US2844452A - Self-sustaining regenerative process - Google Patents

Description

United States Patent O SELF-SUSTAINING REGENERATIVE PROCESS y Rudolph L. Hasche, Johnson City, Tenn. Application April 5, 1950, Serial No. 154,185

6 Claims. (ci. 48-196) This invention relates to gas reactions and more particularly.to novel regenerative apparatus and processes whereby a combination of endothermic and exothermic .gas reactions may be eiected at high thermal eiciency.

A primary object of the invention is the provision of a vcontinuous method for the production of low density heating gases, acetylene, oleiins, aromatics and other -endothermic gas reaction products by the partial combustion of exothermically combustible starting materials :such as hydrocarbons and ammonia.

required reheating of the refractory. Other conventional l practices require long heating periods for the hydrocarbon starting materials and yield an inferior product containing predominantly carbon monoxide, carbon dioxide and hydrogen.

It has now been discovered that low `density heating gases, unsaturated hydrocarbons including acetylene 'and other endothermic gas reaction products may continuously and substantially isothermally be produced by heating a nonllammable first mixture of an 'exothermically combustible -material and oxygen to effect incipient endothermic thermall alteration of the combustible material, thereby producing a ilammable second mixture, the so initiated endothermic reaction being propagated by the resulting exothermic combustion reaction, said combustion reaction being controlled by the limited amount of oxygen present; and thereafter rapidly cooling the product .so obtained, the heat resulting from said lcooling being employed to raise additional quantities of combustiblev material` and oxygen to incipient cracking temperature.

For example, in those instances where a hydrocarbon is employed as a starting material for the production of a heating gas, acetylene, or the like, the hydrocarbon is first mixed in non-flammable proportions with air or other `oxygen containing gas, and the mixture heated to the incipient thermal cracking temperature of the hydrocarbon. There is Iproduced in this manner a flammable second mixture containing carbon and hydrogen in addition to the hydrocarbon starting material. The combustion of this carbon and hydrogen together with a minor portion of the original hydrocarbon provides the heat required to propagate the endotherrnic cracking reaction. Heat released by the quenching of the product so obtained is utilized to heat additional quantities of the starting mixture to the incipient cracking temperature of the hydrocarbon. It will be appreciated that only a relatively `small porrc' ICC tion of the hydrocarbon or other combustible starting material, normally not more than about 15% to about 40% thereof, will be consumed by the limited combustion reaction. The balance of the starting material lwill be eiciently cracked or otherwise thermally altered by the heat released by such combustion. The sensible heat of the entire gas mixture will accordingly be raised to the flame temperature of the combustion reaction which is above that necessary to initiate thermal alteration of the starting material. Hence additional quantities of starting materialv and oxygen may be raised to the incipient thermal alteration temperature of the starting material through utilization of the heat released by the cooling of the product.

In the preferred embodiment of the invention the process is `carried out in a continuous regenerative manner by passing -a non-flammable first mixture containing an exothermically combustible starting material and oxygen through the channels of a first refractory regenerative mass from the cooler to the hotter ends thereof, thereby effecting incipient thermal alteration of the combustible starting material and producing a flammable second mixture, passing said second mixture into a combustion and thermal alteration zone `wherein the previously initiated endothermic thermal alteration reaction is propagated by the simultaneously occurring combustion reaction, thereby producing a third gaseous mixture hotter than the hottest portions of said first regenerative mass, and thereafter quenching said third gaseous mixture by passing the same through the channels of a second regenerative mass from the hotter to the cooler end thereof, the direction of flow of gases through said first and second regenerative masses being reversed at suitable intervals whereby a continuous yield of product is obtained.

The above described continuous regenerative process differs radically from the methods of the prior art `which entail alternate heating and production steps which result in an intermittent ow of desired product. Furthermore, the prior art teaches that the regenerative masses employed to effect the thermal cracking of hydrocarbons and the like must be preheated to a temperature in excess of tha-t required to initiate cracking, that is, that the regenerative mass must be at least as hot as the gases produced and that the mass must alone supply the heat requisite not only to initiate but also to propagate the exothermic cracking reaction. Such processes are necessarily attended by excessive heat loss and therefore of intermittent character occasioned by the constantly recurring necessity of reheating the regenerative mass.

In `contrast to such prior art processes, in this invention the product gases when produced are substantially hotter than the regenerative masses `with which they come in contact. That is, the regenerative mass is always at -a temperature substantially lower than the maximum gas temperature. Furthermore, in the actual cracking or thermal alteration phase the endothermic and exothermic reactions which occur are lsubstantially in balance. Hence, there is no significant heat loss in the system and the entire process is essentially isothermal. Operation at high temperatures without serious adverse effect upon the refractory of the #regenerative mass is thus `made possible.

The continuous refractory regenerative process of this invention is admirably suited by virtue of its continuous nature, both with respect to the introduction of starting materials and to the flow of the product obtained to 'operation under sub-atmospheric or super-atmospheric conditions. Accordingly, the process of the invention is appropriate for the production not only of heating gas and unsaturated hydrocarbons `from more saturated starting materials, but also may be employed to advantage in effecting other reactions involving the formation of endodirect proportion to the reduction in pressure below atmospheric of the `gases undergoing treatment.

Similarly, operation at super-atmospheric pressure is desirably employed for the production of higher oleins and liquid fuels from higher molecular weight starting 'materials Throughthe utilization of such super-atmospheric pressure the longer reaction and quenching periods which are of significance in the production of these materials may be achieved.

Certain critical limitations must be observed with respeci: to this process. AIt is required that the original mixture contain hydrocarbon or other starting material and oxygen. in nonflammable proportions to preclude excessive consumption of the starting material by combustion. Furthermore, only so much oxygen in desirably employed as is required to obtain the heat requisite to the production of the desiredA pyrolysis product. Air, oxygen or oxygen in-adrnixture with gases .inert under the conditions may be employed. Air is preferred.

These limits of combustible proportions of the various hydrocarbons and other combustible gases with oxygen are well Vknown to the art. Such data may be found for example in Handbook of Chemistry and Physics, 30th edition, 1947, p. 1506. The proportions of oxygen or air required to -form a combustible mixture with the preferred hydrocarbons for use in this invention and the `pref ferred proportions for use with these starting materials are set forth in Table I, for operations at atmospheric pressure.

1 Parts by volume of oxygen or air per part by volume of hydrocarbon It is also essential to the success of the process that both the hydrocarbon or other starting material and the oxygen be preheated to the incipient cracking or thermal alteration temperature. The addition of unpreheated oxygen or oxygen containing gas to the starting material raised to the thermal alteration temperature is unsatisfactory.

The hydrocarbon employed may be any hydrocarbon which is gaseous or may .be vaporized under the conditions and which is subject to thermal cracking. Thus low molecular weight compounds such as methane, vethane and the various isomeric propanes, butanes, hexanes, and mixtures thereof may be employed as well as higher molecular weight materials such as the octanes anl decanes and petroleum naphtha. Unsaturated materials may be employed. Low molecular weight, saturated, normally gaseous hydrocarbons such as propane and butane are preferred. However, liquid hydrocarbons maybe preheated or atomihzed andV introduced with air to produce good yields of the higher liquid olens.

The continuous regenerative embodiment of the proess of this invention is attended by a number of unique and outstanding advantages. As previously mentioned, the process may be carried out at high temperature without serious adverse effect upon the refractory of the regenerative masses utilized for the reason that such masses are always at a temperature substantially lower than the maximum gas temperature. Furthermore the cracking of hydrocarbons may be eeted at extremely high temperatures without the formation of appreciable quantities of carbon, thus obviating a serious problem inherent in the processes of the priorart. An additional outstanding advantage of the lprocess resides in the fact that the temperature of operation may automatically be controlled merely by controlling the composition of feed mixture of oxygen containing gas and combustible starting material employed. Furthermore, the process of this inyention represents an advance over the prior art in that there is a remarkably low pressure drop, generally not more than about 2.5 pounds per ysquare inch therefrom.

It willv be apparent that the above described process may be carried out in a plurality of ltypes of apparatus. PQI example, hydrocarbon and oxysenmight be introduced into soils and preheated t0 incipient cracking temperature, the hot gases mixed and the combined Crashing and combustion permita-adn@ ,take place in a cracking zone and the hot products cooled by passage i in heat exchange relationship with the aforementioned preheating coils. This mode Of operation is inexpedient in that it entails the use of expensive equipment and temperaturesattained are limited to those possible with alloy metal tubes and coils.

The process of the invention is preferably carried out however in a refractory regenerative furnace structure. It is essential however when such a structure is employed at substantially atmospheric pressure that the period of residence of the gases undergoing treatment in that portion of the regenerative mass wherein the gases are heated to the cracking. temperature of theI starting material not exceed about 0.3 second. A preferable range for thisV residence period is from about 0.05 second to about 0.1 second. It is likewise necessary that the period of residence of the gases undergoing treatment in that portion of the regenerative furnace wherein the simultaneous combustion and cracking reaction occurs not exceed about 0.05 second. A preferable range for this period of residence is from about 0.01 second to about 0.03 second. As the product gases are quenched bypassage through a second regenerative mass, the same limits of residence time obtain as those previously defined with respect to the initial heating step.

The foregoing limits ywith respect to residence time apply to operations conducted at atmospheric pressure which are suitable for the production of heating gas, lower olenic hydrocarbons and the like. When it is desired to produce acetylene, nitric oxide, hydrazine, hydrocyanic acid and the like, which products require very short residence time in the regenerative masses and extremely rapid quenching, the process of the invention is effected at suba'tmospheric pressure. The foregoing limits will in such cases be reduced t o an extent corresponding to the reductionV in pressure of operation. For example, if the process is effected at a pressure of about one-third atmosphere absolute, the residence time and quenching time can preferably be reducedto below 0.01 second.` Likewise, when operating at super-atmospheric pressure for the production of higher liquid olefinsaromatics and the like, correspondingly 'longer residence periods which favor the reactions yielding such products are employed. Thus, at a pressure oftwo atmospheres residence times as great as about 0.3 second may be employed. Similarly, when oxygen is utilized. in lieu of air, the residence time in` the furnace may be reduced to about one-half of that required with analogous operations conducted with air. Thus, Vthe residence time when oxygen is utilized may be reduced to 'a few thousandths of a second. It will be obvious ythat the reduction of residence and quenching periods by the reduction in pressure in the s/stem can be accomplished without appreciable change in pressure drop through the regenerative mass because only the lineal gas Velocity is increased, not the mass velocity. This feature of restricted pressure drop constitutes one of the salient advantages of this invention.

It is also necessary when a refractory regenerative furnace structure is employed that the pressure drop in the apparatus not exceed about 5 pounds per square inch. A preferable range is from about l pound per square inch to about 2.5 pounds per square inch.

The provision of one type of novel regenerative furnace structure in which this process may be carried out is one of the salient and primary features of this invention. Briey stated, the furnace of the invention comprises two regenerative masses having a plurality of uninterrupted ues or slots passing therethrough. Each of said regenerative masses is provided with a free space at one extremity of the flues for the introduction or withdrawal of gases. The opposite extremities of the regenerative masses are interconnected with an insulated combustion chamber which is provided with a heating means. Each of the aforementioned free spaces is provided with gas admission and withdrawal means which are in turn associated with means for causing a gas to flow from the aforementioned free space of one regenerative mass through the iiues or slots thereof into and through the combustion chamber and thence through the ilues of the second regenerative mass. Means for the reversing of this gas ilow are also provided.

This novel furnace structure will now be described in detail with reference to the accompanying drawings in which:

Figure 1 represents partly in vertical section, partly diagrammatically a complete apparatus in accordance with the present invention, and

Figure 2 represents a horizontal section taken on the line A-A of Figure 1.

In Figure l there is shown a refractory insulated chamber 1 containing two contiguous regenerative checkerworks 2 and 3 both of which are provided with straight, uninterrupted flues 4. Checkerworks 2 and 3 are separated by gas-tight wall S and respectively provided with gas inlet and withdrawal spaces 6 and 7, which are in communication with flues 4. Above the regenerative checkerworksZ and 3 there is provided an interconnecting chamber 8 which is in communication with the upper extremities of ues 4 of both regenerative checkerworks ' i 2 and 3. Chamber v8 is provided with heating means 9, normally a burner for gaseous or liquid fuel. Gas inlet and withdrawal lines 10 and 11 connected respectively with gas inlet and withdrawal spaces 6 and 7 are connected through lines 12 and 13 respectively and threeway valve 14 to line 15 which in turn leads through valve 16, line 17, valve 18, pump 19, and line to a source of hydrocarbon and oxygen containing gas not shown. Valve 18 and pump 19 may be bypassed through line 21, valve 22 and line 23. Likewise, gas inlet and withdrawal lines 10 and 11 are connected through lines 24 and 25 respectively to three-way valve 26 and withdrawal line 27 which in turn leads through valve 28, line 29, valve 30, pump 31 and lines 32, to storage means not shown. Valve 30 and pump 31 may be bypassed by line 33, valve 34 and line 35.

Lines 1t) and 11 are also connected respectively to lines 36 and 37 which function as chimneys duringthe initial heating of the furnace. Lines 36 and 37 are respectively provided with valves 38 and 39.

Very high heat transfer, short residence periods, and low pressure drop in the regenerative furnace are absolutely essential to the successful practice of the previously mentioned process for the production of low density heating gas as well as acetylene, other unsaturated hydrolil 6 carbons and other endothermic reaction products. To' this end it is necessary that the above described furnace structure and modifications thereof embraced by this invention conform to certain definite structural limitations. lt is critical and essential that the length of the regenerative checkerworks 2 and 3 not exceed about fifteen feet in length. Likewise regenerative checkerworks of vless than about four feet in length are impractical although the lower limit is not critical. A preferred length for the regenerative checkerworks is from about six feet to about ten feet.

It is also essential that the gas passageways or ues 4 in the regenerative checkerwork not exceed about 0.75 inch in maximum width or diameter. The lower limit of operable width or diameter of such ilues is not necessarily critical but must not be so small that excess pressure drop in the furnace occurs as a consequence thereof. Generally, flues of maximum Width or diameter of from about 0.75 inch to about 0.25 inch may feasibly be employed. Flues of maximum width or diameter of from about 0.375 inch to about 0.5 inch are preferred. It will be apparent that mere masses of promiscuously deposited 'heat absorbing solids are unsatisfactory regenerative masses for the furnace of this invention.

It is also essential that the ratio of the total volume of the ues 4 in each regenerative checkerwork 2 or 3 to the total volume of the checkerwork in which the flues are located not exceed about 1:3. A preferred range for this ratio is from about 1:4 to about 1:10, and a practical lower limit is about 1:20. This lower limit, however, is not critical except insofar as pressure drop is concerned.

A particularly appropriate type of checker brick for use in the construction of the regenerative checkerwork of the furnace of this invention is that described and claimed in my copending application Serial No. 129,969, entitled Regenerative Packing Construction, led Novem- 'ber 29, 1949, and now abandoned. These checker bricks are prepared from any conventional refractory material such as the various calcium, magnesium aluminum silicon, iron, chromium, etc. oxides and mixtures thereof. Furthermore, as a consequence of the thermodynamic advantages of the process of this invention in the lower or cooler portions of the regenerative masses, a checker- Work metal such as iron or copper or a checkerwork graphite may be employed. Preferably the bricks are prepared from a material having a high alumina content to obtain maximum heat capacity, high refractoriness, high thermal stability and inertness toward the gases undergoing treatment.

The novel placement of the ues or gas passages 4 in this checker brick is diagrammatically shown in Figure 2. It will be observed that all of the flues are equidistantly spaced from all the next closest adjoining ues and that accordingly the thickness of the walls between each ue and the next adjoining flue is uniform. As shown in the drawing, for example, each flue is circular in shape and has a diameter of about @Vs inch. Furthermore, it is approximately 1]/16 from the center of each flue to the center of each of the next most closely adjoining dues. Obvious variations in relative size and shape of the fiues and interwall thickness are operable within the previously dened limits with respect to maximum slot size and volume. Conventional checker bricks of other types than those described in aforementioned application Ser. No. 129,969 may of course be employed if the aforementioned limits are observed.

It is further required that the volume of the combustion chamber 8 not exced about 60% of the combined volume of the ues 4 in both of the regenerative checkerworks 2 and 3. It is preferred that the volume of the combustion chamber 8 be equal to from about 20% to about 40% of the aforementioned combined volume of the ilues 4.

Operation of the furnace and process of the invention to produce a low density heating gas from propane and bers 6 and 7 and thence out of `thefurnace through lines During passageY through flues 4 thehot combustion `gases produced by` 'and 36 and 11 andv 37 respectively.

heating means 9 give up heat to regenerative checkerworks 2 and 3." The heat ,transfer-*efficiency resultant from the construction and dimensions of the regenerative;

checkerworks 2 and 3,`previously described, is'suchithat the combustion gases leavethefurnace at a temperature ofabout 100 C. This procedure is continued until the top of the regenerative checkerwork is in excess of 1000 C., preferably within the-range of 1100" C. to about 1300" C. There is thus provided a temperature gradient in the mass ranging fromabout .100 C. at the bottom to the temperatures in excessof: 1000 C. in the top thereof.

Alternatively, the heating means 9 may be turned off after the top of regenerative checkerworks 2 and 3 has reached a temperature above the ignition temperature of the fuel employed, generally, about .550 to 650 C., valves 18, 30, 38 and 39closed and valves 16, 22,28 and 34 opened. Combustible material is then introduced throughlines and 2.3, Valve 22, lines 2 and 17, valve 16, line 15, valvel4 and lines 13 and 11 to gas inlet 7 from which it passes upwardly through ues 4 of regenerative checkerwork 3 wherein it is heated to ignition temperature. The heated vcombustible material then passes into combustion space 8`where it burns. The combustion products then pass down .through ues 4 of regenerative checkerwork 2Linto gas withdrawal space 6 and.

thence out of the furnace through lines 10 and 24, valve 26, line 27, valve 28, lines29. and 33, valve 34 and lines- 35 and 32. This gas` flow is reversedat suitable intervals by reversing three-way valves 14andI 26., Thevtempera-fture conditions so obtained in the mass correspond toV those previously described.

This alternative method of :heating is particularly advantageous in thata very high ilame temperature is obtainedin chamber with attendant decrease in the time required to. heat the furnace. Furthermore, the high temperature zone at the top of regenerative checkerworks 2 and 3 is shorter in length than that yresulting Vfrom the rst described heating method. This result' is particularly advantageous when it is desired to produce amaxirnumy quantity of unstaturated hydrocarbons in a short residence time at high temperature.

The operation of the heated furnace to produce low density heating gas by the partial combustion of hydrocarbons is much the same as the last described heating method. A mixture containing hydrocarbons consisting predominantly of propane and air in non-combustible proportions of about one to two is introduced through lines 20 and 23, valve 22, lines 21 and 17, valve 16, line' 15, valve 14, and line 11 into gas inlet space 7. The mixture is thenpassed upward through ues 4 of checkerwork 3. In the course of such passage the temperature of the propane is raised until near the top of checkerwork sutlicient cracking has occurred to render the gas mixture flammable. It will be appreciated that carbon and hydrogen will be formed by the cracking .and that the 4materials will be ammable even with thelimid amount of oxygen present. Since there is a deficiency of oxygen, however, only a portion of the combustible materials will be consumed. However, only about 15% to about 40% of original hydro-carbon employed is so dissipated. The balance of the hydrocarbon in the case under consideration,` predominantly propane, is efficiently cracked `by the heat released by the aforementioned combustion reaction. The combustion. l and cracking reactions v predominantly 8 occurin combustion chamber 8 where -it will be noted the endothermic and exothermic heat are substantially equally balanced. It will be obvious that the exothermic heat from the .combustion .will Ibe absorbed by the endothermic cracking reactions. Furthermore, the sensible heat of the entire gasrmixtureis raised to the flametemperature of I .the `combustion reaction.

By virtue of the type and dimensions of the checkerworks 2and3'and chamber 8 .ofthe furnace of this invention-,: the contact 4time of the. gases in chamber 8 is extremely short, i. e., lessthan about 0.025 second with the` result that=extremely .high yieldsl of unsaturated hy.- drocarbons are obtained.

Subsequent tothe combustion and cracking reaction which predominantly'occurs in chamber 8, the gas mixture produced passes ,downwardly through flues 4 of checkerworks 2 andgivesup heat thereto. The mixture then passes out throughichamber 6,. lines 10 and 24, valve 26,` line 27,'valve 28,:1ines129'and 33, valve 34 and lines l35and:.32a tostorage.; The temperature of the gas leaving the furnace will be .aboutf` C.-15 0 C.. which evideneeshighthermal eiciency.

The-.gas flowthr'oughthe furnace iscontinued in the manner specied for approximately one minute and threeway-valves 14-and 26 `are .then simultaneously reversed. This. reversal;is preferably accomplished in a fraction of a second, .infact soquickly that the continuous flow of productV gas passing through line 25 -is not interrupted. The reversalof ftlow'transfers the stream of inlet gas throughrvalvef14,.lines 12 and 1t) and chamber 6 into fluesfi of checkerwork 2.'` The. gas passes upward through flues 4, checkerworks 2, is heated to partial cracking, undergoes simultaneous cracking and combustion in chamber-8,2 is quenched-'ingcheckerworks 3 and passes out Vthrough chamber 7, lines 11 and 25, valve 26, line 27 and valve '28,'l lines 29 'and.33,'valve 34 and lines 35v and 32tovstorage.- The 'gas-flowis again quickly reversed after operation for one minute and the process so operated continuously.: After a period of such continuous operation, the maximum temperature of the regenerativel checkerworksle'vels-l oifatabout 800 C. to 900 C., normally 850 C."

The` gas product obtained had Vthe following composition in percent by volume:

Thevolume :of the-product gasV as compared with the inletV mixture vis 1.37. The heating value of the constituents of the `product gas per'unit volume is 97% of thatof.- the `propane contained in a unit volume of thev Ifeed:v

Itv willbe apparent-,from the foregoing that this inven tion embraces a continuous regenerative process for the production of heating :gas containing unsaturated hydrocarbons. This process operates at very high thermal efiiciency'b'y supplying heat internally and by combustion and heat transfer. The exothermic heat is generated by combustionof-a portion of the cracked hydrocarbons in a restricted combustion chamber located immediately above the.V checker sections.

The lprocess is completely reversible and-establishes a steady state-which continues indenitely. It is particularlyadvantageous rin that no reheating, relocation or condensation` heating zones, in the regenerative f mass is 9 required other than that resultant from the simple reversalv of gas iiues herein discussed. Furthermore, the absence of rapid and extreme Itemperature changes greatly prolongs the life of the regenerative checkerwork and thereby effects substantial economy.

The operation of the furnace in the manner above described results in the continuous production of low density heating gas containing a high proportion of olenic t hydrocarbons. This mode of operation, while admirably suited to the production of such heating gas is not adapted to the production of acetylene in high yields `for the reason that operation under reduced pressure and a more rapid quenching is necessary to prevent decomposition of that product.

Operation at sub-atmospheric pressure may be eiected in the apparatus of this invention through utilization of vacuum pump 31. To obtain the benefits of pump 31, valve 30 is opened and valve 34 is closed. Valve 22 or 16 may be throttled to maintain the desired vacuum. The apparatus is otherwise operated in the same manner as that previously described for operation at atmospheric pressure. A vacuum as great as about 0.2 atmosphere absolute may be obtained. Such reduced pressure operations are particularly suitable for the production of acetylene, hydrazine and other products which require rapid quenching to prevent decomposition for the reason that the residence time of the gases undergoing treatment in the refractory regenerative furnace can be reduced lin proportion to the reduction in pressure below atmospheric. Likewise, yields of acetylene and the like are increased by the low ypartial pressure of suchproduct gases in the re Table II Starting Material Oxygen Air Methane 0. 2. 6 1-3 Ethane 2-4 Propane.. 3 5 Natural G 1-3 Operation of the apparatus in this invention under a reduced pressure of about 0.2 atmosphere absolute utilizing a starting material comprising a mixture of air and natural gas in the ratio of about 2.75 volumes of air per volume of natural gas, yielded a product having the following composition in percent by volume.

Carbon dioxide 1.4 Acetylene 7.5 Carbon monoxide 6-.2 Hydrogen 28.0 Methane 2.4 Nitrogen 54.5

It will be observed that the yield of acetylene obtained is more than 60% of theoretical, a higher yield than has heretofore been reported by any commercial pyrolysis operation. Thus, the novel apparatus and process of this invention makes possible a continuous method for the production of acetylene under reduced pressure and under the optimum conditions of extremely short residence time, i. e., 0.01 second or less, in the reaction zone combined with extremely rapid quenching. Accordingly, there has been developed for the first time a continuous regenerative lfurnace operation for the production of acetylene which is operable under a wide range of pressures and which is attended by no disturbing pressure changes or other adverse effects. An additional result which has been achieved by this invention is the production of acetylene in excellent yield rwhich contains no appreciable contamination of carbon particles. Hence, the difficulties of separation of carbon from the product acetylene is largely obviated.

It will be appreciated that the method and apparatus of this invention is equally adapted to continuous operation at super-atmospheric pressures and may be employed to effect endothermic gas reactions which are favored by such conditions. To achieve this purpose, valve 30 is closed, valve 34 is opened, valve 22 is closed, and valve 18 is opened. T-he starting materials are introduced through line 20, in pump 19,'the process otherwise being conducted in the manner previously described for operations at atmospheric pressure. Valves 28 and 34 may be throttled to maintain the desired pressure in the system.

The novel process and regenerative furnace of this invention constitute a significant advance in the art typified by many advantages such as those hereinbefore described.

Obvious modifications of the process and apparatus may be made. Thus, if desired, the furnaceA might be operated intermittently. Such a mode of operation however, would dissipate the advantages of continuous production of product gases which constitute one of the salient features of the invention.

The apparatus of this invention may also be operated by the continuous addition of a portion of the product to be pyrolyzed through openings in heating means 9. As previously pointed out, however, such a mode of operation reduces the thermal efficiency of the furnace and negatives the advantages of the unique structure of thev furnace.-

Obvious modifications of the apparatus and process of this invention will be apparent to those skilled in the art. It will be understood that the scope of the invention is restricted only by the sub-joined claims.

What I claim is:

1. A self-sustaining regenerative process for continuously effecting endothermic reactions with uid reactants which comprises flowing a non-ammable mixture containing hydrocarbon and air through continuous channels of a regenerative mass progressively hotter in the direction of gas flow to pre-heat said mixture and effect incipient endothermic cracking of the hydrocarbon in the regenerative mass to produce a arnmable mixture, iiowing the flammable mixture through a combustion and endothermic alteration zone simultaneously to burn a portion of the hydrocarbon and endothermically to alter substantially all of the remainder of said hydrocarbon, said burning supplying all of the required heat for said endothermic alteration and producing a gaseous effluent having a temperature higher than that of the regenerative mass, iiowing the said eliluent through continuous channels of a second regenerative mass progressively cooler in the direction of flow to quench said effluent and to transfer the sensible heat thereof to the second regenerative mass in an amount substantially equivalent to the amount of sensible heat removed from the first regenerative mass in the pre-heating step, rapidly reversing the flow of non-flammable gaseous feed mixture when the temperature of the first regenerative mass falls below that effective to pre-heat the said gas and by incipient cracking produce a fiammable mixture and the temperature of the second regenerative mass rises above that effective to quench the effluent; the period of residence of the gases undergoing treatment in each of the regenerative masses not exceeding about 0.3 second, the period of residences of the gases undergoing treatment in said combustion and thermal alteration zone not exceeding about 0.05 second, said residence periods being calculated at atmospheric pressure, the pressure drop of the gases passing through said regenerative masses not exceeding about five pounds per square inch.

entamer.

2. Ai process. according atoz, claim .1 foi'.` proclucingtras heating. gas;v in ,rwhich the feed gasi comprisesr `:a Anon, ammablemixturerlofxair :and methane, the ratiol of' ait? 1 to vmethane being about 1-3 .5: 1.

3. A-p1jocess5iaccording to1claimr1 forproducingwza heating gas in which the feed gas comprises-anon*v ammable: :mixture: :of fair :.-and I va gaseous-: hydrocarbon havingzgat sleastfltwo carbon; atoms:

4.\fAf-process\;according1to1 c1aim,.1 fon. producing a heatingxfgas, 1in':which:the-feed: gas icomprises' `a 'non-A arnmable, mixture-of air;.and,propane, the ratio of. air to propanefbeing: abouti-5:1.

5.,A processiaccordingto claim r1 fonproducingxa heat-.. inggas'finzwhich theieedf gas; comprisesV a :non-amnrableV f mixture: of :airl andrfbutane, the ratio; of A-air to butanerbeingf Y about-1.5.-6.5 :.1.4

6.- A:'self-sustaininggregenerative -process ,for continu ously eectingendothermic reactions Awith, uid. reactants which `comprises initially burning a gaseous tfuelwithnsub.- z stantially. complete :combustion in a combustion zone disposed between two regenerative masses-having continuous channelstherethrough, owing the hot products of ,combustion-sirnultaneously through the channels zof the regeuerativernasses until a temperature gradient is established in, eachwof themasses ranging froma temperature in excess of 1000 C. at the ends thereof adjacent the f combustion zone to a temperatureofV 100 C. at .the `opposite .endsthereo discontinuingysaid Iburning when vsaidy gradientis established, owinga non-flammable mixture containinghydrocarbon vand air through the. continuous channelsof the first regenerativemass progressively hotter in -Ythe `direction of gas flow to lpre-heat said mixture and eiect incipient endothermic cracking of the hydrocarbon".v in thegenerative massto produce a flammable mixture, owingtheammable mixturer through thel combustion zone ysimultaneously to `burn a portion ofthe hydrocarbon andendothermically to alter substantially al1 lofthe remainder of said hydrocarbon, said partialfburning sup,-

plying-heat'llosses offthe system and all `of the-required heat,forxsaidulendothermic .alteration and yproducing-"a gaseous `eiiluentilhaving a temperature higher'than' that ofd the, regenerativer mass; owing .the saicly efuent :through :the continuous channels ,of thevsecond regenerative mass:-

progressivelycooler inithe Adirectioniofiowr to; quench tureof the secondregenerati-ve mass risesA about that effec"- tive to quench thetefuent.; the period 'offresidence'of the gases undergoing-treatment in-each of the regenerative,

masses '.notexceedingabout .0.3 second, the, period of resi-vdence` ofv -the'` gases :undergoing treatment Y in saidcom-i` bustionand thermal ,.alterationzone not v exceeding labout 0.05.second,-,said residence periodsbeing calculated at.y

atmospheric t pressure, andl saidprocess Vhaving a thermal eficiency of atleast about. 90%.

References .Citedin the le of this patent UNITED STATES PATI-LSITS-V 1,023,783 Knapp.:4 Apr. 16',19112 i 1,721,735; 1 Isley:-A t. July23,-`1929/ 1,8()8,168f.. Hopkins; June 2.,'. 1931' f 1,848,184 f' Mawha s; Mar.8, 19321 1,850,291-. SeguyL Mar; :22, 11932Y l 1,907,029 Andrews et al. May;2:1933 1,940;209-- Fischersetal.: Dec. v19,11933 1,995,136 f Winkler etal'. Mar.V 19,31935 2,275,232 Rice; Mal'.V 3, :1942,

FOREIGN PA'1`l` `l`\l'-1`SYV 265,234. GreaLBritain Jan.v31, .1927.

Claims (1)

1. A SELF-SUSTAINING REGENERATIVE PROCESS FOR CONTINUOUSLY EFFECTING ENDOTHERMIC REACTIONS WITH FLUID REACTANTS WHICH COMPRISES FLOWING A NON-FLAMMABLE MIXTURE CONTAINING HYDROCARBON AND AIR THROUGH CONTINUOUS CHANNELS OF A REGENERATIVE MASS PROGRESSIVELY HOTTER IN THE DIRECTION OF GAS FLOW TO PRE-HEAT SAID MIXTURE AND EFFECT INCIPIENT ENDOTHERMIC CRACKING OF THE HYDROCARBON IN THE REGENERATIVE MASS TO PRODUCE A FLAMMABLE MIXTURE. FLOWING THE FLAMMABLE MIXTURE THROUG A COMBUSTION AND ENDOTHERMIC ALTERATION ZONE SIMULTANEOUSLY TO BURN A PORTION OF THE HYDROCARBON AND ENDOTHERMICALLY TO ALTER SUBSTANTIALLY ALL OF THE REMAINDER OF SAID HYDROCARBON, SAID BURNING SUPPLYING ALL OF THE REQUIRED HEAT FOR SAID ENDOTHERMIC ALTERATION AND PRODUCING A GASEOUS EFFLUENT HAVING A TEMPERATURE HIGHER THAN THAT OF THE REGENERATIVE MASS, FLOWING THE SAID EFFLUENT THROUGH CONTINUOUS CHANNELS OF A SECOND REGENNERATIVE MASS PROGRESIVELY COOLER IN THE DIRECTION OF FLOW TO QUENCH SAID EFFLUENT AND TO TRANSFER THE SENSIBLE HEAT THEREOF TO THE SECOND REGENERATIVE MASS IN AN AMOUNT SUBSTANTIALLY EQUIVALENT TO THE AMOUNT OF SENSIBLE HEAT REMOVED FROM THE FIRST REGENERATIVE MASS IN THE PRE-HEATING STEP, RAPIDLY REVERSING THE FLOW OF NON-FLAMMABLE GASEOUS FEED MIXTURE WHEN THE TEMPERATURE OF THE FIRST REGENERATIVE MASS FALLS BELOW THAT EFFECTIVE TO PRE-HEAT THE SAID GAS AND BY INCIPIENT CRACKING PRODUCE A FLAMABLE MIXTURE AND THE TEMPERATURE OF THE SECOND REGENERATIVE MASS RISES ABOVE THAT EFFECTIVE TO QUENCH THE EFFLUENT, THE PERIOD OF RESIDENCE OF THE GASES UNDERGOING TREATMENT IN EACH OF THE REGENERATIVE MASSES NOT EXCEEDING ABOUT 0.3 SECOND, THE PERIOD OF RESIDENCES OF THE GASES UNDERGOING TREATMENT IN SAID COMBUSTION AND THERMAL ALTERATION ZONE NOT EXCEEDING ABOUT 0.05 SECOND, SAID RESIDENCE PERIODS BEING CALCULATED AT ATMOSPHERIC PRESSURE, THE PRESSURE DROP OF THE GASES PASSING THROUGH SAID REGENERATIVE MASSES NOT EXCEEDING ABOUT FIVE POUNDS PER SQUARE INCH.

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