Basic knowledge of thermal power plants

1. Knowledge of thermal power generation

Using coal, oil, natural gas and other extremely rich fossil fuels to generate electricity is called thermal power generation. According to the power generation mode, it can be divided into steam turbine power generation, gas turbine power generation, internal combustion engine power generation and gas-steam combined cycle power generation, and "cogeneration (thermal power plant)" in which thermal power units provide electricity and heat at the same time.

Steam turbine power generation, also known as steam power generation, uses fuel to burn in a boiler to generate steam, which is used to drive the steam turbine, and then the steam turbine drives the generator to generate electricity. This power generation mode occupies a major position in thermal power generation, accounting for more than 95% of the total installed capacity of thermal power generation in the world.

Both internal combustion engine and gas turbine power generation are called gas power generation.

Internal combustion engine power generation mainly refers to high-power diesel engine power generation. The compression ignition engine of diesel engine system uses piston to compress the sucked air to high temperature and ignite the injected fuel to generate high temperature and high pressure, which drives the machinery to rotate and drives the generator to generate electricity. Its advantages are light weight per unit capacity, small floor space, low investment and fast construction speed, but its disadvantages are high fuel price, expensive power generation cost, small capacity, heavy maintenance workload and short operation cycle. Except for special occasions, it is mostly used as peak power supply and emergency power supply. At present, the power of the largest single diesel generator set has reached 45 thousand kilowatts, and the net power generation efficiency has reached 30%~40%.

Gas turbine is a kind of rotating machinery, which is more suitable as common power generation equipment than diesel engine. It compresses air through a compressor and sends it to a combustion chamber, where it is mixed with injected fuel to generate high-temperature and high-pressure fuel gas, which enters a turbine to expand and do work, and drives a generator to generate electricity. Its single unit capacity is much smaller than that of a steam turbine, and its maximum power is 13 ~ 2 16 kW, and its net power generation efficiency exceeds 35%, which is mainly used for peak load.

Combining gas power generation with steam power generation is gas-steam combined cycle power generation, which has high electric energy conversion efficiency.

2. Seek the basic knowledge of thermal power plants urgently, preferably with nodes and the like.

Thermal power generation generally refers to the way that water is heated by using the heat energy generated by the combustion of fuels such as oil, coal and natural gas, so that the water becomes high-temperature and high-pressure steam, and then the steam drives the generator to generate electricity.

Power plants that use coal, oil or natural gas as fuel are collectively called thermal power plants. The main equipment systems of thermal power plants include: fuel supply system, water supply system, steam system, cooling system, electrical system and other auxiliary process equipment.

The thermal power generation system is mainly composed of combustion system (boiler as the core) and steam-water system (mainly composed of various pumps, water heaters, condensers, pipes, water walls, etc.). ), electrical system (mainly turbine generator, main transformer, etc. ), control system, etc. The first two generate high-temperature and high-pressure steam; The electrical system realizes the conversion of thermal energy, mechanical energy and electrical energy; The control system ensures the safe, reasonable and economical operation of each system.

The important problem of thermal power generation is to improve thermal efficiency by improving boiler parameters (steam pressure and temperature). In the 1990s, the best thermal power plants in the world were able to convert about 40% of thermal energy into electrical energy. The thermal energy utilization rate of large heating power plants can only reach 60%~70%.

In addition, thermal power generation consumes a lot of coal and oil, causing environmental pollution, which has also become an increasingly concerned issue. Thermal power plant is a thermal power plant that uses coal as primary energy and uses belt conveyor technology to transport the treated pulverized coal to the boiler. The boiler heated by pulverized coal combustion turns the water in the boiler into steam, which enters the high pressure cylinder after once heating.

In order to improve the thermal efficiency, the steam should be heated for the second time, and the steam will enter the intermediate pressure cylinder. The steam from the intermediate pressure cylinder is used to drive the turbine generator to generate electricity.

From the medium pressure cylinder to the symmetrical low pressure cylinder. Part of the steam after doing work is extracted from the middle section and supplied to brother enterprises such as oil refining and chemical fertilizer, and the rest flows through the condenser for water cooling to become saturated water with a temperature of about 40 degrees as reuse water.

Saturated water with a temperature of about 40 degrees reaches the deaerator through a condensate pump and a low-pressure heater. At this time, the saturated water with a temperature of about 160 degrees is deoxygenated by the deaerator and sent to the high-pressure heater by the feed water pump. The high-pressure heater uses reheated steam as heating fuel, which finally flows into the boiler for reuse. The above is the production process.

The basic production process of thermal power plants The main production systems of thermal power plants include steam-water system, combustion system and electrical system, which are described as follows: (1) Steam-water system: The steam-water system of thermal power plants consists of boilers, steam turbines, condensers, high and low pressure heaters, condensate pumps and feed pumps, including steam-water circulation, chemical water treatment and cooling systems. Water is heated into steam in the boiler, and the steam is further heated into superheated steam by the superheater, and then enters the turbine through the main steam pipeline.

Due to the continuous expansion of steam, the high-speed flowing steam pushes the blades of the steam turbine to rotate, thus driving the generator. In order to further improve its thermal efficiency, some steam is usually extracted from some intermediate stages of steam turbine to heat the feed water.

This feed water regenerative cycle is used for modern large steam turbines. In addition, the ultra-high pressure unit also adopts reheat cycle, that is, the steam that has been working for a period of time is extracted from the outlet of the high pressure cylinder of the steam turbine, heated in the reheat steam sent to the boiler, and then introduced into the middle pressure cylinder of the gas turbine to continue to expand and do work, and the steam sent from the middle pressure cylinder is sent to the low pressure cylinder to continue to do work.

In the process of continuous work, the pressure and temperature of steam are continuously reduced, and finally discharged into the condenser, cooled by cooling water and condensed into water. Condensed water is concentrated in the lower part of the condenser, pumped to low pressure by the condensate pump for heating, and then degassed by deoxygenation. The feed pump sends the preheated and deoxygenated water to the high-pressure heater, the heated hot water is pumped to the boiler, and the reheater heats the water into superheated steam and sends it to the turbine to do work, and so on.

Steam and condensate in the soda system will inevitably run, run, drip and leak, because there are many pipes to be dredged and many valves and equipment to pass through, which will cause water loss to a greater or lesser extent. Therefore, we must constantly replenish chemically treated softened water to the system, generally to the deaerator. (II) Combustion system The combustion system consists of coal conveying, coal grinding, coarse and fine separation, powder discharging, powder feeding, boiler, dust removal and shunting.

It is transported from the coal yard by belt conveyor, passes through electromagnet and coal mill, then enters the coal bunker between coal bunkers, and then enters the coal mill through coal feeder for grinding. The pulverized coal is sent to the coarse separator through hot air from the air preheater, and the coarse separator sends qualified pulverized coal (unqualified pulverized coal returns to the coal mill) to the powder bin through the powder exhauster, and the pulverized coal is pumped into the burner by the powder feeder and sent to the boiler for combustion. Dust in the flue gas is removed by electrostatic dust removal, and then the flue gas is sent to a desulfurization device, and the gas sprayed with slurry is sent to a chimney through an exhaust fan and discharged into the sky.

(3) Power generation system The power generation system consists of auxiliary exciter, excitation disk, main exciter (standby exciter), generator, transformer, high-voltage circuit breaker, booster station and power distribution device. Power generation means that the secondary exciter (permanent magnet) emits high-frequency current, and the current emitted by the secondary exciter flows through the excitation consolidation and then is sent to the main exciter. After the main exciter generates electricity, it is sent to the generator rotor through the voltage regulator and demagnetization switch. When the generator rotor rotates its stator coil, it will induce current. The powerful current is divided into two paths through the generator outlet, one path is transmitted to the auxiliary transformer, the other path is transmitted to the SF6 high-voltage circuit breaker, and the latter is transmitted to the power grid.

Basic production process of thermal power plant This paper introduces the basic production process of steam turbine power generation. The fuels of thermal power plants are mainly coal and petroleum (mainly heavy oil and natural gas).

The coal-fired power plants in China are mainly coal-fired power plants, and some oil-fired power plants have been built in the past. The current policy is to reduce oil-fired power plants as much as possible, and all new power plants will burn coal. The thermal power plant consists of three main equipments-boiler, steam turbine, generator and corresponding auxiliary equipment, which are connected by pipes 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. 1. The combustion system of the combustion system is shown in figure 1-l, including the combustion part of the boiler, coal conveying, ash removal and flue gas emission.

3. What is thermal power generation?

Thermal power generation is the use of coal, oil, natural gas and other fossil fuels with extremely rich natural reserves to generate electricity.

According to its power generation mode, thermal power generation can be divided into steam turbine power generation, gas turbine power generation, internal combustion engine power generation and gas-steam combined cycle power generation, as well as thermal power plants powered and heated by thermal power units. Steam turbine power generation is also called steam power generation. It uses fuel to burn in a boiler to generate steam, which is used to drive a turbine, and then the turbine drives a generator to generate electricity.

This is one of the important ways of thermal power generation, accounting for more than 95% of the total installed capacity of thermal power generation in the world. Power generation by internal combustion engines and gas turbines is also called gas power generation.

Internal combustion engine power generation mainly refers to high-power diesel engine power generation. Diesel engine system compression ignition engine, the inhaled air is compressed to high temperature by the piston, and the injected fuel is ignited to produce high temperature and high pressure, which drives the machinery to rotate and the generator to generate electricity.

The advantages of this power generation method are light weight per unit capacity, small floor space, low investment and fast construction speed. The disadvantages are high oil consumption, high power generation cost, small capacity, large maintenance workload and short operation cycle. Except for special occasions, it is mostly used as peak power supply and emergency power supply. At present, the largest single diesel generator set has a power of 50,000 kilowatts and a net power generation efficiency of 30%? 40%。

Gas turbine is a kind of rotating machinery, which is more suitable as a common power generation device than diesel engine. It compresses air through the compressor and sends it into the combustion chamber, where it is mixed with injected fuel to generate high-temperature and high-pressure gas, which enters the turbine to expand and do work, and drives the generator to generate electricity.

The unit capacity of this gas turbine is smaller than that of steam turbine, and the maximum power is 13? 2 1。 60,000 kilowatts, the net power generation efficiency can reach 35%, mainly used for peak load.

Combining gas power generation with steam power generation is gas-steam combined cycle power generation, so don't underestimate this simple combination, which can greatly improve the efficiency of electric energy conversion.

What skills and knowledge do you need to master when working in a thermal power plant?

At present, what power plants need is basically operators. Because the main and auxiliary parts need to be separated, maintenance is the part to be separated, so there is no need to carry out maintenance.

You are majoring in electrical engineering and automation, and relay protection should be something you have studied. You can write a graduation thesis on relay protection.

If you want to run in a power plant, the future operation operators should be all-round, that is, whether it is boiler, steam turbine or electrical specialty, it is difficult to become an excellent centralized control operation operator. Then in addition to what you have learned now, you should also master the knowledge of boiler principle, steam turbine principle, generator principle, thermal automation control, pump and fan principle, production technology of thermal power plant and so on.