US2417670A

US2417670A - Porous disc type gas mixer

Info

Publication number: US2417670A
Application number: US517396A
Authority: US
Inventors: Clifford C Anthes
Original assignee: Union Carbide and Carbon Corp
Current assignee: Union Carbide Corp
Priority date: 1944-01-07
Filing date: 1944-01-07
Publication date: 1947-03-18
Anticipated expiration: 1964-03-18

Description

C. C. ANTHES POROUS DISC TYPE GAS MIXER March 18, 1947.

-Filed Jan. '7, 1944 2 Sheets-Sheet l INVENTOR CLIFFORD C. ANTHES ATTO R N EY March E8, 1947?. Q c, AN H s POROUS DISC TYPE GAS MIXER Filed Jan. 7, 1944 2 Sheets-Sheet 2 H ww INVE NTOI Q CL I FFDRD C. ANTHES ATTORN EY Patented Mar. 18, 1947 ronous DISC TYPE GKSMIXER *Cliflor'd (l. Anthes, Union, :ass'ignonto'Union Carbide and Carbon Corporation, a corporation :of :New York Application January '2, impseriam .517,396

3 .Claims. (Cl. 15.8--r27-.4)

"This'inven'tion relates to blowpip'es and more particularly to a combinedgas mixer andback-fire arrester and flashback preventer assembly.

In, premixed preheating 'gasblowpipe arrangements used in machines for thermochemically removing surface defects from ferrous metal bodies-such,; as slabs and billets, the premixed preheating gas outlet passages frequentlybecome clogged or closed by slagformed during the desurfacing operation, causinglfiash back or backfire which extends to the conventional mixer and the individual gas supply pipes, filling them, with carbon and in many instances even melting or distorting .them, Consequently, the machine has to be shutdown, repaired, and cleaned. Because .offiash back and'backfire extending far back into the system, many individual .parts have to be .cleanedfiand maintenance costs arehigh.

,The principal objects of the present invention are to provide a combinedgas mixer and backfiresarrester assembly adapted .toeprevent .fiashbacks, the downtime .for cleaning and repair being greatly reduced.

According toethe-present, invention a combined gas mixer and backfire arresterrassembl-yris provided comprising a self-supporting porous wflash .arresting element located in a 'blowpipe close to the nozzle; this same element being adapted to .effect, mixing of a -,combustible gas and a combustion-supporting gas. Such gases are separately delivered directly to one face of the element. Such element has many pores which are not straight through :but crossand interconnect withone another, so that one gasentering one pore on the upstream face mixes with the other gas entering-another pore, before suchgases leave theedownstream face. Burning of-the combustible mixture wit-h-inga blowpipe may' be oftwo kinds: (1f) the rapid poppingbackjknown as backfire or (2.) the :sustainedburningknown as flashback and following backfire. The mixed gas is caused to flow-through :a passage having a throat orre- "stricted portion to establish a gas velocity sufilcientlyhightto.prevent any flashback flame continuing after backfire reaches the porous-element. Any backfire flame reaching thedownstream face is blown out almost ins'tantaneouslyby the pores dividing the fiame and each divided fiameportion impinges the pore walls and is quenched in being bent through thetortuous pore passages. A sustained flashback flame'is prevented to avoid unnecessary heating or carbonizing the porous element. Fromthethroat the mixed gas is expanded and delivered "directly'to the nozzle. The size-ofthe porous element is suchthat the pressure drop-of the gasesis not serious. 'The invention is especially suitable in large capacity blowpipesand may "bexused to suppl mixed as to -a-plurality of'nozzles. Any backfire flame is spread 'over the entire downstream porous material.

For other objects and forabetter understanding of the invention, reference may be had to l the following detailed description taken :in connection with the accompanying drawings, in which zFignlfis a side elevational view of a desurfacingmachine embodying the present invention.

Fig. -2 is :a' front View of "the machine shown .in Fig; 1.

Fig- 3' is-an enlarged cross sectional view of a combined-mixer and arrester assembly, taken on .line 3-3 of-Fig. 1,

Fig. 4 is a crosssectional view 'of .a "modified form-of assembly wherein the porous element-is a hollowcone closed watthe downstream en'd.

Fig; *5 is -a transverse cross sectional "view ltaken online 5-5of Fig. 4, and

Fig o is a fragmentary view in cross section of another modification :of the invention.

Referring to Figs. 1, 2 and 3, there is-shown a plurality of blowpipe :units 4-0, 'H, |'2,"3;1'ld I3 located side-by-side and having respective noz- 'zles M, -I-.5, t6 and 4-1. Such units, so arranged, .directpreheatingflames -F toward a ferrousmetal body 8, a.11d, upon the body being moved along underneath the nozzle tips, streams of cutting oxygen, remove ,thermochemicallya layer of sur- .face metal .of predetermined thickness from the body 1 8. A wave 19 of slag containing molten .metal is thrown up .ahead of the nozzle tips. When .preheat .holes .28 in the nozzle tips be .come clogged,-a backfire or flash back occurs. .'-I?he resulting .fiame may momentarily extend rearwardly-through the nozzle, nozzle block zl, andwthrough a mixed gas supply pipe 22 .until extinguished by a combined mixer .andbackfire arrester. assembly 23.

:Accordingto the present invention, the combined mixer and .arrester assembly 23 includes. a self-supporting porous element 39, which not only serves finally and thoroughly to .mix thegases but also .serves. to arrest and extinguish abackfire. Equal volumesof fuel gas and oxidizing gas such .asacetylene and oxygen under .equal pressure, respectively, enter. the assembly :23 through separate pipelines 24 and-.25 and leave welllmixed through the. mixed gas supply pipe 22.

Cutting gas such .as oxygen is supplied by a pipeline. 26.170. a passage 21 in the block 21 and leaves the nozzle tip. through a flat discharge orifice 28. Screw couplings Stand 32 are respectively used onithe. mixedgas supply pipe 22 and the cutting gas supply pipe 26 so that they may be readilydetached from the nozzle block 2|. iper? is detachably connected to the assembly atlits other end by a screw coupling .33. Nozzle it'jisd'etachably retained in the nozzle block 2| by ai'threaded sleeve "34. By "having these parts face "of the detachable, they may be quickly and easily disassembled, cleaned and reassembled.

As shown in Fig. 3, the combined mixer and backfire arrester assembly 23 includes a casing 35 having two inlet sockets 36 and 3'! (Fig. l) and a single outlet socket 38. Each of such sockets is internally threaded to receive an externally threaded hollow coupling sleeve to connect a pipe to the casing. The socket 38 extends axially for a considerable distance into the body 35 and is of suificient diameter to receive a porous element 39, the upper end portion of an elongated metal pipe 46 having a mixed gas delivery passage P provided with a throat or restricted portion 4|, and a threaded coupling sleeve 42 designed to retain the porous element 39 and the pipe 40 within the body 35 upon being screwed into the threaded outlet socket 38.

Spaced vertical passages 43 lead from the threaded inlet socket 36 to an annular gas distributing chamber 44 in the bottom of the socket 38. Horizontally extending passages 45 lead from the inlet socket 31 (Fig. 1) to a central vertical passage 46 formed between the spaced passages 43 and discharging downwardly into the bottom of socket 38. The porous element 39 has an upstream face 41 facing the bottom of both the annular chamber 44 and the central passage 46; the fa e 41 being recessed to provide space so that gases are mixed and distributed well over the face before entering the porous element 39. Acetylene and oxvgen are delivered respectively to

inlet sockets

31 and 36 and mix together at the bottom of the outlet socket 38. Since the pressures of the gases are equal, any flow from one inlet opening to the other inlet opening is prevented.

The porous element 39 has a radially extending flange 48 which fits on a shoulder 49 of an annular recess 50 in the upper end of the elongated pipe 40. Recess 50 is adapted to contain the porous element 39. As the coupling sleeve 42 is tightened within the socket 38 the flange 48 of the porous element is brought tightly against the bottom of the socket 38. The outer annular surface of the porous element 39 is provided with a coating C of gas sealing material or paint so that the pores of the element are completely sealed to prevent any leakage of gas in a lateral direction. Such coating C extends also over the top of flange 48 so that when the porous element is tight against the bottom of the socket 38 a gas-tight or hermetic seal is present.

The recess 50 in the elongated piece 49 has a frusto-conical bottom providing a shallow axial convergence receding from the flat downstream face 52 of the porous element, forming a mouth 53 in which the gas leaving the element is collected and directed into the throat or restricted portion 4| of the mixed gas passage P. It will be noted that the throat 4| is of considerably less diameter than the outlet portion 54 of the passage P. The effect of the mouth 53 and throat 4| is to increase the collective velocity of the gas such that the gas itself will either blow out or greatly impede a flash back continuing after a backfire. 0n reaching the porous element, a backfire is readily and finally extinguished by the cooling eifect of porous material and by the tortuous shaped pores which cause the flame to come against many heat conductive walls (bronze containing a large amount of copper) and bend and quench it in many small parts through the numerous pores. The restricted portion 4| thus prevents premature breakdown of the porous element material by heat.

In that example of the invention shown in Figs. 4 and 5, it will be noted that the casing 35 of the assembly is of substantially the same shape as the casing of the previously described assembly, and that the only differences reside in the shape and construction of the mixed gas supply pipe and the porous element. A long hollow frusto-conical self-supporting porous element 64 is threaded at its large end upon a base 6| having a central mixed gas passage 62 for the delivery of the gases to the interior of the porous element. Threaded in the outer end of the porous element 6|, is a deflector or closure element 63 of solid or nonporous metal. An elongated pipe 64, generally more hollow than the pipe 49, has an enlarged chamber 65 adapted to receive the porous element and the base 6|. Base 6| has a radial flange 66 against which is abutted a flange 61 of the elongated pipe 64. Upon the coupling sleeve 42 being tightened in the threaded socket 38, base 6| and elongated pipe 64 are rigidly secured to the casing 35.

The gases upon coming together at the bottom of the outlet socket 38, pass down through the central passage 62 of the base 5|, fill up a chamber 63 in the porous element 68, and then pass outwardly through the pores of the porous element to the chamber 65 of the pipe 64. By the time the gases rea h the chamber 65, they are thoroughly and finally mixed. A restricted throat 69 in the pipe 64 increases the velocity of the gas the same as did the throat 4| in that form of the invention shown in Fig. 3. Any flames resulting from a backfire are diverted by deflector 63 upon entering the chamber 65. Each of

elongated pipes

40 and 64 has a threaded outlet end portion 1| adapted to receive the coupling 33 of the pipe connection 22 to connect the assembly 23 to the nozzle block 2|. Any sustained burning flashback flame is prevented by the high gas velocity in the throat 69 after backfire. The comparatively shallow chamber formed between the outer or downstream face of the porous element 69 and a wall 64 of the pipe or casing functions similarly to the chamber 53 in Fig. 3 in being of small enough volume to cause the outflowing gas to have a high enough velocity for the same purpose, i. e., preclude a continued burning.

In that form of the invention shown in Fig. 6 the gases entering the casing 35 are not permitted to be previously mixed prior to entry into a porous element 12. The porous element 12 lies within a flanged inner end 73 of a mixed gas delivery pipe 14, similar in configuration to pipe 48 of Fig. 3, and has a flat upstream face 15 which is brought up flush against a skirt portion a 16 surrounding the central gas inlet passage 46. By this construction, the gases from the

passages

43 and 46 directly enter the porous element 12 without being previously mixed and mixing takes place wholly within the porous element 12. Thoroughly mixed gases leave downstream face 11 of the porous element 12, and pass on downwardly through a restricted throat T8 of the pipe 14.

A self-supporting porous element suitable for the purposes of this invention may be formed of carbon particles compacted with a carbonaceous binder, such as pitch, baking the compacted mass slowly to drive off volatile matter, and then slowly cooling the element.

Another form of porous element which has been found to be satisfactory is that known to the trade as Porex, which is formed by sintering together a collection of bronze particles into a single selfsupporting mass forming circuitous pores through it. The sintering operation leaves the mass with certain of the pores interconnected with one another. The mass may be finally compressed, if found necessary, to reduce the pores to smaller size. As is well known, bronze being largely of copper is a good heat conductor to distribute the heat energy of backfire throughout the porous mass.

The pores of the porous element are in the form of circuitous passages, any one of which interconnects with or crosses several other passages and delivers portions of its gas to or receives portions of the gas of these other passages. The gases oi one pore are thus forced to mix and be mixed with gases of the other pores, with the result that by the time the gases have traversed the full thickness of the element, they are thoroughly mixed.

In many instances a hanging flame is precluded from continuing in the restricted portion of the elongated mixed gas passage. The porosity of the element is such that both eflective' mixing results and maximum flash back resistance is obtained. The overall size of. the element will depend upon the gas flow requirement. One porous element may be designed and arranged to serve several nozzles.

The length of the passage subject to flash back is materially reduced, and the gases are mixed and the backfire arrested in the same casing.

While various changes may be made in the detailed construction, it shall be understood that the changes shall be within the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

l. A combined porous type gas mixer and backfire arrester assembly for a blowpipe, comprising a casing having two separate gas inlet openings, an enlarged outlet opening, a pipe having end portion contained in the enlarged outlet opening, said pipe having an enlarged axially extending chamber and restri ted gas passage portion in communication with each other, a hollow frusto-conical porous element spaced from the wall of and extending within the enlarged chamber into close proximity with the restricted gas passage portion, a solid metal deflector piece closing the outer end of the porous element to divert a flamer sulting from the backfire issuing rearwardly from the restricted gas passage portion, a base connected to the opposite end of the porous element, said base having a mixed-gas passage therethrough to deliver the gases entering outlet opening to the interior of the porous element, and means securing the base and the pipe within the enlarged outlet opening.

2. A porous type backfire arrester assembly comprising in combination a porous element of heat conductive sintered and compressed metal particles strong enough to resist the impact of a backfire, said element having interconnected pores of tortuous shape small enough in size to preclude the passage of a backfire flame, whereby such a flame is extinguished by the chilling action of its impingement upon numerous heat conductive pore walls and such a flame is divided and frequently bent around munerous such heat conductive walls in the tortuous paths constituted by said pores, a casing enclosing said element, an inlet passage in the casing leading to an upstream face of the porous element and at least a 6 major portion of the upstream face of said element being exposed to gas from the inlet passage, an outlet passage in the casing leading from the downstream face of said element and at least a major portion of the downstream face of said element being exposed to said outlet passage for arresting any backfire flame, a shallow chamber in said outlet passage constituted on one side by the downstream face of said element and on an opposite side by a Wall of said casing, said element being gas permeable and mounted to require the passage of gas between the inlet and outlet passages to be through the pores of said element, said shallow chamber. being of small volume and the outlet passage adjacent thereto being constricted to prevent any continued burning or flashback to exist therein following a backfire.

3. In a blowpipe, in combination, a casing member portion having therein a gas mixing chamber, an oxygen supply passage opening into said chamber, and a fuel gas supply passage opening into said chamber, for preliminarily mixing oxygen and fuel gas within said gas mixing chamber; a combined gas mixer and backfire arrester comprising a self-supporting body of porous material secured within said casing member portion and having the pores exposed on at least a major portion of the upstream surface thereof in communication with said gas mixing chamber, to more thoroughly mix within said body of porous material the gases preliminarily mixed in said mixing chamber; and another casmember portion constituting a gas mixture delivery pipe secured to said first mentioned casing member and having an enlarged passage portion and also having a restricted passage portion communicating with said enlarged passage portion and With the pores exposed on at least a maior portion of the downstream surface of said body of porous material to any backfire flame, a shallow chamber constituted on one side by the downstream face of said porous material and on an opposite side by a wall of said second mentioned casing member portion whereby the velocity flow of the gas mixture through said restricted passage portion and shallow chamber inhibits propagation of flashback adjacent the downstream surface of said body of porous material, and said body of porous material arresting propagation of backfire therethrough and into sa d mixing chamber and into said fuel gas supply passage.

CLIFFORD C. ANTI-IE8.

REFERENCES crrnn The following references are of record in the file of this patent:

UNI-TED STATES PATENTS Number Name Date 713.421 Fouche Nov. 11, 1902 Re. 16,149 Southgate Aug. 25, 1925 1.223 308 Bone et al. Apr. 17, 1917 1.097264 Reich May 19, 1914 1,290,878 Barrows Jan. 14, 1919 2,235,433 Kohl Mar. 18, 1941 2,242,471 Jones et a1 May 20, 1941 2,008,130 Damm July 16, 1935 FOREIGN PATENTS Number Country Date 477,958 French Aug. 21, 1915 262,881 German Apr. 26, 1912