US2293421A - Apparatus for production of gas - Google Patents

Description

2 Sheets-Sheet l H. BAETZ Filed May 16, 1940 APPARATUS FOR `PRODUCTION OF GAS Aug. is, 1942.

Aug.l 18, 1942. H. BAETZ APPARATUS FOR PRODUCTION OF' GAS Filed May 16, 1940 2 Asheets-sheet 2 Pateniecl Aug. 18, 1942 UNITED STATES PATENT OFFIQE APPARATUS FOR PRODUCTION OF GAS Henry Bactz, Brookline, Mass.

Application May 16, 1940, Serial No. 335,551

8 Claims.

This invention relates to methods of and apparatus for the production of gas, and particularly where high temperatures are necessary in its production. The principles of the invention are applicable to a wide variety of uses but they are herein shown for illustration as applied to a high temperature vapor-phase cracking still for the cracking of petroleum, such that toluol and other aromatic fractions of petroleum oil which require relatively high cracking temperatures may be obtained in a practical manner.

In the described embodiment of the invention submitted for illustration, a high temperature vapor-phase cracking still is shown presenting a path of travel for the oil through a tubular conduit. In the case of tubularV conduits heretofore used for similar purposes, where the maintenance of temperatures in excess of 1000F. has been attempted, serious diflculties have been encountered due to the rapid formation of carbon, which soon lls and chokes up the tubes so that the still has to be shut down with great frequency until the tubes have been opened and cleaned and the carbon removed. The consequent dismantling of the parts involves expense and a loss of f time and makes the process relatively inefcient.

I have found that this rapid and excessive formation of carbon is promoted by .an unnecessary prolongation of the cracking operation. The

difficulties heretofore experienced in that respect are due in part to the relatively low velocity under which the oil travels through the tubular conduits serving to transfer the cracking heat to the oil,

and in part to the relatively low heating capacity pediting and hastening the cracking operation,

this by increasing the velocity of travel of the oil through the conduit and by greatly increasing the exposed area of the heat transfer walls of the conduit in proportion to the volume of oil enclosed by such walls. l

Another object of the invention is to provide a cracking still with such provision that the carbon, when and as formed within the passages of the tubular conduits, may be quickly removed without opening or dismantling the tubes, this being accomplished by the action of steam or water directed against the carbon while an adequate temperature is maintained about the tubular conduits to result in the formation of water gas, whichis thereupon conducted through and dischargedfrom the still.

In the drawings:

Fig. 1 is an elevation, partly in section, showing a tubular cracking still embodying one form of the invention;

Fig. 2 is a section in plan on the line 2--2 in Fig. 1;

Fig. 3 is an enlarged detail in sectional elevation, partly broken away, showing the construction of each tubular conduit;

Fig. 4 is a cross-section of the tubular conduit in plan taken on the line 4 4 in Fig. 3; and

Fig.5 is a detail showing one of the curved vanes introduced into the annular space presented by the tubular conduit to impart a rotary movement to the petroleum. Referring to the drawings and to the illustrative embodiment of the invention there shown, the still is contained Within a walled casing of refractory material forming the heating chamber of the still and comprising the end walls I, side walls 9, and top and bottom walls II and I3, the casing being supported on a base I5 by vertical steel buck-stays or I-beams I'I.

At one end there is provided a combustion chamber I9 to serve as `a source of heat for the still, this chamber being also constructed of refractory material. Any suitable fuel may be used, but herein there is shown for that purpose a conventional oil burner 2|. The products of combustion pass over the baiiie plate 23 through an opening 25 in the adjacent end wall 1 of the casing and into the still chamber formed within the casing.

The still chamber is sub-divided into successive c'cmpartments by a series of baille walls 21 and'29, also of refractory material. These walls are arranged in alternation, the iirst of which 2'I extends upwardly from the bottom wall I3 of the chamber but terminates short of the topwall, and the secondof which 29 extends downwardly from the top wall'but terminates short of the bottom wall, the succeeding baille walls being similarly arranged in alternation. The result is that the products of combustion from the furnace have a continuous path upwardly through the first compartment, then downwardly into and through the second compartment, upwardly through the third compartment, and so on, until they pass out of the still chamber through the flue exit 3 I' for the waste gases at the top of the last compartment.

In each compartment of the still chamber, and exposed to the heat of the products of combustion, there is positioned an upright tubular conduit through which the petroleum oil is caused to travel in a direction counter to that of the flow of the heated combustion products, the tubes being so related as to provide for a continuous flow ofv their contents from one end of the still to the other, as will be more fully described. Where reference is made to the flow or travel of the oil, it will be understood that the latter term includes the oil either in its entering liquid state or its subsequent gaseous state.

The several successive tubular conduits are of substantially the same construction, the latter being shown more in detail in Fig. 3. Each conduit consists of an outer tubular member 33 having a flange 35 at each opposite end. When installed in the still this tube, as shown in IFig. 1, extends from the bottom wall to the top wall of the still casing.

At its bottom this tubular member is bolted to a companion iiange 31 carrying a cap-like extension 39 and constituting a closure for the bottom of the tube 33.

At its top the flange 35 of the tubular member is bolted to a flange 4I which carries a second tubular member 43 constituting in effect an extension of the tube 33 but contracted at its top to close the space 45 within the tube 43. At the side of the tubular extension is a pipe connection 41 through which for certain of the tubes the oil to undergo cracking is admitted and for others it is disch-arged.

The passage through which the oil travels is provided by an annular space 49 (Figs. 3 and 4) formed between the outer tube 33 and an inner tube 5|. This provides a double-Walled annular passage for the oil of relatively small crosssectional area as compared with circumferential surface presented to the oil by the outertube 33, the walls of which are exposed to the heat of the products of combustion of the surrounding heating compartment. The inner walls of the tube 33 may be spaced so closely from the outer walls of the tube 5| as to provide a relatively high capacity forthe transfer of heatto the oil within the annular space.

Such heating capacity is substantially inversely proportional to the factor represented by the cross-sectional area of the annular passage through which the oil flows divided by the inside perimeter of the outer tube.

For example, with an outer tube having an inside diameter of 5%, inches and an inner tube 5| having an outside diameter of 4% inches, the

width of the annular space through which the Aouter tube from the inner tube.

of the proportions indicated in the described still, the velocity of travel of the oil through the conduit is correspondingly increased for any given volume of oil fed through the still.

The inner tube 5I has its lower end, which may be either closed or open, extending nearly but not quite to the closed bottom of the outer tube cap piece 33 to maintain the annular passage throughout substantially the full length of the tube 33'. At its upper end, just above the flange 4|, the inner tube 5| is contracted and its end closed about and supported by the still smaller innermost tube 53. The latter extends substantially the full length of the tubular conduit and has its lower end opening into the space provided by the cap-like extensionl 39. This provides a counter flow path of travel for the oil which passes down or up through the annular passage 49, as the case may be.

vThe cross-section of the passage presented by the innermost tube 53 is preferably not materially different from that presented by the annular passage 49 between the outer tube 33 and the next inner tube 5|, so that there is no change in the velocity of flow of the oil but a substantially uniform velocity is maintained under all conditions. TheV small inner tube Yin turn passes through and is fastened to the contracted end of the tube extension 43 and its protruding end is connected to the curved tubular pipe 55, by which communication is had to the next tubular conduit of the series. In the travel of the oil through the conduit the space between the innermost tube 53 and the enclosing tube 5I remains as a dead or inactive space.

The several tubular members which form the conduits for the oil are formed of heat resisting metal, such, for example, as a chromium molyb denum steel alloy.

When installed in the still chamber, the upper part of each tubular -conduit passes through a surrounding disk-shaped block 51 of refractory material which fits closely into an opening in the top Wall. This block surrounds and protects the bolts of the flanges 35 and 4| but is formed in segments so that on removal of the conduit the flange bolts are-accessible for separating the Each conduit is supported by Vone or more horizontal supporting members 58, shown partly broken away, to which the tubular extension 43 of the conduit is attached by connections, the details of which are not herein shown.

square inches, so that the factor referred to is 'to secure the required heat transference for the oil the ratio of the cross-sectional area of the annular passage to its outside perimeter with which Vthe oil contacts should be not more than 1.0.V

It will be seen that with an annular passage At the bottom end the flanges 35 and 31 of each tubularconduit are protected by a similar disk-shaped block Y59 of refractory material which has a close fit in .an opening 3| in the bottom wall |73 of the casing but is slidable therein so that expansion and contraction of the suspended tube may readily take place while the still is in operation. The tubes near the furnace end of. the still are subject to higher temperatures than those at the opposite end of the chamber and successive tubes therefore tend to expand unequally. Since each tube presents passages for a two-way travel of the oil, communieating connectionsV are required only at the top of the conduits, no connections being necessary be tween the bottoms of the tubes, and such un equal expansion movements accordingly may readily take place, each tube adapting itself to the heat expansion requirements independently of the others.

The opening 6| in the bottom wall I3 is closed by a refractory cover 63 resting on the support 65. By displacing this support, the cover may be removed and access had to the bottom of the conduit.

By disconnecting the pipe connections 55 and 41 the entire tubular conduit may belifted from the outer chamber and the outer tube 33 separated from the inner tube for the purpose of replacing a burned out tube or for any other purpose.

In the operation of the cracking still, the oil is delivered from any suitable source of supply (not shown) to the feed pipe 61 and forced by the pump 69 through the pipe connection 41 into the chamber 45 of the tube extension 43 for the first tubular conduit, or that located in the last of the several heating compartments of the still. The pressure employed will depend more or less on the length and the cross-sectional area of the passages provided by the series of conduits, the pressure used and the cross-sectional area of such passages, however, being preferably selected to impart a relatively high velocity to the oil. As an example, a pressure of from to 50 pounds per square inch may be employed in a still of the type illustrated. I

From the chamber 45 the oil travels down into and through the annular passage 49 into the cap-like extension 39, thence into and upward through the small innermost tube 53. In initially entering the top of the annular passage, the oil preferably has imparted to it a turbulent rotary path of travel by one or more curved.' vanes 1| (Fig. 5), each of which is Welded to the outer walls of the inner tube 5|, so that the oil may have contact with all sides of the tube 33. A number of these vanes may be employed, distributed lengthwise the tube 5|.

From the top of the innermost tube 53, the oil then passes through the curved connecting pipe 55 into the next tubular conduit of the series. Here, however, its path of travel is first downward through the innermost small tube 53 into the cap extension 39, and thence into and upward through the annular passage 49, between the outer tube 33 and the inner tube 5| Curved vanes similar to the vane 1| vmay be located in the annular passage 4'9 where the oil initially enters that passage from the tube 53.

At the top of this second conduit the oil passes into the chamber 45, and thence through the connection 41 into the space 45 of the next, and herein the third, tubular conduit of the series, where the path of the oil is substantially the same as in the case of the rst tubular conduit.

It will thus be seen that the travel of the oil through the annular passage 49 is reversed in the case of successive conduits and the counterow of the oil through the innermost tube 53 undergoes a similar reversal (as indicated by the arrows in Fig. l), the oil being transferred from the first conduit to the next succeeding conduit through the curved connecting pipe 55, from the second to the third through the pipe connection 41, and so on in alternation.

The oil in gaseous state is finally discharged from the last conduit of the still through the discharge pipe 13 and passes to a suitable fractionating tower, where the various fractions are cooled down to a liquefying temperature and separately withdrawn. Such tower may be of any common or usual construction and the specific character of the latter forms no part of the present invention.

In the operation of the still, the burner 21, which is subject to suitable control, conventionally indi- 'water gas.

cated .by the valve 15, is operated .under conditions to provide the high cracking temperaturesrequired. For example, the temperature of the products of combustion where they enter the first heating compartment of the still may be maintained at a range approximately of the order of from 2500" to 3000 F., and since the travel of the oil in successive conduits is counter to that of the products of combustion through successive heating compartments, this may be adjusted to maintain an approximately uniform temperature difference between the oil in any one conduit and the products of combustion in the surrounding heating chamber, with a, temperature maintained in the last heating chamber, for example, of the order of 1000 F.

In the cracking of petroleum oil to produce such fractions as toluol, xylol, benzol, and other like aromatic constituents, high temperatures well in excess of 1000 are necessary. While the oil travels rapidly under relatively high velocity through the relatively restricted annular passages presented by the series of tubular conduits, due to the effective heat transfer walls of the latter, there results a uniformly increasing absorption of heat by the oil so that before reaching the exit end of the still it may acquire cracking temperatures of the order of from 1000" to 1500" F. or more as required. i

The high velocity of the oil and the large effective heating capacity provided by the annular passage in the described form of still not only meet the conditions required for effective cracking of such constituents as toluol and the like, but the expedition with which the cracking is performed materially cuts down the formation of carbon within the oil passages. When and as such carbon is formed, however, the construction of the still lends itself to a simple method of removing the carbon without the necessity of dismantling the still or any of its component parts.

To effect this result the pressure of the oil as it leaves the still is indicated by a pressure gage 11. This indicated pressure has a definite relation to the pressure under which the oil is forced into the still so long as the oil passages through the tubular conduits are open and free from carbon. As soon as carbon forms, however, this condition is indicated by the drop in the pressure at the gage 11, or it may be indicated through a similar gage by a rise in pressure at the inlet end. When this occurs, or where it has proceeded to a stage indicating an interference with the cracking operation, the feed of oil to the still is cut off by the valve 19, and the oil valve 8| at the discharge end is also closed, cutting the still out of cracking operation.

The carbon is then removed by the formation of This is accomplished by forcing through the still, from any suitable source of'supply, water, or steam if the latter is available, and where water is referred to it will be understood as including water either in its liquid state or in its vapor state as steam. The water is forced into the still through the Valve-controlled pipe 83 tothe connecting pipe 41 of the rst tubular conduit. The operation of the furnace is at the same time continued to maintain temperatures in the successive heating compartments suiiicient to generate water gas through the action of the steam on the carbon. If water is introduced in liquid state it promptly becomes steam after entering the first tubular conduit. The steam passing through the successive conduits acts on the carbon in the passages thereof, with the formation near'the oil exit end thereof, where the temperature imparted to the oil is much higher.. The removal of the carbon by steam or water and the .formation of water gas require a temperatureof the .order of from approximately 1100 t0 1800 F.' With the furnace in full operation, and Where the steam or water is admitted as described through the supply pipe 83, this temperature is readily imparted to the steam by the time it has reached the tubular conduits .near the middle portion of the still or .at the oil exit end thereof, where the tendency to carbon formation is the greatest.

Under this condition, however7 the 'heat absorbed'by the steam in the first few tubular conduits near the oil inlet end of the still may not besuflicient to effect the formation of Water gas and the removal of the lighter deposits -of carbon in these conduits. In the practical application of this method of carbon removal, therefore, and to effect the complete removal of all carbon, it may be desirable, after forcing the steam from the pipe 83 through the still and discharging the resulting water gas through the pipe 85, to insure the removal of the lighter deposits'near the oil inlet lend ofl theV still by reversing the described process.

That is to' say, steam or water is thereafter additionally forced through the still from vthe oil outlet end to the oil inlet end thereof, using for that purpose the pipe 85 to introduce the steam into the still and the pipe 83 as a discharge pipe for the steam and the resulting Water gas. By that subsequent step, the steam, before reaching' the conduits near the oil inlet end of the still, has reached a temperature sulicient toinsure the removal of these lighter Ydeposits of carbon.

The gas producing apparatus described, while having useful application to the cracking of oil and the production of aromatic constituents thereof, may also be advantageously used in the production of other gases, such, for example, as Water gas.

While I have herein shown and described for purposes of illustration one specic embodiment of the invention, it is to be understood that various other applications of the invention may be made and that extensive deviations in the form and relative arrangement of parts may also be made, all without departing from the spirit of the invention.

Iclaim; Y

1.AIn a high temperature vapor-phase oil cracking still, the combination with a combustion chamber, of a heating chamber through which the products of combustion pass, said heating chamber having baie walls dividing the same into compartments through which said products of combustion pass successively, first in one direction and then in the opposite direction, a series of tubular conduits in successive compartments comprising each an outer tubular mem- -ber exposed to the heat thereof and having one end closed, an inner tubular member presenting saidconduit presenting also an annular passage surrounded by the walls of said heat exposed outer tubular member and itself surrounding and communicating adjacent its closed end with the passage of said inner Vtubular member andY presenting thereby anv outer counter-flow path for the travel of the oil in a direction opposite to that traveled in said inner passage and in a direction opposite to that of the travel of the products of combustion, the cross-sectional areas of theV annular and the inner passages being approximately the same, and communicating connections between said successive conduits at the-same Aadjacent ends thereof to cause travel of oil through the annular passage of onel conduit 'in one directionand through the annular passage ofthe next conduit in theopplosite direction, the ends of said conduits opposite' said communicating connections being free to Amove independently of `each other in response-to expansion-and contraction under heat.' i

2. In a gas generator, a` heatingchamber, a tubular conduit in `said Yheating chamber "and having a closed end,'the walls of said conduit being exposed -to `-the heatof said chamberfa'nd said conduit having an inner tubular member within said vfirst tubular member opening' into said conduit near the closed end thereof, and an intermediate tubular member between said inner member and said conduit member,vclosed to the travel of the gas therethrough but'positioned to leave an 'annularpassage of relatively small cross-section between the outer walls of said intermediate member and the inner walls of said tubular conduit member.

3. In a high temperature vapor-phase oil cracking still, the combination with a Vheating chamber, of a series of tubular conduits in said chamber, each conduit: presenting an Vannular passage for the travel of the oil surrounded by the heated walls of the tubular conduit, and presenting also an inner tubular passage providing a counter-flow path of travel for the oil within said annular passage, wall means intermediate the annular and the tubular passages of each conduit constructed and arranged substantially t0 equalize the flow velocity in said passages and communicating connections between successive conduits.

4. In a high temperature vapor-phase oil cracking still, the combination with a heating chamber, of a series of tubular conduits in said chamber, each conduit lpresenting an annular passage for the travel of the oil surrounded by the heated walls of the tubular conduit, and presenting also an inner tubular passage providing a counter-how path of travel for the oil within said annular passage, and communicating connections between successive conduits, said conduits including internal means whereby the cross sectional areas of their annular passages and of their inner tubular passages are made approximately the same and the flow velocities therein are substantially equalized while affording a relatively large circumferential external surface for the annular passages to provide a correspondingly high capacity for the transfer of heat to the oil in the annular passage.

5. In aV high temperature vapor-phase oil crackingstill, the combination with a combustion chamber, of a heating chamber, and a series of connected tubular conduits, veach comprising concentrically arranged tubes providing an outer annular passage for the travel of the oil, an inner communicating passageto provide a counterflow path of travel forthe oil inl the same conduit, and tubular wall means intermediate the annular and the inner passages of each conduit for promoting the iiow velocity in the annular passage thereof.

6. In a high temperature vapor-phase oil cracking still, the combination with a heating chamber, of a series of tubular conduit elements exposed to the heat in said chamber, said conduit elements each presenting an inner passage for one direction of oil travel therein, each conduit element also presenting an annular passage surrounding and connecting terminally with said inner passage and itself surrounded by the heat exposed wall of its conduit element, said annular passages providing for oil travel therein oppositely to the travel direction in the inner passages of the corresponding conduit elements, each conduit element having its annular passage connected to the annular passage of an adjacent conduit element and having its inner passage connected to the inner passage of another adjacent conduit element and tubular wall means intermediate the annular and the inner passages of each conduit for promoting the flow velocity in the annular passage thereof.

7. In a high temperature vapor-phase oil cracking still, in combination, a heating chamber, a tubular conduit in said chamber, said conduit being closed at one end and having its `outer Wall exposed to the heat of said chamber, said conduit having an inner tubular member opening into it near its closed end, and said conduit also having an intermediate tubular member disposed between said inner member and the heatexposed conduit Wall, said intermediate member being closed to the travel of the gas through it and being disposed to afford an annular passage of relatively small cross section between it and said heat-exposed Wall of the conduit.

8. In a gas generator, a heating chamber, a tubular conduit having a closed end and having its outer wall portion exposed to the heat of said chamber, said conduit comprising an outer tubular member presenting said heat-exposed wall, an inner tubular member opening into said outer member near the closed end of the conduit, and an intermediate tubular member between the inner and outer members, closed to the travel of the gas through it but positioned to afford an annular passage of relatively small cross section between it and the outer member.

HENRY BAETZ.

Images