The Fluid Catalyst cracking process was developed by intensive pilot plant work to s u c c d u l commercial usage. The pilot plant equipment compribed a variety of sizes from small laboratory units to a semiplant scale unit of nominal 100-barrel-per-day feed capacity. This 100-barrel plant w4s relied on for the major part of the process data and engineering and equipment studies required for the commercial designs. A description of this unit i s given, as well as that of a smaller unit of 2-barrel-per-day capacity. The variotis engineering studies made are discussed and type of results obtained indicated. The original 100-barrel plant, which was used to pilot the first model of the commercial units, was later modified to a simpler design which has been incorporated in more recent full-scale plants. The results obtained on both designs have been translated to the commercial scale with singular accuracy.
Figure I. First Fluid Catalyst Plant a t Right, Two Newer Simplified Units a t Left
PILOT PLANT DEVELOPMENT OF FLUID CATALYTIC CRACKING L. E. Carlsmith and F. B. Johnson
-
ESSO LABORATORIES, STANDARD OIL COMPANY OF NEW JERSEY (LOUISIANA DIVISION), BATON ROUGE, LA.
HE Fluid Catalyst process has been developed from a laboratory scale to wide commercial usage during the past few years. According t o recent figures @ a total I),of thirty-four Fluid Catalyst cracking units have been built or are under construction. These plants are presently being used exclusively t o produce aviation gasoline and raw materials for the war program. After the war these units mBy be used to produce high-quality motor gasolines with a considerable increase in feed capacity. Previous articles ( I , @ have discussed the Fluid process in considerable detail. These papers described the first commercial plant which was designed before the entrance of the United States into the war and was planned for peacetime production of premium motor fuels. Engineering and design data were based on a background of experimental and semiplant experience in continuous Fluid Cracking as well as in intermittent ked-bed operations. The first commercial plant was designed by the Standard Oil Development Company and placed in operation a t the Baton Rouge refinery of the Standard Oil Company of New Jersey in the early part of 1942. This installation was followed by the design and construction of a simplified type of plant which offered greater
flexibility in operation. Figure 1shows a plant of the original design and two of the improved, simplified type. The purpose of this paper is to trace the development of the Fluid process through the laboratory, pilot plant, and semiplant stages, and to describe the equipment used in this development. The 100-barrel-per-day Fluid Catalyst unit has contributed a large amount of the process and engineering data required for this development. DEVELOPMENT OF COMMERCIAL SCALE UNITS
The Fluid Catalyst operation represents a new industrial method of handling solids and controlling the temperature of gaseous or vapor reactions. Figure 2 presents the principle of the process as applied in catalytic cracking. Catalyst from a standpipe on the regeneration section is mixed with oil vapors which carry it up into the reaction vessel of rather large cross section. The catalyst leaving the reaction vessel is separated from the cracked vapors in conventional cyclone separators, and the cracked vapors pass on to fractionation equipment. The separated catalyst is collected in a hopper and allowed to flow by grav451
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eration stages separately. Later, a small pilot unit feeding approximately 2 barrels per day of gas oil was used t o study feed stocks and catalysts. A larger unit with a feed capacity of 100 barrels per day was built to study engineering and equipment variables arid to confirm process and catalyst data observed in thci smaller units. This larger unit was also used to supply large quantities of gasoline for full scale evaluation, particularly in avia tion gasoline blends. I n addition to the pilot unit equipment, numerous tests were' made to study particular phases of the process. These studies included the temporary installation of a catalyst circulating system 150 feet high, on the side of a fractionation tower which wat under construction for other purposes. This equipment was used for about one month to obtain the necessary data. Other equipment included a circulator system where visual observation of catalyst flow could be made through a window equipped with a windshield wiper and illumination on the inside of the vessel. Numerous glass models were made and used for visual observation and demonstration of the principles involved. These pieces of equipment were especially useful in demonstrating the process to operating personnel and in training new workers. ~
OIL FEE::
I ’ Figure 9 .
Catalyst Flow in Fluid Catalyst Cracking
ity down through a standpipe and slide valve at controlled rates. a i r is introduced below the slide valve, and the air-catalyst mixture is contacted in the regenerator for the desired time to effect pxidation of the carbonaceous material formed in the reaction cycie. It has been found possible by suitable adjustment of gas or vapor velocities to build up relatively high concentrations of solids where desirable-for example, in the reactor or regenerator or in the standpipes. The densities which can be attained in vessels are functions of catalyst feed rate, composition, and particle size as well as of vapor or gas velocity. The quantity of catalyst remaining in the vessel as well as the catalyst passed through the vessel may, therefore, be adjusted independently. This type of contacting gives a solid-gas mixture which is very turbulent and resembles in many aspects a boiling liquid. I n addition to excellent mixing, this process allows for adjustment of time of contact of both catalyst and vapor in the vessel, both of which are important in obtaining the desired results. The pressures required to effect the flow of ratalyst through the system are obtained in the standpipes where the density of the catalyst is relatively high due to the small amount of aeration vapor present. Prior to the development of the above principles as applied in Fluid Catalyst cracking, several other processes were tried for transferring and contacting the catalyst in the reaction and regeneration cycles. The choice of the principles described was based mainly on ease of operation and on elimination of moving mechanical parts. Other methods investigated for transferring the catalyst included the use of bcrew pumps and lock hopper systems. Although operable, these devices were not so satisfactory as the standpipe system, either as to mechanical repairs or ease of operation. The use of other types of reactors was studied also, including smaller pipes and coils, but these did not allow so much flexibility and required more materials than the type of equipment chosen. The choice of the design has been justified in that operation of several of the Fluid units have extended over sixmonth periods and then have been taken off stream voluntarily for routine mechanical inspection. Design factors involved in the development of this process included items such as type of catalyst, feed stocks, operating conditions, and yields and quality of products. Engineering and equipment studies included the mechanics of catalyst flow, catalyst recovery, methods of avoiding erosion and attrition, heat transfer data, control and capacity of the regenerator and reactor, $tripping of spent catalyst, and the general know-how in any new process. The choice of pilot plant equipment to study the process involved first a study in small equipment of the reaction and regen-
CRACKEDPRODUCTS
POROUS q..zkTER
POROUS
FILTER
COMBUSTION
pb G A S E S
SEPARATOR - REGENERATED
CATALYST HOPPER
REGENERATED
AU TOMATI CALLY CONTROLLED /SLIDE VALVE
Figure 3.
Fluid Catalyst Pilot Unit, with a Capacity of 2 Barrels per Day
I n addition to the tests on the pilot units, numerous tests were made on smaller equipment to develop catalysts and test the catalysts used in the larger units for contamination and activity. Among the first pilot units which included both reaction and regeneration sections was the so-called 2-barrel-per-day unit; this comprised the general principles used in the plant desiprr (Figure 3). The unit included a 2 inch X 20 foot reactor, and a 4 inch X 20 foot regenerator. Oil was pumped through a vaporizing coil contained in a lead bath (not shown) and then mixed with regenerated catalyst. The mixture flowed into the reactor where the cracking reaction was controlled by the vapor throughput, catalyst rate, and temperature. The cracked products plus catalyst leaving the top of the reactor were passed through a. cyclone separator where catalyst was separated. The cracked oil vapors were then passed through a porous filter to remove the last traces of catalyst; the oil was then condensed and separated from the noncondensable gases. The catalyst from the filter was returned to the system. The liquid and gases were separated, pressured to 80 pounds by a small pump and a compressor, and then separated again. The final liquid, which contained most o! the gasoline components, was stabilized and fractionated to the desired specifications. The spent catalyst collected in the hopper was allowed to flow downward through the 1.5 inch x 40 foot spent catalyst stand-
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May, 1945
w x
Figure 4.
Fluid Catalyst Unit with a Nominal Capacity of 100 Barrels per Day
453
day unit, but difficulties with both of them were satisfactorily overcome. The 100-barrel-per-day unit was constructed primarily to obtain engineering and process data for designing commercial units. This unit is of sufficient size and is instrumented to allow for complete coverage of.process and engineering data. This unit has had an important part in the development of the commercial units, and has operated successfully from the beginning. Catalyst flow and control are smoother than in the smaller units. The feed rate may be varied considerably, but 100 barrels per day is the nominal capacity. The unit is completely equipped with feed preparation, product recovery, fractionation, and storage facilities. Figure 4 is a flow diagram of the reactor and regenerator section. .The flow is essentially the same as in the 2-barrel unit except that a n additional circuit has been added whereby regenerated catalyst may be recirculated to the regenerator through a heat exchanger. This allows an additional control of the temperature in the regenerator, Various sizes of reactor and regenerator have been tried in studies of process variables. Catalyst flows are maintained by pressure built up in the standpipes, the rates being controlled by the slide valves. The plant was equipped with facilities for feed preparation as well as for product recovery. Figure 5 shows some of the equipment available. A heater, flash tower, and superheater are available for the feed stock. Any one or all of these items may be bypassed as desired. The product recovery system includes a cooler, low-pressure separator, pumps and compressor, high-pressure s e p arator, stabilizer, and fractionation tower. A tank farm consisting of fourteen tanks with a total capacity of 400,000 gallons is available for storage of feed and product. An electrical precipitator is used to recover fines leaving the regenerated catalyst cyclones. This material is returned to the unit through the recycle line to the regenerator. An oil scrubber, not shown, is used to recover fines leaving the reactor cyclones. This material may be returned to the unit with the feed. The reactor, regenerator, and standpipes are enclosed in a flue gas jacket to take care of heat losses. The remainder of the unit outside the jacket is heavily insulated.
pipe. Steam or inert gas introduced a t points in the standpipe displaced any hydrocarbons accompanying the catalyst. The “stripped” catalyst flowed through an automatically controlled slide valve, was mixed with regeneration air, and flowed into the regenerator where, under proper time and temperature conditions, the carbonaceous materials were removed. The combustion gases plus regenerated catalyst were separated in a cyclone separator; final traces of catalyst were removed in a porous filter. The regenerated catalyst was collected in a hopper, flowed down a 1.5 inch X 40 foot standpipe, and was picked up by the oil vapors as previously described. The entire unit was electrically heated to provide for the heat losses attendant to the use of this size equipment. The various circuits were controlled through the use of small transformers and resistors. The quantities of feed stock, catalyst, and air normally used for this unit varied, depending on the severity of cracking desired. Nominal oil feed rates of approximately 2 barrels per day were employed, GAS and air rates of 150-200 cubic TO HOLDER Feet per hour could be used. t----+-The yields of products from the unit were obtained with good accuracy throughout the comct plete range of hydrocarbons P from hydrogen in the gas to carbon burned. Material balI FINES ances of 99-100% were norRETURN LOW-PRESSURE mally obtained. The yields of TO UNIT SEPARATOR products have correlated well with large plant performance, I----- --and consequently this unit has I I been useful in predicting the I utility of various feed stocks, catalysts, and operating conditions proposed for commercial operations. This unit has been limited in usefulness in obtaining engineering d a t a because of i t s small size RECYCLE and comparatively large heat LINE EATER EATE losses. Catalyst flow control and dust recovery were the AIR AIR TO factors influencing operability STOR A G E B~TOMS during the initial stages of operation of the 2-barrel-perFigure 5. 100-Barrel Fluid Catalyst Unit with Auxiliary Equipment
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Figure 6. 1 00-Be rre I- p er- Da y Fluid Catalyst Unit, Electrical Precipitator Above at Left, and a General View Is Shown Below
air, or steam as desired) is injected to prevent catalyst from getting in the lines and meter. Catalyst flow rates are controlled by automatically operated slide valves. These valves were fabricated locally and were designed to minimize erosion which occurs a t points of high velocity unless properly allowed for. Automatic safety shutoff valves are included to prevent hydrocarbons from entering the regenerator or air from entering the reactor in the event of an upset in the unit. The unit is quite flexible, being suitable for processing feeds from light naphthas to reduced crudes, vapor or liquid injection, high or low temperatures, and a variety of operating conditions covering a wide range of catalyst and feed rates. Instrumentation is complete throughout the unit, with automatic control being applied wherever i t seems desirable. Facilities are available for measuring catalyst levels and densities in the various vessels and standpipes so that proper design can be predicted for the large plants. PROCESS, ENGINEERING, AND EQUIPMENT STUDIES
I n the design of large scale equipment from laboratory and pilot plant data, it is often necessary to use rather wide extrapolations of the available results to predict plant performance. This extrapolation was unusually large when designing plants with the capacity of the first Fluid Catalytic cracking units. Figure 7 is a simplified flow diagram of the first commercial design. Table I compares the sizes of the rcactor and regenerator of the first commercial unit with the 100-barrel and 2-barrel plant vessels.
This type of extrapolation may be carried through Lo thc sizes of the other vessels, lines, valves, etc., in the units, Tho principal problems in the extrapolation to large scale design included assurance of the same product distribution, cracking rate, and carbon burning rate. The proper mixing in the large vessels was also important. The type of catalyst flow in the large standpipes (26-inch diameter compared to 4-inch in the 100-barrel plant) gave some concern. T o assure proper cracking and regeneration i t was of utmost importance to know what concentration of catalyst would be obtained in the vessels of the large unit. It was gratifying to find good agreement between results in the 100-barrel-per-day plant and results in the smaller units. This comparison held for process results, catalyst flow characteristics, and catalyst concentrations in the various vessels and standpipes. Successful correlation of factors involving catalyst concentrations and agreement with visual results in an allglass apparatus also gave more confidence in extrapolation of
Table I Reactor Diameter Height Regenerator Diameter Height
Commercial Plant
100-Rairel/ Day Unit
Day Unit
15 it. 2s it.
12 in. 31 f t .
2 in. 2 0 ft.
19 5 ft. 37 ft.
22 in. 31 f t .
4 in. 20 f t .
2-Barrel/
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equipment, ( d ) determination of catalyst rates, (e) catalyst losses and attrition, ( f ) rates of burning in the regenerator, (9) oxygen requirements and heat of combustion in regeneration, (A) stripping of spent catalyst, ( i )recovery of PRODUCT catalyst by oil scrubbing, and 0') cyclone and FRACTIONATOR electrical precipitator efficiencies. These and numerous other problems were studied, and the R E G EN E R A TO R necessary data for plant design determined in the 100-barrel plant prior to operation of the large unit. Many of these problems were new in the field of petroleum refining. As mentioned previously, the newer commercial units employ a simplified principle of design. The 100-barrel plant was modified to the new principle soon after the design data for the &st plant were obtained. It became Figure 7. Fluid Catalyst Cracking Plant apparent that further catalytic cracking units were necessary and simplifications in design could be made. It was necessary a t that time, however, that engineering and process data for design changes results to commercial scale. This glass apparatus which was conbe obtained in a short time t o allow for inclusion in the new structed of 6-inch glass tubing was used to study aeration and plants. mixing of various types of powders. It was found that particle size and particle size distribution both affected the aeration characteristics of catalysts. The effects of particle size, absolute density, and gas velocity on Fluid density were studied. Tests were also made to determine settling rates of the various powders to aid in the design of hopper shes. To check further the process data and hindered settling catalyst concentrations, four reactors having various shape factors were studied in the 100-barrel plant (Figure 8). Comparison of results with these various reactors gave further assurance that the extrapolation of results on the 100-barrel unit to plant design was sound. The product distribution and quality obtained in the commercial unit have been compared (3) with that of the 100-barrel plant; it was shown that good agreement existed. This comparison may be extended to include the 2-barrel-per-day unit also as shown in Table 11. VENT
Table II Rerotor niae Feed stock A.P.I. 60% point,' a F. Yields on feed Gasoline (10 lb. Reid vapor pressure), vol. % Exoess butane. vbl. Gasoline (100% vol: % Gas od, vol. % Dry gas wt. % Carbon,'wt. %
21,
Commercial Plant 16 ft. X 28 ft. 30.6 690
100-Barrel Unit 16 in. X 20 ft. 31.7 680
2-Barrel Unit 2 in. X 20 ft. 31.0 680
42 0 7.6 49,6
45.0 4.7
46.0 6.2
49.7 60.0 6.0 2.8
60.2 60.0 4.2 3.2
46.0
86 93
60.4 46.0 87 75
59.6 46.0 84 77
79.2 92.9
79.7 92.0
79.6 92.4
97.3
97.0
97.6
60.0 6.2 2.8
Figure 8.
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Motor gasoline properties 60.3
gal.
Reactors Used in 100-Barrel Fluid Catalyst Unit
The new design offered considerably more flexibility, and successful operation was observed from the start. Both the general mechanical performance and the product distributiori were satisfactory. The basic catalyst flow data obtained on the original system were found to be applicable with only minor modificrttions. Process data were in agreement with the original type results, and catalyst requirements to maintain a given severity of cracking were also similar. LITERATURE CITED
.
These results show excellent agreement among the three units, indicating that interpolation of the results between units is justifiable. Other equipment studies included extensive determinations of factors influencing the following: (a) heat transfer coefficients in fluid systems, (b) pressure drop data, (c) erosion of lines and
(1) Murphree et al., IND.ENQ. CHBIM.~ 35, 623, 768 (1943). (2) Murphree, Fischer, Gohr, Sweeney, and Brown, Oil Gas J . , 42, No. 28, 37 (1943). (3) Oil Gas J . , 42, No. 49, 167 (1944). PREBIDNTED as part of the Symposium on Cstalyaia in the Petroleum Indurtry before the Division of Petroleum Chemistry nt the 108th Meeting of the AMERICAN CHEMICAL SOCIETY in New York, N. Y.
