[Boutique] Thermal Power Plant Internship Report

Part 1: Thermal Power Plant Internship Report

I. The purpose and significance of the internship

The task of this internship is to familiarize yourself with the thermal energy and power engineering related companies, mainly the main thermal systems of thermal power plants and their layout. The location of the visit was the power plant model room, Nanjing Xiexin Sludge Power Plant and Nanjing Steam Turbine Manufacturing Plant. The purpose is to enable students to have a systematic and comprehensive understanding of the basic structure, working principle and performance of the main production equipment of the thermal power plant during the short-term understanding of the internship, and to provide the necessary perceptual knowledge and understanding of the follow-up professional courses. Basic knowledge.

A thermal power plant is a plant that uses the chemical energy of coal, oil, natural gas and other fuels to produce electricity, that is, the chemical energy of the fuel → the thermal potential of steam → mechanical energy → electrical energy. In a boiler, the chemical energy of the fuel is converted into the thermal energy of the steam. In the steam turbine, the thermal energy of the steam is converted into the mechanical energy of the rotation of the wheel, and the mechanical energy is converted into electrical energy in the generator. Furnace, machine and electricity are the main equipments in thermal power plants, also known as the three mainframes. The equipment that assists the three main hosts is called the auxiliary equipment. The host and auxiliary machines and their connected pipes and lines are called systems. The raw material of Xutang Thermal Power Plant is raw coal. The raw coal is transported to the coal storage yard of the power plant by car or ship, and then transported to the coal hopper by the coal conveyor belt. Then, it is dropped from the coal hopper and sent to the coal mill to be pulverized into coal powder, and at the same time, hot air is sent to dry and transport the coal powder. Finally, it is sent to the furnace of the boiler for combustion. The hot air required for fuel combustion is heated by the air blower into the air preheater of the boiler. The preheated hot air is sent to the coal mill for drying and pulverized coal through a part of the air duct, and the other part is directly led to the burner. Enter the furnace. The high-temperature flue gas generated by the combustion, under the action of the induced draft fan, first flows through the inverted U-shaped flue of the boiler through the furnace, the water wall tube, the superheater, the economizer, the air preheater, and gradually smokes The heat of the gas is transferred to the working medium and the air, and it becomes a low-temperature flue gas, which is discharged into the atmosphere after being purified by the precipitator and the desulfurization device. The ash generated after the combustion of coal, in which large ash will be separated from the gas stream by its own weight, settled into the cold ash hopper at the bottom of the furnace to form solid slag, and finally discharged into the ash slag by the slag discharging device, and then the ash residue Pumped to the ash yard. A large amount of fine ash particles are taken away with the flue gas and sent to the ash ditch after separation by the dust collector. The furnace feed water first enters the economizer to be preheated to near saturation temperature, and then heated to a saturated steam by the heated surface of the evaporator, and then heated to superheated steam through a heat exchanger, which is also called main steam. Through the above process, the transportation and combustion of the fuel, the treatment of the generated fuel and the discharge of the fuel are completed. The main steam from the boiler superheated gas enters the steam turbine to expand work through the main steam pipe, and the steam turbine is driven to drive the generator to generate electricity. The spent steam discharged from the turbine is discharged into a condenser where it is condensed and cooled into water, which is called main condensate. The main condensate is sent to the low-pressure heater through the condensate pump, and the steam turbine extracts part of the steam and then enters the deaerator, in which various gases dissolved in the water are removed by further heating. The feed water and main condensate treated by the chemical workshop sink into the water tank of the deaerator to become the feed water of the boiler, and then pumped to the high-pressure heater after being boosted by the feed water pump. The high-pressure part of the steam turbine extracts a certain steam and then feeds it. The boiler, so that the working fluid completes a thermal cycle. The circulating water pump sends cooling water to the condenser, which forms a circulating cooling water system. Through the above process, the process of converting the thermal energy of steam into mechanical energy, electric energy, and boiler feed water supply is completed. Therefore, a thermal power plant is a complex energy conversion power plant consisting of three major parts of furnace, machine and electricity and their respective auxiliary equipment and systems.

2. Boiler part

1. Overall overview

The boiler is one of the three main equipments of a thermal power plant. Its role is to turn water into high temperature and high pressure steam. A boiler is a summing device for three processes of fuel combustion, heat transfer, and vaporization of water.

Schematic diagram of boiler operation of Nanjing GCL sludge power plant

Boiler technical parameters

Name unit boiler maximum continuous output boiler rated output

Superheated steam flow T/h

Export steam pressure MPa

Export steam temperature

At hot steam flow T/h

Steam pressure, outlet / import MPa

Steam temperature, export/import

Feed water temperature

2. Boiler system

Soda system: equipment that heats, evaporates, and overheats the entire process. It consists of economizer, steam drum, down pipe, water wall, superheater, reheater and other equipment.

Wind smoke system: The equipment through which the wind passes through heating, and the fuel burns to generate flue gas, the flue gas radiates heat, and is discharged into the atmosphere.

Pulverizing system: The raw coal is made into pulverized coal, and then sent to the powder silo, and the equipment passes through the whole process of the furnace. The main components are coal mill, coal feeder, coal powder separator and so on.

3. Boiler body equipment structure

The structure and arrangement of the drum

The steam drum is the ultimate pressure component of the natural circulation and forced circulation boiler. There is no circulation loop without the steam drum. The main functions of the steam drum are: the connection hub of the three processes of heating, evaporation and overheating of the working fluid, which is used to ensure the normal water circulation of the crossing. The steam drum is equipped with a steam separator and a continuous sewage device to ensure the normal water circulation of the boiler. There is a certain amount of water, so it has a heat storage capacity, which can alleviate the change speed of the air pressure, which is beneficial to the boiler operation adjustment.

Down pipe, furnace water pump, regular sewage

There are 5 downcomer pipe joints welded on the bottom of the steam drum. The down pipe is installed at the bottom of the steam drum. The purpose is to make the upper part of the lower pipe inlet have the largest water layer height, which is beneficial to the vaporization of the working fluid at the lower pipe inlet and the lowering pipe. With steam.

Water wall structure, pipe diameter, layout

The heated surface laid on the furnace wall around the furnace is often referred to as a water wall. The water wall of the medium pressure natural circulation boiler is all the evaporation heating surface. The water wall of high pressure, ultra high pressure and subcritical pressure boilers is mainly the evaporation heating surface, and a radiant superheater or a radiant reheater is often arranged in the upper part of the furnace. In a once-through boiler, the water wall is both the heating surface for water heating and evaporation, and the heating surface for the superheater, but the water wall is still mainly the evaporation heating surface.

Structure and arrangement of economizer and air preheater

Economizers and air preheaters are typically placed below the last or convective flue of the boiler convection flue. The temperature of the flue gas entering these heated surfaces is low, so the two heated surfaces are usually referred to as the tail heating surface or the low temperature heating surface.

The economizer uses a heat exchange device that uses the heat of the flue gas of the boiler tail to heat the feed water. He can reduce the exhaust gas temperature, improve boiler efficiency and save fuel. Since the feed water enters the boiler to evaporate the heating surface, it is first heated in the economizer, which can reduce the heat absorption of the water in the evaporation heating surface, and the economizer can replace the partial evaporation heating surface. Moreover, the working fluid in the economizer is water, and its temperature is much lower than the saturation temperature under the water supply pressure. In addition, the working fluid in the economizer is forced flow, countercurrent heat transfer, and the heat transfer coefficient is high. In addition, after the feed water passes through the economizer, the temperature of the feed water entering the steam drum can be increased, and the temperature difference between the feed water and the steam drum wall is reduced, thereby reducing the thermal stress of the steam drum. Therefore, the role of the economizer is not only to save coal, but has become an indispensable component in modern boilers.

The air preheater can not only absorb the heat in the exhaust gas, but also reduce the exhaust gas temperature, thereby improving the efficiency of the boiler; and because of the residual heat of the air, the ignition condition of the fuel is improved, the combustion process is strengthened, and the incomplete combustion heat loss is reduced. It is especially important for burning anthracite that is difficult to catch fire. The use of preheated air can increase the temperature of the furnace and strengthen the heat exchange of the furnace radiant, so that the water surface of the water wall that absorbs the same radiant heat can be reduced. The higher temperature preheated air is sent to the coal powder system as a desiccant. Therefore, the air preheater has become an indispensable component in modern large-scale boiler units.

Three. Turbine

1. Overview of the whole machine

The steam turbine is a rotary thermal power machine with steam as the working medium. Compared with other prime movers, it has the advantages of large single machine power, high efficiency, stable operation and long service life.

The main purpose of a steam turbine is as a prime mover for power generation. The steam turbine must be combined with boilers, generators, and mechanical equipment such as condensers, heaters, pumps, etc. to work together. The steam with a certain pressure and temperature comes from the boiler, enters the steam turbine through the main gas valve and the regulating gas valve, and flows through a series of annularly mounted nozzle grids and moving blade cascades to expand work, transforming its thermal energy into pushing the turbine rotor to rotate. The mechanical work, through the coupling to drive other machinery, here refers to the work of the generator. In a thermal power plant, the steam after the expansion work is introduced into the condenser by the exhaust portion of the turbine, and the cooling water is allowed to condense. The condensed water is then pumped to the heater for heating and then used as boiler feed water to circulate.

Turbines are divided into two categories according to their working principles: impulsive steam turbines and reaction steam turbines.

The nozzle grid and its matched moving blade cascade form the most basic working unit "stage" in the steam turbine, and the different stages are sequentially connected in series to form a multi-stage steam turbine. The steam is converted in different ways in the stage to form steam turbines of different working principles, namely impulsive steam turbines and reaction steam turbines.

Impulse turbine. There is mainly an impulsive stage composition in which the steam is substantially expanded in the nozzle grid, and only a small amount of expansion is in the moving cascade.

Reaction turbine. There are mainly reaction stages, and steam has a moderate expansion in the turbine's stationary blade cascade and moving blade cascade.

2. Rotor stator and other components and functions

The rotating part of the steam turbine is called the rotor. It is one of the most important components of the steam turbine, and it is responsible for the energy conversion and torque transmission of the working fluid. The working condition of the rotor is quite complicated. He is in high-temperature working medium and rotates at high speed. Therefore, he suffers from the huge profit caused by the centrifugal force of the blade, the impeller and the spindle itself, and the thermal stress caused by the uneven temperature distribution. On the other hand, the torque exerted by the steam on the bucket cascade is transmitted to the motor through the impeller, the main shaft and the coupling of the rotor.

The cylinder is the outer casing of the turbine. Its function is to separate the flow passage of the turbine from the atmosphere. The gas chamber is closed by the conversion of steam heat energy into mechanical energy. The cylinder is equipped with nozzles, partitions, partition sleeves, gas seals and other components. They are collectively referred to as the static.

When the steam turbine is running, the turbine rotates at a high speed, and the static bodies such as the cylinders and the partitions are fixed, so that it is necessary to leave appropriate gaps between the rotor and the stator so as not to collide with each other. However, the presence of the gap will result in dew, which will not only reduce the efficiency of the unit, but also affect the safe operation of the unit. In order to reduce steam leakage and prevent air leakage, a sealing device is required, commonly referred to as a gas seal. According to the different installation positions, the gas seal can be divided into a partial gas seal, a diaphragm seal, and a shaft end seal. The reaction turbine is also equipped with a high-medium-balanced piston gas seal and a low-pressure balanced piston gas seal.

3. Condenser and heater

The condenser uses circulating cooling water to condense the steam discharged from the turbine, establishes and maintains the required vacuum in the steam exhaust space of the turbine, and recovers the pure condensate to supply the boiler feed water, thereby improving the thermal efficiency of the unit.

The high-pressure heater uses steam turbine steam to heat the boiler feed water to increase the feed water temperature to improve the thermal economy of the unit. The high-pressure heater is composed of a casing, a tube sheet, a tube bundle, a partition, and the like. The high-pressure feed water heater is a single-row horizontal surface condensation type heat exchanger, and the water chamber adopts a self-sealing structure.

The high-addition housing is an all-welded structure composed of steel plates welded. In order to facilitate the removal of the housing, the lifting lugs and the housing rollers are mounted and allowed to expand freely during operation. To prevent deformation of the housing, each of the heaters with superheated steam cooling section is provided with a shield and a baffle. Stainless steel anti-shock plates are installed at the steam inlet and the hydrophobic inlet of all heaters to prevent the pipes from being directly impacted by steam and causing vibration and corrosion.

The high pressure heater consists of a superheated steam cooling section, a condensation section and a hydrophobic cooling section. The superheated steam cooling section uses a part of the superheated steam extracted from the steam turbine to increase the feed water temperature, and is located on the feed water outlet flow side, and has a cladding plate sealed. Superheated steam flows uniformly through the tube at a suitable line speed and mass velocity under the direction of a set of baffles, leaving the steam with sufficient superheat to ensure that the steam leaves the section as dry, so that when the steam leaves the When the section enters the condensation section, it can prevent the damage of wet steam erosion and water erosion. The condensation section heats the feed water by the latent heat when the steam is condensed, and a set of partitions distributes the steam evenly along the length of the heater to support the heat transfer tube. The steam entering this section is automatically balanced according to the gas cooling principle until it is condensed by saturated steam into saturated condensate and collected at the tail or bottom of the heater. The exhaust pipe that collects the non-condensed gas must be placed at the lowest pressure of the bundle. It is easy to gather non-condensing gas at the place and in the casing. The accumulation of non-condensing gases affects effective heat transfer, thereby reducing efficiency and causing corrosion. The hydrophobic cooling section transfers the hydrophobic heat leaving the condensation section to the feed water entering the heater, and the hydrophobic temperature is below the saturation temperature. The hydrophobic cooling section is located on the feed water inlet process side and has a cladding plate sealed. When the hydrophobic temperature is lowered, the tendency to vaporize within the pipe is diminished when flowing to the next lower pressure heater. The cladding panel is internally spaced from the overall portion of the heater casing side, and a certain hydrophobic water level is maintained from the end plate and the suction or inlet end to seal the section. Hydrophobic enters the section and is directed by a set of baffles to flow from the hydrophobic outlet tube.

System and auxiliary machines

Pump

The pump is a kind of power equipment that converts mechanical energy into liquid pressure potential energy and kinetic energy. It is an indispensable equipment for maintaining the steam power cycle of thermal power plants and one of the main auxiliary equipment of thermal power plants. There are many places where the pump is applied in a thermal power plant. For example, a feed water pump is used to supply water to the boiler, a condensate pump is used to pump condensate from the condenser hot well, and a circulating water pump is used to supply cooling water to the condenser. The pumps in thermal power plants are directly or indirectly involved in the production process, and their safety directly affects the production safety of thermal power plants.

2. Fan

A wind turbine is a kind of power equipment that converts mechanical energy into gas pressure potential energy and kinetic energy. It is one of the main auxiliary equipment of thermal power plants. The fan in the fire electric field is mainly used in the flue gas system and the pulverizing system of the boiler, and is used for conveying air, flue gas and air pulverized coal mixture, etc., mainly including a blower, an induced draft fan, a primary fan and a powder exhaust fan.

These wind turbines in thermal power plants are directly involved in the production process, and their safety and reliability directly affect the safe production of the thermal power plant. These fans consume a lot of power, and their shaft power is hundreds of kilowatts, and thousands of kilowatts. The power consumption is roughly the same as that of a thermal power plant. Therefore, the safety and economic operation of the fan must be sufficiently recognized, and the maintenance of the fan should also be given high priority to ensure the overall safety and economy of the power plant.

V. Experience

Short-term understanding of internships, school departments give us a theoretical knowledge. After the teacher explained and watched the related video pictures, we have a more comprehensive understanding of the production process of boilers, steam turbines, auxiliary machines, etc. of thermal power plants and power plants. On the morning of September 6, we first visited the power plant model and various equipment models in the school laboratory. Then, the group arrived at the Nanjing GCL sludge power plant with a small installed capacity. After the safety education, it was divided into groups. Finally, the instructor took the internship seriously. Everyone abides by the various rules and regulations of the power plant and the various requirements put forward by the teachers. If you don't understand the place, you will be open to the teachers who bring us. The masters are also very enthusiastic to answer for us. Through this internship, we not only combine the theoretical knowledge of the school with the specific production practice, but also through the explanations of the masters, the process of power plant production, water, coal, desulfurization and dust removal has become more profound. Understanding. Through the visit to the Nanjing GCL sludge power plant and the detailed explanation of the teachers, we have further understanding of the power generation process of the thermal power plant.

In this internship, I learned a lot of knowledge that can only be obtained in practice, and I understand the general situation of the thermal power plant and its operation process. In today's rapidly developing economy, power has an unshakable position. Production internship is an important practice part of the university stage, and every college student should participate. This internship lays the foundation for better theoretical study in the future, further recognizing the importance of electric power production and fully embodying the characteristics of our thermal energy professional practice.

Article 2: Thermal Power Plant Internship Report

Through a year of study of the power plant expertise, we have a preliminary theoretical understanding of the power plant. In order to better understand and understand professional knowledge, and expand the actual knowledge, we have conducted internships in Tongdian Datang Thermal Power Plant and Datong No. 2 Power Plant, and conducted a centralized control simulation of Wulashan Power Plant in Beiyue Vocational and Technical College. Through the internship, I have deepened my understanding of the power plant and related industries, and I have a certain understanding of the equipment in the factory.

First, the power plant introduction

Under the careful arrangement of the school teachers, we have successively arrived at the Datang Power Plant and the Second Power Plant, and the Beiyue Vocational and Technical College. In fact, as the masters of the power plant said, this short visit is just a visit. It is not an internship, but it is not necessarily a visit, and it will be of great help to us. From small to large, I have been dealing with textbooks. This time I can directly learn the knowledge other than textbooks. Of course, I can't miss it, and I have to grasp it well.

The first time came to Datang Thermal Power Plant. Before coming to the power plant, the factory master briefed us on the basic history of the power plant and the safety education of the plant. Unfortunately, our group was assigned to the night shift. In the early morning, we visited the various parts of the power plant under the leadership of their respective masters. I and two other students were internships in the coal handling system. The first feeling in the factory is noisy, and then tall buildings, the masters emphasize the most safety. For the introduction of the master, I can hardly hear anything about one meter. Unfortunately, in the factory, I didn’t get close, of course I didn’t know what to say, but fortunately, after the noisy factory, we came. The coal-conveying control room can be said to be the best working place in the power plant environment. There is no gray smoke outside the house, no machine rumbling, and there is no outside heat. In the centralized control room, the most noticeable is a row of three machines across the main entrance, which are covered with red lines, red dots, and some green ones. According to the introduction, it is a flow chart for controlling the equipment and equipment of the coal handling system of the power plant. . Nowadays, it is basically automated. Several computers in the center of the room control him. The number of staff is only a few. As long as the computer is controlled, the normal and safe operation of the machine can be ensured. Compared with the old power plant. Nowadays, the degree of automation is greatly improved, so the number of technicians in the power plant is getting less and less. Of course, the requirements for them are getting higher and higher, and the direct result is that the benefits are getting better and better.

This can also be clearly seen in the Datong No. 2 Power Plant. Under the guidance of the workers' masters, we passed through the power plant's factory building. There is nothing other than just seeing the machinery and equipment. It is difficult to see one. Workers, occasionally seeing a few controllable machines, according to the workers' masters, only the workers need to set up the program on it, the machine control can be observed in the centralized control room, so as long as the power plant runs out of problems, It is immediately known that once a call is made, the repair will be passed immediately, so that it can be resolved as soon as possible.

When it comes to automation, we can also feel deeply in the second power plant. In the steam drum manufacturing branch, some auxiliary manufacturing of steam drums, such as drilling and welding on the steam drum, are all carried out automatically, as long as the skilled workers design the program according to the manufacturing requirements and then start the machine; The production of countless pipes, if it is only artificially polished, it is impossible to do exactly the same, so of course, the automatic operation of the machine is also used, and the workers only need to pay attention to the machine. For the boiler, he has an important part of the water wall. The water wall is composed of a large number of tubes side by side. The tubes are welded together. These weldings are also automatically completed by the machine. Each time several tubes are arranged side by side, the position between them is adjusted, and then the work is automatically performed.

At present, the degree of automation of thermal power plants is very high, and the number of personnel will inevitably decrease, so that the quality of work will increase. It is understood that the employees of a thermal power plant are generally five shifts or three shifts or four shifts or others. Anyway, the rotation system is adopted. Every time it is working, it is 8 hours in a row, and it works in the centralized control room. The computer must be closely watched to ensure that the occurrence of abnormal conditions can be immediately detected; for maintenance, the working hours are somewhat different, there is a joke, saying that the maintenance workers all have "phone phobia", as long as the phone rings Most of them think that they have to work. Some equipment in the power plant needs to be repaired. Whether it is winter or hot summer, whether it is day or night, it will rush to the scene. At the time, we all sounded very surprised. I naturally thought that I would not engage in such work in the future. However, there is a saying in China - "I don't go to hell, who goes to hell?" Work, of course, will not complain, but will not push it. But then again, the technology is so developed, and the machines and equipment are so easy to break, so the situation of maintenance workers is not as difficult as imagined. In short, the concept of working in a power plant is somewhat different from the general one. The typical one is that it will not be calculated according to the normal week, nor will there be a normal “Golden Week”. The most leisure time is when the power plant is the busiest. But I don't think it's okay, it's not all working on earth.

This internship involves all aspects of the power plant, and of course it will not miss the issue of employee salaries. As far as salary is concerned, I have not looked at my face and asked some, but some of them did not have a positive answer, but from their expressions, it should be pretty good. This is also true. Contemporary China is rising and the economy is exploding. In terms of growth, electricity is one of the most fundamental guarantees. As a source of electricity, power plants must play a big role. In short, the overall impression of the thermal power plant is that the working environment is not good, the working hours are not big, the working place is not close to the city, the work is not bad, the contribution to the country is unparalleled, and there is still tremendous development!

Second, the power generation process of thermal power plants

Throughout the internship period, I feel that the harvest at Beiyue Institute of Technology is the biggest and most practical. The teachers from the second power plant are very strong, witty and humorous. Oh, off topic. Unfortunately, there is only one week. Although some things are still a little bit unclear, the production process of thermal power plants has been basically understood.

In fact, the production process of a thermal power plant is a process of conversion of four energy forms. First, the chemical energy of fossil fuels is converted into heat by combustion. This process is completed in the combustion chamber of a steam boiler or a gas turbine; then thermal energy is converted into mechanical energy. This process is done in a steam engine or a gas turbine; finally, the mechanical energy is converted into electrical energy by a generator.

The raw material of a thermal power plant is raw coal. The raw coal is generally transported by train to the coal storage yard of the power plant, and then transported to the coal hopper or silo by the coal conveyor belt. The raw coal is dropped from the coal hopper and sent to the coal mill by the coal feeder to be pulverized into coal powder, and at the same time, hot air is sent to dry and transport the coal powder. After the formed pulverized coal air mixture is separated by the separator, the qualified pulverized coal is sent to the powder conveying pipe through the powder discharging machine, and is injected into the furnace of the boiler through the burner to be burned. The hot air required for fuel combustion is heated by the blower into the air preheater of the boiler. The preheated hot air is sent to the coal mill for drying and powder feeding through a part of the air duct, and the other part is directly led to the combustion. The device enters the furnace. The high-temperature flue gas generated by the combustion, under the action of the induced draft fan, first flows through the inverted U-shaped flue of the boiler through the furnace, the water wall tube, the superheater, the economizer, the air preheater, and gradually smokes The heat energy of the gas is transmitted to the working medium and the air, and it becomes a low-temperature flue gas. The flue gas purified by the dust remover is extracted by the induced draft fan and discharged into the atmosphere through the chimney. If the power plant burns high-sulfur coal, the flue gas is discharged into the atmosphere after being purified by the desulfurization device. The ash generated after the combustion of coal, in which large ash will be separated from the gas stream by its own weight, settled into the cold ash hopper at the bottom of the furnace to form solid slag, and finally discharged into the ash slag by the slag discharging device, and then the ash residue Pumped to the ash yard. A large amount of fine ash particles are taken away with the flue gas and sent to the ash ditch after separation by the dust collector.

The boiler feed water first enters the economizer to be preheated to near saturation temperature, and then heated to a saturated steam by the heated surface of the evaporator, and then heated to superheated steam through a heat exchanger, which is also called main steam. Through the above process, the transportation and combustion of the fuel, the treatment of the generated fuel and the discharge of the fuel are completed. The main steam from the boiler superheated gas enters the steam turbine expansion work through the main steam pipe, and rushes the steam turbine to drive the generator to generate electricity. The spent steam discharged from the turbine is discharged into a condenser where it is condensed and cooled into water, which is called main condensate. The main condensate is sent to the low-pressure heater through the condensate pump, and the steam turbine extracts part of the steam and then enters the deaerator, in which various gases dissolved in the water are removed by further heating. The feed water and the main condensate treated by the chemical workshop sink into the water tank of the deaerator to become the feed water of the boiler, and then sent to the high-pressure heater after being boosted by the feed water pump, and the high-pressure part of the even steam turbine is extracted by a certain steam, and then sent. Into the boiler, so that the working fluid completes a thermal cycle.

The circulating water pump sends the cooling water to the condenser, absorbs the heat of the exhausted air and returns to the river, which forms an open circulating cooling water system. In a water-deficient area or a power plant far from the river. A circulating water cooling system such as a high-performance cooling tower or a fountain is required to realize a closed circulation cooling water system. Through the above process, the process of converting the thermal energy of steam into mechanical energy, electric energy, and boiler feed water supply is completed. Therefore, a thermal power plant is a complex energy conversion power plant consisting of three major parts of furnace, machine and electricity and their respective auxiliary equipment and systems.

Third, the main equipment of thermal power plants

The thermal power plant is mainly composed of three major equipment: boiler, steam turbine and motor. The main understanding of this internship is the boiler and steam turbine.

boiler

In the internship of Datang Power Plant, we have known and initially understood the fluidized bed boiler. The completion of the boiler in the thermal power plant is the energy conversion process of converting the chemical energy of the fuel into heat energy through combustion. The products of the boiler unit are high temperature and high pressure steam. The energy conversion in a boiler unit involves three processes: the combustion process of the fuel, the heat transfer process, and the vaporization process of the water. The fuel and the oxygen in the air are mixed in the boiler combustion chamber, oxidized and burned to generate high-temperature flue gas, and the process is a combustion process. The high-temperature flue gas transfers heat through the various heating surfaces of the boiler, and transfers the heat energy to the working fluid of the boiler, water. After the water absorbs heat, it vaporizes into saturated steam, and the saturated steam further absorbs heat to become high-temperature superheated steam, which is the heat transfer and water vaporization process.

Regarding the water used in the boiler, according to the teacher, the water used in the power plant is generally demineralized. In the internship, it is recognized that the feed water of the boiler first flows from bottom to top, and after heating, it enters the steam drum and then falls to the water wall. The lower header is in the water wall. Part of the water in the water wall becomes steam to form a soda mixture. The soda mixture is separated in a drum where the water continues to remain in the drum for the next cycle.

The boilers use coal. It is the raw material of thermal power plants. In Datang Power Plant, the worker master took us to visit the coal trench. I can't describe it. From a distance, I can't guess that it is coal, because it looks like an ink mountain. Power plants also have high requirements for coal. At present, the power plant generally uses a pulverized coal furnace. The reason is that the pulverized coal has good fluidity and can be fully burned. Before use, hot air is sprayed into the furnace and mixed with air to be suspended and burned in the furnace. The senior brother of Gaoxin Power Plant said that the fineness of pulverized coal is less than that of hair, mainly to improve combustion efficiency. Today's environmental problems are prominent, which seriously hinders the development of human beings. Therefore, in thermal power plants, the exhaust gas must undergo strict desulfurization before it can be discharged.

During the internship, the most relevant boilers in the power plant were the steam drums. After consulting and reading textbooks, I understand the general situation of the steam drum. Its main function is to separate the steam-water mixture, steam is taken from the top of the steam drum, heated to the rated temperature and sent to the steam turbine for work, while the water continues to remain inside for the next cycle. This is the natural circulation boiler.

When I visited the power plant, to be honest, I didn’t realize what the boiler was. In Datang Power Plant, I only saw the water wall of the No. 5 boiler to be installed. In short, it was a hollow tube with no roots. So still did not figure out, until in the simulation laboratory of the University of Technology, in the explanation of the teacher of the Second Power Plant, I realized that the square is that it is said to be more than 60 meters high, surrounded by many water pipes, that is, water wall. The boiler is generally hung. Many people don't understand why such a huge thing is hanging. The reason is very simple, in order to cope with the thermal expansion and contraction of the boiler.

Steam turbine

In the internship, I saw the steam turbine in the power plant. It was a huge thing, lying there, and I didn’t see it inside. It was only the teacher who said it during class. First of all, the teacher said that the blade is only about 30 centimeters long and the width is only ten centimeters. At that time, it felt very small and incredible. How can such a large power plant be such a small blade that it is smaller than I imagined? Much, the middle of the steel, the middle of the steel has six symmetrical grooves, it is natural, this is the rotor, listen to another explanation, six slots are used for winding, a total of three groups, in the stator The middle of the rapid rotation, as the wire cuts the magnetic line to generate electricity, the principle is very simple, from the high school to the high school and then learned the university, and now finally learned the reality. The next one is the stator. The stator is very large. The diameter is almost three meters. The outside is very smooth. There are small pieces in the inside. I heard that it is a magnet. There are some glass windows outside, which are for observation or maintenance.

Internship summary

This internship recognized a lot of practical knowledge. For the first time, I directly faced the manufacturing plants of the relevant industries in the power plant and learned about the general situation of the thermal power plants. In today's rapidly developing economy, power has an unshakable position. With the advent of the knowledge economy, science and technology are changing with each passing day, bringing great changes and developments to all aspects, including of course thermal power plants. Compared with the installed capacity of Tongtai Datang Power Plant and Datong No. 2 Power Plant and the same coal Tashan Power Plant under construction, the difference is huge, and the development of large-capacity units is becoming a trend, so that resources can be better utilized and satisfied. People are increasingly using electricity.

Part 3: Thermal Power Plant Internship Report

Time flies, remember that on July 13th last summer, I came to this strange and prosperous city and came to the long-awaited Guangzhou Power Plant. In the blink of an eye, there have been more than 300 days and nights, and it has passed away. In more than 300 days and nights, I not only opened up my horizons, but also increased my knowledge. In many aspects, my abilities have been exercised and grown, and I took the first step in my career:

From the pre-job training class held by the Guangzhou Personnel Bureau to learn the pre-job training courses in the company; from the "new and old staff basketball match" to the chemotherapy and then to the Xicun Thermal Power Plant, the Youcun Thermal Power Plant and the diesel power plant, the beautiful and beautiful We have been deeply impressed by the factory environment and the corporate culture of “unity and cooperation, and strive for progress”. The speech of the leaders’ long-term speech also provides sincere suggestions for our future work and study.

After the safety study of Xicun Thermal Power Plant and the successful passing of the exam, the beginning of the beginning of August began a two-month professional understanding internship. Starting from the B-level electrical major, the internship was carried out in the boiler, fuel, chemical, and steam turbines, and the entire Xicun Thermal Power Plant. The power generation process has a general understanding. Power plant overview: The Xicun Thermal Power Plant where I am located is a typical cogeneration unit power plant. Like other thermal power plants, boilers are used to burn pulverized coal, heat the water into superheated steam with a certain temperature and pressure, and then enter the steam turbine. Pushing the rotor to do work, which drives the generator and the exciter to generate electricity. From the point of view of energy conversion, the chemical energy in the coal is released from the combustion in the boiler and converted into the heat energy of the superheated steam. This heat energy works in the steam turbine, converts the thermal energy into the mechanical energy of the rotor, and finally converts the mechanical energy into electrical energy. Delivered out. The so-called cogeneration unit, in addition to generating electricity, also provides external heating.

Fuel professional internship:

The fuel workshop is the first energy station of the power generation system of the power plant. It is mainly responsible for the coal-in and coal-up processes of the coal-fired power plant, providing a continuous source of power for boiler combustion. The iconic building of the fuel plant is a huge coal yard and a coal belt that covers the whole plant. In the coal yard, the staff uses a crane to remove the coal from the train card of a car. Different types of coal Place it in a heap. According to the different ratios of coal burning every day, the workers grab different proportions of coal to the belt conveyor for coal blending. The start of the belt conveyor and the transportation process of the entire coal from the coal yard to the coal bunker are controlled by the program control system of the centralized control room. Through the camera disposed on the belt layer, the operator can see the entire coal transfer process at a glance.

Chemistry internship:

We know that the thermal power generation process is actually a form transformation process of the working fluid. In the boiler, the water is heated into superheated steam, and then it is pumped into the steam turbine to generate electricity. The exhausted steam is finally condensed in the condenser. Into the water, and then into the boiler recycling, which shows the status of water in the power plant.

There are many types of water in the power plant: circulating water, water supply, cooling water for various rotating machinery... The supply of these waters and the daily coal quality testing of the boilers are all done in the chemical workshop.

In the chemical workshop, there are mainly pretreatment equipment: inclined tube sedimentation tank, filter and valveless filter. These equipments mainly remove impurities and suspended solids from circulating water to ensure the water in the industrial water system and fire water system. And supply chemical demineralized water source.

Desalination equipment: sun bed, Yin bed, mixed bed, etc. As the name implies, the adsorption of these anions and cation beds removes ions from the water and ensures that the water quality of the main plant's make-up water system is qualified.

Dosing equipment: such as demineralized water plus ammonia treatment, circulating water and chlorine treatment. In order to better meet the water quality of the water needed in production, these equipment operations are essential.

Main post professional internship

The three majors of boiler, steam turbine and electric power are the three main workshops of the power plant, not only because of their important status, but also because the equipment involved in each major spans a very large number, the number is very large, and the operation technology required for operation is very high.

Boiler specialty:

Due to limited time, in the two operating weeks of the boiler B internship, only a general understanding of the boiler can be obtained: there are 5 high-temperature and high-pressure boilers with a rated evaporation of 220t/h and a pressure of 9.8Mpa. The evaporation is 220 tons and the rated pressure is 9.8Mpa. The burner used is a corrugated cuffed blunt body DC burner. The four corners are arranged in two layers. The boiler is ignited by light oil ignition. The four oil guns are arranged separately. In the next secondary air vent. The boiler combustion mode is that the burner is arranged at the four corners, and the pulverized coal forms a tangential circle in the furnace for combustion. The main tube type operation mode has been adopted, and the DCS control system has been used at present.

On the DCS control screen of the centralized control room, I learned that the boilers in our factory mainly include water supply systems, steam systems, combustion systems, flue gas systems and milling systems.

Simply put, the water supply system is shown in the following flow chart:

Feed water drop pipe saturated superheated steam

Water supply pipe economizer steam drum superheater steam turbine

Water wall steam

After the superheated water passes through the economizer, it enters the steam drum, and then absorbs the heat generated by burning the coal powder in the boiler furnace through the water wall to become a steam-water mixture, and then enters the steam drum to separate the steam and water, and separates it. The water and the number of feeds entering the boiler are again subjected to the above process, and the separated steam passes from the top of the steam drum through various heat exchangers such as superheaters, and finally becomes superheated steam meeting the parameter requirements and enters the steam turbine.

Coal coal

Raw coal bunker coal mill coal mill burner

Heat

Furnace combustion flue gas precipitator air extractor exhaust atmosphere

Slag: cold ash slag removal equipment

The fuel professionally transports the coal that has been transported to the raw coal bunker through the belt into the coal feeder. The coal pulverizer enters the coal mill to grind the pulverized coal under the conditions required for combustion, and then the primary air is blown into the burner to suspend combustion in the furnace, around the furnace. The wall is arranged with densely arranged water-cooled wall tubes. Water and steam flow through the tubes, which can absorb the radiant heat of the furnace and protect the furnace from being burned out. The center of the combustion flame has a temperature of 1500 ° C or higher, but at the outlet of the upper furnace, the temperature of the flue gas is lower than the melting point of the coal ash to prevent the molten ash from sticking to the heated surface of the flue. The larger ash particles generated by the combustion of pulverized coal are settled into the cold ash hopper at the bottom of the furnace, gradually cooled and solidified, and fall into the slagging device to form a solid slag discharge. A large number of finer ash particles leave the furnace with the flue gas, flow through a series of convective heating surfaces, gradually cool, and finally discharged by the induced draft fan through the chimney into the sky. The temperature of the exhaust gas is usually around 150 °C. In order to reduce the fly ash from the smoke exhaust and prevent environmental pollution, the flue gas leaving the boiler first flows through the electrostatic precipitator, so that most of the fly ash is captured, and finally only a small amount. The fine ash particles are discharged into the atmosphere through the chimney. The coal slag produced after the combustion of pulverized coal falls into the cold ash hopper, and the bottom pump of the furnace will periodically discharge the slag.

During the internship of the boiler, I participated in the registration of the team's account. I also learned some terminology and boiler operation knowledge that I had not touched before in the school, such as “coke” and “grass picking”. It is the work that the boiler masters have to do every day. The master tells me: Some of the things that seem quite simple, in fact, there are many mysteries in them, which are the experience gained from the accumulation of long hours of work. Like a professional who has a small number of indicators per month in the boiler, an experienced master is particularly important to a team.

Electrical engineering:

The electrical profession is the last station of energy conversion in power plants. Here, part of the electricity produced is continuously delivered to the grid, and some of it is used in various forms in the plant.

Among the 5 steam turbine generator sets of our factory, #1-4 generator power is 60,000 KW, #0 generator is 30,000 KW, the output rated voltage is 10.5KV, and the output voltage of the generator is transformed by the main transformer of the booster station. It is 6KV and 110KV, 110KV is sent to the 110KV bus, and the electric energy is transmitted to the outside through the four lines of the Sitan line, the Xiluo line, the Xiluo line and the Xiliupan line. The 6KV power is reduced by the factory transformer to a 380V factory power supply for power consumption in the plant.

In order to ensure the continuity of power supply in the plant, in addition to the normal plant power, it is also equipped with UPS power and DC backup power.

The electrical professional work is large enough to maintain the line of the whole plant, and it is involved in changing the light bulb in the control room. Since the work is exposed to high-voltage transmission lines and live equipment, pay special attention to safety. These charged equipments are not like the steam turbine and boiler professions. When they are close to the pipeline, they will have a very hot or loud sound. When operating the equipment, there will naturally be a sense of self-protection, and the electricity is invisible and even Arc damage can occur when not in contact. Therefore, electrical work should be done with protective measures, usually think more, and be careful about places where electric shock and electric shock may occur. When I entered the 6KV bus room, the master who took me told me that when I first entered the room, I had to take a small step to prevent myself from being hurt by the stepping voltage generated by the grounding inside the busbar. Safe production, a hundred years of planning. In normal work, we should actively discuss and actively sum up experience, not only in terms of safety but also in terms of technology, so that we can truly increase production and reduce consumption.

Steam engine professional internship:

The steam engine profession is the last stop of my internship. It is also the post that I will work in the future. I am very fortunate to be able to come to the steam engine class B, which is the most dynamic team in the whole factory. According to the internship arrangement, I started the internship from the three positions of steam engine auxiliary support: water supply, oxygen removal and circulating water.

Internship steam engine auxiliary guard

Water supply station:

The water supply position is the most important position of the whole factory. The importance of it can be compared with the "heart". If we compare our power plant to a person, the whole plant's water supply system and condensate system are equivalent to the human arterial system and venous system, and the condensate system is pumped out by the condensate pump, which is sequentially subjected to low addition, high removal, and then by the feed water pump. The pressurizing pump becomes a water supply system to the boiler, and the feed water pump maintains the circulation process of the working fluid throughout the production process like the human heart.

There are 6 feed pumps in Xicun Thermal Power Plant, of which #1,3,5,6 pumps are large pumps with a power output of 320m, #2 pumps are small pumps with a power output of 202, and #4 pumps are medium pumps, which are generally used during operation. Medium and small three pump main tubes operate, maintaining the feed water pressure in the range of 12MPa-14.7MPa.

Since the feed water pump is the equipment next to the deaerator, in the deaerator, the water is the saturation temperature under the corresponding pressure, so if the inlet pressure of the feed pump is not enough, the water vaporization phenomenon is easy to occur: the pump body is not normal. Noise and vibration, under high-speed operation, the damage to the pump body is very large. Therefore, when the inlet water temperature is 158 degrees Celsius, the inlet pressure should not be lower than 1.13 times of the vaporization pressure. There are two valves on the feed pump. Often switched during operation, one is a warm pump valve for warming the standby pump body, and the other is a recirculation pipe for the feed water pump. The function of the recirculation pipe is also to prevent vaporization of the feed water pump under low load or accident conditions of the reheating boiler. .

The key point in the water supply post is to ensure that the water pressure is within the normal range. There are two reasons for the fluctuation of the water pressure: the fluctuation of the boiler load, the change of the water supply, and the sudden shutdown of the running pump. During the period of water supply internship, sometimes the crew often needs to adjust the peak. At this time, we will take over the instructions of the squad, and turn the pump according to the water pressure of the feed water to meet the production needs. The water pressure is too low to meet the pressure of the boiler drum. Too high to operate is not economical. The feed pump is a large power consumer of the plant, and the proper pump can save a lot of power and reduce the power consumption of the plant.

In order to prevent the sudden running of the pump, the feed pump has many interlock protections. The most important one is the low water pressure interlocking of the water supply pipe. When the interlock is input, the pressure of the main pipe is low. Function. When the running pump is turned off or the pressure of the main pipe is as low as 12MPa, the interlock starts the standby 1 pump. If the pressure of the main pipe is lower than 12MPa for more than 5 seconds, the standby 2 pump will also start interlocking.

The normal operation of the water pump is not much. The main work of the daily routine is to carefully monitor the parameters within the normal range. The pump body is carefully inspected every two hours to adjust the bearing, shaft seal and forced cooling water, oil temperature. Etc. Several masters also explained to me the accidents and treatment methods they encountered in their many years of running positions, and also made me understand that true safe production must not stop on the rote of running regulations. What we need is a flexible application of it, an experience, and an emergency brain to calm down.

Deaeration post:

The function of the deaerator is mainly to remove non-condensed gases such as oxygen and carbon dioxide in the condensed water. At the same time, during the process of removing oxygen, the condensed water is heated to the saturation temperature under the operating pressure of the deaerator, which can increase the feed water temperature of the boiler. The heating source of the deaerator is the two-stage extraction of the steam turbine, the door rod and the shaft seal leak, the high hydrophobicity and other aspects of the steam trapping, so as to improve the thermal economy of the unit.

The principle of deaerator deoxidation is simply based on Henry's law and Dalton's law, heating the water to the saturation temperature under the working pressure of the deaerator, so as to get out of the condensed water, such as oxygen, carbon dioxide and other non-condensable gases.

There are 6 deaerators in our factory, including 5 high-pressure deaerators and 1 low-pressure deaerator, all arranged in 12-meter layers, which are spray-filled deaerators. The main task of de-oxidizing jobs is to adjust at any time. The water level and working pressure of the deaerator are within the normal range. Generally speaking, the water level fluctuation of the deaerator will be obvious. In order to maintain the water level, the deaerator must always contact the unit to switch the water supply, and pay attention to the boiler drain box. Water level, reasonable arrangement of boiler water pump. The water level of the deaerator is too low, which may cause the inlet of the feed pump to vaporize. If the water level is too high, it may go from the steam balance to the shaft seal of the unit shaft seal pipe to the unit, causing the water of the unit. Impact, directly leading to jumping.

In the deoxygenation position, I encountered a small situation: at the time of starting, the condensate was not recovered, the boiler was still in the steam, a large amount of water was discharged into the air in the form of steam, and the deaerator water level was sharp. Down, and there is no water in the boiler tank, the unit's water supply has been opened to the maximum has not much effect. At that time, the deoxygenated master decided to start the relay pump to remove the low pump. This is not the last method that will not be used to save the high water level. It is rarely done in the usual way. However, they are clear and clearly remember that the 8 meter layer has a relay water to remove the high door. Open it. I think it's very rare, but it's not difficult to think about it. As long as you take a positive and responsible attitude toward the work, you can remember or find that the rigorous work attitude of the masters left me. Very deep impression. Yes, work is to be serious, meticulous, not to be a bit sloppy, especially in our running positions, the responsibility should be in the first place.

Circulating water post:

The function of the circulating water pump is to supply cooling water to the steam turbine condenser to cool the condensing gas turbine. In addition, the circulating water pump supplies water to the oil cooler, the air cooler, the boiler ash water, and the like.

There are 6 circulating water pumps in our factory, the model is 1000HLB-16, the flow rate is 11240. Generally, 3 sets are normally operated, and the pressure is maintained at 0.05-0.08MPa. Each pump has two rotating filters and one peripheral sluice pair. The water source at the suction port of the pump is used for garbage cleaning. At the outlet of each pump, there is a chemical chlorination device interface to chlorinate and recirculate the circulating water. Previously, it was directly added with chlorine gas to prevent poisoning. The risk is relatively high. Now the toxicity is adopted. The smaller, easy-to-store sodium hypochlorite solution is chlorinated and the safety is improved a lot.

One of the tasks that must be done every day in the circulating water post is to cooperate with the maintenance personnel to clean the peripheral sluice and timely transfer the pump. In addition, attention should be paid to the circulating water pressure and the river water level. The pressure of the circulating water directly affects the vacuum degree of the unit. To the normal operation of the unit.

Internship driver:

I successfully passed the examinations and exercises of the auxiliary posts. I signed the deputy driver training contract at the beginning of April this year. I started to understand and learn about the steam turbine body. I am currently learning the #1-4 machine, which is what we often say 6W. Machine. Because the time is not too long, there is only a preliminary understanding of the whole system, and the operation is also in the stage of learning the operation rules and following the assistant driver.

#1-4 machine model is C60-8.83/1.27 type, single cylinder, impulse, single extraction steam, condensing type, with one-stage adjustment steam extraction, its rated load is 50MW, the maximum load is 60MW, the rated steam pressure is 8.8+ 0.4MPa, rated temperature is 535 ° C, rated speed 3000r / min, a total of 19 grades, regenerative extraction of a total of 5 segments, after 5, 8, 11, 15, 17 after. It mainly consists of speed control system, main steam system, condensate system, water supply system, deaeration system, vacuum system, extraction and heat recovery system, circulating water system and oil system.

I think that as a co-driver, I must first be familiar with the system, where there are valves, where there are some devices in mind; secondly, understand the things on the regulations, and slowly get through; again, when operating outside, I have to listen Clear instructions, work with the driver, follow the driver's instructions to do things. The deputy driver is the driver's hand and eyes, to understand the crew's situation, and what problems should be reflected to the driver in time, so that the driver can make adjustments operating.

to sum up

It has been a year since I first arrived in Guangzhou. I have gained more in this year than in the previous year in school, and I have successfully completed the initial transition from a student to a staff member. From the beginning of the trainee to the later independent post; from the first time holding the system diagram in the machine room and system to independent operation; from the beginning of ignorance to the later familiar with the system and equipment. I also step by step to maturity And at work to develop a hard-working, more brain-working work habits.

Hard work, more brains, learning and innovation are endless. Even though the current system of our factory has become more and more perfect, there are still many deficiencies and areas that need improvement. In the QC activities of the team, rationalization suggestions In fact, in the accidents, we can see the advice and suggestions of the employees of the radio and television industry. This is also the fine tradition passed down from generation to generation in the 70 years of broadcasting and television. Now the whole factory is setting up a “learning class”. The enthusiasm, around the two themes of "learning and innovation", is widely carried out among the employees of the whole factory, carrying forward our fine traditions and realizing its new meaning in the new form.