The pollution problem of thermal power plants has been troubling people in the power industry. Today we will bring you a patent technology Air cooled Roots water ring vacuum unit – designed for power plant renovation.
Vacuum equipment in power plants of operation characteristics:
In power plant, vacuum pump has great influence on power generation coal consumption.Taking 300-330MW unit as an example, the coal consumption of power generation decreases by 2.6g/kWh for every 1kPa increase in vacuum.
Steam turbine vacuum and energy saving in power plant:
At present, the commonly used vacuum pumping equipment in power plants is ejector pump and water ring pump, the former is gradually replaced by the latter.The performance of the water ring vacuum pump is related to the state (pressure, temperature) of the suction gas and the temperature of the working liquid.At the same time, under the influence of “limit suction pressure”, local hammer phenomenon is easy to occur on the surface of the impeller, and the operation noise is very large and will cause the blade to produce a great tensile stress. Long time operation is easy to lead to the fracture of the blade, threatening the safe operation of the unit.
The temperature of the working liquid has a great influence on the performance of the water ring pump. Under the condition of high water temperature, the pumping performance of the water ring pump decreases rapidly by 80%~90%, and even the pumping volume is 0 at a certain inlet pressure.This is why some units need to operate two vacuum pumps to maintain the condenser vacuum in the summer.In addition, due to the temperature rise of the working fluid, it is extremely adverse to the long-term operation of the water ring vacuum pump, resulting in the following consequences:
1, destroy the vacuum, reduce the unit economy:
As the working fluid temperature increases, the corresponding saturated pressure rising, such as evaporation pressure of 4.241 kPa in 30 ℃, 40 ℃ evaporation pressure of 7.35 kPa, when the water ring vacuum pump suction pressure is less than or equal to the work liquid temperature corresponding to the saturation pressure, will make part of the working liquid vaporization, vacuum pump for suction itself a gas medium evaporation from vacuum pump volume caused a serious shortage of vacuum pump output, no non-condensable gas will cause the deterioration of heat transfer and accumulation in the condenser condenser vacuum, water vapor quality content by 60%, thereby reducing the unit economy.
At present, there are three main new technologies to improve the performance of vacuum pumps:
1. Add refrigeration device
Reduce the temperature of the working fluid to improve the pumping performance of the vacuum pump, that is, increase the pumping capacity and the ultimate vacuum value, so as to achieve the purpose of improving the vacuum of the condenser system.
2. Add air ejector
Air ejector is configured on the inlet piping of water ring vacuum pump of a front air jet ejector, its open end towards the atmosphere, using vacuum negative pressure and differential pressure of the atmosphere to form of the air jet, in the injector lower than the vacuum pump for suction pressure, thereby eliminating vacuum pump “extreme suction pressure” restrictions on the condenser pressure to improve.But although this technology solves the limit pressure and cavitation of the vacuum pump, it reduces the pumping volume and increases the electricity consumption. This is reflected in some power plants after the technological transformation, because the pumping volume can not be reduced by a single pump to maintain the vacuum, and is forced to start two vacuum pumps, and the energy consumption directly increases by 100%.
3. The use of high efficiency and energy-saving vacuum device
This technology is an application of a high efficiency group in the condenser vacuum pumping system of thermal power plant. The energy saving can reach 80%, and at the same time, the vacuum of the condenser can be improved under the condition of high water temperature in summer (compared with the conventional water ring pump under the same condition).