of a single pump saves 443KW per hour.
In December 1998, the Ministry of Science and Technology of the former Ministry of Power Industry organized the appraisal and awarded the appraisal certificate of science and technology achievements throughout the country.
3, conclusion
Of course, the promotion of any new technology requires a cognitive process, the most important feature of energy-efficient water pump is energy saving, high efficiency. However, whether it is suitable for all regions, all 135MW units operating conditions also need more practical proof of application, but also the choice of local conditions. Promote energy-efficient circulating pump not only involves the configuration of the circulating pump in the power plant, pump standby and pump operation costs, but also relates to the interlock control of pump and turbine operation, etc., especially in the Yangtze River water pump room must be carefully selected, efficient The energy-saving circulating pump geometry than the larger capacity of the pump is much larger, for the waterfront pumping station, the equipment and equipment operating costs less than the structure and cost of water pumping station construction costs, especially the water level and the highest water level difference between the larger when.
References "water supply and drainage design manual"
"Thermal Power Plant Design Technical Regulations" - NDGJ5-88
"Thermal Power Plant Hydraulic Design Technical Regulations" - DL5000-200
"Efficient G48SH circulating pump design, installation instructions" - Shandong Electric Power Research Institute
Replacement Transfer Case,Hydraulic Motor For Danfoss,Orbital Hydraulic Motor,Small Loaders Hydraulic
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