US2759806A

US2759806A - Method of making a fuel gas

Info

Publication number: US2759806A
Application number: US337078A
Authority: US
Inventors: Elmore S Pettyjohn; Henry R Linden
Original assignee: Institute of Gas Technology
Current assignee: Gas Technology Institute
Priority date: 1953-02-16
Filing date: 1953-02-16
Publication date: 1956-08-21
Anticipated expiration: 1973-08-21

Description

g- 21, 1956 E. s. PETTYJCHN ET AL 2,759,806

METHOD OF MAKING A FUEL GAS Filed Feb. 16, 1953 NATURAL STEAM GAS LIQUID V. V FURNACE TUBE- NICKEL CATALYST co H I FUEL GAS a VAPOR II Ir IRON CATALYST co H V I CONDENSER --SCRUBBER FUEL TARS C a GAS f wezyz'bzzf 13727202? JfPezZg/ofzzz Fizzy ("y ZlzWdQZZ United States Patent 2,759,806 Patented Aug. 21, 1956 amounts ranging from 20 to 60 or more s. c. f./ gallon of starting material.

When natural gas liquids are cracked under the conditions described hereinabove, carbon is formed in such METHOD OF MAKING AFUEL GAS 5 small amounts (less than 2% of the starting material) that the cracking may conveniently be carried out con- Elmore Petty-ohm Evimston and X Linden tinuously (for periods such as 24 hours) in a suitable $23 33 i g 'fi g agg gl ig fifi f g furnace tube. Further, the yield of fuel gas in increased g more than 20% over that obtained in conventional crack- Application February 16', 195 Serial N 337,078 ing methods, and the fuel gas is completely or absolutely 5 Claims. (CL 48 197) interchangeable with natural gas in gas burners adjusted for natural gas. For instance, in the case of propane, 97% of the starting material is gasified to form a fuel gas of 1031 B. t. u./s. c. f. diluent free heating value and a specific gravity of 0.55 (:air=1.000). In the case of This invention relates to a thermal cracking method 12 1b. R, V, P. natural gasoline, 77% of the starting for converting natural gas liquids and petroleum oils into i l i ifi d t form a f l gas f 971 fuel gases. B. t. u./s. c. f. diluent free heating value and a specific An important Object of the present invention is to gravity of 0.53 (air=1.000). Both of these two fuel Provide a method of the nature indicated capable 0f gases are absolutely interchangeable with natural gas. converting or at least a much greater Portion than The character of the liquid by-products (tars and light has heretofore been possible, of the cracked natural gas 11 i i ll h same as that f the liquid liquids Petroleum Oils into fuel gas absolutely intefproducts of conventional thermal cracking of the same Changeable with natural gas when burned in burner starting materials, although the amounts of such liquid adjusted for natural gas. by-products formed are greatly reduced, as compared Other and further objects and features of the present ith nv tio l processes invention Will become pp from the following The procedural steps of carrying out the methods of SCIJ'PtiOH and pp claims as illustrated y the {116- the present invention need not differ from conventional chmpahyihg fiOWsheet Showing, y y of an p cracking methods, apart from the steps required to maina process according to the present invention. tain the above disclosed conditions. Thus, the starting The starting materials employed in the method of material and the hydrogen are passed through a heated this invention include the natural gas liquids such as prostainless steel tube. The resulting oil gas is passed pane, butane and natural gasoline. Distillate petroleum through conventional cooling and condensing equipment oils may also be used. to remove and recover any tar and light oils formed.

According to the present invention, the starting mate- Any remaining tar fog may next be removed with an elecrial (in vapor form) is thermally cracked (in absence of trostatic precipitator. catalyst) under conditions disclosed as follows: The tem- By way of illustrative example, the conditions and perature ranges from 1400 to 1600 F., and preferably results of a number of cracking runs are tabulated hereis kept at from 1450 to 1550" F. The contact time inbelow. These runs were carried out using no hydro ranges from 2 to 10 seconds, and preferably is kept at gen, as well as with various amounts of hydrogen, to from 4 to 5 seconds. The pressure ranges from 2.5 to afford a comparison. Runs Nos. 225, 384, 385, 387 and 7 or 8 or more atmospheres absolute, and preferably is 388 were carried out with 12 lb. Reid vapor pressure maintained at from 3 to 5 atmospheres absolute. The natural gasoline. Runs Nos. 243 and 389 were carried cracking is carried out in the presence of hydrogen in out with propane.

TABLE I Operating and burner test data for pressure hydrogasification of natural gas liquids Run No 225 384 385 387 388 243 389 Operating Conditions: 20. 49 47. 57. 94 0 40. 83

Carrier Gas H2, S. O. FJGal. Hydrocarbon 0 27. 17 '5. 12 2. 96 5. 10 3.05 5. 01 Total Pressure, Atm 3. 11 3. 05 '60. 9 29.1 60. 5 30. 3 59. 2 Gauge Pressure, P. S. l 31. 4 30. 4 1, 470 1,480 l, 480 l, 500 1, 470 Cracking Temp., "F 1, 500 1, 420 92 4. 95 5.01 4. 23 4. 42 Residence Time, Sees 4. 91 4. 72 Operating results:

B. t. u. Recovery, M B. t. u./Gal- 74. 70 86. 48 82. 70 89.68 87. 32 76. 18 S7. 47 Oil Gas Yield) S. O. FJGal. 70. 2 71. 22 67. 69 t 75. 36 81. 86 73.82 69. 77 H2 Absorbed, S. C. FJGal. 13.83 6. 39 5. 76 18. 83 30.80 13. 36 13.13 Tar yield, Wt. percent. Z 39. 6 22.6 27. 6 19. 8 20. 3 2 22.2 0 Light 011 Yield, Wt percent 1, 549 1 0. 420 1.691 0.417 0.599 Carbon Yield, Wt. =percent 2. 47 1. 0 1. 1 1. ;2 1. 2 0. 1. 9 Material Balance, percent 99. 7 98. 7 97.0 99. 2 98. 2 102.9 99. 1

Gas Properties t Gas Composition, Inert-Free, Vol. prcenti H: 20.1 28.4 57.4 43. 5 5. 2 12. 0 0. 1 1. 4 0.1 0. 1 0. 2 14.6 4. 7 2. 7 2. 7 16.0 11.8 1. 2 0.7 0.9 0. 4 0. 9 1.6 0.1 0.2 02 0.1 0.2 0.1 0.2 Pentenes TABLE I.Continued passed over an iron catalyst for the Water gas shift reaction:

Next, to raise the hydrogen concentration, the carbon dioxide-hydrogen gas mixture is scrubbed to remove the 70 carbon dioxide, by any suitable conventional method.

Reference is made to the accompanying flowsheet for the combined cracking--hydrogen generating steps which may be carried out continuously as one form of the present invention. This flowsheet is believed self-explanatory. Each of the above indicated reactions being known per se, a person skilled in the art will know how to carry For The method of this invention, when applied to natural gas liquids as a continuous furnace tube operation, may include a hydrogen generating step in which a part of 65 CnI Im+I1H20 nCO+ (n+m/2)H2 The product gas is then cooled to 700 to 1000 F. by water injection and the resultant steam-gas mixture the feed stream is utilized as a source of hydrogen.

this purpose, a part of the hydrocarbon feed stream is passed over a nickel catalyst with an amount of steam and at a temperature sufiicient to bring nearly to completion the reaction:

(with such added steam as may be required to force the 75 next following reaction to go nearly to completion) is out the combined process in the light of the disclosure given herein.

In general, about to of the feed stream may be converted into hydrogen, as by the method disclosed above. About 10% will usually be satisfactory. The amounts of hydrogen thus obtainable are exemplified as follows: One gallon of propane is capable of yielding 40 s. c. f. hydrogen, and one gallon of 12 lb. R. V. P. natural gasoline is capable of yielding 52 s. c. f. hydrogen.

Thus, according to the present invention, natural gas liquids and petroleum oils may be converted into fuel gases with a fuel gas yield higher than has heretofore been possible and with 20% less of liquid byproducts, as compared with conventional oil gas processes. Further, the fuel gas obtained is absolutely interchangeable with natural gas. Reference -is made to our copending application Serial Number 270,955 (filed February 11, 1952 and entitled Fuel Gas Interchangeable with Natural Gas and Method of Preparing the Same), now Patent No. 2,707,675, for a discussion of the interchangeability of fuel gases with each other.

The above noted features of the method of the present invention are of notable value. The demand for a fuel gas absolutely interchangeable with natural gas arises from the occurrence of a few days of peak gas requirement in the areas supplied with natural gas for domestic and/or industrial heating. On such days, the gas requirement rises above the delivery capacity of the pipe lines and must be met from other sources. The method of the present invention can supply large volumes of fuel gas interchangeable with natural gas without at the same time producing large amounts of liquid by-products, and the apparatus required to practice our methods can be relatively simple and inexpensive, which is important in view of the few days to which operation is confined.

Reference is made to our copending applications Serial Numbers 270,955 (filed February 11, 1952, and entitled Method of Making a Fuel Gas Interchangeable with Natural Gas, now Patent No. 2,707,675), 275,952 (filed March 11, 1952, and entitled Method of Making Oil Gas Interchangeable with Natural Gas), 287,122 (filed May 10, 1952 and entitled Method of Making Oil Gas Interchangeable with Natural Gas, now Patent No. 2,721,123) and 311,256 (filed September 24, 1952 and entitled Thermal Method of Making Oil Gas, now Patent No. 2,721,- 122). These applications disclose cracking methods for making oil gas in which the fuel gas yield can be increased by adding hydrogen in amounts of from 20 to 60 s. c. f./ gallon of liquid feed when the feed is cracked.

Many details may be varied without departing from the principles of this invention. Therefore, we do not intend to limit the scope of this patent otherwise than necessitated by the scope of the appended claims.

We claim:

1. A thermal cracking method (in absence of catalyst) of converting a hydrocarbon taken from the group consisting of propane, butane and natural gasoline into a fuel gas interchangeable with natural gas which comprises passing said hydrocarbon in vapor form through a heated reactor at a temperature from 1400 to 1600 F., a contact time of from 2 to 10 seconds and a pressure of at least 2.5 atmospheres absolute while simultaneously passing hydrogen from an external source through said reactor at a rate of from 20 to 60 s. c. f. per gallon of said hydrocarbon, and thereafter separating the fuel gas then formed from condensable by-products.

2. A method according to claim 1 comprising, as additional steps, converting a part of said hydrocarbon into hydrogen by initially reacting said part with steam to form a mixture of carbon monoxide and hydrogen, thereafter reacting said carbon monoxide with additional steam to form carbon dioxide and additional hydrogen, and thereafter separating said hydrogen from said carbon dioxide, the separated hydrogen being fed into said heated reactor as specified in claim 1.

3. A thermal cracking method (in absence of catalyst) of converting a hydrocarbon taken from the group consisting of propane, butane and natural gasoline into a fuel gas interchangeable with natural gas which comprises passing said hydrocarbon in vapor form through a heated reactor at a temperature of from 1450 to 1550 F., a contact time of from 2 to 10 seconds and a pressure of at least 2.5-8 atmospheres absolute while simultaneously passing hydrogen from an extended source through said reactor at a rate of from 20 to 60 s. c. f. per gallon of said hydrocarbon, and thereafter separating the fuel gas then formed from condensable byproducts.

4. A method according to claim 3 comprising, as additional steps, converting a part of said hydrocarbon into hydrogen by initially reacting said part with steam to form a mixture of carbon monoxide and hydrogen, there- :after reacting said carbon monoxide with additional steam to form carbon dioxide and additional hydrogen, and thereafter separating said hydrogen from said carbon dioxide, the separated hydrogen being fed into said heated reactor as specified in claim 3.

5. A thermal cracking method (in absence of catalyst) of converting a hydrocarbon taken from the class consisting of propane, butane and natural gasoline which comprises passing said hydrocarbon through a heated reactor at a temperature of 1400-1600 F., a contact time of 2 to 10 seconds and a pressure of at least 2 /2 atmospheres absolute, while simultaneously passing hydrogen from an external source through said reactor at a rate of at least 20 s. c. f. per gallon of hydrocarbon, and thereafter separating the fuel gas then formed from condensable by-products.

References Cited in the file of this patent UNITED STATES PATENTS 1,884,269 Russell Oct. 25, 1932 2,072,801 Gary Mar. 2, 1937 2,283,643 Nagel May 19, 1942 2,340,815 Lidov Feb. 1, 1944 2,450,753 Guyer Oct. 5, 1948 2,605,176 Pearson July 29, 1952 2,608,478 Pollock Aug. 26, 1952 FOREIGN PATENTS 531,430 Germany Aug. 10, 1931 481,835 Great Britain Mar. 18, 1938

Claims

1. A THERMAL CRACKING METHOD (IN ABSENCE OF CATALYST) OF CONVERTING A HYDROCARBON TAKEN FROM THE GROUP CONSISTING OF PROPANE, BUTANE AND NATURAL GASOLINE INTO A FUEL GAS INTERCHANGEABLE WITH NATURAL GAS WHICH COMPRISES PASSING SAID HYDROCARBON IN VAPOR FORM THROUGH A HEATED REACTOR AT A TEMPERTURE FROM 1400* TO 1600* F.8 A CONTACT TIME OF FROM 2 TO 10 SECONDS AND A PRESSURE OF AT LEAST 2.5 ATMOSPHERES ABSOLUTE WHILE SIMULTANEOUSLY PASSING HYDROGEN FROM AN EXTERNAL SOURCE THROUGH SAID REACTOR AT A RATE OF FROM 20 TO 60 S. C. F. PER GALLON OF SAID HYDROCARBON, AND THEREAFTER SEPARATING THE FUEL GAS THEN FORMED FROM CONDENSABLE BY-PRODUCTS.