Heat supply
District heating systems are characterized by a combination of three main links: heat sources, heating networks and local heat consumption (heat use) systems of individual buildings and structures.
When using fossil fuel the source of thermal energy can be a boiler plant or a thermal power plant, at nuclear heat supply stations Nuclear fuel is used to produce thermal energy; in some cases, it is used as auxiliary fuel. renewable heat sources– geothermal energy, solar radiation energy, etc.
Fuel types
According to the definition of D.I. Mendeleev, “fuel is a combustible substance that is deliberately burned to produce heat.”
Well known main types of fuel-firewood, peat, coal, shale, oil residues, gas. All of them are organic compounds capable of reacting with oxygen in the air at high temperatures, which releases heat.
Fuel is produced in large quantities, its reserves in nature are very significant. The oxygen required for the reaction is taken from the surrounding air. As a result of the reaction, highly heated combustion gases are obtained, the heat of which is used in the boiler plant. The cooled gases are released into the atmosphere through the chimney.
For combustion can use both natural and artificial fuels, obtained after processing natural fuel in order to isolate valuable products from it, which include resins, gasoline, benzenes, mineral lubricating oils, paints, pharmaceutical products, ammonium sulfate used for agricultural needs, etc.
Solid fuel:
a) natural - firewood, coal, anthracite, peat;
b) artificial - charcoal, coke and pulverized coal, which is obtained from crushed coal.
Liquid fuel:
a) natural - oil;
b) artificial - gasoline, kerosene, fuel oil, tar.
Gaseous fuel:
a) natural - natural gas;
b) artificial - generator gas obtained from the gasification of various types of solid fuel (peat, firewood, coal, etc.), coke, blast furnace, lighting and other gases.
Types of boiler installations
Stationary boiler room is no longer the only option for autonomous heating. Equipment requires a room - but its location can be any.
Block boiler rooms for example, it can be placed both in the basement and on the roof (if a number of conditions are met). In addition, the boiler houses themselves have become much more reliable. This is primarily due to the fact that manufacturing plants began to offer turnkey installations: all the necessary equipment is already installed in blocks or in a module and you can start the installation. Accordingly, there are two types of boiler plants: block and modular boiler rooms. Both types of structures are convenient in terms of transportation (as a rule, they are transported by rail or road transport).
Basic boiler room equipment: boiler, water pump, liquid container, pipes, burner device. Some also purchase additional equipment that helps save money: non-volatile boilers, boilers with electric ignition function, two-pass and combined cast iron boilers.
Relatively recently, thermal equipment appeared on the market TKU – transportable boiler units. The need for them arose with the emergence of new industries that are located in buildings not connected to the central heating system. The advantage of the new product is that it is quite easy to transport (the modular design has wheels), it is easy to handle and does not require the constant presence of an operator. In addition, as a rule, TCUs are fully automated, so managing them is quite simple. At the same time, it is capable of generating a sufficient amount of heat and does not require connection to communications.
Classification of boiler houses.
Depending on where the installation is located, the following are distinguished:
· Roof;
· Built into the building;
· Block-modular;
· Frame.
In every heating system, its main element is the boiler. It performs the main function - heating. Depending on the basis on which the entire system and the boiler in particular operate, there are the following types of boilers :
§ Steam boilers
§ Hot water;
§ Mixed;
§ Boilers using diathermic oil.
Any heating system works, as previously noted, from one or another type raw materials, fuel or natural resource. IN Depending on this, boilers are divided into:
· Solid fuel. For this, firewood, coal and other types of solid fuel are used.
· Liquid fuels – oil, gasoline, fuel oil and others.
· Gas.
· Mixed or combined. It is assumed that various types and types of fuel will be used.
Introduction
General information and concept about boiler systems
1 Classification of boiler installations
Types of heating boilers for heating buildings
1 Gas boilers
2 Electric boilers
3 Solid fuel boilers
Types of boilers for heating buildings
1 Gas tube boilers
2 Water tube boilers
Conclusion
Bibliography
Introduction
Living in temperate latitudes, where most of the year is cold, it is necessary to ensure heat supply to buildings: residential buildings, offices and other premises. Heat supply ensures comfortable living if it is an apartment or house, productive work if it is an office or warehouse.
First, let’s figure out what is meant by the term “Heat supply”. Heat supply is the supply of hot water or steam to the heating systems of a building. The usual sources of heat supply are thermal power plants and boiler houses. There are two types of heat supply to buildings: centralized and local. With centralized supply, individual areas (industrial or residential) are supplied. For the efficient operation of a centralized heating network, it is built by dividing it into levels, the work of each element is to perform one task. With each level, the element's task decreases. Local heat supply - supplying heat to one or more houses. Centralized heating networks have a number of advantages: reduction of fuel consumption and cost reduction, use of low-grade fuel, improvement of the sanitary condition of residential areas. The centralized heat supply system includes a source of thermal energy (CHP), a heating network and heat-consuming units. A CHP plant combines the production of heat and energy. Sources of local heat supply are stoves, boilers, water heaters.
My goal is to get acquainted with general information and the concept of boiler systems, which boilers are used to supply heat to buildings.
1. General information and concepts about boiler systems
A boiler plant is a complex of devices located in special rooms and used to convert the chemical energy of fuel into the thermal energy of steam or hot water. The main elements of a boiler installation are a boiler, a combustion device (furnace), feed and draft devices.
A boiler is a heat exchange device in which heat from the hot combustion products of fuel is transferred to water. As a result, water is converted into steam in steam boilers, and heated to the required temperature in hot water boilers.
The combustion device is used to burn fuel and convert its chemical energy into heat of heated gases.
Feeding devices (pumps, injectors) are designed to supply water to the boiler.
The draft device consists of blower fans, a gas-air duct system, smoke exhausters and a chimney, which ensure the supply of the required amount of air to the firebox and the movement of combustion products through the boiler flues, as well as their removal into the atmosphere. The combustion products, moving through the flues and coming into contact with the heating surface, transfer heat to the water.
To ensure more economical operation, modern boiler systems have auxiliary elements: a water economizer and an air heater, which serve to heat water and air, respectively; devices for fuel supply and ash removal, for cleaning flue gases and feed water; thermal control devices and automation equipment that ensure normal and uninterrupted operation of all parts of the boiler room.
Depending on the purpose for which thermal energy is used, boiler houses are divided into energy, heating and industrial and heating.
Energy boiler houses supply steam to steam power plants that generate electricity, and are usually part of a power plant complex. Heating and industrial boiler houses are built at industrial enterprises and provide thermal energy to heating and ventilation systems, hot water supply to buildings and production processes. Heating boiler houses are intended for the same purposes, but serve residential and public buildings. They are divided into free-standing, interlocking, i.e. adjacent to other buildings, and built into buildings. Recently, more and more often, separate enlarged boiler houses are being built with the expectation of servicing a group of buildings, a residential area, or a microdistrict. The installation of boiler rooms built into residential and public buildings is currently permitted only with appropriate justification and agreement with the sanitary inspection authorities. Low-power boiler houses (individual and small group) usually consist of boilers, circulation and make-up pumps and draft devices. Depending on this equipment, the dimensions of the boiler room are mainly determined. Boiler houses of medium and high power - 3.5 MW and above - differ in the complexity of the equipment and the composition of service and utility premises. The space-planning solutions of these boiler houses must meet the requirements of the Sanitary Standards for the Design of Industrial Enterprises.
1.1 Classification of boiler installations
Boiler installations, depending on the nature of consumers, are divided into energy, production and heating and heating. Based on the type of coolant produced, they are divided into steam (for generating steam) and hot water (for producing hot water).
Power boiler plants produce steam for steam turbines in thermal power plants. Such boiler houses are usually equipped with high- and medium-power boiler units that produce steam with increased parameters.
Industrial heating boiler systems (usually steam) produce steam not only for industrial needs, but also for heating, ventilation and hot water supply.
Heating boiler systems (mainly hot water, but they can also be steam) are designed to service heating systems for industrial and residential premises.
Depending on the scale of heat supply, heating boiler houses are divided into local (individual), group and district.
Local boiler houses are usually equipped with hot water boilers that heat water to a temperature of no more than 115°C or steam boilers with a working pressure of up to 70 kPa. Such boiler houses are designed to supply heat to one or more buildings.
Group boiler systems provide heat to groups of buildings, residential areas or small neighborhoods. Such boiler houses are equipped with both steam and hot water boilers, which, as a rule, have a higher heating capacity than boilers for local boiler houses. These boiler rooms are usually located in specially constructed separate buildings.
District heating boiler houses are used to supply heat to large residential areas: they are equipped with relatively powerful hot water or steam boilers.
2. Types of heating boilers
.1 Gas boilers
If main gas is supplied to the site, then, in the vast majority of cases, heating the house using a gas boiler is optimal, since you will not find cheaper fuel. There are many manufacturers and models of gas boilers. To make it easier to understand this diversity, we will divide all gas boilers into two groups: floor-standing boilers and wall-mounted ones. Wall-mounted and floor-mounted boilers have different designs and components.
A floor-standing boiler is a traditional, conservative thing that has not undergone major changes over many decades. The heat exchanger of floor-standing boilers is usually made of cast iron or steel. There are different opinions about which material is better. On the one hand, cast iron is less susceptible to corrosion; a cast iron heat exchanger is usually made thicker, which can have a positive effect on its service life. At the same time, a cast iron heat exchanger also has disadvantages. It is more fragile, and, therefore, there is a risk of microcracks forming during transportation and loading and unloading. In addition, during the operation of cast iron boilers when using hard water, due to the design features of cast iron heat exchangers and the properties of cast iron itself, over time they are destroyed as a result of local overheating. If we talk about steel boilers, they are lighter and are not very susceptible to shock during transportation. At the same time, if used incorrectly, the steel heat exchanger can corrode. But it is not very difficult to create normal operating conditions for a steel boiler. It is important that the temperature in the boiler does not fall below the dew point temperature. A good designer will always be able to create a system that will maximize the service life of the boiler. In turn, all floor-standing gas boilers can be divided into two main groups: with atmospheric and with forced-air (sometimes called replaceable, fan, mounted) burners. The first ones are simpler, cheaper and at the same time work quieter. Boilers with forced-air burners have greater efficiency and are noticeably more expensive (taking into account the cost of the burner). Boilers for working with forced-air burners have the ability to install burners operating either on gas or liquid fuel. The power of floor-standing gas boilers with an atmospheric burner, in most cases, ranges from 10 to 80 kW (but there are companies producing more powerful boilers of this type), while models with replaceable inflatable
burners can reach a power of several thousand kW. In our conditions, another parameter of a gas boiler is very important - the dependence of its automation on electricity. After all, in our country there are often cases of problems with electricity - somewhere it is supplied intermittently, and in some places it is completely absent. Most modern gas boilers with atmospheric burners operate regardless of the availability of power. As for imported boilers, it is clear that there are no such problems in Western countries, and the question often arises: are there any good imported gas boilers that operate autonomously from electricity? Yes they exist. This autonomy can be achieved in two ways. The first is to simplify the boiler control system as much as possible and, due to the almost complete absence of automation, achieve independence from electricity (this also applies to domestic boilers). In this case, the boiler can only maintain the specified coolant temperature, and will not be guided by the air temperature in your room. The second method, more progressive, is using a heat generator, which from the heat generates the electricity necessary for the operation of the boiler automation. These boilers can be used with remote room thermostats, which will control the boiler and maintain the room temperature you set.
Gas boilers can be single-stage (operate at only one power level) and two-stage (2 power levels), as well as with modulation (smooth control) of power, since the full power of the boiler is required for approximately 15-20% of the heating season, and 80-85% Since it is unnecessary, it is clear that it is more economical to use a boiler with two power levels or power modulation. The main advantages of a two-stage boiler are: increasing the service life of the boiler by reducing the frequency of burner on/off, working at the 1st stage with reduced power and reducing the number of burner on/offs allows you to save gas, and, consequently, money.
Wall-mounted boilers appeared relatively recently, but even during this relatively short period of time they have won a lot of supporters all over the world. One of the most accurate and comprehensive definitions of these devices is “mini boiler room”. This term did not appear by chance, because in a small case there is not only a burner, a heat exchanger and a control device, but also, in most models, one or two circulation pumps, an expansion tank, a system that ensures the safe operation of the boiler, a pressure gauge, a thermometer, and many others elements that a normal boiler house cannot operate without. Despite the fact that wall-mounted boilers implement the most advanced technical developments in the field of heating, the cost of “wall-mounted boilers” is often 1.5-2 times lower than that of their floor-standing counterparts. Another significant advantage is ease of installation. Buyers often believe that ease of installation is a benefit that should only concern installers. This is not entirely true, because the amount that a real consumer will have to pay for installing a wall-mounted boiler or for installing a boiler room, where the boiler, boiler, pumps, expansion tank and much more are installed separately, differs very significantly. Compactness and the ability to fit a wall-mounted boiler into almost any interior is another advantage of this class of boilers.
Despite the fact that wall-mounted boilers implement the most advanced technical developments in the field of heating, the cost of “wall-mounted boilers” is often 1.5-2 times lower than that of their floor-standing counterparts. Another significant advantage is ease of installation. Buyers often believe that ease of installation is a benefit that should only concern installers. This is not entirely true, because the amount that a real consumer will have to pay for installing a wall-mounted boiler or for installing a boiler room, where the boiler, boiler, pumps, expansion tank and much more are installed separately, differs very significantly. Compactness and the ability to fit a wall-mounted boiler into almost any interior is another advantage of this class of boilers.
According to the method of removing exhaust gases, all gas boilers can be divided into models with natural draft (removal of exhaust gases occurs due to the draft created in the chimney) and with forced draft (using a fan built into the boiler). Most companies producing wall-mounted gas boilers produce models with both natural draft and forced draft. Boilers with natural draft are well known to many and a chimney above the roof does not surprise anyone. Boilers with forced draft appeared quite recently and have many advantages during installation and operation. As mentioned above, exhaust gases are removed from these boilers using a built-in fan. Such models are ideal for rooms without a traditional chimney, since combustion products in this case are discharged through a special coaxial chimney, for which it is enough to make only a hole in the wall. A coaxial chimney is also often called a “pipe in a pipe”. Through the inner pipe of such a chimney, combustion products are removed to the street using a fan, and air enters through the outer pipe. In addition, these boilers do not burn oxygen from the room, do not require additional flow of cold air into the building from the street to support the combustion process, and reduce investment during installation, because there is no need to make an expensive traditional chimney, instead of which a short and inexpensive coaxial chimney can be successfully used. Forced draft boilers are also used in cases where there is a traditional chimney, but taking combustion air from the room is undesirable.
According to the type of ignition, wall-mounted gas boilers can be with electric or piezo ignition. Boilers with electric ignition are more economical, since there is no igniter with a constantly burning flame. Due to the absence of a constantly burning wick, the use of boilers with electric ignition can significantly reduce gas consumption, which is most important when using liquefied gas. Savings of liquefied gas can reach 100 kg per year. There is another advantage of boilers with electric ignition - in the event of a temporary power outage, the boiler will automatically turn on when the power supply is restored, while a model with piezo ignition will have to be turned on manually.
According to the type of burner, wall-mounted boilers can be divided into two types: with a regular burner and with a modulating burner. The modulating burner provides the most economical operating mode, since the boiler automatically adjusts its power depending on the heat demand. In addition, the modulating burner provides maximum comfort in DHW mode, allowing you to maintain the hot water temperature at a constant, specified level.
Most wall-mounted boilers are equipped with devices that ensure their safe operation. So, a flame presence sensor turns off the gas supply when the flame goes out, a blocking thermostat turns off the boiler when the boiler water temperature rises unexpectedly, a special device turns off the boiler when the power goes out, another device blocks the boiler when the gas is turned off. There is also a device for shutting off the boiler when the coolant volume drops below normal and a draft control sensor.
2.2 Electric boilers
There are several main reasons limiting the spread of electric boilers: not all areas have the opportunity to allocate the electrical power required for heating a house (for example, a house with an area of 200 sq. m requires approximately 20 kW), the very high cost of electricity, and power outages. Electric boilers really have many advantages. Among them: relatively low price, ease of installation, light and compact, they can be hung on the wall, as a result - space saving, safety (no open flame), ease of operation, an electric boiler does not require a separate room (boiler room), an electric boiler does not require chimney installation, the electric boiler does not require special care, it is silent, the electric boiler is environmentally friendly, there are no harmful emissions or foreign odors. In addition, in cases where power outages are possible, an electric boiler is often used in conjunction with a backup solid fuel boiler. The same option is also used to save energy (first the house is heated using cheap solid fuel, and then the temperature is automatically maintained using an electric boiler).
It is worth noting that when installed in large cities with strict environmental standards and coordination problems, electric boilers also often outperform all other types of boilers (including gas ones). Briefly about the design and configuration of electric boilers. An electric boiler is a fairly simple device. Its main elements are a heat exchanger, consisting of a tank with electric heaters (heating elements) mounted in it, and a control and regulation unit. Electric boilers from some companies are supplied already equipped with a circulation pump, programmer, expansion tank, safety valve and filter. It is important to note that low-power electric boilers come in two different versions - single-phase (220 V) and three-phase (380 V).
Boilers with a power of more than 12 kW are usually produced only three-phase. The vast majority of electric boilers with a power of more than 6 kW are produced in multi-stage versions, which makes it possible to rationally use electricity and not turn on the boiler at full power during transition periods - in spring and autumn. When using electric boilers, rational use of energy is most important.
2.3 Solid fuel boilers
Fuel for solid fuel boilers can be firewood (wood), brown or hard coal, coke, peat briquettes. There are both “omnivorous” models that can operate on all of the above types of fuel, and those that operate on some of them, but have greater efficiency. One of the main advantages of most solid fuel boilers is that with their help you can create a completely autonomous heating system. Therefore, such boilers are more often used in areas where there are problems with the supply of main gas and electricity. There are two more arguments in favor of solid fuel boilers - availability and low cost of fuel. The disadvantage of most representatives of boilers of this class is also obvious - they cannot operate in fully automatic mode and require regular loading of fuel.
It is worth noting that there are solid fuel boilers that combine the main advantage of models that have existed for many years - independence from electricity and are capable of automatically maintaining a given temperature of the coolant (water or antifreeze). Automatic temperature maintenance is carried out as follows. The boiler is equipped with a sensor that monitors the temperature of the coolant. This sensor is mechanically connected to the damper. If the coolant temperature becomes higher than the one you set, the damper automatically closes and the combustion process slows down. When the temperature drops, the damper opens slightly. Thus, this device does not require connection to an electrical network. As mentioned above, most traditional solid fuel boilers can operate on brown and hard coal, wood, coke, and briquettes.
Overheating protection is provided by the presence of a cooling water circuit. This system can be controlled manually, i.e. when the temperature of the coolant increases, it is necessary to open the valve on the coolant outlet pipe (the valve on the inlet pipe is constantly open). In addition, this system can also be controlled automatically. To do this, a temperature reduction valve is installed on the outlet pipe, which will automatically open when the coolant reaches the maximum temperature. In addition, what fuel to use to heat your home, it is very important to correctly select the required boiler power. Typically power is expressed in kW. Approximately 1 kW of power is required to heat 10 square meters. m of a well-insulated room with a ceiling height of up to 3 m. It must be borne in mind that this formula is very approximate.
The final power calculation should be trusted only to professionals who, in addition to the area (volume), will take into account many other factors, including the material and thickness of the walls, type, size, number and location of windows, etc.
Boilers with pyrolysis combustion of wood have greater efficiency (up to 85%) and allow automatic power control.
The disadvantages of pyrolysis boilers include, first of all, a higher price compared to traditional solid fuel boilers. By the way, there are boilers that work not only on wood, but also boilers on straw. When choosing and installing a solid fuel boiler, it is very important to comply with all requirements for the chimney (its height and internal cross-section).
3. Types of boilers for heating buildings
gas boiler heating supply
There are two main types of steam boilers: gas-tube and water-tube. All boilers (fire-tube, smoke-combustion and smoke-fire-tube) in which high-temperature gases pass inside fire and smoke tubes, giving off heat to the water surrounding the pipes, are called gas-tube. In water-tube boilers, heated water flows through the pipes, and flue gases wash the outside of the pipes. Gas-tube boilers rest on the side walls of the firebox, while water-tube boilers are usually attached to the frame of the boiler or building.
3.1 Gas-tube boilers
In modern thermal power engineering, the use of gas-tube boilers is limited to a thermal power of about 360 kW and an operating pressure of about 1 MPa.
The fact is that when designing a high-pressure vessel, such as a boiler, the wall thickness is determined by the given values of diameter, operating pressure and temperature.
If the specified limit parameters are exceeded, the required wall thickness turns out to be unacceptably large. In addition, it is necessary to take into account safety requirements, since the explosion of a large steam boiler, accompanied by the instantaneous release of large volumes of steam, can lead to disaster.
Given the current level of technology and existing safety requirements, gas-tube boilers can be considered obsolete, although many thousands of such boilers with a thermal power of up to 700 kW are still in operation, serving industrial enterprises and residential buildings.
3.2 Water tube boilers
The water tube boiler was developed in response to the ever-increasing demands for increased steam output and steam pressure. The fact is that when steam and high-pressure water are in a pipe of not very large diameter, the requirements for wall thickness turn out to be moderate and easily met. Water-tube steam boilers are much more complex in design than gas-tube boilers. However, they heat up quickly, are virtually explosion-proof, are easily adjusted to accommodate load changes, are easy to transport, are easily reconfigurable in design, and can tolerate significant overloading. The disadvantage of a water-tube boiler is that its design contains many units and components, the connections of which should not allow leaks at high pressures and temperatures. In addition, the units of such a boiler operating under pressure are difficult to access during repairs.
A water-tube boiler consists of bundles of tubes connected at their ends to a drum (or drums) of moderate diameter, the entire system being mounted above the combustion chamber and enclosed in an outer casing. The guide baffles force the flue gases to pass through the tube bundles several times, resulting in more complete heat transfer. Drums (of various designs) serve as reservoirs of water and steam; their diameter is chosen to be minimal in order to avoid difficulties characteristic of gas-tube boilers. Water tube boilers come in the following types: horizontal with a longitudinal or transverse drum, vertical with one or more steam drums, radiation, vertical with a vertical or transverse drum, and combinations of these options, in some cases with forced circulation.
Conclusion
So, in conclusion, we can say that boilers are an important element in the heat supply of a building. When choosing stakes, it is necessary to take into account technical, techno-economic, mechanical and other indicators for the best type of heat supply to the building. Boiler installations, depending on the nature of consumers, are divided into energy, production and heating and heating. Based on the type of coolant produced, they are divided into steam and hot water.
My work examines gas, electric, solid fuel types of boilers, as well as types of boilers, such as gas-tube and water-tube boilers.
From the above, it is worth highlighting the pros and cons of various types of boilers.
The advantages of gas boilers are: cost-effectiveness compared to other types of fuel, ease of operation (operation of the boiler is fully automated), high power (you can heat a large area), the ability to install equipment in the kitchen (if the boiler power is up to 30 kW), compact size, environmental friendliness ( few harmful substances will be released into the atmosphere).
Disadvantages of gas boilers: before installation, you must obtain permission from Gazgortekhnadzor, the danger of gas leakage, certain requirements for the room where the boiler is installed, the presence of automation that blocks the access of gas in the event of a leak or lack of ventilation.
Advantages of electric boilers: low price, ease of installation, compactness and light weight - electric boilers can be hung on the wall and save usable space, safety (no open flame), ease of operation, electric boilers do not require a separate room (boiler room), do not require installation of a chimney, do not require special care, are silent, environmentally friendly - there are no harmful emissions or foreign odors.
The main reasons limiting the spread of electric boilers are not in all areas, it is possible to allocate several tens of kilowatts of electricity, the fairly high cost of electricity, and power outages.
First, let's highlight the disadvantages of solid fuel boilers: first of all, solid fuel heating boilers use solid fuel, which has a relatively low heat transfer. Indeed, in order to properly heat a large house, you will have to spend a lot of fuel and time. In addition, the fuel will burn out quite quickly - in two to four hours. After this, if the house is not heated enough, you will have to light the fire again. Moreover, to do this, you will first need to clean the firebox from the formed coals and ash. Only after this will it be possible to add fuel and rekindle the fire. All this is done by hand.
On the other hand, solid fuel boilers also have some advantages. For example, not being picky about fuel. Indeed, they can work effectively on all types of solid fuel - wood, peat, coal and, in general, anything that can burn. Of course, such fuel can be obtained quickly and not too expensively in most regions of our country, which is a serious argument in favor of solid fuel boilers. In addition, these boilers are completely safe, so they can be installed either in the basement of the house or just nearby. At the same time, you can be sure that a terrible explosion will not occur due to a fuel leak. Of course, you don’t have to equip a special place for fuel storage - bury gas or diesel fuel storage tanks in the ground.
Currently, there are two main types of steam boilers, namely gas-tube and water-tube. Gas-tube boilers include those boilers in which high-temperature gases flow inside flame and smoke tubes, thereby giving off heat to the water that surrounds the pipes. Water tube boilers are distinguished by the fact that heated water flows through the pipes, and the outside of the pipes is washed with gases.
Bibliography
1.Boyko E.A., Shpikov A.A., Boiler installations and steam generators (structural characteristics of power boiler units) - Krasnoyarsk, 2003.
.Bryukhanov O.N. Gasified boiler units. Textbook. INFRA-M. - 2007.
.GOST 23172-78. Kotlystationary. Terms and definitions. - Definition of boilers “to produce steam or to heat water under pressure.”
.Dvoinishnikov V.A. et al. Design and calculation of boilers and boiler installations: Textbook for technical schools specializing in “Boiler Engineering” / V.A. Dvoinishnikov, L.V. Deev, M.A. Izyumov. - M.: Mechanical Engineering, 1988.
.Levin I.M., Botkachik I.A., Smoke exhausters and fans of powerful power plants, M. - L., 1962.
.Maksimov V.M., Boiler units with large steam capacity, M., 1961.
.Tikhomirov K.V. Sergeenko E. S. "Heating engineering, heat and gas supply and ventilation." Textbook for universities. 4th ed., revised. and additional - M.: Stroyizdat, 1991
.Encyclopedia "Around the World" is a popular science online encyclopedia.
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Water steam is used in steam engines, steam power plants of thermal power plants, in technological installations of enterprises, in heating, ventilation and hot water supply systems of industrial, public and residential buildings. Hot water - mainly in heating and ventilation systems of buildings, as well as to meet the plumbing needs of production and the population. Sometimes - for heat supply to process consumers. In many cases, steam or hot water produced in boilers is used as a coolant to supply heat to heating points, called central heating points (CHP), in which heat exchangers (recuperative or mixing) are installed to heat the water circulating between the central heating point and the consumers connected to them (double-circuit circuits). It is also possible to connect consumers to central heating stations through additional heating points (boiler rooms) to supply heat to individual or groups of consumers (three-circuit schemes). For more details, see [9].
Steam and hot water in boiler houses, with the exception of boiler houses with nuclear reactors, are obtained using the heat of burned organic fuel in special units called steam, water-heating and steam-water-heating boilers, respectively.
Depending on their purpose, boiler houses are divided into energy, industrial, industrial heating, boiler houses of the public utility sector (KBS) or housing and communal services (HCS). The latter cover the heat needs of housing and communal services mainly for heating and hot water supply. Power boiler houses are designed to supply steam to turboelectric generators of thermal power plants (TPPs) and steam engines. The power boiler house is an integral part of the thermal power plant. Industrial boiler houses provide steam and hot water to process consumers and heating, ventilation, air conditioning and hot water supply systems.
In industry, large technological consumers of steam are evaporation, distillation, rectification, drying plants, chemical reactors, installations for sorption-desorption purification of natural gas from hydrogen sulfide and carbon dioxide, washing machines, presses, heated baths of galvanic lines, machines for lamination (coating with polymer films) paper, etc.
In table Table 1.1 shows some characteristics of heat consumption of enterprises in various industries [2].
Industrial heating boiler houses are designed to generate steam or hot water, used both in production and for heating industrial, administrative and other buildings on the territory of the enterprise, as well as heating and supplying hot water to nearby residential areas.
Steam boilers are most often installed in industrial and industrial heating boiler houses. Heating boiler houses produce mainly hot water intended for heating buildings and meeting the household needs of the population. Therefore, both steam and hot water boilers are used in heating boiler houses. At modern heat supply stations for housing and communal services there are mainly water heating boilers. And the steam boilers available there are to cover the station’s own needs, mainly to supply steam to the fuel oil industry (in gas boiler houses, fuel oil is used as a backup or emergency fuel). A promising direction is the use of combined steam-water-heating boilers in heating boilers. In the last ten years, autonomous roof-mounted and block-modular boiler houses, steam and water heating houses have also become widespread. Block-modular boiler rooms are factory-installed and delivered to the installation site in assembled form. To put them into operation, it is enough to install them after delivery, connect them to consumers and a fuel supply source, and carry out commissioning work in the prescribed manner.
The principal thermal diagrams of a steam and hot water boiler plant are shown in Fig. 1.1 and 1.2.
Depending on the number of consumers connected to the heat supply source of the housing and communal services, district, group and individual boiler houses are distinguished [1]. District and group boiler houses are located, as a rule, in separate buildings. Individual - often in basements or on the roofs of heated buildings. Autonomous automated rooftop boiler houses running on natural gas have become widespread only in recent years.
Rice. 1.1. Schematic thermal diagram of a steam boiler house
1 – boiler units; 2 – live steam collector; 3 – reduction unit; 4 – steam collector R= 0.6 MPa; 5 – steam collector R= 0.3…0.12 MPa; 6 – continuous blowing separator; 7 – steam-water heaters; 8 – condensate coolers after steam-water heaters; 9 – thermal deaerator; 10 – vapor cooler; 11 – water-water heater; 12 – steam-water heater; 13 – chemical water treatment device; 14 – electrically driven feed pumps; 15 – steam feed pumps; 16 – network pumps; 17 – make-up pump;
symbols of pipelines: T1 – hot water supplied for heating and ventilation (HV); T2 – return water from the heating system; T21 – reverse, after heating in the condensate cooler (OK); T3 – domestic hot water supply, supply; T4 – return water from the hot water supply system; T5 – hot water for technological needs; T6 - return water after technological needs; T61 – return water after OK; T71 – steam from the boiler; T73 – pair after the reducing device ( R= 0.3...0.12 MPa); T72 – pair after reduction ( R= 0.6 MPa); T74 – steam from the continuous blowing separator; T79 – vapor from the deaerator; T81 – condensate at R= 0.6 MPa; T82 – condensate at R= 0.2 MPa; T84 – condensate from production; T91 – feed water; T92 – continuous blowing; T93 – purge water after evaporation; B1 – raw water from the water supply; B20 – water after chemical water treatment
Rice. 1.2. Schematic thermal diagram of a hot water boiler house
1 – hot water boiler; 2 – network pump; 3 – recirculation pump; 4 – recirculation regulator; 5 – heating water temperature regulator; 6 – vacuum deaerator; 7 – deaerator vapor cooler; 8 – water-water heat exchanger; 9 – chemically purified water pump; 10 – gas-water ejector; 11 – working water supply tank; 12 – raw water pump; 13 – heat exchanger-raw water heater; 14 – transfer pump; 15 – make-up water storage tank; 16 – make-up pump; 17 – water temperature regulator in front of the deaerator; a, b – supply and return of hot water from production; c – raw water from the tap; d – return of network water
burners
water treatment plants
boiler pipes, shut-off valves
heat generators
water level indicators
sensors and controllers
and much more
Gas boiler houses
Gas boiler rooms are the most common type of boiler installations today. Obvious advantages are their low construction and operating costs compared to other types of boiler installations. The country's extensive gas pipeline network, which is constantly developing, allows gas to be supplied to almost any point. This leads to a reduction in the cost of delivering working fuel by conventional transport. In addition, gas has a higher heat capacity and heat transfer compared to other types of fuel; it leaves fewer harmful substances after combustion.At industrial enterprises, gas boiler houses are the main source of heat supply for technological processes and for providing heat to working personnel. At the same time, gas boiler rooms have also begun to appear more often in private residential buildings. People appreciated the benefits of such installations.
Gas boiler houses are an irreplaceable source of energy, cheaper than electricity.
Modular boiler rooms
Modular boiler rooms are ready-made engineering systems that can be easily transported and installed anywhere. Using modular boiler rooms, you can significantly save on design and installation, since these systems are usually installed ready-made in a container and equipped with all the necessary equipment for operation and automation of the process.Modular boiler rooms include the following equipment:
hot water boilers
technological equipment
automation systems
water treatment systems
and much more
A boiler is a heat exchange device in which heat from the hot combustion products of fuel is transferred to water. As a result, water is converted into steam in steam boilers, and heated to the required temperature in hot water boilers.
The combustion device is used to burn fuel and convert its chemical energy into heat of heated gases.
Feeding devices (pumps, injectors) are designed to supply water to the boiler.
The draft device consists of blower fans, a gas-air duct system, smoke exhausters and a chimney, which ensure the supply of the required amount of air to the firebox and the movement of combustion products through the boiler flues, as well as their removal into the atmosphere. The combustion products, moving through the flues and coming into contact with the heating surface, transfer heat to the water.
To ensure more economical operation, modern boiler systems have auxiliary elements: a water economizer and an air heater, which serve to heat water and air, respectively; devices for fuel supply and ash removal, for cleaning flue gases and feed water; thermal control devices and automation equipment that ensure normal and uninterrupted operation of all parts of the boiler room.
Classification.
Block modular boiler houses with power from 200 kW to 10000 kW (model range)
There are individually designed boiler rooms of different types:
Roof boiler rooms
Freestanding boiler rooms
Block and modular boiler rooms
Built-in boiler rooms
Attached boiler rooms
Transportable and mobile boiler rooms
All operating parameters are controlled by automated control systems without human presence.
Compound boiler rooms in basic version:
Water heating boilers
The reliability of heat supply is guaranteed by the presence in the composition boiler rooms at least two boiler units, represented by steel fire-tube boilers from reliable and successfully proven German companies on the Russian market Buderus, Viessmann.
Weishaupt burners
In boiler houses they are used burners from the German company Weishaupt. Used to burn natural gas LN burners, ensuring a low content of harmful impurities in combustion products.
Domestic gas supply
Gas supply system equipment boiler rooms regulates gas flow and controls the levels of minimum and maximum gas pressure. In case of emergency situations, the flow of gas into boiler room stops automatically.
Regulating the temperature of the network water
Microprocessor programmable controllers are used that automatically control the system for regulating the temperature of network water depending on the outside air temperature and the needs of the Consumer.
Pump equipment
Boiler circuit pumps ensure independent operation boilers. Twin circulation pumps in the network circuit guarantee 100% redundancy.
Water treatment and pressure maintenance in the heating system
The water treatment unit reduces the hardness of boiler water and prevents the formation of scale on the heat exchange surfaces of the equipment. The pressure maintenance device automatically refills the boiler and network circuits with water, ensuring the required level of pressure in the heating system.
Hydraulic separator
Equipment for hydraulic decoupling of the boiler and network circuits allows for stable operation of the boiler house in systems with a large volume of water under intense dynamics of changes in flow rates, temperature and pressure.
Signaling
Fire alarm systems and gas alarm systems for methane and carbon monoxide are installed in the boiler rooms.
Metering devices
Instrumentation and measuring instruments registered in the State Register of Measuring Instruments are used, allowing for:
– accounting of supplied thermal energy
– accounting of cold water consumption
– gas consumption metering
– metering of consumed electricity
– control of operating parameters of boiler room equipment.
Comprehensive automation
The integrated automation system ensures stable operation of boiler rooms without the constant presence of maintenance personnel. Remote control of the operation of the main equipment of the boiler room is carried out using a remote alarm control panel (included in the scope of delivery).
Modem communication for remote dispatching
Boiler rooms at the time of installation or any period of further operation, they can be connected to modern remote dispatch systems. The complex automation system has a built-in modem unit for transmitting data on the operation of boiler room equipment via telephone communication channels or the Internet.
Smoke pipes
The outer and inner walls of the chimneys are made of stainless steel and insulated with rigid mineral wool insulation. The chimneys used have a certificate of compliance with fire safety standards. A separate pipe is installed for each heating boiler. Chimneys with a height of 6 meters are included in the scope of supply for boiler houses from 200 kW to 10 MW. If desired, the Buyer can refuse the chimney, and also has the opportunity to install chimneys of a different height.
Boiler rooms, depending on sizes and quantities boilers, consist of one or more blocks. Depending on climatic conditions, the metal frame of the modules is insulated with rigid three-layer sandwich panels with mineral wool insulation with a thickness of 80 to 150 mm. The characteristics of the module enclosing structures comply with regulatory requirements for fire resistance and fire safety.
Low-power boiler houses (individual and small group) usually consist of boilers, circulation and make-up pumps and draft devices. Depending on this equipment, the dimensions of the boiler room are mainly determined.
Boiler houses of medium and high power - 3.5 MW and above - differ in the complexity of the equipment and the composition of service and utility premises. The space-planning solutions of these boiler houses must meet the requirements of the Sanitary Standards for the Design of Industrial Enterprises (SI 245-71), SNiP P-M.2-72 and 11-35-76.
Classification of boiler installations
Boiler installations, depending on the nature of consumers, are divided into energy, production and heating and heating. Based on the type of coolant produced, they are divided into steam (for generating steam) and hot water (for producing hot water).
Power boiler plants produce steam for steam turbines in thermal power plants. Such boiler houses are usually equipped with high- and medium-power boiler units that produce steam with increased parameters.
Industrial heating boiler systems (usually steam) produce steam not only for industrial needs, but also for heating, ventilation and hot water supply.
Heating boiler systems (mainly hot water, but they can also be steam) are designed to service heating systems for industrial and residential premises.
Depending on the scale of heat supply, heating boiler houses are divided into local (individual), group and district.
Local boiler houses are usually equipped with hot water boilers that heat water to a temperature of no more than 115°C or steam boilers with a working pressure of up to 70 kPa. Such boiler houses are designed to supply heat to one or more buildings.
Group boiler systems provide heat to groups of buildings, residential areas or small neighborhoods. Such boiler houses are equipped with both steam and hot water boilers, which, as a rule, have a higher heating capacity than boilers for local boiler houses. These boiler rooms are usually located in specially constructed separate buildings.
District heating boiler houses are used to supply heat to large residential areas: they are equipped with relatively powerful hot water or steam boilers.
boiler plant with steam boilers. The installation consists of a steam boiler, which has two drums - upper and lower. The drums are connected to each other by three bundles of pipes that form the heating surface of the boiler. When the boiler is operating, the lower drum is filled with water, the upper drum is filled with water in the lower part, and saturated water vapor in the upper part. At the bottom of the boiler there is a firebox with a mechanical grate for burning solid fuel. When burning liquid or gaseous fuel, instead of a grate, nozzles or burners are installed, through which the fuel together with air is supplied to the firebox. The boiler is limited by brick walls - lining.
Boiler installations located in specially designated areas where outsiders have no access. And heating mains and heat pipelines connect boiler houses and consumers.
Classification of boiler houses.
Modern boiler systems have different classifications. Each of them is based on a certain principle or certain values. Today there are several main distinctions:
Location.
Depending on where the installation is located, the following are distinguished:
Roof;
Built into the building;
Block-modular;
Frame.
Steam boilers
Hot water;
Mixed;
Boilers using diathermic oil.
Solid fuel. For this, firewood, coal and other types of solid fuel are used.
Liquid fuels - oil, gasoline, fuel oil and others.
Gas.
Mixed or combined. It is assumed that various types and types of fuel will be used.
Boilers as technical devices for the production of steam or hot water are distinguished by a variety of design forms, principles of operation, types of fuel used and production indicators. At the same time, according to the method of organizing the movement of water and steam-water mixture, all boilers can be divided into the following two groups:
Boilers with natural circulation;
Boilers with forced movement of coolant (water, steam-water mixture).
In modern heating and heating-industrial boiler houses, boilers with natural circulation are mainly used to produce steam, and boilers with forced movement of coolant operating on the direct-flow principle are used to produce hot water.
Modern steam boilers with natural circulation are made of vertical pipes located between two collectors (drums). One part of the pipes, called heated "rising pipes", is heated by the torch and combustion products, and the other, usually unheated part of the pipes, is located outside the boiler unit and is called "fall pipes". In heated lifting pipes, water is heated to a boil, partially evaporates and enters the boiler drum in the form of a steam-water mixture, where it is separated into steam and water. Through lowering unheated pipes, water from the upper drum enters the lower collector (drum).
The movement of the coolant in boilers with natural circulation is carried out due to the driving pressure created by the difference in the weights of the water column in the lowering pipes and the column of steam-water mixture in the rising pipes.
In steam boilers with multiple forced circulation, the heating surfaces are made in the form of coils that form circulation circuits. The movement of water and steam-water mixture in such circuits is carried out using a circulation pump.
In direct-flow steam boilers, the circulation ratio is unity, i.e. The feed water, when heated, successively turns into a steam-water mixture, saturated and superheated steam. In hot water boilers, water moving along the circulation circuit is heated in one revolution from the initial to the final temperature.
Based on the type of coolant, boilers are divided into hot water and steam boilers. The main indicators of a hot water boiler are thermal power, i.e. heating capacity and water temperature; The main indicators of a steam boiler are steam output, pressure and temperature.
Hot water boilers, the purpose of which is to obtain hot water of specified parameters, are used to supply heat to heating and ventilation systems, household and technological consumers. Hot water boilers, usually operating on the direct-flow principle with a constant flow of water, are installed not only at thermal power plants, but also in district heating, as well as heating and industrial boiler houses as the main source of heat supply.
Steam boiler is an installation designed to generate saturated or superheated steam, as well as to heat water (heating boiler).
Based on the relative movement of heat-exchanging media (flue gases, water and steam), steam boilers (steam generators) can be divided into two groups: water-tube boilers and fire-tube boilers. In water-tube steam generators, water and a steam-water mixture move inside the pipes, and flue gases wash the outside of the pipes. In Russia in the 20th century, Shukhov water-tube boilers were mainly used. In fire tubes, on the contrary, flue gases move inside the pipes, and water washes the pipes outside.
Based on the principle of movement of water and steam-water mixture, steam generators are divided into units with natural circulation and with forced circulation. The latter are divided into direct-flow and multiple-forced circulation.
As a rule, a three-plunger high-pressure pump of the P21/23-130D or P30/43-130D series is used as a feed pump.
Boilers above critical pressure (SCP) - steam pressure above 22.4 MPa.
Main elements of steam and hot water boilers
Furnaces for burning gaseous, liquid and solid fuels. When burning gas and fuel oil, as well as solid pulverized coal fuels, chamber furnaces are usually used. The firebox is limited by the front, rear, side walls, as well as the bottom and arch. Along the walls of the furnace there are evaporative heating surfaces (boiling pipes) with a diameter of 50...80 mm, which receive radiated heat from the torch and combustion products. When burning gaseous or liquid fuels, there is usually no screening under the chamber furnace, and in the case of coal dust, a “cold” funnel is made in the lower part of the combustion chamber to remove ash falling from the burning torch.
The upper ends of the pipes are rolled into the drum, and the lower ends are connected to the collectors by rolling or welding. For a number of boilers, the boiling pipes of the rear screen, before connecting them to the drum, are placed in the upper part of the firebox in several rows, staggered and forming a festoon.
To service the furnace and gas ducts in the boiler unit, the following equipment is used: manholes, lockable doors, peepholes, explosion valves, gate valves, rotary dampers, blowers, shot blasters.
Closable doors and openings in the lining are intended for inspection and repair work when the boiler is shut down. Peepers are used to monitor the process of fuel combustion in the firebox and the state of convective flues. Explosion safety valves are used to protect the lining from destruction during popping in the furnace and boiler flues and are installed in the upper parts of the furnace, the last flue of the unit, the economizer and in the vault.
Cast iron smoke dampers or rotary dampers are used to regulate draft and shut off the hog.
When working on gaseous fuel, in order to prevent the accumulation of flammable gases in the furnaces, chimneys and hogs of the boiler installation during a break in work, a small draft must always be maintained in them; To do this, each individual boiler hog must have its own gate with a hole in the upper part with a diameter of at least 50 mm for the prefabricated hog.
Blowers and shot blasters are designed to clean heating surfaces from ash and soot.
Steam boiler drums. It should be noted the multi-purpose purpose of steam boiler drums, in particular, the following processes are carried out in them:
Separation of the steam-water mixture coming from heated lifting pipes into steam and water and collection of steam;
Reception of feed water from a water economizer or directly from the feed line;
In-boiler water treatment (thermal and chemical water softening);
Continuous blowing;
Drying steam from boiler water droplets;
Washing steam from salts dissolved in it;
Protection against excess steam pressure.
Boiler drums are made of boiler steel with stamped bottoms and manholes. The internal part of the drum volume, filled to a certain level with water, is called the water volume, and the part filled with steam during boiler operation is called the steam volume. The surface of boiling water in the drum, separating the water volume from the steam volume, is called the evaporation mirror. In a steam boiler, only that part of the drum that is cooled by water on the inside is washed with hot gases. The line separating the surface heated by gases from the unheated one is called the fire line.
The steam-water mixture flows through rising boiling pipes rolled into the bottom of the drum. From the drum, water is supplied through lower pipes to the lower collectors.
Emissions, ridges and even fountains appear on the surface of the evaporation surface, and a significant number of droplets of boiler water can enter the steam, which reduces the quality of the steam as a result of an increase in its salt content. Drops of boiler water evaporate, and the salts contained in them are deposited on the inner surface of the superheater, worsening heat transfer, as a result of which the temperature of its walls increases, which can lead to their burnout. Salts can also be deposited in steam line fittings and lead to a loss of tightness.
To ensure uniform flow of steam into the steam space of the drum and reduce its humidity, various separation devices are used.
To reduce the possibility of scale deposits on evaporative heating surfaces, intra-boiler water treatment is used: phosphating, alkalization, and the use of complexones.
Phosphating is intended to create conditions in boiler water under which scale formers are released in the form of non-stick sludge. To achieve this, it is necessary to maintain a certain alkalinity of the boiler water.
Unlike phosphating, water treatment with complexones can provide scale-free and sludge-free boiler water conditions. It is recommended to use Trilon B sodium salt as a complexone.
Maintaining the acceptable salt content in boiler water by standards is carried out by purging the boiler, i.e. by removing from it some part of the boiler water, which always has a higher concentration of salts than the feed water.
To carry out stepwise evaporation of water, the boiler drum is divided by a partition into several compartments that have independent circulation circuits. One of the compartments, called the “clean” compartment, receives feed water. Passing through the circulation circuit, the water evaporates, and the salt content of the boiler water in the clean compartment rises to a certain level. To maintain the salt content in this compartment, part of the boiler water from the clean compartment is directed by gravity through a special hole - a diffuser in the lower part of the partition into another compartment, called “salt”, since the salt content in it is significantly higher than in the clean compartment.
Continuous blowing of water is carried out from the place with the highest concentration of salts, i.e. from the salt compartment. The steam generated in both evaporation stages is mixed in the steam space and exits the drum through a series of pipes located in its upper part.
With increasing pressure, steam is able to dissolve some impurities in boiler water (silicic acid, metal oxides).
To reduce the salt content of steam, some boilers use steam flushing with feed water.
Boiler superheaters. The production of superheated steam from dry saturated steam is carried out in a superheater. The superheater is one of the most critical elements of the boiler unit, since of all heating surfaces it operates under the most severe temperature conditions (overheating temperature up to 425 °C). Superheater coils and collectors are made of carbon steel.
Based on the method of heat absorption, superheaters are divided into convective, radiation-convective and radiation. Low and medium pressure boiler units use convective superheaters with vertical or horizontal pipes. To produce steam with a superheat temperature of more than 500 °C, combined steam superheaters are used, i.e. in them, one part of the surface (radiative) perceives heat due to radiation, and the other part - by convection. The radiation part of the heating surface of the superheater is located in the form of screens directly in the upper part of the combustion chamber.
Depending on the directions of movement of gases and steam, there are three main schemes for connecting the superheater to the gas flow: direct flow, in which gases and steam move in the same direction; countercurrent, where gases and steam move in opposite directions; mixed, in which in one part of the superheater coils gases and steam move straight through, and in the other - in opposite directions.
Optimal in terms of operational reliability is a mixed superheater switching scheme, in which the first part of the superheater along the steam flow is countercurrent, and the completion of steam superheating occurs in its second part with direct flow of coolants. In this case, in some of the coils located in the area of the highest thermal load of the superheater, at the beginning of the gas duct there will be a moderate steam temperature, and the completion of steam superheating occurs at a lower thermal load.
The steam temperature in boilers with pressures up to 2.4 MPa is not regulated. At a pressure of 3.9 MPa and above, the temperature is regulated by the following methods: injection of condensate into steam; using surface desuperheaters; using gas regulation by changing the flow of combustion products through the superheater or moving the position of the torch in the furnace using rotary burners.
The superheater must have a pressure gauge, a safety valve, a shut-off valve to disconnect the superheater from the steam main, and a device for measuring the temperature of superheated steam.
Water economizers. In an economizer, feedwater is heated by flue gases before being supplied to the boiler by using the heat of fuel combustion products. Along with preheating, partial evaporation of the feed water entering the boiler drum is possible. Depending on the temperature to which the water is heated, economizers are divided into two types - non-boiling and boiling. In non-boiling economizers, according to the conditions for the reliability of their operation, water is heated to a temperature 20 ° C below the temperature of saturated steam in a steam boiler or the boiling temperature of water at the existing operating pressure in a hot-water boiler. In boiling economizers, not only the water is heated, but also its partial (up to 15% %) evaporation.
Depending on the metal from which economizers are made, they are divided into cast iron and steel. Cast iron economizers are used at a pressure in the boiler drum of no more than 2.4 MPa, while steel ones can be used at any pressure. In cast iron economizers, water boiling is unacceptable, as this leads to water hammer and destruction of the economizer. To clean the heating surface, water economizers have blowing devices.
Air heaters. In modern boiler units, the air heater plays a very significant role, receiving heat from the exhaust gases and transferring it to the air, it reduces the most noticeable item of heat loss with the exhaust gases. When using heated air, the combustion temperature of the fuel increases, the combustion process intensifies, and the efficiency of the boiler unit increases. At the same time, when installing an air heater, the aerodynamic resistance of the air and smoke paths increases, which is overcome by creating artificial draft, i.e. by installing a smoke exhauster and a fan.
The air heating temperature is selected depending on the combustion method and type of fuel. For natural gas and fuel oil burned in chamber furnaces, the hot air temperature is 200...250 °C, and for pulverized coal combustion of solid fuel - 300...420 °C.
If there is an economizer and an air heater in the boiler unit, the economizer is installed first along the gas flow, and the air heater is installed second, which allows the combustion products to be cooled more deeply, since the temperature of the cold air is lower than the temperature of the feed water at the inlet to the economizer.
Based on their operating principle, air heaters are divided into recuperative and regenerative. In a recuperative air heater, heat transfer from combustion products to air occurs continuously through a dividing wall, on one side of which combustion products move, and on the other - heated air.
In regenerative air heaters, heat is transferred from combustion products to heated air by alternately heating and cooling the same heating surface.
Gas piston installations. The gas piston unit (GPU) is designed to supply electricity to consumers of three-phase (380/220 V, 50 Hz) alternating current. Gas power plants are used as a source of constant and guaranteed power supply to hospitals, banks, shopping malls, airports, manufacturing and oil and gas production enterprises. The engine life of a gas engine is higher than that of gasoline generators and diesel power plants, which leads to a shorter payback period. The use of gas electric generators allows the owner to be independent from planned and emergency power outages, and often completely refuse the services of electricity suppliers.
The operation of gas piston engines (hereinafter referred to as GPA) is based on the operating principle of an internal combustion engine. An internal combustion engine is a type of engine, a heat engine, in which the chemical energy of fuel (usually liquid or gaseous hydrocarbon fuel) burning in the working area is converted into mechanical work.
At the moment, two types of piston engines running on gas are produced in industry: gas engines - with electric (spark) ignition, and gas diesel engines - with ignition of the gas-air mixture by injection of pilot (liquid) fuel. Gas engines have become widely used in the energy sector due to the widespread trend of using gas as a cheaper fuel (both natural and alternative) and relatively more environmentally friendly in terms of exhaust emissions.
From the GPU with heat exchangers, everything is basically the same, but a heat recovery system is additionally used.
The unit operates on several types of fuel, has a relatively low initial investment per 1 kW and has a wide range of power outputs.
Fuel for gas piston units. One of the most important points when choosing the type of gas turbine is to study the composition of the fuel. Manufacturers of gas engines have their own requirements for the quality and composition of fuel for each model.
Currently, many manufacturers are adapting their engines for the appropriate fuel, which in most cases does not take much time and does not require large financial costs.
In addition to natural gas, gas piston units can use as fuel: propane, butane, associated petroleum gas, chemical industry gases, coke oven gas, wood gas, pyrolysis gas, landfill gas, waste water gas, etc.
The use of these specific gases as fuel makes an important contribution to preserving the environment and also allows the use of regenerative energy sources.
Gas control point. Gas control point is a system of devices for automatically reducing and maintaining constant gas pressure in gas distribution pipelines. The gas control point includes a pressure regulator to maintain gas pressure, a filter to capture mechanical impurities, safety valves that prevent gas from entering gas distribution pipelines in the event of an emergency gas pressure in excess of permissible parameters, and instrumentation for recording the amount of gas passing, temperature, pressure and telemetric measurements these parameters.
Gas control points are constructed on city gas distribution pipelines, as well as on the territory of industrial and municipal enterprises with an extensive network of gas pipelines. Points installed directly at consumers and designed to supply gas to boilers, furnaces and other units are usually called gas control devices. Depending on the gas pressure at the inlet, gas control points are: medium (from 0.05 to 3 kgf/cm 2 ) and high (up to 12 kgf/cm 2 ) pressure (1 kgf/cm 2 =0.1Mn/m2).
Safety devices and instrumentation. For hot water boilers, bypass lines with check valves (Fig.), which pass water in the direction from the boiler to the heating system pipeline, can serve as a protective device against increasing pressure in them. With such a simple device, if the valves installed at the boiler are closed for some reason, then the connection with the atmosphere through the expansion vessel will not be disrupted.
If the pipeline between the boilers and the expansion vessel, in addition to the specified valves, has any other shut-off valves, then lever safety valves must be installed.
Steam boilers up to 70 kPa are equipped with a safety device in the form of a hydraulic shutter
For safe and proper operation, steam boilers, in addition to safety devices, are equipped with water indicating devices, plug valves and pressure gauges.
To measure the flow of feed water supplied to a steam boiler or water circulating in a water heating system, a water meter or diaphragms are installed. To measure the temperature of the water entering the water heating system and returning to the boiler, thermometers are provided in special cases.
Boiler installations, depending on the type of consumer, are divided into energy, production and heating and heating. Based on the type of coolant produced, they are divided into steam (for generating steam) and hot water (for producing hot water).
Energy boiler plants generate steam for steam turbines in thermal power plants. Such boiler houses are usually equipped with high- and medium-power boiler units that produce steam with increased parameters.
Industrial heating boiler installations(usually steam) produce steam not only for industrial needs, but also for heating, ventilation and hot water supply.
Heating boiler systems(mainly hot water, but they can also be steam) are designed to service heating systems, hot water supply and ventilation of industrial and residential premises.
Depending on the scale of heat supply, heating boiler houses are divided into local (individual), group and district.
Local heating boiler houses usually equipped with hot water boilers with water heating to a temperature of no more than or steam boilers with a working pressure of up to. Such boiler houses are designed to supply heat to one or more buildings.
Group heating boiler houses provide warmth to groups of buildings, residential areas or small neighborhoods. Such boiler houses are equipped with both steam and hot water boilers, which, as a rule, have a higher heating capacity than boilers for local boiler houses. These boiler rooms are usually located in special buildings.
District heating boiler houses designed for heat supply to large residential areas; they are equipped with relatively powerful hot water and steam boilers.
Rice. 1.1
In Fig. 1.1. a diagram of a district heating boiler house with hot water boilers is shown 1 type PTVM-50 with a heating capacity of 58 MW. Boilers can operate on liquid and gaseous fuel, so they are equipped with burners and nozzles 3 . The air required for combustion is supplied to the furnace by blower fans 4 driven by electric motors. Each boiler has 12 burners and the same number of fans.
Water is supplied to the boiler by pumps 5 driven by electric motors. Having passed through the heating surface, the water is heated and supplied to consumers, where it gives off some of the heat and returns to the boiler at a lower temperature. Flue gases from the boiler are removed to the atmosphere through a pipe 2.
This boiler room has a semi-open type layout: the lower part of the boilers (up to approximately a height of 6 m) is located in the building, and their upper part is in the open air. Inside the boiler room there are blower fans, pumps, and a control panel. A deaerator is installed on the ceiling of the boiler room 6 to remove oxygen from water.
In boiler systems with steam boilers(Fig. 1.2) steam boiler 4 has two drums - upper and lower. The drums are connected to each other by three bundles of pipes that form the heating surface of the boiler. When the boiler is operating, the lower drum is filled with water, the upper drum is filled with water in the lower part, and saturated water vapor in the upper part. At the bottom of the boiler there is a firebox 2 with a mechanical grate for burning solid fuel. When burning liquid and gaseous fuels, instead of a grate, nozzles or burners are installed, through which the fuel together with air is supplied to the firebox. The boiler is limited by brick walls - lining.
The work process in the boiler room proceeds as follows. Fuel from the fuel storage is supplied by a conveyor to the bunker, from where it goes to the firebox grate, where it burns. As a result of fuel combustion, flue gases are formed - combustion products burn.
Flue gases from the furnace enter the boiler flues, formed by lining and special partitions installed in the pipe bundles. As they move, the gases wash the tube bundles of the superheater boiler 3, pass through the economizer 5 and the air heater, where they are cooled due to the supply of heat to the water entering the boiler and the air supplied to the furnace.
The cooled flue gases are removed through the chimney 7 into the atmosphere using a smoke exhauster 8. Flue gases from the boiler can be removed without a smoke exhauster under the influence of natural draft with a built-in chimney.
Water from the water supply source to the supply pipeline is pumped 1 into the water economizer, from where, after heating, it enters the upper drum of the boiler. The filling of the boiler drum with water is controlled by a water indicator glass installed on the drum.
Rice. 1.2
From the upper drum of the boiler, water descends through pipes into the lower drum, from where it rises again through the left bundle of pipes into the upper drum. In this case, the water evaporates, and the resulting steam is collected in the upper part of the upper drum. Then the steam enters superheater 3, where it is completely dried by the heat of the flue gases, as a result of which its temperature rises.
From the superheater, steam enters the main steam line and from there to the consumer, and after use it is condensed and returned to the boiler room in the form of hot water (condensate). Condensate losses from the consumer are replenished with water from the water supply or other water supply sources. Before entering the boiler, water is subjected to appropriate treatment.
The air required for fuel combustion is taken, as a rule, from the top of the boiler room and supplied by fan 9 to the air heater, where it is heated and then sent to the firebox. In boiler houses of small capacity, there are usually no air heaters, and cold air is supplied to the firebox either by a fan or due to the vacuum in the firebox created by the chimney.
A boiler plant with steam boilers has a closed type layout, when all the main equipment of the boiler room is located in the building.
Boiler installations are equipped with water treatment devices (not shown in the diagram), control and measuring instruments and appropriate automation equipment, which ensures their uninterrupted and reliable operation.
Hot water boiler houses installations are designed to produce hot water used for heating, hot water supply and other purposes.
Rice. 1.1 Boiler room with cast iron hot water boilers 1-hopper for collecting ash and slag; 2-scraper; 3-scraper drive winch; 4-ash collectors of cyclone type; 5-smoke exhauster; 6-brick chimney; 7-boiler; 8-blow fan; 9-installation of chemical water purification (filter); 10-scraper channel for removing slag and ash
A hot water boiler house has one coolant - water, in contrast to a steam boiler house, which has two coolants - water and steam. In this regard, the steam boiler room must have separate pipelines for steam and water, as well as a tank for collecting condensate.
Hot water and steam boiler houses differ depending on the type of fuel used, the design of boilers, furnaces, etc. Both a steam and water heating boiler installation usually includes several boiler units, but no less than two and no more than four or five. All of them are connected by common communications - pipelines, gas pipelines, etc.
Plants operating on nuclear fuel, the feedstock of which is uranium ore, are becoming increasingly widespread.
