US2580767A

US2580767A - Process for manufacturing oil gas

Info

Publication number: US2580767A
Application number: US52284A
Authority: US
Inventors: Edwin L Hall
Original assignee: American Gas Association Inc
Current assignee: American Gas Association Inc
Priority date: 1948-10-01
Filing date: 1948-10-01
Publication date: 1952-01-01
Anticipated expiration: 1969-01-01

Description

Jan. 1, 1952 E. L. HALL PROCESS FOR MANUFACTURING OIL GAS Filed Oct. 1, 1948 TO WASH BOX 2 SHEETS-SHEET 1 l7 TO STACK TO STACK l6 T I STEAM 3 (FIXING ZONE) ,I2 (FIXING ZONE) H [2 UNIT II HEATING STER GAs MAKING UNITS 5 (coMGusTIgg /APo IzING) UNIT Io IDLE. (,?A FJ ,YQ') -4-FLUID FUEL STEAM GAS TO WASH BOX I |3 |2 l0 ll k UNIT II GAs MAKING STEP v |5 I4 GAS MAKING OIL SUPERHEATED STEAM TO STACK ll2 UNIT Io HEATING srse l4 FLUID F-UEL- TAIR GAS TO STEAM *WASH BOX si um Io GAs MAKING STEP IO\ /H GAS MAKING OIL l4 5 SUPERHEATED STEAM INVENTOR EDWIN L. HA I I FIGJ BY H IS ATTORNEYS any Jan. 1, 1952 PROCESS FOR MANUFACTURING OIL GAS Filed Oct. 1, 1948 E. L. HALL ATO WAS H BOX UNIT 2| HEATING STEP.

2 SHEETS-SHEET 2 STACK 2 3 (FIXING ZONE) 4 COMBUSTION 1 ggm c-"| u|t FUEL HOT GASES STEAM us To WASH BOX 2% 20 22 pm'r 2| GAS MAKlNG STEP 2l 25 24 05s MAKING on.

SUPERHEATED STEAM T0 STACK AIR UNIT 20 HEATING STEP 2;

/2 25 FLUID FuEL HOT GASES GAS T0 STEAIM d] *WASH BOX l 2- 23 UNIT 20 GAS MAKING 20 22 STEP 2| GAS MAKING bu. 25

SUPERHEATED STEAM INVENTOR EDWIN L. HALL BY HIS ATTORNEYS FIG. 2 W4- Patented Jan. 1, 1952 PROCESS FOR MANUFACTURING OIL GAS- Edwin L. Hall, Cleveland Heights, Ohio, assignor to American Gas Association, Incorporated, New York, N. Y., a corporation of New York Application October 1, 1948, Serial No. 52,284

6 Claims. 1

The present invention relates to a novel process for the manufacture of oil gas, and more particularly it relates to an improved process for the manufacture of oil gas by the pyrolysis of petroleum oils in a regenerative-heating operation.

Oil gas has been manufactured for many years by procedures in which petroleum oil is vaporized and pyrolyzed; in the presence of a gaseous diluent such as steam, in zones of stored heat. A zone, or zones, is first heated by burning a fuel and passing the hot products of combustion of the burning fuel therethrough, and, when the zones are sufliciently heated, oil is then vaporized and, in the presence of a gaseous diluent, pyrolyzed into fixed gases by abstracting heat stored in the zone. After a gas making run. the zone is again heated, followed by another gas making run, and so on. This method of heating is referred to as cyclic heating as contrasted, for example, to the vaporization of oil in a still where "heat is applied continuously to the oil directly from the heat source. In order to pyrolyze the vaporized oil properly not only must the vaporized oil be cracked into molecular fragments, but the cracked materials must be held in a heated zone for a suflicient time for the gaseous system to reach equilibrium during which time the highly reactive molecular fragments become converted into stable molecules of gaseous compounds. To bring this conversion about, the

cracked vaporized oil is swept from the initial vaporizing and cracking zone, which is at a relatively high temperature, through a path of stored heat, or fixing zone. The temperatures in the fixing zone must be controlled so that the average temperature thereof is relatively low as compared to that of the combustion-vaporizing zone where vaporization and initial cracking of the 011 takes place, with the highest temperature adjacent the combustion-vaporizing zone and with the temperatures progressively decreasing toward the exit end. By the time the vapors have reached the relatively cooler exit end of this zone. the gas has been fixed and it may then be cooled with the removal of condensable constituents.

In the present commercial process, for instance. there is provided a combustion-vaporizing zone, which is often merely the carburetor-generator cell of a carbureted water gas system; and a path of stored heat, or fixing zone, which is often the "superheater of the carbureted water gas system. The combustion-vaporizing zone is merely a chamber providing a space, surrounded by high temperature-resisting walls of heat-conducting material, wherein fuel, such as tar. gas or oil, and air are forced in the proper ratio for combustion, and burned. The hot products of combustion heat the walls of the chamber, and are swept through the superheater where heat is stored in a checkerwork of ceramic material. and thence out the stack. This step is referred to as the "blow. Then oil and steam are admitted to the combustion-vaporizing zone where the oil is vaporized and cracked, and the mixture is swept through the hot checkerwork where itis fixed into permanent gas, and thence to the wash box. As indicated above, the step is referred to as the gas making run or simply as the make." These steps are repeated continuously as long as required for the gas-making operation. Generally, the apparatus is purged" with air or steam between the blow and the make, or between the "make and the blow, or both, to remove undesirable products, to recover the gas remaining in the system and to prevent the accumulation of explosive mixtures. There are various modifications of the commercial process as outlined above, all of which, however, are based on the same sequence of steps.

-There are limitations imposed by the above set forth procedure which are becoming presently more serious. As indicated previously, the opti mum conditions throughout the system embody a combustion-vaporizing zone of relatively high temperature, followed by a fixing zone of relatively low average temperature as compared to that of the combustion-vaporizing zone and in which the temperature progressively decreases toward the exit end. These conditions are met in present day processes only with difiiculty since the temperature throughout the system depends for the most part upon the combustion of oil during the blow," and a rate of combustion adapted to provide a relatively high temperature in the combustion-vaporizing zone similarly results in undesirably high temperatures in the subsequent path. In other. words, the top temperature limit in the combustion-vaporizmg zone is restricted in order to provide the necessary temperature conditions in the fixing zone. As a result, the temperature in the combustion-vaporizing zone cannot be maintained. as high as desirable on the one hand, and the temperature of the fixing zone cannot be maintained as low as desired on the other, and thus a relatively wide temperature gradient between the combustionvaporizing zone and the exit end of the fixing zone, which would represent the optimum conditions, cannot be obtained economically in present day procedures. This is further aggravated by the fact that the steam admitted into the combustion-vaporizing zone during the gas making run has a cooling effect on that portion of the apparatus which it is desired to have at the highest temperature.

Moreover, the present commercial processes can only satisfactorily utilize low residual carbon oils in the gas-making run. For instance, oils containing over 67% free carbon, as determined by the Conradson test more fully described hereinafter, cannot be-employed successfully in the gas-making run because of the fact that the carbon deposited on the checkerwork in that portion of the fixing zone which is adjacent the combustion-vaporizing zone, will in time clog the system. It has thus been necessary toemploy only the low residual carbon oils which are relatively expensive as compared to the more abundant oils containing higher quantities of Conradson carbon, or high residuum oils. A method of manufacturing oil gas wherein high carbon oils may be utilized as the gas-making oil is becoming increasingly desirable with the advent and increasing use of catalytic and thermal cracking techniques in the petroleum refining industry which result in more highly cracked residuum oils which produce much higher ratios of carbon upon gasification. The economics of the gas industry require the successful use'of the cheapest residual oils that the petroleum industry provides. Furthermore, even the carbon deposited in the checkerwork during present commercial oil gas operations represents a waste since it cannot be utilized in the system but must be removed by periodic cleaning or by intermittent blasts of air or steam.

will be apparent from a consideration of the following specification and claims.

In accordance with the present invention, there is provided a continuous regenerative process for the manufacture of oil gas by the pyrolysis of petroleum oils in which heat is stored in two independently heated interconnected paths of stored heat, each of which is preceded by a combustion-vaporizing zone in flow communication therewith, which comprises admitting fiuid fuel and air into the combustion-vaporizing zone preceding one of said paths; burning said fuel in said combustion-vaporizing zone. the products of said burning being swept along said path to store heat therein, abstracting a portion of said heat from the other of said paths of stored heat by passing, in the direction of its communicating combustion vaporizing zone,

steam therethrough to superheat said steam; admitting said superheated steam to the first mentioned combustion-vaporizing zone concurrently with the admission of petroleum oil thereto; va-

- porizing and pyrolyzing said petroleum oil in the All these mentioned limitations, of course,

combine to seriously limit the capacity of the apparatus during the gas-making run. That is to say, since the temperature of the combustionvaporizing zone, on the one hand, cannot be tained as low as desired, less efilcient gasification is obtained during the gas-making run due to overcracking. Furthermore, since carbon deposited, is removed by unduly long blow periods, further inefiiciency is encountered. Thus, there is room for improvement in the presently practiced procedures with the aim of overcoming the limitations set forth above.

' It is, therefore, a principal object of the present invention to provide an economical process for the manufacture of oil gas whereby the aforementioned disadvantages are for the most part overcome or eliminated.

Another object is to provide a process for the manufacturer of oil gas wherein there is readily established between the combustion-vaporizing zone and the fixing zone, temperature gradients favorable to the production of the maximum quantity of high heat unit gas per unit of gasmaking oil employed.

Another object is to provide a process whereby steam employed in the gas-making run may be preheated to a high temperature prior to the admission to the combustion-vaporizing zone of a gas-making unit while at the same time insuring optimum temperature gradients during the process.

A specific object is to provide a process fo the manufacture of oil gas whereby heavy residuum and high Conradson carbon oils may be readily employed as gas-making oils.

A specific object is to provide a process for the manufacture of oil gas whereby greater efil'ciency is obtained by the utilization of the carbon deposited in the system during preceding gas-making runs as a part of the fuel required in the subsequent storage of heat in the system.

A further object is to provide a process for the manufacture of oil gas whereby heat losses due to the loss of sensible heat in the made gas is kept at a minimum.

Further objects, including the provision of a.

presence of said steam in said first mentioned combustion-vaporizing zone and in said first mentioned path; withdrawing said vaporized and pyrolyzed oil and said steam from said first mentioned path; and repeating said sequence of steps with a reversal of the order of said two paths of stored heat.

It will be noted from the above that in accordance with the broader aspects of the present process there are provided a pair of gas-making units, each unit comprising, in fiow communication, a combustion-vaporizing zone and a gas-fixing zone. The sequence of steps that occur, 1. e. blow and gas-making run" in each unit are roughly the same as that occurring in present day procedures, with the exception that steam introduced into the combustion-vaporizing zone of one of the units during the gasmaking run is previously preheated to a high temperature by passing it through the fixing zone and combustion-vaporizing zone of the other unit from the exit end of the former in the direction of the latter. This exception, however, provides many unexpected advantages as well as fulfilling a part of the objects outlined above. In the first place, by passing steam through one unit in the direction stated preparatory to its admission to the other for its gas-making step, a wider temperature gradient is provided in the first unit preparing it for its subsequent heating and gas-making runs. In other words, the temperature of the fixing zone of the first unit is materially reduced from a point adjacent to its communicating combustion-vaporizing zone outwardly towards its exit end so that during its subsequent blow or heating step greater combustion can be had in its communicating combustion-vaporizing zone with consequent higher temperatures therein, while still maintaining a relatively low mean temperature in the fixing zone, with the temperatures in the fixing zone progressively decreasing toward the exit end. In the second place, while performing this valuable function, the steam also becomes heated to a high temperature obviating the use of auxiliary steam-heaters.

This also eliminates the cooling effect encountered in prior procedures when the heat in the combustion-vaporizing zone was relied upon to superheat the steam.

Preferably. however, heat is also abstracted from the fixing zone of one unit by passing air a therethrough from the exit end thereof in the direction of and through its communicatingcombustion-vaporizing zone. The hot gases thus leaving that combustion-vaporizing zone are admitted to the combustion-vaporizing zone preceding the other path concurrently with the admission of a fluid fuel thereto during the blow" or heating step. This feature, along with the superheating of the steam during the gas-making run as above described, combine to form a particularly valuable commercial process. Thus, in accordance with the preferred process of the present invention, a portion of the stored heat from one of said independently heated, interconnected paths of stored heat is abstracted by passing air therethrough in the direction of its communicating combustion-vaporizing zone to raise the temperature of the air and to burn carbon in said path and its communicating combustion-vaporizing zone. The resulting hot gases are then admitted to the combustion-vaporizing zone preceding the other of said paths concurrently with the addition of fluid fuel thereto. The fuel is burned in the presence of said hot gases in said combustionvaporizing zone, the products of said burning being swept through the path communicating therewith to store heat therein. A further portion of stored heat is then abstracted from the first mentioned path of stored heat by passing steam therethrough in the direction of, and through, its communicating combustion-vaporizing zone to superheat the steam, and the superheated steam is admitted to said combustion-vaporizing zone preceding said second mentioned path concurrently with the addition of petroleum oil thereto. The petroleum oil is vaporized and pyrolyzed in the presence of said superheated steam in the said combustion-vaporizing zone and in the said second mentioned path of stored heat, and the vaporized and pyrolyzed oil and steam are withdrawn from said path. The cycle is completed by repeating the above sequence of steps with a reversal of the order of said two paths of stored heat. A gas-making process of the same general type in which air is passed countercurrently through one unit preparatory to its admission to the other as described, but in which steam, if used, is not preheated in the manner described above, forms the subject matter of copending application, Serial Number 52,283, filed October 1, 1948.

Thus, in accordance with the preferred embodiment as outlined above, the passage of the air and the steam through one unit in the direction stated preparatory to their admission to the other unit during the respective blow and gas-making" steps results in a greater temperature gradient between the combustion-vaporizing zone and fixing zone of each unit than is the case when only steam is preheated in the manner described preparatory to the gas-making runs. Of equal importance, however, is the fact that the air passing through one unit in the direction stated becomes progressively hotter as it approaches the point in the apparatus where carbon deposited from the preceding asmaking run is heaviest. The hot air causes combustion of carbon in this unit not only removing it but further raising the temperature, of the resulting gaseous mixture to a high degree just prior to its admission into the combustionvaporizing zone of the other unit. This not only eliminates cooling, due to the admission of cool air into the combustion-vaporizing zone of the other unit, but also provides more efllcient coinbustion of the oil therein. Furthermore, since the hot mixture of gases entering the combustion-vaporizing zone contains a relatively large amount of sensible heat, both due to the abstraction of heat from the first unit and due to the combustion of carbon deposited therein, a correspondingly less amount of fuel is required for the blow," or heating step, in the second unit. The reduction in the amount of fuel required increases with the amount of carbon deposited by the gas-making oil which is in turn burned during the passage in the manner described of the air through the unit containing the deposited carbon. Thus in accordance with the preferred embodiment not only can less expensive oil be employed in the gas-making run, but the cheaper the grade employed, i. e. the higher the quantity of carbon it deposits during cracking, the smaller the quantity of fuel required.

It will be also noted from the above that the high temperatures are concentrated in that portion of each unit where they are most necessary, i. e. in the combustion-vaporizing zones, and that portion of the fixing zone immediately adjacent each combustion-vaporizing zone; while lower temperatures are provided where they are most desirable, i. e. in the fixing zone with temperatures progressively decreasing toward the exit end thereof. The net result of this is that more efficient combustion of fuel is obtained in each combustion-vaporizin zone during the particular "blow or heating step of that unit, and more efficient gasification with less over-cracking is obtained in each unit during its particular gasmaking run.

The present invention may be more readily understood by a consideration of the drawings in which Figure 1 illustrates the main steps of a complete cycle of the present process, and Figure 2 illustrates the main steps of a complete cycle of the preferred embodiment of the invention.

Referring more particularly to the drawings, Figure l, as stated, illustrates the main steps of the invention. There are shown in Figure 1 two oil-gas-making units Ill and il each of which is provided with a combustion-vaporizing zone l4 and i5, respectively, and a path of stored heat, 1. e. fixing zone, I! and 13, respectively. While, for the sake of description, distinct combustion-vaporizing zones and distinct fixing zones 4 are shown in the drawings. it will be understood that often, in actual practice, no clear boundary line between the combustion-vaporizing zone and its communicating fixing zone can be fixed. As seen in 1 which illustrates the heating step for unit ii, there are means for selectively introducing steam into the exit end of each unit. One method of doing this is shown in 1 wherein conduits leading to the exit ends of each unit it and II are connected to a common source of steam by means of two way valve II. By this arrangement steam may be directed to either of the units as desired or turned 01f completely. The succeeding steps shown in drawings, 1, 1 and 1 which illustrate the gas-making step in unit I I, the heating step for unit l0, and the gasmaking step in unit Ill, respectively, show the directions of flow of the steam, or, if no flow direction is shown, the fact that no steam is flowing in that step. Similarly 1 shows means for selectively withdrawing the materials from the respective units. One method of doing this is shown in 1 by providing appropriate conduits leading from the exit end of each unit II and II to a conventional two-way valve I, so that the gas coming from the respective units may be directed to the wash box as required. in 1- conventional conduits leading to a stock are also provided. In this case also, the succeeding steps as seen in 1 1 and 1 show the direction of flow from the respective units. There are, of course, conduit means interconnecting both combustion-vaporizing zones, and in 1 and 1* the direction of now through these means during the various steps is indicated. Since, for the purposes of the broader aspects of the present invention as illustrated in Figure 1 gas-making unit ll may be idle during unit is heating step as shown in 1, the representation of unit' il in l has been omitted.

While each gas-making unit is illustrated in the figure as a unitary structure, it will be understood that the combustion-vaporizing zone of each may be a separate structure or cell, such as a conventional generator-carburetor unit of the type used in present day oil-gas, or carbureted water-gas industries, each of which is in fiow communication with a separate fixing zone such as a conventional superheater of the type employed in present day oil-gas or carbureted watergas industries. Since the figure illustrates the main steps of a complete cycle, it is understood that the system has already been heated to start the process, as is conventional, by burning fluid fuel such as oil, tar or gas in each combustionvaporizin zone and blasting the hot combustion gases through the respective fixing zones. Units in and ii may be connected to a common stack or, as is preferred, to separate stacks in order to avoid hct" valves, and may be connected either to a common wash box, or to separate wash boxes. Although combustion-vaporizing zones l4 and 15 have been, for the purpose of description, illustrated ,as separate structure, it will be understood that, since the conduit means interconnectin them is large so as to handle the hot gases, combustion-vaporizing zones i4 and I5 and the interconnecting conduit means may be developed in practice into a single chamber.

As shown in l of Figure l, the cycle may be started, after each unit has been heated to the extent desired for starting the process as is well known in theart, by admitting air and a fluid fuel to the combustion-vaporizing zone of one of the units, in this case, combustion-vaporizing zone l5 of unit Ii. The fuel is burned in combustion-vaporizing zone [5 and the hot combustion-products are swept through the fixing zone is, and thence out the stack.

The next main step is shown in 1 where steam is passed through unit Ill from the exit end thereof through fixing zone I! and combustion-vaporizing zone I4, respectively. As the steam passes through unit l0 it abstracts heat from fixing zone [2 which has been stored therein by a previous blow" step. As the steam approaches combustion-vaporizing zone ll it becomes progressively hotter. However, due to its initial cooling effect upon its admission to the exit end of unit ill. the temperature throughout unit progressively decreases from the combustion-vaporizin zone It outwardly toward the exit end. The passage of steam in the direction stated thustends to concentrate high temperatures where they are required, i. e. in combustion-vaporizing zone I4 and in that portion of the fixing zone I2 which is adjacent to the combustion-vaporizing zone u. while at the same time providing a relatively As shown widetemperature gradient between the combustion-vaporizing zone H and the exit end of the fixing zone ii. The highly superheated steam leaving unit It is then admitted to combustionvaporizlng zone I! of unit ll, substantially concurrently with the admission of gas-making oil thereto, In combustion-vaporizing zone II the oil is vaporized, and substantial cracking of the vaporized 011 takes place. Because of the large amount of sensible heat contained in the superheated steam, the steam serves' as a heating medium for the vaporized oil and also as heat transfer medium between the hot surfaces in unit II and the vaporized oil. It will also be realized that gas-making oil may be admitted to combustion-vaporizing zone i4 while the steam is passing therethrough, in which case it is also admitted to combustion-vaporizing zone I! concurrently with the superheated steam.

The thus vaporized and pyrolyzed oil and the steam are then passed through fixing zone II where the more reactive molecular fragments of cracked gas become converted to stable gaseous molecules. However, since steam has previously been passed through unit il in the same manner as in unit ID as above-described, a wider temperature gradient is provided in the same manner as was described above with respect to unit l0. Thus the average temperature in fixing zone I3 is lower than that in conventional fixing zones facilitating the fixing" of the gas therein and decreasing to a marked extent the danger of over-cracking. The fixed gas and steam leaving fixing zone 13 from the exit end thereof and directed to a wash box.

1 and 1 illustrate the completion of the cycle by a repetition of the above steps with, however, a reversal in the order of units. As shown in 1 air and a fluid fuel are admitted to combustionvaporizing zone [4 of unit ill. As in 1 the fuel is burned and the hot combustion products are swept through fixing zone, l2 storing heat therein. However, since unit ID has just previously been swept with steam, as described above and as illustrated in 1 the higher temperatures are concentrated in combustion-vaporizing zone l4 and in that portion of the fixing zone I! which is adjacent thereto; while the temperatures in the fixing zone l2 progressively decrease toward its exit end. The next main step, as shown in 1' corresponds to that shown in 1 except the order is reversed. Steam is passed through fixing zone i3 of unit i l toward, and through, combustionvaporizing zone 15. The passing steam abstracts heat stored during the preceding blow" as shown in 1, with the greatest cooling effect being produced near the exit end, and with the concentration of the highest temperatures at and near the combustion-vaporizing zone [5. The thus superheated steam is admitted to combustion-vaporizing zone ll of unit l0 concurrently with the addition of gas-making petroleum oil thereto. As described above zone gas-making oil may also be admitted to combustion-vaporizing zone l5 as the steam is passing therethrough. In unit III the oil is vaporized and pyrolyzed in the same manner as described previously with respect to 1 and the fixed gas leaves the exit end of fixing zone l2, going to the wash box.

The gas produced in each unit may then be treated by procedures which are well known in the gas-making industry, by being subjected to conventional cooling and condensing operations. Normally, the hot gas is fed to a wash box which is merely the primary condenser where the gas 9 is cooled to below the boiling point of water, and condensable constituents such as tar and other hydrocarbons -are removed. As stated above, a common wash box advantageously may be employed having a capacity adapted to receive the products from both units.

As indicated above, Figure 1 shows the main steps of the process and it will be understood that suitable purges may be, and advantageously are conducted between one or more of the various steps. For instance, between the steps set forth as 1 and 1 and between 1 and 1 a blast of air is advantageously swept through in the direction shown without introducing heating oil into the respective combustion-vaporizing zones. removes from the system undesirable products formed by the combustion of the fuel before the gas-making run is begun. Similarly, between the steps illustrated as 1 and 1 and between steps 1 and 1 a blast of steam is advantageously swept through the respective units in the direction shown to clear the system of oil-gas. In this purging step, there is also advantageously a blast of steam admitted from the exit end of the unit in which oil gas has just been made to insure that no explosive mixtures of gas and air will be obtained when the subsequent blow, or heating step is performed.

Figure 2, as stated, illustrates the main steps of the preferred embodiment of the present invention. As in Figure 1, there are shown in Figure 2 two oil gas-making units 20 and 2| each of which is provided with a combustion-vaporizing zone. i. e., 24 and 25, respectively, and a path of stored heat, or "fixing zone, 1. e. 22 and 23, respectively. As previously pointed out, while each gas-making unit is illustrated in the figure as a unitary structure, it will be understood that the combustion-vaporizing zone of each unit may be a separate structure or cell each of which is in flow communication with a separate fixing zone. As also pointed out above, wh le for the sake of description, distinct combustion-vaporizing zones and distinct fixing zones are shown in the drawings, it will be understood that often, in actual practice, no clear boundary line between the combustion-vaporizing zone and its communicating fixing zone can be fixed. Since the fi ure illustrates the main st ps of a complete cycle, it is to be understood that the system has been already heated to start the proce s. as is conventional, by burning fluid fuel in each combustion-vaporizing zone and blasting the hot combustion ases throu h the respective fixing zones. Units 20 and 2| may be connected to a common stack or, as is preferred. to separate stacks, in order to avoid "hot valves. and may be connected either to a common wash box, or to se arate wash boxes.

As shown in 2 which illustrates the heating step for un t 2|, the cycle may be started, after each unit has been heated, by passing air through one of the units. in this case unit 20, from the exit end thereof, 1. e. the end from which the made oil-gas leaves the unit, through the fixing zone 22 and the combustion-vaporizing zone 24, respectively. During its passage the air becomes progressively hotter'and at the same time cools the fixing zone 22 somewhat, by abstracting a portion of the heat stored therein. The hot air causes carbon deposited in combustion-vaporizing zone 24, and in that portion of fixing zone 22 which is adjacent combustionvaporizing zone 24 to burn. Deposited carbon in fixing zone 22 and combustion-vaporizing zone 24 is not only thus removed but also serves as This part of the fuel necessary for supplying heat to combustion-vaporizing zone 24 and to unit 2|. The resulting hot mixture of gases isthen admitted to combustion-vaporizing zone 25 of unit 2| concurrently with the addition of a fluid fuel thereto. Because of the large amount of sensible heat contained in the hot gases entering combustion-vaporizing zone 25, less fuel is required to supply heat to unit 2|, and that which is burned is burned more efiiciently. Additional air, supplementing any admitted from unit 20, may be supplied to combustion-vaporizing zone 25 if necessary. The combustion pr ducts from combustion-vaporizing zone 25 are swept through fixing zone 23, storing heat therein. However, since unit 2| has just previously been swept successively with air as described above, and with I steam as will be described below, relatively large amounts of heat, with correspondingly high temperatures, are concentrated in combustion-vaporing zone 25 and in that portion of fixing zone 23 adjacent combustion-vaporizing zone 25, while the temperatures in'fixing zone 23, rapidly decrease toward its exit end. The combustion products leaving fixing zone 23 may be directed to a stack where they are discarded.

The next main step, that is the gas-making step in unit 2|, is shown in 2 where steam is passedthrough unit 20 in the same manner as has been described with respect to 1 in Figure 1.' The steam passing through fixing zone 22 abstracts a further portion of heat stored therein. During its passage through fixing zone 22 the steam becomes progressively hotter until by the time it reaches combustion-vaporizing zone 24 relatively little heat is abstracted by the hot steam. As has been pointed out above with respect to Figure 1, some gas-making oil may be admitted into the passing steam at this point in combustionvaporizing zone 24. Nevertheless. due to its initial cooling effect the temperatures near the exit end of fixing zone 22 will be further lowered, resulting in even a greater temperature gradient between the two ends of the unit. The thus superheated steam is then admitted to combustion-vaporizing zone 25 of unit 2| concurrently with the admission of gas-making oil thereto. In combustion-vaporizing zone 25 vaporization and substantial cracking of the oil takes place. The mixture of cracked gas and steam then flows through fixing zone 23 in which its resides for sufilcient time for the cracked gas to become converted to stable gaseous molecules. The fixed gas, and steam, are then directed toa wash box.

Figures 2 and 2, which illustrate respectively the heating step for unit 20 and the gas-making step in unit 20, show a repetition of the steps outlined above with, however, a reversal of the order of units. As shown in 2, air is passed through fixing zone 23 and combustion-vaporizing zone 25. As in the previously described steps, carbon deposited during the preceding gas-making run, is burned and the hot mixture of gases is admitted to combustion-vaporizing zone 24 concurrently with the admission of fluid fuel thereto. The fuel is burned in the presence of the hot gases and the hot combustion products are swept through fixing zone 22, storing heat therein, and thence to a stack. As illustrated in 2 steam is then passed countercurrently through unit 2|, as was described above with respect to 2 and the thus superheated steam and gas-making oil are admitted concurrently to combustion-vaporizing zone 24 of unit 20. As has been described previously some gas-making oil may be admitted to 11 combustion-vaporizing zone 25 as the steam is passing therethrough, in which case it also enters combustion-vaporizing zone 24 concurrently with the steam. In combustion-vaporizing zone 24 the oil is vaporized and cracked, and the vaporized and cracked material is passed through fixing zone 22 as described previously. The fixed gases leaving unit 20 are directed to a wash box. The process as illustratedin Figure 2 is continued, of course, by repeating the cycle beginning with the steps shown in 2'.

As indicated above, Figure 2 shows the main steps of the preferred process and it will be understood that suitable "purges may be, and advantageously are conducted between one or more of the various'steps. For instance, between the steps set forth as 2 and 2 and between 2 and 2 a blast of air is advantageously swept through the respective units in the direction shown without introducing heating fuel into the respective combustion-vaporizing zones. This removes from the system undesirable products formed by the combustion of the fuel before the gas-making run is begun. Similarly, between the steps illustrated as 2 and 2 and between steps shown in 2 and 2', a blast of steam is advantageously swept through the respective units in the direction shown to clear the system of oil-gas. In this purging step, there is also advantageously a blast of steam admitted from the exit end of the unit in which oil-gas has just been made to insure that no explosive mixtures of air and gas will be obtained when the subsequent "blow," or heating step is performed.

As also seen in 2' there are means for selectively introducing steam or air into the exit end of each unit. One method of doing this is shown in 2 wherein conduits leading to the exit ends of each unit l and II are connected, through two-

way valves

21 and 28, respectively, to sources of steam and air. By this arrangement steam may be directed to either of the units as desired or turned off completely, or air may be directed to either of the units as desired or turned ofl completely. The succeeding steps shown in drawings 2 2 and 2 show the directions of flow of steam or air as the case may be. Similarly 2' shows means for selectively withdrawing the materials from the respective units. One method of doing this, as shown in 2 is by providing conventional conduits leading from the exit end of each unit II and II to a two-way valve 26 so that the gas coming from the respective units may be directed to a wash box as required. As also shown in 2 conventional conduits leading to a stack are provided. In this case also, the succeeding steps, as seen in 2, 2 and 2 show the direction of flow of materials from the exit ends of the respective units. There is, of course, as is also the case in Figure 1, conduit means interconnecting the combustion-vaporizing zone of each unit. In 2, 2", 2 and 2 the direction of flow through this conduit means is indicated.

Referring to the apparatus that may be employed, each part, i. e. the combustion-vaporizing zone and the fixing zone, may be those presently employed in the gas-making industry. As indicated above, the combustion-vaporizing zone may be any of the well known structures used for that purpose, such as the carburetor section of the conventional carbureted water gas apparatus, or one of the combined generator-carburetor structures of conventional oil-gas systems. Specifically, the combustion-vaporizing zone is merely a chamber of heat-conducting material,

12 which is capable of resisting high temperatures,

7 such as clay fire brick, carborundum brick, and

the like, designed for the combustion of the fluid heating fuel, and, after it has become sufiiciently heated. for the vaporization of the gas-making oil. The walls .of the chamber ordinarily provide sufllcient area to store the heat required for the subsequentvaporization and initial cracking of the gas-making oil. The chamber may be completely empty, or may have a portion thereof equipped with checkerwork of ceramic material, such as clay, fire brick, carborundum brick, and the like, in which sensible heat may be stored.

As is customary in present day oil gas-making procedures, the combustion-vaporizing zone is provided with a burner adapted to handle the particular fuel employed. Normally, the burner is essentially a jet or jets which inject the fuel into the combustion-vaporizing zone. The bumer may be provided with means to mix incoming air with the fuel before it is injected into the combustion-vaporizing zone, or some or all of the air may be separately admitted into the combustion-vaporizing zone. In any event, air and fuel are admitted to the combustion-vaporizing zones in the ratios providing efl'icient combustion of the fluid fuel. The combustion-vaporizing zones are also equipped with means for injecting the gas-making oil thereinto. Such means are well known in the gas-making industry and generally comprise a nozzle or nozzles adapted to spray the oil into the zone at the appropriate time.

With respect to air passed through one unit preparatory to its admission to the other unit during the heating steps, at least sufllcient air is passed through the first unit to burn the carbon therein. If the air passed through the first unit is just sufficient to burn carbon therein, supplementary air may be added to the combustionvaporizing zone wherein combustion of fluid fuel is taking place in an amount to support combustion of the fuel: On the other hand, air in excess of that required for burning the deposited carbon may be passed through the first unit, in

which case the amount of supplemental air required is correspondingly decreased. Thus, the amount of air passed through the first unit may besufflcient not only to burn carbon deposited therein but also to support the combustion of at least the major portion, and even all of the fluid fuel admitted to the combustion-vaporizing zones.

, With respect to the path of stored heat or fixing zone," it may be any of those structures which are well known and are used for that or similar purposes in the oil-gas, or carbureted water-gas. industry. It is essentially a large chamber of high temperature-resisting material such as fire brick. the inside of which is provided with many passage ways through which the gaseous material must flow. Customarily,-the inside is provided with a checkerwork of high temperatureresistlng material such as clay brick with the portion of checkerwork which is to be subjected to the highest temperatures, i. e. that portion which is nearest the combustion-vaporizing zone, being made of carborundum brick. The fixing zone is of suflicient volume to permit the passing gases to reside there until converted or fixed" into stable commercial oil-gas. The exact size and shape of the fixing zone will be dictated by the considerations well known in the gas-making industry, including capacity desired, requisite holding time, and the like.

Referring to the fuel employed durng the "blow or heating step for storing heat in each unit, as indicated previously, it may be any of the fluid fuels ordinarily employed in the gasmaking industry such as petroleum oil, tar, gas, and the like. Generally, the fuel employed will be a petroleum oil and a wide variety of such oils are available for this use such as Numbers 2 and 3 furnace oils, heavy residuum oils, and the like. As stated, tar, such as coal tar, carbureted water gas tar, and oil gas tar such as is obtained in the process, may also be used as the fuel, in which case it will possess sufficient fluidity to be handled by the burner and injected into the combustion-vaporizing zone. The proper fluidity may be obtained in some cases by heating the tar, or heavy oil if used, or by thinning them with less viscous miscible liquids of the same nature, or by a combination of these means.

As indicated above, the preferred process permits the utilization of a wide range of gas-mak ng petroleum oils. Whereas previous processes were restricted to the use of petroleum oils containing less than 7%, and preferably less than 4%Conradson carbon, the present preferred process is readily adapted for the utilization of petroleum oils containing as high as 13% Conradson carbon or even higher. (Conradson carbon is the proportion of carbonaceous residue remaining after a standardized heating cycle is performed on aweighed quantity of the particular oil following the procedure set forth under the A. S. T. M. designation D189-36. In accordance with that procedure, a weighed quantity of oil is heated at a predetermined rate in a crucible until a cokelike residue is left, and this residue is then heated to red heat. From the weight of the carbon remaining, the Conradson carbon content of that oil is calculated as the percentage thereof based on the weight of the oil sample employed.) In any event, any of those petroleum oils heretofore used such as gas oil or diesel oil or lighter hydrocarbons. for example, kerosene, gasoline, liquefied petroleum gases, such as propane. butane and the like, may be employed, and, when the preferred process is practiced, petroleum oils which have heretofore been unusable such as those containing more than about 7% Conradson carbon, may be used.

In accordance with the present process steam which has been superheated as described, is introduced into the combustion-vaporizing zone concurrently with the gas-making oil in order to reduce the partial pressures of the oil vapors. The relative proportions of superheated steam and gas-making oil may vary widely as is well known in the art. For example, the proportion of steam to gas-making oil may range from about 1 part of the former to l of the latter, by weight, to about 1 part of the former to about 10 parts of the latter by weight.

The average temperatures in each unit will be similar to those employed during conventional procedures, for example, between about 1150 F. and about 2000 F. and preferably between about 1400 F. and about 1650 F. However, it will be realized that due to the novel procedure herein set forth, relatively higher temperatures, e. g. 100 F. to 500 F. higher, than heretofore will be concentrated at the combustion-vaporizing zones of each unit, while the temperature near the exit end of each fixing zone will be somewhat lower, e. g. 100 F. to 500 F. lower, than those employed in conventional processes.

The following examples illustrate the operation of the process and are not intended to limit the scope of the invention in any way.

EXAMPLE I Two gas-making units were set up. each of which comprised a combustion-vaporizing zone and a fixing zone. Prior to the gas-making run in each unit, steam was superheated in the other as described herein, and prior to the blow in each unit air was passed through the other unit, as also described herein. The test lasted 22.58 hours during which time there were about 170 cycles. Each cycle lasted 8 minutes. The combined blow periods consumed about 51% of each cycle, and the combined make periods consumed about 39% of each cycle. Purges and valve action accounted for the remaining time in each cycle.

The oil employed, both as gas-making oil and as fuel oil was a petroleum oil having a Conradson carbon content of 0.2%. Unit #1 used 2260 gallons of fuel oil, and unit #2 consumed 3313 gallons, indicating a total consumption of fuel oil amounting to 1.01 gallons per thousand cubic feet of gas made. Unit #1 consumed 32,981, galions of gas-making oil, and unit #2 consumed 33,342 gallons, indicating a total consumption of gas-making oil mounting to 11.98 gallons per thousand cubic feet of gas made, and a total consumption of oil, both fuel and gas-making, of 12.98 gallons per thousand cubic feet of gas.

The average temperatures during the operation were as follows:

F. Combustion-vaporizing zone #1 1740 Bottom of fixing zone #1 1665 Top of fixing zone #1 1370 Combustion-vaporizing zone #2 1440 Bottom of fixing zone #2--. 1690 Top of fixing zone #2 1090 EXAMPLE II The same procedure was followed as in Example I with the exception that a petroleum oil with a Conradson carbon content of 6.02% was employed as fuel oil and gas-making oil.

Time of operation 17 hours Time of each cycle; 8 minutes Time consumed in bl0w" 48% Time consumed in make- 43% Gallons fuel oil consumed:

Unit i'l -i 1.8 5 gals. Unit #2 1,867 gals. Volume of gas made 4,294 MCF" Heating value of gas 1017 B. t. u./cu. ft. Gallons fuel oil consumed/MCF gas .87 gnls./i\l(,.l- Gallons gas-making oil consumed Unit #1 23.018 gals. Unit #2 23. gals 10.76 alsf/MCF Gallons gas-making oil/MCF gas 11.63 gals/CF Gallons total oil used/MCF gas"--. Avcra ge temperatures Combustion-vaporizing zone #1 1570 F. Bottom of fixing zone #1 1600 I". Ton of fixing zone itl 1200 F. Combustionwaporizingzon 1430 F. Bottom of fixing zone #2.. 139 F.

Top of fixing zone #2 I. 1040 l". Steam rate during "make lbs. per lllllllll'e' Air rate during blow:

Preheated 16,536 cu.ft.permin.

Supplemental 11,596 cu.ft.per miu. MCF==Thousand cubic feet.

18 EXAMPLE!!! The same procedure was iollowe'd as in the foregoing examples'with the exception that a. petroleum oil having a Conradson carbon con- 18 to store heat therein; abstracting a portion of the heat stored in the fixing zone and in the combustion-vaporizing zone of the other of said gas-making units by passing steam through said tent of 1333, was used as fuel on and as gas 5 fixing zone in the direction of its communicating making 01L Y I combustion-vaporizing zone and thence through Ti f do 24 hm said combustion-vaporizing zone to superheat T1515 .irfiit $211122: s minutzs said steam; admitting said superheated t gme consu ::11::g\ :g" g; to the combustion-vaporizing zone of the said on congumed; l first'mentioned cur ently the 8dg g fig-g s missionof petroleum oil thereto; vaporizing and x i f 33; gggggfiitdpl H pyirilyzinghsaiddpetizoleum oil in the presence of I 0 8" r a super eate s am in the combustion-vaporizing zone and fixing zone of said first-meng3}: tioned unit; withdrawing the vaporized and pyro- Gallonu-gas-EltihEdil}ibi gas: I. iifss cr' lyzed 11 an Steam from said first-mentioned $3 5 1 $3 33520 8 1157/1?F unit; then introducing air into the combustiong r i busmgr v orlzm ne #1 1530 vfiriiifilgmzonemcliif said second-mentioned unit 118mm! 5 w e ng d fuel therein, the resulting i iisgfo vzg siz i n i26553551323 1 hot gaseous products being swept through its ggg g g f ggfg z y f i $38; communicating fixing zone to store heat therein; fiseamtradte glut-l ng:l mhke" 129 lbs/minute agi por ion of t e eat Stored in the e 11 ng zone and the combustion-vaporizing zone glfgggn ieniafjl::ILIIlZZ: v of said first-mentioned unit by passing steam The advantages of the present process will be through said fixing zone in the direction of its more readily ap reciated by a consideration of communicating Zone and the following ta le. m the table, data collected thence through Said combustion-vaporizing mm from tests similar to those set forth in the ex- Superheab Said Steam; admitting Said superr amples were converted to the basis of 1,000 cu. heated steam to the cmbustion'vaprizmg zone it. of 1000 B. t. u. gas. Four difierent oils were of the Said second'menfloned unit concurrent employed, m group A a 02% Comadson carbon ly with the admission of petroleum oil thereto; oil was used; in group B a 3% Conradson carvaporizing and pyrolyzmg 581d petroleum bon n was used; in group c a 5% Com-M150 in the presence of said superheated steam in carbon oil was used, and in group D is a 13% the combustion-vaporizing zone d fixing Com-Son carbon on was used In each group of said second-mentioned unit; withdrawing the with the exception of group D, performance data vaporized and pyrolyzed on and steam from said obtained as the result of the present process second-mentioned unit, and repeating cyclically listed as the odd numbered tests, are compared said sequence of stepst t obtained as the result of a convem 2. The process of claim 1 wherein the fluid tional gas-making procedure listed as even-numfuel Petroleum bered tests. Since group D employed 13% co 3. The process of claim 1 wherein the fluid radson carbon oils, the apparatus of the convenfuel 18 tional procedure became clogged and no data 4. The proc s '01 e tu e o 011 as could be collected. 5 by the pyrolysis of petroleum oil in which heat Table I Group Tet iii/tot tiihiiifrt" 3.52: Per Can! A 1 .90 11.50 12.40 248 78.6 2 1. to 11. 42 13.11 200 75. a B a .19 11.40 12.19 213 80.4 4 .aa 12. 13. as 14. 5 c 2 a as as s is: D u g .28 11.00 11.91 149 30.0

' Thousand cubic feet of gas.

Heat unitsingas andtarbosedonheat unitsinstarting oil.

Considerable modification is possible in the is stored in each of two gas-making units, each variation of details in practicing the process of of which gas-making units comprises a fixing the present invention without departing from zone in flow-communication with a combustionthe scope thereof. vaporizing zone, the combustion-vaporizing zones I claim: of said two gas-making units being in flow-com- 1. The process for the manufacture of oil gas munication with each other, which comprises by the pyrolysis of petroleum oil in which heat is abstracting a portion of said stored heat from stored in each of two gas-making units, each of the fixing zone and combustion-vaporizing 0 8 which gas-making unit comprises a fixing zone in of one of said units by passing air through said flow-communication with combustion-vaporizfixing zone in the direction of its communicating zone, the combustion-vaporizing zones of said ing combustion-vapori n Z n and hence two gas-making units being in fiow-communicathrough said combustion-vaporizing zone of tion with each other, which comprises introsaid first-mentioned unit; admitting the resultducing air into the combustion-vaporizing zone i h gases to e m t n-v p i z n of one or said units while burning fluid f l of the other of said units while burning fluid fuel therein, the resulting hot gaseous products bet in. the resulting hot gase us p du ts eing swept through its communicating fixing zone ing swept through the fixing z e i i se ond- 17 mentioned unit to store heat therein; abstracting a further portion of heat from the fixing zone and combustion-vaporizing zone of said firstmentioned unit by passing steam through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustion-vaporizing zone, to superheat said steam; admitting said superheated steam to the combustion-vaporizing zone of said second-mentioned unit concurrently with the admission of petroleum oil thereto; vaporizing and pyrolyzing said petroleum oil in the presence of said superheated steam in the combustionvaporizing zone and fixing zone of said secondmentioned unit; withdrawing said vaporized and pyrolyzed oil and said steam from said secondmentioned unit; then abstracting a portion of said stored heat from the fixing zone and combustion-vaporizing zone of said second-mentioned unit by passing air through said fixing zone in the direction of its communicating combustionvaporizing zone and thence through said combustion-vaporizing zone, to raise the temperature of said air and to burn carbon in said fixing zone and said communicating combustion-vaporizing zone of said second-mentioned unit; admitting the resulting hot gases to the combustionvaporizing zone of said first-mentioned unit while burning fluid fuel therein, the resulting hot gaseous products being swept through the fixing zone of said first-mentioned unit to store heat therein; abstracting a further portion of heat from the fixing zone and combustion-vaporizing zone of said second-mentioned unit by passing steam through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustionvaporizing zone, to superheat said steam; admitting said superheated steam to the combustion-vaporizing zone of said first-mentioned unit concurrently with the admission of petroleum oil thereto; vaporizing and pyrolyzing said petroleum oil in the presence of said superheated steam in the combustion-vaporizing zone and fixing zone of said first-mentioned unit; withdrawing said vaporized and pyrolyzed oil and said steam from said first-mentioned unit, and repeating cyclically said sequence of steps.

5. The process of claim 4, wherein the fiuid fuel is petroleum oil.

6. The process claim 4, wherein the fiuid fuel is tar.

EDWIN L. HALL.

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

UNITED STATES PATENTS Duncan July 16, 1940

Claims

1. THE PROCESS FOR THE MANUFACTURE OF OIL GAS BY THE PYROLYSIS OF PETROLEUM OIL IN WHICH HEAT IS STORED IN EACH OF TWO GAS-MAKING UNITS, EACH OF WHICH GAS-MAKING UNIT COMPRISES A FIXING ZONE IN FLOW-COMMUNICATION WITH A COMBUSTION-VAPORIZING ZONE, THE COMBUSTION-VAPORIZING ZONES OF SAID TWO GAS-MAKING UNITS BEING IN FLOW-COMMUNICATION WITH EACH OTHER, WHICH COMPRISES INTRODUCING AIR INTO THE COMBUSTION-VAPORIZING ZONE OF ONE OF SAID UNITS WHILE BURNING FLUID FUEL THEREIN, THE RESULTING HOT GASEOUS PRODUCTS BEING SWEPT THROUGH ITS COMMUNICATING FIXING ZONE TO STORE HEAT THEREIN; ABSTRACTING A PORTION OF THE HEAT STORED IN THE FIXING ZONE AND IN THE COMBUSTION-VAPORIZING ZONE OF THE OTHER OF SAID GAS-MAKING UNITS BY PASSING STEAM THROUGH SAID FIXING ZONE IN THE DIRECTION OF ITS COMMUNICATING COMBUSITON-VAPORIZING ZONE AND THENCE THROUGH SAID COMBUSTION-VAPORIZING ZONE TO SUPERHEAT SAID STEAM; ADMITTING SAID SUPERHEATED STEAM TO THE COMBUSTION-VAPORIZING ZONE OF THE SAID FIRST-MENTIONED UNIT CONCURRENTLY WITH THE ADMISSION OF PETROLEUM OIL THERETO; VAPORIZING AND PYROLYZING SAID PETROLEUM OIL IN THE PRESENCE OF SAID SUPERHEATED STEAM IN THE COMBUSTION-VAPORIZING ZONE AND FIXING ZONE OF SAID FIRST-MENTIONED UNIT; WITHDRAWING THE VAPORIZED AND PYROLYZED OIL AND STEAM FROM SAID FIRST-MENTIONED UNIT; THEN INTRODUCING AIR INTO THE COMBUSTIONVAPORIZING ZONE OF SAID SECOND-MENTIONED UNIT WHILE BURNING FLUID FUEL THEREIN, THE RESULTING HOT GASEOUS PRODUCTS BEING SWEPT THROUGH ITS COMMUNICATING FIXING ZONE TO STORE HEAT THEREIN; ABSTRACTING A PORTION OF THE HEAT STORED IN THE FIXING ZONE AND THE COMBUSTION-VAPORIZING ZONE OF SAID FIRST-MENTIONED UNIT BY PASSING STEAM THROUGH SAID FIXING ZONE IN THE DIRECTION OF ITS COMMUNICATING COMBUSTION-VAPORIZING ZONE THENCE THROUGH SAID COMBUSTION-VAPORIZING ZONE TO SUPERHEAT SAID STEAM; ADMITTING SAID SUPERHEATED STEAM TO THE COMBUSTION-VAPORIZING ZONE OF THE SAID SECOND-MENTIONED UNIT CONCURRENTLY WITH THE ADMISSION OF PETROLEUM OIL THERETO; VAPORZING AND PYROLYZING SAID PETROLEUM OIL IN THE PRESENCE OF SAID SUPERHEATED STEAM IN THE COMBUSTION-VAPORIZING ZONE AND FIXING ZONE OF SAID SECOND-MENTIONED UNIT; WITHDRAWING THE VAPORIZED AND PYROLYZED OIL AND STEAM FROM SAID SECOND-MENTIONED UNIT, AND REPEATING CYCLICALLY SAID SEQUENCE OF STEPS.