Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
  • B01D46/0052—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with filtering elements moving during filtering operation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/75—Multi-step processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/88—Handling or mounting catalysts
  • B01D53/885—Devices in general for catalytic purification of waste gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2279/00—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses
  • B01D2279/40—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses for cleaning of environmental air, e.g. by filters installed on vehicles or on streets
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
  • Y02A50/2351—Atmospheric particulate matter [PM], e.g. carbon smoke microparticles, smog, aerosol particles, dust

Definitions

• the present invention relates to an apparatus and a process that allow purification, with a minimum expenditure of energy, of an appreciable amount of air in a metropolitan environment polluted with carbon, nitrogen and sulphur oxides, as well as with particles of dust and smog.
• the apparatus is designed and built in a size suitable for transportation on a vehicle travelling the streets of a town or city.
• a particularly suitable type of vehicle for this purpose is a public transport vehicle for transport by road or rail, capable of purifying an appreciable amount of air during its day-to-day working cycle while consuming a low amount of energy and using low cost chemical reagents.
• the International Patent Application No. WO 9755 describes an apparatus for treatment of air transported by a vehicle, and containing a filter system made up of a series of electrostatic filters to retain the ionised particles contained in the air.
• This system is incapable of acting on the gaseous chemical pollutants, and involves excessively frequent removal and/or maintenance of the filters.
• Catalytic systems are also known, and are used for catalytic post-combustion of the products of combustion, to purify them of unburned solids.
• these systems are applied to gaseous fluids with a high concentration of combustion products, and are only active at a temperature much higher than that of the surrounding environment, which means that a notable consumption of energy is required specifically for the purpose.
• washing filters and tunnels in comparison with the working flow rate of air to be treated and the concentration of fine dust, require the use of excessive amounts of space when compared with that available in case of application on a vehicle, and the same thing can be said for the amount of washing liquid used for j - purification, which, according to the current dimensions of these devices, would involve the need to load the vehicle with large amounts of liquid.
• the present invention provides a mobile apparatus on a transport vehicle and a related purification process that performs a cleaning operation which does not require large amounts of liquid or employ large amounts of space, and which is such that it offers the advantages typical of dynamic filters in combination with those typical of washing tunnels, without involving the problems indicated above.
• An object of the present invention is therefore a mobile apparatus for the purification of polluted air in a town environment installed on a transport vehicle, characterised in that it comprises: an inlet section for the air to be purified; an oxidisation section following said inlet section, to oxidise CO into C02 and nitrogen oxides NO x into N0 2 by means of the action of nascent oxygen and a catalyst active at least at room temperature based on an oxide of a metal selected from the class consisting of the first series of the transition group of the Periodic System or on cupric chro ite; a washing section following said oxidation section to purify the air from said higher carbon and nitrogen oxides and from so 2 ky reaction with hydroxyl ions deriving from lime or sodium bicarbonate or a mixture thereof in solution in an aqueous washing solution to obtain insoluble salts and to reduce nascent oxygen or residual ozone by means of a catalytic filter, as well as particles, dust and unburned substances; an apparatus for separation of said insoluble
• figure 1 is a general view of the apparatus installed on an urban transport vehicle
• figure 2 is a plan view of the apparatus according to the present invention
• figure 3 is a partly cut-away view of an embodiment of the apparatus of figure 2.
• FIG. 1 A typical application for the present invention is illustrated in figure 1.
• a vehicle 1 carries on its roof a purification apparatus 2 according to the invention.
• the vehicle 1 is typically an urban transport vehicle that travels the town roads during its working day, which can be calculated to last around 10 hours.
• the apparatus 2 is a module capable of treating an air flow rate of around 2000 m 3 /hour it can be calculated that each urban transport vehicle can purify 20000 m 3 of air per working day in each module installed.
• the apparatus according to the invention has an energy consumption of approximately 3 kWh
• a vehicle 1 equipped as indicated above produces an amount of purified air during the day that is greatly in excess of the pollution produced by the vehicle itself, and with minimum energy costs compared with the energy produced by the vehicle to move itself.
• It comprises an inlet section 3 for the air, served by a suction feeder 16 provided with traps for leaves and other foreign bodies, in which a fan 4 feeds the flow of air to be treated, at a relatively low speed, into an oxidation section 5.
• the air then accelerates inside a washing section 6, passing through a series of labyrinths within which the air is made to pass through several barriers of chemically activated water. From here, the flow of air slows down in an accumulation section 7 or stilling pool, where any water that may have been carried in is separated from the air before the latter is finally returned to the surrounding environment.
• the fan 4 can also be situated, for example, downstream of the oxidation section 5, without altering the process.
• the oxidation section has the aim of transforming the carbon monoxide CO into CO2, and the nitrogen oxides NO x into N0 2 , so that these oxides, and in particular N0 2 , are able to react in the washing section 6 with chemical reagents capable of transforming them into insoluble products that can be precipitated and separated off.
• the oxidation of the polluting oxides mentioned above is obtained by the action of nascent oxygen.
• the nascent oxygen is generated by the decomposition of ozone produced in the oxidation section.
• the ozone is produced during the passage of air over a group of lamps capable of producing ultraviolet light with a wavelength of below 250 millimicron.
• the concentration of NO is three times lower than that of CO, so that it is advisable to size the process according to the amounts of CO to be treated.
• the emission of ozone into the atmosphere is to be avoided and considering the positive effect of the subsequent washing, it is preferred to use a limited number of UV lamps.
• the ozone or the nascent oxygen could also be produced by means of other physical or chemical processes, for example the formation of high voltage electric discharges.
• the washing chamber and the accumulation chamber immediately beyond the oxidation section are sized in such a way as to provide for reduction of any ozone remaining after the oxidation process into oxygen. This is also the case in the event of accidental stoppage of the washing system, as the residual ozone is consumed by oxidising the catalytic surfaces, and also because a flow meter is installed in the washing system and, in the absence of flow, this prevents the ultraviolet lamps 8 from turning on.
• the state of the art essentially proposes catalytic oxidation based on catalysts preferably made up of precious metals such as platinum, cobalt and the like, which are activated at high temperatures.
• the oxidation is preferably promoted by a catalytic bed 9 which is active at room temperature, said bed comprising one or more catalysts selected from the oxides of a metal of the class belonging to the first series of the periodic table transition group.
• a catalytic bed 9 which is active at room temperature, said bed comprising one or more catalysts selected from the oxides of a metal of the class belonging to the first series of the periodic table transition group.
• Particularly preferred because of their low cost and high yield are ZNO, Mn0 2 , CuO, as well as the copper chromite CuCr 2 ⁇ 4.
• the same catalysts promote decomposition of the residual ozone and, in order to prevent the latter from reaching the external atmosphere, the same catalysts can also be present in the successive washing and accumulation sections.
• Reduction of S0 2 , N0 2 and C0 downstream of the oxidation section 5 takes place mainly in the washing section 6, by intimate contact and reaction with a chemically activated washing liquid made up of an aqueous solution containing hydroxyl ions from substances such as lime, sodium bicarbonate or the like, which by reacting with the polluting oxides produce insoluble salts that are separated by means of filtration or precipitation.
• a chemically activated washing liquid made up of an aqueous solution containing hydroxyl ions from substances such as lime, sodium bicarbonate or the like, which by reacting with the polluting oxides produce insoluble salts that are separated by means of filtration or precipitation.
• calcium nitrate is obtained from nitrogen oxides, calcium carbonate from carbon monoxide, and calcium sulphite from sulphur monoxide, or the corresponding carbonates obtained from the decomposition of bicarbonate to carbonic acid.
• the washing section is made up of a labyrinth within which the air follows a route with a series of brusque 180° inversions of direction accompanied by an equal number or double the number of washing barriers.
• Section 6 is in fact subdivided by a series of walls 10 that form a serpentine-shaped route, while a battery of nozzles 11 spray the washing liquid onto the metal walls, generating an atomisation that promotes contact between the liquid phase and the gaseous phase and also produce a series of liquid barriers to passage of the air.
• the washing liquid collects on the bottom of the section 6 and is sent to a recycling circuit comprising a filter apparatus 12 and following this a settling chamber 13 from which the liquid is picked up by a pump 14 and recycled to the nozzles 11.
• the settling chamber 13 is served by a supply device 17 which restores the hydroxyl ions to the desired concentration, measured by means of a pH-meter.
• the washing operation does not merely perform the process of chemical reduction of the concentration of sulphur, nitrogen and carbon oxides, but also acts as a highly effective filter to reduce particulate and unburned hydrocarbons, due to the mechanical drag produced by the washing barriers and the rapid changes in direction of the route.
• the purified flow of air which is still rich in atomised water particles, passes into the accumulation section 7 or stilling pool, where the increase in the flow section slows down the mass flow rate of air, allowing precipitation of the drops, which collect on the bottom of the bath.
• a final filter 15 preferably catalytic, which helps to retain the liquid phase in the apparatus and reduce any residual ozone until the concentration is brought down to zero, as well as protecting against the entry of foreign substances from the outside, the purified air is returned to the atmosphere.
• a modular unit of the apparatus according to the present invention which merely as an example, in order to treat an air flow of around 2000 m 3 /hour is made up of a washing section formed by a parallelepiped of 500 by 1000 mm within which an air passage approximately 4 m long is formed, with between five and eight 180° inversions of direction and between 10 and 16 washing barriers.
• Example 1 A description will now be given of certain embodiments, with the process data found during operation of the apparatus. Example 1
• An apparatus is built with a suction funnel 16 with a size of 520 x 890 x 500 mm and a centrifugal fan having the following characteristics: capacity: 1960 m 3 /hour hydraulic head: 195 mm of water power consumption: 1.5 kW motor: three-phase asynchronous belt transmission vertical axis to limit bulk.
• the fan discharges into a diffuser sized in such a way as to reduce the speed of the air at the entry into the subsequent oxidation section and to reduce the load loss.
• the oxidation section is sized in such a way as to optimise load loss, bearing in mind the presence of the obstacle formed by the ozonization lamps.
• the washing section was built with passage through five separate water barriers, each one obtained by means of five spray nozzles of the type Hl/4 W11001 which allow a 110° aperture.of the jet at 3 bar giving a total flow rate of all 25 nozzles equal to approximately 10 litres/minute.
• the total load loss through the circuit was approximately 5.25 kg/cm 2 .
• the re-cycling pump 14 had a prevalence of approximately 10 kg/cm 2 to provide a flow rate of approximately 10 litres/minute, with a power consumption of approximately 0.4 kW.
• the UV lamps numbered 8 each of which was capable of producing approximately lg/hour of ozone.
• the apparatus when tested in the most severe conditions foreseen for operation, corresponding to an environmental temperature of 35°C and a relative humidity of 30%, showed a consumption of washing water of 7 litres/hour, a corresponding consumption per hour of aqueous lime equal to 50 g/hour and a consumption of bicarbonate of 500 g/hour.
• Example 2 The apparatus described in the preceding example 1 was made to undergo testing as follows.
• a chamber Upstream of the apparatus a chamber was installed with a volume of approximately 1.5 m 3 , made of anodised metal plate, within which varying ratios of clean air from the environment were mixed with the exhaust fumes from a 4000 cm 3 diesel engine running at a constant speed. From this chamber the polluted and mixed air was sucked by the fan, on the outlet of which a probe was installed to pick up samples of polluted air (upstream of the treatment) . A second probe was installed downstream of the oxidation section in order to pick up samples of oxidised air before it undergoes washing.
• a third probe was installed downstream of the device in the stream of treated air leaving it.
• NOx (NO+N0 2 ) average level 5 ppm, reduction 60% (3 ppm)
• Residual ozone at outlet traces, ⁇ 0.1 mg/m 3
• Flow rate of treated air 1890 mm 3 /hour
• Energy consumption ⁇ 2.8 kWh
• Water consumption ⁇ 7 litres/hour
• Duration of bath over 24 hours of continuous running.
• a test on a prototype apparatus according to the invention as described in Example 1 was conducted by technical staff of ENEA (Italian Authority for New Technologies, Energy and Environment) with a pair of laboratory test apparatuses of their own and with data processed by a pair of Microwax computers.
• the test apparatuses were of the current mobile type used for tests on environmental pollution and the tests were carried out in a two-day scheduled program.
• a metal chamber with a volume of 4 cubic meters was installed, in which polluted air was produced artificially by dilution into the environmental air of the exhaust from a diesel motor and an operation controlled motor.
• the dilution was controlled in such a way as to obtain a concentration of pollutants comparative with the characteristics of town smog.
• a sensor mounted at the inlet of the purification apparatus took up polluted air continuously before treatment in the purification apparatus. This gas was directed to one test apparatus. Another sensor identical to the first one mentioned above took up air at the outlet of the purification apparatus, and this was directed to the second test apparatus.
• the two test apparatuses were identical and with exactly the same calibration.
• the apparatus illustrated in the examples has been designed as a free standing modular unit for application on a vehicle not specifically designed for the purpose, but it is understood that the apparatus may also be constructed during the manufacturing cycle of the vehicle itself as an integral part thereof.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Analytical Chemistry (AREA)
• Biomedical Technology (AREA)
• Health & Medical Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Exhaust Gas After Treatment (AREA)
• Treating Waste Gases (AREA)
• Catalysts (AREA)
• Filtering Of Dispersed Particles In Gases (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1994
  • 1994-02-18 IT ITRM940085A patent/IT1272176B/it active IP Right Grant
• 1995
  • 1995-02-14 WO PCT/IT1995/000019 patent/WO1995022395A1/en not_active Application Discontinuation
  • 1995-02-14 JP JP7521705A patent/JPH08508448A/ja active Pending
  • 1995-02-14 PL PL95310412A patent/PL310412A1/xx unknown
  • 1995-02-14 HU HU9502144A patent/HUT77994A/hu unknown
  • 1995-02-14 AU AU18224/95A patent/AU1822495A/en not_active Abandoned
  • 1995-02-14 EP EP95909938A patent/EP0695212A1/en not_active Withdrawn

Non-Patent Citations (1)

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