US3459655A

US3459655A - Production of coke

Info

Publication number: US3459655A
Application number: US543956A
Authority: US
Inventors: Charles Newton Kimberlin Jr; Henry George Ellert; Morey E Oldweiler
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1966-04-20
Filing date: 1966-04-20
Publication date: 1969-08-05
Anticipated expiration: 1986-08-05
Also published as: DE1645838A1; BE697290A; NO123581B; GR33609B; GB1156456A; CH492772A; ES339493A1; SE335400B; FR1552807A; NL6705493A; AT285531B

Description

Aug. 5, 1969 COKE CIRCULATION LOOPS FOR HEATING LOW TEMPERATURE REACTOR PRODUCTION OF COKE Filed April 20, 1966 HIGH TEMPERATURE REACTOR 27 PRODUCT FLUIDIZING I GAS INLET REACTOR AUXILIARY '/54 HEATER V FLUIDIZING 26 GAS INLET 34 FEED HYDROCARBON INLET LOW TEMPERATURE C. N. KIMBERLIN, JR. H. G. ELLERT M. E. OLDWEILER INVENTORS IQM a. 9mm

PATENT ATTORNEY U.S. Cl. 208-53 12 Claims ABSTRACT OF THE DISCLOSURE The invention described herein relates to a. highly flexible endothermic process for forming gaseous and carbonaceous products by cracking hydrocarbons by contact with hot fluidized particulate coke solids contained in separate communicating reaction zones at different elevated temperatures. Heat for the total system is supplied by circulating coke solids particles, in dilute solids phase, between the high temperature reaction zone and an auxiliary heating zone, to heat the coke solids particles by direct contact with the combustion products of fuel and oxygen. Heat for the low temperature reaction zone is supplied by circulation of the coke solids particles between the high temperature reaction zone and the low temperature reaction zone. Heat economies are obtained by withdrawal of the coke solids particles directly from the low temperature reaction zone. Coke is produced, and carbon-black can be co-produced, if desired. A unique coke product can be obtained by co-production of coke and carbon black, and by incorporation of the latter within the coke particles. By contact between the coke and a hydrocarbon-carbon black containing slurry within the low temperature zone, the carbon black is coated upon the coke particles, and by circulation of the product between the low temperature zone and the high temperature zone both the coke and carbon black are converted into a unique form of calcined coke.

This invention relates to an improved process combination for pyrolysis, or thermal cracking, of high molecuiar weight hydrocarbon and residual feeds by contact thereof with fluidized beds of hot carbonaceous solids to produce coke and a reducing gas consisting essentially of hydrogen. In particular, it relates to such combination which employs a plurality of conversion or reaction zones, each containing beds of fluidized coke solids at different elevated temperatures. It also relates to such process which can be used for the co-production of carbon black, and for the formation of a novel coke product.

The new and novel coke product of this invention is suitable for use in the preparation of coke electrodes, especially suitable for use in cells of the type for producing aluminum. In the formation of such electrodes, some of the coke product is formed into aggregates, is mixed with binder and other materials, calcined, and agglomerated or compacted into a carbonaceous mass of desired shape, and prebaked prior to use, if desired.

Thermal coking techniques are known in the prior art. In the more conventional low temperature thermal coking, a bed of particulate fluidized coke solids is maintained at temperatures ranging generally from about 900 F. to about 1400 F., and the hot coke particles are contacted by preheated hydrocarbonaceous feeds which are cracked to deposit coke on the particulate solids and to produce moderate quantities of lower molecular weight or lower boiling materials. Thus, topped crude oils, viscous hydrocarbon oils, and pitch or residua of low API gravity are contacted with hot solids coke particles to produce lower molecular weight hydrocarbon gases, both States atent O saturated and unsaturated. Exemplary of such compounds are methane, ethane, ethylene, butene, and the like, and other relatively low boiling products falling within the motor fuel boiling range. In the cracking reactions, there results some deposition of coke upon the surfaces of the hot solids coke particles.

Processes for coking and gasification of hydrocarbons at higher temperatures to produce reducing gas mixtures consisting essentially of hydrogen or hydrogen and carbon monoxide, as well as residual coke, are also known. These processes, termed high temperature coking processes, are invariably conducted at temperatures ranging generally above about 1800 F., and generally are conducted at temperatures ranging from about 1800 F. to about 3000 F. A residua or pitch is subjected to pyrolysis in the presence of sufficient oxygen or steam so that the cracked products are oxidized. Though the mechanism is not certain, it is believed that carbon dioxide and water are produced, these in turn reacting with carbon to produce carbon monoxide and hydrogen. In any event, the gasification reactions virtually eliminate the formation of any substantial amounts of low molecular weight hydrocarbons but produce a variety of other products, e.g., town gas, synthesis gas, hydro gas, reducing gas, and the like. There is then a considerable difference between the two types of process, a major cause for which relates to the temperature at which the different coking reactions are conducted. The difference relates not only to the different gases evolved from the two types of process, but also as to the type of coke that is produced.

In both types of processes, there are similarities between the steps employed. In each a fluidized bed of particulate hot coke is provided within a primary reaction vessel, or reaction zone, and the hydrocarbon feedstock is sprayed directly into the bed through a plurality of nozzles while steam or other extraneous gas, or both, may be injected into the bottom of the reactor to fluidize the coke solids particles. The hydrocarbon feedstock contacts and covers the coke particles, immediately cracking and vaporizing to leave a solid residue upon the external surfaces of the particles.

A major problem in each type of process involves that of supplying heat to the reactions. Both are endothermic. To accomplish this end, auxiliary burners or transfer line heaters are generally employed in combination with the primary reaction vessel. The particulate coke solids, generally in fluidized phase, are circulated between the heater and bed of the primary reaction vessel, and the coke is heated and thence retransferred or recycled to the bed of the reactor to impart heat for continuation of the coking reactions. The heat is generally supplied by burning oxygen or an oxygen-containing gas (air) and a hydrocarbon fuel in the transfer line heater through which the coke is circulated. The combusting gas contacts and imparts heat to the coke solids particles, elevating the temperature of the coke above that of the bed, so that heat is transferred to the primary reactor by recycle thereto of the heated coke particles. A portion of the coke is generally consumed by the combustion reaction this also supplying heat to the reaction.

There are a number of deficiencies associated with such processes. A marked limitation is that these processes leave much to be desired from a heat conservation standpoint. The processes are thermally inefficient, particularly a high temperature coking process. In high temperature coking, also, much of the coke is consumed by the gasification reactions. In relatively low temperature coking operations, on the other hand, a coke product is left which contains a high volatiles content. Such coke must be calcined before the coke is suitable for general use, this necessitating extra steps in a process. Besides coke, large amounts of soot are also formed in such processes.

Soot formation results in the degradation of feed, waste of fuel, reduction of desirable yields, and is generally inefficient.

For these and other reasons, there is need in the art for a new and improved process.

Accordingly, it is the primary objective of the present invention to obviate these and other difficulties. In particular, it is an objective to provide an improved process for the manufacture of a hydrogen-enriched gas and high quality, high temperature coke of low or negligible volatile content, such product requiring little or no calcining prior to most usages. Another object is to provide a high efiiciency process which provides considerable flexibility in that good quality carbon black can also be coproduced, if desired; or, on the other hand, essentially all of the feed converted to hydrogen-enriched gas and coke. A further object is to provide a more efficient process wherein coke can be produced in good yield without significant coke consumption via gasification or significant heat degradation. Yet another object is to provide a process which will produce a coke product of low sulfur and low metals content. It is also an object to provide a new and novel coke product.

These and other objects are achieved in accordance with the present process which contemplates the combination of low temperature and high temperature reaction zones, each containing fluidized beds of coke solids. Feed hydrocarbon is injected and cracked in a low temperature reaction zone and the products therefrom transferred to a high temperature reaction zone and subjected to more rigorous or elevated temperatures to produce hydrogenenriched gas and a novel high temperature coke product.

Heat for the reactions is directly supplied to a high temperature zone by circulation, i.e., transfer and recycle, of coke solids, in dilute phase, through a heater zone wherein the temperature of the coke solids is elevated above that of the bed to impart heat to the bed when the heated coke is returned thereto. Heat is supplied to a low temperature bed by controlled circulation of coke between a low temperature and high temperature bed.

Feed is introduced and initially cracked by contact with hot coke solids in a low temperature zone, and the products of the reaction, which include the coke, are withdrawn and transferred to a high temperature zone. The products are further reacted in the high temperature zone to give rise to a hydrogen-enriched gas, high temperature coke, and carbon black. The carbon black produced in the reaction can be slurried with the feed which is injected to a low temperature zone and ultimately converted to coke, if desired, so that essentially only hydrogen-enriched gas and coke are withdrawn from the process. A portion of the coke product is preferably ground or otherwise reduced in size and returned to a reaction zone as seed.

A feature of the process is that it provides for the preparation of a new and novel high temperature coke product by incorporation of carbon black therein at the time of coke formation. Such product is formed by the production, withdrawal, and reintroduction of carbon black into the reaction system. Quality carbon black is thus produced within a high temperature reaction zone by selection of conditions favoring its yield. The carbon black is then removed from the process, admixed or slurried with a feed hydrocarbon and reintroduced in the process via a low temperature reaction zone. The carbon black, is a low temperature reaction zone, adheres to the solid coke particles and the coated particles are then introduced into a high temperature reaction zone, and circulated back and forth between the zones while the individual particles grow in size.

Carbon black can be concurrently produced in a high temperature reaction to provide yields as high as about fifty percent, based on the weight of the total carbon present in the hydrocarbon feed. More generally, however, the production thereof is controlled to yield from about 10 to about 30 percent quality carbon black, based on the weight of the total carbon present in the hydrocarbon feed. Where conditions are controlled to yield up to about 20 percent carbon black, it has been found that the entire amount of carbon black can be slurried and reintroduced with the feed into the low temperature reaction zone to form products consisting only of a hydrogenenriched gas and quality coke. Upon introduction of the coated coke solids into the high temperature reaction zone, the feed portion of the coating will coke, and volatile matter will be substantially eliminated. Circulation and recirculation of the coke between the low temperature and high temperature reaction zones and repetitive contacting with fresh carbon black slurry and subsequent treatments providing average total resistance times in the reactor system ranging from about 1 to about 12 hours, and preferably from about 2 to about 3 hours, will result in the formation of coke of unusual structure and quality. The carbon black is totally dispersed throughout a coke particle, and the physical characteristics thereof are significantly different from, e.g., coke formed entirely within a high temperature or low temperature coking process. Formation of this type of coke, furthermore, provides benefits in both the process as well as in the coke product.

It has also been found necessary to control conditions within the high temperature reaction zone to obtain suitable carbon black. It has been found that quality carbon black can be produced only by maintaining the high temperature reaction zone between about 2000 F. to about 2400 F., and preferably the temperature should not exceed about 2200 F. The fluidized bed of the zone is maintained in a state of subdivision such that fine bubbles are provided, these constituting vapor spaces within which the carbon black is formed, and contact times between the solids and gases range from about 5 to about 20 seconds, and preferably from about 10 to about 15 seconds. A surprising and unique feature of the process is that quality carbon black can be obtained from essentially any kind of hydrocarbon feed, even normally gaseous hydrocarbons. This is sharply contrasted with conventional methods of forming carbon black which require select high grade hydrocarbon feedstocks.

The coke product of this invention is one characterized as coke particles containing up to about twenty percent incorporated carbon black, based on the weight of the total coke particles. Preferably, the coke product contains from about five to about fifteen percent carbon black dispersed throughout the individual coke particles. The coke product is constituted of generally round individual coke particles. An individual particle has a grainy appearance, this being caused by its peculiar structure. The structure is composed of a series of layers of onionlike skins about a central core or seed. Each layer is believed constituted of a large number of platelets of coke overlapping, one with another, and the individual layers are thus shingle-like in appearance. The individual layers are well oriented, one with respect to the other, and range only a few hundred Angstrom units in thickness. It is believed that the incremental additions of carbon black as the coke is repeatedly recycled between low and high temperature zones, and repetitively treated, causes interruptions in the formation of individual coke layers so that new layers are being continuously formed as new junctions are formed by deposition of carbon black particles. Whatever the cause of such formations, however, the sum-total effect is that the new coke product, inter alia, mixes well with binder, provides good wetability, e.g., in a cryolite bath, and has suitable electrical conductivity.

In general, the reactions can be conveniently carried out in a single reactor or in a multiple stage reactor, e.g., in a single two-stage reactor which houses separate fluidized beds or in a two-stage reactor unit comprising two individual vessels, each containing separate fluidized beds of particulate coke. In, e.g., a first vessel is provided a high temperature zone, and therein the fluidized bed is maintained at a temperature ranging from about 1800 F. to about 2600 F., and preferably from about 2000 F. to about 2200 F., while in the other, or second, is provided a low temperature zone containing a fluidized bed of coke operated at a temperature ranging from about 900 F. to about 1400 F., and preferably from about 1000 F. to about 1200 F.

Coke is circulated between the beds of the two vessels during an operation. Coke is transferred from the bed of the high temperature zone to the bed of the low temperature zone to provide heat to the latter. Heat for the over-all operation is provided to the high temperature coking zone by circulation of coke, in dilute phase, through an adjacent externally fired transfer line heater. Fuel, e.g., hydrogen or natural gas, is burned with oxygen or an oxygen-containing gas (air) and the hot gases are directly contacted with the coke. The coke is heated to temperatures ranging generally from no more than about 50 to about 300 Fahrenheit degrees, and preferably from about 100 to about 200 Fahrenheit degrees, above the temperature to be maintained within the high temperature zone and the coke is circulated at a rapid rate to minimize coke consumption.

Coke is circulated through the transfer line heater in a dilute phase gas-solids system and at a velocity permitting a very short residence or contact time between the solids and the combustion gas. Generally, the contact time is maintained within a range of from about 0.1 second to about 1 second, and preferably the contact time ranges no more than from about 0.2 to about 0.5 second. The loading, or amount of coke solids contained within the dilute gas-solids system passed through the transfer line heater, preferably ranges from about 0.5 to about 4 pounds of coke solids per cubic foot of gas, and more preferably from about 1 to about 2 pounds of coke solids per cubic foot of gas.

In general, gas and solids handling involves use of conventional equipment, cyclone separators, risers, standpipes, and the like. The invention will be better understood by reference to the following detailed description, which describes the process by reference to the attached schematic flow diagram.

Referring to the figure is shown an upper vessel, or reactor 10, and a lower vessel, or reactor 20.

Reactors

10, 20 are coupled together and interconnected or communicated one with the other through a grid 11 having one or a plurality of openings, a single grid opening being shown for convenience. Each

reactor

10, 20 contains a particulate

coke solids bed

12, 22, respectively, fluidized by ascending gases.

It is the function of circulatory loop 50 to provide heat for the entire reactor system by circulation of coke between high temperature reactor and an external heater 52.

Coke solids must also be transferred from high temperature reactor 10 to the low temperature reactor to provide heat. Coke solids are thus transferred or passed from high temperature reactor 10 to low temperature reactor 20 via the loop 30.

Fresh coke solids are fed into high temperature reactor 10 via line 23 and coke is withdrawn from low temperature reactor 20 via line 27, cooled and sent to storage. A portion of the product coke is finely ground and returned as seed via

lines

25, 23 to high temperature reactor 10. Hydrocarbon feed is injected into low temperature reactor 20 via line 26 and is cracked to deposit carbonaceous solids upon the coke solids constituting bed 22 and to liberate gases.

Coke solids are also transferred from low temperature reactor 20 into high temperature reactor 10 for further treatment. Some coke solids from low temperature reactor 20 are thus returned to high temperature reactor 10 via upward passage through

lines

24, 23, respectively. Gases are also continuously evolved from reactor 20 and channeled upwardly through a sized, inverted cone-shaped grid opening 11 with substantial quantities of entrained solids. The hot effluent vapor scours and cleans the walls around the opening to lessen the formation of carbonaceous deposits and prevents plugging. The gas is also further reacted or cracked in the high temperature reactor 10. The injection of the relatively low temperature solids into the upper bed 12 further heat treats and calcines the coke solids.

Gases evolved from high temperature reactor 10 are separated in cyclone separator system 40 and the entrained coke solids returned to the same reactor.

The sum total effect of these additions and withdrawals are that solids are continuously introduced as seed particles into the high temperature reactor 10, a coke product is formed, and the coke is used as a heat carrier to transfer heat to high temperature reactor 10 and to the low temperature reactor 20. The seed particles grow by the cracking reactions. The seed particles grow to some extent in the low temperature cracking reactions wherein as much as about five to twenty percent of the hydrocarbon feed is cracked, and to a much greater extent in the high temperature cracking reaction wherein as much as about eighty-five percent of the feed hydrocarbon is cracked. Where a carbon black-hydrocarbon slurry is used as a feed, however, the carbon black adheres to the individual particles as a sticky mass and is transported to the high temperature cracking zone for further reaction. After suflicient residence time in the reactor system to form a homogeneous mixture of the desired product, the high temperature coke product is withdrawn from the low temperature reactor 20, as during a cotninuous operation when a portion of the solids is withdrawn via

lines

24, 25. Withdrawal of coke from the low temperature zone provided considerable heat economy, particularly as contrasted with conventional high temperature coking processes.

It can be considered that there are four important coke flow systems in the entire reactor fluidized solids system, and three of these are major coke circulation systems. Those formed by

loops

30, 50 and the transfer via grid opening 11 between reactor 20 to reactor 10 are of ma jor importance. Another coke flow system is that formed by transfer of coke via

lines

24, 23 from low temperature reactor 20 to high temperature reactor 10. A remaining coke transfer system, of relatively minor importance, is that formed by circulatory loop 40 which constitutes a cyclone separator 41 located at the top of reactor 10. Gas and entrained coke solids are removed from the top of reactor 10 via line 42 and separated in separator 41. The gases and entrained carbon black, generated in the proc ess, are removed from the top of cyclone 41 and carbon black is separated from the gas stream effluent by conventional cyclones and bag filters. Coke is returned from cyclone 41 downwardly via line 43 and riser 44 to the same reactor 10.

The carbon black, if desired, can be mixed with feed, and injected back into the low temperature reactor 20 with fresh feed. In accordance with this technique, essentially all of the carbon black produced in the reaction can be coated upon the hot coke particles within the low temperature reaction zone and transferred into the high temperature zone wherein the carbon black is carbonized or converted into calcined coke. Hence, the process can be utilized, if desired, to produce essentially only coke and a hydrogen-enriched gas.

Coke flow system 50 circulates coke between the high temperature reactor 10 and the transfer line heater 52, this providing process heat for the entire series of endothermic cracking reactions. Coke at relatively low temperature is thus taken from the bottom of reactor 10 and flowed through the cold solids riser 51 and through the heater 52. A hydrogen gas operated stripper reaction (not shown) can be provided, if desired, to lessen the transfer of carbonaceous gases into the riser 51. In any regard, the coke is passed therethrough while in dilute phase, and the temperature of the coke passing heater 52 is generally rapidly elevated above the temperature of fluidized bed 12 of reactor 10. It is thence passed into heater cyclone 53 where solids are disengaged and the gas separated therefrom, the hot coke solids passing downwardly through dipleg 54 wherein a coke level is main tained, and from whence they are returned through the hot solids standpipe or riser 55 to the bottom of reactor 10. The hot coke passed into reactor 10 imparts heat to the coke solids of fluidized bed 12 of the reactor. The coke circulation rate in loop 50 is quite rapid, and accomplished by varying the riser gas velocity and the differential pressure between the reactor 10 and the heater 52 to provide the desired flow rate of coke. This is to say also that the gas velocity in the hot solids riser 51 determines the level of coke to be maintained in dipleg 54, and in the hot solids standpipe 55 so as to return coke to reactor 10 at the same rate that it is being circulated to transfer line heater 52.

Heat is provided to low temperature reactor via transfer of hot coke from high temperature reactor 10 through loop 30. Hot coke solids from reactor 10 is transferred via riser 31 to disengaging drum 32, the separated solids falling downwardly through dipleg 33 to the bottom thereof where a level is maintained. Coke is trans ferred from dipleg 33 to the top of reactor 20 via riser 34, and the rate of flow can be controlled by regulating the pressure drop between riser 31 and disengaging drum 32 to provide the desired temperature in reactor 20. Circulation can also be controlled by the velocity and pressure drop imposed on the reactor 20 across riser 34.

A coke circulation loop is also formed by line 24 to the external riser 23 for returning coke from the low temperature reactor 20 to the high temperature reactor 10. The rate of return is controlled by the gas rate and line 24 slide valve setting which is preferably maintained relatively constant throughout normal operation. Another method in which coke is returned from low temperature reactor 20 to high temperature reactor 10' is by entrainment of coke solids with the gases passing through grid opening 11. Entrainment can be normally such as to return from about 20 percent to about 40 percent of the coke, and preferably from about percent to about percent of the coke to high temperature reactor 10. The rate of coke return can be varied in different ways, e.g., by changing the fluidized bed level in reactor 20, varying the fluidizing gas flow rate into reactor 20, or feeding extraneous gas to the top of reactor 20 to effect pressure changes.

Coke particles are also separated from the gaseous eflluent evolved from high temperature reactor 10, though this does not constitute a major coke circulation loop. Thus, coke and gas are evolved from reactor 10 via line 42 and are separated at reactor cyclone 41. The separated coke fines are transported, or falls downwardly, through cyclone standpipe 43 to the bottom thereof wherein a coke level is maintained. Coke is returned to the same reactor via riser 44.

The function of the solids circulating systems is to provide adequate process temperatures in

reactors

10, 20. Temperature control in the high temperature reactor 10 is maintained by the coke circulation rate and the temperature rise of the coke as it passes through the transfer line heater. The preferred method of operation is to maintain the circulation rate near the maximum operable value by providing a rapid flow of coke through the transfer line heater 54 while providing the necessary temperature to produce sufficient temperature rise of the coke to maintain the desired temperature in reactor 10. By providing dilute phase transfer of coke through the heater and very short contact, the rate of coke burnup is maintained at an extremely low value.

The source of heat to the low temperature reactor 20, as indicated, is by coke circulation from the high temperature reactor 10. Such circulation is sufficient to provide all of the heat required in reactor 20. The bottom bed temperature of reactor 20 is thus extremely sensitive to changes in coke circulation rate. The circulation rate, however, can be readily controlled to provide a uniform temperature in reactor 20.

The following example is exemplary and describes a preferred mode of operation of the process.

In a continuous operation, the fluidized bed 12 of the high temperature reactor 10 is maintained at 2000 F., and the fluidized bed 22 of the low temperature reactor 20 is maintained at 1000 F. Coke is withdrawn from the fluidized bed 12 of reactor 10 and transferred, in dilute phase, through the auxiliary or transfer line heater 54 whereupon it is heated to 2200" F. Coke burnup is minimized by maintaining a residence time in the heater of about 0.5 second. The hot coke is recycled to the reactor 10 to maintain the desired temperature.

The fluidized bed 22 of reactor 20 is maintained at 1000 F. by transfer of coke at 2000 F. from reactor 10 via loop 30 into the top of fluidized bed 22 of reactor 20.

Coke, which has been treated at high temperature, is removed from low temperature reactor 20 via line 27 and a portion thereof, after grinding, is returned via

line

25, 23 to reactor 10 as seed coke.

The carbon black which is formed is removed from the effluent evolved from the top of reactor 10 by scrubbing and filtering.

Bunker C fuel oil with a gravity of 12.6 API, a carbonzhydrogen ratio of 8.36, and a Conradson carbon of 16.0 weight percent is slurried with the carbon black generated in the reaction and fed via line 26 into reactor 20.

High temperature coke and enriched hydrogen gas are removed from the process as products. The coke, ranging from about to microns in size, is mixed with finely ground coke from the same source, having an average particle size of about 40 microns, in 80 parts to 20 parts fines, respectively. The mixture is then blended with 12 parts coal tar binder, thoroughly mixed, and prebaked in an oven to form an electrode. The electrode has superior strength and high density and, when immersed in the cryolite bath of an operating aluminum cell, wets well and provides good conductivity.

A relatively wide variety of feed hydrocarbons are suitable for the practice of this invention, even those of relatively high sulfur and metals content, since the present process results in the drastic reduction of these elements in the final coke product. In general, feed hydrocarbons suitable for use in the present invention include those characterized as high concarbon residual oils, i.e., these consisting generally of high boiling hydrocarbons of API gravity ranging between about minus 10 to 20 degrees, a Conradson carbon between about 5 and 50 weight percent, and an initial boiling point ranging from about 850 F. to about 1200 F. Exemplary of such feeds are shale oils, asphalts, tars, pitches, coal tars, synthetic oils, cycle stocks, extracts, recycled heavy ends from conversion products, whole crudes, heavy distillates or residual fractions and mixtures thereof. Even normally gaseous hydrocarbons, e.g., methane, ethane, propane, etc., can be additionally injected into the high temperature zone to form carbon black, if desired.

It is apparent that the described process combination can be modified without departing the spirit and scope of the invention.

Having described the invention, what is claimed is:

1. In an endothermic process for forming gaseous and carbonaceous products by cracking hydrocarbons by contact with hot particulate coke solids, the combination comprising:

establishing separate communicating reaction zones,

each containing fluidized beds of particulate coke solids at diiferent elevated temperatures, a low tem- 9 perature reaction zone operated at temperatures ranging from about 900 F. to about 1400 F., and a high temperature reaction zone operated at temperatures ranging from about 2000 F. to about 2400 transferring and exchanging coke solids between the said reaction zones, supplying heat for the said reaction zones by circulating coke solids particles, in a dilute phase gas-solids system, between the high temperature reaction zone and an auxiliary heating zone and heating the coke solids particles by direct contact with the combustion products of fuel and oxygen,

supplying heat for the low temperature reaction zone by directly transferring hot coke solids particles from the high temperature zone to the said low temperature zone,

injecting hydrocarbons into the said low temperature reaction zone and cracking same by contact with the hot particulate coke solids,

while withdrawing the coke product from the low temperature reaction zone.

2. The process of claim 1 wherein the temperature provided in the high temperature reaction zone ranges from about 2000 F. to about 2200 F., and the temperature provided in the low temperature reaction zone ranges from about 1000 F. to about 1200 F.

3. The process of claim 1 wherein the loading of coke solids in the dilute phase gas-solids system circulated through the auxiliary heating zone ranges from about 0.5 pound to about 4 pounds, per cubic foot of gas, and the contact time of the solids with the combustion gases within the auxiliary heater zone ranges from about 0.1 to about 1 second.

4. The process of claim 3 wherein the dilute phase gassolids system is flowed upwardly through the auxiliary heating zone, the coke solids heated by direct contact with the combustion products of air and natural gas, and wherein a contact time ranging from about 0.2 to about 0.5 second is provided.

5. The process of claim 1 wherein the coke solids are heated to temperatures ranging from about 50 F. to about 300 F. above the temperature of the fluidized bed of the high temperature reaction zone.

6. The process of claim 1 wherein high temperature and low temperature reaction zones are intercommunicated via an opening through which the gaseous product with entrained coke solids is transferred from low temperature reaction zone to high temperature reaction zone, this forming a portion of a circulatory loop for transfer of coke solids between high temperature reaction zone and low temperature reaction zone.

7. The process of claim 2 wherein carbon black is produced by providing a gas solids contact time between the fluidized bed solids and effiuent gas from a low temperature zone ranging from about 5 seconds to about 20 seconds, then separated from the efiiuent gas evolved from the high temperature reaction zone, the carbon black admixed with the hydrocarbon feed in concentration ranging up to about 20 percent of carbon black, based on the weight of the total carbon content of the feed, and the admixture fed into the low temperature reaction zone to produce adhesion of the carbon black upon the coke solids surfaces.

8. The process of claim 7 wherein the carbon coated coke product is circulated between the low temperature and high temperature zones to provide a homogeneous mixture while maintaining average total residence times in the reaction zones ranging from about 1 to about 12 hours.

9. As an article of manufacture, the coke product produced by the process combination comprising establishing separate communicating reaction zones, each containing fluidized beds of particulate coke solids at different elevated temperatures, a low temperature reaction zone operated at temperatures ranging from about 900 F. to about 1400 F., and a high temperature reaction zone operated at temperatures ranging from about 2000 F. to about 2400 F., respectively, generating carbon black within the high temperature reaction zone, withdrawing same, and admixing the carbon black with the hydrocarbon feed in concentration ranging up to about 20 percent of carbon black, based on the weight of the total carbon content of the feed, and feeding the admixture into the low temperature reaction zone to produce adhesion of the carbon black upon the coke solids surfaces, and thence circulating the coke solids between the said reaction zones to calcine the coke.

10. The article of manufacture of claim 9 wherein the coke product is withdrawn from the low temperature reaction zone.

11. The article of manufacture according to claim 9 wherein the temperature provided in the high temperature reaction zone ranges from about 2000 F. to about 2200 F., and the temperature provided in the low temperature reaction zone ranges from about 1000' F. to about 1200 F.

12. The article of manufacture according to claim 11 wherein the carbon coated coke product is circulated between the low temperature and the high temperature zones to provide a homogeneous mixture while maintaining average total residence time in the reaction zones ranging from about 1 to about 12 hours.

References Cited UNITED STATES PATENTS 2,885,267 5/1959 Buchmann et al. 23-212 2,985,512 5/1961 Avey 23-212 3,205,044 8/1965 Berger 23-212 HERBERT LEVINE, Primary Examiner U.S. Cl. XrR.