Unusual flexibility and a quick accurate system for recording data and calculating results enable this pilot unit to forge a wedge into unexplored potentials of petroleum hydrogena tion
I
R. S. MANNE, H. G. BOYNTON, and A . M . SOUBY Research and Development Division, Humble Oil and Refining Co., Baytown, Tex.
General Purpose Hydrogenation Pilot Plant
The pilot unit with stabilizer in foreground. The reactor is the insulated vessel beyond the two liquid-level controller arms
ETROLEUM REFISERS are confronted with the problem of manufacturing products of increasingly higher quality, usually from crude oils of decreasing quality. This problem cannot be solved economically by using conventional methods of product finishing, such as acid-treating, caustic washing, or usual sweetening procedures. I n postwar years, refiners have turned more and more to use of hydrogenation processes for improving yields and quality, particularly sirice fairly pure hydrogen from catalytic reforming operations has become available in large quantities. Mild hydrogenation is being used extensively as a method of product finishing, especially for naphthi?, kercsine, Diesel fuel: heating oil, and distillate lubricating oils. Primarily it replaces other less efficient methods of treating for removing sulfur compounds, improving color and odor, and increasing the storage stability of the products. Also, more severe hydrogenation is being investigated, particularly as applied to heavy gas oils and residual stocks, in order to remove sulfur, nitrogen, and metals, improve the catalytic cracking characteristics of gas oil, and convert residual srocks to distillatts with a consequent reduction in low quality fuel oil production. A variety of pilot units have beEn employed in this work, ranging from the small-scale unit described by Roth (4)to the 50-barrels-per-
640
day pilot unit described by I\/IcAfee (2). The research and development division of Humble Oil and Refining Co. has for some time been engaged in develdping hydrogenation processes. For these studies it has employed a versatile, moderate-scale pilot unit (feed rate, 0.5 to 3.0 barrels per day) which can be operated over a wide variety of conditions with a wide range of feed stocks, to produce sufficient quantities of products for complete evaluations, and to provide engineering data which can be used for plant design. The unit, designed with emphasis on flexibility, has been operated a t charge rates varying from 0.5 to 4.0 volumes of oil prr hour per volume of catalyst, pressures to 800 pounds per square inch gage, temperatures to 850' F., and recycle gas rates from 0 to 6000 standard cubic feet per barrel of oiI charged. Approximately 1.25 gallons of catalyst constitutes a charge to the 2 inch X 8 foot reactor. Feed stocks used without need for changes in equipment range from a light West Texas gas oil having a gravity of 35 O API to a fluxed asphalt of 7.2' API gravity. The unit can be operated either with once-through or recycle gas; the gas can be taken either from commercial tank wagons or from plant reforming units a t Humble's Baytown refinery. A continuous vacuum flash tower operating a t controlled pressures as low as 2 mm. of mercury absolute permits bottoms having a boiling point in excess of 1040' F. to be recycled if desired. The
INDUSTRIAL AND ENGINEERING CHEMISTRY
oil preheat system is designed to allow considerable variation in holding time under almost any temperature pattern. and permits the study of thermal or catalytic processes. L7arious combination operations such as a mild catalytic hydrogenation with a severe thermal pretreat can also be carried out. Valves, orifices, and pumps are designed to have capacities well in excess of those employed for most average operations. This permits wide variations in conditions, including the use of high throughput rates and high gas-to-oil ratios. O n the other hand, these items of equipment are either providrd with sufficient control for operation a t low percentages of their maximum output, or they are manifolded with smaller equipment to permit operation, if desired, a t very low throughputs and gas rates without loss in accuracy. Facilities are provided for regenerating the catalyst in place and for determining the amount of carbon and sulfur removed from the catalyst by regeneration. A number of unusual safety devices are provided. The unit is operated by onr man per shift except during runs employing the vacuum recycle facilities. Since the vacuum equipment was provided as a major addition to a n existing unit, a second operator was made available.
Pilot Unit Flow Liquid Flow. Oil feed is charged From heated weigh tanks by means of a
H Y D R O G E N IN THE PETROLEUM INDUSTRY reciprocating pump and, after mixing with the gas, flows through the preheat system to the top of the down-flow reactor. The total reactor product passes to a high pressure separator which provides a hydrogen-rich recycle gas stream overhead. The liquid flows from the bottom’of this vessel on liquid level control to the stabilizer which is operated under total reflux and from which only gas is removed overhead. The stabilized product can pass to a product weigh tank; or it can undergo additional fractionation, first in a n atmospheric flash tower where naphtha, kerosine, and heating oil can be taken overhead, then in a continuous vacuum flash tower where products boiling up to 1040O F. can be taken overhead. Operation of the vacuum flash tower permits 1040’ F. and heavier bottoms to be recycled to the reactor if desired. The recycle is charged to the reactor with fresh feed through the system previously described. Gas Flow. Make-up gas, either commercial cylinder hydrogen from a tank wagon or catalytic reformer tail gas from a plant unit, is metered into the system on rate-of-flow control. This make-up gas combines with the overhead from the high pressure separator to provide the total gas stream charged to the reactor. This combined stream enters the suction side of a two-stage reciprocating compressor which discharges gas to the reactor through a rate-of-flow control valve. The recycle gas and liquid feed, combined ahead of the preheat system, enter the reactor in admixture. I n addition to a bleed stream from the high pressure separator overhead, a gas stream leaves the unit at thestabilizer overhead. This tail gas, along with the recycle gas and the make-up gas, if other
The hydrogenation treating pilot unit
Panel board of the pilot plant. Variable voltage transformers are in foreground, temperature controllers and indicators in center, and pressure gages and controllers in background
than cylinder hydrogen, is bled continuously through recording gas gravitometers to floating head receivers for composite sampling.
Description of Equipment Feed System and Preheat. Oil feed is charged to the unit from either of two 120-gallon stainless steel drums mounted on Toledo floor scales. Both drums contain steam coils and the steam input is controlled by a Brown pneumatic temperature controller. A 3/8-inch Viking gear pump is manifolded to take suction a t the bottom of either charge drum and circulate the oil through
I
n,
n
BOTTOMS RECYCLE PUMP
RECYCLE METERING DEVICE
steam-traced lines to the suction of the positive displacement charge pump, with excess oil being returned to the top of the charge drum. A I/2-inch duplex Hills-McCanna Dositive disdacement pump with adjustable stroke is employed to pump oil feed to the reactor and to regulate the feed rate. Oil charge rates of 0.5 to about 5.0 gallons per hour, can be handled. These charge rates represent a range of from 0.4 to about 4.0 volumes of oil per hour per volume of catalyst. Hydrogen from a trailer truck or alternatively, reformer tail gas (80 to 90y0 hydrogen) may be charged to the same system. The make-up gas is dis-
U
BOTTOMS SCALES
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641
charged on rate-of-flow control into the compressor suction system where it is mixed with gas recycle from the reaction zone. This mixture, the compressor suction feed, is maintained at a constant pressure of about 30 pounds per square inch gage by a Hammel-Dah1 control valve which releases excess gas through a wet-test meter to the vent. By adjusting the make-up gas rate-of-flow controller so that the efflux of excess gas from the system is small, the unit can be operated with only the sampling requirement of about 2 to 3 standard cubic feet per hour of excess gas. Operation in this manner maximizes the accuracy of hydrogen consumption calculations. The recycle gas with its complement of make-up gas is compressed in an Ingersoll-Rand ER-5 two-stage reciprocating compressor. The compressor discharge is pressure controlled at about 100 pounds per square inch above reactor pressure with excess discharge gas recycling through an Annin pressure control valve into the compressor suction. The compressor interstage knockout pot is steam heated so that light ends will not condense in the lubricating oil. The flow of lubricating oil is kept a t an absolute minimum consistent with safe operation of the compressor. Light ends which condense in the second stage knockout pot are permitted to flow back into the sight glass of the stabilizer. The flow is regulated by a Hoke needle valve based on observation of bubbles rising through the sight glass. The recycle gas is on rate-of-flow control and joins the oil feed ahead of the lead baths. Two orifices are manifolded into the recycle gas line in such a manner that they may be used separately or conjunctively to measure gas rates ranging from about 30 to about 400 standard cubic feet per hour, The mixture of oil feed and recycle hydrogen is preheated to the desired reactor temperature by means of four lead baths and a fluidized sand bath in series. The lead baths consist of coils of I/d-inch extra heavy stainless steel pipe, numbered 1 through 4, having lengths of 44, 83, 57, and 22 feet, respectively. Two 5-kw. Calrod heaters are immersed in each lead bath. The fluidized sand bath contains an 8-foot coil of I/d-inch extra heavy stainless steel pipe around which fine sand is fluidized by air. Heat is supplied by means of a 5-kw. electrical winding wrapped around the outside of the bath. Temperature on each of the preheat baths is separately controlled, thus permitting a wide range of preheat severity. For example, minimum preheat may be attained by operating all the lead baths at 350' to 400' F. (or as low as possible while maintaining oil fluidity) and the sand bath at about 50" F. higher than the desired reactor inlet temperature. O n the other hand, severe preheat may
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be imposed by operating lead baths Kos. 1 through 4 at 500°, 700°, 820°, and 850' F., respectively, and the sand bath at 800" to 850' F. Reactor and High Pressure Separator. From the sand bath outlet, the mixture of heated vapor and liquid passes through an electrically wound transfer line into the top of the reactor. The reactor is constructed from 98 inches of 2-inch extra heavy Type 304 stainless steel pipe. There are four skin temperature and six process temperature points in the reactor. The process temperature points are the reactor inlet, catalyst bed inlet, catalyst bed '/3 (I/$ of the distance from catalyst inlet to catalyst outlet), catalyst bed 2/3, catalyst bed outlet, and reactor outlet. All the process points and skin temperatures are continuously recorded. The upper and lower halves of the reactor are each wound with one 5-kw. electrical winding on top of 1 inch of Super-X insulation. Outside the winding is 1 inch of Super-X and 3 inches of sponge felt insulation. Additional thermocouples, between the winding and the reactor wall midway of each of the two windings, measure insulation temperatures and thus indicate heat transfer through the insulation. Current to each winding is controlled by a Wheelco temperature controller. The reactor is operated in such a way that process temperatures and corresponding insulation temperatures are maintained as nearly equal as possible; this indicates zero heat flow and, consequently, adiabatic operation. I n addition to the windings already described, the top and bottom flanges are electrically wound. These flanges are maintained at the reactor inlet and reactor outlet temperatures, respectively. A differential pressure meter continuously records pressure drops through the catalyst bed. This measurement is valuable both as engineering design data and as a measure of the rate of carbon build-up on the catalyst. The reactor effluent is cooled and passed through either of two glass wool filters to a high pressure separator. The separation is made at reactor pressure and at as low a temperature as is consistent with maintaining flow of the viscous oil. The separator is equipped with a condenser in the overhead and with a plug of wire mesh to knock back any entrainment. Under these conditions the recycle gas is predominantly hydrogen. During most operations it has analyzed about 70 to 85% hydrogen, 5 to 15% hydrogen sulfide, and the remainder light hydrocarbons. The hydrogen is taken off through an Annin Domotor valve which controls the pressure in the separator and the reactor. The built-in positioner feature of this valve has helped to overcome valve plugging which at one time oc-
INDUSTRIAL AND ENGINEERING CHEMISTRY
curred here and elsewhere on the unit. Small particles of suspended catalyst fines or carbon caused unpositioned valves to stick even though all streams are filtered at least once beyond the reactor. Stabilizer, Atmospheric Flash, and Vacuum Flash. The liquid product flows from the bottom of the high pressure separator on liquid level control through a steam-jacketed preheater to the stabilizer. The bottom of the stabilizer is wound with one 5-kw. electrical heater and the bottoms tempcrature is manually controlled at about 350" to 400" F. The entire vessel is constructed of 4-inch carbon steel pipe and the section above the feed inlet is packed in ascending order with three disk-and-donut trays, about 24 inches of '/Z-inch ceramic Raschig rings, and about 6 inches of rolled wire mesh. A watercooled condensing coil is mounted in the top, and the stabilization is carried out under total reflux. Noncondensables pass out the top of the stabilizer through an Annin Domotor control valve to sampling and measurement. This vent gas usually consists of about 10 to 20% hydrogen, 35 to 50% hydrogen sulfide, and the remainder light hydrocarbons. The control valve maintains a back pressure of about 25 pounds per square inch gage on the stabilizer. The stabilized liquid product flobvs out the bottom of the stabilizer on liquid level control either to a product weigh tank similar to the oil feed drums described previously or to additional fractionation facilities which have been provided to permit recycle of that portion of the product boiling above about 1040' F. The stabilized product flo\vs through an electrically wound transfer line into an atmospheric flash tower operating at about 600' to 650" F. and 10 pounds per square inch gage. This tower is constructed of 4-inch carbon steel pipe and contains about 6 inches of rolled wire mesh immediately above the feed inlet to knock back entrainment. Two 5-kw. electrical windings wrapped the entire length of the tower are used to maintain isothermal conditions within the tower. The overhead product consisting of naphtha, kerosine, and heating oil, is condensed and routed to the product weigh tank mentioned in the preceding paragraph. The bottoms product flows on liquid level control through a glass wool filter and an electrically wound transfer line to the vacuum flash tower operating at about 600' to 650" F. and 3 mm. of mercury absolute pressure. This tower, also constructed of 4-inch carbon steel pipe, is electrically compensated with one 5-kw. and one 2-kw. winding for isothermal operation. Entrainment is eliminated by offsetting the upper half of the tower about 6 inches, thus forcing the vapors to make two 90' bends. Wire mesh as an entrainment eliminator was avoidedi since this
H Y D R O G E N IN THE PETROLEUM I N D U S T R Y would have created a n unnecessarily high pressure drop through the column. Vacuum is maintained by an Elliott three-stage noncondensing steam-jet ejector and is controlled through a Bristol absolute pressure recorder-controller actuating a pneumatic control valve in the vacuum line just upstream of the ejector. The hydrocarbon vapors are partially condensed in the top of the tower by a hot water coil and the condensate flows by gravity to an external accumulator operating a t tower pressure. Vapors leaving the tower are condensed in a n external cold water condenser in the overhead line, which is sloped downward away from the tower so that condensates will flow by gravity into the accumulator. I n addition, the vacuum line to the ejector is sloped so that any material condensing in this line flows to the accumulator. The accumulator liquid is pumped to the product weigh tank where it is combined with the atmospheric tower overhead. An air-driven Viking gear pump is used for this purpose, and a liquid level is maintained in the accumulator by a Fielden Tektor liquid level controller actuating a solenoid valve in the air supply line to the pump. Vacuum tower bottoms (nominally 1040' F. and heavier) are removed by a constant-speed Viking pump discharging through a glass wool filter to the suction of a Hills-McCanna quadruplex positive displacement pump which manually controls the rate of bottoms recycle. This pump discharges into the oil feed line just ahead of the lead baths. The liquid level in the vacuum tower is controlled through a level controller actuating a pneumatic control valve in a branch line o f f the gear pump discharge which permits bottoms product to flow to an open-top drum on portable Toledo scales. The excess pump effluent above that required for recycle and for level control flows through a spring-loaded check valve back to the pump suction. The check valve holds about 30 pounds per square inch gage pressure on the gear pump discharge system and a constant pressure on the reciprocating pump suction. Bottoms recycle rate is measured by periodically bypassing the oil through a mercury-filled U-tube having in one leg two electrical contacts with a calibrated displacement between them. This device is located immediately ahead of the Hills-McCanna bottoms recycle pump. A solenoid valve in the main oil flow line between the two legs of the Utube is closed, thus forcing the oil to flow into one leg of the U-tube. When the ,oil-mercury interface passes the first electrical contact, a relay is actuated which starts a timer. When the inter-
Flash vaporization equipment. Flow i s from right t o left through atmospheric flash zone, vacuum flash tower, vacuum overhead accumulator, and t o product drum on scales
face passes the second electrical contact, relays are actuated which stop the timer and open the solenoid valve, thus permitting the mercury legs to equalize to their original level, ready for the next measurement. A sufficient volume of oil is maintained on top of both mercury
legs to prevent interruption of the oil flow'while a measurement is being made and to prevent forcing mercury into the main oil flow line. Since the 1040' F.and-heavier bottoms product must be held at about 300" F. in order to maintain fluidity, lines from the vacuum
VOL. 49,
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tower bottoms to the junction of the oil recycle and fresh feed lines are steam jacketed wherever possible. Steam tracing is used on elbows, pump manifolds, etc. Product Handling
I n runs employing bottoms recycle, two liquid product streams exist. The first of these, overhead from the atmospheric and vacuum flash towers recombined into one distillate stream (or total liquid product if bottoms recycle is not used), is collected in a weigh tank while the heavy residuum is collected in open-top drums on small platform scales. The distillate is circulated in the weigh tank until thoroughly mixed a t the end of a run before it is pumped from the tank to barrels for storage. During pump out, samples are collected and submitted immediately for distillations, gravity, sulfur, viscosity, and other required product inspections. Spot samples for sulfur content and gravity are taken at regular intervals during the course of pilot unit runs so that operations can be closely monitored without waiting for the results of composite sampling done at the end of a run. Composite samples of make-up, recycle, and stabilizer gas are submitted for mass spectrometer analyses after each run. This is necessary so that accurate balances can be made for hydrogen and other components. Gravities of these gases are recorded continuously during runs on Arcco Anubis continuous recording gravitometers. Since hydrogen sulfide is lost during gas collecting and handling, periodic spot analyses for hydrogen sulfide in recycle and tail gases are made during each run. These values are calculated into the mass spectrometer results. Large scale distillations are made periodically on products from selected runs in order that large enough samples for testing of all fractions may be obtained. Regeneration. Slow build-up of carbon and other combustibles, which deactivate the catalyst, dictates that periodic regeneration be employed. This is accomplished by admitting mixtures of controlled concentrations of air in nitrogen to the bottom of the catalyst bed at temperatures high enough to initiate burning. Regeneration with oxygen-containing gas is preceded and followed by a 2- to 3-hour purge with inert gas. The oxygen inlet line is physically disconnected from the reactor inlet before hydrogenation is resumed so that no possibility of leakage exists. The regeneration gas is preheated to 800" F. in a coil submerged in molten lead and thence passes to the reactor through an electrically wound transfer line which maintains this temperature.
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Regeneration off gases pass through a heated copper oxide bed for converting carbon monoxide to dioxide and thence to a caustic scrubber to absorb carbon and sulfur dioxides. The progress of the flame front through the reactor is followed by means of eight reactor temperature points. Burning is continued until carbon dioxide is no longer present in the off gases; if it is still present after the burning reaches the top, an increase in reactor temperature or a slight increase in oxygen concentration often suffices to complete combustion. Oxygen concentrations must be kept sufficiently low to avoid reaching bed temperatures in excess of about 1200" F. above which catalyst damage may result. At temperatures of about 1400' to 1500' F.,a phase change occurs in the alumina catalyst support. The change is exothermic and self-supporting and destroys catalyst activity. When oxygen concentrations of 1% are employed, the temperature rise is around 250' F. at the flame front: thus, the catalyst is not heated above 1050" F. However, if oxygen concentration were increased to about 370, temperatures in the danger range would result. Oxvgen concentration is hand controlled by metering in the air and nitrogen streams separately. An oxygen analyzer would be an added convenience but has not been justified by past experience. Safety Devices. I n addition to conventional spring-loaded pressure relief valves. the unit employs a number of specialized devices. Because a sudden drop in compressor suction pressure could occur if a relief valve opened or a large leak otherwise occurred, it is necessary to ensure that no air is pulled into the suction system through packing glands. This is accomplished by means of two Mercoid pressure switches. The first of these actuates a \varning device if suction pressure drops to around 15 instead of the normal 30 pounds per square inch gage at which operations are carried out. The second shuts down the compressor if pressure drops to 5 pounds per square inch gage. Using two Mercoid switches at different settings gives the operator time to correct the difficulty before the unit is shut down. Another warning device associated lvith the compressor is a Tektor liquid level detector on the suction knockout pot. The recycle gas frequently contains entrained liquid and, although this knockout is drained periodically, it is conceivable that during an upset in operations, large volumes of liquid could reach the compressor with possibly serious consequences. When the level reaches half way u p the knockout drum, an alarm is sounded. Temperature runaways during regeneration are not entirely preventable by keeping oxygen concentrations low. A loss of inert gas pressure, a plugged
INDUSTRIAL AND ENGINEERING CHEMISTRY
Table
I.
Hydrogenation Texas Gas Oil
of
West
(Cobalt' molybdate on alumina catalyst) Feed
Desulfurization, 70 Total liquid yield, vol. Yo Inspections on total liquid product Gravity, 'API Sulfur, wt. % Conradson carbon, wt.
Product 91 100.2
24.4 2.10
29.0 0.18
470 0.38 0.08 Distillation," O F. % off 20 771 596 50 788 725 80 926 860 ASTM D 1160 distillation a t 10 m m . ; temperature converted t o equivalent temperatures at 760 mm. by means of rliart [ (8, P. 431. Table
II.
Hydrogenation of Texas Crude Oil
West
(Cobalt molybdate on alumina catalyst) Feed P r o d u c t
Desulfurization, 70 94 Yields, vol. yo of feed C3 and lighter, wt. % 0.1 0.8 C1-430' F. 31.8 34.6 430-650' F." 24.0 30.1 650-1040° F." 31.0 27.6 1040' F.+Q 13.0 8.2 Inspections on total liquid product Gravity, OAPI 32.3 35.5 0.12 Sulfur, wt. % 2.04 a Distillations above 600' F. conducted under reduced pressure and terriperatuieb converted t o equivalent temperatures at 760 mm. h j means of chart [(S), p. 421
line, or a sudden surge in air pressure could result in a sudden increase in temperature and loss of a valuable batch of catalyst or damage to the reactor itself. An alarm on the %point temperature recorder used to monitor regeneralion, prevents such a n occurrence from going unnoticed. The alarm is set at l l O O o F., about 50" F. above the normal flame front temperature. All the devices described are connected to a Universal Panalarm "50" annunciator system which rapidly indicates to the operator the source of difficulty. Forced ventilation exhausts large quantities of air from the building for protection against hydrogen or hydrogen sulfide leaks. An easy-to-operate Mine Safety Appliances analyzer for hydrogen sulfide is furnished, and when an odor is detected, it can be used to determine if the atmosphere around the unit is safe. Data Processing
Each yield period on the pilot plant is subjected to complete and detailed material balance and component balance calculations. Yield periods are normally of 12 or 24 hours' duration and the workups require a great deal of computation.
H Y D R O G E N IN T H E P E T R O L E U M I N D U S T R Y Table 111.
Hydrogenation of West Texas Reduced Crude and Residuum (Cobalt molybdate on alumina catalyst) Reduced Feed Crude Feed Residuum Conversion of 1040’ F.+, vol. % 62 49 Desulfurization, % . 84 50 Yields, vol. yo of feed 1.1 2.0 Ca-and-lighter, wt. % ’ 5.8 0.7 12.6 Ca-430’ B. 9.0 12.5 28.1 43Oo-65O0 F.“ 650°-10400 1040’
F.“
56.0 30.8
49.7 11.5
9.0 91 .o
40.6 46.7
Inspections on total liquid product Gravity, OAPI 18.1 26.8 8.8 14.9 Sulfur, wt. yo 2.65 0.42 3.86 1.95 a Distillations above 600° F. conducted under reduced pressure and temperatures converted to equivalent temperatures at 760 mm. by means of chart [(a),p. 421. Table IV. Hydrogenation of Fluxed West Texas Asphalt (Cobalt molybdate on alumina catalyst) ProdFeed uct Conversion of 1040’ F.+, vol. % 38 Desulfurization, % 59 Yields, vol. % of feed &-and-lighter, wt. % 1.3 c4-430’ F. 43Oo-65O0 F a a 65O0-1O4O0 F.a 1040’ F.+a
6.2 14.0 30.8 51.4
Inspections on total liquid product Gravity, “API 7.2 13.0 Sulfur, wt. Yo 2.95 1.20 Naphtha insolubles, wt. % 7 . 7 6.5 a Distillations above 600’ F. conducted under reduced pressure and temperatures converted t o equivalent temperatures at 760 mm. by means of chart [(a),p. 421 .
In order to minimize personnel requirements, the entire work-up has been programmed for IBM Type 650 computing equipment available in Humble’s accounting department. All orifice meter and rotameter calibrations and temperature corrections for gravity and gas saturation are programmed. All conversion factors to provide for different units of various measurements are included. I t is necessary, therefore, only to record raw pilot unit data on the forms for keypunching. The calculation is divided into two parts. The first is a yield, material balance, and process conditions calculation requiring only data which are immediately available. The completed calculation can be made available within a n hour of the completion of a run and can be used to direct changes in operation. The second part of the computation provides a hydrogen balance, a sulfur balance, a balance for each light hydrocarbon component of the gas streams, and yield data on various liquid fractions. This calculation, dependent on gas analyses and distillation data, is delayed pending completion of these tests.
By programming options into the machine computation, it is possible to handle runs uniformly, regardless of how the unit is run. Recycle of gas and liquid, and use of different orifice plates, different feed stocks, or impure hydrogen as make-up are some of these options. Each alternative requires changes in computation procedure; but these changes are made automatically by use of the “logic” features of the Type 650 computer. Typical Results with Various Stocks
The pilot unit has been used primarily for studies in hydrogenating crude oils and residual stocks, though some operations have been conducted with gas oil. These operations will be described in detail in subsequent reports. Tables I, 11, 111, and I V summarize some of the operations with West Texas gas oil, West Texas crude oil, West Texas reduced crude and residuum, and West Texas asphalt. Gas Oil. Typical results with West Texas gas oil (Table I), indicate that this stock can be readily desulfurized to about 90% without excessively lowering the boiling range. The product, a high quality catalytic cracking feed stock, is suitable for producing low-sulfur gasoline blend stocks. In this type of operation, the catalyst maintains its activity unimpaired for a n indefinite period without needing regeneration. Crude Oil. I n hydrogenating crude oil (Table 11), the catalyst shows a steady decline in activity during operations, though its activity can be completely restored to that of the fresh catalyst by regeneration. The run represents approximately the first 20 hours of operation. Effective hydrogenation is still obtained after longer periods, but not to the same extent. I t appears that a crude hydrogenation process might require regeneration much more frequently than gas oil hydrodesulfurization. Hydrogenation of crude oil resulted in the production of distillate
fractions of about the same quality as those from sweet crudes, and in appreciable conversion of the residuum to distillate. Reduced Crude a n d Residuum. Hydrogenation of the bottoms from atmospheric distillation (reduced crude) and from further vacuum distillation (residuum) of West Texas crude are illustrated in Table 111. I n these operations also, the catalyst loses activity gradually, and the activity may be restored by regeneration. Here again the first 20 hours of operation are illustrated. Operations with ‘a residual stock have been conducted, with periodic regeneration, for over 3000 hours on oil; this indicates that a t least a 6-month catalyst life could be realized in commercial operations. With reduced crude and its residuum, good desulfurization was obtained and a large fraction of the residuum was converted to more valuable distillate products. Asphalt. Hydrogenation of the asphalt produced by conventional propane deasphalting of mixed refinery residua has been studied fairly extensively ( 7 ) (Table IV). I n asphalt operations, catalyst activity initially shows a fairly rapid drop, but then levels off and appears to remain constant for 500 or more hours. Results shown were obtained in operations after catalyst activity had leveled off. Acknowledgment
The authors wish to express appreciation to the management of the Humble Oil and Refining Co. for permission to publish this work. Special mention is due H. G. Corneil, G. R . L. Shepherd, G. T. Gwin, B. N. Hill, and G. A. Stankis for assistance in design and operation of the pilot unit and in carrying out experimental work. T h e efforts of research technicians, C. W. Bell and I. G. Thompson, are also deserving of acknowledgment. The analytical, mechanical, and operating personnel who participated in this work are too numerous for individual mention. literature Cited
(1) Gwin, G. T., Heinrich, R. L., Hoffmann, E. J., Manne, R . S , Meyer, H. W. H., Miller, J. R., Thorpe, C. L., IND.END. CIIEM. 49, 668 (1957). ( 2 ) McAfee, J., Montgomery, C. W., Summers, C. R., Jr., Hirsch, J. H., Horne, W. A., Proc. Am. Petroleum Znst. 35, Sect. 111, 312 (1955). (3) Maxwell, J. B., “Data Book on Hydrocarbons,” Van Nostrand, New York. 1950. (4) Roth, E. R., IND.ENG. CHEM.46, 1428 (1954). RECEIVED for review September 17, 1956 ACCEPTED January 14, 1957 VOL. 49, NO. 4
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