US2885343A

US2885343A - Conversion of hydrocarbons

Info

Publication number: US2885343A
Application number: US365308A
Authority: US
Inventors: Herman N Woebcke
Original assignee: Hydrocarbon Research Inc
Current assignee: Hydrocarbon Research Inc
Priority date: 1953-07-01
Filing date: 1953-07-01
Publication date: 1959-05-05
Anticipated expiration: 1976-05-05

Description

Filed July 1, 1953 INVENTOR. HERMAN N. WOEBCKE AGENT oxygen is reacted with carbonaceous matter depo United States Patent 2,885,343 CONVERSION OF HYDROCARBONS Herman N. Woebcke, Emerson, NJ., assignorto' Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Application July 1, 1953, Serial No. 365,308

7 Claims. (Cl. 208-59) volve the cracking of the higher boiling hydrocarbons into hydrocarbons boiling in the gasoline range. However, available cracking processes, which. are effective in the treatment of ordinary heavy oil fractions, are of limited effectiveness in producing gasoline of commercially acceptable quality from low grade, heavy hydrocarbon oils, such as sour crudes,. petroleum residues, shale oil, coal tar and the like, which have a high content of sulfur and/or nitrogen and/or metal compounds.

Recently, however, a process has been developed which can efficiently convert crudes of high Ramsbottom carbon residue into economic yields of high octane gasoline. Generally speaking, this process involves conversion of hydrocarbon oil in the presence of a hydrogen-containing atmosphere. Notable modifications of this process are described in Keith Patent No. 2,606,862, issued August 12, 1952, and the patent application of. Finneran et .al., Serial No. 299,114, filed July 16, 1952. In this process, the regeneration of particulate contact material, on which carbonaceous matter has been deposited by the hydrocarbons undergoing. conversion, is carried out with oxygen and steam -to produce the hydrogen-containing atmosphere required for the hydrocarbon conversion. However, when the charge stock has a high carbon residue, say generally above 5% by Weight of carbon by the terial yields more hydrogen-containing gas than is necessary in the conversion of the hydrocarbons with the result that the converted hydrocarbons are unduly diluted by the hydrogen-containing gas and this necessitates a-large Additional objects and advantages will be apparent from the description which follows.

In accordance with the invention, particulate contact material or carrier is passed through a cracking, cycle comprising a primary hydrocarbon conversion or cracking zone, a secondary cracking zone, a methanizationzone and a regeneration zone; in the regeneration zone, a

regenerating gas consisting predominantly of: steam",

on the carrier by the hydrocarbons undergoing con Ramsbottom test, the regeneration of the contact marecovery plant for separating the converted hydrocarbons methanization zone.

sion to provide a hydrogen-containing regeneration product gas which flows through the methanization zone and then only in part through the conversion zones.

The hydrocarbon oil, preferably preheated, is fed into the primary cracking zone where the regeneration product gas provides a hydrogen partial pressure of 35 to 200 psi. (pounds per square inch), preferably to psi. During the hydrocarbon conversion, heavy hydrocarbons and carbon are deposited on the carrier particles. Carrier particles withdrawn from the primary cracking zone are passed downwardly through the secondary cracking zone countercurrent by hydrogen-containing regeneration product gas. At least the bulk of the heavy hydrocarbon portion of the deposit on the carrier particles is volatilized in the secondary cracking zone. Thence, the carrier passes downwardly through the methanization zone in which the hydrogen-containing regeneration product gas reacts with a portion of the residual carbonaceous deposit on the carrier to form methane and minor proportions of other gaseous hydrocarbons. From the methanization zone, the carrier passes into the regeneration zone wherein the remaining carbon on the carrier is reacted with steam and oxygen at a temperature in the range of 1600 to 2500 F., preferably 1700 to 2000 F., to produce the regeneration product gas containing hydrogen, carbon monoxide and dioxide and steam. The thus regenerated carrier particles are returned to the primary cracking zone to complete the cracking cycle by suspension in a gas stream derived from the process and containing a major proportion of hydrogen, usually in excess of 60% by volume. v

From the gasiform efiluent of the primary cracking zone, a good yield of high octane gasoline is recovered, even when heavy crudes or residual oils which contain large quantities of sulfur, nitrogen and metal compounds are treated. Because the present invention limits the quantity of regeneration product gas that is admixed with the hydrocarbons, the separation and recovery ofthe converted hydrocarbons from the gasiform efiluent of the cracking process are materially facilitated.

In most cases, the gasoline produced by the foregoing process has a sulfur content Within commercially desirable limits and is in other respects an acceptable product. In those cases where, because of the excessively poor quality of the oil treated, the gasoline produced, although of much reduced sulfur content, still contains more sulfur than is desirable or has less than the desired stability characteristics, the sulfur content and the stability characteristics can be brought to acceptable values by known refining processes, e.g., catalytic treatment of the gasoline in the presence of hydrogen and at elevated temperature. Such a process is described in the copending application of Johnson et al., Serial No. 272,512, filed February 19, 1952, on which US. Patent 2,774,718 was granted December 18, 1956. q

The particulate carrier which is employed in the process of the invention is any solid heat-resistant material, such as sand, quartz, alumina, magnesia, zircon, beryl, bauxite or other like material, which will Withstand the desired regeneration conditions including a temperature above 1600 F. without physically disintegrating or i The entire reaction system is generally maintained at a total pressure in the range of about 150 to 800 p.s.i.g. (pounds per square inch gage) preferably at 250 to 650 p.s.-i.g. Under these conditions, a hydrogen partial pressure of at least 35 p.s.i. (pounds per square inch), pref- .erably 75 to 150 psi, is readily maintained in the i The use of total pressures in the indicated range also provides a high oxygen partial pressure in the regeneration zone increasing the rate of regeneration and, consequently, decreasing the height of the regeneration zone.

Fluidization of the particulate carrier in the secondary cracking zone and in the methanization zone is preferably restrained in the sense that vertical movements of the fluidized particles are restricted to the extent that a temperature gradient is established along the vertical dimension of the zone. Such restrained fluidization is obtained by filling the zone with coarse packing bodies like Raschig ring and Berl saddles.

High-purity oxygen containing at least about 90% by volume of oxygen, preferably at least 95% by volume of oxygen, and obtained, for example, by air liquefaction and rectification, is used together with steam as the regenerating gas. Steam-to-oxygen volume ratios in the range of 1.5:1 to :1 are generally satisfactory for generating the required quantity of hydrogen. It is preferable, as a practical matter, to employ a steam-to-oxygen volume ratio of the order of 2:1 to 3:1 and thereby avoid a very high regeneration temperature.

The regeneration product gas contains hydrogen, carbon monoxide and carbon dioxide as well as excess steam introduced with the regenerating gas. This gas mixture provides the atmosphere for the hydrocarbon conversion reactions. At least 75%, preferably all, of the regeneration product gas is passed through the methanization zone. The regeneration product gas leaving the top of the methanization zone is divided into two streams, one flowing up through the secondary and primary cracking zones and the other by-passing these zones. In general, not more than about 40% of the regeneration product gas is passed through the secondary and primary cracking zones. The temperature of the primary cracking zone is maintained in the range of 850 to 1100 F., preferably 900 to 1050 F., by control of the temperature and quantity of carrier and gas transferred from the regeneration zone and by control of the temperature to which the hydrocarbon oil feed is preheated. The feed rate of hydrocarbon oil is desirably maintained at about 0.2 to 3.0, preferably 0.5 to 1.5, volumes of liquid oil per hour per volume of the primary cracking zone. The oil partial pressure, determined essentially by the rate of hydrocarbon oil feed and the volume of regeneration product gas may vary from about 5 to 100 p.s.i., preferably from to 50 p.s.i. The oil partial pressure is readily controlled in accordance with the invention since the volume of regeneration product gas passed into the primary cracking zone can be varied at will. It is a feature of the invention that the preferred range of conversion temperature is higher and the preferred range of oil partial pressure lower than are generally employed in thermal cracking processes, and as a consequence the gasoline which is produced is considerably higher in octane number than that produced in such processes, approximating 90 CFRR octane number without use of tetra-ethyl lead or other anti-knock additives.

The secondary cracking zone is operated at a temperature higher than the primary cracking zone. Preferably, the carrier passes downwardly through the secondary cracking zone with restrained fluidization. Devices of the type designated as packing or trays as are commonly utilized in fractionation and absorption towers are eifective in providing the type and degree of restrained fluidization which is desired. For example, the secondary cracking'zone may be filled with 2-inch Raschig rings. Obviously, undue restriction of the flow of carrier particles through the secondary cracking zone would adversely affeet the movement of carrier from one zone to another and interfere with the efficiency of the process. It has been found that the free horizontal area of the secondary cracking zone should, for best results, be 50 to 80% of the total horizontal area. This is particularly so when packing such as Raschig rings provides the desired restriction of flow. As a consequence of the type of flow of particulate carrier which is obtained, a temperature gradient is established in the secondary cracking zone with the top of this zone close to the temperature of the primary cracking zone and the bottom close to the temperature of the methanization zone. Heavy portions of the hydrocarbon oil feed which are not converted to volatile products in the primary cracking zone pass downwardly with the carrier into the secondary cracking zone and there are partially converted to volatile products with the benefit of increasing temperatures and contact with hot regeneration product gas. By the time that the carrier reaches the methanization zone, the carbonaceous residue on the carrier will be very low in hydrogen content; in general, the residue will have a hydrogen content not exceeding'that of the simplified chemical formula m- As the regeneration product gas flows up through the methanization zone, the steam and carbon monoxide present in the product gas undergo the water-gas shift reaction:

As the temperature is decreased, the equilibrium of the shift'reaction is favored toward the right, thereby producing nascent hydrogen. The nascent hydrogen thus generated comes into intimate contact with the carbonaceous residue on the particulate carrier and reacts therewith to produce methane and possibly small amounts of other gaseous hydrocarbons. The reaction is believed to'proceed along the lines indicated by the illustrative equation:

. l 2CH +2.4H- CH +CH Temperatures in excess of about 1200 F. appear to favor thisimethanization ofthe carbonaceous residue. Two important benefits of methanization are: more of the oil feed is converted to desirable gaseous and liquid products and less carbon is formed, requiring less regeneration capacity.

For a fuller understanding of the invention, reference is made to the accompanying schematic drawing showing a sectional elevation of a reactor adapted for carrying out the invention.

The reactor comprises an upright cylindrical vessel 10 provided with a flow-restricting baflle structure 11 at an intermediate level therein to permit the maintenance of different temperatures in the fluidized carrier particles on opposite sides of baffle structure 11 whichis shown as a perforated plate but, as known, may take the form of a grill, a screen or closely spaced baflle slats. Perforated plate 11 supports a bed of packing bodies 12, such as 2- inch Raschig rings. The portion of vessel 10 below plate 11 is regeneration zone 13 while the portion above plate 11 filled by packing bodies 12 is methanization zone 14. A tube 15 extends from the lower end portion to the upper portion of vessel 10, passing through plate 11 and the bed of rings 12. Extending downwardly from the upper end of vessel 10 is an inner cylindrical shell 16 which is disposed in concentric and overlapping relation with the upper end section of tube 15. The lowermost portion of shell 16 is provided with a perforated plate 17 which supports another bed 18 of Raschig rings. The feed oil is injected into shell 16 by way of pipe 19 and distributor ring 20 disposed above bed 18 in shell 16. The portion of shell 16 which is filled with fluidized carrier and which is above bed 18 is primary cracking zone 21 while bed 18 through which the carrier with absorbed heavy hydrocarbons moves downwardly provides the secondary cracking zone. The bulk of the absorbed hydrocarbons are stripped from the carrier particles passing down through bed 18 in contact with the upflowing regeneration product gas. The carrier particles leaving bed 18 through perforated plate 17 have a carbonaceous residue which is low in hydrogen content. These particles become admixed with the fluidized mass 22 above methanization zone 14. The carrier particles of fluidized mass 22, in turn, move downwardly through methanization zone 14 against the rising regeneration product gas from zone 13 with the result that a portion of the carbonaceous residue undergoes methanization. The carrier particles thence discharge through perforated plate 11 into regeneration zone 13 wherein a regenerating gas consisting predominantly of steam and high-purity oxygenintroduced by way of pipe 23 and distributer ring 24 reacts with the residual carbon on the particles, forming the hydrogen-rich regeneration product gas that is utilized in methanization zone 14 and then, in part, in both secondary conversion zone 18 and primary conversion zone 21.

The regenerated carrier is conveyed up through tube to primary conversion zone 21 by injecting through tubular valve stem 25 and perforated valve head 26 a hydrogen-enriched gaseous fraction obtained from the process. For instance, the hydrogen-enriched stream may be obtained by removing water vapor and carbon dioxide from the gaseous stream discharging from outlet 34. This hydrogen-enriched stream makes possible the maintenance of the desired hydrogen partial pressure in primary conversion zone 21 without undue dilution of the hydrocarbon products of conversion. It will be noted that the valve stem 25 is vertically adjustable so that the opening between valve head 26 and the lower extremity of tube 15 may be varied in relation to the desired rate of carrier circulation from regeneration zone 13 to primary cracking zone 21.

The hydrocarbon products of conversion together with the portion of the regeneration product gas which has passed up through bed 18 and the suspension gas used in tube 15 pass up through the gas dome 27, discharging therefrom by way of conduit 28. It is frequently desirable to quench this gaseous effluent by injecting a cooling fluid like water through pipe 29 into the inlet end of conduit 28.

The portion of the regeneration product gas which is in excess of that required to maintain the desired hydrogen partial pressure in the secondary and primary cracking zones flows up through the fluidized carrier mass 22 and discharges from vessel 10 as a separate gaseous stream after passing through cyclone separator 30. Where it is desired to increase the proportion of hydrogen over that of carbon monoxide in this gaseous stream, water and/ or steam may be introduced through pipe 31 and distributor ring 32 to promote the water-gas shift reaction. The portion of fluidized mass 22 above baffles 38 may be maintained at a lower temperature than that of the portion below bafiies 38 to promote further the production of hydrogen in the gas leaving vessel 10 through outlet 34.

Such hydrogen-enriched gas is well suited for introduction into tube 15 to convey regenerated carrier to primary cracking zone 21.

The diversion of the regeneration product gas leaving methanization zone 14 into two separate streams is efiected by suitable valves associated with

outlets

33 and 34. An advantageous arrangement involves a flow controller on outlet 34 and a pressure controller on outlet 33. In this manner, the control devices may be used to establish a fixed rate of withdrawal of gas through outlet 34 while maintaining a slightly lower pressure in shell 16 than that in vessel 10 above the fluidized mass 22; such operation ensures that gas will not flow back from primary conversion zone 21 into fluidized mass 22.

The hydrocarbon products recovered from the gaseous efliuent discharging through outlet 33 will generally include hydrocarbons boiling above the gasoline range. If desired, such heavy hydrocarbons may be recycled to the reactor and introduced by way of pipe 35 and nozzle 36 into the regenerated carrier flowing up through tube 15 into primary conversion zone 21. Losses of carrier by entrainment in the

gases leaving outlets

33 and 34 may be compensated by additions of carrier introduced by suspension in a suitable gas like steam through pipe 35 and nozzle 36.

As a specific example of the invention, Boscan (Venezuelan) crude oil having the following characteristics:

Gravity, degrees, API 10.5 Sulfur, weight percent 5 Carbon, Ramsbottom, weight percent 10.4

is treated in a reactor of the type shown in the drawing. Vessel 10 has an inside diameter of 16 feet andan over-all height of 120 feet. Primary cracking zone 21 has a main diameter of 12 feet and secondary cracking zone 18 has a diameter of 9.5 feet. The walls of vessel 10 contiguous to

zones

13 and 14 are internally lined with refractory insulation so that the effective diameter of

zones

13 and 14 is 12 feet. Transport tube 15 has a diameter of 5 feet. Bauxite is employed as the comminuted contact material providing the fluidized mass circulating through the various zones of the reactor. The bauxite is of fluidizable particle size, by weight being between 40. and 200 mesh. The total pressure in vessel 10 is maintained at 400 p.s.i.g.

The Boscan crude oil is introduced through pipe 19 at the rate of 20,000 barrels per day, and oxygen of by volume purity and steam are introduced through pipe 23 at the rate of 16.7 and 42 millions of standard cubic,

feet per day, respectively, to effect regeneration of the bauxite passing into regeneration zone 13 from the superposed zones.

To facilitate maintenance of the desired temperatures in the vessel 10, the oil being charged is preheated to a temperature of 400 F., the recycle stock to 850 F., the oxygen to 300 F. and the steam to 1000 F. A hydrogenrich gas fraction obtained from this operation is introduced through tubular valve stem 25 and perforated valve head 26 at the rate of 11 millions of standard cubic feet per day to transport the bauxite carrier from regeneration zone 13 to primary cracking zone 21 at the rate of 400 tons per hour. The temperature gradient through secondary cracking zone 18 ranges from the 950 F. temperature of primary cracking zone 21 to the 1250" F. temperature of the fluidized mass 22. .In turn, the temperature gradient through methanization zone 14 ranges from 1250" F. to the 1800 F. temperature of regeneration zone 13.

The regeneration product gas flowing upwardly through methanization zone 14 and providing therein a hydrogen partial pressure approximating p.s.i. is split into two streams on leaving methanization zone 14. About 75% of the regeneration product gas passes shell 16 .for withdrawal through outlet 34. The remainder of the regeneration product gas flows upwardly through the secondary and primary cracking zones 18 and 21, which together with the hydrogen-rich recycle gas employed to transport the bauxite in tube 15 provides a hydrogen partial pressure of 80 p.s.i. in zone 21. The regeneration product gas is quenched with 10,000 lbs. of saturated steam and 3,000 gallons of water introduced hourly through pipe 31 and distributor ring 32, thereby reducing the temperature of the gas and fluidized mass 22 above bafiles 38 to 800 F. and simultaneously promoting the water-gas shift reaction to increase the hydrogen content of the gas. The product gas is removed through outlet 34 at the rate of 58 millions of standard cubic feet per day, this containing 27% by volume of water vapor. The dried gas has the following volume percent composition.

Hydrogen 45.0 Carbon monoxide 11.2 Carbon dioxide 39.1 Methane 3.1

Nitrogen, etc.

'7v .The gasiform efiuent discharging from outlet 33 contains 36.7% byvolume of water vapor. By fractionation,

there are obtained from this eflluent the following quantities per-day of liquid products:

'Barrels Gasoline (C and higher hydrocarbons boiling up to 400 F.) 10,600 Light gas oil (boiling 400 to 750 F.) 13,000 Heavy gas oil (boiling above 750 F.) 5,200

The light gas oil is recycled "to vessel through pipe 35 to maintain the high gasoline yield. The gasoline fraction hasa CFRR octane number of 88 and a sulfur content of 1.5% by weight. The effluent also contains 23 millions of standard cubic feet of non-condensable gases including about by volume of hydrogen.

In view of the various modifications of the invention which will occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit or scope thereof, only such limitations should be imposed as are indicated by the appended claims.

What is claimed is:'

1. The process of converting a heavy hydrocarbon oil of high Ramsbottom carbon residue which comprises contacting said hydrocarbon oil with a particulate carrier in a cracking zone maintained at a temperature below about 1100" F. while maintaining therein a hydrogen partial pressure of at least p.s.i. to convert said hydrocarbon oil to lower boiling hydrocarbons with simultaneous deposition of carbonaceous matter on said carrier, passing carrier removed from said cracking zone through a methanization zone maintained at a temperature above about 1200 F. to convert part of said carbonaceous matter to normally gaseous hydrocarbons, contacting carrier removed from said methanization zone in a reg en eration zone maintained at a temperature above about 1600 F. with steam and high-purity oxygen to form a regeneration product gas containing hydrogen, flowing substantially all of said regeneration product gas into said methanization zone to provide therein a hydrogen partial pressure of at least 35 p.s.i., and flowing not more than a minor portion of the gaseous effluent from said methanization zone through said cracking zone.

2. The process of claim 1 wherein at least part of the major portion of said gaseous efiluent not flowing through said cracking zone is enriched relative to hydrogen content and the hydrogen-enriched part is introduced into said cracking zone.

3. The process of claim 2 wherein regenerated carrier is returned to said cracking zone by suspension in said hydrogen-enriched part.

.. 4. The process of converting a heavy hydrocarbon oil of high Ramsbottom carbon residue which comprises co nverlting said hydrocarbon oil in the presence of hydrogen and a particulate carrier in a conversion zone maintained at a temperature in the range of about 850 to 1100" F., passing carrier removed from said conversion zone through a methanization zone to convert to methane part of the carbonaceous matter deposited on said carrier during the conversion of said hydrocarbon oil, said carrier being exposed to increasing temperatures above about 1200 F. during passage through said methanization zone, contacting carrier removed from said' methanization zone in a regeneration zone maintained at a temperature above about 1600" F. with steam and high-purity oxygen to form a regeneration product gas containing hydrogen, flowing substantially all of said regeneration product gas into said methanization zone to provide therein a hydrogen partial pressure of at least 35 p.s.i., passing not more than 40% by volume of the gaseous eflluent from said methaniza tion zone into said conversion zone, enriching at least part of the remainder of said gaseous eflluent relative to hydrogen content, and introducing at least some of the hydrogen-enriched part of said gaseous effluent into said conversion zone to maintain therein a hydrogen partial pressure of at least p.s.i.

5. The process of claim 4 wherein enrichment of part of said gaseous effluent relative to hydrogen content is efiected by removing water vapor and carbon dioxide from said par-t. v I

6. The process of claim 4 wherein enrichment of part of said gaseous efiluent relative to hydrogen content is effected by subjecting said part to the water-gas shift reaction under conditions favoring the production of hydrogen.

7. The process of claim 4 wherein at least some of the hydrogen-enriched part of said gaseous efiluent conveys regenerated carrier to said conversion zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,970,248 Pier et al. Aug. 14, 1934 2,362,270 Hemminger Nov. 7, 1944 2,448,549 I Reed et al. Sept. 7, 1948 2,450,753 Guyer Oct. 5, 1948 2,533,026 Mattheson Dec. 5, 1950 2,557,680 Odell June 19, 1951 2,738,307 Beckerberger Mar. 13, 1956

Claims

1. THE PROCESS OF CONVERTING A HEAVY HYDROCARBON OIL OF HIGH RAMSBOTTOM CARBON RESIDUE WHICH COMPRISES CONTACTING SAID HYDROCARBON OIL WITH A PARTICULATE CARRIER IN A CRACKING ZONE MAINTAINED AT A TEMPERATURE BELOW ABOUT 1100*F. WHILE MAINTAINING THEREIN A HYDROGEN PARTIAL PRESSURE OF AT LEAST 35 P.S.I. TO CONVERT SAID HYDROCARBON OIL TO LOWER BOILING HYDROCARBONS WITH SIMULTANEOUS DEPOSITION OF CARBONACEOUS MATTER ON SAID CARRIER, PASSING CARRIER REMOVED FROM SAID CRACKING ZONE THROUGH A METHANIZATION ZONE MAINTAINED AT A TEMPERATURE ABOVE ABOUT 1200*F. TO CONVERT PART OF SAID CARBONACEOUS MATTER TO NORMALLY GASEOUS HYFROCARBONS, CONTACTING CARRIER REMOVED FROM SAID METHANIZATION ZONE IN A REGENERATION ZONE MAINTAINED AT A TEMPERATURE ABOVE ABOUT 1600*F. WITH STEAM AND HIGH-PURITY OXYGEN TO FORM A REGENERATIOIN PRODUCT GAS CONTAINING HYDROGEN, FLOWING SUBSTANTIALLY ALL OF SAID REGENERATION PRODUCT GAS INTO SAID METHANIZATION ZONE TO PROVIDE THEREIN A HYDROGEN PARTIAL PRESSURE OF AT LEAST 35 P.S.I., AND FLOWING NOT MORE THAN A MINOR PORTION OF THE GASEOUS EFFLUENT FROM SAID METHANIZATION ZONE THROUGH SAID CRACKING ZONE.