US3497308A - Air purifying apparatus and method - Google Patents

Description

Feb. 24, 1970 f 4:.l s. FLYNN AIR PURIFYING. APPARATUS Aub METHOD Filed July 22, 1968 .u mm wmf mr in.. VJ M ms e s l w f up A. M Y. V.. B

United States Patent O 3,497,308 AIR PURIFYING APPARATUS AND METHOD Charles S. Flynn, 2991 Sherwood Court, Muskegon, Mich. 49441 Filed July 22, 1968, Ser. No. 746,462 Int. Cl. F23d 13/44 U.S. Cl. 431-5 6 Claims ABSTRACT OF THE DISCLOSURE Combustion apparatus and method for Combusting Waste fluids, particularly combustible vaporous and gaseous fluids as from kraft paper pulp processing, in a thorough and safe manner, with such fluids being passed at high velocity through manifold jets specially located adjacent special gaseous burners, into a hot gas flow zone in a stack for ignition and passage to the atmosphere in puried form. The processing kettle is preferably vented to the atmosphere through a kettle stack from which the fluids are drawn by suction to be forcefully blown through the manifold equipment and out a second stack.

BACKGROUND OF THE INVENTION This invention relates to an apparatus and a method of combusting Waste fluids and destroying noxious components of discharged fluids, with the invention having particular significance in combination with kraft pulp processing apparatus.

Certain industrial processes to frequently result in the discharge of obnoxious, harmful components into the atmosphere. Particularly obnoxious substances are ejected into the atmosphere when processing wood to wood pulp for paper by the kraft process. The pungent, obnoxious odor of the mercaptans and suldes can often be detected for miles from the facility. Although electrical precipitator equipment can -be used with some success for this problem, its limitations have prevented kraft pulp processors from widely adopting it. Although such waste products are combustible, the exhaust vaporous and gaseous fluids from kraft pulp processing kettles varies from a low volume of gases which will not maintain combustion when hard Woods are processed `to tremendous volumes of potentially explosive mixtures of gases and vapors when conifers are processed, because of the presence of large amounts of turpentine vapors as well as other highly combustible substances. An explosion back into the mammoth kettle would be disastrous. Other industrial processes also cause obnoxious and/or toxic discharge into the atmosphere.

SUMMARY OF THE INVENTION It therefore is an object of this invention to pro-vide a unique apparatus for combustion of such combustible waste fluids in an efficient manner, but with a low initial cost and a low operational cost. The apparatus is particularly suitable for treatment of combustible stack gases and vapors as from kraft paper processing and the like.

Another particular object of this invention is to provide an apparatus and a method of reliably and relatively inexpensively eliminating the obnoxious components of kraft paper pulp processing stack gases and vapors. Moreover, the unique equipment is capable of reliably treating the wide range of such stack gases, including effecting continuous combustion of the relatively low volume of gases from hard woods, and also safely treating the high volume of potentially explosive gases and vapors from conifers without danger of explosion due to flash-back to the kettle. Moreover the system is relatively inexpensive.

The novel apparatus employs a particular burner and manifold arrangement, in a stack, the burner having hot combustion gas flow past the manifolds jets through which the combustible gases and vapors are ejected at a high velocity. The burner combustion gases extend over a substantial area using a refractory felt dissipator and combustion surface. This surface has the manifold adjacent thereto, preferably at its peripheral portions and slightly offset toward the downstream direction, i.e. normally the stack discharge end. The burner surface is oriented toward the discharge end, with the manifold outlet jets being directed toward this discharge.

The gases are sucked out of the generating vessel zone and forcefully discharge through the manifold ports or jets adjacent the burners at a velocity far exceeding the llame propagation rate of any of the combustible, c g. about 18,000 feet per minute, preventing flash-back into the kettle or other vessel.

The details of the method and the construction and arrangement, as well as other objects and advantages will be apparent from a study of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevational, fragmentary, partially sectioned view of the novel apparatus shown in combination with a paper processing apparatus;

FIG. 2 is a plan view of a portion of the apparatus in FIG. l, taken on plane II-II; and

FIG. 3 is an enlarged sectional view of one of the burner units in the combination.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to the drawings, the complete assembly 10 there shown includes a kraft paper pulp processing kettle 12, the kettle stack 14, conduit assembly 16 from stack 14 to a second stack 18, and specifically to manifold sub-assembly 20 which cooperates with burner assembly '22.

Kettle sub-assembly 12 is of typical configuration and components normally used for the kraft, i.e. sulfate process for treating wood pulp, specifically preparing wood pulp for use in making paper.

Stack 14 which vents kettle 12, is open on its upper end to the atmosphere. The substances ejected from the kettle include mercaptans, some sulfur 1based acids, and, when Conifer wood is being processed, substantial amounts of volatile vaporous materials in the turpentine family. The latter components are of course highly combustile and potentially explosive. The acid components are harmful `to surfaces which they contact. The mercaptans are extremely obnoxious in odor, even when present in very small amounts. Typical of these sulfur based odorous materials are methyl mercaptan, dimethyl sulfide, isopropyl mercaptan, dimethyl disulfide, and dipropyl sulde.

The inlet end of conduit means 16 communicates with the stack 14. This conduit means preferably includes a condensor 24 to condense Water vapor from the stack gases. This is not essential, but does aid in obtaining more complete combustion of the other components. The conduit also includes a blower 26 to withdraw the stack gases from kettle stack 14 into the conduit assembly and force them through the conduit and manifold 20 into the second stack 18 at very high velocity. The pressure in conduit 16 may be indicated on a suitable gauge 30. Stack 18 has its upper end vented to the atmosphere, and has its lower end enclosed by burner assembly 22.

The vertical arrangement of these components as just described is preferred. However, if the manifold ports are kept in proper association between the burners and the stack discharge and adjacent the burner surface so as to discharge into the burner gases and to suck the hot burner gases into the stream for thorough mixing, they need not necessarily be arranged vertically.

This burner assembly includes an overall insulated housing 32 secured to peripheral support 50. This housing receives, through conduit 34, a combustible mixture of gases from a mixer 36. This in turn receives a combustible fuel gas as through inlet 38, and compressed air through conduit 40. Air conduit 40 may include a suitable air regulator 42 and filter 44. The pressure in housing 32 is indicated on a suitable gauge 46. The upper side of housing 32 is enclosed by a baffle plate 48 mounted to a peripheral angle iron support 50. Supported on bafiie plate 48 and secured thereto to receive the combustible mixture of gases therethrough are a plurality of individual burner units 54. Surrounding the burner units, and secured by angle iron support 50 is a peripheral refractory liner 56 which preferably has an upwardly divergent inner surface to cause the hot combustion gases from burner 54 to diverge into the entire area within and over the surface of peripheral manifold 20. Support 50 may be secured to a plurality of legs S8.

An igniter unit 90 has its outlet tip 92 immediately adjacent the surface of one of burner units 54.

Manifold means 20 basically includes a hollow pipe or tube 96 which communicates with the output from conduit means 16 to receive the stack gases. It has a plurality of outlet jets or ports 98 along its length for discharge of the stack gases in stream form at a high velocity. This manifold preferably extends around the perihperal portions of the burner surface area formed by the combined surfaces of the individual burner units, and, with the manifold pipe being positioned close to but offset from the burner surface area in the direction of the stack outlet, normally above the burner surface area. The jets 98 are then oriented upwardly toward the stack outlet, but also inwardly into the zone of discharge of the hot combustion gases from the burners. Immediately above manifold 96 is one or more secondary air shutters 100 to allow supplemental air or oxygen inlet if necessary,

The particular construction of each burner unit is significant. Each burner preferably includes a generally square or rectangular burner housing formed of an outer Shell member 60 and an inner generally annular, peripheral member 62. These members are interconnected by suitable bolts 64, with an annular gasket 66 therebetween. When assembled, the housing includes one open side (FIG. 4) covered by a coarse mesh support screen 68, a fibrous gas dissipating refractory felt layer 70 on screen 68, a relatively fine mesh retention screen 72 over the felt layer, and a generally coarse mesh outer retention screen 74 over the others. When assembled, these elements close the internal chamber 76 which receives a combustible mixture of gases through inlet 78 provided on the back closure face of housing member 60.

Inner housing member 62 fits within outer housing member 60, except for its outermost peripheral edge 62 which is spaced axially slightly from the adjacent outer edge 60 of member 60, to form a peripheral outer groove 80 around the housing.

Support screen 68 is relatively rigid, and rests within the confines of flange 62. It may initially be adhered with an adhesive so as to hold its position during assembly. Felt layer 70 extends over screen 68 and around the periphery of flange or edge 62. It has its outermost edge deformed into groove 80. It is held in this grooveby the outer, relatively coarse mesh screen 74 which also has its peripheral edge extending around edge 62 and deformed or crimped into groove 80' to press the felt layer tightly against edge 62 and secure it and the other screens to the housing. Underlying outer screen 74 and overlying felt layer 70 is the relatively fine mesh screen 72. It preferably is not extended around the housing since this is not necessary. -Rather it is a flat screen member as shown in FIG. 5.

The fibrous felt is a self-supporting layer formed from short refractory fibers, preferably alumina and silica for example in a 50-50 ratio. The fibers are integrated into a unitary sheet body. The randomly dispersed fibers in the integrated structure are initially compressed to the desired thickness and density as by rolling. The felt has myriads of tiny passages, all with sufficient resistance to gaseous fiow to cause uniform gaseous dissipation therethrough. The density of the felt may vary, depending upon the thickness used, the fiber diameter, the ratio of substances and the like. It may range for example from about 2 pounds per cubic foot to about l2 pounds per cubic foot for different applications and may be any where from 1/16 to 1/2 inch in thickness more or less, depending on the factors involved such as desired operating pressure, operating temperature, velocity of gases, and upon the width of the burner, the density of the material; the area of burner to be covered, and the desired flexibility of the felt body. Preferably it is normally quite thin, e.g. around 20 to 40 mils, to fiex and seal readily around the housing edge. The felt must be free from many gaseous leaks of pin hole size which would enable the gases to fiow through in a stream with only slight resistance. These can be identified by the occurrence of flame pimples which visibly project from the surface of the felt during operation. The presence of these undesirable leaks can be readily ascertained by the presence of these fiame pimples. The felt material has a substantial resistance to gaseous flow therethrough due to the fact that the gas must flow through millions of minute tortuous passages having a diameter in the low micron range. Therefore, the pressurized gaseous mixture is generally uniformly distributed over the entire back of the fibrous layer from inner pressure chamber 76.

This distribution of gases is supplemented by a planar bafiie plate 82 in chamber 7.6. The bafiie plate has a plurality of inwardly projecting, L-shaped, spacer flanges 84 on its periphery to abut the inner surface of housing member `62. It also has a plurality of outward spacer projections 86 to abut the inner screen member 68. The gases fiowing in through central inlet 78 strike this baffie and are forced to travel out around the peripheral edge to be distributed relatively uniformly to the entire felt surface area.

The gases, when passing through the felt layer, do so in a finely dispersed uniformly distributed manner in the form of millions of tiny merging streamlets forming a continuous layer of gases over the combustion surface. They are ignited upon emergence from the felt layer. The blue combustion flame occurring :on the surface of the felt layer is visible by peering across the surface. Although the slight blue flame layer often projects a fraction of an inch from the surface, for higher firing rates (from 5,000 to 15,000 B.t.u.s/sq. in.), the flame may be from 1/2 to l" long.

The supporting screen 168 is relatively coarse, self-supporting, and quite rigid. A ten mesh screen (0.025 inch mesh diameter) of steel works excellently, although the exact mesh may vary, providing the screen is kept relatively rigid,

The relatively fine mesh screen 72 has a mesh of about 40, for example (0.010 inch mesh diameter). Any individual fibers of the felt tending to protrude out of the burner surface under pressure are retained in position by this fine screen. It is desirable to keep the fine fibers from extending out from the surface in order to obtain uniform flow and to prevent them from lglowing to cause a spreading radiant heat glow over the surface.

The relatively stiff retention screen 74 serves the double purpose of retaining the felt and screens in position when crimped around the peripheral groove, and also retaining the fine screen, which may tend to bow when heated, in its planar condition.

PEMTION In operation, a combustible mixture of gases is formed in external mixer 36 and conducted through conduit 34 into the chamber of housing 32. The combustible mixture of gases is introduced under pressure through ports 78 into chambers 76 which remain cool. The combustible mixture of gases is then forced by the pressure through the fibrous felt layer, igniting at the outer surface of the felt layer to create high temperature combustion gases. The particular volume and temperature of output can be regulated by varying the pressure and the gaseous mixture input to the burner. With this construction, the gaseous pressure applied can be varied over an extremely wide range, for example from a couple inches of water pressure up to about 30 inches of water pressure.

Simultaneously, the kettle gases and vapors are drawn by suction of the inlet of blower 26 out of stack 14 and kettle 12 into conduit 16 and through condensor 24 and blower 26, and forcefully propelled through manifold 2C'. The stack gases exit from the manifold ports at extremely high vel-ocity, in the general direction of the discharge of the system. This high velocity purposely far exceeds the flame propagation rate of the most cornbustibe kettle mixture, preventing possibility of flashback into the kettle. The ejected gases also create a vacuum or suction to draw the hot gases from the burner surface into the gaseous stream to cause thorough mixing of the oxygen, hot gases, and kettle gases. Mixer 36 can be regulated to have an excess of oxygen necessary for the burners, passing through the burner units, so that sufficient oxygen can be supplied for complete combustion of the stack gases. The tremendous variable output of the burner units enables them to be adjusted to a high output when treating stack gases from the kraft processing of hard wood pulps to elevate the temperature above the kindling temperature, Alternatively, the output of the burners can be adjusted to a relatively small amount, almost nil, by lowering their output to accommodate the relatively low kindling temperatures of stack gases and vaporous fluids emitted during the kraft processing of conifer woods. Typical operating temperatures 0f this equipment are between about 1,000 to 1,600 degrees Fahrenheit, with good results being obtained at about 1,340 degrees Fahrenheit.

It will be noted that stack 14 is still vented to the atmosphere when employing the novel assembly. Thus, if any excess of gases should momentarily erupt from the kettle 12, these can be safely vented without creating a back pressure.

Experimental operations of this equipment in a large kraft processing facility show complete reliability and safety, even in the judgment of insurance inspectors. Further, the reduction of obnoxious components and dangerous components is remarkable. Specifically, the turpentine fractions obtained during processing of conifer wood are eliminated. Moreover, obnoxious components have been shown by careful analysis to have been practically eliminated. Specifically, methyl mercaptaon was reduced from 5340 to 160 parts per million, dimethyl sulfide was reduced from 9030 to 398 parts per million, isopropyl mercaptan was reduced from 8840 to 162 parts per million, dimethyl disulfide was reduced from 1790 to 648 parts per million, and dipropyl sulfide was reduced from 5050 parts per million to an undetectable amount.

Further, estimates of equipment costs indicate that the novel equipment can be installed for approximately one tenth of equipment previously available and which did not have the flexibility or operational characteristics of the novel apparatus, while the maintenance costs have been reduced to approximately one tenth also.

Various additional advantages also may well occur to those in the lart upon studying the foregoing description. As noted previously, the novel apparatus has utility for combusting noxious uids from other processes. Particularly appropriate are those processes causing emission of organic waste products or by products.

Further, the particular configuration and arrangement of the components may be altered somewhat to suit the installation.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for combusting combustibe waste gases and vapors comprising: stack conduit means having a discharge; burner means in said stack means having combustible gas mixture inlet means thereinto, and having hot gas discharge surface area oriented toward said discharge to create a hot gas flow zone toward said discharge; manifold means in said stack means adjacent peripheral portions of said burner discharge surface area:1 having an inlet for a mixture of gases and vapors to be be combusted, and having a plurality of discharge ports adjacent said burner surface area and oriented toward said stack means discharge and blower means for propelling said gases and vapors out of said ports at a velocity exceeding the flame propagation rate thereof, so that waste gases and vapors therefrom engulf hot combustion gases from said burner means for continuous ignition and combustion before passage out said stack means.

2. Apparatus for combusting kraft pulp processing vapors and gases comprising: stack conduit means having a discharge; high velocity burner means in said stack means; said burner means comprising at least one burner having a housing that has combustible gas mixture inlet means thereinto and that has a surface enclosed by a refractory fibrous felt tightly retained thereover by screen retention means extending thereover and secured peripherally to said housing; said felt forming a combustion surface area for uniform combustion of a combustible mixture of gases; said burner surface area being oriented toward said discharge; manifold means in said stack means adjacent peripheral portions of said burner discharge surface area and offset toward said stack discharge, having an inlet for waste gases and vapors to be combusted, and having a plurality of discharge jets oriented generally toward said discharge and adjacent said burner surface area; and a conduit having a discharge end connected to said manifold inlet and having a blower connected on its inlet end, said blower being adapted to be connected to a discharge stack from a kraft pulp processing kettle for withdrawing gases and vapors from said kettle and forcing them at high velocity out said jets, whereby hot combustion gases from said burner means continuously ignite said gases and vapors before passage out said stack means.

3. The apparatus in claim 2 wherein said manifold is closed on its lower end by said burner means, and said manifold means is positioned above and extending around the periphery of said burner surface area.

4. A combination kraft pulp processing and air purifying apparatus comprising:

a wood pulp processing kettle having a stack vented to the atmosphere;

a branch conduit having one end opening into said kettle stack;

blower means in` said conduit arranged to withdraw combustible discharge vaporous and gaseous fluids from said kettle stack and through said conduit;

a manifold on the discharge end of said conduit;

a second stack having an upper end vented to the atmosphere;

said manifold being located in said second stack;

burner means in and closing the lower end of said second stack, having a combustible gas mixture inlet means thereinto, and having a combustion gas discharge surface area oriented generally toward said second stack upper end to create a hot gas ow zone toward said upper end;

said manfoldmeans having outlet jet means adjacent peripheral portions of Said burner surface area and (a) drawing gases and vapors from a kraft pulp processing kettle and the forcing such uids into a manifold;

(b) discharging such withdrawn gases and vapors in tiny streams from said manifold at a velocity far exceeding the iame propagation rate of such gases and vapors While passing hot combusting gases adjacent the manifold to ignite such gases and vapors; and

kraft pulp processing dis- V(c) discharging the entirety of-gases andv vapors to the atmosphere.

6. The method in venting the kettle to for kettle gases.

claim 5 including, in step a, also the atmosphere as a safety outlet References Cited UNITED STATES PATENTS 3,134,424 5/1964 Zink et a1. 431-5 X 3,195,608 7/1965 Voorheis et a1. 431-202 X 3,376,098 4/1968 Pryor 431-238 3,390,944 7/1968 Flynn 431-158 EDWARD G. FAVORS, Primary Examiner Us. C1. XR.

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