How a steam boiler works
Steam boilers are equipment that can be used both at industrial facilities and for domestic purposes. The main function of such devices is to convert water into steam, which can then be used to heat rooms or provide movement of various mechanisms.
Steam boilers are actively used in the following industries:
Finally A Flash Steam Boiler That Works!!
- Heating systems. There are industrial and household models of steam boilers that can use steam as a heat transfer medium. Steam passes through heating circuits and/or enters the heat exchangers of hot water devices, thereby moving heat energy. Household steam heating boiler is often combined with solid fuel heating devices. Industrial facilities use more powerful and reliable devices that produce superheated steam, which has a higher heat output.
- Energy. Steam machines convert superheated steam into electrical energy. The working process looks quite simple: steam moves into the turbine and rotates the shaft, due to which electricity is generated. This principle has been used successfully in many power plants.
- Industry. Steam devices are quite capable of providing mechanical motion to various elements of systems. The principle of operation of the industrial steam boiler looks the same as in the previous case, but the energy generated is aimed at performing mechanical effects on the elements that need to move.
Knowing what a steam boiler is needed for and where it is used allows the device to be used with the utmost efficiency.
Technological applications of steam boiler systems
There are several industries that use steam boilers all the time:
- The first industry is heat production. Steam heats large workshops, for example, in the automotive industry. Steam is used to heat water to the desired temperature, which is then pumped through heating mains to apartment buildings and other facilities.
- Second branch is energy. Here steam is used to turn a turbine that generates electric current.
- The third industry is the production of building materials. For example, steam is used to dry concrete products.
In many industries, steam boilers are an essential part of technology. Disinfection and drying of foodstuffs, cooking, preservation, etc.
Gas wastes recovery also includes steam plants. In this process they act as coolers. Such a boiler takes heat energy from gases, e.g. from high-temperature furnaces.
Steam boiler manifolds
All pipes of the evaporation and blowdown part of the boiler are fastened with their ends in the collectors (steam and water) by the rolling method. Sometimes, in the case of highly stressed boilers, pipes can be connected by welding, or a combination of both (rolling and welding).
Collectors of steam boilers are welded cylindrical steel thick-walled structures. Bottoms of large diameter (steam) collectors have elliptical shape. The shells of collectors have a thickened structure at the point of pipe fastening and are called a pipe board. All collectors, in order to provide inspection and repair work, have in the bottoms with manhole holes with manhole gates. Various partitions, baffles and other intra-collector devices are installed inside collectors.
Intra-collector devices of the steam collector (depending on the boiler design) may include the following devices:
- All kinds of separation devices: perforated shields, louvered separators, inside-collector cyclones, etc., ensuring steam separation. separation of steam from water in steam-water mixture and decrease of steam humidity
- feed tube, providing uniform distribution of feed water over the collector and supplying it to the downpipes;
- steam extraction devices: steam collection pipes or steam baffles, which ensure extraction of saturated separated steam from the steam collector and its supply to the steam superheater;
- funnels and pipes of boiler water sampling system;
- Funnels and pipes of the upper boiler blowdown system;
- Steam cooler pipe system.
Intra-collector devices of water and steam superheater headers are mainly designed for uniform distribution of media along their length and organization of flow of these media. Intra-collector devices of water collectors and superheater collectors include various types of shields, baffles, bypass pipes, pipelines of blowing systems.
Purpose and classification of shipboard steam boilers
Steam boiler is a heat exchange apparatus designed to convert water into steam of specified parameters at the expense of thermal energy released during combustion of fossil fuels.
The principle of operation of the steam boiler is determined by the essence of the working processes that take place in it. Working processes in steam boilers run in the air-gas path, in the steam-water path, and are closely interconnected with each other.
How to Diagnose Leaks in a Steam Boiler | Ask This Old House
There are two main sources of heat generation in a steam boiler:
- 1.Direct combustion of organic fuel in the boiler furnace (main method). This generates a large volume of hot combustion products (flue gases), which are a heat transfer medium that transfers heat to heated and evaporated water and superheated steam;
- 2.Using the exhaust heat of other types of heat engines: diesel engine or gas turbine.
Ship steam boilers can be classified according to the following features:
- for the main. which supply steam to main engine (steam turbine) and all steam consumers during ship (vessel) running;
- auxiliary. steaming all consumers of the ship at anchorage when the main boilers are not in operation as well as those used to put the main boilers into operation. On ships with GTUs and DAEWOO, auxiliary boilers also operate on sea modes to provide steam to all consumers on the ship;
- on autonomous. having their own fuel and air supply system, and using the heat of the combustion products generated during combustion of organic fuel in the furnace for steam generation
- waste heat recovery. Using heat from exhaust gases of DAEWOO or GTU;
- combined. which heat water and its evaporation can be carried out from both own fuel and air systems, and from the heat of combustion products of other types of fuel plants;
- water tube. in which water and steam-water mixture move inside pipes, washed from outside by hot gases;
- fire tubes. where hot gases move inside pipes, washed with water from outside
- combined. having in their composition water-tube and fire-tube parts;
according to the principle of organization of water and steam-water mixture movement:
- boilers with natural circulation (NTC). in which the movement of water and steam-water mixture along the circulation circuit is due to the difference in density of feed water and steam-water mixture formed by evaporation of water;
- boilers with forced circulation (PC). in which the movement of water and steam-water mixture in the circulation circuit is due to the operation of a special circulation pump.
In turn, steam boilers with PC according to the circulation ratio are divided into boilers:
according to the way the air movement is organized:
- boilers with fan blowing (open and closed), in the furnace of which the fuel burns at a pressure slightly higher than the atmospheric pressure, and the air is supplied to the furnace by the boiler fan;
- Boilers with compressor boost (high-pressure boilers), in which furnace the fuel burns at a pressure much higher than the atmospheric pressure: 0.2 ÷ 0.4 MPa (2 ÷ 4 kgf/cm2 ), and the air is blown into the furnace by a special compressor unit;
- boilers operating on solid fuel (coal and coal dust)
- boilers operating on liquid fuel (fuel oil, diesel fuel);
- boilers operating on gaseous fuel (natural and synthetic gases);
For operation of ship and ship steam boilers, the following liquid fuels are usually used: fuel oil or (much more seldom) diesel fuel. In exceptional cases, gas-fired steam boilers operating on gas transported by the ship can be used on gas carriers with PTU.
- single-front boilers, in which the firing devices are located at one, front (from the service side) of the boiler;
- With double-front heating, in which the furnace devices are located at the front and rear fronts of the boiler;
- with ceiling arrangement of furnace devices;
- with side location of the furnace devices;
Ship steam boilers can also be classified by other features which characterize their design features:
- by type of applied heating surfaces: evaporative tube bundles, economizer, air heater and steam superheater;
- on the presence or absence of tail heating surfaces (economizers and air heaters);
- by the mutual placement of the heating surfaces;
- by the number of collectors;
- system, by the organization of the combustion process, and others, by the number of collectors; 7.
A BHPP usually includes more than one boiler unit. One or more boilers ensuring production of steam of required parameters, together with systems, auxiliary mechanisms and appliances serving them, are referred to as a shipboard boiler plant.
.3. Vortex furnace of CKTI system A. А. Shershneva
For combustion of milled fuel without its preliminary milling, as well as sawdust, the pneumatic vortex furnace of the CKTI system A is widely used. А. Schershnev, its furnace chamber 1 (Fig. 2.7) has a special configuration. Main air flow required for combustion, with velocity 25. 30 m/s flows through nozzles 3 to the bottom of the cold funnel along its front slope. The fuel by the drum feeder 2 is fed through a slot to the front slope of the cold hopper, along which it moves towards the airflow. Being washed by air flow the fuel particles are as though sorted according to their sizes: small particles are immediately caught by the air and during ignition burn in the upper part of the combustion chamber being in suspended state. The dried lighter fuel particles are ejected into the middle part of the combustion chamber and there also burn in a suspended state. Wet, heavy fuel particles will return by gravity to the funnel mouth and will be caught up by the air current again. In the process of repeated circulation up and down these particles are dried up and crushed. These particles are circulated until the air current carries them to the middle part of the combustion chamber where they are burned.
Part of the biggest fuel fractions falls on the grate under the funnel, on the afterburning grate 6, where they finish combustion in the bed of the furnace. Air for combustion of this part of fuel is supplied through the channels of air duct 5 under the grate of grate 6. At normal operation of the furnace 80% of air is supplied through the nozzles, and 20%. under the grate.
1. furnace chamber; 2. drum feeder; 3. air nozzle; 4. air duct; 5. air duct (air supply to the afterburning grate); 6. afterburning grate
The design of steam boilers
Depending on the purpose, operating conditions and requirements for steam parameters, the steam boiler design may vary. Structurally, steam boilers are distinguished by:
- The method of separation of steam. direct flow (flow-through) and circulation;
- By the device of steam separator. drum and other (bell-type, coil, etc.);
- The method of heat transfer. gas-tube (formerly known as firetube; old firetube) and water-tube;
- By orientation and configuration of steam generator channels. horizontal, vertical, combined (flue gas inlet horizontal, outlet vertical; channels curved), inclined, multi-collector, serpentine, jacketed vortex combustion, etc;
- By the way of combustion gases. direct and circulating;
- By hydrodynamics. with open or closed steam-water circuit, see Fig.6.1. further;
- By method of heating. flame (fuel), electric, indirect heating, solar boilers, etc.
As for the heating method, electric steam boilers allow obtaining only low and low-potential steam. a TEN cannot withstand the harsher conditions of a boiler. Indirect heating boilers are mostly used. at nuclear power plants. When they write that the temperature of the coolant in them reaches 500 degrees or higher, this refers to the first circuit, which by means of a heat exchanger heats the usual high-potential boiler, which gives steam to the turbine. Solar boilers (solar boilers) t.п. exotics is a subject of a separate consideration. We will touch on them in passing at the end, and will deal mainly with flame steam boilers. the unit of steam efficiency from them is the cheapest and most accessible.
Note: submarine sailors sometimes play a trick on land “teapots” with tales of how they allegedly washed off watch and slept on the primary reactor circuit of a nuclear submarine. This is a pure joke. on the first circuit, not only is the temperature above 400 degrees, but the radiation is fatal, and unauthorized leaving the watch is a serious crime. The first circuit of nuclear reactors is designed so that there is no steam release from the coolant in it.
Straight flow or circulation
In direct-flow steam boilers (pos. A in fig.) Wet steam enters the coil, tube header, or under the hood, where it precipitates a water slurry that flows by gravity into the steam generator.
Circuit diagrams of direct flow and circulation steam boilers
Straight-flow boilers are structurally simpler, and from automatics they need only an experienced boiler man. Straight-flow boilers can be energy-independent. they can do without feed pump, receiving water by gravity from a feed tank. But they are much more explosive than circulating boilers, and their thermal efficiency and steam capacity are low. Steam is emitted most intensely from the uppermost layers of water in the boiler. Free from the micro-bubbles of steam, the water sinks downwards and rises up again as it becomes saturated with steam. In the direct-flow boiler the water renewal takes place by gravitational convection (the water produced by the steam is heavier), which consumes fuel. You need a lot of it, t.к. The convective flows are disorderly, with whirlpools and dissipate the received energy more than carry water upwards. Thermal efficiency of the direct-flow boiler is approx. 35-40% Having multiplied this value by the efficiency of steam engine 25-30% (at modern ones up to 45%), just get the notorious “steam engine” efficiency of 8-16%
In a circulating boiler, the total water flow is directed upward by a separate circulation pump, pumping condensate out of the superheater; internal friction losses in the water are minimal and circulation pump power is required to be small. The elementary volume of water, before it evaporates completely, goes through 5 to 30 revolutions and more, which further increases the thermal efficiency and steam capacity of the boiler. Let’s assume that for one revolution of the water portion evaporates only 10% of it. For the next revolution, 90% will remain, of which 10% will evaporate, i.e.е. another 9% of the original volume and water will remain 81% Calculating in a similar way further (mathematicians such calculations are called recurrence relationships), we obtain for 5 turns the boiler efficiency of 63%, and for 30 turns. 92.6%. The effective area of the condensate separator in this case increases against the geometric area of the condensate separator. by a factor of 1.5 and 2.
A circulation boiler must be equipped not only with pumps, but also with a condensate level regulator in the steam separator. If there is too much of it, the boiler’s technical parameters will sharply deteriorate. If there is too little, it can cause trouble: wet steam condenses quickly, the pressure in the boiler drops sharply too. boiling. explosion. Drum type boilers allow to avoid such a situation. A steam separator is a segment of a wide pipe (drum) into which saturated steam flows from the boiler (heater), which in this case is not a steam generator; in this way water heating and steam extraction from it are separated. The heater can not boil in principle, and boiling of the drum is not so dangerous.к. most of the energy released is spent squeezing the water back into the heater and the supply tank.
The principle of operation of the drum steam boiler automation
Wet steam from the steam separator enters the small volume “free” condenser, also round in cross-section. The feed pipe is elevated above the bottom of the condenser, ensuring a constant condensate level in the condenser. For the correct operation of the drum boiler, the pressure of the water columns in the drum and the condenser must be balanced. To ensure the latter condition the condenser is not placed directly on the drum but is elevated above it. As a result, the drum boiler mode is clearly maintained by the energy-independent automatics (see Fig. Fig. above): a lot of water in the drum, outlet pressure is higher than normal. the differential steam regulator cuts off the power supply; on the contrary. it turns it on. The standard water level in the drum is maintained within the permissible limits. The drum steam boiler can also operate with natural circulation, see video below. video below:
Operating principles and design of steam boilers
Steam plant operation is based on the principle of changing the physical state of water from liquid to steam at high temperature heating and further transformation of steam into a state with required parameters. This principle is put into practice by supplying the boiler circuit with the required amount of water and ensuring a suitable evaporating surface.
In order to monitor the operation of the unit, the steam boiler is equipped with a large number of monitoring sensors. The entire steam production cycle is constantly monitored. The technology of steam preparation in the unit is as follows: prior to operation, the pump fills the pipes with prepared and treated water to the required level. After that the water supply is cut off. Then the heating process starts, during which the water evaporates. The steam thus created leaves the heating circuit. As the water evaporates, it falls to the minimum. Sensors detect the drop in water level and activate the pumping equipment which presses the water up to the operating level. After that the heating process is repeated again. So it is not difficult to imagine that the steam generator works in cyclic mode.
Besides controlling the operating level of the liquid in the tank, the electronics also controls the alarm levels. maximum and minimum. When the liquid reaches these levels, the protection automatics interlocks the fuel supply and makes an emergency steam dump. The automatics thereby isolates the steam boiler from the main line and protects the downstream system from severe water hammer.
Considering that the steam boiler is the equipment of increased danger, it is equipped with both electronic protection automatics and mechanical devices. This includes breakdown valves, pressure relief valves, shut-off devices and spigot valves. The task of this safety equipment in the event of an emergency situation, if electronic protection does not work, to stop and shut down the installation and avoid accidents.
A great advantage of the steam installation is that when using it as a heating device it is not necessary to additionally install circulation pumps to inject steam into the main pipeline. Here, pressurized steam constantly pushes the coolant volume with its own pressure. And make-up is carried out by means of pump water intake from condensate collector. In closed systems, where the heat transfer medium circulates continuously, no additional water treatment is required to remove the condensate before it is sent to the boiler.
And in open systems, when the heating medium flows after passing through the heating circuit to the open cooler, it is necessary to constantly replenish the water from an external source. In this case it is carried out pre-treatment. softening, cleaning from foreign impurities, removal of oxygen from it. In some cases to prevent corrosion formation special anticorrosive additives and neutralizers are added to water, it is required by technological standards of production.
Steam boilers K-50-40-1 K-50-40/14
These steam boilers are designed to burn pulverized lignite and hard coal, and milling fuel. Boilers K-50-40/14 produce saturated steam with pressure of 1,4 MPa or overheated steam
1. convective surface; 2. additional drum; 3. steel water economizer; 4. tubular air heater; 5. cast-iron water economizer; 6. festoon; 7. steam superheater; 8. main drum
steam of the same pressure with a temperature of 250 ° C, and boilers K-50-40-1. superheated steam pressure of 3.92 MPa and a temperature of 440 ° C.
Steam boiler K-50-40/14 (fig. 3.9) Has vertical orientation and U-shaped arrangement of heating surfaces. The boiler cladding is framed. Furnace chamber is fully shielded. Depending on the type of fuel combusted, boilers can be equipped with various dust collection devices. The burners are located on the front wall of the furnace. Pipes of the rear screen in the upper part of the furnace are bifurcated and form a four-row festoon A small superheater 7 is located immediately behind the festoon. Convective heating surface is located in the rotary chamber, which is made of inclined tubes, connected to the additional drum, which is an independent circulation circuit.
Main drum joins eight independent circulation circuits. Each screen, located on the side wall of the furnace, consists of three circuits (two side screens have six circuits in total), rear and front screens are derived in independent circuits.
Two-stage tube air heater and water economizer are located in the boiler exhaust shaft. Feed water enters the first stage of the cast-iron water economizer 5, then the second stage of the steel water economizer from where it is sent to the upstream additional drum The latter separates the steam-water mixture coming from the convective heat transfer area into steam and water. Steam is then sent to the steam space of the main drum and water to the lower collector of the convective heating surface and to the water space of the main drum.
The cold air is supplied by the fan to the three-pass first stage air heater and from there it is sent to the single-pass second stage air heater through the air duct.
3.8, Steam boiler BM-35
Fig. 3.10 steam boiler BM-35 manufactured by the Belgorod Power Engineering Plant is a modern boiler with natural circulation, designed to operate on natural gas and fuel oil. Operating characteristics of the boiler are as follows: steam output 50 t/h; superheated steam pressure 3.9 MPa; temperature of superheated steam 440 °C.
The furnace chamber is shielded with 60 x 3 mm tubes. Downpipes are located outside the furnace chamber and are 83×4 mm in diameter. On the front wall of the boiler four gas burners of diffusion type 7 are installed.
1. drum; 2. regulator of superheated steam temperature; 3. steam superheater stages; 4. water economizer; 5. air heater; b. furnace chamber; 7. burners; 8. festoon; 9. external cyclone
Mixture of gas with swirling air flow occurs in the embrasure of the burner and ends in the furnace. The horizontal bottom of the furnace chamber is not shielded and is made of refractory bricks, laid on a layer of thermal insulating material.
Rear screen at the outlet of the combustion chamber is diluted and forms a three-row festoon In the horizontal gas duct of the boiler is set-. Two-stage steam superheater is installed (see Fig. 1). pos. and in the downpipe. water economizer, consisting of four packs, and air heater 5.
Two-stage superheater is made of pipes with diameter of 38 x 4 mm. Corridor arrangement of pipes. Saturated steam from the drum through overhead tubes enters the first steam superheater stage and flows in it countercurrently in relation to the steam flow. Then the steam enters the collector, where the superheated steam temperature regulator. surface-type steam cooler is located, in which the cooling feed water from the feed line enters. From the superheated steam temperature regulator, the last one enters the second-stage steam superheater, where the inlet coils are on counterflow and the outlet coils are on direct flow in relation to the direction of steam flow. There is a main steam valve above the steam superheater outlet manifold.
The water economizer of boiling type is made of steel tubes of 32 x 3 mm diameter arranged in a staggered arrangement. Steam and water mixture is drained from the upper collector, the last one in the water course of the package, through four pipelines connected to the drum. In horizontal and vertical directions, the coils of the economizer packs are distanced by special strips and hangers made of heat-resistant steel. During periods of firing up and stopping of the boiler, the economizer can be included in a line for water recirculation trimmer, which ensures its reliable cooling during these periods.
Air heater 5. steel tube (diameter of pipes 40×1,5 mm) two-way air, consists of six sections. The upper tube sheet of the air heater is connected to the gas duct by a lens compensator, which ensures its tightness from the air and gas side during thermal expansions of pipes and casing. Air heater heats air up to 200. 250°C.
The boiler jacket of a light type is fixed to the boiler frame and is made in two layers. The first layer, facing the inside of the smokebox, is made of fireclay bricks, the second one. of claydite insulating tiles. The sheathing is sealed by metal sheeting.
Evaporation system of the boiler is designed as a two-stage evaporation. First-stage evaporation circuits are incorporated directly into the drum. Separation of water-steam mixture coming from the first evaporation stage is carried out in cyclones installed in the drum. For dehumidifying the steam, louvered separators are installed at the drum outlet and behind them are louvered distribution panels. Steam from bypass cyclones of the second evaporation stage enters the steam space of the drum under the louvered separators and mixed with the main steam flow. Feed water through distributor louvers under the water level in the drum. Power