A thermal power plant is a factory that uses coal, oil, and natural gas as fuel to produce electricity and heat. Its basic production process is: the fuel is burned in a boiler to heat water to make steam, and the chemical energy of the fuel is converted into heat energy. The steam pressure drives the steam turbine to rotate. , thermal energy is converted into mechanical energy, and then the steam turbine drives the generator to rotate, converting the mechanical energy into electrical energy, and a part of the thermal energy or waste heat is output in the form of steam through the pipeline for industrial production or converted into hot water for civil heating.
In the thermal system of a power plant, the pumps used in the power plant are divided into two systems according to their functions: steam turbine unit auxiliary pump (boiler feed water pump, front pump, condensate pump) desulfurization circulation pump (main circulation desulfurization pump, FGD peripheral pump, absorption tower system), there are boiler feed water pumps, condensate pumps and cooling water circulation pumps required for water and steam circulation, as well as pre-booster pumps, low-pressure heater drain pumps, high-pressure heater drain pumps, and ash pumps for removing boiler coal ash. When the power plant uses an auxiliary circulation drum boiler or a combined circulation boiler, a boiler circulation pump is also required. In the wet flue gas desulfurization system of thermal power stations, desulfurization pumps such as limestone slurry pumps, slurry circulation pumps and gypsum slurry pumps are also installed. Power plant pumps are used in a wide range of applications.
1. Boiler feed water pump
With the improvement of the technical level of the power station, the boiler feed water pump is developing in the direction of large capacity and high lift, and its operation is required to be safe and reliable, and it is even required that the pump can continue to reliably “dry run” and Easy maintenance to reduce the economic loss caused by unit shutdown.
2. Condensate pump
The condensate pump absorbs water from the hot well of the condenser, because the pressure in the condenser is very low, in order to avoid cavitation of the condensate pump, in addition to making it work in the reverse flow state, it is also required to have a high anti-cavitation performance, according to the requirements The head is different, the condensate pump can be a single-stage pump or a multi-stage pump, it can be a vertical shaft pump or a horizontal shaft pump.
3. Heater drain pump
It is also used to transport condensate. The low-pressure heater drain pump draws condensed water from the low-pressure heater and delivers it to the feed water circulation pipeline. The high-pressure heater drain pump is used to ensure that the condensed water in the high-pressure heater can be transported to the degasser when the main steam turbine is at partial load. Therefore, the power plant drain pump, especially the low-pressure heater drain pump, has similar working conditions to the condensate pump, and its structure should also have the same above-mentioned characteristics as the condensate pump.
4. Ash pump
Ash and slag pumps are used to transport boiler coal ash and slag to suitable places outside the plant or to dams.
5. Boiler circulation pump
The boiler circulation pump installed in the steam drum boiler or compound circulation boiler used in large-capacity power stations is used to make the boiler water do forced circulation. The head of the pump is not high, generally 30-60m, but the working conditions are harsh. The inlet pressure and temperature of the pump are very high, so it must have good sealing performance, and canned pumps or wet stator sealless pumps are mostly used.
6. Desulfurization pump
In the wet flue gas desulfurization system of coal-fired power plants, desulfurization pumps such as limestone swirl pumps, limestone slurry pumps, circulating slurry pumps, gypsum discharge pumps, filter pumps, waste water swirl pumps, and flue gas cooling water pumps are also installed.
7. Circulating pumps for power plants
It is used to supply condensed water to the condenser. This kind of pump has a large flow rate, which can be 50 times that of the boiler feed water pump, and its geometric size is also large. It is the largest equipment in the auxiliary equipment for power generation. Since the amount of cooling water depending on the capacity of the condenser varies with the seasons, the flow rate of the circulation pump also varies with the seasons. This type of pump often operates in a reverse flow state, and also often adopts a vertical shaft structure in which the impeller is submerged in water. Vertical shaft axial flow pumps or centrifugal pumps can be used as circulating pumps.
In addition to the above-mentioned various pumps, auxiliary mechanical equipment must be equipped for the normal operation of the main equipment of the power station. There are also various types of pump applications within this auxiliary equipment, including:
●Vacuum pumps and jet pumps in vacuum systems of power stations
●Production and domestic water supply pumps in technical water supply systems
●Various oil pumps in the oil supply system
●Sewage pumps, submersible sewage pumps, and sewage pumps in the sewage system
●Fire pumps in fire protection systems
●Sewage pumps and submersible sewage pumps for water seepage and accumulated water in the factory area