US3718440A - Regenerative afterburner for air pollution elimination - Google Patents

Regenerative afterburner for air pollution elimination Download PDF

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Publication number
US3718440A
US3718440A US00110279A US3718440DA US3718440A US 3718440 A US3718440 A US 3718440A US 00110279 A US00110279 A US 00110279A US 3718440D A US3718440D A US 3718440DA US 3718440 A US3718440 A US 3718440A
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disk
duct
gas
wheel
afterburner
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Expired - Lifetime
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US00110279A
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English (en)
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Pegg R Foster
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/26—Construction of thermal reactors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/36—Arrangements for supply of additional fuel
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S55/00—Gas separation
    • Y10S55/30—Exhaust treatment

Definitions

  • ABSTRACT An afterburner including a regenerator disk having passages therethrough disposed over the combustion chamber, means slowly rotating the disk, a inlet duct having a first rigid seal extending completely about the periphery of the upper surface of the disk, and an exhaust duct extending through the inlet duct, the duct chamber having a second seal extending about a sector of the upper surface of the disk within the first seal.
  • BACKGROUND OF THE INVENTION Incineration of gaseous contaminants can serve to accomplish many of the desirable objectives in air pollution control and produce other beneficial results. For example, odor problems created by-rendering plants, kraft pulp mills, baking oven operations, and by the release of mercaptans from different industrial processes can be eliminated with the proper application of flame incineration equipment. The opacity of the gaseous products emitted from coffee-roasting operations, paint-baking ovens, smokehouses and diesel engines can be reduced. Hydrocarbon emissions from numerous operations such as paint-spray booths, storage tank vents, and internal combustion engine exhausts can be burned to carbon dioxide and water vapor with afterburning equipment. For complete corn bustion of organic vapors and gases or flamable liquids and even solids to take place, it is necessary that materials to be burned react with oxygen at a sufficient temperature and for a sufficient length of time for the reaction to be completed.
  • Combustible gases that are to be completely burned must be elevated to a temperature above their minimum ignition temperature in the presence of oxygen.
  • Minimum ignition temperatures vary from 580F for acetylene to 1,170F for methane. Under ordinary circumstances, however, atemperature of l,500F in the presence of excess air will destroy almost any organic material or aerosol. The general range of temperatures utilized successfully in afterburner devices is 1,200 to 1,500F.
  • Oxygen is required for complete combustion. Typically, when incomplete combustion occurs, an air pollution problem is not solved; it is aggravated. Complete combustion is achieved when sufficient air is supplied to enable the theoretical quantity of oxygen to intermix with the vapor to be burned. Excess air is provided to make certain that more than the stochiometric quantity of oxygen is provided. Also, the time factor, referred to as residence time or retention time in the combustion device, is most important if complete combustion is to take place.
  • FIG. 1 is a side view of a single disk afterburner unit according to this invention.
  • FIG. 2 is a longitudinal vertical section through a fragment of the upper portion of the unit of FIG. 1;
  • FIG. 3 is a top view of a multi-disk afterburner
  • FIG. 4 is a longitudinal vertical section taken on line 4-4 of FIG. 3;
  • FIG. 5 is a longitudinal vertical section through a fragment of the disk shaft and the bearing assembly therefor;
  • FIG. 6 is a top view of a regenerating disk showing areas through which gases may pass in the device of this invention
  • FIG. 7 is' a top view of a fragment of a regenerative disk.
  • FIG. 8 is a top view of a fragment of a wall of an inlet chamber showing a manifold extending therethrough over a fragment of a-disk.
  • the regenerative afterburner of this invention has a compressor or fan 10 driven by a 50 h.p. motor 11 by the belt and pulley drive 12.
  • Duct 13 of fan 10 receives contaminated gases at 500F at ambient pressure and compresses them to about 27 inches of water to pass them through ducts l4 and 15 which lead to the combustion chamber 16.
  • Chamber 16 has a metal shell 17 lined with refractory material 18 and supported by the legs 19.
  • Inlet duct 20 is connected to duct 15 and disposed over the entire top of combustion chamber 16.
  • shaft 23 is connected to an extension of the hollow shaft 24 which forms a labyrinth seal 25 with housing 26.
  • Hollow shaft 24 is journalled in a roller bearing 27 which rotatably mounts disk 22.
  • shaft 24 is driven by a motor 28 through the reducing gear box 29.
  • a rotary union 30 on top of hollow shaft 24 is connected by means of a line 31 to any convenient source of cool compressed air at 20 to 30 p.s.i. Housing 32 supports gear reducer 29 and motor 28.
  • An exhaust duct 35 is disposed over disk 22 opposite the largest portion of andwithin inlet duct 20.
  • a metal inlet chamber seal 36 extends completely about the periphery of disk 22.
  • a partition 39 divides the inlet duct 20 from the exhaust duct 35.
  • a portion 40 of partition 39 surrounds shaft 23 and opens into inlet duct 20 so that shaft 23 will operate in the cooler inlet gases.
  • Cool air entering line 31 passes through hollow shaft 24 and its lower extension to flow through the apertures 41 in the labyrinth seal 25. This air cools bearing 27 as it leaks from seal 25 and it prevents any upward flow of hot gases through seal 25.
  • An adjusting nut 42 secures disk 22 to shaft 23 and a radiation shield 43 reduces heat flow up shaft 23.
  • An exhaust duct 44 leads to a stack 45.
  • disk 22 is a refractory heat transfer material able to withstand temperatures in excess of 2,000F.
  • Disk 22 contains a number of through passages 46 which provide an open area of over 70 percent.
  • One such disk was 27
  • This invention operates as follows. Satisfactory combustion of pollutants in an afterburner requires the pollutants be raised to a temperature from l,000 to 1,500F. By use of fuel alone, 20 Btu are required to raise the temperature of 1SCF l,OF. The cost to eliminate pollutants from 5,000 SCFM of 500F stack gas by combustion to l,500F for 8,000 hours per year with gas at 30 c per MCF, would be I 7,000 per year.
  • the purpose of this invention is to reduce the requirement for fuel of an afterburner system by recycle of exhaust heat to preheat the incoming gas.
  • regenerators The performance of regenerators is best compared on the basis of effectiveness defined as the temperature rise in or heat transferred by the regenerator compared to the theoretical maximum which could be transferred in an exchanger with infinite area. For example, with a gas inlet of 500F and exit from the afterburner of 1,500F, an exchanger with infinite surface and 100 percent effectiveness could preheat the inlet gas to l,500F for a temperature rise of 1,000F. A regenerator with 75 percent effectiveness would prehead the inlet gases 75 percent of 1,000F or 750F, thus reducing the fuel requirements from 1,000F temperature rise to 250F temperature rise and saving 75 percent of the $17,000 annual fuel bill required without regeneration. The inlet gases would be preheated to l,250F and temperatures of disk 22 would reach an average between L250 and l,500 or about 1,400F with higher temperatures during upsets and transients.
  • Seals 36 and 37 are required to minimize leakage of gas around the wheel 22 to and from the combustion chamber 16 and also across the partition 39 from inlet duct to the exhaust duct 35. Non-rubbing, close clearance seals 36 and 37 allow minimal leakage.
  • the wheel shaft 24 and the structural members connecting the seal 36 and the wheel bearing 27 are all surrounded by the cooler inlet gas, thus these elements are maintained at equal temperature and expand equally.
  • the hotter exhaust gas is contained in the exhaust duct 35 which is surrounded and separated from the main structure by the cooler inlet gas. Pressure in the combustion chamber 16 is less than in the inlet duct 20, thus, leakage across the peripheral seal 36 is of cooler inlet gas leaking into the combustion chamber 16. In this way hot gas is kept away from the seals 36 and 37 which are prevented from overheating.
  • the disk 22, seals 36 and 37, shaft 24, bearing 27, and motor 28 are a precision assembly and are inserted and withdrawn into the complete regenerator as a single unit.
  • Wheel or disk 22 sub-assemblies will be interchangeable between units of different numbers of wheels 22.
  • the shaft 24 is cooled by cool pressurized air from line 31.
  • the cooling air leaks out in the labyrinth shaft seal 25, with a portion of it leaking inwards into the gas inlet duct 20 so that leakage of polluted gas to the outside is prevented.
  • Afterbuming requires oxygen to be present in the gases at time of combustion. Many polluting gases do not contain oxygen and require addition of air for combustion proportional to the fuel required to be burned.
  • the regenerated afterburner of this invention requires the addition of less air than a straight afterburner with a greater fuel saving than for cases where no air addition is required.
  • the afterburner is supplied with a fan 10 to balance its pressure drop. Pressure drop during both passes through the disk 22 is about 22 inches of water which requires a fan 10 of about 50 h.p.
  • Typical operating conditions for a unit as shown in FIG. 1 are as follows. Polluted gas flows to the fan inlet duct 13 at 500F and approximately at atmospheric pressure. The fan 10 raises the pressure of the gas to 27 inches water required to push the gas through the regenerator disk 22. In passing through the wheel 22, the gas is heated from 500 to l,300F, thus cooling the wheel 22. Combustion in chamber 16 then raises the temperature from l,300 to l,500F. Combustion chamber volume will provide approximately 0.5 secs. residence time at maximum temperature. When leaving the chamber 16 through the regenerator wheel 22, the gas cools from l,500 to 700F while heating the wheel 22. I
  • the wheel 22 is rotated at about 15 RPM by speed reducer 29 driven by A HP motor 28.
  • a variable speed motor 28 is supplied.
  • the gas discharges direct to stack 45, but can alternately be passed through a heat exchanger (not shown) to heat water or raise steam for heating and air conditioning.
  • the unit described will treat about 5,500 SCFM (25,000 lb/hr. or 7 lb/sec) of polluted gas.
  • the fan motor 11 absorbs 50 HP, and the motor 28 to turn the regenerator wheel 22 takes about A HP.
  • Fuel consumption is about 1,600 SCF of natural gas per hour introduced through line 50, insulating bushing 51 and burner 52 as shown in FIG. 2.
  • This unit with fan and motor and all accessories mounted on a skid weighs about 15,000 lbs.
  • the skid is about 12 ft.
  • Total height of the unit is about 16 ft.
  • the deposits are all combustible and predominantly carbon and can be burned from the regenerator disk surface by raising the temperature to above the ignition point.
  • the hot side of the wheel 22 will operate above the ignition temperature of deposits and no deposition will occur on the hot side.
  • the cold side will operate at a mean temperature between gas inlet and outlet temperatures which will usually be below the ignition temperature of deposits, thus deposits will form in a zone extending part way through the wheel 22 from the cold side.
  • the temperature of the cold side of the wheel 22 can be raised to burn off the deposits by slowing the wheel to spoil the effectiveness of heat exchange and simultaneously increasing the afterburner firing.
  • Deposits can also be removed by stopping the wheel 22 in a series of positions until all sectors had been cleansed, however, the unequal heating of the wheel 22 may result in detrimental thermal stresses and distortion.
  • the combustion temperature rise in the regenerative afterburner if a fraction of the total temperature increase of the gas equal to l-E percent. Where E is the regenerator effectiveness,'E will usually fall between 70 and 80 percent, thus, total temperature rise will be from three to five times the combustion temperature rise. Temperatures in the afterburner will usually not exceed 2,000F, thus combustion temperature rise will fall between 200 and 500F. This temperature rise requires a heat release by combustion of from 5 to l l Btu per SCF. If the effluent gas to be treated contains this quantity of unburned combustible after the regenerator has achieved operating temperatures, no supplementary fuel will be required. Preheating-and pilot fuel will be required depending on operating conditions.
  • the lower explosive limit of a gas will usually contain combustibles that will result in a temperature rise of about 50 Btu per SCF.
  • combustible contents are held to a maximum of 25 percent of the LEL or a maximum heating value of about 13 Btu per SCF.
  • Maximum temperatures in the regenerative afterburner will be exceeded if combustibles in the gas exceed about Btu per SCF, thus explosions and flashback in the regenerative afterburner are unlikely to be a factor with sound application and operating engineering.
  • the quantity of fuel required by the regenerative afterburner when evenly dispersed throughout the gas stream is not combustible at normal temperatures. At the higher temperatures after passing through the wheel 22, the dispersed fuel often will burn, and it is often desirable to inject the fuel gas through injector 60 shown in phantom lines in FIG. 2, upstream of the wheel 22 where it is not combustible and thus use the wheel 22 as a flame holder. This makes the best use of combustor volume and results in a low cost system. A flame holder and ignitor (not shown) are then required downstream of the wheel for light off and warm up.
  • FIGS. 3 and 4 show a modification of this invention in which a large volume combustion chamber lined with refractory material 101 has a large inlet duct 102 fixed over it and connected to a fan (not shown).
  • Four identical units 103 are fixed about the periphery of chamber 100 in duct 102.
  • Each unit 103 has a drive 104 substantially identical to those described for the first embodiment of this invention.
  • Each drive 104 rotates a regenerator disk 105.
  • Four exhaust ducts 107 extend over a sector of each disk 105 and communicate with the central stack 108. The exhaust ducts 107 thus extend through the inlet 102.
  • This modification of the invention operates in the manner described for the first embodiment except that its capacity is increased four times.
  • the units 103 may be independently replaced for servicing.
  • a regenerative afterburner of gases for air pollution elimination comprising, in combination, a combustion chamber, a regenerator disk of low heat conductivity having passages extending therethrough disposed over said combustion chamber, an inlet duct having a first seal extending about the periphery of said disk, means for slowly rotating said disk, an exhaust duct having a second seal extending about a first sector of said disk within said first seal, said exhaust duct extending to said first sector of said disk, a fan forcing gases from said inlet duct through said disk into said combustion chamber heating said gases, said gases burning in said combustion chamber and flowing through said disk into said exhaust duct heating said disk and means in said inlet duct over said disc having an air supply for purging said disk of inlet gases prior to said disk rotating under said second seal of said exhaust duct.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Incineration Of Waste (AREA)
US00110279A 1968-07-05 1971-01-27 Regenerative afterburner for air pollution elimination Expired - Lifetime US3718440A (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2624874A1 (de) * 1976-03-30 1977-12-29 Kraftanlagen Ag Vorrichtung zur thermischen nachverbrennung von prozessabgasen
US4126419A (en) * 1974-04-02 1978-11-21 Keichi Katabuchi Combustion device for burning waste gases containing combustible and noxious matters
US4280416A (en) * 1980-01-17 1981-07-28 Philip Edgerton Rotary valve for a regenerative thermal reactor
US5232358A (en) * 1988-07-08 1993-08-03 Nippon Chemical Plant Consultant Co., Ltd. Combustion apparatus
US5562442A (en) * 1994-12-27 1996-10-08 Eisenmann Corporation Regenerative thermal oxidizer
US5601790A (en) * 1993-07-16 1997-02-11 Thermatrix, Inc. Method and afterburner apparatus for control of highly variable flows
US5628968A (en) * 1993-12-27 1997-05-13 Eisenmann Maschinenbau Kg Apparatus for purifying pollutant-containing waste air from industrial plants by regenerative afterburning
US5768888A (en) * 1996-11-08 1998-06-23 Matros Technologies, Inc. Emission control system
US5871349A (en) * 1997-10-16 1999-02-16 Smith Engineering Company Rotary valve thermal oxidizer

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3509834A (en) * 1967-09-27 1970-05-05 Inst Gas Technology Incinerator

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3509834A (en) * 1967-09-27 1970-05-05 Inst Gas Technology Incinerator

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4126419A (en) * 1974-04-02 1978-11-21 Keichi Katabuchi Combustion device for burning waste gases containing combustible and noxious matters
DE2624874A1 (de) * 1976-03-30 1977-12-29 Kraftanlagen Ag Vorrichtung zur thermischen nachverbrennung von prozessabgasen
US4280416A (en) * 1980-01-17 1981-07-28 Philip Edgerton Rotary valve for a regenerative thermal reactor
US5232358A (en) * 1988-07-08 1993-08-03 Nippon Chemical Plant Consultant Co., Ltd. Combustion apparatus
US5601790A (en) * 1993-07-16 1997-02-11 Thermatrix, Inc. Method and afterburner apparatus for control of highly variable flows
US5637283A (en) * 1993-07-16 1997-06-10 Thermatrix, Inc. Method and afterburner apparatus for control of highly variable flows
US5628968A (en) * 1993-12-27 1997-05-13 Eisenmann Maschinenbau Kg Apparatus for purifying pollutant-containing waste air from industrial plants by regenerative afterburning
US5562442A (en) * 1994-12-27 1996-10-08 Eisenmann Corporation Regenerative thermal oxidizer
US5768888A (en) * 1996-11-08 1998-06-23 Matros Technologies, Inc. Emission control system
US5871349A (en) * 1997-10-16 1999-02-16 Smith Engineering Company Rotary valve thermal oxidizer

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CA943406A (en) 1974-03-12
GB1231435A (fi) 1971-05-12

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