Water treatment in the energy sector: enemies of thermal power plants, water purification systems. Chemical shop. Water treatment processes

13.08.2012

One of the most important issues in the energy sector has been and remains water treatment at CHP. For energy companies, water is the main source of their work, and therefore very high requirements are placed on its content. Since Russia is a country with a cold climate, constant severe frosts, the operation of a thermal power plant is what people's lives depend on. The quality of the water supplied to the heat and power plant greatly affects its operation. Hard water results in a very serious problem for steam and gas boilers, as well as steam turbines of thermal power plants, which provide the city with heat and hot water.
In order to clearly understand how and what exactly hard water negatively affects, it would not hurt to first understand what a CHP is? And with what it "eat"?
So, a CHPP - a heat and power plant - is a kind of thermal power plant that not only provides heat to the city, but also supplies hot water to our homes and enterprises. Such a power plant is designed as a condensing power plant, but differs from it in that it can take part of the thermal steam after it has given up its energy.

Steam turbines are different. Depending on the type of turbine, steam with different indicators is selected. Turbines in the power plant allow you to adjust the amount of steam taken.
The steam that has been extracted is condensed in the network heater or heaters. All energy from it is transferred to network water. Water, in turn, goes to peak water heating boiler houses and heat points. If the steam extraction paths are blocked at the CHPP, it becomes a conventional IES. Thus, the heat and power plant can operate according to two different load schedules:

thermal graph - directly proportional dependence of the electrical load on the thermal;
electrical graph - there is either no heat load at all, or the electrical load does not depend on it.

The advantage of CHP is that it combines both heat and electricity. Unlike IES, the remaining heat does not disappear, but is used for heating. As a result, the efficiency of the power plant increases. For water treatment at CHPPs, it is 80 percent versus 30 percent for IES. True, this does not speak of the efficiency of the heat and power plant. Here, the price includes other indicators - the specific generation of electricity and the efficiency of the cycle.
The peculiarities of the location of the CHP should include the fact that it should be built within the city. The fact is that the transfer of heat over distances is impractical and impossible. Therefore, water treatment at CHPPs is always built near consumers of electricity and heat.
What is the water treatment equipment for CHP? These are turbines and boilers. Boilers produce steam for turbines, turbines produce electricity from steam energy. The turbine generator includes a steam turbine and synchronous generator. Steam in turbines is obtained by using fuel oil and gas. These substances heat the water in the boiler. The pressurized steam turns the turbine and the output is electricity. Waste steam is supplied to homes in the form of domestic hot water. Therefore, the exhaust steam must have certain properties. Hard water with a lot of impurities will not allow you to get high-quality steam, which, moreover, can then be supplied to people for use in everyday life.
If the steam is not sent to supply hot water, then it is immediately cooled in the thermal power plant in cooling towers. If you have ever seen huge pipes at thermal stations and how smoke pours from them, then these are cooling towers, and smoke is not smoke at all, but the steam that rises from them when condensation and cooling occurs.
How does it work water treatment at CHP we figured out that the most affected by hard water here is the turbine and, of course, boilers that convert water into steam. The main task of any thermal power plant is to get clean water in the boiler.
Why is hard water so bad? What are its consequences and why do they cost us so much?
Hard water differs from ordinary water by its high content of calcium and magnesium salts. It is these salts that, under the influence of temperature, settle on heating element and walls of household appliances. The same applies to steam boilers. Scale forms at the heating point and the boiling point along the edges of the boiler itself. Descaling in the heat exchanger in this case is difficult, because. scale builds up on huge equipment, inside pipes, all kinds of sensors, automation systems. Flushing the boiler from scale on such equipment is a whole multi-stage system, which can even be carried out when disassembling the equipment. But this is the case high density scale and its large deposits. The usual remedy for scale in such conditions, of course, will not help.
If we talk about the consequences of hard water for everyday life, then this is the impact on human health and the rise in the cost of using household appliances. In addition, hard water is very bad in contact with detergents. You will use 60 percent more powder, soap. Costs will grow by leaps and bounds. Water softening was therefore invented to neutralize hard water, you put one water softener in your apartment and forget that there is a descaling agent, a descaling agent.

Scale is also characterized by poor thermal conductivity. This lack of it is the main cause of breakdowns of expensive household appliances. A thermal element covered with scale simply burns out, trying to give off heat to the water. Plus, due to the poor solubility of detergents, washing machine you need to additionally turn on the rinse. These are the costs of water and electricity. On any side, water softening is the most reliable and economically profitable option prevent scale formation.
Now imagine what is water treatment at a CHP in industrial scale? There, the descaler is used by the gallon. Flushing the boiler from scale is carried out periodically. It happens regularly and repair. To make descaling more painless, water treatment is needed. It will help prevent the formation of scale, protect both pipes and equipment. With it, hard water will not exert its destructive effect on such an alarming scale.
If we talk about industry and energy, then most of all hard water brings trouble to thermal power plants and boiler houses. That is, in those areas where there is direct water treatment and heating of water and the movement of this warm water through water pipes. Water softening is as necessary here as air.
But since water treatment at a thermal power plant is work with huge volumes of water, water treatment must be carefully calculated and thought out, taking into account all sorts of nuances. From the analysis of the chemical composition of water and the location of a particular water softener. In CHP, water treatment is not only a water softener, it is also equipment maintenance after. After all, descaling will still have to be done in this production process, with a certain frequency. More than one descaler is used here. It can be formic acid, and citric, and sulfuric. In various concentrations, always in the form of a solution. And one or another acid solution is used, depending on what components the boiler, pipes, controller and sensors are made of.
So, which energy facilities need water treatment? These are boiler stations, boilers, this is also part of the CHPP, water heating installations, pipelines. by the most weak points and thermal power plants, including pipelines. Scale accumulating here can also lead to depletion of pipes and their rupture. When the scale is not removed in time, it simply does not allow water to pass through the pipes normally and overheats them. Along with scale, the second problem of equipment in CHP is corrosion. It also cannot be left to chance.
What can lead to a thick layer of scale in the pipes that supply water to the CHP? This is a difficult question, but we will now answer it knowing what water treatment at CHP. Since scale is an excellent heat insulator, the heat consumption increases sharply, while the heat transfer, on the contrary, decreases. The efficiency of boiler equipment drops significantly, and as a result, all this can lead to rupture of pipes and explosion of the boiler.

This is something you can't skimp on. If in everyday life, you still think whether to buy a water softener or choose a descaler, then such bargaining is unacceptable for thermal equipment. At thermal power plants, every penny is counted, so descaling in the absence of a softening system will cost much more. And the safety of devices, their durability and reliable operation also play a role. Descaled equipment, pipes, boilers work 20-40 percent more efficiently than equipment that has not been cleaned or works without a softening system.
main feature water treatment at a thermal power plant is that it requires deeply demineralized water. To do this, you need to use precise automated equipment. In such production, reverse osmosis and nanofiltration, as well as electrodeionization, are most often used.
What stages does water treatment in the energy sector include, including at a heat and power plant?
The first stage includes mechanical cleaning from all kinds of impurities. At this stage, all suspended impurities are removed from the water, up to sand and microscopic rust particles, etc. This is the so-called coarse cleaning. After it, the water comes out clean for the human eye. Only dissolved hardness salts, ferrous compounds, bacteria and viruses, and liquid gases remain in it.

When developing a water treatment system, it is necessary to take into account such a nuance as the source of water supply. Is it tap water from public water systems or is it water from a primary source?
The difference in water treatment is that the water from the water supply systems has already passed the primary treatment. Only hardness salts should be removed from it, and deferrized if necessary.
Water from primary sources is absolutely untreated water. That is, we are dealing with a whole bouquet. Here it is imperative to carry out a chemical analysis of water in order to understand what impurities we are dealing with and what filters to install to soften the water and in what sequence.
After rough cleaning, the next stage in the system is called ion-exchange demineralization. An ion exchange filter is installed here. Works on the basis of ion-exchange processes. The main element is an ion exchange resin, which includes sodium. It forms weak bonds with resin. As soon as hard water at a thermal power plant enters such a softener, the hardness salts instantly knock sodium out of the structure and firmly take its place. Restoring such a filter is very simple. The resin cartridge is moved to the recovery tank, where the saturated brine is located. Sodium takes its place again, and hardness salts are washed into the drain.
The next step is to obtain water with desired characteristics. Here, a water treatment plant is used at a thermal power plant. Its main advantage is the receipt of 100% pure water, with the specified indicators of alkalinity, acidity, mineralization level. If the company needs industrial water, then the reverse osmosis plant was created just for such cases.

The main component of this installation is a semi-permeable membrane. The selectivity of the membrane varies, depending on its cross section, water with different characteristics can be obtained. This membrane divides the tank into two parts. One part contains a liquid with a high content of impurities, the other part contains a liquid with a low content of impurities. Water is launched into a highly concentrated solution, it slowly seeps through the membrane. Pressure is applied to the installation, under the influence of it, the water stops. Then the pressure is sharply increased, and the water begins to flow back. The difference between these pressures is called osmotic pressure. The output is perfectly pure water, and all deposits remain in a less concentrated solution and are discharged into the drain. The disadvantages of this method of drinking water treatment include high water consumption, hazardous waste and the need for water pretreatment.
Nanofiltration is essentially the same reverse osmosis, only low-pressure. Therefore, the principle of operation is the same, only the water pressure is less.
The next stage is the elimination of gases dissolved in it from the water. Since CHP plants need clean steam without impurities, it is very important to remove oxygen, hydrogen and carbon dioxide dissolved in it from the water. The elimination of impurities of liquid gases in water is called decarbonation and deaeration.
After this stage, the water is ready for supply to the boilers. Steam is obtained at exactly the concentration and temperature that is needed. None additional cleanings do not need to be carried out.
As can be seen from the above, water treatment in CHP- one of the most important components production process. Without clean water, there will be no high-quality good steam, which means there will be no electricity in the right amount. Therefore, water treatment in thermal power plants should be dealt with tightly, trust this service exclusively to professionals. A properly designed water treatment system is a guarantee of long-term equipment service and quality energy supply services. Now you know that NPI "GENERATION Ufa" knows how to treat water at a thermal power plant.
______________________________________________________________________________________________________________

It is somehow difficult to imagine thermal power plants without working with water. home driving force in such production, just water is. And in order for the CHP, that is, the heat and power plant to work without interruption, it does not hurt to take care of the quality of the water entering it in advance. And with the current water treatment water treatment at CHP will not be superfluous, but extremely necessary and important.

How are they doing?

The difference in the operation of boiler houses in Russia and, for example, European Denmark, is significant. But we can safely say that Europeans do not have to work in such difficult weather conditions. In the same place in Denmark, they don’t work at temperatures over thirty, both in hellish heat and in wild cold. Any CHP plant will work longer and better if it is properly operated and if the water supplied to it meets the requirements of the equipment.

At one time, a wave of updates and requirements for make-up water swept through Europe. Today they work, for example, in Denmark for water with a temperature of thirty-five to almost two hundred degrees. At the same time, the requirements for the operation of CHP clearly state that aluminum parts cannot be mounted. The reason is that at the level of acid-base balance equal to 8.7, the system will necessarily begin corrosion processes. Such CHPPs operate on softened or demineralized deaerated water. Moreover, for each type of water, the following input requirements must be met:

Of all the impurities that can only be found in water, the greatest danger directly to heating plants will be precisely the hardness of the water. The presence of a significant excess of the calcification threshold will be a direct cause of the formation limescale on the walls of the equipment. And moreover, this scum will hit everything with which it will cooperate.

If there was no such great harm from scale, then no one would pay attention to it, but in fact, it settles everywhere:

Heat exchangers;
pipes;
Cauldrons.

The result of this contact is bad job boiler room or CHP in the complex. Fuel consumption is growing exponentially. And the thicker the scale, the more difficult it is to heat the surface. This is the main reason for such an urgent need for water softening. If the scale exceeds a certain threshold, then the heat from the heating element or the walls of the equipment will stop flowing into the water. At the same time, heat cannot be absorbed somewhere. It begins to accumulate, and not just anywhere, but directly in the metal of the walls or the heating element. Even the most hardened metal will not be able to withstand constant heating for a long time. Crooked pipes, as if torn from the inside, these are the consequences of just a millimeter layer of scale. Therefore, scale in thermal power plants is treated very reverently. The layer is thin, and the boiler can easily break. And that's a big expense. Therefore, water can either be desalinated or softened. And the difference between these concepts is small, but there is. Softening involves the elimination of two mineral salts, and desalting involves the complete elimination of salts. That is, the result is a distillate.

But no matter how the water is cleaned and prepared, a certain percentage raw water can still enter the water treatment system. Tanks can leak, and while the same electromagnetic device does not work, because. water is at rest, it is also possible for some hard water to enter the system. To neutralize such water, chemicals are used in the water treatment system at the CHP plant. They are injected into the water supply system, the salts form an easily removable precipitate that is easy to remove from the equipment. And he does not stick to the walls.

By the way, scale is also harmful because, as a result of poor thermal conductivity, corrosion appears on surfaces, the metal then becomes almost soft. He then overheats, becomes more susceptible to water. The percentage increase in surface heating temperature due to scale can reach up to 50 percent!

The next enemy of the equipment of the combined heat and power plant, stimulated by scale, is, as mentioned above, corrosion. And already have to decide not one, but two at once big problems. In order for the metal to begin to carrode, it is necessary that air is freely available to its surface. Therefore, in fact, for the operation of circulating water, they buy. And the higher the percentage of oxygen, the higher the probability of formation of corrosion centers.

Filters and a new interpretation of water treatment at thermal power plants

In Russian realities, they prefer to deal more with corrosion than with its origins. Only in boiler houses where there is the possibility of water treatment at the CHP and not only includes degassing. In Denmark, for example, not every CHP plant has such installations. In most cases, oxygen is dealt with by adding conventional chemicals. Although in Russia today many central plants work with conventional chemical softening or preventive washings, because for a full good system there is simply no money for water treatment.

An important indicator of the correct is the pH level. And when it is circulating water, its value should not go beyond the range from nine and a half to ten. The fork is quite small. But on the other hand, a high value of this indicator guarantees the protection of iron surfaces. Moreover, the dependence of the level of acid-base balance on the corrosion of metals can also be applied to brass, copper or zinc. But when working with this indicator, you need to remember about the work of alkali. For example, an indicator above ten will again lead to the risk of corrosion, zinc from brass will begin to be massively washed out.

The main work of proper water treatment at thermal power plants is taken over by filtering installations. The system will work best if not only dissolved metal salts, but also solid impurities are eliminated from it. This will make it possible not only to prevent the formation of scale and corrosion, but also to slow down the wear of the equipment. Yes, and bottlenecks in the system, the pumps will be safer.

Therefore, water treatment systems are a complex treatment with mechanical filters and softeners. Moreover, cleaning can be either complete or partial. Moreover, the system is not mounted on the main pipeline, which does not interfere with the normal continuous circulation of water. It is better, of course, when the filtration unit can be easily dismantled and cleaned. In the event that water is reused, it is better to mount cleaning system directly to the main pipe. But even here there should be sensors that, in the event of a clogged one of the filters, will quickly forward the flow through another circuit, and signal the problem to the control center.

Today, in order to save money, they began to massively use plastic as the main material for softening installations. But, unfortunately, while the hopes placed on him, he does not justify. The use of stainless steel seems to be more promising. Moreover, the problem with microbacteria has not yet been completely eliminated.

The trouble with plastic is that it easily concentrates oxygen. And therefore, the installation of unprotected pipelines becomes completely unprofitable, because. corrosion will begin to progress in the system and very quickly. But today there are special barrier devices that help remove oxygen from plastic with almost a hundred percent probability.

The next problem that is still being fought is bacteria. No matter how they tried to remove them. And most importantly, even soft purified water does not save, because the reagent can be put more than usual, so it turns out that the water begins to rot, the bacteria spread very quickly. In addition, bacteria are sand, dirt that accidentally got into the heating system. A special expanse of bacteria occurs inside the water supply systems, here they accumulate and can give the water an unpleasant odor. Bacteria can be eliminated by chemical reactions. Disinfection is by far the most effective and affordable way to eliminate bacteria from your heating plant.

Stainless steel has become one of the features of the new water supply systems for boiler houses and insulation. easier to tolerate bacterial plaque, but does not tolerate temperature and chloride compounds. When planning to mount such an installation, it is imperative to do a water analysis in order to know which one to choose. Yes, and the percentage of chloride is so awesome for stainless steel, it also does not hurt to find out. And in no case should such a surface be washed with perchloric acid. It will destroy the protective film of stainless steel.

As you can see, only careful preparation will help to establish correct system water treatment. And then it will always be warm in the houses of the inhabitants.

Is the liquid used in thermal power engineering subject to mandatory purification? both before and after use. Passing through treatment facilities allows you to protect pipes and boilers from corrosion, scale formation, as well as disinfect effluents for their further return to the environment. Only a specialist will be able to determine the stages and what is used for water treatment at a thermal power plant after a complete chemical and biological analysis. This will allow you to identify the need for the use of certain reagents and draw up optimal scheme purification facility.

To date, the goal of the reconstruction of the chemical water treatment system of the CHPP is to obtain better quality raw materials with minimum cost funds. Scientists offer new ways to filter liquids, the use of safe oxidizers and neutralizers. One of the popular methods is reverse osmosis, which is often used in various industries. The standard scheme, typical instructions for reverse osmosis water treatment allows you to get rid of dissolved salts, metals and impurities. The principle of its operation is to run the liquid through membranes with cells, the size of which depends on the type of pollution. Due to its high efficiency this scheme water treatment at thermal power plants, ktets 3 for bottled water is successfully used in many enterprises. The final stage of liquid purification for these purposes is its passage through a modern steam sterilizer with water treatment and a set of spare parts, which, due to high steam pressure, ensures complete purification of it from all kinds of bacteria.

Water treatment processes at CHPPs and TPPs

One of the most modern, efficient and safe methods is water treatment by ozonation to obtain demineralized water with a capacity of 100 l/h, actively using the high oxidizing properties of ozone. It is able to oxidize both dissolved salts and metals. At the same time, the danger of using chlorine preparations is prevented; ozonation of purified water in water treatment systems allows not only to neutralize chemicals, but also to saturate the liquid with oxygen resulting from the oxidation reaction. This method makes it possible to avoid the use of chemicals such as chlorine, sodium hypochlorite, etc. It solves main problem filtration of H2O for CHP is its desalination and iron removal. The cartridges used for the Feed Water ozone water treatment station almost completely purify the liquid to a state ready for use. The method has not been widely used due to its high energy consumption. Continuous production of ozone by equipment requires a large number electricity, which is too expensive for many businesses.

In order to reduce costs, many enterprises prefer automatic control water treatment process for thermal power plants, doc certificates of which indicate the compliance of equipment with all established standards. The use of modern filters for desalination or clarification of H2O provides high results that will protect equipment from scale formation and corrosion. Many processes and devices, calculation of equipment and water treatment devices at thermal power plants can not only completely purify the liquid, but also significantly reduce costs, since even a thin layer of scale on pipes increases energy costs to heat them to the desired temperature. One of the most important tasks water treatment at CHP puts the elimination of limescale. To solve this problem, devices for water treatment of desalination in a steam boiler using coagulants or flocculants are used. The most common is thermal method. Its essence lies in increasing the temperature of the liquid to such an indicator at which salts of harmful substances will be destroyed. The method is not suitable for all cases, because it dissolves only a part of the chemicals. Magnetic water treatment is considered more effective, the use of ultrasound for thermal power plants, which not only destroy calcium and magnesium salts with the help of constant magnetic field, but also do not allow them to settle on the sorption elements. They are deposited in the form of soft sludge in special tanks. This method effective not only for softening liquids, but also well proven in the fight against bacteria and other chemicals.

Water treatment of steam generators at CHP

A very important point is the causes and consequences of saturated steam pollution in water treatment, the serviceability of the steam generator, and the choice of H2O filtration method. Fluid requirements depend on the country of manufacture of the steam generator. So, domestic water treatment facilities may not be suitable for foreign equipment. Insufficient filtration of H2O may result in damage to the apparatus. For this reason, it is very important to prevent salts, iron, bacteria and other contaminants from remaining in the liquid. It is very important to control the balance of water, GENODOS type dm1/20 s units for chelating water treatment allow precise dosing of chemical reagents, reaching their optimal concentration. About what new reagents, dosing units are currently used at the stations, you can consult with the specialists of our company. They will offer the best water treatment at thermal power plants, including the most effective methods and reagents.

In addition to removing salts from liquids, it is very important for a CHP plant to neutralize the iron present in it. Its presence can lead to damage to the steam generator. To solve this problem, you can use the T 20 electromagnetic water treatment device, which neutralizes iron anions and cations by ion exchange. In addition to eliminating this substance, the device also copes with many other types of pollution. Processes such as demineralization, disinfection of recycled water at CHP plants can be carried out using UV radiation. This requires special chambers with an input and output for H2O and a lamp, which will be the main element of this circuit. The liquid exposed to UV rays will be sent to the steam generator and the resulting sludge will be removed from the tank. The method is as simple as it is effective. Standard water treatment at a thermal power plant, iron removal, in which it is a mandatory procedure, can take place both with and without reagents. For iron filtration, reverse osmosis systems, ozonation, ion exchange method and others can be used. The choice depends on the amount of liquid used and the degree of contamination. It is impossible to talk about the universality of any method, because each of them has its pros and cons, characteristic only for it.

Demineralization and water treatment at CHPP

The total cost of installation of water treatment for demineralized mineral water steam generators depends on the factors mentioned above. It is calculated individually and may increase depending on the growth of requirements for the quality of the final product, imposed by supervisory organizations and the managers of the CHPP themselves.

For water treatment at mineral water plants, it will be mandatory to disinfect it using UV radiation or ozonation. The filtration system will in this case consist of several stages, each of which uses its own methodology. It is also necessary to take into account the engineering and environmental aspects of water treatment, their impact on the environment and human health.

The effluents generated during the use of the liquid must not contain substances that threaten the ecological balance of the natural complex. All toxic and hazardous substances must be removed before the water is released into water bodies. The main thing that water treatment must take into account in thermal networks, heat power engineering, and heat supply is the filtration of liquid from calcium, magnesium and iron salts. It is these substances that cause damage to equipment and an increase in the cost of heat transfer reactions. Cleaning the liquid before using it in a CHP plant is not only a necessary measure to comply with the requirements of the sanitary services, but also a real opportunity to significantly reduce the costs of the organization. This is due to the reuse of H2O, the safety of steam generators, boilers and other equipment. Modern leaders have long understood that investments in wastewater treatment plants pay off very quickly and help to increase the profitability of the enterprise.

To date, water treatment in the energy sector remains an important issue in the industry. Water is the main source at TPPs, including TPPs, which are subject to increased requirements. Our country is located in a cold climate zone, severe frosts occur in winter. Therefore, TPPs are an integral part comfortable life of people. Thermal power plants, steam and gas boilers suffer from hard water, which disables expensive equipment. For a clearer understanding, we will deal with the principles of operation of the CHP.

The principle of operation of the CHP

CHP (thermal power main) is considered a type of thermal power plant. It generates electrical energy and is a source of heat in the heat supply system. From the CHP, hot water and steam are supplied to people's homes and industrial enterprises.

The principle of its operation is similar to a condensing power plant. There is only one important difference: part of the heat can be sent to other needs. The amount of selected steam is regulated at the enterprise. Thermal turbine determines how energy is collected. The separated steam is collected in the heaters. The energy is then transferred to the water, which moves through the system. It transfers energy to peak water heating boiler houses and heat points.

Water treatment can have two load curves:

thermal;
electric.

If the main one is thermal load, then the electric one obeys it. If an electrical load is installed, then the thermal load may even be absent. A combined load option is possible, which makes it possible to use the residual heat for heating. Such CHP plants have an efficiency of 80%.

When constructing a CHPP, the absence of heat transfer to long distance. Therefore, it is located in the city.

CHP problems

The main drawback of energy production at thermal power plants is the formation of a solid precipitate that precipitates when water is heated. To clean the system, it will be necessary to stop and dismantle all equipment. Scale is removed at all turns and in narrow openings. In addition to scale, well-coordinated work will be hampered by corrosion, bacteria, and so on.

Scale

The main disadvantage of scale is a decrease in thermal conductivity. Even its insignificant layer leads to high fuel consumption. Permanent descaling is not possible. Only monthly cleaning is allowed, which incurs losses from downtime and damages the surface of the equipment. The amount of fuel consumed will increase, and the equipment will fail faster.

How to determine when to clean up? The equipment will report itself: the overheating protection systems will work. If scale is not removed, heat exchangers and boilers will not work in the future, fistulas will form or an explosion will occur. All expensive equipment will fail without the ability to restore it.

Corrosion

The main cause of corrosion is oxygen. Circulating water should have it at a minimum level - 0.02 mg / l. If there is enough oxygen, then the likelihood of corrosion on the surface will increase with the increase in the amount of salts, especially sulfates and chlorides.

Large CHP plants have deaerator installations. On the small installations corrective chemicals are used. The pH value of the water should be in the range of 9.5-10.0. With an increase in pH, the solubility of magnetite decreases. It is especially important if brass or copper parts are present in the system.

Plastic is a source of local oxygen release. Modern systems try to avoid flexible plastic pipes or create special oxygen barriers.

bacteria

Bacteria affect the quality of the water used and form some types of corrosion (bacteria on metal and sulfate reducing bacteria). Signs of bacterial growth:

specific smell of circulating water;
content deviation chemical substances when dosing;
corrosion of copper and brass components, as well as batteries.

Bacteria come with dirt from the soil or during repairs. The systems and the lower part of the battery have favorable conditions for their growth. Disinfection is carried out with a complete shutdown of the system.

Water treatment for CHP

Water treatment in the energy sector will help to cope with these problems. Thermal power plants install a lot of filters. The main task is to find the optimal combination of different filters. The outlet water must be softened and demineralised.

Ion exchange plant

The most common filter It is a tall cylindrical tank with an additional regeneration tank for the filter. The round-the-clock operation of the CHP requires an ion exchange plant with several stages and filters. Each of them has its own recovery tank. The whole system has a common controller (control unit). It monitors the operation parameters of each filter: the amount of water, cleaning speed, cleaning time. The controller does not pass water through filters with full cartridges, but sends it to others. Dirty cartridges are removed and sent to the remanufacturing tank.

The cartridge is initially filled with low sodium resin. When passing through hard water, chemical reactions: strong salts are replaced by weak sodium. Over time, hardness salts accumulate in the cartridge - it should be regenerated.

Salts of a high degree are dissolved in the recovery tank. A highly saturated salt solution (more than 8-10%) comes out, which removes hardness salts from the cartridge. Heavily salted waste is additionally cleaned, and then disposed of by special permission.

The advantage of the installation is the high speed of cleaning. Disadvantages include costly plant maintenance, high cost of salt tablets, and disposal costs.

Electromagnetic water softener

It is also common in CHP. The main elements of the system are:

strong permanent magnets made of rare earth metals;
pay;
electrical processor.

These elements create a strong electromagnetic field. On opposite sides, the device has wound wiring along which waves travel. Each wire is wound more than 7 times on the pipe. During operation, make sure that water does not come into contact with the wiring. The ends of the wires are insulated.

Water passes through the pipe and is irradiated with electromagnetic waves. Hardness salts are transformed into sharp needles, which are inconvenient to “stick” to the equipment surface due to the small contact area. Additionally, needles qualitatively and finely clean the surface of old plaque.

Main advantages:

self-service;
no need to care;
service life of more than 25 years;
no additional costs.

The electromagnetic softener works with all surfaces. The basis of the installation is installation on a clean section of the pipeline.

Reverse osmosis

In the production of make-up water, a reverse osmosis system is indispensable. She is the only one who can purify water by 100%. It uses a system of various membranes that provide the necessary characteristics of water. The downside is the lack of the possibility of independent use. The reverse osmosis installation must be supplemented with water softeners, which affects the cost of the system.

Only a complete water treatment and purification system guarantees a 100% result and compensates for the high cost of equipment.

The method of water treatment has a strong influence on the operation of heat supply. Depend on him economic indicators operation and protective function of the system. During the construction or planned repair of a CHP, special attention should be paid to water treatment.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Ministry of Education and Science of the Russian Federation

Branch of the Federal State Budgetary Educational Institution of Higher Professional Education "South Ural State University» (national research

University) in Satka

Test

in the discipline "General Energy"

topic: "Chemical water treatment at a thermal power plant"

INTRODUCTION

Energy consumption is a prerequisite for the existence of mankind. The availability of energy available for consumption has always been necessary to meet human needs, increase the duration and improve the conditions of his life. The history of civilization is the history of the invention of more and more new methods of energy conversion, the development of its new sources and, ultimately, an increase in energy consumption. The first jump in the growth of energy consumption occurred when people learned how to make fire and use it to cook and heat their homes. During this period, firewood and the muscular strength of a person served as sources of energy. Next milestone associated with the invention of the wheel, the creation of various tools, the development of blacksmithing. By the 15th century medieval man, using draft animals, water and wind power, firewood and a small amount of coal, already consumed about 10 times more than primitive man. A particularly noticeable increase in world energy consumption has occurred over the past 200 years since the beginning of the industrial era - it has increased 30 times and reached 14.3 Gtce/year in 2001. A man in an industrial society consumes 100 times more energy than a primitive man, and lives 4 times longer. In the modern world, energy is the basis for the development of basic industries that determine the progress of social production. In all industrialized countries, the pace of development of the energy industry outpaced the pace of development of other industries. Power plant - a power plant that serves to convert any energy into electrical energy. The type of power plant is determined, first of all, by the type of energy carrier. The most widespread are thermal power plants (TPPs), which use thermal energy released by burning fossil fuels (coal, oil, gas, etc.). Thermal power plants generate about 76% of the electricity produced on our planet. This is due to the presence of fossil fuels in almost all areas of our planet; the possibility of transporting organic fuel from the place of production to the power plant located near energy consumers; technical progress at thermal power plants, which ensures the construction of high-capacity thermal power plants; the possibility of using the waste heat of the working fluid and supplying consumers, in addition to electrical, also thermal energy (with steam or hot water), etc.

Depending on the source of energy, there are: - thermal power plants(TPP) using natural fuel; - hydroelectric power plants (HPP) using the energy of falling water of dammed rivers;

Nuclear power plants (NPPs) using nuclear energy; - other power plants using wind, solar, geothermal and other types of energy.

Our country produces and consumes a huge amount of electricity. It is produced almost entirely by the three main types of power plants: thermal, nuclear and hydroelectric power plants.

In Russia, about 75% of energy is produced at thermal power plants. TPPs are built in fuel extraction areas or in energy consumption areas. It is advantageous to build hydroelectric power stations on full-flowing mountain rivers. Therefore, the largest hydroelectric power plants are built on Siberian rivers. Yenisei, Angara. But cascades of hydroelectric power stations have also been built on the flat rivers: the Volga, the Kama. combined heat and power plant turbine water treatment

Nuclear power plants are built in areas where a lot of energy is consumed, and other energy resources are not enough (in the western part of the country).

The main type of power plants in Russia are thermal (TPP). These installations generate approximately 67% of Russia's electricity.

Their placement is influenced by fuel and consumer factors. The most powerful power plants are located in the places where fuel is extracted. Thermal power plants using high-calorie, transportable fuel are consumer-oriented.

1. THERMAL POWER PLANTS (CHP)

This type of power plant is designed for centralized supply industrial enterprises and cities with heat and electricity. Being, like IES, thermal stations, they differ from the latter in the use of heat from the steam “exhausted” in turbines for the needs of industrial production, as well as for heating, air conditioning and hot water supply. With such a combined generation of electrical and thermal energy, significant fuel savings are achieved in comparison with separate energy supply, i.e., electricity generation at CPP and heat from local boiler houses. Therefore, CHPs have become widespread in areas (cities) with high consumption of heat and electricity. In general, CHPs produce up to 25% of all electricity generated in the country.

Parts of the scheme, which are similar in structure to those for IES, are not shown here. The main difference lies in the specifics of the steam-water circuit and in the method of generating electricity.

Rice. 1. Features of the technological scheme of a station of the CHP type:

1 -- network pump; 2 -- network heater

As can be seen from fig. 1, steam for production is taken from intermediate turbine extractions after it has given off a significant part of the energy at a pressure of 10–20 kgf/cm2, while its primary parameters before the turbine are 90–130 kgf/cm2.

For heat supply, steam is taken at a pressure of 1.2-2.5 kgf / cm2 and enters the network heaters 2 (Fig. 1). Here it gives off heat to the network water and condenses. The heating steam condensate is returned to the main steam-water circuit, and the water pumped into the heaters by network pumps 1 is directed to the needs of heating.

It is clear that the greater the commercial heat supply (i.e. heat consumption) and the less heat is wasted away by circulating water, the more economical the process of generating electricity at a CHP plant.

In general, the CHP efficiency exceeds the efficiency of IES. Depending on the amount of heat consumption, it can be 50--80%.

If there is no or little heat consumption, the CHP plant can generate electricity in the condensing mode. However, in this mode, CHPP units are inferior in terms of technical and economic indicators to IES units.

The specificity of the electrical part of the CHPP is determined by the position of the station near the centers of electrical loads. Under these conditions, part of the power can be supplied to the local network directly at the generator voltage. For this purpose, a generating station is usually created at the station. Switchgear(GRU). Excess power is supplied, as in the case of CES, to the system at increased voltage.

An essential feature of the CHPP is also the increased capacity of thermal equipment compared to the electric power of the plant, taking into account the production of thermal energy. This circumstance predetermines a higher relative consumption of electricity for own needs than in the case of IES.

2. CHEMICAL WATER TREATMENT AT CHPP

In thermal power engineering, the main heat carrier is water and the steam formed from it. Impurities contained in the water entering the steam boiler with feed water, and in hot water - with network, form low-thermal-conductive deposits and scale on the heat exchange surface, which heat-insulate the surface from the inside, and also cause corrosion. Corrosion processes, in turn, are an additional source of impurities entering the water.

As a result, the thermal resistance of the wall increases, heat transfer decreases, and, consequently, the temperature of the flue gases increases, which leads to a decrease in the efficiency of the boiler and excessive fuel consumption. With excessive temperature rises in the metal of pipes, their strength decreases, up to the creation of an emergency.

At low and medium pressures in drum boilers, impurities enter the steam only as a result of the entrainment of droplets of boiler water, that is, if the drying of the apparatus is not effective enough. At high pressures impurities begin to dissolve in the vapor and the more intense, the higher the pressure, and, first of all, silicic acid.

Therefore, with increasing pressure, the requirements for the quality of feed and make-up water increase significantly. The requirements for the reliability of the water regime are formulated in the form of water regime norms in the rules for the technical operation of power plants and networks (PTE) and in the rules for the installation and safe operation steam and hot water boilers.

The presence of deposits makes it necessary to clean the equipment, which is a laborious and expensive operation. Thus, water treatment is a necessary attribute of any boiler room. The purity of water and steam in individual units and parts of the boiler house paths, combined general concept the water regime of the boiler house, has a significant impact on the efficiency and reliability of its operation.

2.1 Water treatment at CHP

One of the most important issues in the energy sector has been and remains water treatment at thermal power plants. For energy companies, water is the main source of their work, and therefore very high requirements are placed on its content. Since Russia is a country with a cold climate, constant severe frosts, the operation of a thermal power plant is what people's lives depend on. The quality of the water supplied to the heat and power plant greatly affects its operation. Hard water results in a very serious problem for steam and gas boilers, as well as steam turbines of thermal power plants, which provide the city with heat and hot water. In order to clearly understand how and what exactly hard water negatively affects, it would not hurt to first understand what a CHP is? And with what it "eat"? So, a CHPP - a heat and power plant - is a kind of thermal power plant that not only provides heat to the city, but also supplies hot water to our homes and enterprises. Such a power plant is designed as a condensing power plant, but differs from it in that it can take part of the thermal steam after it has given up its energy.

Steam turbines are different. Depending on the type of turbine, steam with different indicators is selected. Turbines in the power plant allow you to adjust the amount of steam taken. The steam that has been extracted is condensed in the network heater or heaters. All energy from it is transferred to network water. Water, in turn, goes to peak water heating boiler houses and heat points. If the steam extraction paths are blocked at the CHPP, it becomes a conventional IES. Thus, the heat and power plant can operate according to two different load schedules:

thermal graph - direct proportional dependence of the electrical load on the thermal;

electrical graph - there is either no heat load at all, or the electrical load does not depend on it. The advantage of CHP is that it combines both heat and electricity. Unlike IES, the remaining heat does not disappear, but is used for heating. As a result, the efficiency of the power plant increases. For water treatment at CHPPs, it is 80 percent versus 30 percent for IES. True, this does not speak of the efficiency of the heat and power plant. Here in the price there are other indicators - the specific generation of electricity and the efficiency of the cycle. The peculiarities of the location of the CHP should include the fact that it should be built within the city. The fact is that the transfer of heat over distances is impractical and impossible. Therefore, water treatment at CHPPs is always built near consumers of electricity and heat. What is the water treatment equipment for CHP? These are turbines and boilers. Boilers produce steam for turbines, turbines produce electricity from steam energy. The turbogenerator includes a steam turbine and a synchronous generator. Steam in turbines is obtained by using fuel oil and gas. These substances heat the water in the boiler. The pressurized steam turns the turbine and the output is electricity. Waste steam is supplied to homes in the form of domestic hot water. Therefore, the exhaust steam must have certain properties. Hard water with a lot of impurities will not allow you to get high-quality steam, which, moreover, can then be supplied to people for use in everyday life. If the steam is not sent to supply hot water, then it is immediately cooled in the thermal power plant in cooling towers. If you have ever seen huge pipes at thermal stations and how smoke pours from them, then these are cooling towers, and smoke is not smoke at all, but the steam that rises from them when condensation and cooling occurs. How does water treatment work on fuel cells? The most affected by hard water is the turbine and, of course, boilers that convert water into steam. The main task of any thermal power plant is to get clean water in the boiler. Why is hard water so bad? What are its consequences and why do they cost us so much? Hard water differs from ordinary water by its high content of calcium and magnesium salts. It is these salts that, under the influence of temperature, settle on the heating element and the walls of household appliances. The same applies to steam boilers. Scale forms at the heating point and the boiling point along the edges of the boiler itself. Descaling in the heat exchanger in this case is difficult, because. scale builds up on huge equipment, inside pipes, all kinds of sensors, automation systems. Flushing the boiler from scale on such equipment is a whole multi-stage system, which can even be carried out when disassembling the equipment. But this is in the case of a high density of scale and its large deposits. The usual remedy for scale in such conditions, of course, will not help. If we talk about the consequences of hard water for everyday life, then this is the impact on human health and the rise in the cost of using household appliances. In addition, hard water is very bad in contact with detergents. You will use 60 percent more powder, soap. Costs will grow by leaps and bounds. Water softening was therefore invented to neutralize hard water, you put one water softener in your apartment and forget that there is a descaling agent, a descaling agent.

Scale is also characterized by poor thermal conductivity. This lack of it is the main cause of breakdowns of expensive household appliances. A thermal element covered with scale simply burns out, trying to give off heat to the water. Plus, due to the poor solubility of detergents, the washing machine must be additionally turned on for rinsing. These are the costs of water and electricity. In any case, water softening is the surest and most cost-effective way to prevent scale formation. Now imagine what is water treatment at a thermal power plant on an industrial scale? There, the descaler is used by the gallon. Flushing the boiler from scale is carried out periodically. It happens regularly and repair. To make descaling more painless, water treatment is needed. It will help prevent the formation of scale, protect both pipes and equipment. With it, hard water will not exert its destructive effect on such an alarming scale. If we talk about industry and energy, then most of all hard water brings trouble to thermal power plants and boiler houses. That is, in those areas where there is direct water treatment and heating of water and the movement of this warm water through water supply pipes. Water softening is as necessary here as air. But since water treatment at a thermal power plant is work with huge volumes of water, water treatment must be carefully calculated and thought out, taking into account all sorts of nuances. From the analysis of the chemical composition of water and the location of a particular water softener. In CHP, water treatment is not only a water softener, it is also equipment maintenance after. After all, descaling will still have to be done in this production process, with a certain frequency. More than one descaler is used here. It can be formic acid, and citric, and sulfuric. In various concentrations, always in the form of a solution. And one or another acid solution is used, depending on what components the boiler, pipes, controller and sensors are made of. So, which energy facilities need water treatment? These are boiler stations, boilers, this is also part of the CHPP, water heating installations, pipelines. Pipelines remain the weakest points, including CHPs. Scale accumulating here can also lead to depletion of pipes and their rupture. When the scale is not removed in time, it simply does not allow water to pass through the pipes normally and overheats them. Along with scale, the second problem of equipment in CHP is corrosion. It also cannot be left to chance. What can lead to a thick layer of scale in the pipes that supply water to the CHP? This is a difficult question, but we will answer it now knowing what water treatment at a CHP is. Since scale is an excellent heat insulator, the heat consumption increases sharply, while the heat transfer, on the contrary, decreases. The efficiency of boiler equipment drops significantly, and as a result, all this can lead to rupture of pipes and explosion of the boiler.

Water treatment at a thermal power plant is something that cannot be saved on. If in everyday life, you still think whether to buy a water softener or choose a descaler, then such bargaining is unacceptable for thermal equipment. At thermal power plants, every penny is counted, so descaling in the absence of a softening system will cost much more. And the safety of devices, their durability and reliable operation also play a role. Descaled equipment, pipes, boilers work 20-40 percent more efficiently than equipment that has not been cleaned or works without a softening system. The main feature of water treatment at thermal power plants is that it requires deeply demineralized water. To do this, you need to use precise automated equipment. In such production, reverse osmosis and nanofiltration, as well as electrodeionization, are most often used. What stages does water treatment in the energy sector include, including at a heat and power plant? The first stage includes mechanical cleaning from all kinds of impurities. At this stage, all suspended impurities are removed from the water, up to sand and microscopic rust particles, etc. This is the so-called coarse cleaning. After it, the water comes out clean for the human eye. Only dissolved hardness salts, ferrous compounds, bacteria and viruses, and liquid gases remain in it.

When developing a water treatment system, it is necessary to take into account such a nuance as the source of water supply. Is it tap water from public water systems or is it water from a primary source? The difference in water treatment is that the water from the water supply systems has already passed the primary treatment. Only hardness salts should be removed from it, and deferrized if necessary. Water from primary sources is absolutely untreated water. That is, we are dealing with a whole bouquet. Here it is imperative to carry out a chemical analysis of water in order to understand what impurities we are dealing with and what filters to install to soften the water and in what sequence. After rough cleaning, the next stage in the system is called ion-exchange demineralization. An ion exchange filter is installed here. Works on the basis of ion-exchange processes. The main element is an ion exchange resin, which includes sodium. It forms weak bonds with resin. As soon as hard water at a thermal power plant enters such a softener, the hardness salts instantly knock sodium out of the structure and firmly take its place. Restoring such a filter is very simple. The resin cartridge is moved to the recovery tank, where the saturated brine is located. Sodium takes its place again, and hardness salts are washed into the drain. The next step is to obtain water with desired characteristics. Here, a water treatment plant is used at a thermal power plant. Its main advantage is the receipt of 100% pure water, with the specified indicators of alkalinity, acidity, mineralization level. If the company needs industrial water, then the reverse osmosis plant was created just for such cases.

Nanofiltration is essentially the same reverse osmosis, only low-pressure. Therefore, the principle of operation is the same, only the water pressure is less. The next stage is the elimination of gases dissolved in it from the water. Since CHP plants need clean steam without impurities, it is very important to remove oxygen, hydrogen and carbon dioxide dissolved in it from the water. The elimination of impurities of liquid gases in water is called decarbonation and deaeration. After this stage, the water is ready for supply to the boilers. Steam is obtained at exactly the concentration and temperature that is needed.

As can be seen from all of the above, water treatment in a CHP is one of the most important components of the production process. Without clean water, there will be no high-quality good steam, which means there will be no electricity in the right amount. Therefore, water treatment in thermal power plants should be dealt with tightly, trust this service exclusively to professionals. A properly designed water treatment system is a guarantee of long-term equipment service and quality energy supply services.

2.2 Chemical water treatment

Majority modern enterprises use wastewater treatment plants to filter wastewater for subsequent use. Due to the presence in them of a large number of harmful substances - the remnants of technogenic production, simple mechanical purification is not enough. For this reason, for complete chemical water purification, technologies and installations are used that purify the liquid using chemical reagents. Proper use of such methods allows you to achieve very high results and eliminate pollution of any type. Depending on the data of the chemical and biological analysis of the liquid, the appropriate types of chemical, biochemical substances are used for water purification, which maximally meet all the requirements.

Using the obtained data on the composition of H2O, scientists determine in the laboratory what chemical reactions occur during water purification with a particular concentration of reagents. Since the substance used as a reagent is active in this process, in order to avoid its overdose, the proportions proposed by specialists should be strictly observed. In some cases, the use of such additives is impossible because the damage from them will be much greater than the benefits. In such situations, biological active substances, capable of oxidizing almost all contaminants without harming the environment. Before using them, it will not be superfluous to find out in more detail what analyzes are performed during aerobic biochemical water treatment. One of the most common studies is biochemical oxygen demand, which indicates how much O2 is enough for microorganisms to normal functioning and oxidation of harmful substances. In addition to this indicator, the chemical and biological analysis of the liquid is also taken into account.

Often in the drains you can find chromium - a toxic substance that causes allergic reactions and is very dangerous for the human body. Its neutralization is also important, as well as desalination, deferrization of H2O. To do this, it is necessary to carry out chemical purification of water from chromium by electrocoagulation. The liquid is subjected to electrophoresis, as a result of which the chromium molecule is divided into anions and cations. Aluminum and iron hydroxides, which have a high sorption capacity, attract them, forming an insoluble flocculent precipitate. The advantages of this method are the absence of reagents acting as salts.

Chemical purification of water from iron and calcium

One of the most common contaminants is iron oxide, which is characterized by a specific color and metallic taste. In the case when its amount is small, oxygen can be used as a reagent. Often in this way water is purified from a well containing iron oxide. The essence of this method is that with the help of the H2O compressor, O2 is saturated. For the successful flow of the reaction between iron and oxygen, a catalyst, magnesium, is used. The result of the reaction is the production of ferric iron, which is easily retained by mesh filters.

In cases where it is necessary to perform iron removal, softening, neutralization and chemical purification of rusty water in a well, stronger reagents are used. These include sodium hypochlorite, which oxidizes almost all salts, metals and organic substances. In the event that the liquid will not be further involved in production, and its filtration is necessary to return to natural environment, it is worth using more gentle methods. Deserves special attention industrial cleaning CHP water with chemical reagents from calcium, protecting pipes from the formation of limescale. Even a small layer of scale on the pipes contributes to a decrease in the heat transfer coefficient and an increase in fuel consumption. To solve this problem, the liming method can be used, when a solution of slaked lime with a pH level of not more than 10 is added to the liquid. As a result, the following example of a chemical water purification reaction can be observed:

Ca(HCO3)2 + Ca(OH)2 = 2CaCO3 + 2Н2O Mg(HCO3)2 + 2Ca(OH)2 = Mg(OH)2 + 2СaCO3 + 2Н2O.

As a result, insoluble salts, which are then removed from the reservoir. It is very important that the reactions of the chemical water treatment system, as well as the control of temperature and pressure, are carried out constantly. Otherwise, there may be difficulties in the disposal of sludge, an increase in the turbidity of the liquid.

The choice of reagents for the chemical treatment of industrial water largely depends on the nature of the pollution, as well as on the financial capabilities of the enterprise. Chemical water treatment is combined with the efforts of many organizations using sodium hypochlorite, which is explained by its high efficiency and low cost. According to the results of filtration, it can compete with the ozonation method, which is absolutely harmless to humans, but its cost will be much higher. Many plants use boiler plants that require thorough filtration of H2O prior to use. This need is due to protection against the formation of limescale and corrosion. Chemical water treatment of a boiler plant is carried out by means of electrochemical oxidation or by adding a special anti-scale solution to the liquid. The first method is safer, since it does not use reagents, and the removal of salts occurs due to the action of a magnetic field on them. The second method is not used so often and is used for prevention.

REFERENCES

1. Gitelman L.D., Ratnikov B.E. Energy business. - M.: Delo, 2006. - 600 p.

2. Fundamentals of energy saving: Proc. allowance / M.V. Samoilov, V.V. Panevchik, A.N. Kovalev. 2nd ed., stereotype. - Minsk: BSEU, 2002. - 198 p.

3. Standardization of energy consumption - the basis of energy saving / P.P. Bezrukov, E.V. Pashkov, Yu.A. Tsererin, M.B. Plushevsky //Standards and quality, 1993.

4. I.Kh.Ganev. Physics and calculation of the reactor. Tutorial for universities. M, 1992, Energoatomizdat.

5. Ryzhkin V. Ya., Thermal power stations, M., 1976.

Hosted on Allbest.ru

...