|Publication number||US2894897 A|
|Publication date||Jul 14, 1959|
|Filing date||May 28, 1954|
|Priority date||May 28, 1954|
|Publication number||US 2894897 A, US 2894897A, US-A-2894897, US2894897 A, US2894897A|
|Inventors||Post Howard E|
|Original Assignee||Universal Oil Prod Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (7), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
July 14, 1959 H. EfPosT v2,894,897
HYDROCARBON CONVERSION PROCESS IN THE PRESENCE OF ADDED HYDRDGEN Filed May 28. 1954 United States Patent HYDROCARBON CONVERSION PROCESS IN THE PRESENCE `0F ADDED HYDROGEN Howard E. Post, Skokie, lll., assigner, by mesne assignments, to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Application May 28, 1954, Serial No. 433,018 8 Claims. (Cl. 208-111) This invention relates to a process for purifying and exhaustively converting hydrocarbons and particularly to a combination process for converting a heavy petroleum fraction into puried lower boiling material and at the same time aiding in the disposal of an industrial waste material.
It is a main object of this invention to combine a hydrocarbon conversion process advantageously and interrelatedly with a noxious industrial waste material disposal process to obtain benefits for both processes.
It is another object of this invention to rene an entire crude oil to produce a purified light material without the production of a residuum fraction and with the elimination of multiple fractionation and treating stages.
lt is another object of this invention to maintain the entire process including the reaction Zones, the regeneration and burning Zones and the fractionation zone in a heat balance relationship so that the heat produced in the exothermic reactions is advantageously utilized in the endothermic reactions and the total quantity of heat present within the process at any time may be regulated by balancing the amount of exothermic and endothermic reactions effected. The heat balance method of the present invention provides a means of converting heat energy into chemical energy whereby it may be disposed of by converting a stream of material into a stream of different material of higher free energy.
It is still another object of this invention to recover mercaptan and thiophene compounds that are removed in the purication of a hydrocarbon fraction and to react these normally wasted materials to form their corresponding hydrocarbon molecules and hydrogen sulde, the latter of which may be disposed of.
In one embodiment the present invention relates to a process for converting hydrocarbon which comprises contacting said hydrocarbon with hot contact material in a coking zone at coking conditions and converting said hydrocarbon to a cracked product and coke which deposits on said contact material, passing said contact material to a burning zone wherein it is contacted with oxygen-containing gas to oxidize a portion of the coke therefrom thereby raising the temperature of said contact material, returning a portion of the resultant hot contact material from said burning Zone to said coking zone as the aforesaid hot contact material, passing another portion of hot contact material from said burning Zone to a water gas producing Zone wherein it is contacted with H2O at conditions to produce water gas, returning the contact material from said water gas producing zone to said burning zone, passing said cracked product to a fractionation zone wherein a light fraction is separated from a heavy fraction, returning said heavy fraction into contact with said hot contact material, passing said light fraction into contact with an alkaline medium, separating a substantially sulfur-free light hydrocarbon fraction and a sulfur-containing alkaline medium, passing said water gas into contact with said sulfur containing alkaline medium to remove carbon oxides therefrom and to displace combined sulfur from said alkaline medium whereby a hydrogen and combined sulfur stream is produced and passing the latter stream into said coking zone to supply the hydrogen atmosphere thereto.
in a more speciic embodiment the present invention relates to a process for refining petroleum which cornprises passing said petroleum and a cracked product stream into a fractionation zone, separating from said zone a light distillate stream and a combined feed stream passing said combined feed stream into contact with iluidized hot particulate Contact material in the presence of hydrogen maintained in a coking zone to produce cracked product and coke which deposits on said contact material, passing said contact material to a burning zone wherein it is contacted with oxygen-containing gas to oxidize a portion of said coke therefrom thereby raising the temperature of said contact material, returning a portion of said hot Contact material from said burning zone to said coking zone as the aforesaid hot contact material, passing another portion of hot contact material from said burning zone to a water gas producing zone wherein it is contacted with H2O at conditions to produce water gas, returning the contact material from said water gas producing zone to said burning Zone, passing said light distillate into contact with an aqueous alkaline medium, separating a substantially sulfur-free product and a combined sulfur-containing alkaline stream, contacting said water gas with said sulfur-containing alkaline stream, separating a substantially neutralized stream and a combined sulfur and hydrogen-containing gas stream and passing the latter into said coking zone to form the aforesaid hydrogen therein.
The process of the present invention has many advantages over previous similar processes that are known in the art. The process of this invention provides a means of processing a total crude oil in a single unitary process to produce any desired petroleum product or series of products without residuum streams and without energy requirements with regard to reaction energy and heat. The crude oil may be fractionated in the present invention by the heat supplied to the fractionator by the cracked product from the coking Zone. Under ordinary conditions this will be suicient heat to effect the separation of the cracked product as well as the incoming crude so that all of the light material from the cracked product is commingled with the straight run light material from the crude to pass overhead to subsequent operations. The heavy material contained both in the crude charge and in the cracked product descends the column and is withdrawn from the lower section from where it is withdrawn as a combined feed for the coking or cracking portion of the process. When it is necessary, a reboiler may be used to provide sufficient heat to the fractionation column, however it is contemplated that suflicient heat is available from the process to effect this fractionation and in fact it is contemplated that a cooling medium will be required in the upper portion of the column rather than a heating medium in the bottom.
The combined feed, as hereinbefore stated, passes to a coking zone wherein it is converted into vaporizable material and a solid carbonaceous coke which deposits on the particulate contact material maintained therein. As hereinbefore described the vaporized cracked product is passed into a fractionator with the incoming crude and the two streams are mutually fractionated in the manner described. The coke particles resulting from the reactions in the coking zone are passed into a regeneration or burning zone wherein they are contacted with oxygen which results in simple combustion which removes al portion of the coke as carbon oxide and raises the temperature of the particles proportionate to the amount of burning effected. The coke particles which are now in a hot condition are then returned into contact with the combined feed stream to effect further reaction thereof.
Another portion of the hot coke particles are passed into contact with water and the contact of hot carbon and H2O at the temperature of the particles causes a series of reactions known as the water gas reactions thereby producing, among other things, hydrogen, carbon dioxide, and carbon monoxide. The coke particles from the water gas producing zone are cooled substantially and are returned to the burning zone wherein they are further heated by contact with hot particles and by combustion of the remaining coke deposited on them.
It is advantageous to effect coking and cracking reactions in the presence of hydrogen so that a more saturated and more stable product is produced and further more desirable products are produced. In previous processes the water gas produced in the manner hereinbefore described is passed into the coking zone to supply this desirable hydrogen thereto. It is, however, undesirable to use water gas in the coking zone inasmuch as the impurities in the water gas, namely carbon dioxide and carbon monoxide, contaminate the liquid product and the oxides of carbon lower the hydrogen concentration. It is therefore desirable to enrich the water gas in hydrogen prior to introducing it to the coking zone. One means of enriching a water gas stream in its hydrogen content is to remove carbon oxides by contacting the stream with an alkaline medium so that the slightly acid carbon oxides will be removed by neutralizing the alkaline medium while the neutral hydrogen is not effected thereby. It is an object of this invention to purify water gas solution by contacting it with an alkaline medium, however, the alkaline medium used is spent alkaline medium that was previously used to desulfurize the product from this process and is ready to be disposed of. By contacting this spent alkaline medium with water gas a triple advantage is obtained. First, the carbon oxides are removed from the water gas thereby substantially enriching it in hydrogen. Second, the alkaline medium is neutralized so that it may be disposed of without unduly contaminating the area of disposal and third the organically bound sulfur in the alkaline medium is displaced into the water gas stream so that it is returned to the coking zone wherein desulfurization is effected so that the hydrocarbon portion of the molecule is saved.
It is unnecessary to dwell upon the economic advantages of profitably using a normally wasted material. Whereas the spent alkaline medium used to desulfurize a petroleum product formerly was disposed of, sometimes with great diiiiculty, the process of the present invention provides a means of improving the refinery operation by employing this material. Formerly the disposal of waste caustic or spent caustic required treating the spent material to neutralize it 'so that it did not contaminate wells or streams in the area where it was disposed of. This neutralization has been effected by adding chemicals, which of course is expensive in that additional material must be purchased, or by bubbling flue gas through the caustic so that the acid material in the flue gas would neutralize the alkaline material. The present invention allows an undesired alkaline material to be neutralized by removing an undesired acid material from a process stream whereby the process stream is improved and the acid and alkaline material are mutually disposed of in the form of a neutral substance.
The sulfur content of various crude oils and particu- `lai-ly of various fractions of a crude oil varies considerably. Naphthas and gasoline have been known to contain up to 5 weight percent of sulfur measured as elemental sulfur. The sulfur in a petroleum fraction is generally in the form of organically bound sulfur such as mercaptan or thiophene compounds. These compounds exhibit acid characteristics so they are removed from the fraction by reacting them with an alkaline material. Although the process elfectively removes sulfur ythere is great waste in that the hydrocarbon portion of the molecule, which represents by far the greater weight of material, is removed along with the sulfur. Besides the wastefulness of the process there is also created a disposal problem since the noxious thiophene and mercaptan compounds are in the form of` liquids and therefore diicult to dispose of, The present invention provides a means of utilizing the hydrocarbon portion of a mercaptan or thiophene molecule by hydrogenating and cracking the molecule to form hydrogen sulfide and the corresponding hydrocarbon and at the same time eliminating the disposal problem by causing all of sulfur in the molecule to be in the form of hydrogen sulfide which is a gas and which may be readily disposed of.
The fractionation zone of the present invention may be any conventional fractionation column which is provided with means of effecting intermediate contact between a rising gas stream and a descending liquid stream such as bubble plates, perforated decks, packing, etc. The column is provided with at least one feed point maintained at an intermediate portion thereof and at least one light product withdrawal means and one heavy product withdrawal means. When the charge to the fractionation zone is separated into only one overhead and one `bottoms product the withdrawal means will be disposed in the uppermost and lowermost zones respectively, however, any number of side cuts may be removed from the column without departing from the broad scope of this invention. It is contemplated that the fractionation zone is operated at whatever temperature is required to effect the desired fractionation at slightly superatmospheric pressure to facilitate the flow of material therefrom and to increase the ease with which the overhead product may be condensed. When it is desired to operate for a minimum bottoms fraction, the fractionation zone of the present invention may be operated at atmospheric or any subatmospheric pressure and this latter embodiment is especially useful when the nature o-f the charge stock is such that its cracking temperature is below its vaporization temperature under normal conditions. The fractionation zone may as hereinbefore stated, be provided with a means of heating the material in the lower portion to vaporize it thereby supplying the rising vapor stream `and/or it may be provided with a means of reflux in the uppermost portion to provide cooling to the top of the tower and thereby further increase the eiciency of the fractionation. As hereinbefore stated, the present invention contemplates that all of the heat required for the fractionation will be supplied from the cracked product passing into the fractionation zone concurrently with the crude. Depending upon the proportion of crude and cracked procluct, the temperature of both streams and their composition, the feed or feeds to the column may be liquid, vapor or mixed. The column may be provided with a header so that the-charge to the f ractionator may ybe fed through any of a multiplicity of points so that the optimum feed tray may be selected.
The coking zone of the present invention is preferably maintained at a temperature of from about 750 F. to about 1500 F. and at a pressure of from about atmospheric to about 600 pounds per square inch or more. The coking zone will preferably contain a fluidized bed of particulatecontact material which is maintained at leastl partially in the tluidized state by means of an ascending stream of hydrogen-containing, gas passing therethrough, The reactions effected in the coking zone are numerous and complex. One of these reactions is the cracking reaction which comprises severing of a carbon-carbon bond to.,
reduce the size of the hydrocarbon molecules and form olefinic molecules. which are lower boiling. Another reacnon effected in the coking zone is the polymerization or .alkylation reactionv which comprises fusion of molecules to.
form higher lboiling molecules such as the reaction between two olefinicmolecules to form yanother olenic molecule whose size is equivalent to the addition of the sizes of the two olefinic molecules. The most common of the polymerization reactions effected in this zone is the fusion or condensation of aromatic type hydrocarbons to form extremely heavy and carbonaceous condensed ring compounds, usually termed polynuclear aromatics, which are heavy, tacky liquids, or as the polymerization reactions continue, become black, solid carbonaceous material known as coke. Other reactions include isomerization to form molecules of the same molecular weight with different geometric configuration, dehydrogenation reactions which consist of a severence between a carbon and hydrogen bond, aromatization which is probably a complex reaction involving dehydrogenation and cyclization of an olenic or paraflinic hydrocarbon, hydrogen and alkyl transfer reactions which are similar to isomerization reactions and many others.
The use of a fluidized bed of hot particulate material has been thoroughly discussed in the prior art and its advantages in regard to efficient contacting and desirable temperature regulation are too well known to be discussed in detail herein. The bed of uidized particles may consist of either catalytic or non-catalytic particles of any desirable size and composition. When a net solid coke product is desired it is advantageous to employ particles of carbon or coke as the hot contact material so that the coking reactions causes a gradual increase in the size of each particle. The solid product of such a process is thus homogenous with respect to composition. When a net coke yield is obtained there will usually be incorporated into the process a zone for classifying the coke particles according to size so that the larger coke particles are withdrawn as yield while the smaller particles are returned to the coking zone to act as nuclei for further coking reactions. Other non-catalytic particular material which may be used includes siliceous material such vas pebbles, kieselguhr, diatomeaceous earth, clays, or such material `as pumice, bauxite, alumina, etc.
The process may also be effected in the presence of catalytic material which increases the selectivity of the reactions to produce greater quantities of desirable material boiling in the gasoline range and lesser quantities of undesirable normally gaseous material and coke. The use of a catalytic contact material furthermore allows the coking zone to be operated at a lower temperature with the resultant saving in materials of construction. The catalytic material used may be any of the common cracking catalysts including silica-alumina, silica-magnesia, silica-zirconia, silica-al-umina-magnesia, combinations of these with such material as boron, halogens, Vanadium, tungsten, molybdenum, chromium, manganese, iron, cobalt, nickel, palladium, platinum, copper, combinations of these such as cobalt-molybdenum, chromium-molybdenum, chromium-nickel, iron-copper and others. The combinations of inorganic oxides in themselves generally promote cracking reactions while the use of groups V, VI, VII and VIII metals of the periodic system in the form of free metals, suldes, oxides, or other compounds thereof generally promote hydrogenation and dehydrogenation reactions. The addition of halogen phosphate, or other acid acting material further may promote both hydrogenation, cracking and even burning reactions effected in the regeneration zone.
To maintain the contact material in the coking zone in a uidized state the hydrogen-containing gas is introduced into the lower portion of the zone so that it passes upwardly therethrough. The charge stock or combined feed may also be introduced concurrently with the hydrogen or it may be introduced directly into the fluidized bed. The latter embodiment is particularly desirable if the combined feed is of such a nature that it'produces solidv coke almost immediately upon con- 6 tact with hot material. When ordinary charge stocks are encountered, however, it is preferred to introduce the charge and the hydrogenacontaining gas concurrently so th-at the vaporized charge stock is used as a lifting gas to transport the particulate solid to the coking zone.
The burning zone or regeneration Zone, similar to the Cokin-g zone, has maintained therein a fluidized bed of particulate contact material which is maintained in the state of hindered settling by an lascending stream of oxygen-containing gas passing therethrough. The oxygen-containing gas which is usually air reacts with the coke deposited on the particles of contact material to cause oxidation which results in a continuously changing composition of the oxygen-containing stream, it becoming increasingly richer in carbon oxides as it ascends through the burning zone and increasingly poorer in oxygen. The burning zone is preferably operated at a temperature of from about l200 F. to about 2500 F. or more and its temperature will be regulated by the heat requirements of the process, the amount of coke to be removed, the thermal characteristics of the contact material, etc. It is contemplated that the burning zone effects only a partial removal of the coke on the particulate material, the remainder of the coke being removed endothermically in the Water gas producing zone.
In the Water gas producing zone the hot particles are contacted with H2O and the well known water gas reactions are effected to produce hydrogen and carbon oxides. The hydrogen producing zone is maintained at a temperature in excess of l200 F. so that the reaction rate and equilibrium are suitable for the production of hydrogen. It is desirable to maintain the Water gas producing zone at a fairly high temperature so that the products withdrawn therefrom consist largely of hydrogen. It is, of course, obvious that the ultimate temperature maintained in the hydrogen producing zone will depend largely upon the economics of constructing a zone to withstand high temperatures and it is therefore preferred that the hydrogen producing reactions are effected at temperatures of from about 1500 F. to about 2000 F. or slightly more. It is particularly advantageous in the process of the present invention that the product contain a minimum of carbon monoxide since each molecule of carbon Vthat is converted to carbon dioxide produces two molecules of hydrogen wherein the production of carbon monoxide indicates a use of carbon that is not optimum and requires further purification of the resulting Water gas stream. It may be desirable to provide a means of quenching the products from the water gas producing zone so that the favorable equilibrium established at the closely regulated conditions may be frozen.
The water gas reactions are not simple and may require particular conditions to be maintained in the Water gas producing zone in order to procure the most desirable results. The reactions effected in the water gas producing zone consist of reactions between H2O and carbon to produce hydrogen, carbon dioxide, carbon monoxide, methane and possibly higher boiling hydrocarbons. Each of the reactions operates independently with regard to the equilibrium established at each temperature, however, the reactions are interrelated in that the product or consumption of the product of one reaction will eifect the rate of other reactions by increasing or decreasing the concentration of products or reactants of the others. For example, as the temperature of the reaction zone increases from a low temperature to a moderate temperature the equilibrium for the formation of methane becomes less favorable thereby increasing the amount of hydrogen in the reaction zone. As the temperature increases to the moderate temperature range, that is about 1500" F., the equilibrium for carbon dioxide formation is favorable and the hydrogen production rate is extremely high due to the fact that methane formation is inhibited and carbon monoxide formation;
is also inhibited so that a maximum of hydrogen is realized for each molecule of carbon. It may be seen that the increased production of hydrogen by the destruction of methane will inhibit the formation of hydrogen by the reduction of water in that greater quantities of product will be present in the reaction zone and relatively lesser quantities of reactants.
As the temperature increases from the moderate temperature range to the high temperature range, that is about 2000 F. and higher, the equilibrium favors the formation of carbon monoxide thereby at least partially diminishing the hydrogen production by causing the formation of less carbon dioxide. At these temperatures, however, the production of methane is virtually entirely eliminated thereby causing increasing amounts of hydrogen to be in the reaction product due to the diminished amount of methane. It may be seen here again that the law of mass action will operate when one reaction changes the concentration of reactantsand products of another. Operating conditions such as temperature, pressure, space velocity, etc, effect the various reactions due to volume increases or decreases and the fact that different reactions are effected at different rates.
From the foregoing discussion it may be seen it would be diiicult to predict optimum operating conditions and these most frequently must be obtained by varying conditions until a suitable product is obtained. The water gas producing zone as the other zones in this process is preferably maintained in a uidized state and this is particularly important in this zone inasmuch as the temperature at which the reaction is effected is rather critical in determining the composition of the product.
The light material passing overhead from the fractionation zone, which as hereinbefore described contains the lower boiling portions of both the original charge stock and the cracked product, will contain mercaptan and thiophene sulfur components. These undesirable contaminants in the product are removed by contacting the product with an alkaline medium so that the acidic mercaptan and thiophene molecules react to form compounds with the alkaline material and thereby entering the alkaline medium phase, with the resultant removal from` the petroleum phase. The scrubbing is generally effected countercurrently in a liquid-liquid contacting device with an aqueous alkaline medium. Suitable alkaline materials are sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium hydroxide, other alkaline inorganic salts and alkaline organic material such as ethanolamine, diethanolamine, etc. The mercaptan and thiophene sulfur thus removed will form lose compounds or complexes with the alkaline material and may be readily displaced therefrom by a more acidic material. It is preferable that the sulfur scrubber is maintained at a temperature and pressure that will have both the hydrocarbon and the aqueous alkaline phase liquid so that improved contact may `be obtained, however the alkaline phase may be solid and the hydrocarbon phase may be gaseous and the process may still function. The hydrocarbon phase discharges from the upper portion of the sulfur scrubber as a substantially sulfur-free material while the sulfur-containing alkaline medium discharges from the lower portion thereof and is passed into the upper portion of the Water gas scrubber wherein it countercurrently contacts an ascending stream of Water gas produced as hereinbefore described.
In the water gas scrubber the carbon oxides contained in the water gas, ybeing more acidic than mercaptan or thiophene compounds, react with the alkaline medium to neutralize it and at the same time to displace the mercaptan and thiophene compounds into the water gas stream. A substantially neutral stream of' treating medium discharges from the lower portion of the water gas scrubber While asubstantially enriched hydrogen stream containing: mercaptan and thiophene-compounds discharges from theupper portion of the Water gas scrubber and passes into the coking zone as the aforementioned hydrogen. The hydrogen thus introduced into the coking zone tends `to saturate the oleiins produced therein and inhibits coke formation while the mercaptan and thiophene compounds are converted into hydrogen sulfide and hydrocarbons.
The improved process of the present invention may be more clearly explained with reference to the accompanying drawing which illustrates one embodiment of this invention and is intended to illustrate rather than limit the. invention to the particular embodiment herein described.
Referring now to the drawing, crude charge enters the process through line 1 and is commingled with cracked product obtained as hereinafter described and enters the process through line Z. The stream of crude charge and the stream of cracked product may be commingledl in line 3 and mutually passed into an intermediateA portion of fractionator 4 wherein the stream is separated into a low boiling and high boiling fraction by customary fractionation methods. The stream of crudev charge and the stream of cracked product may also -be introduced into fractionator 4 at dilferent points. The charge to the fractionator mayl also be only the crude oil and the cracked product in line Z may not be introduced into the fractionator. When sufficient heat is not supplied to the fractionation zone by the cracked product, heater, 9 may be employed by means of the illustrated thermo- Siphon which is contrived by connecting heater 9 to fractionator 4 though lines 7 and 5. When the reboiler or heater 9 is not required for the fractionation valves 8 and 6 may be closed to block the reboiler out of operation.
The material is separated into a high boiling or combined feed fraction which passes from the lower portion of fractionator 4 through line 10 and a low boiling or light distillate fraction which passes from the uppermost portion of fractionator 4 through line 11 and is condensed in cooler 12 to at least partially form a liquid phase which descends to receiver 14 wherein uncondensable gases are separated from the liquid phase and vented through line l5. The liquid product in receiver 14 passes through line 16 wherefrom it is split, a portion rbeing' returned to the uppermost contacting section in fractionator 4 as redux and another portion `being withdrawn through line 18 as light distillate product.
The light distillate product which contains sulfur in the form of mercaptan and thiophene compounds passes through line 18 into the lower portion of sulfur scrubber 33 wherein it ascends in countercurrent contact with a descending stream of alkaline medium or fresh alkali introduced into the upper portion of sulfur scrubber 33 through line 32. As a result of the countercurrent contact in sulfur scrubber 33, the mercaptan andy thiophene compounds are removed to the alkali phase and discharge from t'ne lower portion of sulfur scrubber 33 through line 35 while a substantially sulfur-free light hydrocarbon is withdrawn from the upper portion of sulfur scrubber 33 through line 34. This substantially sulfur-free light hydrocarbon is the product from the process and may cornprise gasoline, and heavier fractions including gas oil and will generally require stabilization and possible further fractionation before it is ready for the market.
The sulded alkaline material Withdrawn from the lower portion of sulfur scrubber 33 through line 3S is passed into the upper portion of water gas scrubber 36 wherein it descends in countercurrent contact with an ascending stream of Water gas. The 4ascending water gas stream contains among other things carbon dioxide, carbonmonoxide and hydrogen and as a result of the contact with the sultided alkaline medium the acidic carbon oxides are adsorbed with the resultant displacement of at least a portion of the mercaptan and thiophene compounds contained in the alkaline medium. Some of the hydrogen sulfide in the alkaline medium will also be displaced; however, the hydrogen sulde being moreV acidic than mercaptan and thiophene compounds will be more diffi-v cultly displaced and therefore will pass from the lower portion of water gas scrubber 36 through line 37 with the spent alkaline medium. Under proper operating conditions the alkaline medium discharged through line 37 will be substantially neutral and under most conditions it will be of substantially decreased alkalinity and therefore more readily disposed of.
A hydrogen-containing gas stream substantially diminished in carbon oxide content is discharged from the upper portion of water gas scrubber 36 through line 38. This gas stream will also contain whatever mercaptan and thiophene compounds were displaced from the sullided alkali. The hydrogen-containing gas stream passes through line 38 and enters line 39 wherein it is commingled with a stream of hot particulate contact material. When required suitable means may be provided to transfer a mixed gas and liquid hydrogen stream to the reaction zone. Although a single pump may be suitable, a settling zone with a special liquid pump may be provided to transport the liquid phase mercaptan and thiophene compounds to the coking zone.
The hydrogen-containing gas stream rising through line 39 entrains the hot particles of contact material and the combined stream of gas and particles mutually ascends line 39 and discharges into the lower portion of coker 23. In one embodiment of this invention the combined feed hereinbefore described may pass through valve 21 and enter line 39 wherein it is ycommingled with both the hydrogen-containing gas and the hot particles and at least partially vaporized by such contact with hot particles and ascends the conduit 39 as a part of the ascending stream. When the charge stock enters coker 23 through line 39, the stream entering the lower portion of coker 23 will `contain hydrogen, thiophene and mercaptan cornpounds, hot particulate contact material, vaporized charge stock, liquid charge stock and cracked products inasmuch as at least a portion of the :cracking reactions will be effected while the stream is in transit through line 39.
In another embodiment of this invention valve 21 may be closed and valve 20 opened so that the combined feed from line will pass through line 19 and enter an intermediate portion of coker 23 to be discharged directly into the bed of fluidized contact material maintained therein. This latter embodiment is particularly desirable when the characteristics of the combined feed are such that excessive coking would be eifected in line 39 resulting in clogging or extreme pressure drop therein.
In coker 23 the hereinbefore described coking reactions are effected and result in the production of a cracked product which is lower boiling than the combined feed and a coke deposit on the particulate solid contact material making up the fluidized bed. The fcracked product which is in the form of vapors passes from the upper portion of coker 23 through the beforementioned line 2 and is'introduced into fractionator 4, or may be sent to another actionator. The resultant coked particles of contact material are passed from the lower portion of coker 23 through line 24 wherefrom they discharge into the upper portion of burning zone 25.
In burning zone 25 the coked particles are contacted with an ascending stream of air which enters the lower portion thereof through line 26 and which may be distributed by means of a grid or other distributing device. The iluidized contact of oxygen-containing gas and coked particles results in combustion which removes a portion of the coke from the particles and increases their temperature. The resulting llue gas is discharged from the upper portion of burning zone 25 through line 27. Line 22 passes hot particles from the lower portion of burning zone 25 and discharges them into the beforementioned line 39 which returns them to coking zone 23. Line 28 also passes from the lower portion of burning zone 25 and passes hot carbon-containing particles into contact with an ascending stream of H2O in line 29. The combined stream of H2O and hot carbon-containing particles rises through line V29 and while in transit at least partially reacts to produce hydrogen and carbon oxides. The remainder of the water gas producing reactions are effected in water gas reactor 30 wherein a iluidized bed of the coke-containing contact material is maintained in suspension with the ascending gas stream. The water gas reaction is endothermic and substantially cools the particles of coke-containing solid and these particles are discharged from the lower portion of Water gas reactor 30 through line 40 into the upper portion of burning zone 25 Wherein they are subjected to further heating due to oxidation of residual coke and contact with other hot particles.
The water gas resulting from the contact of H2O and hot carbon in water gas reactor 30 pass from the upper portion thereof through line 31 and into the lower portion of water gas scrubber 36 wherein the hereinbefore described enrichment in hydrogen is elfected.
It is of course obvious that many modifications of this process may be made by one skilled in the art of petroleum refining and these modifications are intended to be within the broad scope of this invention. Such modifications may include the use of dense moving beds of Xed beds in place of the iluidized beds which form the preferred embodiment of this invention. The various reaction Zones may be disposed in a unitary structure and may have the flow therebetween regulated by various means. eIt is of course contemplated that various pumps, valves, instrumentation etc. which are required to regulate and elfect the flow of material between the various stages of this process will be used and since these form no part of this invention a description thereof is not included in this specication. It is also intended that aids to the process may be incorporated therein such as stripping streams where required which prevent the entry of undesirable material to the various zones along with the transfer of solid particles. Therefore, steam, llue gas, or other inert gases may be introduced into line 24 through line 41 to prevent entrained and occluded vaporizable hydrocarbon from entering the burning zone with the resultant saving of vaporizable product and prevention of unduly high combustion temperatures. Similarly, line 42 may introduce a stripping medium into line 22 to prevent occlusion of oxygen-containing gas or carbon oxides on the particles coming from the burning zone and passing into the coker.
The process of this invention provides a means of balancing and distributing heat between exothermic and endothermic reactions so that all portions of the plant may always be maintained at the proper temperature and energy level to effect the desired results. The coking zone causes a deposit of coke on the particles which must be removed and this rremoval. may be efected in two ways; namely by burning in the burning zone and by reducing water in the water gas reaction zone. The burning reaction is an exothermic reaction which causes a temperature increase while the water gas reaction is an endothermic reaction which causes a temperature decrease. It may thus be seen that for any given quantity of coke to be removed from the particles, the removal may be distributed between the burning zone and the water gas reaction Zone so that the temperature of the particles may lbe maintained at any desired level. Thus, a charge stock at ambient temperature is heated to be at least partially vaporized in a fractionation zone by contacting superheated cracked product which also requires fractionation. The cracked product contains suilcient superheat to supply sensible heat and latent heat of vaporization to the charge stock thereby effecting the fractionation by means of the heat of the product. The combined feed which results from the fractionation is at a high temperature due to its contact with cracked product and the temperature of the combined feed is further raised by its contact with hot particles. As a result, coke is laid down and its subsequent remo-val supplies the heat for further cracking as well as the heat for the original fractionation.Y
In most operations the coke laydown will be sufficient to supply all the heat required for reacting and the heat required for fractionation and there will be additional heat to be disposed of andl this is particularly true in the case of processing heavy residuum fractions or total crude wherein large quantities of high boiling material are present. ln the present invention the additional heat that must be disposed of is used in the water gas reaction zone to reduce water to. hydrogen thereby converting thermal energy to chemical` energy in the form of a higher free; energy substance i.e, hydrogen fromV a lower energy substance i.e. water.
Y Since the amount of hydrogen to be produced in the water gas reaction zone is not critical the amount of water gas reaction may be varied or completely discontinued depending upon the heat` disposing requirements of the process. In ordinary coking or catalytic cracking operations, when for example the compositionl of the charge stock changes so thatgreater quantities of coke are produced, the additional burning required to remove the extrak coke produces a. hotter contact material which in turn produces higher conversion of the charge stock which in tum produces more coke which again in turn produces greater heat. It may be seen that this snowballing elfect is very undesirable and requiresA heat removal in some form. In the process of the present invention when greater quantities of coke are produced the distribution of carbon removal is changed so that greater quantities are removed by means of the water gas reaction and the temperature ofthe particles may be maintained constant.
From the foregoing specification it may be seen that the process of the present invention provides a means of refining a total crude oil to produce relatively saturated, sulfur-free and purified light products without a residuurn fraction and without the necessity of additional heat and at the same time neutralizes spent caustic material so that it may be readily disposed of and recovers mercaptan and thiophene compounds that are ordinarily lost.
I claim as my invention:
l. A hydrocarbon conversion process which comprises coking lhydrocarbon material in the presence of hydrogen and a solid contact material in a coking zone, thereby depositing coke on the solid material, separately removing cracked hydrocarbon products and'soiid material from the coking zone, contacting at least a portion of the solid material, while still containing at least a portion of the deposited coke, with H2O at water gas producing conditions, separating resultant water gas from the solid material, contacting at least a portion of said cracked hydrocarbon products with an alkaline medium to transfer sulfur from the former to the latter, contacting said Water gas with the resultant sulfur-containing alkaline medium to remove carbon oxides from the water gas and thereby enrich the gas with respect to hydrogen, and introducing thus enriched gas to said coking zone to supply hydrogen for the coking step.
2. A process for converting hydrocarbon which comprises contacting said hydrocarbon with hot solid contact material in a coking zone at coking conditions in the presence of hydrogen obtained as hereinafter set forth and converting said hydrocarbon to a cracked product and coke which deposits on said contact material, passing said contact material to a burning zone wherein it is contacted with oxygeneontaining gas to oxidize. a portion of the coke therefrom thereby raising the temperature of said contact material, returning a portion of the resultant hot contact material from the `burning zone to the coking zone as the aforesaid hot contact material, passing another poition of said hot contact material from said burning zone to a water gas producing zone and therein contacting, the material with H2O at conditions to produce water gas, returning the resulting contact material from said water gas producing zone to said burning zone, passing said, cracked product to n fractionation zone where- 12 in alight fraction is separated from a heavy fraction, returning said heavy fraction into contact with `said hot contact material, passing said light fraction into contact with an alkaline medium, separating a substantially sulfur-free light hydrocarbonv fraction from a resulting sulfur-v containing alkaline meditun, passing said water gas fromv the water gas producing zone into contact with said sulfur-containing alkaline medium to remove carbonoxides therefrom and to displace combined sulfur from said alkaline medium, separating a substantially neutralized alkaline medium stream and a combinedY sulfur and hydrogen-containing gas stream and passing the latter stream into said coking zone as the aforesaid hydrogen.
3. A process for reiining petroleum which comprises commingling said petroleum with a cracked productstream and passing the resultant commingled stream intoy a fractionation zone wherein it is separated into a light distillate stream and a combined feed stream, passing said combined feed stream into contact with fluidized hot' particulate contact material in the presence of hydrogen maintained in a coking zone to produce cracked product and coke which deposits on said contact material; passing said contact material to a burning zone wherein it is con' tacted with oxygen-containing gas to oxidize a portion of said coke therefrom thereby raising the temperature. of said contact material, returning a portion of said hot contact material from said burning zone to said coking-v zone as the aforesaid hot contact material, passing another portion of hot contact material from said burning zone to a water gas producing zone wherein it is contacted with H2O at conditions to produce water gas, returning the contact material from said water gas producing zone to said burning zone, passing said light distillate into contact with an aqueous alkaline medium, separating a substantially sulfur-free product and a combined sulfur-containing alkaline stream, contacting said water gas with said sulfur-containing alkaline stream, separating a substantially neutralized alkaline stream and a combined sulfur and hydrogen-containing gas streamv and. passing the latter into said coking zone to form the aforesaid hydrogen therein.
4. The process of claim 2 further characterized in, that said alkaline medium comprises sodium hydroxide.
5. The process of claim 2 further characterized in that said hot solid contact material comprises silica-alumina.
6. The process of claim 2 further characterizedV in that said hot contact material comprises coke particles.
7. The process of claim 2 further characterized in that said contact of reactant streams and solid material is effected in fluidized beds of solid material.
8. The process of refining petroleum which comprises commingling. said petroleum with a cracked product stream and passing the resultant commingled stream` into a fractionation zone wherein it is separated into a light distillate stream and a combined, feed stream, passing said combined feed stream into contact with fluidized hotparticulate contact material at a temperature of from about 750 F. to about 1500 F. in the presenceof hydrogen maintained in a coking zone to produce cracked product and coke which deposits on said contact material, passing said contact material to a burning zone wherein it is contacted with oxygen-containing gas to oxidize a portion of said coke therefrom thereby raising the temperature of said contact material, returning a portionI of said hot contact, material from said burning zone to said coking zone as the aforesaid hot contact material, passing another portion of hot contact material from said burning zone to a water gas producing zone wherein it iscontacted with H2O at a temperature in excess of about l F. to produce water gas, returning the contact maf terial from said water gas producing zone to said burning zone, passing said light distillate into contact with an aqueous sodium hydroxide, separating a substantially sulfur-free product and a combined sulfur-containing sodium hydroxide stream,r contacting said water gas. with said sulfur-containing sodium hydroxide stream, separating a substantially neutralized sodium hydroxide stream and a combined sulfur and hydrogen-containing gas stream and passing the latter into said coking zone to form the aforesaid hydrogen therein.
References Cited in the le of this patent UNITED STATES PATENTS 2,311,342 Kerns et al Feb. 16, 1943 14 e s, Roetheli Oct. 31, 1950 Rex Aug. 26, 1952 Cornell Oct. 14, 1952 Gohr et al Dec. 21, 1954 Beckberger Mar. 13, 1956
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|US4374018 *||Apr 20, 1981||Feb 15, 1983||Air Products And Chemicals, Inc.||Method for producing upgraded products from a heavy oil feed|
|U.S. Classification||208/111.15, 208/127, 208/95|