In addition, if you study the principle of operation, as well as the design features of such steam generators, you can try to implement them yourself, using certain means. However, this possibility will be discussed a little later.

Device and principle of operation

According to their design features, boiler plants have a fairly similar structure. They include several working nodes, which are considered to be decisive - directly itself, and the turbine. The last two components form a kinetic connection with each other, and one of the varieties of such systems is a steam-type turbine electric generator.

If you look more globally, then such installations are full-fledged thermal power plants, albeit smaller ones. Thanks to their work, they are able to provide electricity not only to civilian facilities, but also to large industrial sectors.

The very same steam electric generators boils down to the following main points:

• Special equipment heats water to optimal values, at which it evaporates, forming steam.
• The resulting steam enters further, onto the rotor blades of the steam turbine, which sets the rotor itself in motion.
• As a result, we first obtain the kinetic energy converted from the resulting energy of the compressed steam. Then the kinetic energy is converted into mechanical energy, which leads to the start of the turbine shaft.

The electric generator included in the design of such steam plants is decisive. This is due to the fact that it is the generators that convert mechanical energy into electrical energy.

Description:

Is it worth remembering the first domestic steam engines (see reference) in our age of high technology? Undoubtedly. After all, steam engines are now finding their application in the energy sector.

Mini-CHP with steam engines - a reality of the XXI century

I. S. Trokhin, Engineer VIESSH of the Russian Agricultural Academy, Lecturer of the MOPC National Research Nuclear University "MEPhI"

Is it worth remembering the first domestic steam engines (see reference) in our age of high technology? Undoubtedly. After all, steam engines are now finding their application in the energy sector.

Recently, in industry and housing and communal services, the expediency of the combined production of electric and thermal energy at steam mini-combined heat and power plants (mini-CHP) (Fig. 1), located in close proximity to the consumer, has been increasingly recognized.
This is due to the constant rise in the cost of electricity, the increase in cases of abnormal heavy winds and frosts, leading to a decrease in the reliability of power lines (wire breaks) of centralized power supply.

Boiler house as a source of heat and electricity

Consumers who have their own boiler houses sometimes supplement them with electric generating sets (electrical units) with steam engines (usually turbines) and electric generators with a capacity of several hundred kilowatts to a few megawatts. Thus, boiler houses reconstructed into mini-CHPs become sources of both thermal and electrical (Fig. 1, three-phase line A-B-C) energy.

Depending on the heat output of the steam boiler plant, 17–40 kW (1.7–4%) of electricity is required to generate 1 MW (100%) of heat energy. The absolute steam pressure in boilers, permitted by the authorities of Rostekhnadzor, usually does not exceed 0.7–1.0 MPa (hereinafter - absolute).

Industrial consumers or for steam-to-water heat exchangers (boilers for producing hot water) require steam with a lower pressure - 0.12–0.6 MPa. Therefore, generating sets with steam turbines are connected in parallel with reduction devices or instead of them (Fig. 1). Then, instead of useless throttling of steam by turbines, useful work will be done to drive electric generators. The exhaust steam in this case is sent to the boiler, after which it condenses, and the condensate is pumped back to the boiler through the cleaning system.

Thus, the boiler house becomes a profitable source of heat and electricity with a high efficiency of fuel combustion heat (80–85% or more).

If the consumer does not need a large amount of heat, but only hot water, for example, in the summer, then the mini-CHP is also equipped with absorption refrigeration machines operating on the steam exhausted in the turbine. Such machines provide the required cooling of water that enters the refrigeration system for air conditioning of the consumer's premises.

For year-round uninterrupted power supply to consumers, including mini-CHP equipment (pumps, smoke exhausters, lighting, automation systems, etc.), its non-stop operation is necessary. This is possible, for example, if electricity is generated together with the generation of heat necessary to provide consumers with hot water.

On the sites of existing boiler houses, mini-CHPs with increased thermal power are also being created. For example, obsolete boilers with a saturated steam pressure of 1.4 MPa are being replaced by boilers with a superheated steam pressure of 4.0 MPa and a temperature of 440 °C. With the same dimensions of the boilers, the electric power of such a mini-CHP becomes much larger.

However, attention should be paid to the type of steam engine used in modern mini-CHPs 1 . It is a low power steam turbine which is usually of single stage design as it operates at low pressure drops. The rotor, as the rotating part of the turbine, consists of a hub, which is mounted on the shaft, and a set of profiled blades (blade ring). The blades are made of special alloys and are responsible and expensive elements of the turbine. Steam-propeller turbines also have a profiled rotor, only of the Archimedes screw type.

Since the days of steam engines, a piston has been a simpler and cheaper working body than a turbine blade.

Comparison of the characteristics of electric generating sets with a steam turbine and a steam engine

Some designs of steam engines and motors of the last century were not so imperfect as it is believed. Let us imagine an electric generator set with a steam engine or motor and a modern electric generator. Since steam engines, as a rule, had very low shaft speeds (up to 300 rpm), and modern electric generators operate at frequencies of 1000–3000 rpm, a multiplier is also needed for an imaginary installation.

Let us compare such an installation with a modern steam turbine. Let's do it correctly: at commensurate pressures and temperatures of steam at the inlet to these engines and commensurate counterpressures of steam at the outlet. Then it becomes clear (Table 1) that the specific steam consumption per unit of generated electricity, and, consequently, the efficiency of some steam or steam engine installations is quite commensurate with the specific steam consumption in modern turbine plants, the power of which is even 5 times greater!

With an increase in the rotational speed of the shaft of a steam engine or motor, ceteris paribus, an increase in efficiency occurs due to a reduction in the duration of steam inlet into the cylinder and, consequently, a decrease in the time the steam contacts the cylinder walls, which leads to a decrease in heat loss in the engine.

At speeds of 750–1500 rpm and powers up to at least 1200 kW, modern German Spilling steam engines and Czech PM-VS have steam consumption 2 1.3–1.5 times less than steam turbines that exceed their power is more than 5 times! At the same power as turbines, steam engines are even more efficient, since it is easier to make more advanced steam distribution mechanisms in a relatively larger engine.

Russian innovation

Russian specialists proposed an idea: to convert a modern piston internal combustion engine (ICE) into a steam engine and adapt it to work in a mini-CHP. Since the cost of an internal combustion engine is lower than the cost of a steam turbine, then, subject to minor improvements in the design, we will get a cheaper drive engine: a steam engine based on a serial internal combustion engine.

Specialists of the joint scientific group 3 "Promteploenergetika", headed by V.S. Dubinin, a senior researcher at the Department of Aircraft Engine Design of the Moscow Aviation Institute, are developing steam piston engines (SPR) - modern single-pressure steam engines. The latter means that when the engine is running, the steam entering the cylinder puts pressure on the piston from only one side, as with the original internal combustion engine.

In the basic internal combustion engine, in fact, only the mechanism for supplying fuel to a gas-dynamic valve or spool-valve unit for supplying and releasing steam (know-how) is subject to alteration. PPD can operate in a wide range of live steam pressures - from 0.5 to 4.0 MPa at temperatures up to 440 °C. According to the frequency of rotation of the crankshaft, PPD can develop up to 3000 rpm!

PPD has a circulating lubrication system with a "dry" sump, as in the internal combustion engines of diesel locomotives and diesel power plants. With such a system, the oil, in general, does not linger in the internal cavities of the engine, but is pumped through them under pressure, cleaned and then re-entered into the engine.

In the RPM connected to the electric generator, steam is supplied from the boiler, and the exhaust is carried out to the steam-water heat exchanger (Fig. 2, blue symbols). PPD control is provided by signals from the automated control system. In addition to one or more PPDs and electric generators, the unit includes: a block of excitation, control and protection of the BVUZ of an electric generator, which, in turn, consists of excitation and control blocks of the BVU, protective automatics of the BZA, control system of the BSU.

On fig. 2 shows a variant of the electric unit with an asynchronous electric generator, therefore, for its operation, the BV excitation unit is equipped with capacitors. The switchgear electrically connects the generating set with electricity consumers. The dotted line (Fig. 2) shows electrical connections from other generators in the case of a multi-engine unit.

A steam engine, unlike a turbine, can always provide direct drive to an electric generator. The turbine usually requires a gearbox for this, since it must operate at high speeds to ensure an acceptable steam flow.

The steam turbine also requires a cooling system, which means additional water consumption and energy losses. It is quite enough to insulate the PPD, but it is not required to cool it, since the temperature in its cylinders is 5–6 times lower than that of the original internal combustion engine.

The resource before the overhaul of steam turbines (30,000–50,000 hours) is determined mainly by the resource of blades made of expensive alloys, and for steam engines (more than 50,000 hours, according to) - a much larger resource of cheaper units of the connecting rod and piston group.

Steam engines, like reciprocating steam engines, are highly reliable. And the resource before the overhaul of the PPD can be higher than that of the original internal combustion engines (30,000–100,000 hours), since the steam during engine operation, unlike the combustible mixture, does not explode, but expands and smoothly presses on the piston.

Turbine maintenance requires highly qualified personnel. Steam engines, being similar in type to internal combustion engines, can be serviced by less qualified specialists, and their repair can be done right on the spot.

Uninterruptible power supply application

In order to generate current with a frequency, in accordance with the requirements of 4 GOST 13109–97 for mains electricity (in normal mode - 50 ± 0.2 Hz), the PTEA steam turbine power plant (Fig. 2, red symbols) must work with an uninterruptible power supply UPS or in parallel with the centralized power supply network.

A steam turbine generating set generates electricity with a relatively coarse stabilization of the frequency of the alternating voltage. With the help of the voltage rectifier ABH, a constant voltage is obtained. Then the AVI inverting unit, equipped with a highly stable frequency master oscillator, ensures the conversion of direct voltage into alternating voltage with high frequency stabilization accuracy.

The AB storage battery unit is used for short-term backup power supply of the AE in case of failure of the turboelectric unit or for the period of emergency switching on of the reserve.

Motor shaft speed self-stabilization

All piston engines, including steam engines, have the property of self-stabilization of the shaft speed, which cannot be said about turbines. This discovery by VS Dubinin is revolutionary 5 . Its implementation makes it possible to maintain the speed of the prime mover shaft with such accuracy that the driven electric generator is capable of generating electricity at a frequency of 50±0.2 Hz, as required by power quality standards. For comparison, diesel power plants can generate electricity with a coarser frequency maintenance accuracy (in steady state operation - 50 ± 0.5 Hz).

Self-stabilization is carried out without the organization of feedback during pulsed supply or generation of the working fluid (steam) at regular intervals. Such a process, in fact, is similar to the operation of the escapement mechanism and the pendulum in a mechanical clock. In our case, this is a PPD with a steam source and a master steam supply pulse generator.

The point of view regarding the advantages of steam reciprocating engines over turbines for mini-CHPs is also shared by foreign experts. So, in 2005, at the American Council for an Energy Efficient Economy, Michael Muller from the Center for Advanced Energy Systems at Rutgers University in the USA noted in his report “The Return of the Steam Engine” that small-sized steam piston engines, unlike turbines, operate reliably and economically even on wet steam. and at moderate speeds.

Nevertheless, it should be noted that the vast majority of steam engines are still somewhat inferior to turbines in terms of mass and overall characteristics. However, as many years of operating experience shows, in particular, Spilling motors, these indicators are not paramount, against the background of a number of undeniable advantages of piston engines.

Re-equipment of water-heating boiler houses into steam mini-CHPs

But what to do with hot water boilers? How can they be converted into steam mini-CHPs? It is advisable to equip such boiler houses with additional steam boilers with the transfer of the basic part of the heat load to them or completely replace them with hot water boilers. Steam boilers are more expensive than hot water boilers, but their operating costs are lower and they can work reliably with a longer resource.

Environmental issues of mini-CHP operation

The environmental performance of fuel combustion in modern steam boilers is quite good. The implementation of the well-known domestic technology for burning solid fuels (coal, coal preparation waste, sludge, wood and plant waste, etc.) in a high-temperature circulating fluidized bed (utility model patent RU 15772) makes it possible to ensure the operation of the boiler with very low emissions into the atmosphere. The environmental performance of boilers with such furnaces meets the most stringent requirements of Rostekhnadzor.

In conclusion, it should be noted that power generating units with steam engines are the best suited for environmentally friendly solar power plants (Table 2), including mini-CHPs, in which boilers with solar collectors rather than furnaces are used to produce steam. It turns out a truly environmentally friendly power plant operating on the sun, water and steam!

So, we can draw the following conclusions:

• steam engine mini-CHPs are more energy efficient than steam turbine ones. For them, the specific steam consumption in electric units for generating electricity is 1.3–1.5 times less than in steam turbine mini-CHPs, especially at electric capacities up to 1200 kW.
• the resource before overhaul of modern steam engines for mini-CHPs is at least not lower than that of steam turbines of blade and screw types.

Literature

1. Burnosenko A. Yu. Mini-CHP with steam turbines to improve the efficiency of industrial heating boilers. 2009. No. 1.
2. Micro and small-scale CHP from biomass (up to 300 kWe). OPET RES-e NNE5/37/2002 // OPET Finland: http://web.archive.org/web/20070208002554/
   http://akseli.tekes.fi/opencms/opencms/OhjelmaPortaali/ohjelmat/DENSY/en/Documenttiarkisto/Viestinta_ja_aktivointi/Julkaisut/OPET-RES/TechnologyPaper2_chp_70404.pdf.
3. Dubinin V. S. Ensuring the independence of electricity and heat supply in Russia from electrical networks based on reciprocating technologies: monograph. M., 2009.
4. Shkarupa S. O. The use of point transformation for the analytical description of the transient process in a thermal engine of discrete action // Dynamics of complex systems. 2010. No. 2.
5. Muller M.R. The Return of the Steam Engine // ACEEE Summer Study on Energy Efficiency in Industry. New York (USA). July 19–22, 2005. http://quasiturbine.promci.qc.ca/Press/SteamMuller050721.pdf.

1 Historically, the term "steam engine" has been used to cover all designs of engines powered by steam. In the literature, sometimes the steam engine and the steam engine are mistakenly identified. A steam engine is a reciprocating steam engine.

3 The group includes specialists from the Moscow Aviation Institute, the All-Russian Institute for the Electrification of Agriculture, the Moscow Power Engineering Institute, the Moscow Institute of Energy Security and Energy Saving, and the Royal College of Space Engineering and Technology.

4 From 2013 GOST R 54149-2010 will be introduced instead of GOST 13109-97.

5 Note that V.S. Dubinin developed in the 1980s the theory of self-stabilization only for a single-cylinder piston engine and confirmed it experimentally. And in 2009, a young engineer, S. O. Shkarupa, applied this theory to the case of multi-cylinder piston engines, which one has to deal with in practice.

A steam generator is specialized equipment designed to convert a liquid, most often water, into steam. The liquid heats up when burning any fuel: wood, coal, oil or natural gas.

The transition of a liquid to a gaseous state creates pressure and then expansion, which can be directed and used as a source of energy.

Steam-powered pistons were instrumental in the development of factories, railroad locomotives, steamships, and many other pieces of mechanical equipment.

One of the earliest applications of the industrial steam generator in engineering was the steam locomotive. Fuel, in the form of firewood or coal, was fed into the furnace. The resulting heat was channeled through a system of pipes that heated the water, which was stored in a special tank.

Once the temperature reached boiling point, the energy created from the steam then drove the pistons that turned the wheels of the steam locomotive. The main function of steam power was the movement of the train, but it was also actively used in brakes and whistles.

Compared to steam boilers, steam generators contain less steel in construction and use a single steam coil instead of many small hoses. A specialized water supply pump is used to continuously pump water through the hose.

The steam generator uses in its design a one-time forced water supply in order to turn the incoming water into steam at a time using a heating coil.

As the water passes through the coil, heat is transferred from the burning gases and causes the water to turn into steam. The design of the generator does not use a steam collector, where there is free space between the steam and water inside, therefore, in order to achieve 99.5% steam quality, it is necessary to use a moisture / steam separator.

Because generators do not use a large pressure tank in their design like flame tubes, they are often very small and easy to start, making them ideal for situations where you need to get a small amount of steam in a short time.

However, this comes at a cost to power generation, as generators are not very efficient and therefore not always able to produce enough steam in different situations.

Advantages

According to their design and principle of operation, steam generators are quite similar to other systems of steam boilers, while remaining fundamentally different from them.

These, at first glance, insignificant differences change the entire operation of the system, which, as a rule, is less powerful than that of boilers, but has a number of advantages.

For example, steam generators have a simpler design, which allows them to start up much faster and be easier to operate than a full-scale industrial boiler. They are also smaller in size, making them more versatile, often seen as auxiliary boilers when working in tight spaces.

The next reason they are often used as auxiliary boilers is that they are quite easy and quick to start.

Due to their compact design, single coil and relatively lower water capacity, these machines can be started up and run at full capacity in a shorter time than full scale boilers, making them useful in emergency situations.

It's like comparing a race bike to a military tank - the former accelerates faster and runs fast but isn't very strong, while the latter takes a long time to start but is ultimately a more powerful machine. And while they generally cost a lot less than full-scale boilers, they can be more desirable for jobs that don't require such high steam levels.

Where applicable

When you think of steam power, you might think of steam engines or chugging locomotives. However, industrial steam generators have many applications:

• Distillation
• Sterilization
• Heat pump heating
• indirect heating
• Heating, ventilation and air conditioning

An electrical generator can convert approximately 97% of electrical energy from steam. Automatic safety control - a liquid level regulator, for example - maintains the required water level and turns off the generator if the water level drops below normal.

Steam generators with this functionality can work continuously without overheating.

Stainless steel steam generators are the best options when you need enough clean steam. Stainless steel reduces the chance of steam contamination.

Diesel steam generator

They follow a similar heat transfer concept as serpentine boilers, but can produce even higher pressures depending on the capacity. They are mainly used in power plants.

Their steam pressure can equal, and in some steam engines exceed the maximum water pressure of 221 bar. The steam temperature on these high pressure machines can reach 500 degrees Celsius.

Heat recovery steam generator

A heat recovery steam generator, or heat exchanger, collects clouds of steam under high pressure and uses this steam after exhaustion through a chain of heat exchangers to power other less powerful steam engines.

This recovered steam can even be used on these lower pressure generators to heat industrial plants or homes.

Steam generators for nuclear power plant

There are two main types of nuclear steam generators: (BWR), hot water reactor and (PWR), pressurized water reactor. The water in the BWR turns into steam inside the nuclear reactor itself and goes to a turbine outside the tank.

PWR water is under pressure over 100 bar and no water boiling processes occur inside the reactor.

Steam Solar Powered Generators

Solar steam generators are the cleanest way to generate steam. Water runs through pipes inside the solar panel.

The sun heats the water, and then the water passes through a steam turbine, creating electricity. This type of steam generator does not produce waste and does not pollute the environment.

Principle of operation

Heat exchange

Steam generators are used to capture and use the energy released as heat in a wide variety of processes and convert it into a more useful form such as mechanical and electrical energy.

The resulting heat is used to generate electricity or processed as a by-product of some other industrial process.

The immediate source of heat is usually contaminated, such as radioactive fuel in a nuclear power plant, so the first step in generating steam power is to transfer this heat to clean water using a heat exchanger.

This is done by raising the temperature of the fuel, such as gasoline, etc., which circulates in a closed circuit, with a heat source. The fuel, in turn, heats the water tank without polluting it.

Steam generation

The hot fuel is circulated through the water bath to produce steam. There are several different geometric schemes, but the principle remains the same.

The heated liquid is discharged through several small tubes to increase its surface contact with water and in order to ensure the acceleration of heat transfer and steam production.

The steam produced in modern nuclear and coal-fired power plants is often in supercritical conditions or above the critical point on the phase diagram of water (374 degrees Celsius and 22 MPa).

Turning heat into electricity

Supercritical steam is overloaded with energy. Steam energy is converted into mechanical energy by passing it through a steam turbine. The high steam pressure presses on the many inclined blades of the turbine, causing them to rotate.

This mechanical energy is converted into electrical energy by using the rotational energy of a steam turbine to power an electrical generator. The turbine shown in the image can generate up to 65 megawatts of electricity.

Conclusion

Each type of fuel is a source of heat for heating water. It's just that each of them does it in their own way. Some are environmentally friendly, while others have a fairly strong impact on the environment.