US3867102A - Fume incinerator - Google Patents

Abstract

In a fume incinerator, a preheater for incoming gas to be treated comprises straight tubes through which hot combustion gas is passed, and means for conducting incoming gas to a combustion unit along a zigzag path repeatedly crossing the exteriors of the tubes. The tubes can be made of inexpensive metal because they operate cooler than heretofore. A J-shaped combustion unit promotes turbulent mixing and causes heat to be focused at a central zone.

Description

I I United States Patent 11 1 1111 3,867,102 Csathy 1451 Feb. 18, 1975 FUME INCINERATOR 3,251,656 5/1966 Edwards 23/277 (3 3,353,919 11/1967 Stockman 23/277 C [75] Inventor: B E G- Csathy, Mmneapohs, 3,561,928 2/1971 Weber 23/277 0 mn. [73] Assignee: llsfilltgk Corporation, Minneapolis, Primary Examiner james H. Tayman,

[22] Filed: May 28, 1974 21 Appl. Ne.;474,093 I [57] ABSTRACT R l d U S A fi ti m In a fume incinerator, a preheater for incoming gas to [63] Continuation of Ser No 236 361 March 20 1972- 1 be treated comprises straight tubes through which hot abandoned combustion gas is passed, and means for conducting incoming gas to a combustion unit along a zigzag path [52] us. c1. 23/277 c, 423/210, 110/8 A repeatedly Crossing the exteriors of the tubes The 51 1m. (:1. F0ln 3/12, F23g 7/06 tubes can he made of inexpensive metal because they 58 Field Of Search 23/2770; 423/210; Operate Cooler than heretofore A P Combus- 1 10/8 tion unit promotes turbulent mixing and causes heat to be focused at a central zone. [56] References Cited UNITED STATES PATENTS 3 Claims, 2-Drawing Figures 3,090,675 5/1963 Ruff at 111...; 23/277 c 2 iji:

li egui 34 s Z9 I 1 1 Q 24 7 W; i, p 3O @6 35 \Q\ 28 5| 27E PATENTEB FEB] 8l975 sum 2 or 2 FIG.'Z.

I t FUME INCINERATOR now abandoned.

This invention relates to improvements in incinerators for combusting fumes and particulate matter that is carried in gas to be treated, and by which such gascarried material is rendered inoffensive.-

It is known to provide fume incinerators with a heat exchanger in which gas to be treated, before being fed into the combustion zone is passed in heat transfer relation with gases issuing from that zone. Preheating of the incoming gas to be treated affords substantial fuel economy and results in more complete combustion of the objectionable matter carried by such gas.

However, prior fume incinerators had the problem of blockage of the heat exchanger passages due to accumulations of particulate matter precipitated from gas to be'treated. The present invention is in part based upon a recognition that this problem was the result of the heat exchanger arrangement heretofore invariably used, wherein the gas to be treated was caused to flow inside of heat exchanger tubes and hot combustion gas was passed across the exteriors of such tubes. The present invention is also based in part upon the recognition that this prior arrangement, despite its uniform acceptance, not only gave rise to the blockage problem but was rather directly responsible for the high cost of prior apparatus. This was because the heat exchanger tubes of prior incinerators operated at such high temperatures that they had to be made of stainless steel, which is of course expensive.

In any fume incinerator havinga heat exchanger, the gases must obviously undergo some change in flow direction in the course of passing through the incinerator apparatus as a whole, in order for incoming gas to pass in heat exhange relation with departing hot gases. In prior incinerators in which such change in flow direction was wholly or partially accommodated by curved or bent heat exchanger tubes, the curves in the tubes further aggravated and contributed to the problem of tube blockage, since particulate matter tended to be precipitated out of the gas to be treated as it flowed through the curved parts ofthe tubes, being thus deposited in precisely those portions of the tube interiors that were least accessible for cleaning.

By contrast, it is the general object of this invention to provide a fume incinerator which is not only lower in first cost than prior such devices but requires substantially less maintenance and attention than prior fume incinerators, although affording more complete combustion of fumes and particulate matter in gas to be treated.

A more specific object ofthis invention is to provide a fume incinerator of the character described that can be made at substantially lower cost for a given capacity than prior such devices by reason of its having a heat exchanger in which incoming gas to be treated abstracts heat from gases issuing from the combustion zone, which heat exchanger is so arranged that its tubes are at a substantially lower operating temperature than those in the apparatus heretofore conventional, and can therefore be made of less expensive material.

A further specific object of this invention is to provide a fume incinerator having a compact combustion chamber which accommodates the necessary change in flow direction through the apparatus as a whole, to make possible the use of straight heat exchanger tubes in the preheater, and which combustion chamber furthermore induces a high degree of turbulence in the gases flowing therethrough and is so arranged as to concentrate the heat of combusting fuel upon such gases, thereby assuring thorough and complete combustion of objectionable matter to be incinerated.

It is also a specific object of this invention to provide a fume incinerator which is so arranged as to induce all precipitation of particulate matter to take place in a part of the apparatus where it is readily accessible for removal.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of an embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a view in vertical section of a fume incinerator embodying the principles of this invention; and

FIG. 2 is a view in front elevation of the fume incinerator shown in FIG. 1.

Referring now more particularly to the accompanying drawings, the numeral 5 designates generally a fume incinerator embodying the principles of this invention, intended for burning fumes and particulate matter carried by gases to be treated. In most cases gas or air to be treated that carries combustible fumes will also contain a certain amount. of particulate matter, and it is the particulate matter which presents special problems that are solved in the apparatus of this invention.

For ease of handling and shipment, the fume incinerator 5 can be manufactured as two units or subassemblies, namely a preheater 6 and a combustion unit 7. Preferably the incineratoris installed with the combustion unit 7 lowermost and the preheater 6 projecting up from it, but it will be seen that the incinerator can also be laid on its side so that gases flow through it horizontally. The incinerator is hereinafter described, for purposes of example, as if erected for vertical operation with the preheater uppermost.

In general, the preheater compriseswalls that define a vertically elongated passage, and more specifically a pair of substantially identical opposite side walls 8, a front wall 9 and a rear wall 10. There is an inlet 11 for gas to be treated in the rear wall, near its top, and an outlet 12 for such gas in the front wall, near its bottom. It will be understood that the gas to be treated is forcefully propelled into theinlet 11, as by means of a fan or blower (not shown).

The top and bottom end walls of the preheater passage are defined by tubesheets I3 and 14, respectively, and a plurality of straight heat exchange tubes 15 ex tend between these tubes sheets and vertically through the preheater passage. At their lower ends these tubes are communicated with the interior of the combustion unit.

' In prior fume incinerator-s having heat exhangers wherein gas to be treated abstracted heat from gases leaving the combustion zone, the gas to be treated, was caused to flow to the combustion zone through stainless steel heat exchanger tubes, and hot gases of combustion were passed across the outside of such tubes.

It will be observed that the incinerator of the present -in this art turns out to have unexpected advantages. For

one,'the gases issuing from the combustion unit are cleaner than the gases to be treated, and therefore with the arrangement of this invention there is little likelihood of the heat exchanger tubes being plugged by particulate matter precipitated out of the gas flowing through them. Furthermore, because of the different dynamics of stream flows along and across a tube, the internal heat transfer coefficient of a heat exchanger tube is considerably lower than its external heat transfer coefflcient; and for this reason the arrangement of the present invention has the additional important advantage that the metal temperature of the heat exchanger tubes remains lower than for an equivalent capacity unit embodying the heretofore customary opposite arrangement. Consequently the heat exchanger tubes 15 can be made of a less expensive steel than the stainless steel heretofore conventionally used for such tubes. I

In order to cause the greatest possible amount of heat to be transferred from the combustion gases to the gas to be treated, the latter is caused to flow through the preheater passage ina zigzag path, generally along the tubes 15 and back and forth across them. To this end the preheater is provided with a pair of baffles, one of these, designated 17, being located a short distance below the inlet 11 and extending from the rear wall 10 partway to the front wall 9, the other baffle 18 being intermediate the baffle l7 and the outlet 12 and projecting from the front wall partway to the rear wall. To further encourage zigzag flow of gas to be treated, the rear wall has portions 19 which are inclined forwardly and toward the baffle l7, and the front wall has similar portions 20 that are inclined rearwardly and toward the baffle 18.

The combustion unit 7 of the incinerator of this invention is substantially .I-shaped. The outlet 12 of the preheater unit opens directly into the inlet of the combustion unit, which is located in its upper portion, intermediate its front and rear ends. From the upper edge of the combustion unit inlet a J-shaped outer wall 22 of the combustion unit extends forwardly, thence downwardly and around in a semicircular arc, as at 24, and merges into a straight bottom wall portion 26 that extends rearwardly beneath the .combustion chamber inlet and the lower tube sheet 14. The rear edge-of the J-shaped outer wall 22 is near the plane ofthe rear wall 10 of the preheater. From that rear edge a vertical wall portion 27 extends up to the rear edge of the lower tube sheet, which extends rearwardly in the plane of the lower edge of the combustion unit inlet. The combustion unit also has a generally channel shaped inner wall portion 28 with a front-vertical leg 29 extending down from the bottom edge of the combustion unit inlet, a

rear vertical leg 30 extending down from the front edge of the lower tube sheet 14, and a horizontal portion 31 connecting said legs and spaced above the bottom wall portion 26. The combustion unit also has flat,'substantially identical side walls 32.

The above described wall portions of the combustion unit can be made of steel plate that forms a shell, lined with a thick layer 33 of castable refractory material, with a layer 34 of high temperature insulation sandwiched between the refractory layer and the shell. The refractory material and the insulation can be secured to the shell in any suitable manner, as by means of high alloy anchors (not shown). The underside of the lower tube sheet is also covered with refractory material. as at 35, and stainless steel ferrules 36 extend through that refractory and a short distance up into the tubes 15.

Directly at the combustion unit inlet there is a fuel burner 37 of the type comprising a'multiplicity of fuel nozzles arranged in convergent substantially coplanar relationship so as to produce a grid or sheet of flame. Hence all portions of the stream of gas to be treated are exposed to combusting gas in the course of passage through that inlet.

The fuel burner is preferably one that is intended for burning a gaseous fuel, such as natural gas. Hence the gas to be treated, in passing through the sheet of flame produced by the burner at the entrance to the combustion unit, will be subjected to a temperature on the order of l500F., at which fumes that it carries will be incinerated.

As the gas to be treated moves into the combustion unit from the inlet thereof, along with hot combustion gases from the fuel burner, the curved outer wall portion 24, in cooperation with the inner wall portion 28, compels such gases to undergo a complete reversal of flow direction. Note that the roundedwall portion 24, which is rearwardly concave, has a uniform radius of curvature about an axis located just in front of and below the inlet to the combustion unit. The semicylindrical shape of this wall portion not only imparts a substantial turbulence to the gases flowing along the J-shaped path that it helps to define, but it also reflects heat and focuses it back toward the axis about which it is curved, producing a core-like zone of very high heat in the area where the gas to be treated is emerging from the inlet to the combustion unit.

In these respects the configuration of the walls of the combustion unit serves to insure very complete combustion of both fumes and particulate matter carried by gas to be treated.

Preferably there is an observation port 38- in the curved wall portion 24, arranged so that both the burner flame and the core'like zone of reflected heat focus can be seen. 7

Upon passing out the hottest part of the combustion zone, the gases flow rearwardly above the straight bottom wall portion 26 and are then subjected to another abrupt change in flow direction. This time they are deflected upwardly by the vertical, wall portion 27 at the rear of the combustion unit. In making this last rightangle turn the gases tend to drop heavy particulates into or near the corner defined by the junction of the bottom wall portion 26 with the vertical wall portion 27, and therefore the vertical wall portion is preferably apertured at its bottom for a refractory-lined manhole or clean-out door 39.

The final upward movement of the gases in the combustion unit carries them into the heat exchanger tubes and thus out of the combustion unit proper. In flowing upwardly through the tubes, the hot gases of course give up their heat to incoming gas to be treated, as explained above. At'their upper ends the tubes can open into a stack through which they can be vented. Y

From the foregoing description taken with the ac companying drawings it will be apparent that this in vention provides an incinerator for fumes and particulate matter carried by a stream of gas to be treated, comprising a heat exchanger by which combustion gases are passed in heat exchange relation with incoming gas to be treated, which heat exchanger, in departing from principles heretofore uniformly accepted and practiced, can be made at substantiallylower cost but nevertheless obviates the plugging problem that had beset heat exchangers in prior fume incinerators. It will also be apparent that the fume incinerator of this invention comprises a combustion unit that promotes complete and very efficient combustion and effects the deposit of heavy particulate matter in a zone where it is readily accessiblefor removal.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims.

I claim:

1. An incinerator by which fumes and particulate matter carried in gas to be treated can be rendered inoffensive, and which comprises a combustion chamber in which gas to be treated is subjected to a high temperature, and a preheater in which gas to be treated, flowing towards the combustion chamber, is passed in indirect heat exchange relation with hot gas issuing from the combustion chamber, said incinerator being characterized by:

A. the preheater comprising 1. means defining an elongated passage having opposite end walls and having near one of its end walls a laterally opening inlet for gas to be treated and having near its other end wall a laterally opening outlet for preheated gas to be treated, and g 2. a plurality of substantially straight tubes extending lengthwise in said passage and through said end walls, through which tubes heated gas from the combustion chamber can flow for heat exchange with gas flowing from said inlet to said outlet across the exterior of the tubes; means defining an axially short burner zo'ne through which said outlet is substantially directly communicated with the combustion chamber; C. a plurality of spaced apart nozzles for combustion spaced substantially parallel relation to said other end wall of preheater, and 2. the rounded portion of said J-shaped wall being inwardly concave, curved on a substantially uniform radius through about and joined to an edge of the burner zone that is remote from said straight long leg so that a substantial part of said rounded wall portion is in opposing, spaced relation to the burner zone'to compel gas flowing out of the burner zone to undergo a reversal of direction in flowing through the combustion chamber and to reflect heat from the burner zone into substantial portions of the interior of the combustion chamber, thus subjecting substantially all por tions of gas flowing through said chamber to re flected heat.

2. The incinerator of claim 1 wherein the combustion chamber further comprises:

another substantially straight wall portion extending between said long leg of the J-shaped wall portion and said other end wall of the preheater, said other substantially straight wall portion and said long leg of the J-shaped wall defining mutually substantially perpendicular inner wall surfaces of the combustion chamber that are remote fromsaid rounded wall portion and cooperate with one another to produce turbulence in gas flowing along them towards the tubes, one of said inner wall surfaces being oriented substantially horizontally so that particulate matter carried by the gas can settle onto it for collection.

3. The incinerator-of claim 1, further characterized by:

1. said outlet of the preheater being of substantially smaller area in cross section than the portion of the passage inwardly adjacent to it, and 2. the burner zone being of substantially the same size and shape in cross section as said outlet, to ensure that combusting gas issuing from, the nozzles extends substantially entirely across it.

Claims (10)

1. THE STRAIGHT LONG LEG OF SAID J-SHAPED WALL BEING SPACED FROM SAID BURNER ZONE AND BEING IN SPACED SUBSTANTIALLY PARALLEL RELATION TO SAID OTHER END WALL OF PREHEATER, AND

1. AN INCINERATOR BY WHICH FUMES AND PARTICULATE MATTER CARRIED IN GAS TO BE TREATED CAN BE RENDERED INOFFENSIVE, AND WHICH COMPRISES A COMBUSTION CHAMBER IN WHICH GAS TO BE TREATED IS SUBJECTED TO A HIGH TEMPERATURE, AND A PREHEATER IN WHICH GAS TO BE TREATED, FLOWING TOWARDS THE COMBUSTION CHAMBER, IS PASSED IN INDIRECT HEAT EXCHANGE RELATION WITH HOT GAS ISSUING FROM THE COMBUSTION CHAMBER, SAID INCINERATOR BEING CHARACTERIZED BY: A. THE PREHEATER COMPRISING

1. MEANS DEFINING AN ELONGATED PASSAGE HAVING OPPOSITE END WALLS AND HAVING NEAR ONE OF ITS END WALLS A LATERALLY OPENING INLET FOR GAS TO BE TREATED AND HAVING NEAR ITS OTHER END WALL A LATERALLY OPENING OUTLET FOR PREHEATED GAS TO BE TREATED, AND

2. A PLURALITY OF SUBSTANTIALLY STRAIGHT TUBES EXTENDING LENGTHWISE IN SAID PASSAGE AND THROUGH SAID END WALLS, THROUGH WHICH TUBES HEATED GAS FROM THE COMBUSTION CHAMBER CAN FLOW FOR HEAT EXCHANGE WITH GAS FLOWING FROM SAID INLET TO SAID OUTLET ACROSS THE EXTERIOR OF THE TUBES; B. MEANS DEFINING AN AXIALLY SHORT BURNER ZONE THROUGH WHICH SAID OUTLET IS SUBSTANTIALLY DIRECTLY COMMUNICATED WITH THE COMBUSTION CHAMBER; C. A PLURALITY OF SPACED APART NOZZLES FOR COMBUSTION GAS MOUNTED IN SAID BURNER ZONE, SAID NOZZLES HAVING THE AXES OF THEIR OUTLETS LYING SUBSTANTIALLY IN A COMMON PLANE AND THEIR OUTLETS SO ORIENTED THAT COMBUSTING GAS ISSUES FROM THEM IN A SHEET OF FLAME ACROSS SUBSTANTIALLY THE ENTIRE AREA OF SAID ZONE WHEREBY ALL PORTIONS OF GAS FLOWING FROM THE PREHEATER INTO THE COMBUSTION CHAMBER ARE EXPOSED TO COMBUSTING GAS TO BE INTENSELY HEATED THEREBY; AND D. THE COMBUSTION CHAMBER HAVING A SUBSTANTIALLY J-SHAPED WALL,

2. The incinerator of claim 1 wherein the combustion chamber further comprises: another substantially straight wall portion extending between said long leg of the J-shaped wall portion and said other end wall of the preheater, said other substantially straight wall portion and said long leg of the J-shaped wall defining mutually substantially perpendicular inner wall surfaces of the combustion chamber that are remote from said rounded wall portion and cooperate with one another to produce turbulence in gas flowing along them towards the tubes, one of said inner wall surfaces being oriented substantially horizontally so that particulate matter carried by the gas can settle onto it for collection.

2. the rounded portion of said J-shaped wall being inwardly concave, curved on a substantially uniform radius through about 180*, and joined to an edge of the burner zone that is remote from said straight long leg so that a substantial part of said rounded wall portion is in opposing, spaced relation to the burner zone to compel gas flowing out of the burner zone to undergo a reversal of direction in flowing through the combustion chamber and to reflect heat from the burner zone into substantial portions of the interior of the combustion chamber, thus subjecting substantially all portions of gas flowing through said chamber to reflected heat.

2. THE ROUNDED PORTION OF SAID J-SHAPED WALL BEING INWARDLY CONCAVE, CURVED ON A SUBSTANTIALLY UNIFORM RADIUS THROUGH ABOUT 180*, AND JOINED TO AN EDGE OF THE BURNER ZONE THAT IS REMOTE FROM SAID STRAIGHT LONG LEG SO THAT A SUBSTANTIAL PART OF SAID ROUNDED WALL PORTION IS IN OPPOSING, SPACED RELATION TO THE BURNER ZONE TO COMPEL GAS FLOWING OUT OF THE BURNER ZONE TO UNDERGO A REVERSAL OF DIRECTION IN FLOWING THROUGH THE COMBUSTION CHAMBER AND TO REFLECT HEAT FROM THE BURNER ZONE INTO SUBSTANTIAL PORTIONS OF THE INTERIOR OF THE COMBUSTION CHAMBER, THUS SUBJECTING SUBSTANTIALLY ALL PORTIONS OF GAS FLOWING THROUGH SAID CHAMBER TO REFLECTED HEAT.

2. a plurality of substantially straight tubes extending lengthwise in said passage and through said end walls, through which tubes heated gas from the combustion chamber can flow for heat exchange with gas flowing from said inlet to said outlet across the exterior of the tubes; B. means defining an axially short burner zone through which said outlet is substantially directly communicated with the combustion chamber; C. a plurality of spaced apart nozzles for combustion gas mounted in said burner zone, said nozzles having the axes of their outlets lying substantially in a common plane and their outlets so oriented that combusting gas issues from them in a sheet of flame across substantially the entire area of said zone whereby all portions of gas flowing from the preheater into the combustion chamber are exposed to combusting gas to be intensely heated thereby; and D. the combustion chamber having a substantially J-shaped wall,

2. the burner zone being of substantially the same size and shape in cross section as said outlet, to ensure that combusting gas issuing from the nozzles extends substantially entirely across it.

3. The incinerator of claim 1, further characterized by:

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