EA039152B1 - Device for photocatalytic air purification and method for dynamic control of the degree of photocatalytic air purification therein - Google Patents

Abstract

The invention relates to the field of cleaning air and gases from organic and inorganic impurities, and can be used in everyday life, hospitals, industrial premises, etc. The invention proposes a device for photocatalytic air purification, comprising a means (6) for moving air, located in a channel (5) carriers (2) with a catalytic coating assembled in parallel with a gap (3) to form at least one photocatalytic oxidation module (1) that can be illuminated, at least from one of the sides, by at least one radiation source (4) that can operate in a continuous or pulsed mode, and each said module (1) and at least one corresponding radiation source (4) form a photocatalytic unit (7). In the photocatalytic unit (7), the continuous illumination mode is used for the radiation spectrum in the range of 200 to 400 nm, and the pulsed illumination mode is provided by xenon lamps with the radiation spectrum in the range of 200 to 1,000 nm; the photocatalytic unit (7) is made with the ability to control and maintain the temperature of the catalytic coating on the carrier (2) by means of said xenon lamps, the ratio of the cross-sectional area of the photocatalytic unit (7) in the channel (5) to the area of carriers (2) belongs to the interval 1/66-1/193, and the length of the carriers (2) are conditioned, at the design stage, by one-sided or two-sided illumination of the photocatalytic oxidation module (1) and by the carrier material (2); the device contains at least two photocatalytic units (7) that are installed in series with the possibility of independent remote control of turning them on/off. Also proposed is a method for dynamic control of the degree of photocatalytic air purification in the claimed device.

Description

The invention relates to the field of purification of air and gases from organic and inorganic impurities and can be used in everyday life, medical institutions, industrial premises, warehouses, etc.

A photocatalytic air purifier is a device for reducing volatile organic compounds in indoor air. A photocatalytic coating based on titanium dioxide is applied to the surface of the purifier carriers, which absorbs UV radiation and further increases the efficiency of disinfection and air purification due to photocatalysis. In the process of photocatalysis, titanium dioxide, absorbing ultraviolet, produces free radicals that effectively oxidize organic matter, including viruses, bacteria, other microorganisms, and, in addition, volatile organic compounds, and decompose to harmless water and carbon dioxide molecules [1]. Thus, the use of a photocatalytic air purifier is beneficial for improving indoor air quality.

Thus, a photocatalytic air purifier is known, in which the process of cleaning air and gases from organic and inorganic impurities using photocatalysis is based on the fact that the molecules of air or gas polluting compounds decompose to safe substances during reactions in the presence of a catalytic coating, for example, titanium dioxide under the action of ultraviolet radiation with an emission spectrum in the range from 200 to 400 nm. In this case, titanium dioxide, as a rule, is deposited on a metal substrate in various forms, in the phases of anatase, rutile, and their combinations [2]. It is proposed to achieve cleaning efficiency by increasing the length of carriers coated with titanium dioxide, while the calculation of the length and area of carriers is not proposed.

An air cleaner with photocatalytic oxidation is also known, containing an air moving means that creates an air flow through the channel, photocatalytic oxidation elements located in the channel, which illuminate the radiation source in the ultraviolet radiation spectrum [3].

Devices are also known that implement a purification method in which purification is used with the passage of the medium to be cleaned through several photocatalytic units of the purifier.

Also known is a method of photocatalytic gas purification [4] by oxidation using a photocatalyst based on titanium dioxide. In this case, the initial gas mixture containing oxidizable substances is saturated with hydrogen peroxide vapor. At the same time, ceramic carriers with a catalytic coating in the form of titanium dioxide and ultraviolet lamps are alternated.

The disadvantage of this solution is the lack of calculation of the dimensions of ceramic carriers and, in connection with this, the dimensions and number of lamps, and the issue of determining the number of purification units to achieve the required degree of purification has not been considered.

There is also an air purifier from gaseous impurities [5], which contains a unit built into the ventilation system, consisting of a source of ultraviolet radiation and a photocatalytic element located in the housing in the form of at least one package assembled from separate thin-walled carriers. However, no recommendations are given on the optimal choice of the geometric dimensions of the carriers and their number.

There is a method for air purification and disinfection by oxidation using a titanium dioxide-based photocatalyst and a source of ultraviolet radiation. At the same time, an aerosol cloud of titanium dioxide nanopowder is used as a catalyst, which is aerated and sprayed from a pre-filled container with combustion products of a gas generator with a charge of low-temperature solid fuel, and at least three radiation sources are used, which are evenly distributed along the periphery of the aerosol cloud [6].

At the same time, formulas are proposed for determining the rate of heterogeneously catalyzed photochemical reactions only depending on the parameters of titanium dioxide nanoparticles without correction for the frequency of purification and the achieved result.

It is also known that the dependence of the rate of photocatalytic oxidation of contaminants on titanium dioxide on temperature has a maximum, the value of which is determined by the type of pollution and the presence of water.

It is known that titanium dioxide exists in the form of several forms that differ in the type of molecular lattice. Currently, two coatings are used for the purposes of photocatalysis: in the form of rutile and anatase. Evoniklndustrials offers finely dispersed pure titanium dioxide AEROXIDE® TiO ₂ P 25 for photocatalysis, which is a combination of anatase and rutile crystal structure. The high efficiency of AEROXIDE® TiO ₂ P 25 is explained precisely by the presence of various structural modifications in the powder composition, which separates charge carriers more efficiently.

SachtlebenChemieGmbH, Germany, produces a pure anatase photocatalyst TiO ₂ Hombikat UV100 with very high photocatalytic properties, associating this with the possibility of fast interfacial electron transfer in the catalyst structure.

At the same time, the proposals from these manufacturers do not contain information on the optimization of the catalyst depending on the type of pollution.

It is also known to use pulsed xenon lamps with a wide emission spectrum from 200

- 1 039152 to 1000 nm, at which bacterial disinfection is provided by direct action without a catalyst on a biological object. Overheating and destruction of pollution occurs due to the excess of energy supply from the radiation source over the removal of thermal energy by the biological object.

However, we are not aware of any recommendations on how to control and distribute catalyst heating and the use of this type of lamp to control catalyst heating.

Since many catalytic coatings, including titanium dioxide, are semiconductors, the dependence of the quantum efficiency of oxidation on the electrical characteristics of the band gap is known, but there are no recommendations for controlling the electrical potential to control catalysis processes.

Also, there are no solutions that contribute to the active mixing of the stream of the gas medium being cleaned to activate contact with the catalyst.

The closest of the known essential features to the claimed device for photocatalytic air purification and the method of dynamic control of the degree of photocatalytic air purification in it is the above-mentioned air cleaner with photocatalytic oxidation [3]. The patent describes in detail the physical properties of the components of the cleaner, but does not make it possible to optimize the cleaning efficiency and determine the minimum sufficient dimensions of the components for the required degree of purification.

It should be noted that the prior art does not know the calculation method for controlling the catalysis process with differentiation of the variable parameters of pollution over time, i.e. dynamic regulation of parameters and moments of switching on/off cleaning units is not used. The most common is the sampling method, which takes a long time and does not predict the behavior of the system enough.

Thus, the objective of the invention is to develop a device for photocatalytic air purification and a method for dynamically controlling the degree of photocatalytic air purification in it, which would provide high efficiency of air purification with optimal dynamic control of the degree of air purification and with optimal geometric dimensions and the ratio of the sizes of the active components of the device with a catalytic coating , as well as determining the number of cleaning blocks and the number of passes during cleaning by analyzing the light fluxes and activity of the first block.

The problem is solved, and the technical results are achieved using the proposed device for photocatalytic air purification, containing an air moving means that creates an air flow through the channel, carriers located in the channel with a catalytic coating active in the radiation spectrum from infrared to ultraviolet, while the carriers are collected in parallel with a gap of at least one photocatalytic oxidation module, wherein said module is configured to illuminate at least one of the sides by at least one radiation source configured to illuminate in continuous or pulsed mode, and each photocatalytic oxidation module and at least one respective radiation source form a photocatalytic unit. At the same time, in the photocatalytic unit, the continuous illumination mode is used for the emission spectrum in the range from 200 to 400 nm, and the pulsed illumination mode is implemented by xenon lamps with an emission spectrum in the range from 200 to 1000 nm. At the same time, the photocatalytic unit is configured to control and maintain the temperature of the catalytic coating on the carrier by means of the indicated xenon lamps, the ratio of the cross-sectional area of the photocatalytic unit in the channel to the area of the carriers with the catalytic coating belongs to the interval 1/66 - 1/193, and the lengths of the carriers are determined at the stage designing one-sided or two-sided lighting of the photocatalytic oxidation module and the carrier material, contains at least two photocatalytic blocks, while the blocks are installed in series with the possibility of independent remote control of turning them on / off.

In preferred embodiments, the catalytic carrier coating is made of titanium dioxide, preferably in anatase or rutile phases.

In the most preferred forms of implementation, the photocatalytic unit is configured to control and maintain the temperature of the catalytic coating on the carrier by heating due to the radiation of a part of the spectrum of the radiation source, by changing the illumination mode.

Also, in preferred embodiments, the photocatalytic unit is configured to regulate and maintain the sign and value of the potential of the catalytic coating on the carrier by connecting to an electrical source or grounding. This speeds up oxidation reactions and increases the safety of the device, since the cleaned air with impurities can be explosive.

Preferably, the length of the carriers when the photocatalytic oxidation module is illuminated by a light source located on one side, for a stainless steel carrier is not more than 50 mm, for an aluminum carrier is not more than 145 mm, and when the photocatalytic oxidation module is illuminated by light sources located on opposite sides, for stainless steel carrier is not more than 100 mm, for aluminum carrier is not more than 290 mm.

- 2 039152

In preferred embodiments, when the photocatalytic oxidation module is illuminated by at least two radiation sources, each of the radiation sources is configured to be illuminated in continuous or pulsed mode independently of the other radiation source.

In this case, in the pulsed mode, the heating of the catalytic coating of titanium dioxide is better ensured.

Also, in the preferred embodiments, when the photocatalytic oxidation module is illuminated by at least two radiation sources, one of them is configured to illuminate in continuous mode, and the second in a pulsed mode alternately, or the radiation sources are configured to illuminate in only one mode.

In preferred forms of implementation, when cleaning air from acetone, ammonia, ethyl acetate and other substances that are easily decomposed on the catalytic coating of carriers, the ratio of the cross-sectional area of the photocatalytic oxidation module in the channel to the carrier area is selected from the range 1/66 - 1/97.

In alternative forms of implementation in the purification of air from formaldehydes, aliphatic hydrocarbons С1- _С10 , carbon monoxide, exhaust gases, cigarette smoke and other substances that are difficult to decompose on the catalytic coating of carriers, the ratio of the cross-sectional area of the photocatalytic oxidation module in the channel to the carrier area is selected from the interval 1/97 - 1/193.

Preferably, the carriers are inclined with respect to the axis of the channel. This makes it possible to exclude laminar flows of the cleaned air, as a result of which the cleaning efficiency increases.

In preferred embodiments, when there are two or more photocatalytic blocks, adjacent photocatalytic blocks are located at different angles of inclination to the channel axis, while at least part of the photocatalytic blocks can be located at an inclination angle of 0°.

In each of the implementation forms, the air flow is formed with the possibility of passing through the channel in a mode selected from the exhaust ventilation mode, the supply ventilation mode, and the recirculation mode.

The problem is solved, and the technical results are also achieved by the claimed method of dynamically controlling the degree of photocatalytic air purification in the device, including passing the stream of air to be purified sequentially through remote independent control of switching on / off individual photocatalytic units depending on the physical and chemical characteristics of the carriers and catalytic coating on carriers of photocatalytic oxidation modules, determining the number of successively installed photocatalytic units to be put into operation, and determining the moment of switching on/off each photocatalytic unit into operation. At the same time, the number of sequentially installed photocatalytic units to be put into operation in the exhaust ventilation mode and in the supply ventilation mode is determined by the degree of purification in the first photocatalytic unit, and in the recirculation mode, by the degree of purification in the first pass in the first photocatalytic unit, the number of passes of the cleaned air, and the degree of purification in the second and subsequent photocatalytic blocks and passages in these modes is determined based on the degree of purification in the first block and passage, respectively.

In the most preferred forms of implementation of the proposed method, the degree of purification in the second and subsequent photocatalytic units is determined by the following formulas:

for the mode of exhaust and supply ventilation, the total degree of purification after the second block

C12 = 2Ci - 0.01C1 ² , (1) where C is the degree of purification after the first block, %, C ₁₂ is the total degree of purification after the first and second blocks, %;

for the mode of exhaust and supply ventilation, the total degree of purification after the third block

where C ₁₂₃ - the total degree of purification after the first, second and third block,%;

for the _{recirculation mode} , the _degree of purification after the first _{block k}

K _h \u003d [(K _n x (2Ci - 0.01 C?) + K _g ) xV _r ] / V _u , (4) for the recirculation mode, the total degree of purification after the third block

K _h = [(K _n x (3Ci - 0.03C _L ² +0.0001 Cl ³ ) + K _g ) xV _r ] / V _u , (5) where in formulas (3)-(5)

K _h - residual concentration after cleaning, %, h - operating time of the recirculator, h,

- 3 039152

C1 - cleaning degree after the first block, %,

K _n - initial concentration of pollutants in the room,%,

Kg - additional emissions of pollutants from K _n , %/h,

V _r - room volume, m ³ ,

V _r = V _u xK _h /(K _n xC + K _g ), (6)

V _u - performance of the recirculator, m ³ / h,

V _u =[(K _n xCi ^((Vu/Vr)xh ' ¹⁾ + K _g ) xV _r ] / K _h . (7)

The proposed solution for calculating the length of titanium dioxide carriers in a photocatalytic purifier and choosing the ratio of the area of the channel for the passage of the air being cleaned to the total area of the carriers provides high efficiency in terms of the degree of purification / purification cost, and determining the number of blocks and passes during purification using the proposed formulas ensures the achievement of environmental standards. high efficiency air purification.

In addition to the above technical results, the implementation of the proposed device additionally provides environmental protection through a reduction in the amount of materials used for the components of the device and electricity for the cleaning process.

In the preferred forms of implementation of the proposed method, the temperature of the catalytic coating on the carrier is controlled, and the temperature is chosen according to the temperature value of the highest rate of photocatalytic oxidation of one pollution, preferably, the pollution that prevails in terms of quantity in the total composition of pollution.

Also, in the preferred forms of implementation of the proposed method, the temperature of the catalytic coating on the carrier is controlled, and the temperature is chosen according to the smallest standard deviation from the temperature value of the highest photocatalytic oxidation rates for all removed contaminants. This form of implementation of the proposed method is used, preferably, when there are several air pollutants and they are in a similar concentration.

In the preferred forms of implementation of the proposed method, the temperature of the catalytic coating on the carrier is controlled, and the temperature is chosen taking into account the values of the temperatures of the highest oxidation rates and the specific concentrations of contaminants to be removed. This form of implementation of the proposed method is used, preferably, when there are several air pollutants and their concentrations differ significantly.

In the preferred forms of implementation of the proposed method, the temperature of the catalytic coating on the carrier is controlled, and the temperature is chosen to be variable along the length of the carrier in the photocatalytic oxidation module. The temperature of the catalytic coating, which is variable along the length of the carrier, makes it possible to ensure that the temperatures of the highest oxidation rates for various contaminants coincide.

In the preferred forms of implementation of the proposed method, the chemical composition of the catalytic coating, including the ratio of components, is selected according to the value of the highest rate of photocatalytic oxidation of one pollution, preferably pollution, by the amount prevailing in the total composition.

In alternative forms of implementation of the proposed method, the chemical composition of the catalytic coating, including the ratio of components, is selected according to the smallest standard deviation from the value of the highest rates of photocatalytic oxidation for all removed contaminants. This form of implementation of the proposed method is used, preferably, with comparable proportions of pollution.

In the preferred forms of implementation of the proposed method, the characteristics of the electrical potential of the carrier with a catalytic coating are regulated, and the value and polarity of the electrical potential are selected according to the value and polarity of the potential of the highest rate of photocatalytic oxidation of one pollution, preferably pollution, by the amount prevailing in the total composition.

In alternative forms of implementation of the proposed method, the characteristics of the electrical potential of the carrier with a catalytic coating are regulated, and the value and polarity of the electrical potential are selected according to the smallest standard deviation from the value of the electrical potentials of the highest rates of photocatalytic oxidation for each of the removed contaminants. This form of implementation of the proposed method is used, preferably, with comparable proportions of pollution.

In the preferred forms of implementation of the proposed method, the moment of turning on / off the photocatalytic unit in operation is determined by calculating the time to reach the maximum permissible level of pollution after the photocatalytic unit by differentiating the rate of catalytic decomposition of pollution and the rate of change in the amount of pollution over time.

Additionally, the moment of turning on / off the unit in operation should be associated with the calculation of the time to reach the maximum permissible level of pollution by differentiating the speed over time

- 4 039152 catalytic decomposition of contaminants and the rate of change in the amount of contaminants, followed by comparison of the time of approaching the desired differentials to zero, which is a dynamic control and is important when remotely controlling the cleaning process.

The definitions of the optimal design and technological parameters were obtained on the basis of the formulas developed and given below in the description by the author for calculating the light losses necessary for the catalysis process by analyzing the schemes for studying light losses from a source of ultraviolet radiation in a package of carriers with a catalytic coating, an increase in the reaction rate was obtained by controlling the temperature and coating potential and in connection with the type and ratio of contaminants, and dynamic regulation is carried out by differentiation over time of contaminant concentrations and the rate of decomposition reaction.

The above and other advantages, advantages and features of the claimed invention will be further discussed in more detail on some of the possible, but non-limiting examples of the implementation of the claimed photocatalytic air purification device and the method for dynamically controlling the degree of photocatalytic air purification in it with reference to the position of the figures of the drawings, in which schematically presented:

fig. 1 - device for photocatalytic air purification with one module of photocatalytic oxidation;

fig. 2 - device for photocatalytic air purification with two photocatalytic oxidation modules;

fig. 3 - device for photocatalytic air purification with three photocatalytic oxidation modules;

fig. 4 - general view of the device for photocatalytic air purification;

fig. 5 is a diagram of the arrangement of photocatalytic oxidation modules at an angle;

fig. 6 - scheme for calculating the working length of carriers under direct illumination;

fig. 7 is a plot of illumination from a point source as a function of the cosine of the angle of incidence of light on a carrier with a catalytic coating;

fig. 8 is a graph of the dependence of illumination on the cosine of the angle of incidence of light on a carrier with a catalytic coating under direct irradiation with an ultraviolet radiation source from one side of the photocatalytic oxidation module, combined with a graphic representation of the gap between the carriers;

fig. 9 is a graph of the dependence of illumination on the cosine of the angle of incidence of light on carriers with a catalyst under direct irradiation with an ultraviolet radiation source from both sides of the photocatalytic oxidation module, combined with a graphic representation of the gap between the carriers;

fig. 10 is a graph of the dependence of illumination on the number of reflections for stainless steel and aluminum;

fig. 11 is a graph of illuminance versus number of reflections with an ultraviolet light source on one side of the photocatalytic oxidation module, combined with a graphic representation of the gap between stainless steel carriers;

fig. 12 is a graph of illuminance versus number of reflections with an ultraviolet light source on both sides of the photocatalytic oxidation module, combined with a graphic representation of the gap between stainless steel carriers;

fig. 13 is a plot of illuminance versus number of reflections with an ultraviolet radiation source on one side of the photocatalytic oxidation module, combined with a graphic representation of the gap between aluminum carriers;

fig. 14 is a plot of illuminance versus number of reflections with an ultraviolet radiation source on both sides of the photocatalytic oxidation module, combined with a graphic representation of the gap between aluminum carriers;

fig. 15 is a graph of the degree of purification in the second and third photocatalyst units as a function of the degree of purification in the first photocatalyst unit;

fig. 16 is a diagram for calculating the ratio of the cross-sectional area of the photocatalytic block in the channel to the carrier area.

fig. 17 is a diagram of measurements during air purification from acetone in a device with two blocks.

fig. 18 is a plot of formaldehyde concentration in mg/m ³ over 20 days.

fig. 19 is a graph of the change in the concentration of formaldehyde in % after turning on the photocatalytic purification device.

fig. 20 is a plot of VOC concentration (Volatile Organic Compounds - volatile organic mixtures) in mg/m ³ over 20 days.

fig. 21 is a graph of the change in VOC concentration in % after turning on the photocatalytic purification device.

In FIG. 1 schematically shows a photocatalytic air purification device comprising a photocatalytic oxidation module 1 in which carriers 2 with a catalytic coating are collected in parallel with a gap 3. The module 1 is illuminated by a radiation source 4.

- 5 039152

In FIG. 2 schematically shows a photocatalytic air purification device comprising two photocatalytic oxidation modules 1 with catalytically coated carriers 2.

In FIG. 3 schematically shows a photocatalytic air purification device comprising three photocatalytic oxidation modules 1 with catalytically coated carriers 2.

In FIG. 4 schematically shows a general view of a photocatalytic air purification device, where the photocatalytic oxidation modules 1 are located in the channel 5, while the passage of the medium to be cleaned is provided by means 6 for moving air, in particular a fan. In this case, each photocatalytic oxidation module 1 and the corresponding radiation source 4 form a photocatalytic unit 7.

In FIG. 5 shows the layout of the photocatalytic oxidation modules at an angle in channel 5.

In FIG. 6 shows a radiation source 4, on the surface of which a point light source 8 is isolated, light rays 9 in a gap 3, angles θ of incidence of light rays 9 from a radiation source 4 onto the surface of carriers 2 with a catalytic coating. Under carriers 2 there is a scale of 10 lengths, graduated in mm.

In FIG. 7 shows a graph of the fall in illumination E in the gap 3 as a function of the cosine of the angle θ of the incidence of light rays 9 from the radiation source 4 onto the surface of carriers 2 with a catalytic coating.

In FIG. 8 shows a graph of the fall in illumination E in a gap 3 equal to 3 mm as a function of the cosine of the angle θ of incidence of direct light rays 9 from radiation sources 4 located on one side onto the surface of carriers 2 with a catalytic coating. Below the graph is a scale of 10 lengths, graduated in mm.

In FIG. 9 shows a graph of changes in illumination E in a gap 3 equal to 3 mm as a function of the cosine of the angle θ of incidence of direct light rays 9 from radiation sources 4 located on both sides onto the surface of carriers 2 with a catalytic coating. Below the graph is a scale of 10 lengths, graduated in mm.

In FIG. 10 shows a graph of the dependence of illumination E on the number of reflections for stainless steel and aluminum, the fall in illumination depending on the number of light reflections in gap 3 for carrier 2 made of stainless steel 11 and aluminum 12.

In FIG. 11 is a plot of the illumination E as a function of the number of light reflections in the gap 3 with an ultraviolet radiation source 4 on one side of the photocatalytic oxidation module 1 between stainless steel carriers 2.

In FIG. 12 shows a graph of the dependence of illumination E on the number of light reflections in the gap 3 with an ultraviolet radiation source 4 on both sides of the photocatalytic oxidation module 1 between stainless steel carriers 2.

In FIG. 13 shows a graph of the dependence of illumination E on the number of light reflections in the gap 3 with an ultraviolet radiation source 4 on one side of the photocatalytic oxidation module 1 between aluminum carriers 2.

In FIG. 14 shows a graph of the dependence of illumination E on the number of light reflections in the gap 3 with an ultraviolet radiation source 4 on both sides of the photocatalytic oxidation module 1 between aluminum carriers 2.

In FIG. 15 is a graph of the degree of purification in the second and third photocatalyst units 7 as a function of the degree of purification in the first photocatalyst unit 7.

In FIG. 16 is a graph of the ratio of oxidation rates for carbon monoxide 13, gasoline 14, isobutane 15, car exhaust 16, tobacco smoke 17, ethyl acetate 18, ammonia 19, and acetone 20.

In FIG. 17 shows the measurement scheme for air purification from acetone in a device with two blocks.

In FIG. 18-21 shows graphs of changes in the concentration of contaminants after turning on the cleaning device. In FIG. 18 is a plot of formaldehyde concentration in mg/m ³ over 20 days. The point 0.85 mg/m ³ on the graph is the moment the cleaning device is turned on. In FIG. 19 is a graph of the change in the concentration of formaldehyde in % after turning on the cleaning device. The point 0.85 mg/m ³ on the graph is taken as 100% - the moment the cleaning device is turned on. In FIG. 20 is a graph showing the change in VOC concentration in mg/m3 over 20 days. The 5.8 mg/m ³ point on the graph is the moment the cleaning device is turned on. In FIG. 21 is a graph of the change in VOC concentration in % after turning on the cleaning device. The point 5.8 mg/m ³ on the graph is taken as 100% - at the moment the cleaning device is turned on.

The inventive device for photocatalytic air purification with the implementation of the proposed method for dynamic control of the degree of photocatalytic air purification in it functions as follows.

The photocatalytic oxidation module 1 is assembled from carriers 2 made of stainless steel or aluminum, which are the substrate for applying a catalytic coating, while the carriers 2 are placed in parallel to form a gap 3. The photocatalytic oxidation module 1 is illuminated by a radiation source 4, while said module 1 is located in the channel 5. On one or both sides of the photocatalytic oxidation module 1, at least one radiation source 4 is installed in the form of ultraviolet radiation sources, fluorescent lamps or LEDs. The air to be cleaned is passed through a channel 5 with a rectangular, round or other cross section by means of an air moving means 6 in the form of a fan.

Each photocatalytic oxidation module 1 and the corresponding radiation source 4 form a photocatalytic unit 7.

With the passage of the air to be cleaned on the catalytic coating in the presence of ultraviolet light and water, the cleaning process previously mentioned with reference to the prior art takes place.

The proposed decision to use as a source 4 radiation with an emission spectrum in the range from 200 to 1000 nm allows you to provide several new effects.

Impulse xenon lamps are capable of realizing such an emission spectrum.

Additionally, a xenon lamp has an active warming effect on the bodies under its radiation, and the power per pulse is from 25,000 W / cm ² .

By adjusting the power and wavelength of the radiation source 4, the heating of the catalytic coating layer on the carrier 2 is regulated to the temperature of the maximum rate of pollution oxidation. At the same time, radiant heating of the catalytic coating layer does not heat the carrier 2 itself either, so only the surface layer is heated with minimal power consumption. Also, taking into account the location of the radiation source 4 and the length of the carrier 2, it becomes possible to control the temperature along the length of the carrier 2 to select the temperature of the maximum oxidation rate for different pollutants.

Depending on the amount and ratio of contaminant concentrations, it becomes possible to choose the optimal temperature.

Carriers 2 are in the stream of air to be cleaned, which leads to the electrification of the surface and the emergence of an electric potential, so it is maintained and regulated by connecting to a source of electricity or grounding.

The value and polarity of the electric potential is chosen according to the value and polarity of the potential of the highest rate of photocatalytic oxidation of one pollution, preferably pollution, according to the amount prevailing in the total composition or according to the smallest standard deviation from the value of the electric potentials of the highest rates of photocatalytic oxidation for each of the removed pollution.

The efficiency of the photocatalytic air purification device also depends on the area of the carriers 2 with a catalytic coating, and the total area of the carriers 2 determines the cost and energy consumption during the operation of the catalyst.

Optimization of the geometrical dimensions of the purifier and the purification process was performed on the basis of the calculations below for the loss of light in module 1 from carriers 2 and the rates of oxidation of pollutants.

The test results made it possible to obtain the values of the degree of purification in the first photocatalytic unit 1 of the photocatalytic air purification device, which are taken as reference when deriving formulas for the method for determining the degree of purification in subsequent photocatalytic units 7, as well as determining a sufficient number of photocatalytic units 7.

The light from the radiation source 4, which has fallen into the gap 3 between the carriers 2, weakens as it moves away from the edge. Therefore, the oxidation reactions on the catalytic layer are weakened.

Based on the calculation of light losses in gap 3 and experimental data on the efficiency of the degree of purification by one block, numerical data were obtained for recommendations on determining the effective length of carriers 2 in photocatalytic oxidation module 1.

In FIG. 6, the illumination of the surface of carriers 2 is considered by a point emitter 8 isolated on the source 4, located on one side and emitting an elementary beam of light 9.

It follows from the inverse square law that the illumination generated by a point emitter 8 is inversely proportional to the distance from the point emitter to the surface and directly proportional to the cosine of the angle θ between the direction of the light flux and the normal to the illuminated surface:

E \u003d T x cos0 / r ² , where E is the illumination;

θ is the angle of incidence of light on the surface of the plate;

I - light intensity of the source in the direction of the illuminated point;

r is the distance from the source to the illuminated surface.

Due to the fact that many point light emitters 8 are installed at a small distance from the edge of the carriers 2 in comparison with the dimensions of the source 4, the change in r can be neglected, therefore, the main factor affecting the illumination is the angle θ.

The dependence of illumination E on the cosine of the angle θ is shown in Fig. 7 and used for further

- 7 039152 dependency builds. This graph also allows you to determine the minimum acceptable gap 3 between the media attenuation of light.

The dependence of the illumination E on the cosine of the angle θ under direct illumination by a point emitter 8 on one side of the module 1, combined with a graphic representation of the carriers 2, of the length scale 10, is shown in Fig. 8. In this case, the illumination graph has a zero point at an angle of 90 °.

The dependence of illumination on the cosine of the angle θ under direct illumination by point emitters 8 from both sides of the module 1, combined with a graphic representation of carriers 2, of the length scale 10, is shown in Fig. 9. At the same time, the choice of the length of carrier 2 for direct illumination from both sides is made in such a way that not only is there no point with zero illumination, but the illumination does not fall below the set residual illumination, in this case it is 10% of the initial value.

The calculation of the length of carriers 2 with a catalytic coating under direct illumination according to the described method is suitable for materials with a low reflectivity. Their use is not the most effective, in reality, with a multitude of point emitters, multiple reflections from carriers 2 occur inside gap 3, and the illumination turns out to be greater, therefore, the material of carrier 2 should be selected with maximum reflection, provided that a coating of titanium dioxide is applied.

The calculation of the working length of carriers 2 under reflected illumination was obtained from the found dependence of the fraction of reflected light on the number of reflections and the initial fraction of reflected light:

where Ki is the proportion of reflected light, in %, i is the number of reflections,

K ₀ - initial fraction of reflected light, in % at i=1.

Stainless steel and aluminum were further considered as materials for the substrate.

The result of calculating the dependence of illumination E on the number of reflections for stainless steel is shown in Fig. eleven.

The result of calculating the dependence of illumination E on the number of reflections for aluminum is shown in Fig. 13.

Since the lower illumination threshold of 10% of the initial value was applied in the calculations, the declared lengths of carriers 2 were obtained when module 1 of the photocatalytic oxidizer was illuminated on one side for carriers made of stainless steel and no more than 145 mm. When the photocatalytic oxidation module 1 is illuminated from both sides, the lengths of the carriers 2 made of stainless steel are no more than 100 mm, those of aluminum are no more than 290 mm.

In today's world, some of the main pollutants are carbon monoxide, gasoline, isobutane, car exhaust, tobacco smoke, ethyl acetate, formaldehyde, ammonia and acetone.

Based on the experimental data on the decomposition time, the optimal ratio of the cross-sectional area of the photocatalytic block 7 in the channel 5 to the total area of the carriers 2 with a catalytic coating in the form of titanium dioxide was obtained and declared in the range from 1/66 to 1/193.

At high concentrations of contaminants or high demands on the degree of purification, the photocatalytic units 7 are installed and operated in series. In this case, sources 4 of ultraviolet radiation work more efficiently, but more power is required to pump the cleaned air.

Therefore, the calculation of the number of blocks, the number of passes and the expected degree of purification is relevant and was carried out on the basis of an experiment to study the degree of purification in one block as a reference.

Based on the above formulas, a method is claimed for dynamically controlling the degree of photocatalytic air purification by determining the number of blocks or the number of passes during recirculation, and the on/off moment is determined by differentiating the rate of pollution decomposition.

The obtained formulas for the degree of purification in the second and third blocks show that when the conditions for the ratio of areas from 1/66 to 1/193 are fulfilled, it is not advisable to use more than three blocks or passages during recirculation.

The claimed method will also be illustrated further on one of the possible, but non-limiting examples of its implementation.

Example 1

Initial data for calculation:

pollutant - acetone;

the required degree of purification is 80.0±5%.

For the mode of exhaust and supply ventilation, the total degree of purification of C12 after the second block is calculated according to the claimed formula:

C12 \u003d 2C1 -0.01C1 ²

- 8 039152

In this case, C1 - the degree of purification of acetone after the first block is determined in proportion to the degree of purification of ethyl acetate, for which C1 = 57.82.

In table. Table 1 gives recommendations on choosing the ratio of the cross-sectional area of block 7 to the area of carriers 2 in module 1, depending on the type of air pollution. In accordance with this table. 1, the ratio of the cross-sectional area of the photocatalytic block 7 in the channel 5 to the area of the carriers 2 for contamination in the form of acetone is 1/66.

Table 1. Ratios of the cross-sectional area of block 7 to the area of carriers 2 in module 1 depending on the type of air pollution

The ratio of the cross-sectional area of the photocatalytic block in the channel to the area of the elements of the photocatalytic oxidation package Carbon monoxide 1/193 Petrol 1/182 Methane 1/166 Traffic fumes 1/152 Cigarette smoke 1/152 ethyl acetate 1/116 Ammonia 1/80 Acetone 1/66

Thus, the calculation of the total degree of purification from acetone C12 after the second block gives C12 = 82.2%.

The formulas are derived from the dependences on the degree of purification on a pilot-industrial device for photocatalytic air purification, made according to the measurement scheme shown in Fig. 17.

The total degree of air purification from acetone in one pass in a two-block purifier according to the results of experimental data is 82.12%, which indicates a high convergence of the obtained experimental data with theoretical calculation.

Thus, a theoretical calculation was made for one pollution of the degree of purification of another pollution, and the experimental data for the purification of another pollution, as close as possible to the calculated value.

Sources of information

1. Patent RU 159723U1, published. February 20, 2016

2. Patent RU 2497584С1, publ. November 10, 2013

3. Patent GB 2472509 (A), publ. 02/09/2011

4. Patent RU 2259866C1, published. September 10, 2005

5. Patent RU 2262455C1, published. October 20, 2005

6. Patent RU 2450851С2, publ. May 20, 2012

Claims (23)

1. A device for photocatalytic air purification, containing means (6) for moving air, creating an air flow through the channel (5), carriers (2) located in the channel (5) with a catalytic coating active in the radiation spectrum from infrared to ultraviolet, while the carriers (2) are assembled in parallel with the gap (3) in at least one module (1) of photocatalytic oxidation, and the specified module (1) is made with the possibility of illumination from at least one of the sides by at least one radiation source (4) made with the possibility of lighting in continuous or pulsed mode, and each module (1) of photocatalytic oxidation and at least one corresponding source (4) of radiation form a photocatalytic unit (7), characterized in that in the photocatalytic unit (7) continuous illumination mode is used for emission spectrum in the range from 200 to 400 nm, and the pulsed lighting mode is implemented by xenon lamps with an emission spectrum in the range from 200 to 1000 nm, while the photocatalytic unit (7) is configured to control and maintain the temperature of the catalytic coating on - 9 039152 carrier (2) by means of the specified xenon lamps, the ratio of the cross-sectional area of the photocatalytic block (7) in the channel (5) to the area of carriers (2) with a catalytic coating belongs to the interval 1/66 - 1/193, and the length of the carriers (2 ) are determined at the design stage by one-sided or two-sided illumination of the photocatalytic oxidation module (1) and the carrier material (2), contains at least two photocatalytic blocks (7), while the blocks are installed in series with the possibility of independent remote control of turning them on / off. 2. Device according to claim 1, characterized in that the catalytic coating of the carriers is made of titanium dioxide, preferably in anatase or rutile phases. 3. The device according to claim 1, characterized in that the photocatalytic unit (7) is configured to control and maintain the temperature of the catalytic coating on the carrier (2) by heating due to the radiation of a part of the spectrum of the radiation source, by changing the lighting mode. 4. The device according to claim 1, characterized in that the photocatalytic unit (7) is configured to regulate and maintain the sign and value of the potential of the catalytic coating on the carrier (2) by connecting to a source of electricity or grounding. 5. The device according to claim 1, characterized in that the length of the carriers (2) when the module (1) of photocatalytic oxidation is illuminated by a light source (4) located on one side, for a carrier (2) made of stainless steel is not more than 50 mm, for carrier (2) made of aluminum is not more than 145 mm, and when the module (1) of photocatalytic oxidation is illuminated by sources (4) of illumination located on opposite sides, for carrier (2) made of stainless steel is no more than 100 mm, for carrier (2 ) from aluminum no more than 290 mm. 6. The device according to claim 1, characterized in that when the module (1) of photocatalytic oxidation is illuminated by at least two sources (4) of radiation, each of the sources (4) of radiation is configured to be illuminated in continuous or pulsed mode independently of the other source (4) radiation. 7. The device according to claim 1, characterized in that when the module (1) of photocatalytic oxidation is illuminated by at least two sources (4) of radiation, one of them is made with the possibility of illumination in continuous, and the second in a pulsed mode alternately, or sources (4) radiation is made with the possibility of illumination in only one mode. 8. The device according to claim 1, characterized in that when cleaning air from acetone, ammonia, ethyl acetate and other substances that are easily decomposed on the catalytic coating of carriers (2), the ratio of the cross-sectional area of the photocatalytic oxidation module (1) in the channel (5) to the carrier area (2) is selected from the interval 1/66 - 1/97. 9. The device according to claim 1, characterized in that when cleaning air from formaldehydes, aliphatic hydrocarbons C1-C ₁₀ , carbon monoxide, exhaust gases, cigarette smoke and other substances that are difficult to decompose on the catalytic coating of carriers (2), the ratio of the area of the transverse section of the module (1) of photocatalytic oxidation in the channel (5) to the area of carriers (2), selected from the interval 1/97-1/193. 10. The device according to claim 1, characterized in that the carriers (2) are inclined with respect to the axis of the channel (5). 11. The device according to claim 1, characterized in that in the presence of two or more photocatalytic blocks (7) adjacent photocatalytic blocks (7) are located at different angles of inclination to the axis of the channel (5), while at least part of the photocatalytic blocks (7 ) can be located at an inclination angle of 0°. 12. The device according to any one of claims 1 to 9, characterized in that the air flow is formed with the possibility of passing through the channel (5) in a mode selected from the exhaust ventilation mode, the supply ventilation mode and the recirculation mode. 13. A method for dynamically controlling the degree of photocatalytic air purification in a device according to any one of claims 1 to 10, including passing the stream of air to be purified sequentially through remote independent control of switching on / off individual photocatalytic units (7) depending on physical and chemical characteristics of carriers (2) and catalytic coating on carriers (2) of modules (1) of photocatalytic oxidation, determining the number of sequentially installed photocatalytic units (7) to be put into operation, and determining the moment of switching on/off each photocatalytic unit (7) into operation, at the same time, the number of successively installed photocatalytic units (7) to be put into operation in the exhaust ventilation mode and in the supply ventilation mode is determined by the degree of purification in the first photocatalytic unit (7), and in the recirculation mode, by the degree of purification in the first pass in the first photocatalyst In the logical block (7), the number of passes of the air to be cleaned is additionally determined, and the degree of purification in the second and subsequent photocatalytic blocks (7) and passages in the indicated modes is determined based on the degree of purification in the first block and passage, respectively. 14. The method according to claim 13, characterized in that the degree of purification in the second and subsequent photocatalytic units (7) is determined by the following formulas: - 10 039152 for the mode of exhaust and supply ventilation, the total degree of purification after the second block C ₁₂ \u003d 2C _X - 0.01Ci ² , (1) where C1 is the degree of purification after the first block,%, C ₁₂ - total degree of purification after the first and second blocks, %; for the mode of exhaust and supply ventilation, the total degree of purification after the third block Cp = 3Ci - 0.03Ci ² +0.0001Ci ³ , (2) where C ₁₂₃ is the total degree of purification after the first, second and third block, %; - for the recirculation mode, the degree of purification after the first block K _h = [(K _n x (0.01xCi ) + _Kg ) xV _r ] / V _u , (3) for the recirculation mode, the total degree of purification after the second block K _h = [(K _n x (2Ci - 0.01Ci ² ) « ^w vr)xh.i) _{+ xVr]} / ( ₄ ) for the recirculation mode, the total degree of purification after the third block K _h = [(K _n x (3Ci - 0.03Ci ² +0.0001Ci ³ ) + K _g ) xV _r ] / V _u , (5) where in formulas (3)-(5) K _h - residual concentration after cleaning, %, h - operating time of the recirculator, h, C ₁ - degree of purification after the first block,%, K _n - initial concentration of pollutants in the room,%, Kg - additional emissions of pollutants from K _n , %/h, V _r - room volume, m ³ , V _r = VuxK^KdxCA^^ + K _g ), (6) Vu - recirculator capacity, m/h, V _u =[(K _n xC ₁ ^((Vu/Vr)xh ' ¹⁾ + K _g ) xV _r ] / K _h . (7) 15. The method according to claim 13, characterized in that the temperature of the catalytic coating on the carrier (2) is controlled, and the temperature is chosen according to the temperature value of the highest rate of photocatalytic oxidation of one pollution, preferably the pollution that prevails in terms of quantity in the total composition of pollution. 16. The method according to claim 13, characterized in that the temperature of the catalytic coating on the carrier (2) is controlled, and the temperature is chosen according to the smallest standard deviation from the temperature value of the highest rates of photocatalytic oxidation for all removed contaminants. 17. The method according to claim 13, characterized in that the temperature of the catalytic coating on the support (2) is controlled, and the temperature is chosen taking into account the values of the temperatures of the highest oxidation rates and the specific concentrations of contaminants to be removed. 18. The method according to claim 13, characterized in that the temperature of the catalytic coating on the support (2) is controlled, and the temperature is chosen to be variable along the length of the support (2) in the photocatalytic oxidation module (1). 19. The method according to claim 13, characterized in that the chemical composition of the catalytic coating, including the ratio of components, is selected according to the value of the highest rate of photocatalytic oxidation of one pollution, preferably pollution, by the amount prevailing in the total composition. 20. The method according to claim 13, characterized in that the chemical composition of the catalytic coating, including the ratio of components, is selected according to the smallest standard deviation from the value of the highest rates of photocatalytic oxidation for all removed contaminants. 21. The method according to claim 13, characterized in that the characteristics of the electrical potential of the support (2) with a catalytic coating are regulated, and the value and polarity of the electrical potential are selected according to the value and polarity of the potential of the highest rate of photocatalytic oxidation of one pollution, preferably pollution, according to the amount of the predominant in the general composition. 22. The method according to claim 13, characterized in that the characteristics of the electrical potential of the carrier (2) with a catalytic coating are controlled, and the value and polarity of the electrical potential are selected according to the smallest standard deviation from the value of the electrical potentials of the highest rates of photocatalytic oxidation for each of the removed contaminants. 23. The method according to claim 13, characterized in that the moment of turning on / off the photocatalytic unit (7) in operation is determined by calculating the time to reach the maximum permissible level of pollution after the photocatalytic unit (7) by differentiating the rate of catalytic decomposition of pollution and the rate of change in the amount of pollution over time pollution.