US2744814A

US2744814A - Apparatus for the production of fixed gas from fuel oil

Info

Publication number: US2744814A
Application number: US210005A
Authority: US
Inventors: Charles B Francis
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-02-08
Filing date: 1951-02-08
Publication date: 1956-05-08
Anticipated expiration: 1973-05-08

Description

y 8, 1956 c. B. FRANCIS 2,744,814

APPARATUS FOR THE PRODUCTION OF FIXED GAS FROM FUEL OIL Filed Feb. 8, 1951 2 Sheets-Sheet 1 xrrozA/awof- C. B. FRANCIS May 8, 1956 APPARATUS FOR THE PRODUCTION OF FIXED GAS FROM FUEL OIL Filed Feb. 8. 1951 2 Sheets-

Sheet

2 ,2 z z a k 2 H -II- d m f m m e 1 -I' i-M :l- 2 m/ Q J AM/ z a \B -1 Il l- -l 21... 5 f m e I -II- I l -lh 0-|-M a 2 z United States Patent 1 2,744,814 APPARATUS FOR THE PRODUCTION OF FIXED GAS FROM FUEL OIL Charles B. Francis, Pittsburgh, Pa. Application February 8, 1951, Serial No. 210,005 3 Claims. (Cl. 48-105) This invention relates to apparatus for the conversion of liquid and liquefiable carbonaceous fuels to fixed gases. The term fixed gases includes any mixture of compounds and elements that remain in the gaseous state at ordinary atmospheric temperatures and pressures. Such mixtures may be entirely consumed as fuels directly or may be processed to obtain certain substances which may be used for other purposes.

More particularly, the invention relates to the conversi-on into fixed gases of such carbonaceous liquids as coal tar and soft pitch, which are now largely consumed as liquid fuels, and hydrocarbon oils, such as crude petroleum, and the residues resulting from the high temperature processing thereof, which residues have heretofore been used mainly as liquid fuels in certain types of furnaces and processes operating at high temperatures. In addition to the named liquids, the apparatus is also adapted to effect the conversion to fixed gases of certain animal and vegetable oils, and to the conversion to fixed gases of many waste products, such as used automobile oils, discarded wash oils, etc.

The advantages of a fixed gaseous fuel, such as natural gas, for use in certain industrial processes, as Well as for household use, are well known. In many districts natural gas is not available. In other districts, which are supplied with natural or manufactured gas, shortages are often experienced.

It is an object of the present invention to supply these deficiencies with a fuel gas of high heating value-a fuel gas manufactured from any carbonaceous liquid available, including such waste products as those mentioned.

Most large steel producers make coke, and in the process great quantities of coal tar and/or soft pitch are produced and used as fuel. But the use of tar as fuel is restricted to certain furnaces, such as open hearths, that operate at high temperatures. The tar or pitch is viscous, and costly to handle, particularly in cold Weather. Also, such viscous materials are generally produced at a distance from the points of consumption and must be transported in tank cars or trucks to such points.

A further object of the present invention is to provide 4 an apparatus whereby the tar or pitch may be economically converted at the point of production or origin into a sulfur-free fixed gas, and then delivered in gas lines (many of which are already in existence) to the points of consumption.

Fixed gases suitable for use as gaseous fuels have for many years been produced from petroleum residues. These gases are commonly designated as oil gas. In general, oil gas varies in composition and heating value about as follows:

Range in Typical Analyses, Per- Oil Gas Constituents Percent by cent by Volume of 3 Volume Specimens Methane, CH4 27. 6 to 43. 2 27. 6 43. 2 30.0 Ethane, O HB, and Propane C; s 00to 64 0.0 6.4 1.0 Ethylene, 02134, and other olefins 3. to 17. 0 3. 5 17. 0 26.0 Acetylene, 02114... 0. O to 0. 5 0.0 0. 5 1.1 Hydrogen H2 50. 8 to 23.2 50. 8 23. 2 9. Carbon monoxide, CO 10. 2 to 3. 6 10. 2 3. 6 2. Carbon dioxide, 00;. 2. 6 to 1. 1 2. 6 1.1 3. Oxygen, Oz O. 2 to 1.0 0.2 1.0 2. Nitrogen and other inert gases. 5.1 to 4.0 5.1 4.0 25.

Total 13. t. u. per cu. ft. 548110 975 548 975 1,030

Still a. further object of the present invention is to control the heating value of a fixed gas, produced from the materials indicated, at any desired value between 500 and 1000 B. t. u. per cu. ft., and to produce a clean vapor free gas having a heating value practically constant, so that burners may be adjusted and combustion accurately controlled over any desired period of time. Also, an object is to provide for the control of the specific gravity of the gas produced in those instances when desired.

With the exception of those apparatus that effect the partial combustion of the oil with air or oxygen, and those using nickel catalyst (which are poisoned by the sulfur in mineral oils), practically all of the apparatus used heretofore for converting liquid hydrocarbons into fixed gases are intermittent in operation, requiring the use of a set of two producer units, these units consisting essentially of two or more checker chambers of brick, into one of which oil and steam are injected while the other is being heated to restore its temperature and eliminate carbon depositions. Such intermittent operation is very inefiicient for reasons which this specification need not become involved.

Another object of the invention is to provide an apparatus that may be operated continuously as a unit or producer, whereby gas may be produced uninter'ruptedly from a given fuel oil, and at a controlled rate over long periods of time.

Still other objects will be apparent in the following specification.

In the accompanying drawings, apparatus embodying the invention is illustrated, the apparatus selected in this case being a small unit, designed to convert about 15 gal. of oil per hour into about 4,000 cu. ft. of gas, having a heating value of from 500 B. t. u. to 600 B. t. u. per cu. ft:

Fig. 1 is a diagrammatic view. illustrating the apparatus in longitudinal, vertical section; I

Fig. 2 is a view in horizontal section of the gas generator unit of the apparatus, as seen on the plane II--II of Fig. 1;

Fig. 3 is another view in horizontal section of the generator unit, as seen on the plane Ill-III of Fig. '1;

Fig. 4 is still another view in horizontal section of the generator unit, as seen on the plane IV-IV of Fig. 1; Fig. 5 is a view in vertical section of a pressure-regulating electrical switch included in the apparatus for automatically controlling the generation of gas according to the rate at which it is consumed; and

Fig. 6 is a developed view or layout of a vaporizer or boiler included in the apparatus.

Referring to the drawings, the apparatus comprises a gas generator unit 1, a gas-scrubbing or purifying unit 2, and a gas receiver tank 3. The tank 3 is not essential to the process, and may be varied in design and size. Indeed, it may comprise merely an enlargement in the gas main, or it may comprise a gas storage tank of any capacity desired. The gas-scrubbing and purifying unit 2 is essential only in the event it is desired to cool the gas, or to free it from oil and water vapors, and/or sulfur compounds.

The generator unit 1 comprises a catalyst chamber 5,

constructed of heat-resistant metal, typically chrome nickel-molybdenum alloy steel. This chamber contains a porous catalyst body 6 formed of hard hematite, crushed and graded in lumps or pieces from /2" to M1" in size. The catalyst chamber is arranged within a heating chamher 7. In the smaller sizes of gas generators it may be practical to supply the necessary heat in chamber 7 by means of electrical resistors, but in the illustrated unit, as well as in units of larger size, the heat is preferably supplied by burning oil and/or gas. In the present case a combination oil-gas burner 8 is mounted on the generator gra am.

body at or near the zone of the section plane 11-11 in Fig. '1, and is of the construction shown in Fig. 2. The burner is arranged to project its flame parallel to a line tangent to the inner face of the wall of the combustion chamber 7. A flue 73 for the products of combustion opens through the top of the generator. In starting with the generator cold, this burner is operated on a light fuel oil injected with air under super-atmospheric pressure, until the generator is producing gas, at which time the oil is turned off and the generator is heated by a small portion of the gas generated, delivered to the burner through a line 9 leading from the gas delivery line 463 of the apparatus.

'The walls of heating chamber 7 are formed of steel plate 11, lined with refractory material. A storage box '12 is located on top of the catalyst chamber 5 and holds enough of the sized hematite to fill the catalyst chamber. At the bottom of the generator a catalyst-receiving box 13, formed of ordinary carbon steel, is provided.

A thermo-electric pyrometer 14 projects into the combust'ion chamber, and, when the generator is making gas,

this pyrometer (in conjunction with conventional control devices, not shown) automatically controls the flow of gas to the burner, to maintain the temperature at any desired point within the working range of 1500 F. to 1700 F., as revealed by an indicator 14ft.

Such control devices are well-known in the art and it .is needless to an understanding of the present invention to illustrate them, .or to describe their operation in detail herein. Within the generator means are provided to produce superheated steam, which is a gaseous oxidizing agent, for use in the production of fixed gas. Such means may comprise a boiler formed of four pairs of

vertical tubes

21, 21a, 21b and 21c (Figs. 3 and 6) that are preferably embedded in the refractory lining it) of the combustion chamber, and lie within the flanges of steel channels 22 that support or reinforce the steel walls 11 of the chamber 7. The two tubes of each pair are inter-connected by tubes 21d adjacent their lower ends and by tubes 21e adjacent their upper ends, and the four pairs of tubes are inter-connected in series adjacent their upper ends by means of pipes 21 Water is supplied by a line 15 to an overhead tank 16 which includes a ball-valve 17 for maintaining the water in the tank at desired hydrostatic head. Water from tank 16 is delivered by way of a pipe 18 to the bottom of boiler tubes 21-21 the rate of flow being measured by flow meter 19 and regulated by valve 20; and the steam generated in such tubes is delivered by way of a pipe 23 to a manifold 24 that encompasses and is welded to the heat-conducting wall of catalyst chamber 5, in the position shown in Fig. 1. In its flow in tube 23 and manifold 24 the steam is highly superheated for the chemical reactions presently to be considered. Pet cocks 51 and 52 are connected at suitable points to the boiler tubes for testing. The described arrangement of tubes provides a boiler that utilizes, for the generation of steam, heat which would otherwise be ..lost by radiation from the walls of thegenerator.

liquids that may be used for the production of fixed gas,

the products of combustion in chamber 7 may be employed to preheat such liquids. As one example of the way this may be done, a pipe coil 300 is shown at the top of the combustion chamber, and the viscous liquid may be passed through this pipe, whereby the viscosity of the liquid is lowered and the temperature raised.

The liquid fuel, drawn through pipe 27 from thesup- ;p ly,.-is forced through a flow meter 28 and feed line 30 to an injector pipe 29 located at an intermediate zone in the catalyst chamber, as shown. The pipe 29, otherwise closed at its inner end, is provided with a small to A hole positioned in its wall to direct a jet of oil downwardly. The injector pipe 29 is connected to the oil feed line 30 by a union 31, and extends through a heat resistant shield tube 32, which projects through and is welded to the wall of the catalyst chamber 5. It is important that the jet of oil be directed downwardly through a small orifice. I have found that an injector tube with open end or large delivery orifices soon becomes clogged with carbon. It is further important that the steam shall be injected or shall be effective below the point or points of admitting the oil to the catalyst.

The motor 269 that drives the pump 26 is started by closing a switch 33. Thereafter, the operation of the pump and its motor is controlled by the pressure of the gas in tank 3, through the instrumentality of a special pressure regulating electrical switch 34, later described in detail. By means .of said switch 34, which may be set to respond to a pressure between one-half lb. and two lbs. in tank 3, the energizing circuit of the pump motor 266 is interrupted when the pressure in tank 3 reaches that at which said pressure-regulating switch is set. The circuit is reclosed when the pressure in the tank drops below that at which such switch is set. In thisway the generation of gas is automatically controlled and adjusetd to the rate at which the gas is used, up to the maximum capacity of the generator. The float-valve in tank 16 and the valve 20 control the flow of water to the generator, and these valves, in conjunction with the gas-pressure-controlled oil pump 26, provide for accurate proportioning of the oil and water flow to the generator. Other devices may be designed or may exist for accomplishing the same results, but they are more costly and less reliable than the device 34. For example, if a water pump and an oil pump were driven by a single motor that stops the flow of both oil and water at the same time, the results would be imperfect, since the flow of'the water should be maintained for several minutes after the oil is shut of, to prevent the formation of coke carbon, and to permit the regeneration of the catalyst in chamber 5.

In preparing the apparatus for service, the catalyst chamber 5 and storage box 12 are filled with the crushed and sized hard hematite, and gasketed covers 35 and 35a are securely bolted in place over the charging openings in the top of storage box 12. The generator is gradually heated to a temperature of 1650 F., as shown by the indicator 140.

While the generator is being heated, the gas scrubbing and purifying units are prepared for use. The scrubbing and purifying units include a cooler and scrubber unit 36, an oil separator 37, a sulfur remover 45 (employed only where the removal of sulfur is needed), and an oil scrubber 46. The scrubber 36 and the oil separator 37 are charged with cold water by opening a valve 38 in a pipe leading from'the water supply line 15.

The scrubber 36 comprises a vertical steel tank, having a pipe 360 extending from apoint midway of its vertical extent downwardly to the oil separator 37, which also comprises a vertical tank, arranged at lower level than tanlr 36. When the rising level of the water in tank 36 reaches the mouth of pipe 360, water flows through such pipe into the oil separator'37, and when the level of the water rising in the oil separator reaches the point where it appears in a sight gage 39, the water inlet valve 38 is closed. Next, if sulfur-free gas is desired, a few pounds of slaked lime are introduced through cover 40 of a sealed container 42, the lime being placed and supported upon a perforate partition or screen 41. The cover 40 is then sealed in place on the top of container 42, and a valve 43 is opened to admit water from supply line 15. The water rises through the body of lime on screen 41 until its level reaches the opening of a pipe 420 leading from container 42 to the top of the sulfur remover 45.

The sulfur remover 45 comprises a vertical tank having a water-overflow pipe 450 leading into the oil separator tank 37. As the water rising in tank 45 reaches the mouth of pipe 450, it overflows through the latter pipe into the oil separator tank 37, with the efiect that the level of the water in sight gage 39 begins to rise. At this time the valve 43 is adjusted in a position which (in the case of the 5000 C. F. H. apparatus herein illustrated) reduces the flow to about one quart per minute. fiow is determined by opening valve 44 in a line 440 leading from the bottom of the oil separator 37 and measuring the water delivered. The valve 43 is manipulated until it reaches the position at which the flow through pipe 440 reaches the desired rate. The water running from pipe 440 may be led to a drain line, sewer, or other convenient point of disposal. When the desired flow of water has thus been established through the lime container 42, the tank 45, the tank 37, and drain line 440, the valve 38 is reopened and adjusted in such position that the total flow of water from drain line 440 equals about one gallon per minute when the water is at 40 F., or one and one-half gallonsper minute when it is at 65 F. The level of the water is thus established at operating levels in scrubber 36, sulfur remover 45, lime container 42, and oil separator 37. Then, the positions in which the

valves

38 and 43 have been adjusted are marked and the valves closed.

The oil scrubber 46 is now made ready. The oil scrubber consists in a vertical tank having two

horizontal partitions

460 and 461, as shown. The chamber 470 above partition 460 includes a bubbler cap 67, whose lower edge is notched, as shown. The cap 67 seats over the upper end of a tube 68 which extends downwardly through the partition 460 to a bubbler cap 69 at the bottom of the tank. In preparing the-oil scrubber for service, light oil (such as No. l or No. 2 fuel oil) is introduced .to the upper chamber 47 by way of a funnel inlet 48 including a valve 4&0. From the chamber 47 the oil runs into chamber 470 by way of a by-pass 490 that includes a valve 49. The oil rises in chamber 470 to the level at which it overflows the upper edge of tube 68, whence it falls through such tube to the bottom of tank 46, where it forms a body of oil that envelopes the bubbler cap 69. When adequate pools of oil have thus been formed around the bubbler caps 67 and 69, the valve 49 is closed and the chamber 47 is filled, whereupon the pouring of oil into the funnel is discontinued and the valve 430 closed. Next, the valve 49 is opened, and is adjusted in such position that the oil flows through by-pass 490 at a rate of about-sixty drops per minute, as may be checked by means of a sight-glass 50 included in the bypass. A vent tube 471 opens through the partition 461 and extends almost to the top of chamber 47. The oil is fed at the rate of about sixty drops per minute as long as the generator remains in operation. I,

While the scrubbing and purifying units are being brought into service condition as described above, the firing of the combustion chamber is continued, until the temperature therein reaches 800 F. or 900 P. Then, the petcock 51 and valve 20 are opened, admitting water into the boiler 21-Z1f. When water flows from said petcock, the petcock and valve 20 are closed and petcock 52 opened. Petcock 52 remains open until the temperature in the combustion chamber 7 reaches 1650 F., at which time petcock 52 is closed, and valve 20 is. adjusted to provide for a flow of water at a volumetric rate equal to one-half that of the oil delivered by pump 26 for conversion to gas.

In the particular case of the generator illustrated and described herein the water flow may be at a rate of one pint per minute. Next, any excess water in the scrubbers is displaced and theapparatus tested for leaks, by admitting compressed air into line 57 through an inlet 570 until the pressure in tank 3 rises to two lbs. The specified flow of cooling and scrubbing water is then estab- The rate of l lished by opening and adjusting

valves

38, 43 and 44, the

valves

38 and 43 being opened at the marked positions already determined for the required flow.

To start the production of gas, main delivery valve 53 is opened, switch 33 is closed to start the oil pump, and valve 54 is opened until the flow meter 28 indicates the flow of oil desired one quart per minute for the illustrated generator. Gas is formed at once and soon displaces all the air in the apparatus. With the catalyst chamber 5 filled with freshly prepared hematite, the gas is high in C02 and N2 for the first five to ten minutes, and this gas may be wasted by temporarily closing valve 53 and opening petcock 530. The gas released through petcock 530 may be burned. After about ten minutes the petcock 530 is closed and main delivery valve 53 is opened, allowing the gas to flow to the desired points of consumption.

The conversion of the oil to gas is effected within a fraction of a second by a series of physical and chemical reactions. For example, when No. 2 fuel oil is injected (as at 29) into the hot hematite it is first volatilized and then decomposed by the process known as cracking to lighter or more volatile compounds and carbon. The car- Reaction a occurs only when the catalyst is new. The surfaces of the pieces of hematite (F6203) that form the catalyst are soon reduced to magnetite (Fe3O4) where upon only Reaction b can occur, such Reaction b taking place only on the surfaces of the pieces of ore. These changes and reactions give a mixture of fixed gases composed of C0 and H2, plus vapors composed of water and light oils. As these mixtures ascend through the hot ore body above, some of the light oils undergo, while passing through super-heated tubes 55 and 55a, a pyrolysis which results mainly in the formation of unsaturated hydrocarbons known as olefins, while others of the light oils react with the ore and water to form CH4, Hz and CO. If the gas is not cooled quickly, the olefins tend to polymerize, forming aromatic compounds and H2. Furthermore, if the generator is operated at maximum capacity, and particularly at temperatures near 1500 F., a little oil vapor escapes unchanged with the gas passing through the pyrolysis zone or super-heated tubes 55 and 55a at a high velocity.

In chamber 5 the gases, together with some water and oil vapors, leave the ore body at a temperature between 1300 F. and 1500 F, and pass through a duct 57 into the cooler and scrubber 36. At the top of this scrubber cold water, entering a manifold 58, is sprayed through orifices 580 into the gas, thereby cooling it. The gas flows downwardly through a tube 5b into a distributing or bubbler cap 60, from the bottom of which the gas rises t and bubbles through'a column 600 of water extending to a height slightly above the bottom edge of the mouth of overflow pipe 360. By this scrubbing action, most of the water and oil vapors are condensed, and, the oil in globule form escapes with the cooling Water through the overflow 360. In this scrubber '36 some sulfur and other water-soluble compounds are separated from the gas. The temperature of the overflow water from this scrubber is kept below F. If the temperature rises above this value the how ot water is increased by adjusting valve 38. If, in order to keep the temperature of the water down to desired value, the flow is increased to a rate at which the water level rises above the gage glass 62, drain valve 63 at the bottom of the scrubber is opened until the Water reaches the normal level, whereupon valve 63 is closed and the flow through valve 4-4 re-adjusted. Cleanliness of the gas is tested by opening a petcock 64 provided at the top of scrubber 36. The escaping gas is ignited and a flame kept burning with a long candle-like flame.

The gas leaving the scrubber 36 at a temperature of from 100 F. to 120 F. carries with it some entrained water and oil, some fog, and part of the sulfur in the gas developed in the generator, mainly in the form of H2S- an acidic gas. To remove these impurities the gas is passed through a second scrubber 4-5, which is practically a duplicate of the first scrubber, but somewhat smaller in size. As the gas enters this scrubber by way of a duct 361 it is scrubbed with dilute lime water obtained from tank 42, the lime water being introduced through a spray nozzle 65 at the top of a downtake tube 66. At the bottom of the scrubber, the gas is forced through a submerged bubbler cap 61, and as the gas temperature is now well below 90 F. both oil and water vapors are condensed. The lime water also removes H23 and some of the other acidic gases present, such as C02. The lime water may be very dilute, as water having a hydrogen ion concentration of pI-Is is efiective in removing 90% of the H28 in the gas, assuming of course that sufiicient lime water is supplied.

The gas produced from certain oils contains some organic compounds of high molecular weight in molecular suspension which are not removed by scrubbing the gas with water or aqueous solutions. To remove these gum-like compounds, the gas is passed from scrubber through a duct 451 into the double oil scrubber id. in this scrubber the gas is forced to bubble downwardly through a body of light oil in chamber 479, whence it enters bubbler cap 67, forming a spray which is carried with the gas down a tube 623 and into the second bubbler cap 69. The gas bubbles upwardly through the body of oil in the bottom of the scrubber 46, thereby separating the spray from the gas. In this way practically all of the organic compounds carried in suspension by the gas are left behind dissolved in the oil, which, as the process continues, rises in the scrubber and overflows through pipe 462 into the oil-separating tank 37. In this tank the flow of liquids is very slow, with the water being removed from the bottom by means of line 446, as already noted. The oils, all having a density less than that of Water, rise to the surface of the water in tank 37, and, by maintaining the Water level in the tank well above the Water outlet the oils accumulate in the upper half of the chamber, whence they are drawn off periodically through a line 59 controlled by a valve 590. The oil removed through line 59 is returned to the oil supply tank for reintroduction to the generator. The process provides for practically 100% conversion of oil to gas.

The clean gas, rising from the bottom of scrubber 46, flows by way of a pipe 463 into the receiver tank 3, whence it is delivered to the points of consumption under the control of valve 53.

From the preceding description it is apparent that the operation of the generator and gas cooling and purification units is practically automatic as long as the rates of flow of water and oil, as adjusted at the'start of the run, are

maintained. However, the amount of gas that can be usefully consumed by either industrial or domestic users varies, not only from day to day but also for different periods in each day, wherefore it is highly desirable to produce gas only as fast as it can he profitably or usefully consumed. Since the proportion of oil and Water injected into the generator may vary without atiecting the process, that is, as long as a certain minimum proportion of water is delivered, the rate of gas production may be varied by adjusting the oil injected. When the gas consumption for several hours is constant and can be anticipated, a rough adjustment of the rate of flow of water and oil can be made by means of the flow meters pro 8 vided, but such adjustment does not'provide for the small unavoidable variations in'the volume of'gas consumed in relation to the volume produced.

it is desirable that the gas be supplied at a constant gage pressure, which for most commercial uses varies from one-half lb. to two lbs. per square inch.

To meet this requirement, a particularly effective pressure-regulating electrical switch has been devised, the switch being shown attached to gas tank 3 in Fig. 1. A vertical section through the center of the switch is shown on larger scale in Fig. 5.

The switch 34 comprises a mercury manometer, including a thick-walled glass U-tube 74. The tube is of /2" internal diameter, and is 2 /2 long, measured from the inside of the bend in the U. One leg of the U-tube is longer than the other, and includes a 90 bend at its upper end, which is equipped with a rubber collar 75 sealed and clamped in an orifice formed in the side wall of tank 3, as indicated in Fig. 1. The tube is supported and protected by a steel guard 76, secured to the Wall of tank 3. The longer leg of the U is calibrated in centimeters and millimeters-from a line above the bend for a distance of 5 centimeters. Clean mercury is placed in the tube to the level indicated at 90 in Fig. 5, which is the level of the 25 mm. graduation on the wall of the tube.

At the top of the shorter leg of the U, a set of electric contacts 77 and $1 is provided. The contact 77 comprises a ring formed of copper or brass tubing having a diameter slightly larger than the outside diameter of the U-tube. The upper edge of the ring is swedged and ground to form a flat seat, and the body of the ring is slit longitudinally. A rubber sleeve '78 is cemented to the inner surface of the ring; an electric conductor wire 770 is soldered to the ring; and a clamp 79 secures the ring assembly in desired vertical position upon the shorter leg of the U- tube. A float 8i? formed of glass tubing of 10 mm. outside diameter, closed at its lower end, fits loosely within the open end of the shorter leg of the U-tnbe. The length of the float 80 is not less than 1%., and the otherwise open end of the float is necked-in and closed by means of a stopper $3 of electric insulating material.

The contact 81 comprises a ring of light gage copper tubing, having its upper end closed by means of copper disk 82 soldered to the edge of the ring. The contact member 81 is secured to the float by means of a screw 84 that passes through the end wall 82 into the body of the stopper 83. The screw 84- provides the terminal post for uniting an electrical conductor 810 to the contact member 31. The contact member 81 normally bears at its lower edge upon the seat formed on the upper edge of contact ring 77, as shown in Fig. 5. Positioned over the assembled contact members is a protecting hood 85 formed of insulating material, or of metal lined with insulating material. As long as the pressure in tank 3 remains below that desired, the float 8d remains stationary, with the copper rings '77 and 81 in contact, closing through conductors 810 and 776 that are connected to switc- 33 the electric energizing circuit of the oil pump motor 260. If there is a drop in quantity of gas consumed in service the pressure in tank 3 is increased, pushing the mercury level in the long arm of the U-tube downwardly and raising the mercury level under the float. The float rises with the mercury and breaks the circuit to the oil pump motor 266, thus interrupting the flow of oil until such time as more gas is consumed and the pressure in the tank 3 decreased. This control is well adapted to the process, since the generator continues to produce some gas for several minutes after the oil is shut off, and makes gas immediately when the flow of oil into the generator is reinstated. This lag, or the gradual decrease in the generation of gas after the oil has been shut off, increases the intervals between the stopping and the starting of the motor. It will be manifest that, by adjusting the vertical position at'which the contact assembly 77-85 is clamped on the shorter leg of the U-tube, the apparatus may be made automatically responsive to any selected delivery pressure.

The composition, specific gravity, and heating value of the gas produced vary somewhat according to the type of oil used, and the temperature at which the generator is operated. With a well-conditioned catalyst in the generator operating at a temperature of 1500 F., the gas will have a specific gravity of about 0.7, and a heating gas may be lowered to any value desired, while the specific gravity and the quantity of gas produced will be correspondingly increased, due to the formation of CO and dilution with N2. In general, the volume of gas produced from a given volume of oil varies from 150 cu.'ft. to 250 cu. ft. per gallon of oil, according to the type of oil used, and the heating value of the gas produced.

With certain oils that give high residues on distillation, such as No. 6 or Bunker C oil, it is advisable to inject a little air continuously through line 57, which flows upwardly from box 13, to prevent the formation of coke in the bottom of the generator. With oils which give little or no residue, it is necessary to introduce only enough air in box 13 to equal the gas pressure in the generator, and

this will prevent water and oil vapors from flowing through the body of the catalyst 6 into the box 13.

If vapors are permitted to enter box 13 they will condense, creating a partial vacuum that promotes a continuation of the undesired flow. 7

As already mentioned, the iron ore in the chamber acts as a catalyst to prevent the formation of carbon, and is largely self-regenerating, provided that an excess of steam (or a little air) is employed, and the temperature of the ore is maintained above 1300 F. in all parts of the chamber 5. On the other hand, if the temperature is increased above 1700 F. the oxide on the surface of the pieces of ore may be reduced to metallic iron which will cause the lumps to stick together, or sinter, particularly if too much air is added with a high residue oil. The latter situation is avoided by limiting the operating temperature in the combustion chamber. The temperature of the ore, which is a poor conductor of heat and is being continuously cooled by the injected oil, is held to a value between 1500 F. and 1550 F. at the top of the catalyst chamber, and to a still lower value below the point at which the oil is injected. At a temperature below 1400 F. the ore will not react with carbon, and the oil will not be cracked sufficiently to form fixed gases. Difficulty from these causes is avoided by forming the catalyst chamber with its walls flaring upwardly, as shown, and by superheating the injected stream to a temperature near that prevailing in the combustion chamber. In operating at the higher temperatures and using a high sulfur oil, the ore tends to absorb some sulfur, forming FeS on the surface of the lumps, but this sulfide is reconverted to oxide by reaction with the air or water at the high operating temperatures.

As a precaution against all factors that tend to decrease the effectiveness of the iron oxide catalyst, provision is made for moving the ore through the catalyst chamber from the storage chamber 12 at the top of the regenerator to the box 13 at the bottom. This movement is obtained by a pusher 70, which is moved back and forth through a distance of 2" to 3 by oscillating a lever 72. Each stroke of the lever pushes three to four lbs. of ore into the box 13. Eight to ten strokes of the pusher each hour is sufi'icient.

The air introduced through pipe 57 to the box 13 tends to keep the Vapors from flowing downwardly from the catalyst chamber, and serves to regenerate or reactivate the 10 catalyst delivered into the box 13, whereby such catalyst may be re-used.

In the use of fuel oils giving little or no residue, movement of the ore appears to be unnecessary, especially if catalyst-regenerating air is injected by way of box 13 to the bottom of chamber 5 from time to time.

Regarding the overall eificiency of the generator; the reactions taking place in the catalyst chamber are both exothermic and endothermic, with the latter slightly overbalancing the former. The chief source of heat absorption in the catalyst chamber is that required to vaporize the oil injected, which, added to the heat absorbed by the chemical reactions, amounts to about 600 B. t. u. per pound of oil injected. The other heat losses are the sensible heat in the gases formed and in the products of cornbustion that escape through the flue 73. In large installations the latter may be used to preheat the oil as it is pumped to the generator, and the loss from radiation may be reduced to a minimum by insulating the combustion chamber. Thus, the overall efiiciency, by which term is meant the tota'l'heating value of the oil used as compared with the total heating value of the gas delivered, ranges from about for the small generator described .herein to and higher for larger units.

It will be perceived that the method of my invention involves not only the physical and chemical changes known as cracking, and those changes known as pyrolysis, but also involves certain chemical reactions among the components of the carbonaceous liquid, the ore, and the 7 water and/or oxygen of the air used. Such carbonaceous liquids as fuel oils derived from petroleum are composed mainly of residues from distillation and cracking processes that are repeated until the residue will no longer yield a lighterhydrocarbon of value. When a mixture of such heat-stable liquids is injected into my catalyst chamber heated to a temperature above 1450" F. the initial action is that of vaporizing the oil. This physical change is instantly followed by a chemical action, in which the hydrocarbon molecules are first broken down by reaction with oxygen derived from the oxide catalyst. This reaction is primarily limited to the oxygen available on the surfaces of the catalyst mass, and it may be said that in some surface areas of the pieces forming catalyst mass the oxide is reduced from a higher to a lower oxide, with'possibly the formation of a slight amount of metal. With the decomposition of hydrocarbon molecules thus initiated, there immediately follows a cracking reaction, in which molecules of smaller molecular weights are formed with the usual deposition of carbon. This carbon is converted to CO by reaction with the oxygen supplied by the catalyst, or to CO and H2 by reaction with the water vapor or steam supplied. Finally, the hydrocarbons having molecular weights above ethane and butane undergo a pyrolysis or decomposition without deposition of carbon, and unsaturated hydrocarbons known as olefins are formed.

In the absence ofan oxidizing gas,'such as water vapor, the catalyst oxide would soon be reduced to the point where it becomesinactive, but with Water injected in the form of superheated steam as described, the lower oxide on the surfaces of the lumps is oxidized to a higher oxide (and such slight quantity of metal as exists is oxidized), and the water is reduced to H2. All of these reactions proceed to equilibrium, which depends upon the temperature and the proportion of water vapor or steam injected.

The catalyst will be understood to be formed of a substance which yields or promotes the release of oxygen for breaking down heat-stable hydrocarbons as described above. In the presence of heat and such an oxidizing gas as steam, the substance of the catalyst is at least partially converted or restored from a lower to a higher oxide.

Although hard hematite is preferred as the substance or material of which to form the catalyst, other oxides of metals having a valency of at least two, such as manganese dioxide, nickel oxide, and chromic, cobaltic, molybdic, and tungstic oxides, may serve. For example, I have produced gas using manganese dioxide as a catalyst, but I found the reduced oxide is a powder which either clogs the generator oris-carriedover with the gas, making an extra step necessary to'clean the gas of this dust. Likewise, the other oxides mentioned present certain difiiculties in operation, all-of which are avoided by the use of hematite. However, as those skilled in the chemical art will know, the difiicu'lties referred to may be overcome by reinforcing, pelletizing, or capsulating the catalytic substance within walls-or coatings of a suitably pervious substance.

By virtue-of the invention herein disclosed a clean fixed gaseous fuel, including at least one hydrocarbon gas, is produced. Thegas developed in the generator is not only cleansed of water and oil vapors in the scrubber 36, but

the gas is cooled below the temperature at which the hydrocarbon gas polymerizes or decomposes under the effect of heat alone. And as already described in detail the units 45 and 46 cleanse the generated gas of acidic and gum-like organic inclusions.

From the context of the foregoing specification oxydizing gas and gaseous oxydizing agent will be understood to cover water vapor or steam or air, or a mixture of water vapor or steam with air or oxygen.

Within the intent of the appended claims various modifications and variations in the apparatus described may be made within the skills of the experts in the art, without departing from the spirit of the-invention.

Notice is given of my co-pending divisional application Serial No. 161,559, filed May 12, 1950.

I claim:

1. Apparatus for converting a carbonaceous liquid into a combustible mixture of fixed gases, said apparatus comprising a combustion chamber, a catalyst chamber having heat-conducting walls in said combustion chamber, a catalyst in said chamber comprising a porous vertical column of particulate metal oxide forming a cracking zone positioned below a pyrolysis zone, the column of catalyst being of greater cross section in the region above the cracking zone than'it is in such zone, means for burning fuel in said combustion chamber for heating the catalyst in both of said zones, means'for injecting said carbonaceous liquid into the catalyst in said cracking zone, means for supplementing the transfer of heat from said combustion chamber to said cracking zone of said catalyst body, said supplemental heating means comprising a steam superheater in said combustion chamber and a device for the delivery of steam from said superheater into said cracking zone below the region where said carbonaceous liquid is injected, the steam and liquid in the presence of said heated catalyst in the cracking zone reacting to produce vapors and gases that flow to said pyrolysis zone, and a delivery line for leading the gases from the pyrolysis zone, said pyrolysis zone comprising a plurality of pyrolysis tubes including said catalyst and standing in communication between said catalyst chamber and said delivery line.

2. Apparatus for converting a carbonaceous liquid into a combustible mixture of fixed gases, said apparatus comprising a combustion'chamber, a catalyst chamber having upwardly divergent heat-conducting walls in said combustion chamber, a catalyst in said chamber comprising a porous vertical column of particulate metal oxide forming a cracking zone below a pyrolysis zone, the column of catalyst being of greater effective cross-sectional area above the cracking zone than below, means for burning fuel in said combustion chamber "of heating .the catalyst in both of said zones, means for injecting said carbonaceous liquid into the catalyst in said cracking zone, means for supplementing the transfer :of heat from said combustion chamber to said cracking zone of relatively smaller crosssectional area, said supplemental heating means comprising a steam superheater in said combustion chamber and a device for the delivery of superheated steam from said superheater into said cracking zone below the region where said carbonaceous liquid is injected, said steam and liquid in the presence of said heated catalyst in the cracking zone reacting to produce vapors and gases that flow to said pyrolysis zone, and a delivery line for leading the gases from the pyrolysis zone, said pyrolysis zone comprising a plurality of pyrolysis tubes including said catalyst and standing in communication between said catalyst chamber and said delivery line.

3. Apparatus for converting a carbonaceous liquid into a combustible mixture of fixed gases, said apparatus comprising a combustion chamber, a catalyst chamber having upwardly divergent heat-conducting walls in said combustion chamber, a catalyst in said chamber comprising a porous vertical column of particulate metal oxide forming a cracking zone below a pyrolysis zone, the column of catalyst being of greater efiective cross-sectional area above the cracking zone than below, means for burning fuel in said combustion chamber for heating the catalyst in both of said zones, means for injecting said carbonaceous liquid into the catalyst in said cracking zone, means for supplementing the transfer of heat from said combustion chamber to said cracking zone of relatively smaller crosssecticnal area, said supplemental heating means comprising a steam superheater and a device for the delivery of superheated steam from said superheater into said cracking zone below the region where said carbonaceous liquid is injected, said steam and liquid in the presence of said heated catalyst in the cracking zone reacting to produce vapors and gases that flow to said pyrolysis zone, and a delivery line for leading the gases from the pyrolysis zone, said pyrolysis zone comprising a plurality of pyrolysis tubes including said catalyst and standing in communication between said catalyst chamber and said delivery line.

References Cited in the file of this patent UNITED STATES PATENTS 862,508 Ralston Aug. 6, 1907 931,018 Amet Aug. 10, 1909 1,138,460 Derby May 4, 1915 1,902,004 Whitlock Mar. 21, 1933 1,915,363 Hanks et al. June 27, 1933 1,924,813 Sperr Aug. 29, 1933 2,028,326 Hanks et al Jan. 21, 1936 2,309,540 Rollman et al. Jan. 26, 1943 2,336,466 Chatterton et al Dec. 14, 1943 2,386,778 Claffey Oct. 16, 1945 2,397,432 Records Mar. 26, 1946 2,493,784 Strader Jan. 10, 1950 2,524,840 Shapleigh Oct. 10, 1950 2,525,276 Shapleigh Oct. 10, 1950 2,526,521 Voorhies Oct. 17, 1950 2,543,005 Evans Feb. 27, 1951 FOREIGN PATENTS 255,423 Great Britain Aug. 19, 1927

Claims

1. APPARATUS FOR CONVERTING A CARBONACEOUS LIQUID INTO A COMBUSTIBLE MIXTURE OF FIXED GASES, SAID APPARATUS COMPRISING A COMBUSTION CHAMBER, A CATALYST CHAMBER HAVING HEAT-CONDUCTING WALLS IN SAID COMBUSTION CHAMBER, A CATALYST IN SAID CHAMBER COMPRISING A POROUS VERTICAL COLUMN OF PARTICULATE METAL OXIDE FORMING A CRACKING ZONE POSITIONED BELOW A PYROLYSIS ZONE, THE COLUMN OF CATALYST BEING OF GREATER CROSS-SECTION IN THE REGION ABOVE THE CRACKING ZONE THAN IT IS IN THE SUCH ZONE, MEANS FOR BURNING FUEL IN SAID COMBUSTION CHAMBER FOR HEATING THE CATALYST IN BOTH OF SAID ZONES, MEANS FOR INJECTING SAID CARBONACEOUS LIQUID INTO THE CATALYST IN SAID CRACKING ZONE, MEANS FOR SUPPLEMENTING THE TRANSFER OF HEAT FROM SAID COMBUSTION CHAMBER TO SAID CRACKING ZONE OF SAID CATALYST BODY, SAID SUPPLEMENTAL HEATING MEANS COMPRISING A STEAM SUPERHEATER IN SAID COMBUSTION CHAMBER AND A DEVICE FOR THE DELIVERY OF STEAM FROM SAID SUPERHEATER INTO SAID CRACKING ZONE BELOW THE REGION WHERE SAID CARBONACEOUS LIQUID IS INJECTED, THE STEAM AND LIQUID IN THE PRESENCE OF SAID HEATED CATALYST IN THE CRACKING ZONE REACTING TO PRODUCE VAPORS AND GASES THAT FLOW TO SAID PYROLYSIS ZONE, AND A DELIVERY LINE FOR LEADING THE GASES FROM THE PYROLYSIS ZONE, SAID PYROLYSIS ZONE COMPRISING A PLURALITY OF PYROLYSIS TUBES INCLUDING SAID CATALYST AND STANDING IN COMMUNICATION BETWEEN SAID CATALYST CHAMBER AND SAID DELIVERY LINE.