PROCEDURE AND APPARATUS FOR CLEANING OF AIR

This invention relates to a method for air purification, as described in the preamble of Claim 1, and to an air purification apparatus, as described in the preamble of Claim 10.

The air we breathe contains a large number of impurities that have a variety of health effects. In many cases, the amount of such impurities is constantly increasing due to traffic, industry and other emissions. Similarly, many viruses and epidemics release dangerous impurities into the air. In addition the air is affected by increasing problems with mildew in buildings, as well as volatile organic compounds

(VOCs) . Further, the air is often polluted by tobacco smoke and growing amounts of carbon dioxide. The problem is to create a properly functioning, sufficiently efficient system that can effectively remove all the different kinds of impurities from the air we breathe.

In known technology, various mechanical filters, ionisers and ozonisers are used for air purification, but none of these technologies alone is sufficient to remove all the impurities present in the air efficiently enough. In addition, air filters according to known technology are passive, i.e. they do not process the air for purification in any way. They operate mechanically, letting through or impeding particles of a certain size depending on the size of the holes in the filter, until the holes become blocked after which nothing else will pass through the filter. One problem is filter cleaning, which is usually not done frequently enough. In time, these kinds of filters collect bacteria and mould spores, and when the filter acquires enough moisture, it begins to form and release the metabolic products of mould, which are extremely toxic. This is often the cause of poor indoor air quality.

SUBST5TUTE SHEET (Rule26)

The object of this invention is to remove the problems described above and to achieve a sufficiently affordable, efficient method and equipment for removing many kinds of impurities from the air, requiring little cleaning and being easy to maintain. The method described in the invention is characterised by what is disclosed in the characterisation part of claim 1. Similarly, the apparatus described in the invention is characterised by what is disclosed in the characterisation part of claim 10. Other embodiments of the invention are characterised by what is disclosed in the other claims .

The method and apparatus according to the invention will hereafter be referred to collectively as the solution according to the invention. An advantage offered by the solution according to the invention is that it can remove a multitude of types of impurities from the air. Another advantage is the fact that the apparatus is self-freshening, i.e. it cleans itself for the most part. Only certain elements need to be cleaned from time to time. Another advantage is the fact that thanks to its controls, the apparatus is very energy-friendly, meaning it uses little energy when there is not much to purify. A further advantage is the fact that the apparatus can easily be equipped with a function that uses ozone to increase the amount of oxygen in the output air, freshening the air and making it healthier to breathe. This is useful for instance in school classrooms and other similar facilities. Another advantage is that thanks to its modular structure, the apparatus is easy to maintain, as only the module that needs cleaning or replacing needs to be detached. Another advantage is the low flow resistance of the air to be purified, caused by the sub-modular structure of the purification elements.

Below, the invention is described in detail using an application example of the solution according to the invention, by referring to the appended figures, in which

Figure 1 shows the apparatus according to the invention, in diagrammatic and simplified form, partly in cross-section, diagonally from above,

Figure 2 shows the apparatus according to Figure 1 in diagrammatic and simplified form, from above and with the lid removed,

Figure 3 shows the apparatus according to Figure 1 in diagrammatic and simplified form, from the side and with the side wall removed, Figure 4 shows apparatuses according to the invention, connected in parallel, in diagrammatic and simplified form, viewed from the front,

Figure 5 shows apparatuses according to the invention, serially connected, in diagrammatic and simplified form, viewed from the side,

Figure 6 shows one part of a cold catalyst module according to the invention, in diagrammatic and simplified form, enlarged, viewed from the side and with the side wall removed, and Figure 7 shows one of the pleated substrates of a cold catalyst according to the invention, in simplified and diagrammatic form, viewed from the side.

Figure 1 displays an apparatus 1 according to the invention, in diagrammatic and simplified form, partly in cross-section, viewed diagonally from above. The apparatus 1 consists of an essentially rectangular box-like structure, containing at least parts 2a-2c forming sleeve surfaces, and two parts 2d forming end surfaces. The first end surface has an inlet 3 and the other end surface has an outlet 4. The air or gas to be purified is conducted through inlet 3 to the inside of apparatus 1 for purification, after which it is conducted out of apparatus 1 through outlet 4. Arrow 14 indicates incoming air or gas for purification and arrow 15 indicates purified air or gas. The apparatus's lid 2a and base 2c have rails 5 mounted at suitable intervals for modular purification elements 6-13 that are connected to the apparatus for various

purposes. The rails 5 hold these purification elements 6-13 in place.

The apparatus displayed in Figure 1 contains as purification elements at least a preliminary filter 6, which is placed first in the direction of flow of the air for purification, and which preliminary filter is designed to mechanically remove the largest impurities and dirt particles. The air for purification flows through the preliminary filter 6, which causes the largest impurities to be caught in the preliminary filter 6. Next in the direction of flow of the air is a preionisation element 7, which gives the particles passing through it additional reaction energy by charging them either positively or negatively. In other words, the particles receive either a negative or a positive electron. After this, the apparatus contains a UV radiation element 8, which radiates the air flow passing through it, killing all pathogens and providing more ions. Next in the direction of flow is an ozonising element 9, which oxidises and sterilises a large part of the hydrocarbons in the air into carbon dioxide and water vapour, and, if necessary, regenerates the activated carbon of later filters, if activated carbon filters are in use.

After the ozonising element 9, the apparatus contains a so called cold catalysis element 10, in which a nanocrystalline catalyst and the UV radiation directed at it are designed to create a plasma layer of OH radicals and electrons. This plasma layer oxidises practically all the remaining organic gases from the air. If activated carbon is used in the cold catalysis element 10 to adsorb VOCs, the catalyst also regenerates the carbon with the help of the plasma layer, i.e. it cleans the carbon by transforming pollutant particles into simpler chemical forms. After the cold catalysis element, in the direction of flow of the air, the apparatus contains for example an electret filter 11, designed to charge fine particles negatively or positively. The electret filter's earthed plates collect these particles. Next in the

direction of flow is a filter 12 with HEPA or other gauge, which removes the remaining fine particles from the air. At the end of the apparatus is for example an ionising element 13, similar to element 7, which ionises the air with negative ions making the air healthy to breathe and good for plants.

Depending on the air or gas for purification, the arrangement of modular elements 6-13 can be adjusted to suit their purpose for instance by making the rails 5 fit all the elements. Then the elements can be pushed into the groove in the rails 5 from the side of the apparatus. In addition, the supply current to power the elements is brought to the apparatus such that it can easily be distributed between all the elements requiring power, which elements have the necessary connectors for being connected to the power supply. Depending on the conditions of use, elements 6-13 can be placed in different places. Elements' needing power are connected to power supply connectors placed next to each element station.

Figures 2 and 3 display an apparatus according to the invention, viewed from above and from the side. Preliminary filter 6 is a mechanical filter according to known technology, which removes largish impurities and particles from the air flow. The preliminary filter may need to be cleaned from time to time.

The second element, preionisation element I ₁ consists for example of vertical, metallic, earthed compartments 17 formed with guide plates 16 connected to the main framework and placed at suitable intervals. The air to be purified passes through these compartments 17. In the middle of each compartment 17 is an essentially vertical wire 18, insulated from the element's frame and charged either negatively or positively with high voltage. The voltage charge can be for example 4-8 kV, but it can be anything up to for example 50 kV or even above this. This creates a strong electrical field around wires 18, so that when the air passes through the

compartments 17, the particles in the air are ionised, i.e. they become charged either negatively or positively depending on the charge of the wire 18. Preionisation is used to increase the effectiveness of the later purification processes.

The third element in this example is a UV radiation element 8, in which UV lamps 19 direct UV radiation with a wavelength of approx. 100-400 nm to the passing air. This causes a UV field that essentially kills all the passing bacteria and viruses. It also increases the ionisation of the air flow. The UV radiation source can be for example a germicidal UV radiation element, whose radiation is between 240 and 280 nm, and most favourably approx. 254 nm.

The next element in the direction of flow, the ozonising element 9, also contains UV light sources 20. The wavelength in this element is shorter, however, than in the previous element 8. In the ozonising element the wavelength is approx. 150-200 nm, most favourably approx. 184-185 nm. As a result, some of the oxygen in the air passing through the ozonising element 9 turns into ozone. Ozonisation is also a preliminary- purification measure, strongly oxidising all organic gases and impurities in the air, turning them into water vapour and carbon dioxide. Ozonisation is a well-known and effective way to remove various smells and e.g. mould spores from the air.

After ozonisation, the apparatus has a cold catalysis element 10, which is an extremely important stage in the purification of the air. Cold catalysis is also known as photocatalysis . In the cold catalysis element, an essentially film-like catalyst coating is placed by casting, spraying, spreading or another suitable method on top of a suitable substrate 21 that allows the air to pass through it. This film-like catalyst coating consists of nanocrystalline titanium dioxide powder, whose particle size is only a few nanometres, e.g. 5- 20 nm. Substrate 21 is chosen such that the catalyst coating has as large a surface area as possible. The substrate can

consist for instance of porous perforated material, of a compartmentalised model used in filters or of another suitable model that allows air to flow through it and provides a maximal surface are for the catalyst coating. In the cold catalysis element 10, UV light with a wavelength between 200 and 500 nm, most favourably approx. 365 run, is directed towards the catalyst coating, creating an excitation reaction. This means that the electrons surrounding the titanium oxide atom become excited so that they move from lower belts to higher belts due to the effect of the UV light. This releases a large amount of energy and causes gaps to form in the lower belts. The energy released combines with the air and the water vapour in it to form very strong OH radicals (hydroxyl radicals) . At the same time, a very strong electron flux with positive or negative ions is caused in the field. This creates a plasma layer that very strongly oxidises the polluted air passing through it. This breaks down all the organic material in the air into simpler chemical forms, i.e. into carbon dioxide and water vapour. The process according to the invention is characterised by taking place at an essentially low temperature. A suitable temperature is for example room temperature (hence the name cold catalysis) . Therefore the temperature for the process is for example under +3O ⁰ C. Cold catalysis is made significantly more effective by the catalyst coating being bombarded during the UV radiation with a negatively charged electron shower, which shower is facilitated by the ionisation of the air that takes place before the cold catalysis in the preionisation element 7. This makes the abovementioned excitation reaction many times faster than if it were conducted without preionisation .

The next element after the cold catalysis element 10, in the direction of flow of the air, is an electret filter 11, which is equipped essentially with similar guide plates 22 as the preionisation element's guide plates 16, as well as with essentially similar high-voltage-charged wires 23 as the preionisation element's wires 18. However, in the electret

filter 11, the distance between the guide plates 22 and the wires 23 is smaller than in the preionisation element 7. Thus the compartments 24, through which the air passes, are narrower than the compartments 17 in the preionisation element. The frame and guide plates 22 of the electret filter 11 are earthed and the wires 23 are insulated from the frame and from the guide plates, which creates a high-voltage field between the wires 23 and the guide plates 22. The particles flowing through the electret filter are charged either positively or negatively in the electret filter 11. Because the guide plates 22 and wires 23 are differently charged, the air particles and, especially, the toxic fine particles that are charged by the wires 23 bond to the electret filter's 11 guide plates as the air flows through the filter. The particles that have bonded to the guide plates 22 are removed regularly for instance by removing the electret filter from the apparatus and washing it with water.

Next after the electret filter 22 is a HEPA filter 12, or a filter with a different gauge, which removes particles of less than one micron in size from the air flow. The HEPA filter may be accompanied by an activated carbon filter to make particle collection even more effective.

Figures 2 and 3 also show as an optional accessory a fan 25 attached to the inlet 3 of the apparatus 1, and an aspirating fan 26, attached to the outlet 4, which fans speed up the flow of air through the apparatus 1. In addition, next to the inlet to the apparatus 1, there is a sensor 27, which is arranged to monitor and measure the total pollution level of the air coming in, determining for example how many organic compounds (VOCs) are present in the incoming air. In practice, particularly in industry, smell loads vary between different times, which means that the amount of VOCs also varies. Peak loads appear from time to time. If the apparatus operated according to peak loads constantly, it would be subjected to unnecessary loads when there is less smell pollution. To eliminate this problem, the apparatus 1

according to the invention is also equipped with a controlling sensor 28, which is placed next to the air outlet to measure the purity of the outgoing air. Sensors 27 and 28 are connected to an intelligent unit 29, such as a computer or similar device equipped at least with a suitable interface, data processing tools, memory, a database and software. The computer 29 is connected to the apparatus's different modules, for example to one or more of the following elements: preionisation element 7, UV radiation element 8, ozonising element 9, cold catalysis element 10 and electret filter 11, whose operating power the computer 29 is designed to adjust by adjusting the current and/or voltage or by cutting of the supply current completely from some elements when necessary. In this way for example the computer 29 controls the progress of the purification process when necessary. In addition the computer is connected to fans 25 and 26 and equipped to control and adjust through them the flow of air for purification.

Figures 4 and 5 display different connections of purification apparatus 1 according to the invention, to satisfy different purification needs. Purification elements 6-13 placed inside the apparatus 1 are modular, but the apparatus 1 itself can also make up a module of a larger entity. In order to purify large quantities of gas, several apparatuses 1 can be connected in parallel as displayed in Figure 4. Similarly, if the purification needs to be especially effective, the apparatuses 1 can be connected serially as displayed in figure 5. In this case, the outlet 4 of each apparatus 1 is connected to the next apparatus's inlet 3 with a pipe-like connector 3a. To purify large amounts of gas effectively, apparatuses 1 can be connected simultaneously both in parallel and serially. This means that the same basic apparatus unit 1 can be applied to many uses.

Figure 6 displays one part of a cold catalysis element 10 according to the invention, in diagrammatic, simplified and enlarged form. In this structure, the cold catalysis element

10 consists of several similar sub-modules 10a, placed on top of each other and connected in parallel. Each sub-module 10a has an inflow aperture 31, placed at the front of the sub- module in relation to the direction of flow, indicated by the arrow, and an outflow aperture 32 placed at the back. Each sub-module 10a contains a previously mentioned substrate 21, equipped with a catalyst coating, through which the air for purification is led to flow. In addition, each sub-module 10a contains lamps 30 that act as UV light sources and direct radiation at the catalyst coating. By placing the sub-module 10a of the cold catalysis 10 on top of each other as indicated in Figure 6, and by directing the air flow through each catalyst only once according to the flow pattern of figure 6, the surface area and effectiveness of the catalyst can be increased. The advantage of such a structure is a low flow resistance in comparison to a structure in which the air flow has to pass through all catalyst elements and substrates placed serially, for instance from top to bottom as in Figure 6. Flow resistance decreases as the number of sub-modules 10a increases. Another advantage is access to a large catalyst surface area, which is necessary in order to increase the relatively low effect of the catalyst. If necessary, at least some of the other elements 6-9 and 11-13 in the apparatus can be built using a similar structure composed of sub-modules and connected in parallel.

Figure 7 displays a cold catalyst structure according to the invention in simplified form. In it, an essentially film- like catalyst coating 33 is placed by casting, spraying, misting, spreading or another suitable method on top of a suitable flexible substrate 21, pleated into suitable angles A, that allows the air to pass through it. This film-like catalyst coating consists of nanocrystalline titanium dioxide powder, whose particle size is only a few nano- metres, e.g. 5-20 nm, as previously mentioned. Substrate 21 and the angles A between its pleats 35, which pleats are V- shaped when viewed from the side, are chosen such that the catalyst coating has as large a surface area as possible.

Every other pleat 35 faces downwards and every other one upwards. In addition the selection of the angles A between the pleats 35 makes it possible that the air flowing in the direction of arrow 34 does not pass directly through the catalyst film 33, making the distance travelled through the catalyst film 33 longer and therefore the purification more effective. The angles A between the pleats 35 are approximately 5-160° according to the invention, favourably e.g. 30-90°. Favourably, all the angles A of the pleats 35 in one cold catalysis element 10 are the same, but they can also vary. Thanks to the pleats 35, the catalyst structure resembles a folded or honeycombed structure.

In one favourable embodiment of the invention, the surface area of the catalyst film 33 is increased by placing tiny hollow balls coated with a layer of catalyst within the film, for instance during the production phase of the film.

The balls can be for instance oxide compounds of rare earth metals, such as hollow silicon microballs . This increases the effectiveness of the catalyst film 33.

In one favourable embodiment of the invention, the purification effect of the catalyst film 33 is increased by using visible light in addition to UV light. In this case, a phosphorising material that lengthens the wavelength of the UV light used is blended for instance during the production phase of the film in with the catalyst film 33 consisting essentially of titanium oxide. This increases the wavelength of e.g. 350 nm UV light to up to 500 ran.

The air purification process according to the invention is conducted for example at least as follows: initially the air for purification is ionised in the preionisation element 7, after which the air is conducted to a cold catalysis process conducted in the cold catalysis element 10, in which the air is oxidised using UV light and a suitable catalyst essentially at room temperature, and the organic material in the air is transformed into at least carbon dioxide and water

vapour. After the cold catalysis process, the air is conducted to a post-ionisation process carried out in ionisation element 13, after which the air is conducted out of the apparatus.

The air purification can be made more effective by conducting the air initially through a mechanical filter 6, after which it is conducted to the preionisation element 7. Effectiveness is increased after this by conducting the air through a UV radiation element 8 and an oxidising and sterilising ozonising element 9 to the cold catalysis process in cold catalysis element 10. The effectiveness of the process can be increased further after the cold catalysis process by passing the air through an electret filter 11, where the air's particles are ionised, and then, if needed through a HEPA filter 12 before the post-ionisation taking place in ionisation element 13, where the outgoing air is charged with negative ions.

In the method according to the invention the air purification process is monitored by measuring the composition of the incoming air with a suitable initial sensor system 27 and similarly by monitoring the composition of the outgoing air with a suitable second sensor system 28. According to the invention, the tracking data provided by the sensors are transferred for processing to an intelligent processor 29. On the basis of this processing the amount of air passing through the apparatus and/or the effectiveness of the air purification process is adjusted for example by increasing the power of fans 25 and 26 or by increasing, decreasing or turning off the power of the modular elements 6-13.

The method according to the invention is also characterised by the fact that when using an activated carbon filter in the cold catalysis element 10, the carbon in the filter is regenerated during the cold catalysis process in the element 10. The regeneration is implemented as described above, using a plasma layer created on the catalyst coating 33. Similarly,

any activated carbon filters used in other elements are regenerated during the purification process by producing ozone, for instance using UV radiation, and mixing it into the air flow.

Those skilled in the art will clearly see that the invention is not limited to the example given above, but can be varied within the scope of the patent claims given below. Therefore for example the order in which the modular elements of the apparatus are placed can be varied within certain limits. For example the electret filter can also be placed before the cold catalysis element.

It is also obvious to those skilled in the art that the number of elements in each apparatus may vary. For example, there can be several cold catalysis elements in each apparatus, placed next to each other or with other elements in between. Similarly, there can be several of the other elements in the apparatus.

Further, it is obvious to those skilled in the art that a return flow can be arranged through the apparatus, causing at least a part of the air to the purified to pass through the same apparatus more than once. In this case, the air to be purified is recycled through the apparatus until it has reached the desired level of purity, after which it is conducted out of the apparatus in specific proportions.

In addition, it is obvious to those skilled in the art that the apparatus according to the invention can be placed as a module at the inlet of air coming for example into a small building' s air conditioning so that it purifies the incoming air before it is breathed by people inside the building. Therefore it can be used to create clean-room solutions.