US2733287A

US2733287A - Cracking of hydrocarbon gases and heater therefor

Info

Publication number: US2733287A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 o. c. scHAuBLl-z ETAL 2,733,287

cEAcxING oF HYDRocARBoN GAsEs AND HEATER THEEEEOE Filed sept. 2o, 1952 2 Sheets-Sheet l @OGG GOC)

OO OO GO GG OO @G @C G@ @G GO O O C O O G G O G @O O@ C@ C@ C@ O@ C@ @G C@ @ma GGO@ INVENTORS f z/: ATTO Jan. 31, 1956 o. c. scHAuBLE E-rAx. 2,733,287

CRACKING OF HYDROCARBON GASES AND HEATER THEREFOR Filed Sept. 20. 1952 2 Sheets-Sheet 2 INVENTORS Edward() l luik BY ,f /fr//W i/ ATTo 3.15'

CRACKING OF HYDROCARBON GASES AND HEATER THEREFOR Otto C. Schauble, Mount Kisco, and Edward H. Palclxik,

Hollis, N. Y., assignors to The Lummus Company,-

This inventionrrelates to improvements in the heating of gases to conversion temperatures and more particularly to the thermal cracking of lower hydrocarbon gases` such as methane, ethane and propane to obtain desired products such as ethylene and acetylene, for examples. It has been customary to employ for such cracking either heaters of the tube still type or those of the regenerative type. The former are quite expensive since they require the employment of expensive alloys in the tubes and their supports to withstand the high temperature required even for ethylene production. They are incapable of withstanding the higher temperature required for acetylene production so that a regenerativeV heater is employed for that purpose. An objection to'an otherwise suitable regenerative heater is that it is cyclic and not continuous in its operation; the charge to the heater must be interrupted periodically for reheating of the heating surface or mass.

An important object of the present invention is to provide for the continuous performance of the aforesaid type of cracking-with great economy in cost of heating apparatus and render possible the attainment of greatly increased temperature without damage to the apparatus and with acceleration of the reaction.

Otherimportant objects of the invention are to provide ar gas heater of improved design including a mass of refractory material having passages for continuously conducting there-through the charge to be converted and provision for directly and continuously tiring said mass in a mannerto effectively heat and convert the charge; to provide for controlling said firing in a manner to obtain a widerangeof heat curves-and adapt the heater for the conversion of diiferent charges and to different degrees to obtain desired end products; and to provide means cooperable with-'said mass to limit the conversion by quenching.

Further objects and ,advantages of the invention will appear from the following description taken in connection with the accompanying drawings.

In the drawings:

Fig. 1 is a verticle` longitudinal sectional view of the improved heater, the section being approximately on the linel-I of Fig. v2, with parts broken away and parts in elevation. f-

Fig. 2 isa vertical cross section on the line 2--2 of Fig. 3 is aihorizontal section on the line 3-3 of Fig. 2,' with most of the refractory appearingin plan.

t Fig. 4is a perspective viewi of one of the block components of the refractory mass.

.-According to the invention, the cracking operation is performed by a heater which-includes an elongated mass of refractorvmaterial constructed of stacked blocks or tiles. -The. massisformedv withnurnerous passages extending longitudinally thereof and. with numerous ilues The gas: charge Vis passed conously red by burners in respective alignment with the adjust the heat input with respect to the progress of the Provision is also madey charge through the passages. for passing the combustion gas from some of the ilues to others spaced along the course of the charge gas through the passages, for additional heat input. Certain of the ilues near the end of the course of the charge may be left unfired for quenching the conversion reaction, and air may be directed into said ilues for that purpose.

Referring to the drawings which show a preferred form of the heater, the refractory mass, designated M, is formed of a horizontal row of stacked blocks or tiles 1. One of these is shown in Fig. 4; itis of elongated rectangular shape and is formed witha central longitudinal flue 2 and with spaced transverse grooves 3 at its upper and lower faces. The block may, forexample, be 8 inches square in cross section and 3 -feet in length. The grooves 3 are omittedk from the top faces of the uppermost blocks of the stacks andfrom the bottom faces of the lowermost blocks of the stacks. The blocks are otherwise duplicates of on another and vthey give the mass M an elongated rectangular form. Each block has adjacent each end thereof a groove 4 extending entirely around it. The grooves 4 are lled with a suitable cement, as indicated at 5 inrFigs. 2 and 3, to seal all of the blocks together and prevent the escape of the charge gas at the opposite side faces of the mass M. The grooves 3 of abutting block faces together form passages for the charge gas.

These passages extend throughout the length of the mass and the tlues 2 extend throughout the width'of the mass and are tired to heat the charge, as will be explained hereinafter.

. The mass M is housed within a casing formed by a metal shell 6 lined with heat-insulating material 7 such as firebrick commonly employed in furnace walls. Actually, there will be courses of bricks but the heat insulation is shown as solid in order to simplify theillustration. The mass M rests upon the insulation at the bottom of the housing, andat thetop of the housing, the insulation is vpassed down upon the mass by two rows of screw clamps 8 borne by a pair of beams 9 secured to columns 10 at opposite ends of the housing. A pair of the clamps bear upon the insulating lining over each stack or tier of blocks and serve to press the lining down upon themargins of the ends of the mass-M, as shown in Fig. 3.

The columns 10 extend'beneath the housing toform short supportingv A structural steel frame 12';

legs for the heater unit. secured to said columns provides under support for the body of the heater. While the body of the heater is shown as vertical, it may be otherwise disposed.

The housing has an inlet 13 at one end to admit the gas.' charge to one end of the passages 3 and an outlet;14' at'itsff products from the oppoopposite end to conduct reaction site end of said passages. Said inlet and .outletare adapted to be connected to supply and discharge conduits, respectively. The interior of the housing is of substantially greater width than the width of the mass M and the latter is centered within the housing, to provide chanv nels .at opposite sides of the mass and extending the-full: length-and heighmhereof. As shewnin Fig-...23, passt partitions 15 -divide these channels into compartments'Il-' a 17,18, 19, 20'and 21 in alternation at' opposite sides`of` Compartment 21 has on exit flue. 22 fori oomff the mass. bustion gas.

Patented 'Jan.A 3 1, 1956 against the insulating re' Provision is made for tiring into the individual dues 2 of the refractory blocks 1. For that purpose, burners 23 are mounted in the side walls of the housing. These burners are disposed in alignment with the respective flues across: the aforesaid channel compartments. For delivery of `huid fuel to the burners, there are two manifolds 24 leading from a supply source, not shown. Air for sup porting combustion by the burners is delivered through two manifolds 25 connected to a source of compressed air, not shown. rIhe burners are distributed upon the opposite side walls ofthe housing and the fuel manifolds and.theireompanion air manifol'ds'serve the burners upon the opposite walls, respectively. For the burners on each of said walls there are fuel and air mixers 26, one for each verticall rowv of burners for firing a stack or tier of the blocks. A pipe 27 leads from the respective fuel manifold to each: mixer andl a pipe. 28 leads from the companion. air manifold to the'y mixer. These pipes have valves 29. A riser pipe 30 leads from each mixer and branch pipes 31 lead? therefrom to the individual burners ofA a vertical row of burners. The pipes 31 are provided with valves 32.

Thermostatic meansV are provided for indicating the temperature at different points along the mass M. At the top of the housing there is a row of thermocouplesv 33 each extending downward' through the insulating tirebrick and into contact with the topmost one of a stack of the blocks 1. They thermoc'oupl'esl are connected by wiring to a conventional type of device, not shown., for indicating the temperature. of each of the stacks of blocks along the massi.`

The oppositev side wallsof the furnace may, as shown, berformed: of panels P which may be removed or swung outward: to give access to internal parts for cleaning, repairing' or replacement thereof, and the fuel pipesI 30 are preferably formed of.l sections connectedv by releasable jointsl 3'4.- to permitl opening movement of the panels. Each panelextends for at least the full height of the refractory mass M and the total area of the panels; at each side of the heater is at least equal to the side area of the refractory mass so that the mass may be fully exposed at either side. If' desired, the panels may be provided' with peep holes, not shown, for internal inspection f the heater during operation;

In thel operation of the heater, the burners 23 areoperated', tn iire into theflues 2' of the blocks 1 or selected ones-of saidilues.v While the ame mayor may not enter the fines, depending upon the adjustment of the burners;

the combustion gas will be directly projected into theiues and. the expression4 re into is meant to apply both to entry of the flame, and'. to such projection of the combustion' gas. Refem'ng to Fig. 3, the combustion gas from thefburners at'the channel'A compartment` 16, after passing throughthe flues directly opposite said burners, enters the compartment 1f7f and: is carriedf by the flame or gas from Suhstantiallydncreas'es the heat' input overthe direct rin'g by the burners. From the compartment 21?r the combustion gas passes. out of the heater through the outletilue 22 which may leadrdirectlyv to a stack or to a waste heat recovery. means, not shown.

While the burners are operated, the gas charge to be conyertedis continuously conducted into the heater throughthe-inletvlV of the.: housing. Thencev the charge passes continuously through the,v numerous parallel pas# sagesV in. the;- refracto'ryf mass and. is' conyerted byfheat cQnducted fromfthef rediluesthrnugh the refractory mal' erialptothe passages?. The reactionproducts passoutLv Conduction of'A thel through the outlet 14. The heat input may be accurately adjusted to the particular charge employed and to the' degree of conversion thereof desired by selective adjust ment of the burners according to readings of the thermostatic indicator. The burners for firing the different stacks of blocks may be readily adjusted independently through adjustment of the fuel and air valves 29 to obtain any heat curve required. The reaction may also be quenched to limit the conversion by closing certain of the valves 29 to omit tiring of some of the stacks of blocks, such as the ones located near the exit. Additional quenching'A effect may be obtained, if required, by closing the fu'el valve 29 and opening the air valve in the pipe or line 28 to supply the respective burners with air to cool the Selected stacks of blocks.

The heater disclosed may be constructed at a cost small in comparison with the cost of a tube type heater and, with the employment of a suitable refractory material in the blocks or tiles of the mass M, it may be operated at a temperature exceeding 3,0009 F. without damage. Atl such temperature, cracking time is reduced so' that con'- version may be completed in a single passage of the charge through the refractory mass. Heaters of the regenerative type employing a refractory mass have been resorted to for exceedingly high temperature conversion which the tube type heaters are unable to withstand. Regenerative heaters are, however, not continuous in their conversion. operation;v said operation must be interrupted periodically to reheat the mass. The disclosed heater has the advantages of. continuous' conversion operation and improved control of heat input over a heater of the re-` generative type. The heater is also designed for' com venient. operation and. servicing, most of' the parts being no morev thanbreast' highV and internal. parts being acces'- sible. The charge passages: 3V may becleaned or decoked by a known method such as passing steam through them and operating' the burners to superheatthe steam.-

If considered desirable fora particular'heatingor cracking operation, the ow of the charge gas may be reversed,- passing in` at 14 and out at 13. The ow of4 charge gas and combustion gas willv then be generally concurrent.

While the advantageous employment of the' heater for the. cracking of hydrocarbon: gases has been described, its utilityV is'r not limited to such employment. It may beemployed to advantage for effecting synthesis reactions and for thev conversion of: charges other than hydrocarbon ones.

The present: disclosure of theinvention is merely illustrative and in nowise limiting and c'omprehends' such` modifications and adaptationsas will; come within"v the# scope of the followingy claims,

We claim:

l. The method of thermallyl cracking a hydrocarbon gas charge, comprising passing said charge alongisub'stam tially parallel. coursesl confined by refractory'materiaL-iring transversely' of'. said4 courses: appoints' spacedtherealong. into ues dened by said material and separated thereby from said courses, tiring transversely from the" opposite side of saidcoursesI at points: spaced' therea'lo'ng. into a second group offlues.l de'ned by said? material and' sepa'- rated thereby from said courses, passing the combustion gas of said firing from the exit end of one group of uesf to-thefiring endof the nextr adjacent flues' spaced along said course therefrom, conducting heat from saidflues through said-material torthe charge within' said'courses-, a'djusting said tiring; at said spaced points on each side ofy said courses independently to' obtainA the desiredy cracking effect, and injecting air into-a.- in'al group of llu'es spaced farther along said'y courseA than said tiring pointsia'ndf delined byV said materiali and separated thereby from said courses whereby-heatis conductedlaw'ay from said coursesin: thefvicinity of'sad finali' u'e's toquench'y the cracking reactionL iir said: courses;

2. Aheaterfbr a charge in a gaseous state, ccnnpfrisiirg'A a m'a'ss ofA refractory material formed'-` Witl substantially' parallel passages for said charge and with substantially parallel transversely spaced flues open at both ends and in heat-conducting relation to said charge passages, through the refractory material of said mass, a plurality of independently controlled burners opposed to one end of some of said ues and the other end of the remainder of said llues respectively and directed to fire thereinto, and conduit means for conducting combustion gas from the opposite end of some of said flues to the tired end of others of said llues.

3. A heater for a charge in a gaseous state, comprising a mass of refractory material formed with substantially parallel passages for said charge and substantially parallel ues open at both ends extending transversely of said passages and spaced therealong and therefrom in heatconducting relation to the passages, through the refractory material of the mass, burners opposed to one end of one portion of said flues and the other end of another portion of said ilues respectively and directed to fire thereinto, means to control combustion at said burners independently, conduit means to conduct combustion gas from the opposite end of some of said ilues to the fired end of others of the ilues, and means to inject air into a remaining portion of the ues to cool them while others are being tired to heat the charge.

4. A heater for a charge in a gaseous state, comprising a mass of refractory material formed with substantially parallel spaced passages for said charge and lues open at both ends extending transversely of said passages and in heat-conducting relation thereto through the refractory material, said ues being transversely spaced in rows arranged successively along said charge passages and the latter extending between the tubes of said rows, burners opposed to one end of a portion of the flues and the other end of a portion of said ues respectively and directed to re `thereinto, means to control combustion by said rows of burners independently, a heat insulating casing enclosing said refractory mass having an inlet for admission of the charge to one end of said passages and an outlet for discharge of the heated gaseous contents from the opposite end of the passages, the said casing having passages for conducting combustion gas from the opposite end of the ues of one portion of said rows to the red end of another portion of the tlues of said rows spaced along the charge passages, and outlet means for exit from said casing of combustion gas produced by the operation of the burners.

5. The heater of claim 4 including means for injecting air into a remaining portion of said ues to cool them while others are being fired to heat the charge.

References Cited inthe tile of this patent UNITED STATES PATENTS 1,351,801 Smallwood Sept. 7, 1920 1,404,721 Stein Jan. 24, 1922 1,430,630 Dempsey Oct. 3, 1922 1,431,486 Posnack Oct. 10, 1922 1,588,629 Smith June 15, 1926 1,657,704 Wescott Ian. 31, 1928 1,777,125 McDermott Sept. 30, 1930 1,958,200 Morton May 8, 1934 2,092,402 Morton et al. Sept. 7, 1937 2,188,133 Hepburn Jan. 23, 1940 2,430,344 Kemp Nov. 4, 1947 2,431,632 Brandt Nov. 25, 1947 2,574,738 Graham et al Nov. 13, 1951 2,678,339 Harris May 11, 1954 2,692,819 Hasche et al Oct. 26, 1954

Claims

1. THE METHOD OF THERMALLY CRACKING A HYDROCARBON GAS CHARGE, COMPRISING PASSING SAID CHARGE ALONG SUBSTANTIALLY PARALLEL COURSES CONFINED BY REFRACTORY MATERIAL, FIRING TRANSVERSELY OF SAID COURSES AT POINTS SPACED THEREALONG INTO FLUES DEFINED BY SAID MATERIAL AND SEPARATED THEREBY FROM SAID COURSES, FIRING TRANSVERSELY FROM THE OPPOSITE SIDE OF SAID COURSES, FIRING TRANSVERSELY FROM THE OPPOSITE SECOND GROUP OF FLUES DEFINED BY SAID MATERIAL AND SEPARATED THEREBY FROM SAID COURSES, PASSING THE COMBUSTION GAS OF SAID FIRING FROM THE EXIT END OF ONE GROUP OF FLUES TO THE FIRING END OF THE NEXT ADJACENT FLUES SPACED ALONG SAID COURSE THEREFROM, CONDUCTING HEAT FROM SAID FLUES THROUGH SAID MATERIAL TO THE CHARGE WITHIN SAID COURSES, ADJUSTING SAID FIRING AT SAID SPACED POINTS ON EACH SIDE OF SAID COURSES INDEPENDENTLY TO OBTAIN THE DESIRED CRACKING EFFECT, AND INJECTING AIR INTO A FINAL GROUP OF FLUES SPACED FARTHER ALONG SAID COURSE THAN SAID FIRING POINTS AND DEFINED BY SAID MATERIAL AND SEPARATED THEREBY FROM SAID COURSES WHEREBY HEAT IS CONDUCTED AWAY FROM SAID COURSES IN THE VINCINITY OF SAID FINAL FLUES TO QUENCH THE CRACKING REACTION IN SAID COURSES.

2. A HEATER FOR A CHARGE IN A GASEOUS STATE, COMPRISING A MASS OF REFRACTORY MATERIAL FORMED WITH SUBSTANTIALLY PARALLEL PASSAGES FOR SAID CHARGE AND WITH SUBSTANTIALLY PARALLEL TRANSVERSELY SPACED FLUES OPEN AT BOTH ENDS AND IN HEAT-CONDUCTING RELATION TO SAID CHARGE PASSAGES, THROUGH THE REFRACTORY MATERIAL OF SAID MASS, A PLURALITY OF INDEPENDENTLY CONTROLLED BURNERS OPPOSED TO ONE END OF SOME OF SAID FLUES AND THE OTHER END OF THE REMAINDER OF SAID FLUES RESPECTIVELY AND DIRECTED TO FIRE THEREINTO, AND CONDUIT MEANS FOR CONDUCTING COMBUSTION GAS FROM THE OPPOSITE END OF SOME OF SAID FLUES TO THE FIRED END OF OTHERS OF SAID FLUES.