Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
  • A62B29/00—Devices, e.g. installations, for rendering harmless or for keeping off harmful chemical agents

Definitions

• the present invention relates to an air purifying apparatus for human respiration, this purification being obtained by elimination of toxic compounds and odors.
• the combination of the different parts that make it up produces clean air which can be used inside buildings but which can also be used to renew the air in polluted streets or neighborhoods.
• This device has the characteristic of being able to be installed close to the people who use it and it is also designed to be installed on very transited and / or very polluted streets.
• This invention underlines that, by the combination of different means, one can simultaneously obtain a significant reduction in the volume of the apparatus, its energy consumption and its investment cost and, consequently, obtain a system at low cost. which can be installed near people (house, automobile, school, business, etc.).
• this significant reduction in costs makes it possible not only to design a low-cost household appliance, but also an appliance capable of purifying large air flows in city streets.
• the devices according to the invention can purify air flows between 20 m3 / hour and 20,000 m3 / hour and the principles of their construction are identical in these two extreme cases.
• ozone can be destroyed at 70 ° C and that carbon monoxide and reactive hydrocarbons can be destroyed at temperatures of the order of 240 ° C. Saturated hydrocarbons are burned at temperatures above 300 ' C but in the case of the depollution of the ambient air, it is not necessary to eliminate these hydrocarbons which are not toxic and are not either precursors of compounds of the ozone type.
• a fan (1) fitted with a filter (2) intended to remove dust, suspended particles, etc., blows the air to be purified coming from the street or from the building itself, in a system of pipes, tees and elbows, equipped with two or more solenoid valves (3) which, by the action of a cyclic programmer (11) allow this air to be introduced into one or other of the two reactor inlets.
• the air enters at (4) into the reactor and exits at (5).
• the air enters (5) and leaves (4).
• the reactor mainly consists of three parts:
• the element (6) is the catalyst, of the type mentioned in the foregoing or, preferably, of the type mentioned in the following.
• air at room temperature enters (4) it preheats in section (7) to a temperature close to that of the reactor (approximately 220 ° C).
• the section (8) At the exit of the section (6), it enters the section (8) in which it gives up its sensible heat which thus remains stored (accumulated) in the lining.
• section (8) serves as an air preheater and section (7) as a cooler.
• the exchange sections have a very long length, which obviously is not economical (large volume and high pressure drop).
• the outlet temperature in (5) is therefore necessarily higher than the inlet temperature in (4). Consequently, the apparatus according to the invention is at the same time a purifier and an air heating apparatus and even, with a very efficient heat exchange system like that claimed in the invention, a contribution of thermal energy must be provided to compensate for the inefficiency of the heat exchanger.
• FIG. 1 indicates the method recommended in the invention for introducing this electrical energy into the system.
• the operation of the device is completely electric (fan, solenoid valves and heating energy).
• An electrical resistance (9) is placed in the middle of the catalyst bed to provide the heat necessary for the operation.
• This resistor (9), connected to the general switch of the device (common to the fan motor, to the programmer and to the resistor) is kept active during the preliminary warm-up period and during the actual operation ( pseudo-stationary regime) and this with the same intensity of electric current.
• the temperatures of the catalyst (6) and of the linings increase to stabilize, after a certain number of cycles, at the temperatures chosen during the design of the device.
• the essential property of the device according to the invention is to minimize the supply of energy to the resistor (9) and to the fan (1) without prejudice to the purification and without increasing the investment cost.
• the heat exchange system (sections 7 and 8) must satisfy the following conditions: a) Increase in the efficiency of heat exchange through the use of a lining of large specific surface (square meters of surface per cubic meter of lining). This can only be achieved by the use of small diameter metal wires of a relatively stainless material.
• the efficiency of a packing is defined in scientific terms, by the NTU (Number of Transfer Units), that is to say Number of Transfer Units, per unit of length. For the same length of the lining, the heating and cooling will be greater the greater the value of the NTU.
• Ts Average air temperature at the outlet of the device
• Te is also the temperature of the air leaving the fan.
• Ts is the average temperature of the air leaving during a half cycle: for example, this temperature can rise from 20 'C at the start of the half cycle, to 30 "C at the end of this half cycle. is the outlet temperature of the catalyst and therefore, of entry into the section of the cooling lining.
• Te can be chosen close to 250 ° C for so-called "high temperature” devices and 80 'C for those called
• catalysts based on Palladium or Silver can have a very high activity at relatively low temperatures: the operating temperature of the catalyst will always be chosen such as to allow it to operate in the regime called external diffusion regime that is to say that it is not the catalytic activity which defines the efficiency of the catalytic bed but the transfer of material in the gas situated at the periphery of the catalyst particles.
• Palladium catalysts were thus obtained by electrochemical deposition on metallic copper fabrics of high volume porosity (90%).
• the wires used in the manufacture of these fabrics preferably have a diameter of about 0.1 mm. As the illustrative examples show, the depollution efficiency is very high.
• the thickness of the electrochemical deposit was 300 Angstroms.
• the device is fitted with a soil ides particle filter
• Poisoning of the catalyst is therefore relatively slow.
• the catalyst (type PC 163 from the company PROCATALYSE) consists of spherical particles with an average diameter of 0.32 cm. The density of these particles is such that the mass of the catalytic bed is 2.9 kg. At 220 ° C, with the air flow rate mentioned above, the pressure drop across the catalytic bed is 3.5 cm - water.
• the linings are made up of a metallic fabric woven from aluminum wires, of around 17 mesh. The wires have a diameter of 0.17 mm and the space between two wires is 1.6 mm. Circular discs 30 cm in diameter are cut from the wire mesh and with these stacked discs, the accumulators 7 and 8 are formed. The length of each section is 15 cm. Two diffusers (10) comprising a large number of small calibrated orifices make it possible to distribute the air flow regularly over the entire section of the lining. The porosity of the packing is 90%. The weight of each section is 2.9 kg.
• each packing section In normal operation, the pressure drop of each packing section is 7 cm - water to be needed add 1 cm - pressure drop water from the diffuser.
• the reactor is thermally insulated using a 5 cm thick layer of glass wool (12).
• the resistor (9) can provide 250 watts.
• the programmer (11) positioned to obtain a 1 minute cycle (at each cycle, the two solenoid valves are reversed twice) the operation is started and the progressive increase in temperature indicated by the thermocouple (13) located is observed. in the middle of the catalyst bed. After 25 minutes of operation, this temperature remains practically constant and equal to 220 ° C.
• the consumption of the fan motor is 250 watts and this energy is to be added to the 250 watts consumed by the resistor (9), which means that the air passing through the device undergoes an average temperature increase d 'around 9 degrees Celsius.
• This relatively warm air is quickly mixed with the colder air in the apartment or house; anyway a heat input of 500 watts does not heat more than 1 or 2 ° C a house whose surface is between 100 and 200 M2 and we can therefore say that the device works well as a purifier and not not as a heater.
• This device can be called "high temperature" (220 'C). Under these operating conditions (temperature, air residence time in the catalytic bed) the conversion of ozone is very large (the concentration decreases from 1 ppmv (parts per million by volume) to less than 0.05 ppmv ) as well as that of carbon monoxide (from 5 ppmv to 0.5 ppmv) and of a typical reactive hydrocarbon (from 1 ppmv to less than 0.05 ppmv in the case of toluene). The efficiency of this industrial catalyst therefore conforms well to that indicated by its manufacturer and this is not the subject of the present invention.
• the programmer of the apparatus of example 1 is set to 6 cycles per hour. To maintain the temperature at 220 "C, it is necessary, through the use of a transformer, to increase the power consumed in the resistance up to 450 watts.
• This comparative example shows another advantage of the operation with short cycles. With 6 cycles per hour, as in Example 2, the catalyst can be kept at
• This comparative example illustrates the advantage associated with the use of high porosity metallic fabrics.
• 50 mesh aluminum foils consisting of 0.2 mm wires, porosity 0.67 and reducing the length of the linings to 6 cm
• the power required to maintain the catalyst at 220 ° C is still equal to 250 watts (same efficiency as in Example 1).
• the pressure drop of each filling is equal to 12 cm-water.
• This comparative example illustrates the advantage associated with the use of metallic fabrics of good conductive metals.
• the heat exchange is less efficient: the efficiency goes from 98% to 95.8%.
• the specific densities and heats of aluminum and glass are approximately equal, but the thermal conductivities of the two materials are very different (that of aluminum is 200 times greater than that of glass), this result shows that the radial conduction of heat in the same trim portion contributes to increasing the efficiency of the lining and reducing the effect of the poor distribution of air at the inlet of the lining.
• any lining not made up of metal wires oriented perpendicular to the axis of the apparatus will be less effective. This would be particularly the case with metallic or ceramic particles for which the radial conduction is weak and due only to the points of contact of the particles with each other.
• the length of the linings of Example 1 is reduced from 15 to 8 cm and the power consumed by the resistor (125 watts) is also reduced by half, which results in a catalyst temperature equal to 70 ° C.
• the pressure drop in each packing is 3.7 cm and in the catalyst bed 2.6 cm.
• the power consumed by the motor is 150 watts.
• a catalyst without internal porosity constituted by metallic wires with the catalytic metal electrochemically deposited on the surface of these wires.
• the catalytic lining is in every way similar to the lining of heat recovery and its efficiency, that is to say, its catalytic efficiency defined in this case as the ratio of the transfer of material to the pressure drop will be very high if the porosity of the catalytic lining is large (greater than 70% ). Reducing the size of the wires (diameter less than 0.5 mm) also makes it possible to reduce the amount of support metal. However, it is obvious that the weight of the support metal or the pressure drop of the fiber or canvas bed are not determining factors in the investment cost or the operating cost of the device.
• the main gain resulting from the use of these electrochemically coated catalysts is the low cost of the manufacturing process and the fact that they are thermally stable without the additives that are used with the porous catalysts in order to avoid sintering of the metal particles deposited in the pores.
• This new catalyst in a preliminary operation, is conditioned at 600 ° C. for 14 hours in a mixture of 1% methane, 4% oxygen and 95% nitrogen (cf. method of Briot and Primet, Applied Catalysis, 68 (1991) P. 301-314).
• Example 9 With the aluminum cloths of Example 7 but using a silver covering (thickness: 300 Angstroms), polluted air containing 1 ppmv of ozone and 10 ppmv of carbon monoxide is treated. The temperature of the catalyst is maintained at 90 ° C. using the electric transformer. The ozone conversion is more than 90% but the carbon monoxide is only slightly transformed.
• This low temperature system based either on palladium or on Silver, should make it possible to treat large flows of polluted air at a very low cost, by optimizing the total electrical consumption (in the resistance and in the motor).

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• Health & Medical Sciences (AREA)
• Pulmonology (AREA)
• General Health & Medical Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)

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Citations (3)

• 1992
  • 1992-07-16 MX MX9204170A patent/MX9204170A/es unknown
• 1993
  • 1993-07-06 AU AU45057/93A patent/AU4505793A/en not_active Abandoned
  • 1993-07-06 AT AT93914817T patent/ATE150653T1/de not_active IP Right Cessation
  • 1993-07-06 WO PCT/FR1993/000693 patent/WO1994002207A1/fr active IP Right Grant
  • 1993-07-06 DE DE69309248T patent/DE69309248T2/de not_active Expired - Fee Related
  • 1993-07-06 EP EP93914817A patent/EP0607379B1/fr not_active Expired - Lifetime

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