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EP0397856A1 - Procede et dispositif de purification d'air - Google Patents

Procede et dispositif de purification d'air

Info

Publication number
EP0397856A1
EP0397856A1 EP19900901265 EP90901265A EP0397856A1 EP 0397856 A1 EP0397856 A1 EP 0397856A1 EP 19900901265 EP19900901265 EP 19900901265 EP 90901265 A EP90901265 A EP 90901265A EP 0397856 A1 EP0397856 A1 EP 0397856A1
Authority
EP
European Patent Office
Prior art keywords
bed
air
tubes
pellets
heated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19900901265
Other languages
German (de)
English (en)
Other versions
EP0397856A4 (en
Inventor
Pawan Kumar Bassi
Kenneth Charles Eastwell
James Stephen Goudey
Mary Eileen Spencer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Alberta
Original Assignee
University of Alberta
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CA000583937A external-priority patent/CA1314383C/fr
Priority claimed from US07/277,254 external-priority patent/US5008091A/en
Application filed by University of Alberta filed Critical University of Alberta
Publication of EP0397856A1 publication Critical patent/EP0397856A1/fr
Publication of EP0397856A4 publication Critical patent/EP0397856A4/en
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665

Definitions

  • the present invention relates to a method and apparatus for removing low molecular weight hydrocarbons, such as methane, ethylene and ethane, present as impurities in air supplies.
  • Contaminated air supplies are of concern in many economic sectors, such as commercial horticulture, as well as to scientists studying growth and metabolism of plants, animals, or microorganisms.
  • Ethylene is produced by and has effects on all of them.
  • Ethylene is widely recognized as a plant growth regulator and levels less than 50 ppb in air can alter plant metabolism.
  • the role of ethylene in the ripening of climacteric fruits is well documented.
  • the post-harvest storage life of flowers and climacteric-type fruits can be extended by removing ethylene, evolved by the produce and from other sources, from the storage atmosphere.
  • Our invention provides a reliable, efficient, and safe method for obtaining hydrocarbon free air for other purposes as well.
  • Adsorbent traps are often less effective, as they have finite binding capacities and they frequently require the handling and/or disposal of toxic materials.
  • oxidative methods are preferred, including reaction with ozone, atomic oxygen, potassium permanganate or metal catalysts.
  • Ozone is a powerful oxidant but it is highly corrosive and toxic to man at low concentrations.
  • Atomic oxygen is more reactive ttian ozone towards ethylene but this approach, like reaction with ozone, requires specialized equipment and trained personnel.
  • permanganate is non- volatile, a large surface area is required to remove trace amounts of ethylene from air supplies.
  • permanganate Unlike ozone and atomic oxygen, permanganate requires special and expensive procedures for handling and disposal. Permanganate is not not reusable. In addition, this method is non-selective, dangerous and, in many cases, does not effect complete removal of hydrocarbon gases.
  • Air flow through a heated metal catalyst is an effective method of removing low molecular weight hydrocarbons.
  • Hydrocarbons are oxidized to carbon dioxide and water in the presence of the catalyst.
  • Metal catalysts are reusable and stable during extended use if provided with sufficient oxygen for regeneration and heated within specified operating temperatures. (High temperatures can damage certain metal catalysts and reduce their efficiency.)
  • the amount of oxygen required for regeneration is stoichiometrically related to the levels of hydrocarbons removed (oxidized) from the air stream. For the trace amounts of hydrocarbons present in most air supplies ( ⁇ 10 ppm) the amount of oxygen consumed is negligible. Levels of carbon dioxide produced under these conditions are also minimal.
  • the efficiency of any catalyst is largely determined by the amount of active surface area and control over catalyst temperature.
  • the active surface area can be increased by coating a suitable fibrous support material, such as asbestos, with the metal catalyst.
  • a suitable fibrous support material such as asbestos
  • On more rigid porous support materials such as aluminum oxide pellets
  • a greater active surface area can be achieved by impregnating with metal solutions containing organic solutes (fatty acids for example) that lower the surface tension and/or by infiltrating under partial vacuum. The organic solutes are then removed (oxidized) at high temperature before the catalyst is used. Both methods increase the penetration of the soluble metal into the support material thereby developing a greater active surface area.
  • Non rigid catalyst support materials such as asbestos are disadvantageous for systems with high flow rates. High flow rates may compress these materials, which will impede air flow and reduce catalyst efficiency.
  • increasing the active surface area on more rigid support materials does not, in most cases, enhance catalyst efficiency at high flow rates.
  • an object of one aspect of this invention is to provide a method and apparatus specially designed to effect the substantially complete oxidation of low molecular weight hydrocarbons at high flow rates.
  • a major factor in achieving this aim is the efficient and uniform heating of the catalyst bed, accomplished by incorporating a good thermal conductor into the catalyst bed.. More particularly, turnings made of stainless steel or other suitable metal or mixture of different metals are incorporated into the bed for this purpose.
  • Aluminum oxide in pellet form, acting as a support for the platinum catalyst also provides better heat conductivity than catalyst supports such as asbestos. Additionally, the contaminated influent air stream is also preheated before it comes in contact with the catalyst, thereby preventing uneven heating of the catalyst bed.
  • this invention provides a method of removing low molecular weight hydrocarbons from air, comprising the steps: a) preheating the air, and b) passing the preheated air through a heated catalytic bed comprising a mixture of platinized heat- conductive pellets and metal turnings.
  • this invention provides an apparatus for removing low molecular weight hydrocarbons from air, comprising: two substantially concentric tubes of heat- conductive material, the tubes being oriented substantially vertically, the tubes defining a first chamber within the innermost tube and defining a second chamber in the space between the two tubes, the two chambers being in communication at the bottoms thereof, a catalytic bed in one of said chambers, the catalytic bed comprising a mixture of platinized heat- conductive pellets and metal turnings, first means for heating the catalytic bed, second means for preheating the air, and • third means for ducting air to the top of the other of said chambers, downwardly along said other of the chambers, thence upwardly along said one chamber, thence out of the apparatus.
  • Figure 1 is a vertical sectional view through an apparatus constructed in accordance with a first embodiment of this invention
  • Figure 2 is a vertical sectional view through an apparatus constructed in accordance with a second embodiment of this invention.
  • Figure 3 is a vertical sectional view through an apparatus constructed in accordance with a third embodiment of this invention. DETAILED DESCRIPTION OF THIS INVENTION
  • Figure 1 shows an apparatus 10 consisting of a top mounting member 12, a bottom mounting member 14, and two concentric stainless steel tubes.
  • the tubes consist of an inner tube 16 and an outer tube 18.
  • the arrangement of tubes 16 and 18 is such as to define a first chamber 20 within the tube 16, and a second chamber 22 in the annular space between the two tubes 16 and 18.
  • the inner tube 16 is open at the bottom, which allows the two chambers 20 and 22 to be in communication at the bottom end of the apparatus 10.
  • outlet means 24 At the upper portion of the outer tube 18, there are provided outlet means 24 to allow air to be ducted out of the apparatus 10.
  • the inner tube 16 has, at its upper end, an inlet opening 26 through which contaminated air can enter the apparatus.
  • the arrows show the flow of air.
  • a catalytic bed 28 is provided in the second chamber 22, i.e. in the annular space between the tubes 16 and 18.
  • the catalytic bed 28 comprises a mixture of platinized aluminum oxide pellets and stainless steel turnings, although other materials could be utilized.
  • the aluminum oxide pellets are platinized by being impregnated with from about 1% to about 5% by weight of platinum chloride. This is accomplished by soaking the aluminum oxide pellets in a solution of chloroplatini ⁇ acid for several hours, pouring off the solution, then drying the pellets at 50°C.
  • cylindrical aluminum oxide pellets (5.0 mm long by 3.0 mm in diameter) to be very satisfactory, but of course other shapes and sizes can be used.
  • the ratio of stainless steel turnings (coarse, medium or fine) to aluminum pellets, oh a volume basis, can be varied from about 1:2 to about 2:1, without affecting the performance of the purification apparatus. A ratio of approximately 1:1 is preferred for the high flow rates that would be used ,in commercial applications.
  • the stainless steel turnings provide more efficient and uniform heating of the catalyst, and afford greater rigidity to the catalyst bed, than is provided by the pellets alone held in place by their own weight.
  • the catalyst bed must remain substantially stationary, particularly at high flow rates, in order to maintain the desired catalyst temperature and prevent damage to the pellets which otherwise may clog the outlets and impede air flow.
  • the probability of movement within the catalyst bed becomes greater when the turnings content of the bed drops below about 33%, even though the device will continue to function. This is due to the fact that the turnings provide structural support and rigidity for the bed, as already mentioned.
  • Means are provided for preheating the contaminated air before it comes into contact with the catalytic bed 28.
  • preheating is accomplished by conveying the impure influent air stream down the centre of the inner concentric tube 16 which is located in the centre of the catalytic bed 28.
  • the desired temperature is obtained by placing heating elements 30, regulated at the desired temperature, on the external surface of the outer concentric tube 18. These heating elements 30 can be uniformly distributed around the periphery of the tube 18, and are of known construction.
  • the hollow portions of the apparatus 10, particularly the first chamber (that within the inside tube 16) can be loosely packed with stainless steel turnings (coarse, medium or fine) .
  • the catalytic bed 28 is preferably heated to a temperature between about 300 ⁇ C and 350 ⁇ C.
  • operating temperatures below 300 ⁇ C. can be used to remove only the more reactive hydrocarbons such as ethylene. More particularly, it has been found that the temperature below which ethylene will not be removed in the device disclosed herein is about 160 ⁇ C, as measured on the external surface of the device at the midpoint of the catalyst bed.
  • the external heating elements 30' are shown to be smaller than the equivalent heating elements 30 shown in Figure 1.
  • the preheated impure influent air travelling down the internal tube 16' reverses its direction at the bottom and flows up through the concentric outer tube 18 containing the catalytic bed 22', where low molecular weight hydrocarbon impurities are removed by being oxidized in the presence of the platinum catalyst.
  • the purified air then exits through outlets 24 shown at the top of the outer tube 18.
  • Figure 3 shows an arrangement in which the air flow is reversed from that of the first two embodiments.
  • a catalytic bed 40 is provided within the inner concentric tube 42, and impure air is directed inwardly through one or more inlets 44 located at the top of the outer concentric tube 46.
  • the first chamber located inside the inner tube 42 is in communication at the bottom with the second chamber located in the annular space between the two tubes.
  • air arriving at the bottom of the second chamber passes radially inwardly, thence upwardly through the catalytic bed in the inner tube 42.
  • Heating of the apparatus is accomplished by heating elements 48 which are located on the external surface of the inner concentric tube 42 in the figure. Alternatively, the heaters may be located on the inner or outer surface of the outer concentric tube 46. Purified air exiting from the bed 40 is removed from the apparatus through the top end 50 of the inner tube 42. Preferably, all versions of the entire device are enclosed in a high temperature heat insulation and encased in a stainless steel jacket (not illustrated) . The temperature can be controlled with a rheostat by regulating the voltage applied to the heaters. A thermocouple placed between the external heater and the outer steel tube 5 cm from the bottom of the reactor vessel can be used to monitor temperature.
  • the detection limit for each hydrocarbon was 0.05 ng.
  • levels of methane, ethane, and ethylene in the air supply ranged from 6.9 - 8.2, 0.100 - 0.200, and 0.010 - 0.020 ppm respectively.
  • Methane is less reactive than both ethane and ethylene and requires a higher temperature for complete oxidation. Consequently the optimum operating temperature at each flow rate was defined as the temperature required to remove all traces of methane.
  • the performance of the test apparatus was stable during extended use, when operated in accordance with the conditions defined. No loss of efficiency was detected after 10 months of continuous operation at temperatures between 300 and 350°C, and at a space velocity of 10,000 catalyst bed volumes per hour. Less than 0.25 kW h"-- are.required to operate the device under these conditions.
  • the apparatus When encased in the high temperature heat insulation, the apparatus is safe to handle during operation, and can be used in confined areas such as growth cabinets.
  • This purification device has been used to remove hydrocarbon contaminants from air supplies for biochemical and physiological studies on isolated tissues, seeds, and intact plants. In addition, we have used the device to obtain hydrocarbon- free air for gas chromatography.
  • cylinders of compressed air contain hydrocarbon impurities at levels that can interfere with the analysis of gas samples, and here again the device of the present invention can find use. It can also be employed to remove hydrocarbons from air supplied to storage chambers containing horticultural products. Since ethylene is known to accelerate senescence and fruit ripening, ventilating storage chambers with hydrocarbon- free air would prolong the storage life of flowers and climacteric-type fruits. Also, the chamber air could be recirculated through the device to remove hydrocarbons. The device can be used to provide hydrocarbon-free air for other purposes as well. GENERAL DISCUSSION
  • a greater platinum content (5% by weight) and/or pressurization of the reactor vessel is required.
  • the reactor vessel can be pressurized by reducing the aperture of the outlet or outlets.
  • higher flow rates can reduce the efficiency of heat exchange.
  • a cooling trap/coil wrapped around the effluent line or a heat exchanger in the effluent line could be used to cool down the purified gas stream to desired temperatures.
  • the apparatus described herein can be operated at lower temperatures and at substantially higher flow rates (space velocity of 10,000 catalyst bed volumes per hour at 300 to 350"C) than normal for devices of this type. These low temperatures will not produce biologically active levels of nitrous oxides or ozone, which are of great concern in biological studies.

Landscapes

  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Catalysts (AREA)

Abstract

On extrait des hydrocarbures de faible poids moléculaire de l'air en préchauffant l'air (30) et en le faisant passer à travers un lit catalytique (28) comprenant un mélange de pastilles platinées thermo-conductrices et de copeaux métalliques. Les copeaux garantissent la rigidité structurelle et l'échauffement uniforme du lit, et permettent de réduire la consommation d'énergie requise pour maintenir le lit à la température désirée.
EP19900901265 1988-11-23 1989-11-22 Method and apparatus for purifying air Ceased EP0397856A4 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CA583937 1988-11-23
CA000583937A CA1314383C (fr) 1988-11-23 1988-11-23 Methode et appareil de purification d'air
US07/277,254 US5008091A (en) 1988-11-29 1988-11-29 Method for purifying air
US277254 2002-10-22

Publications (2)

Publication Number Publication Date
EP0397856A1 true EP0397856A1 (fr) 1990-11-22
EP0397856A4 EP0397856A4 (en) 1991-05-15

Family

ID=25672245

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900901265 Ceased EP0397856A4 (en) 1988-11-23 1989-11-22 Method and apparatus for purifying air

Country Status (2)

Country Link
EP (1) EP0397856A4 (fr)
WO (1) WO1990005577A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8902250A (nl) * 1989-09-08 1991-04-02 Veg Gasinstituut Nv Werkwijze voor het uitvoeren van een chemische reactie en daarbij te gebruiken reactor.
FR2699831B1 (fr) * 1992-12-30 1995-02-03 Berger Produits Dispositif d'épuration d'air, notamment de désodorisation, par destruction catalytique des espèces organiques présentes dans l'air à épurer.
US5482685A (en) * 1993-04-12 1996-01-09 Matsushita Electric Industrial Co., Ltd. Deodorizing apparatus
GB9420481D0 (en) * 1994-10-11 1994-11-23 Taylor Research & Dev Ltd Analysis of gas emissions
EP2228122B1 (fr) 2009-02-25 2012-08-15 K.M.W.E. Management B.V. Procédé et réacteur pour l'élimination de VOC de flux gazeux

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3025132A (en) * 1959-08-07 1962-03-13 American Cyanamid Co Method of oxidizing hydrocarbon constituents of exhaust gases
GB953216A (en) * 1960-05-16 1964-03-25 Lorraine Houilleres Improvements in and relating to the method of purifying gas
US3167400A (en) * 1962-07-30 1965-01-26 Norris Thermador Corp Catalytic converter
US3607131A (en) * 1969-02-05 1971-09-21 Us Navy Catalytic air purifier
DE2401204A1 (de) * 1974-01-11 1975-07-17 Marquardt Peter Katalytischer abgasreaktor fuer verbrennungsmotoren
US4138220A (en) * 1978-02-13 1979-02-06 Colonial Metals, Inc. Apparatus for catalytic oxidation of grease and fats in low temperature fumes
PL123101B1 (en) * 1979-09-12 1982-09-30 Polska Akademia Nauk Instytut Katalizy I Fizykochemii Powierzchni Method of storage of garden produce preserving freshness
DE3042843A1 (de) * 1979-12-21 1981-07-02 USS Engineers and Consultants, Inc., 15230 Pittsburgh, Pa. Verfahren und vorrichtung zur katalytischen oxidierung von verunreinigungssubstanzen in einem abgasstrom
FR2479323B1 (fr) * 1980-03-31 1987-03-20 Johnson Matthey Plc Procede et dispositif anti-pollution pour gaz d'echappement de moteur a combustion interne a turbo-compresseur
GB2163637A (en) * 1984-08-31 1986-03-05 Johnson Matthey Plc Removal of ethylene from fruit and vegetables stores by catalytic combustion
US4867949A (en) * 1985-07-25 1989-09-19 Betz Erwin C Heat recuperative combustion device

Also Published As

Publication number Publication date
EP0397856A4 (en) 1991-05-15
WO1990005577A1 (fr) 1990-05-31

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