Water treatment in air humidification systems. Air humidification in clean rooms Humidification systems and air humidity standards for clean rooms

High precision of maintaining air humidity, in conditions of maximum hygiene - throughout the entire humidification process.

High precision control of air humidity and hygiene.

Rooms that have been assigned a cleanliness class require an impeccable microclimate, with precise control of temperature and humidity conditions. It is possible to achieve high levels of hygiene with the use of steam humidifiers, as well as with adiabatic air humidifiers. For the first (isothermal systems), water quality will play a less significant role for process hygiene, it is more likely to ensure the reliability of the steam cylinder and the resource of heating elements. For adiabatic systems, water quality is the main element on which maximum hygiene will depend.

Humidification systems and air humidity standards for clean rooms.

30-50% RH. Pharmaceuticals - production of drugs, drugs.

40-50% RH. Electronics - production or server rooms (data centers).

40-60% RH. Medicine - diagnostic centers, hospitals.

40-90 RH%. Laboratories - research, pilot production.

Today, a clean room can be seen not only in a medical institution or laboratory. The premises, which are assigned standards and cleanliness classes, are in almost every office in the form of a server room or in the production of electronic components, in industry or agriculture. Hygiene classes and cleanliness standards may vary with respect to airborne particulate matter, aerosols or bacteria. High hygiene requirements are also applied to humidification systems, where the first, priority requirement will be the requirement for the quality of the water with which the humidification unit will work.

Sterile humidification systems: operate in high hygiene mode, use purified water and control humidity with an accuracy of 1% RH.

The second requirement would be; the process of water vapor preparation itself and the method of their delivery into the air of the clean room The path from preparing water vapor to saturating the air mass with it should be the shortest and without stagnant zones. Water must not stagnate in the duct or inside the humidification unit, as this can cause the growth of mold and mildew spores. The water must be purified or completely demineralized.

Ask a Question.

In order not to be mistaken and choose the best air humidifier for an apartment or for a children's room, you need to know about the advantages and disadvantages of different types of humidifiers.

Ultrasonic humidifiers

The main problem that the owner of such a device may face is the formation of white plaque. Output - use distilled or purified water (reverse osmosis filter).

Advanced models are equipped with replaceable filters. However, sometimes they do not help either. If the water hardness in the tap is excessive (value higher than 21 dH), it is better to either abandon ultrasonic devices in favor of steam or traditional humidification, or use only distilled water, which can be bought quite inexpensively at a car dealer.

You can find out what kind of water you have at the water utility or use aquarium test strips.

Steam humidifiers

The most effective in terms of increasing humidity (almost up to 100%), but:

Control is required. Waterlogging (above 65-70%) is good for plants, but not for people and furniture. To help a hygrostat or weather station;
Hot steam. At the exit, it is already cooling down, but it can be dangerous for children. But the humidifier can be used as an inhaler;
Increased energy consumption. Evaporates water like an electric kettle.

Air washers with natural humidification

They are the most economical and have an air purification function. But waiting for a quick effect and creating high humidity (like in steam rooms) is not worth it. As well as superfine cleansing. But no plaque and waterlogging.

A little about the functions:

Built-in hygrostat

It should be understood that its readings are approximate and reflect the air humidity in the immediate vicinity of the humidifier. Would you like to be more precise for the whole room? Then you need a separate device.

Ionizer

There is no need to wait for some tangible effect. This is not a Chizhevsky chandelier, it is small and simple little dilutes a large number of positive ions with negative ones for more comfortable breathing.

Choose the humidifier that works best for your conditions, and then your purchase will be a success!

Humidification is one of the most complex and knowledge-intensive processes in ventilation and air conditioning. , determined by a number of fundamental documents of a regulatory and reference nature.

Successful engineering and technical implementation of air humidification systems requires the correct choice of the used methods and means of generating steam, compliance with rather strict requirements for its distribution inside the serviced room, or inside the supply part of the ventilation system, as well as the correct organization of the drainage of excess moisture.

Important from a practical point of view points accompanying the operation of the humidifier

Of particular importance is the use of an appropriate quality feed water ... The requirements for this are fundamentally different for humidifiers, the principle of operation and design of which are very diverse. Unfortunately, this issue has not yet found adequate coverage in the literature, which in a number of cases leads to operational errors and premature failure of expensive hardware.

Notable publications mostly refer to water treatment in heating systems and hot water supply of buildings, which differs significantly from water treatment in air humidification systems. This article is an attempt to clarify the essence of the requirements for the quality of feed water for the main types of humidifiers by analyzing the physicochemical features of the behavior of substances of varying degrees of solubility during the transition of water to steam, implemented in one way or another. The presented materials are quite general in nature, covering almost all known methods of air humidification. However, based on the author's personal experience, the considered specific designs of the units are limited to the nomenclature supplied by CAREL, which includes air humidifiers of various types in a wide range of operating principles used.

There are two main methods of air humidification for practical application: isothermal and adiabatic.

Isothermal humidification occurs at a constant temperature (∆t \u003d 0), i.e. with an increase in the relative humidity of the air, its temperature remains unchanged. Saturated steam enters the air directly. The phase transition of water from a liquid to a vapor state is carried out by an external heat source. The following types of isothermal air humidifiers are distinguished, depending on the way the external heat is realized:

with submersible electrodes (HomeSteam, HumiSteam);
with electric heating elements (HeaterSteam);
 gas humidifiers (GaSteam).

Adiabatic humidificationOnly by the content of harmful substances in drinking water 724 indicators are normalized ... General requirements for the development of methods for their determination are regulated by GOST 8.556-91. From the point of view of water use in air humidification systems, not all of the above indicators are of significant importance.

The most important are only ten indicators, detailed below:

Figure: 1

Total dissolved solids in water(Total Dissolved Solids, TDS)

The amount of substances dissolved in water depends on their physicochemical properties, the mineral composition of the soils through which they infiltrate, temperature, the time of contact with minerals and the pH of the infiltration medium. TDS is measured in mg / L, which is equivalent to one part per million (ppm) by weight. In nature, the TDS of water ranges from tens to 35,000 mg / l, which corresponds to the saltiest seawater. According to the current sanitary and hygienic requirements, drinking water must contain no more than 2000 mg / l of dissolved substances. In fig. 1, on a logarithmic scale, the solubility of a number of chemicals (electrolytes) most commonly found in water under natural conditions is presented as a function of temperature. Noteworthy is the fact that, in contrast to most salts (chlorides, sulfates, sodium carbonate) present in water, two of them (calcium carbonate CaCO3 and magnesium hydroxide Mg (OH) 2) have relatively low solubility. As a result, these chemical compounds form the bulk of the solid residue. Another characteristic feature concerns calcium sulfate (CaSO4), the solubility of which, unlike most other salts, decreases with increasing water temperature.

Total hardness (TH)

The total hardness of water is determined by the amount of calcium and magnesium salts dissolved in it, and is divided into the following two parts:

 constant (non-carbonate) hardness, determined by the content of calcium and magnesium sulfates and chlorides that remain dissolved in water at elevated temperatures;
 variable (carbonate) hardness, determined by the content of calcium and magnesium bicarbonates, which, at a certain temperature and / or pressure, participate in the following chemical processes that play a key role in the formation of a solid residue.

Сa (HCO3) 2 ↔CaCO3 + H2O + CO2, (1) Mg (HCO3) 2 ↔Mg (OH) 2 + 2 CO2.

With a decrease in the content of dissolved carbon dioxide, the chemical balance of these processes shifts to the right, leading to the formation of poorly soluble calcium carbonate and magnesium hydroxide from calcium and magnesium bicarbonates, which precipitate from the water solution with the formation of a solid residue. The intensity of the considered processes also depends on the pH of the water, temperature, pressure and some other factors. It should be borne in mind that the solubility of carbon dioxide sharply decreases with an increase in temperature, as a result of which, when water is heated, a shift in the balance of processes to the right is accompanied by the formation, as indicated above, of a solid residue. The concentration of carbon dioxide also decreases with decreasing pressure, which, for example, due to the aforementioned shift of the considered processes (1) to the right, causes the formation of solid deposits in the mouths of the nozzles of spray-type air humidifiers (atomizers). Moreover, the higher the velocity in the nozzle and, accordingly, according to Bernoulli's law, the deeper the rarefaction, the more intense the formation of solid deposits. This is especially true for atomizers without the use of compressed air (HumiFog), which are characterized by a maximum speed at the mouth of a nozzle with a diameter of no more than 0.2 mm. Finally, the higher the pH of the water (more alkaline), the lower the solubility of the calcium carbonate and the greater the solid residue formed. Due to the predominant role of CaCO3 in the formation of the solid residue, the measure of water hardness is determined by the content of Ca (ion) or its chemical compounds. The existing variety of units of measurement of stiffness are summarized in table. 1. In the United States, the following classification of water hardness is adopted for domestic use:

0.1-0.5 mEq / l - almost soft water;
0.5-1.0 mg-eq / l - soft water;
1.0-2.0 mg-eq / l - water of low hardness;
2.0-3.0 meq / l - hard water;
3.0 mEq / l - very hard water. In Europe, water hardness is classified as follows:
TH 4 ° fH (0.8 mg-eq / l) - very soft water;
TH \u003d 4-8 ° fH (0.8-1.6 meq / l) - soft water;
TH \u003d 8-12 ° fH (1.6-2.4 mg-eq / l) - medium hard water;
TH \u003d 12-18 ° fH (2.4-3.6 mEq / l) - practically hard water;
TH \u003d 18-30 ° fH (3.6-6.0 meq / l) - hard water;
TH 30 ° fH (6.0 mg-eq / l) - very hard water.

Domestic water hardness standards are characterized by significantly different values. According to the sanitary rules and norms of SanPiN 2.1.4.559-96 "Drinking water. Hygienic requirements for water quality in centralized drinking water supply systems. Quality control" (clause 4.4.1), the maximum permissible water hardness is 7 mg-eq / l. At the same time, the specified value can be increased to 10 mg-eq / l by order of the chief state sanitary doctor in the relevant area for a specific water supply system based on the results of an assessment of the sanitary and epidemiological situation in the settlement and the applied water treatment technology. According to SanPiN 2.1.4.1116-02 "Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control" (clause 4.7) the standard of physiological usefulness of drinking water in terms of hardness should be in the range of 1.5-7 mg-eq / l. At the same time, the quality standard for bottled waters of the first category is characterized by a hardness value of 7 mg-eq / l and the highest category - 1.5-7 mg-eq / l. According to GOST 2874-82 "Drinking water. Hygienic requirements and quality control" (clause 1.5.2) water hardness should not exceed 7 mg-eq / l. At the same time, for water pipelines supplying water without special treatment, in agreement with the authorities of the sanitary and epidemiological service, water hardness up to 10 mg-eq / l is allowed. Thus, it can be stated that in Russia it is allowed to use extremely hard water, which must be taken into account when operating humidifiers of all types.

This is especially true humidifiers of adiabatic type , unconditionally requiring appropriate water treatment.

With regard to isothermal (steam) humidifiers, it should be borne in mind that a certain degree of water hardness is a positive factor contributing to the passivation of metal surfaces (zinc, carbon steel) due to the formed protective film, which helps to inhibit the corrosion that develops under the action of the chlorides present. In this regard, for isothermal electrode-type humidifiers, in some cases, limit values \u200b\u200bare set not only for the maximum, but also for the minimum values \u200b\u200bof the hardness of the water used. It should be noted that in the territory of Russia the water used differs significantly in terms of hardness, often exceeding the above standards. For example:

 the highest water hardness (up to 20-30 meq / l) is typical for Kalmykia, southern regions of Russia and the Caucasus;
 in the underground waters of the Central region (including the Moscow region) water hardness ranges from 3 to 10 mg-eq / l;
 in the northern regions of Russia, water hardness is low: within the range from 0.5 to 2 mg-eq / l;
 water hardness in St. Petersburg does not exceed 1 mg-eq / l;
 the hardness of rain and melt water ranges from 0.5 to 0.8 mg-eq / l;
Moscow water has a hardness of 2-3 meq / l.

Dry residue at 180 ° С(Dry residue at 180 ° C, R180)
This indicator quantitatively characterizes dry residue after complete evaporation of water and heating to 180 ° С , differing from the total amount of dissolved solids (TDS) in the contribution that dissociating, volatilizing and absorbing chemical compounds make. These are, for example, CO2, which is present in bicarbonates, and H2O, which is contained in hydrated salt molecules. The difference (TDS - R180) is proportional to the bicarbonate content of the water used. In drinking water, R180 values \u200b\u200bare recommended, not exceeding 1500 mg / l.

Figure: 2

Natural water sources are classified as follows:

R180 200 mg / l - low mineralization;
R180 200-1000 mg / l - average mineralization;
R180 1000 mg / l - high mineralization

Specific conductivity at 20 ° С (Specific conductivity at 20 ° C, σ20)
Specific conductivity of water characterizes the resistance to the flowing electric current , being dependent on the content of dissolved electrolytes in it, which are mainly inorganic salts in natural water. The unit of measure for conductivity is μS / cm (μS / cm). The specific conductivity of pure water is extremely low (about 0.05 μS / cm at 20 ° C), increasing significantly depending on the concentration of dissolved salts. It should be noted that the conductivity is strongly temperature dependent, as shown in Fig. 2. Consequently, the specific conductivity is indicated at a standard temperature of 20 ° C (less often 25 ° C) and is indicated by the symbol σ20. If σ20 is known, then the values \u200b\u200bof σt ° C corresponding to the temperature t, expressed in ° С, are determined by the formula: σt ° Cσ20 \u003d 1 + α20 t - 20, (2) where: α20 is the temperature coefficient ( α20 ≈0.025). Knowing σ20, the values \u200b\u200bof TDS and R180 can be roughly estimated using empirical formulas: TDS ≈0.93 σ20, R180 ≈0.65 σ20. (3) It should be noted that if the TDS estimate in this way has a small error, then the R180 estimate has a much lower accuracy and depends significantly on the content of bicarbonates in relation to other electrolytes.

Figure: 3

Acidity and alkalinity(Acidity and alkalinity, pH)

Acidity is determined by H + ions, which are extremely corrosive towards metals, especially zinc and carbon steel. Neutral water has a pH value of 7. At lower values, acidic properties appear, and, conversely, at higher values, alkaline ones. The acidic environment dissolves the protective oxide film, which contributes to the development of corrosion. As shown in fig. 3, at pH values \u200b\u200bbelow 6.5, the corrosion rate increases significantly, while in an alkaline medium at pH above 12, the corrosion rate is also slightly increased. Corrosion activity in an acidic environment increases with temperature. It should be borne in mind that at pH< 7 (кислотная среда) латунный сплав теряет цинк, в результате чего образуются поры и латунь становится ломкой. Интенсивность данного вида коррозии зависит от процентного содержания цинка. Алюминий ведет себя иным образом, поскольку на его поверхности образуется защитная пленка, сохраняющая устойчивость при значениях pH от 4 до 8,5.

Chlorides(Chlorides, Cl-)

Chloride ions present in water cause corrosion of metals, especially zinc and carbon steel, interacting with metal atoms after the destruction of the surface protective film formed by a mixture of oxides, hydroxides and other alkaline salts formed due to the presence of dissolved CO2 in water and the presence of impurities in the atmospheric air ... The presence of electromagnetic fields, typical for isothermal (steam) humidifiers with immersed electrodes, enhances the above effect. Chlorides are especially active with insufficient water hardness. It was previously indicated that the presence of calcium and magnesium ions has a passivating effect, inhibiting corrosion, especially at elevated temperatures. In fig. 4 schematically shows the inhibitory effect of temporary hardness in terms of the corrosive effect of chlorides on zinc. In addition, it should be noted that a significant amount of chlorides intensifies foaming, which negatively affects the operation of isothermal humidifiers of all types (with immersed electrodes, with electric heating elements, gas).

Figure: 4

Iron + Manganese(Iron + Manganese, Fe + Mn)

The presence of these elements causes the formation of suspended suspension, surface deposits and / or secondary corrosion, which implies the need to remove them, especially when working with adiabatic humidifiers using reverse osmosis water treatment, since otherwise rapid membrane fouling occurs.

Silica(Silica, SiO2)

Silicon dioxide (silica) can be contained in water in a colloidal or partially dissolved state. The amount of SiO2 can vary from trace amounts to tens of mg / L. Usually the amount of SiO2 is increased in soft water and in the presence of an alkaline medium (pH 7). The presence of SiO2 has a particularly negative effect on the operation of isothermal humidifiers due to the formation of a hard, difficult to remove sludge consisting of silicon dioxide or formed calcium silicate. Residual chlorine (Cl-) The presence of residual chlorine in the water is usually due to the disinfection of drinking water and is limited to minimum values \u200b\u200bfor all types of humidifiers in order to avoid the appearance of strong odors entering the humidified rooms along with moisture vapor. In addition, free chlorine, through the formation of chlorides, leads to metal corrosion. Calcium sulfate (Calcium sulphate, CaSO4) Calcium sulfate, present in natural water, has a low degree of solubility, and therefore it is prone to sediment formation.
Calcium sulfate is present in two stable forms:

 anhydrous calcium sulfate, called anhydrite;
 two-water calcium sulfate CaSO4 2H2O, known as chalk, which at temperatures exceeding 97.3 ° C dehydrates to form CaSO4 1 / 2H2O (hemihydrate).

Figure: five

As shown in fig. 5, at temperatures below 42 ° C., the dihydrate sulfate has a reduced solubility compared to anhydrous calcium sulfate.

In isothermal humidifiers at water temperature corresponding to the boiling point, calcium sulfate can be present in the following forms:

Hemihydrate, which at 100 ° C has a solubility of about 1650 ppm, which corresponds to about 1500 ppm in terms of calcium sulfate anhydrite;
Anhydrite, which has a solubility of about 600 ppm at 100 ° C.

Excess calcium sulfate precipitates , forming a pasty mass, which under certain conditions tends to harden. A summary of the limit values \u200b\u200bof the feed water parameters discussed above for various types of humidifiers is presented in the following series of tables. It should be borne in mind that isothermal humidifiers with immersion electrodes can be equipped with cylinders designed to operate on standard water and water with a reduced salt content. Electric heater type isothermal humidifiers may or may not have a Teflon-coated heating element.

Isothermal (steam) humidifiers with immersion electrodes The humidifier is connected to a water supply network with the following parameters:

pressure from 0.1 to 0.8 MPa (1-8 bar), temperature from 1 to 40 ° C, flow rate not lower than 0.6 l / min (nominal value for the supply solenoid valve);
hardness no more than 40 ° fH (which corresponds to 400 mg / l CaCO3), specific conductivity 125-1250 μS / cm;
 lack of organic compounds;
the parameters of the feed water must be within the specified limits (Table 2)

Not recommended:
1. Use of spring water, industrial water or water from refrigeration circuits, as well as potentially chemically or bacterially contaminated water;
2. Adding disinfectants or anti-corrosion additives to the water that are potentially harmful.

Humidifiers with electric heating elements The feed water used by the humidifier must not have an unpleasant odor, corrosive agents or excessive amounts of mineral salts. The humidifier can operate on tap water or demineralized water with the following characteristics (Table 3).

Not recommended:
1. Use of spring water, service water, water from cooling towers, as well as water with chemical or bacteriological contamination;
2. Adding disinfectant and anticorrosive additives to the water. humidifying the air with such water can cause allergic reactions in others.

Gas humidifiers
Gas humidifiers can operate on water with the following characteristics (Table 4). In order to reduce the frequency of maintenance of the steam cylinder and heat exchanger, namely cleaning, the use of demineralised water is recommended.

Adiabatic (spray) humidifiers (atomizers), compressed air humidifiers adiabatic type MC can operate both on tap water and on demineralized water, which does not contain bacteria and salts found in ordinary water. This makes it possible to use this type of humidifier in hospitals, pharmacies, operating rooms, laboratories and other special rooms where sterility is required.

1 Adiabatic (spray) humidifiers (atomizers) working on high pressure water
HumiFog humidifiers can only be operated with demineralized water (table 5). For this purpose, as a rule, water treatment is used, corresponding to the following parameters. The first three parameters are of primary importance and must be respected under all conditions. If the specific conductivity of water is below 30 μS / cm, it is recommended to use a pump unit made entirely of stainless steel.

2 Adiabatic centrifugal (disc) humidifiers
DS direct humidifiers do not use water as such. With their help, the existing steam is supplied to the humidification section of central air conditioners or to the supply air ducts. As it is obvious from consideration of the above information, in some cases it is desirable, and in some of them it is mandatory, appropriate water treatment by replacing, transforming or removing certain chemical elements or compounds dissolved in the feed water. This prevents premature failure of the used air humidifiers, extends the service life of consumables and materials such as steam cylinders, and reduces the amount of work required for periodic maintenance. The main tasks of water treatment are to reduce to a certain degree corrosive activity and the formation of salt deposits in the form of scale, sludge and solid sediments. The nature and degree of water treatment depends on the ratio of the actual parameters of the available water and those required for each of the humidifiers discussed above. Let us consider sequentially the main methods of water treatment used.

Water softening

Figure: 6

This method reduces the hardness of the water without changing the amount of electrolyte dissolved in the water. In this case, the replacement of the ions responsible for the excess rigidity is carried out. In particular, calcium (Ca) and magnesium (Mg) ions are replaced by sodium (Na) ions, which prevents the formation of lime deposits when the water is heated, because, unlike calcium and magnesium carbonates, which form a variable component of hardness, sodium carbonate remains dissolved in water when elevated temperature. Usually the water softening process is carried out using ion exchange resins. When using sodium ion exchange resins (ReNa), chemical reactions are as follows, constant hardness:

2 ReNa + CaSO4 → Re2Ca + Na2SO4, (4) variable hardness:
2 ReNa + Ca (HCO3) 2 → Re2Ca + NaHCO3. (5)

Thus, the ions responsible for excessive hardness (in this case Ca ++) and dissolution of Na + ions are fixed on the ion-exchange resins. Since ion exchange resins are gradually saturated with calcium and magnesium ions, their effectiveness decreases over time and regeneration is required, which is carried out by backwashing with a dilute sodium chloride solution (table salt):
ReCa + 2 NaCl → ReNa2 + CaCl2. (6)
The formed calcium or magnesium chlorides are soluble and are carried away with the rinsing water. At the same time, it should be borne in mind that softened water has increased chemical corrosivity, as well as increased specific conductivity, which intensifies the electrochemical processes taking place. In fig. 6 shows, in comparative terms, the corrosive effects of hard, softened and demineralized water. Please note that despite the patented Anti Foaming System (AFS), the use of softened water in isothermal humidifiers of all types can lead to foam formation and eventually malfunction. As a result, water softening during water treatment in air humidification systems is not so much of an independent importance as it serves as an auxiliary means of reducing the hardness of water before its demineralization, which is widely used to ensure the operation of adiabatic humidifiers.

Polyphosphate treatment
This method allows for a while to "bind" hardness salts, preventing them from falling out in the form of scale for some time. Polyphosphates have the ability to form bonds with CaCO3 crystals, keeping them in suspension and, thereby, stopping the process of their aggregation (formation of chelate bonds). However, it should be borne in mind that this mechanism is operable only at temperatures not exceeding 70-75 ° C. At higher temperatures, it has a tendency to hydrolysis and the effectiveness of the method decreases sharply. It should be borne in mind that water treatment with polyphosphates does not reduce the amount of dissolved salts, therefore, the use of such water, as in the previous case, in isothermal humidifiers can lead to foaming and, consequently, to their unstable operation.

Magnetic or electric air conditioning
Under the influence of strong magnetic fields, allotropic modification of salt crystals occurs, which are responsible for variable hardness, as a result of which the salts of scale-forming agents turn into a finely dispersed sludge, which does not deposit on surfaces and is not prone to the formation of compact forms. Similar phenomena take place when using electrical discharges, which reduce the ability of precipitated salts to aggregate. However, until now, there are no sufficiently reliable data regarding the efficiency of such devices, especially at high temperatures close to the boiling point.

Demineralization
The methods of water treatment considered above do not change the amount of chemicals dissolved in water and, therefore, do not completely solve the problems that arise. When operating isothermal humidifiers, they can reduce the amount of solid deposits formed, which is most relevant to water softening methods. Demineralization, carried out by the extraction of substances dissolved in water in one way or another, has a limited effect for isothermal humidifiers with immersed electrodes, since their principle of operation is based on the flow of electric current in a salt solution. However, for all other types of air humidifiers, demineralization is the most radical method of water treatment, especially for adiabatic air humidifiers. It can also be fully used for isothermal humidifiers with electric heating elements and gas humidifiers, when using other methods of water treatment discussed above, reducing the amount of solid deposits formed, create concomitant problems associated with an increase in the concentration of strong electrolytes during water evaporation. One of the negative aspects associated with the lack of water demineralization is the formation of a finely dispersed salt aerosol when moisture is supplied to the serviced premises. This applies to the greatest extent to enterprises in the electronics industry ("clean" rooms) and medical institutions (eye microsurgery, obstetrics and gynecology). This problem can be completely avoided by demineralization, except for the use of isothermal immersion electrode humidifiers. The degree of demineralization is usually estimated by the specific conductivity, which is approximately proportional to the total concentration of dissolved electrolytes in the following ratios (Table 7).

In nature, water with a specific conductivity of less than 80-100 μS / cm is almost never found. Ultra-high demineralization is necessary in exceptional cases (bacteriological laboratories, crystal growth chambers). In most practical applications, however, a fairly high and very high degree of demineralization. The highest degree of demineralization (up to theoretically achievable) is provided by distillation of water, incl. double and triple. However, this process is costly, both in terms of capital costs and operating costs. In this regard, the following two methods of demineralization are most widely used for water treatment with air humidification:

Reverse osmosis
In accordance with this method, water is pumped under high pressure through a semipermeable membrane with pores having a diameter of less than 0.05 μm. Most of the dissolved ions are filtered on the membrane. Depending on the membrane used and other characteristics of the filtration process carried out, 90% to 98% of the ions dissolved in the water are removed. Achieving higher demineralisation efficiency is problematic. The possibility of carrying out the reverse osmosis process completely automatically, as well as the absence of the need for the use of chemical reagents, make it especially attractive for the purposes under consideration. The process is quite economical, consuming 1-2 kWh of electricity per 1 m3 of treated water. The cost of equipment is constantly decreasing due to the increase in its production volume due to the constant expansion of the scope of use. Reverse osmosis, however, is vulnerable if the treated water is very hard and / or contains a large amount of mechanical impurities. In this regard, in order to increase the service life of the membranes used, pre-softening of the water or its polyphosphate treatment or magnetic / electric conditioning and filtration are often required.

Deionization
In accordance with this method, layers of ion exchange resins (columns of ion exchangers) are used to remove solutes, which have the ability to exchange hydrogen ions for cations and hydroxyl ions for dissolved salt anions. Cationic ion exchange resins (cation resins, polymeric acids) exchange one hydrogen ion for a cation of a solute coming into contact with the resin (eg Na ++, Ca ++, Al +++). Anionic ion exchange resins (anion exchangers, polymeric bases) exchange one hydroxyl ion (hydroxyl group) for the corresponding anion (eg Cl-). Hydrogen ions, liberated by cation exchangers, and hydroxyl groups, liberated by anion exchangers, form water molecules. Using calcium carbonate (CaCO3) as an example, chemical reactions look like this, in a cation exchanger column:

Figure: 7

2 ReH + CaCO3 → Re2Ca + H2CO3, (7) in the anionite column 2 ReH + H2CO3 → Re2CO3 + H2O. (8) As the ion exchange resins consume hydrogen ions and / or hydroxyl groups, they should be subjected to a regeneration process using the treatment of a hydrochloric (hydrochloric) acid cation exchanger column:

Re2Ca + 2 HCl → 2 ReH + CaCl2. (9) The anionite column is treated with sodium hydroxide (caustic soda): Re2CO3 + 2 NaOH →  (10) → 2 ReOH + Na2CO3. The regeneration process ends with washing, which ensures the carryover of salts formed as a result of the considered chemical reactions. In modern demineralizers, the water flow is organized "from top to bottom", which prevents the separation of the gravel layer and ensures continuous operation of the unit without deteriorating the quality of cleaning. In addition, the ion exchanger layer acts as a filter for water purification from mechanical impurities.

The efficiency of demineralization by this method is comparable to distillation. At the same time, the operating costs inherent in deionization are significantly lower compared to distillation. Theoretically, water demineralized by the considered methods (reverse osmosis, deionization) is chemically neutral (pH \u003d 7), but various substances with which it subsequently contacts are easily dissolved in it. In practice, demineralized water is slightly acidic due to the demineralization process itself. This is due to the fact that the residual amounts of ions and gas impurities lower the pH. In the case of reverse osmosis, this is due to the differential selectivity of the membranes. In the case of deionization, the indicated residual amounts are explained by depletion or disruption of the integrity of the ion exchanger columns. In the case of increased acidity, water can dissolve metal oxides, opening the way for corrosion. Carbon steel and zinc are particularly susceptible to corrosion. The typical phenomenon is, as noted earlier, the loss of zinc by the brass alloy. Water with a specific conductivity of less than 20-30 μS / cm should not come into contact with carbon steel, zinc and brass. Finally, Fig. 7 shows a diagram that interconnects the considered indicators of water quality, methods of air humidification and water treatment methods. For each humidification method, black rays determine a set of water quality indicators, the quantitative values \u200b\u200bof which must be ensured within specified limits. Colored rays determine the methods of water treatment recommended, if necessary, for each of the considered methods of air humidification. At the same time, the priorities of the recommended water treatment methods have been determined. Colored arcs also, taking into account the priorities, identified auxiliary methods of water treatment, recommended for preliminary reduction of water hardness, subject to further processing by reverse osmosis. The most critical in terms of the content of dissolved salts in water is the ultrasonic method of air humidification (HumiSonic, HSU), for which the priority is the use of distillate, or at least the use of deionization or reverse osmosis. Water treatment is also mandatory for atomizers operating on high pressure water (HumiFog, UA). In this case, the use of reverse osmosis provides satisfactory results. More expensive water treatment methods such as deionization and distillation are also possible. Other methods of air humidification allow the use of tap water without its preparation, if their quantitative values \u200b\u200bare within specified limits throughout the entire set of specific indicators of water quality. Otherwise, it is recommended to use water treatment methods in accordance with the identified priorities. As for direct-acting humidifiers (UltimateSteam, DS), they are fed with ready-made steam and in the one shown in fig. 7 schemes have no formal links with water quality indicators and water treatment methods.

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Is the amount of water vapor in the air. In everyday life, we usually remember about it only by listening to the weather forecast.

Employees and institutions have a completely different attitude to indoor air humidity. Due to the lack of moisture in the air, it is necessary to do forced humidification in clinics, industrial and food enterprises, using industrial, semi-industrial or household installations.

Air humidity is not only one of the parameters, but also mandatory, provided, a deviation from which is unacceptable.

When the air humidity drops, static electricity builds up. Electronic devices that are sensitive to their effects are easily damaged. To reduce the risk of electrostatic charges, the relative humidity of the air must be maintained at a level of at least 30%.

A decrease in humidity negatively affects the well-being of people, especially those who suffer from allergies and asthma: in winter, a significant amount of dust accumulates in the dry indoor air.

Humidity plays an important role in most technological processes. The rate of many chemical reactions depends on relative humidity. Air humidity at the level of 40-60% will exclude the development of microorganisms and the reproduction of bacteria.

Getting the right microclimate in a laboratory or clean room without a humidifier is problematic. Dry air occurs regardless of whether we want it or not:

in cold weather when the heating is turned on;
in the summer heat;
due to the peculiarities of production;
in connection with heat transfer during the operation of the equipment;
due to the hygroscopic nature of the raw material, which absorbs moisture from the air.

If it is impossible to change the weather and production technology, then you can neutralize the consequences and restore the loss of moisture with the help of air humidifiers.

Long live hydration

Air humidification creates a comfortable and healthy living environment for people, increasing labor productivity. The required amount of moisture in the atmosphere of the production room ensures a reliable flow of technological processes, the quality of finished products does not suffer, sanitary norms and rules are followed.

It is effective to use natural methods for humidifying the air - small fountains, aquariums - in small household premises. In all other cases, the problem of humidification is solved differently.

Humidification in laboratories and clean rooms is recommended using industrial or semi-industrial humidification systems. There are three main ways to moisturize:

Adiabatic.
Isothermal.
Ultrasonic.

The advantages of adiabatic humidification include low energy consumption. Simultaneously with moisturizing occurs. Systems operating on the principle of adiabatic humidification have high productivity, do not emit harmful impurities into the atmosphere, 90% of the water volume is used for its intended purpose. The air is saturated with moisture without using a source of thermal energy.

Isothermal humidifiers operate on the principle of a steam generator: water vapor is generated when water is heated and evaporated. For normal operation, purified and softened water is required. These devices are very energy-intensive: about 750 W of electricity is spent on the production of 1 kg / h of moisture. The advantages of this type of device include high performance and low noise level.

Another type of artificial humidifier, ultrasonic. The operation of the device is based on the cavitation process, the use of the energy of high-frequency vibrations of water molecules. It turns into cold steam, saturating the air with moisture as much as possible. For the device is completed. The ultrasonic humidifier consumes little energy, lowers the room temperature by 1-2 degrees, and works absolutely silently.

When choosing a humidification system, performance, energy class, environmental friendliness, technical parameters of the room in which it is installed are taken into account.

There is a humidifier, no problem

An air humidifier is a climatic device used to increase air humidity in rooms.

Proper humidification of the air is a prerequisite for the safe stay of a person in a home or industrial area. Insufficient or excessive humidity will equally have a detrimental effect on well-being and performance. There can be no talk of any technologically correct and competent production process, if the regulatory requirements of the standards for the microclimate of laboratories and clean rooms are not met.

Humidification in clean rooms by spraying microscopic, no more than 5 microns, drops of moisture in them simultaneously reduces the ambient temperature. Passing from a liquid to a gaseous state, water takes the energy of the air, cooling it.

The humidification system will create the required humidity level in clean rooms and laboratories automatically and absolutely silently. Create a comfortable, healthy microclimate at your workplace, it's easy!

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