US2442093A

US2442093A - Pyrolysis of fluid hydrocarbons

Info

Publication number: US2442093A
Application number: US600041A
Authority: US
Inventors: Milbourne Charles Gordon
Original assignee: United Gas Improvement Co
Current assignee: United Gas Improvement Co
Priority date: 1945-06-18
Filing date: 1945-06-18
Publication date: 1948-05-25
Anticipated expiration: 1965-05-25

Description

May 25, 1948- c. G. MILBOURNE 2,442,093

PYROLYSIS OF FLUID HYDROCARBONS Filed June 18, 1945 2 Sheets-Sheet 1 May 25, 1948. c. G. MILBOURNE 2,442,093

PYROLYSIS OF FLUID HYDROCARBONS Filed June 18, 1945 2 Sheets-Sheet 2 @a Kamm/bum.

resented May 2s, 4,194s

mowers or num mnocAnBoNs Charles Gordon Milbourne, Los Angeles, Calif.,

assignor to The United Gas Improvement Com.- l pany, a corporation of Pennsylvania' Application June is, 1945, serial No. 600,041

4 Claims.

The present invention relates to the manufacture of combustible gas by a cyclic process, which involves the pyrolysis of iluid hydrocarbon material, and in which heat is stored in a gas making path, during a heating period of the cycle, by the passage of hot combustion gases therethrough; and in which thestored heat is subsequently utilized for the pyrolysis of the fluid hydrocarbon material, by its passage through the heated path, during a gas making period of the cycle.

Typical of such cyclic processes for the manufacture of combustible gas' are the well known cyclic oil gas processes, carburetted Water gas processes, and hydrocarbon gas reforming processes.

Typical of the fluid hydrocarbon material pyrolyzed in such processes are crude petroleum oil and fractions thereof, such as naphtha, gas oil, fuel oils and residuums; natural gas; refinery oil gas; and sometimes tars derived from the pyrolysis of petroleum oil or coal. Some of'these materials contain non-hydrocarbon components in addition to their hydrocarbon constituents.

The invention, for convenience, will be described in connection with the employment of crude petroleum oil or a fraction thereof, which for convenience will be referred to generally as oil, although it is to be understood that the invention is applicable to the pyrolysis of other uid hydrocarbon material.

The invention, also for convenience, will be described in connection with the introductionof the oil to the cyclically heated gas making path in the liquid phase for vaporization therein, although it is to be understood that the invention is applicable to processes in which the oil is vaporized, for example in a continuous tube still. before its introduction into the cyclically heated path.

In the cyclic manufacture of oil gas, a gas set comprising a vessel or vessels, provided with a refractory lining or linings and with refractory checker brick, is heated during the heating period nf the cycle. termed the blow," by the combustion of fuel such as oil, tar or combustible gas, and by the passage of the resulting hot combustion products through the ves-sei or vessels, thereby raising the refractory lining or linings and checker brick to elevated temperatures and storing heat therein to provide a path of stored heat.

After the blow has been terminated, a run is made in which oil is sprayed into the gas set in the presence of a diluent gas, such for example as steam, and vaporized therein, the resulting oil vapors being passed along the path of stored heat with the steam and cracked therein by the stored heat to produce oil gas.

The cycle also includes steps for purging products of combustion to the atmosphere, and for purging oilgas to storage.

In the manufacture of carburetted water gas, an ignited bed of solid fuel, in a generator, is y blasted with air and raised to a highternperature. The resulting blast products are burned with secondary air, and their heat stored in the refractory lining and checker brick of a carburetting vessel or vessels, producing a path of stored heat. After the blast, termed the blow, a water gas run is made in which steam is passed through the highly heated fuel bed, generating blue water gas, which together with the excess steam is passed along the path of stored heat in the heated carburetting vessel or vessels, in which the blue water gas is carburetted with oil, which is sprayed into the set, vaporized, and the vapors cracked by the stored heat in the presence of the blue water gas.

Purging steps are performed in the cycle to purge blast products to the atmosphere, and to purge carburetted water gas to storage.

In normal cyclic oil gas and carburetted water gas practice, by far the larger part of the petroleum oil, which customarily comprises the less costly fractions of the crude such as gas oil and heavy residuums, iinds its way into fixed gas or in other words into gases which are liquefied with difficulty, such as hydrogen', methane, ethylene, and possibly other gaseous paraflines and olenes. Nevertheless a. certain portion of the oil is used up in the production of tar, drip oil and lower temperature condensates, the quantity of the later recovered depending upon the final temperature to which the gas is reduced before delivery to a gas holder for distribution.

The tar, drip oil and lower tempertaure condensates containv a wide variety of hydrocarbons, the number and quantity'of which vary with the final temperature to which the gas is subjected.

As an example hydrocarbons such as benzene, toluene, xylene, naphthalene, anthracene, indene, styrene, methyl styrene, cyclopentadiene, isoprene, piperylene, butadiene, etc., might be detected in small quantities or recovered in substantial amounts. All of these hydrocarbons are valuable, the unstaurated resinl forming compounds perhaps more so than the others, because under normal gas manufacturing conditions small quantities only are produced.

ljrom the standpoint of the manufacture of gas for distribution, "th'esecyclic processes have been' developed to a high degree of etllciency. However, from the standpoint of securing high yields of selected individual hydrocarbons',` while the employment of la cyclic operation of their general'character is highly desirable, the usual methods of operation are not so satisfactory.

In securing high yields -of many valuable in'dividual hydrocarbons from petroleum oil, a severity of pyrolysis is required which inevitably aeaaoea 4 time occupied by purges may also be disproportionate, or if it is not, an undue contamination of the make gas with combustion gases, or an undue loss of make gas to the atmosphere may take place.

The present invention is directed to the provision of a novel cyclic process of the above genresults in the production of a very considerable i eral character in the performance of `which a greater uniformity of pyrolysis may be' effected and greater yields of desired valuable hydrocarbons in good quality secured.

According to the present invention, during the f rst portion of the run, only a portion of the entire path of stored heat established during the venting its accumulation and providing a substantially carbon free path of pyrolysis at the i beginning of each gas making run.

In the usual methods oi operating these cyclic processes for the production of gas for distribuu tion, however, even should the required conditions for a high yield of' a given hydrocarbon of good quality be accidentally attained in a portion of the gas making path, and during a portion of the gas making run, oth'er portions of the gas making path and other portions of the gas making run may provide cracking conditions far removed from those which are desirable from the standpoint of production of the desired hydrocarbon material.

In the heating step of the cycle, in establishing temperature conditions approximating the desired temperature conditions in the downstream portion of th'e path of the heating gases suitable for effecting the desired pyrolysis therein, it is extremely difiicult to avoid setting up temperature conditions in the upstream portion of the heating path, which are entirely too severe for the desired pyrolysis.

During the gas making rum due to the fact that the stored heat in the path of pyrolysis is being continually abstracted in th'e vaporization of the oil and the pyrolysis of the resulting vapors with consequent cooling of the heat storage material, there is a continual shift, during the run. toward pyrolysis conditions of decreased severity I as the run proceeds, which is indicated by the swing, with respect to time, of observed temperatures at various points in the gas making path.

'I'he swing in pyrolysis conditions, throughout the gas making run, may be decreased by the employment of refractory heat storage material of relatively high heat conductivity as compared with that of the usual re clay brick, such for example as bricks of bonded silicon carbide or carborundum. Such refractory material has the capability of rapidly transferring heat from the outside surface to the interior during th'e blow, and from the interior to the outside surface of the brick, during the run, thereby maintaining more uniform surface temperatures.

Short cycles wit? short "runs also tend to lessen the swing in pyrolysis conditions attendant upon operations with any' given oil input rate. There is a practical limit to the shortening of cycle time, however, in that, with' continued shortening, valve operations begin to take up a disproportionate portion of the cycle- The blow is employed as the path of pyrolysis, and during the run the path of pyrolysis is shifted longitudinally within the path of stored h'eat in such manner that the succeeding portion of the run is conducted under pyrolysis conditions more closely approximating in pyrolyzlng effect those existing in the path of pyrolysis at the beginning of the run, than did those existing in the path of pyrolysis' immediately beforethe shift. y

Stated otherwise, during' the run after the pyrolysis conditions existing in the path of pyrolysis at the beginning 0f the run have been moderated due to the cooling action of the pyrolysis upon that portion of the path of stored heat employed as, the path 0f pyrolysis, the path of pyrolysis is shifted lengthwise within the path of stored heat, so as to alter the pyrolysis conditions in the direction of greater intensity of cracking and so as to approximate more closely the intensity of the cracking effected at the beginning of the run, whereby greater uniformity of cracking is attained.

The shift of the path of pyrolysis within the path of stored heat during the run may be made in a number of ways depending, among other things, upon the temperature conditions set up in the path of stored heat during the blowf upon the particular portion of the path of stored heat employed during the initial part of the run, and upon th'e degree of compensation in pyrolysis conditions to be effected by the shift of the path of pyrolysis.

The restoration of pyrolysis effect produced by the shift of the path of pyrolysis during the run may be obtained by shifting the path of pyrolysis so as to compensate for reduced temperature conditions by increased time of contact, or by shifting the path of `pyrolysis so as to operate during the succeeding portion of thev run with substantially the same temperature and time of Contact as at the start of the run, or even by shifting the path of pyrolysis so as to operate under more severe temperature conditions and with shorter time of contact, than those obtaining at the start of the run.

The shiftv in the path of pyrolysis within the path of stored heat may be conveniently made by shifting either the point of admission'of the oil to the path of stored heat, or the point of exit of the products of pyrolysis therefrom, or

Figure 6 is an elevation partly in section, illustrating, somewhat diagrammatically, an oil gas set adapted for employment in the process of the present invention.

The invention will be more particularly described in connection with the manufacture of oil gas, although it is applicable as before stated to other processes in which fluid hydrocarbon material is pyrolyzed.

Referring to Figures 1 to 5:

In all of the Figures 1 to 5, the path of stored heat established during the blow portion of the cycle is indicated by the shaded rectangle having an upstream end at I and a downstream end at 2.

In the operation diagrammatically illustrated in Figure 1, during the first part of the gas making run, oil is introduced to the path of stored heat at 3, which is downstream from I, while a diiuent gas such as steam is introduced at I, the products of pyrolysis and steam leaving the path of stored heat at 2.

During the later portion of the gas making run, and after the moderation of excessive temperatures in the stream portion of the path of stored heat by the cooling effect of the steam, the admission of the oil is shifted upstream to 4, the products of pyrolysis and steam ,still leaving the path of stored heat at 2.

It will be seen that the path of pyrolysis in the first portion of the run extended within the path of stored heat from 3 to 2. While in the second portion of the run the path of pyrolysis was shifted so that it extended from 4 to 2. The time of the shift and the degree of the shift and other conditions are chosen so that while the pyrolysis conditions existing in the longer path from 4 to 2 at the time of the shift are somewhat more severe than those existing at the time of the shift in the shorter path from 3 to 2, they closely approximate in effect the conditions of pyrolysis existing in the shorter path at the outset of the run A measure of the intensity of the crackin;f effected .in the several portions of the run may be obtained by a comparison of the density relative to air of the gas produced in the several portions of the run, as will bemore particularly described hereinafter.

In the operation diagrammatically illustrated in Figure 2, during the first portion of the run. the oil is introduced to the path of stored heat at 5, a diluent gas such as steam being introduced upstream at I. steam 'leave the path of stored heat during the rst portion of the run at 6 which is up stream from 2.

During the later portion of the run, with the oil and steam admissions unchanged, the point of removal of the products of pyrolysis and steam is shifted downstream to 2.

During the rst portion of the ,run, the path of pyrolysis extended within the path of stored heat from 5 to G, while during the latter portion of the run" it was shifted so as to extend from 5 to 2.

As in the previous operation. the time, degree and other conditions of the shift are chosen so that the pyrolyzing effect of the longer path of pyrolysis, while somewhat more severe than that of the shorter path of pyrolysis at the time of the shift, closely approximates the pyrolyzing effect of the shorter path at the outset of the lfrunl,

In the operation diagrammatically illustrated in Figure 3, during the first portion of the run,

The products of pyrolysis andl the oil is introduced downstream at 1, while a diluent gas such as steam is introduced at I. -jI'he resulting products of pyrolysis and steam leave the path of stored heat at 2. i

During the second portion of the run, after the upstream portion of the path of stored heat has been suiciently cooled by the passage of steam therethrough, the admission of the oil is shifted upstream to 9, and the point of removal of products of pyrolysis and steam shifted upstream to 8;

I n this case, the path of pyrolysis in the latter part of the run extending from 9 to 8 may be longer, shorter or the same length as the path of pyrolysis in the rst portion of the run extending from 1 to 2. In any case, other conditions such as temperature, rate of oil and steam admission, etc.. are such as to produce a pyrolyzing effect in the path of pyrolysis from 9 to 8 somewhat more severe than that existing in the path of pyrolysis from 'I to 2 at the time of the shift, but closely approximating pyrolyzing effect of the pyrolysis conditions in the path from 1 to 2 at the outset of the run.

In the operation diagrammatically illustrated in Figure 4, during the first portion of the run, oil is introduced to the path of stored heat at I0. while a diluent gas such as steam is introduced at I. 'I'he products of pyrolysis and steam leave the path of stored heat at II.

During a later portion of the run, oil is admitted to the path of stored heat at I2, which is upstream from I Il, and downstream from I, steam continuing to be admitted at I. During this portion of the run," the resulting products of pyrolysis and steam are taken off at 2, which is downstream from II.

As in the case of the previously described operations. the shift in the pyrolyzing path, during the run, is to compensate for moderation of pyrolyzing conditions during the earlier portion of the run" and to secure greater uniformity of cracking.

In Figure 5, the operation is similar to that of Figure 1 except that the upstream portion of the path of stored heat is divided by partition I3@ into two parallel portions I3 and I4.

During the rst portion of the run\oil is admitted to the path of stored heat downstream at I5, with steam supplied at I to either or both of the parallel portions I3 and I4, the resultingv pyrolysis products and steam being taken off at 2.

During a later portion of the run the oil admission at I5 is terminated and oil admitted at I6, which is upstream from I5 and downstream from I. Steam is admitted at I to both parallel portions of the path oi' stored heat I3 and I4, the steam admitted through portion I4 providing a diluting medium in the oil vaporization zone as well as carrying heat from the upstream end of the path of stored heat into the path of pyrolysis. The steam admitted through I3 carries heat from this portion of the path of stored heat into a downstream portion of the path of pyrolysis. bilpassing the upstream portion of the path of..

pyrolysis. Appropriate proportioning of the steam admitted through I3 and I4 provides a further control of the uniformity of cracking.

The resulting pyrolysis products and steam during the later portion of the run are taken 7 pyrolysis eiiected at the beginning of the "run is substantially restored, thereby securing increased uniformity.

In the operations diagrammaticaliy illustrated in Figures 1 to 5, steam may be admitted to the path of stored heat simultaneously with the oil, at the same point or points as the cil.

Also, if desired, the upstream admission of the oil to the path of stored heat, during the latter part of the run, in the operations of Figures 1, 3, 4 and 5 may be at I, the upstream end of the path of stored heat instead of somewhat downstream therefrom as shown in these figures, providing however that in such event the temperature conditions in the shifted path of pyrolysis are not excessive.

In the operations of Figures 1, 3, 4 and 5 the admission of the steam upstream at i, during the earlier portion of the "run" carries heat into the downstream fportion of the path of stored heat, which is then being employed as the path of pyrolysis, thereby reducing the swing in pyrolysis conditions therein, due to the cooling effect of the pyrolysis. Reference is made, in this connection, to Patent No. 2,372,197, dated March 2'1, 1945, to Edwin L. Hall.

In the operation of the present invention, as exemplied in the operations of Figures 1, 3, 4 and 5, this passage of steam may have the further function of moderating, during the earlier portion of the run, temperature conditions in the upstream portions oi' the path of stored heat in and adjacent to the zone of combustion, which are excessive from the standpoint of oil vaporization and pyrolysis, so that when the point of introduction of the oil is shifted upstream, the

temperature conditions in this upstream portion of the path of stored heat are no longer too severe for use as a. portion of the path of pyrolysis.

Referring to Figure 6:

' 2| generally indicates an oil gas generator provided With the refractory lining 22. In the generator chosen for illustration, there are provided three

refractory checkerbrick masses

24, 25, and 26 suitably supported on

arches

21, 28, and 29 respectively, and, together with the lining, forming the combustion space 30, and the oil vaporization spaces 3| and 32. Below checkerbrick 26, the generator is in communication by way of connection 33 with the superheater 34, provided with the refractory lining 35.

In the superheater chosen for illustration, there are provided two

checkerbrick masses

36 and 31, suitably supported by arches, one of which is shown at 38.

The superheater is further provided with the stack valve 40, and with the gas oft'take 4|, which lis provided with valve 42, and which leads to the wash box' 43. The superheater may be provided with the additional gas oitake 44, provided with valve 45, which leads from the space between

checkerbrick masses

36 and 31 to the oitake 4| and thence to the wash box. From the wash box, gas oiItake 46 leads to condensation, gas purification, and gas storage apparatus.

In an operation of Figure 6, chosen for illustration and similar to that diagrammaticaily illustrated in Figure l, during the blow, with stack valve 40 open and valve 42 closed (valve 45 is also closed, if connection 44 and valve 45 are provided), fluid fuel such as crude petroleum oil, fuel oil, residuum oil, tar or combustible gas is admitted to the combustion space 30, through V.fuel supply means 50, and burned with air supplied through air supply means I. The hot combustion gases traverse the combustion space 30, the checkerbrick 24, oil vaporizing space 3|, checkerbrickr 25, oil vaporizing space 32,' and checkerbrick 26. From the generator base, the hot combustion gases pass through connection 33 to the superheater 34, and through the superheater checkerbrick to the stack valve 4|), and thence to the atmosphere.

Duringthe blow the refractory linings and checkerbrick of the vessels are heated to a high temperature and heat stored therein.

The path of stored heat, so produced, extends from the combustion chamber 36, through checkerbrick 24, vaporization chamber 3|, checkerbrick 25, vaporlzation chamber 32, and checkerbrick 26 of the generator, and through the

checkerbrick masses

36 and 31 of the superheater, with the highest temperature conditions being established in combustion chamber 30 and checkerbrick 24 and lower temperature conditions in vaporization chamber 3|, checkerbrick 25, vaporization chamber 32, checkerbrick 26 and the

superheater checkerbrick

36 and 31.

When the desired temperature conditions for the oil vaporization and pyrolysis in the selected downstream portion of the path, that is, for illustration, in the generator below the arches 28 and in the superheater, have been set up, the heating is terminated byv shutting o the fuel supply through 50and the air supply through 5|.

A purge may now be made with steam supplied at 52, purging combustion products out through stack valve 40.

The stack valve 40 may then be closed, valve 42 opened (valve 45 remaining closed if provided), and the gas making run begun.

The admission of steam through steam supply 52 is continued, while simultaneously oil is sprayed into the vaporizing chamber 32, through oil supplyimeans 53. Additional steam may be simultaneously supplied, if desired, through steam supply means 54.

The oil is vaporized in the lowerfportion of the generator, in the presence ofthe steam, at least a part of which is heated in passing down through checkerbrick 24 and 25 into the vaporizing chamber 32. The steam and the resulting oil vapors pass through the generator checkerbrick 26 and the

superheater checkerbrick

36 and 31, in winch the desired pyrolysis of the oil hydrocarbons is eected.

The resulting oil gas passes through the gas offtake 4| to the

Wash box

4,3, and thence through oitake 46 to storage, condensing, purication, and fractionation apparatus (not shown) for the removal and separation of impurities and valuable constituents therefrom.

The washbox is illustrated as continuously supplied with water through connection 55, so as to maintain a body of sealing liquid, in the wash box, at a level suiiciently high to seal the end of connection 4|, and to prevent the return of gas to the set during the blow," but insuiciently high to prevent the ready passage of the oil gas to the ofltake 46 during the run.

The oil gas is cooled in the wash box, and a considerable quantity of tar containing valuable hydrocarbons is condensed therefrom. This tar is continuously removed with sealing water in the form of an emulsion, through connection 56,

As the gas passes through the gas offtake 46, it may be continuously sampled, the sampled gas passing through connection 51 to the scrubber-cooler 58. The scrubber-cooler 58 is illustrated as provided with the supply means 53 of a cooling and scrubbing liquid `such as water.

As the gas sample passes upward through the scrubber-cooler, it is scrubbed and cooled to remove entrained tar particles or other entrained material, and to cool the gas to a definite selected temperature indicated by thermometer 60. The removed entrained material and any condensate produced by the cooling leaves the scrubber with scrubbing and cooling liquid through connection 6I. Other means for removing entrained particles such as the use of packing with or without scrubbing might be employed.

The cleaned and cooled gas sample passes through connection 62 to the relative density register 63. The pressure of the gas may be controlled by valves to maintain a desired pressure approximating atmospheric and indicated by the manometer B4.

The gas passes through the relative density register 63, in which its density is compared with that of air, which is drawn in through connection 65, by way of the drier 66. The gas sample and the comparison air leave the register by way of connections 61 and 68 respectively. The relative density register may be arranged to continuously indicate and record the density with respect to air of the produced oil gas at chosen standard conditions of temperature and pressure, for example at 60 F. and slightly above atmospheric pressure.

An example of a type of relative density register which may be advantageously employed is that known commercially as Ranarex- The relative density of the gas, so determined, may be employed as a measure of the intensity of the pyrolysis effected in the several portions of the run.

As the gas making run proceeds, the temperature conditions in the vaporizing chamber 32 and in the checkerbrick 26 and the superheater are reduced due to the abstraction of heat for vaporization of the oil and for the cracking of the resulting vapors. This cooling is reduced in rate, however, by the passage into the vaporization chamber 32 of the steam admitted to the combustion chamber 30, through steam supply 52 and superheated in passage through the combustion chamber and the checkerbrick sections 24 and 25, while simultaneously cooling these upstream portions of the path of stored heat.

After a considerable portion of the gas making run has elapsed, for example after the expiration of 60, 10 or 80% thereof at the end of which' time pyrolysis conditions in the path of pyrolysis have been moderated somewhat due to cooling of that portion of the path of stored heat by the pyrolysis, and providing also that at the end of which time, the temperature conditions in the portion of the path of stored heat upstream from the point of oil admission have been sufficiently moderated by the passage of steam therethrough, the admission of oil through supply means 53 is terminated (steam supplied through 54 may also be shut oil) During the succeeding portion of the run the path of pyrolysis is extended upstream in the path of stored heat by supplying oil through oil supply means 'I0 to vaporization space 3|. Steam may be continued to be supplied to the combustion space 30 through steam supply 52 and additional steam may be supplied simultaneously to the vaporization space 3|, through steam supply means 1l.

The oil is vaporized and the resulting vapors cracked in passage through the vaporization space 3 l, checkerbrick 25, vaporization space 32, checkerbrick 26. and superheater checkerbrick 36 and 31, the resulting products of pyrolysis passing through oiftake 4I, to the wash box, the uncondensed gas passing through connection 46, as before. During its passage through connection 46, the gas may be sampled, scrubbed, cooled, and its relative density measured as before described.

A comparison of the relative density of the gas after the shift of the path of pyrolysis within the path of stored heat with the relative density of the gas produced at the outset of the run. furnishes a measure of how closely pyrolysisconditions in the shifted path of pyrolysis approximate those existing in the original path of pyrolysis at the outset of the run.

According to the present invention it is preferred to shift the path of pyrolysis during the run so that the change' in pyrolyzing conditions during the run does not produce a swing during the run of more than 0.03 in relative density of the oil gas when measured, at 60 F. and slightly above atmospheric pressure, by the method above described or by an equivalent method.

More preferably this swing in relative density docls not exceed 0.02 and still more preferably 0.0

Those skilled in the art will understand that care should be taken, in comparing relative densities of the oil gas produced in the several porytions of the runs, to avoid the inclusion of significant proportions of other gases such for example as unpurged combustion gases from the fb1ow, or correction should be made therefor in order to calculate the swing in relative density which is due to changes in conditions of oil pyrolysis.

At the end of the run the supply of oil to vaporization space 3| through oil supply means 'I0 is shut off, and the gas set is purged, for example, by continuing the admission of steam thereto through steam supply 52, purging the pyrolysis products out of the set through offtake 4 I The steam may then be shut oi and the cycle repeated.

It will be understood by those skilled in the art that the points of admission of oil and of steam in the respective portions of the rum 'as well as the durations of the respective portions of the run may -be so chosen that the pyrolyzing effect of the shifted path of pyrolysis, very closely approximates that of the original path of pyrolysis at the outset of the run.

Within a very considerable range of variation, the influence of changes in temperature upon cracking intensity may be closely compensated for by appropriate change in the length of the pyrolyzing path,

Under certain conditions, it may be possible to move the point of oil admission upstream in the path of stored heat, and simultaneously move upstream the point of exit of the pyrolysis products from the path of stored heat, maintaining the length of the path of pyrolysis substantially the same as before, providing temperature conditions in the shifted path are appropriate.

For example in the later portion of the run, the oil may be admitted to the vaporization space 3l, through supply 10. while with valves 40 and 42 closed and valve 45 open, the products of pyrolysis are taken off from the superheater through offtake 44, without passing through the downstream checkerbrick 31. In such case, the

. All upper portion of the superheater may be kept free of oil gas and purged by steam admitted at 12. This operation is in general similar to that diagrammatically illustrated in Figure 3.

During the later portion of the run. in either of the operations before described, if desired the oil may be admitted directly to the combustion space 30, providing temperature conditions therein and in checkerbrick 2l have been sufiiciently modied.

It will be obvious to those skilled in the art vthat the apparatus of Figure 6 may also be readilyy employed with whatever modication may 'be [Cycle length, 1.9 minutes] Per cent ci Operation cycle time Air and fuel admission to combustion zone. Soakin od.

g Steam to combustion zone (purge). Steam to combustion zone. Oil to downstream vaporizing zone.

2. Steam purge of downstream oil admission means.

6.5... Steam to combustion zone. Oil to upstream vaporization zone (combustion zone).

5.4- Steam to combustion zone (purge).

1.0 Expansion.

5.0. Air to combustion zone (air purge).

It will be seen that the total oil pyrolyzing time of the above cycle is less than 33 seconds, during approximately 78% of which, oil was admitted to the downstream vaporization zone. while the upstream vaporization zone was cooled by the passage of steam therethrough, and during the remaining 22% of which, the oil was admitted with steam to the upstream vaporizing zone, in this case the combustion zone. The products of pyrolysis were taken off from the superheater tcp in both portions of the pyrolyzing period, the operation being generally similar to one described in connection with Figure 1.

Of course, so short a cycle so highly subdivided is only practicable with eiiicient automatic valve operation.

The following temperatures were average observed temperatures through the cycle as measured by shielded iron-constanten thermocouples o F. Top of downstream vaporizing zone 1520 Middle of downstream vaporizing zone- 1495 Base of downstream vaporizing zone 1595 Base of superheater 1535 Top of superheater 1395 In general, in such operations, the high combustion temperatures of the combustion zone, at the end of the-blow," were reduced to observed temperatures (by optical pyrometer) of the order of 1700cl F. and lower, by the steam passing therethrough, during the ilrst portion of the run, prior to the introduction of oil to the combustion zone. It was found that greatly improved uniformity of pyrolysis could be secured under these conditions of operation with very materially increased set capacities as compared with operations in which the path of pyrolysis was not shifted within the path of stored heat, during the run. Increases in capacities of the order of 30% and more ma? be so obtained without sacrifice of yield and quality of desired unsaturated hydrocarbon products.

In the practice of the invention. it has been found that variations of observed temperature through the set and through the cycle may be very materially reduced. For example. the observed temperature swing, throughout a cycle of the above length, in F. (shielded iron-constantan thermocouple) at the middle of the downstream vaporizing zone may be only 30 F. or less:

at the bottom of the downstream vaporizing zone only 15 F.; in the lower superheater checkers only 14 F. or less; while in the middle of the superheater and in the top of the superheater. theoolnserved temperature swing may be reduced to In operations without the shift in the path of oil pyrolysis during the run, but otherwise comparable, these swings were very much greater resulting in much less uniform cracking. For example, swings in the observed temperature of the downstream vaporizing zone were frequently of the order of F. and more, even with a cycle of the above length and with the use of silicon carbide refractories. Likewise, the variation in temperature throughout the set is much less in the employment when the path of pyrolysis is shifted in accordance with the present invention.

In operations, in which neither the process of the above referred to patent to Edwin L. Hall nor the process of the present invention are employed. swings of observed temperatures of the order of 30o-400 F. in the oil vaporization zone have been frequently encountered, while without the use of refractory heat storage material of relatively high conductivity as compared to that of ordinary firebrick, still greater swings in observed temperature may occur, even though a. short cycle be employed.

The above temperatures are purely illustrative. Those skilled in the art will understand that the required intensity of pyrolysis varies widely depending upon the character of the :duid hydrocarbon material pyrolyzed and upon the particular hydrocarbon products desired.

For example. when unsaturated aromatic resinforming hydrocarbon material in good yields and in good quality and other aromatic hydrocarbon material in good quality is desired, there is a preference for relatively severe conditions of pyrolysis and for a naphthenie oil. such as a crude petroleum oil falling within classes 5 to 7 and particularly class 7, when classified by the method of Bureau of Mines Report of Investigations R. I. 3279, or a fraction of such an oil. On the other hand, when highest yields of aliphatic or alicyclic ,conjugated oleilnes are particularly desired. milder pyrolysis conditions and a more parafilnic oil may be chosen,

It will be further understood that in cyclic operations of the character described, for the same intensity of cracking, the observed temperatures in different portions of the apparatus and in different portions of the cycle, as well as calculated times of contact therein, may vary widely depending, among other things, upon the particular apparatus and cycle employed and upon the particular method of measuring temperature. Someof the influential variables are the character of the fuel and the method of combustion, the character, quantity and arrangement of the heat storage material, the character, subdivision, and rate of input of the hydrocarbon material pyrolyzed, the character and quantity of the diluent gas. whether or not the hydrocarbon material is vaporized as well as pyrolyzed by the stored heat, and the length and subdivision of the cycle.

In the operations particularly described in the foregoing, k'the path of pyrolysis was shifted within the path of stored heat but once during the run. Those skilled in the art will readily understand, that the path of pyrolysis may be so shifted a plurality of times, and that the manner of the shift need not be the same. For example the first shift of the. path of pyrolysis during the run" may be made by shifting the point of -removal of the products downstream in the path of stored heat, without changing the point of oil admission, While the next shift may be made by moving the point of oil admission upstream in the path of stored heat, without changing the point of removal of the products.

Other modifications of the process and of the apparatus illustrated will occur to those skilled in the art without departing from the spirit of the invention. For example, it may be preferred, especially when heavy oils" and residuums are employed, which yield particularly large quantitles of coke on vaporization, to further subdivide the gas set, so as to provide separate shells for the upstream and downstream vaporizing zones either or both of which may be devoid of checkerbrick below the point of oil admission thereto. If the vessels are of large diameter, a central refractory pier may be provided -in each otherwise empty vaporizing chamber.

The set may be further subdivided for other reasons, or on the other hand may be consolidated into a single shell.

Although it is preferred tc flow the fluid hydrocarbon material through the path of stored heat in the ,direction of the flow of the heating gases, as above described, the invention may be applied in cases in which these flows are in opposite directions to each other.

From the foregoing, it will be obvious to those skilled in the art that the invention may be readily applied to the manufacture of carburetted water gas. For example, during the first portion of the up run the carburetting oil may be admitted into the path of stored heat downstream from the top of the carburetter, during a later portion -of the up run the admission of the oil may be to the top of the carburetter, the carburetted water gas in each case being led from the set at the top of the superheater.

In comparing the relative densities of the carburetted water gas producedv during different portions of the run, it should be remembered that the composition of the blue water gas component ofthe carburetted water gas varies with the temperature of the fuel bed, and that this affects the density of the carburetted Water gas. Those skilled in the art will understand how to correct for varying blue water gas composition and will be able to employ the corrected relative gas density to control the uniform pyrolysis of the carburetting oil. i

yAs in the case of oil gas manufacture, significant quantities of combustion products from the blow should be excluded from the ycarburetted stood by those skilled in the art without the necessity of detailed explanation. v

In theforegoing, thek equalizationof pyrolysis conditions in the several portions of the pathof pyrolysis, which maybein part overlapping, and

in the several portions of the run" by equalizing the density, relative to a standard gas such as air, of the gas produced therein has been described.

The same method of equalizing pyrolysis conditions may be applied in the case of pyrolysis carried out in a plurality `of pyrolyzing paths arranged in parallel, such, for example, as a plurality of cyclically operatedv oil gas sets, the resulting pyrolysis products from which pass into a. common conduit or common relief holder.

For example in the case of a plurality of oil gas sets such, for example, as that shown in Fig. 6, and connected in parallel to the samerelief holder, the relative density, with respect to air, for example, of the make-gas passing from the wash` box of each oil gas set, may be continuously measured and recorded as previously de.

scribed, in connection with the description of the apparatus of Fig. 6, and the pyrolysis conditions within the individual sets adjusted in such manner that each of th sets produces oil gas of substantially the same desired relative density, within any desired degree of variation, tolerance, such for example, as that discussed in connection with the previously described equalization of pyrolysis conditions in different portions of the same set, during different portions of the run.

Those skilled in the art will know how to adjust the various factors which control variation in the intensity of pyrolysis as between individual gas sets, which is reflected in variations in the density of the make-gas' therefrom. Among water gases compared as to relative density, or

the determined relative densities should be corrected for the presence of such combustion p rodthe variables involved are the temperature conditionsset up in the heating period in the various portions -of the pyrolyzing path of the set, the time of contact during pyrolysis, and the effectiveness of contact between the material pyrolyzed and the heated surfaces in the gas set, the length and subdivision of the cycle, etc.

Assuming that other factors such as the disposition of heated surfaces and the character of heat conductive and heat storage refractory material are fixed, and that the rate of input, during the run, of fluid hydrocarbons and accompanying diluent gas is the same, the intensity of pyrolysis may be increased or decreased by elevating or reducing temperature conditions set up during the blow by increased or decreased rate of fuel combustion or by employing longer or shorter heating periods.

)With the same temperature and other conditions, the intensity of pyrolysis may be increased or decreased by increasing or decreasing the time of contact by reducing or increasing the rate of input of materials into the pyrolyzing path, such as, by decreasing or increasing the input of petroleum oil and steam to the generator.

It may be convenient to substantially fix all of the pyrolysis variables except one, for example, the rate of fuel combustion during a heating period of fixed length, and to control the intensity of pyrolysis, as measured by the relative density of the produced gas, by increasing the rate of heat input during the b1ow" period in response to increase in said relative density, and decreasing the rate of heat input 'during the blow period. in response to decrease in said relative density. y

However. control may be exercised by varying as by varying therate of input of the oil to be pyrolyzed, together with the accompanying steam, or other diluent gas. Control may also `be eficcted by yvarying more than one pyrolysis variable, if desired, l

The petroleum oil pyrolyzed may be introduced into the set in liquid or vapor form, as desired;

Other modications will readily occur to those skilled in the art and may be made without departing from the spirit of the invention.

This application is a continuation-in-part of my copending application Serial Number 564,540, filed November 21, 1944, whichas matured into Patent No. 2,393,333, dated January 22, 1946.

I claim:

1. A process for equalizing the intensity of pyrolysis eiected in a plurality of uid hydrocarbon pyrolyzing zones arranged in parallel flow relation one to another and discharging into a common gas storage zone comprising separately measuring the density of the gas produced in each of said zones during a. pyrolysis run, and in accommodation to the indications of such measurements separately adjusting the conditions of pyrolysis ineach of said zones including separately timed shifting of the pyrolysis path traversed by the said uid hydrocarbon in each of said zones during the pyrolysis run to produce gas in each of said zones of substantially the same density.

2. A process for equalizing the intensity of the pyrolysis cyclically effected in a plurality of petroleum oil pyrolyzing zones arranged in parallel flow relation one to another and discharging into a common gas storage zone, said pyrolyzing zones being heated by the passage of combustion gases other variables, as between sets, if desired, such f during the oil pyrolyzlng runs of the cycle to therethrough during heating periods of the cycle and between heating periods being employed for pyrolysis of fluid hydrocarbons by passage therethrough of said fluid hydrocarbons in contact with heat storage material arranged therein during a, pyrolysis run which comprises continuously and separately measuring under substantially the same conditions of temperature and pressure and after substantially the same degree of condensation, the gas produced during said pyrolyzing runs in each of said pyrolyzing zones, and in accommodation to the indications of such measurements separately adjusting pyrolysis conditions in said zones including separately timed shifting of the pyrolysis path traversed by the said petroleum oil in each of said zones during the pyrolysis run to cause the production of gas in each of said zones of substantially the same density when so measured.

' 3. A method for controlling the uniformity of products of pyrolysis produced in a plurality of cyclically operated oil gas sets connected ln parallel to the same relief holder, the cycle comprising a heating period in which heat is stored in refractory heat storage material by the passage in contact therewith of hot combustion gases and an oil pyrolyzing run in which petroleum oil is substantially the same temperature under substantially the same pressure conditions, `separately measuring the density of the gas in each stream so cooled under substantially the same conditions of temperature and pressure, and in accommodation to the indications of such measurements separately adjusting the rate of heat input to the several gas sets during the heating periods of the cycle in such manner that the density of the oil gas flowing from each set when so measured is substantially the same and with separate timing in the two se,ts shifting the pyrolysis path traversed by the said petroleum oil in each of the two sets during the pyrolysis run. 4. A method for controlling the uniformity of products of pyrolysis produced in a plurality of cyclically operated oil gas sets connected in parallel to the same relief holder, the "cycle comprising a heating period in which heat is stored in reiractory heat storage material by the passage in contact therewith of hot combustion gases and an oil pyrolyzing period in which petroleum oil is pyrolyzed by the stored heat invapor phase and in the presence of steam, said oil gas sets each operating in a, cycle of substantially the same length and subdivision, which comprises separately cooling the oil gas ilowing from each set during the oil pyrolyzing periods of the cycle to substantially the same temperature under substantially the same pressure conditions, separately measuring the density of the gas in each stream so cooled under substantially the saine conditions of temperature and pressure, and in accommodation to the indications of such measurements separately adjusting the rate of petroleum oil input to the several sets during the pyrolyzing periods of the cycle and separately shifting the pyrolysis path traversed by the said petroleum oil in each of the sets during the pyrolysis periods of the cycle in such manner that the density of the voil gas owing from each set when so measured is substantially the same.

CHARLES GORDON MILBOURNE.

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

UNITED STATES PATENTS Rude oct. s, 1940