Working principle of thermal power plant.1 article accurate make it clear!

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Briefly introduce the working principle of thermal power plant and the basic production process of steam turbine power generation:

Working principle of thermal power plant

The fuel of thermal power plant is mainly coal and oil (mainly heavy oil and natural gas), which means the way of thermal power generation is also different. China’s thermal power plants are mainly coal-fired. In the past, a number of oil-fired power plants were built. The current policy is to reduce the number of oil-fired power plants as much as possible, and all new power plants are coal-fired.

A thermal power plant consists of three major equipments-boiler, steam turbine, generator and corresponding auxiliary equipment. They are connected by pipelines or lines to form the main production system, namely combustion system, steam-water system and electrical system. The production process is briefly described as follows.

Combustion system

Coal is conveyed by belt to the coal hopper of the boiler workshop and enters the coal mill to be ground into coal powder (coal powder furnace has coal mill). Then it is sprayed into the furnace together with the air preheated by the preheater to burn, converting the chemical energy of the coal into thermal energy. After the flue gas is ash-removed by the dust collector, it is extracted by the induced draft fan and discharged into the atmosphere through a tall chimney. The slag and fine ash at the bottom of the dust collector are discharged to the ash field by the ash pump.

Steam-water system

After being heated in the boiler, the water evaporates into steam, and is further heated by the superheater to become superheated steam with a specified pressure and temperature, and then sent to the steam turbine through the pipeline.

In the steam turbine, the steam continues to expand and flow at high speed, impacting the rotor of the steam turbine, rotating at the rated speed (3000r/min), converting thermal energy into mechanical energy, and driving the generator coaxial with the steam turbine to generate electricity.

During the expansion process, the pressure and temperature of the steam continue to decrease. After the steam does work, it is discharged from the bottom of the steam turbine. The discharged steam is called exhaust steam, which is discharged into the condenser. In the condenser, the exhaust steam of the steam turbine is cooled by cooling water and condensed into water.

The thermal power plant generates electricity by converting heat energy into mechanical energy
The thermal power plant generates electricity by converting heat energy into mechanical energy

The condensed water in the lower part of the condenser is pressurized by the condensate pump and then enters the low-pressure heater and deaerator. The water temperature is increased and the oxygen in the water is removed to prevent corrosion of thermal power equipment. The water is further pressurized by the feed water pump, and then enters the high-pressure heater and returns to the boiler to complete the water-steam-water cycle. The condensed water after the feed water pump is called feed water.

The steam and condensed water in the steam-water system always have some losses during the circulation process. Therefore, chemically treated water must be continuously added to the feed water system. The feed water enters the deaerator and is pumped into the boiler together with the condensed water by the feed water pump.

Electrical system

The electrical system includes generators, excitation systems, plant power systems, and step-up substations.

Summary

A thermal power plant is a plant that uses coal, oil, and natural gas as fuel to produce electricity. Its basic production process is: the fuel burns in the boiler to heat the water to make steam, and the chemical energy of the fuel is converted into thermal energy. Steam pressure drives the turbine to rotate, converting heat energy into mechanical energy, and then the turbine drives the generator to rotate, converting mechanical energy into electrical energy.

It is classified into: by fuel, coal-fired power plants, oil-fired power plants, gas-fired power plants, waste heat power plants, and power plants fueled by garbage and industrial waste. By steam pressure and temperature, medium and low pressure power plants (3.92MPa, 450 degrees). High pressure power plants (9.9MPa, 540 degrees), ultra-high pressure power plants (13.83MPa, 540 degrees). Subcritical pressure power plants (16.77MPa, 540 degrees), supercritical pressure power plants (22.11MPa, 550 degrees).

According to the prime mover, there are condensing steam turbine power plants, gas turbine power plants, internal combustion engine power plants, steam-gas turbine power plants, etc. According to output energy, there are condensing power plants (only electricity generation), thermal power plants (thermal power generation and heating). According to installed capacity of power plants, there are small-capacity power plants (below 100MW), medium-capacity power plants (100-250MW), large- and medium-capacity power plants (250-1000MW), and large-capacity power plants (above 1000MW).

The largest thermal power plant in China: Beilun Port Power Plant in Zhejiang, with an installed capacity of 3 million KW (3000MW) and 5 600,000 KW (600MW) units.

The thermal power plant utilizes coal, natural gas, or nuclear fuel as its primary energy source
The thermal power plant utilizes coal, natural gas, or nuclear fuel as its primary energy source