WO1994014536A1 - Tube de tirage destine a la repartition d'un catalyseur - Google Patents

Tube de tirage destine a la repartition d'un catalyseur Download PDF

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Publication number
WO1994014536A1
WO1994014536A1 PCT/US1993/012120 US9312120W WO9414536A1 WO 1994014536 A1 WO1994014536 A1 WO 1994014536A1 US 9312120 W US9312120 W US 9312120W WO 9414536 A1 WO9414536 A1 WO 9414536A1
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Prior art keywords
draft tube
catalyst
gas
tube
slurry
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PCT/US1993/012120
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English (en)
Inventor
Larry E. Pedrick
Charles H. Mauldin
William C. Behrmann
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ExxonMobil Technology and Engineering Co
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Exxon Research and Engineering Co
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Priority to AU58004/94A priority Critical patent/AU5800494A/en
Publication of WO1994014536A1 publication Critical patent/WO1994014536A1/fr
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
    • B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
    • B01J8/224—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid the particles being subject to a circulatory movement
    • B01J8/226—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid the particles being subject to a circulatory movement internally, i.e. the particles rotate within the vessel
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
    • C07C1/06—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen in the presence of organic compounds, e.g. hydrocarbons
    • C07C1/063—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen in the presence of organic compounds, e.g. hydrocarbons the organic compound being the catalyst or a part of the catalyst system
    • C07C1/066—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen in the presence of organic compounds, e.g. hydrocarbons the organic compound being the catalyst or a part of the catalyst system used for dissolving, suspending or transporting the catalyst

Definitions

  • This invention relates to a process and apparatus for uniformly distributing catalyst in a slurry phase reactor by using a substantially vertical draft tube means, open at both ends, fully immersed in the slurry in said reactor and preferably utilizing a lifting gas injected at or substantially near the bottom of said draft tube means.
  • Catalyst is drawn up the draft tube means from near the bottom of said reactor under the influence of the lifting gas and ejected from the top of the draft tube means at or below the top of the slurry phase in such reactor.
  • Catalyst rejuvenation can be accomplished using the draft tube means by fitting the bottom of said tube with synthesis gas deflector means and using a rejuvenation gas such as a hydrogen containing gas.
  • draft tube means will be referred to simply as draft tube or draft tubes, unless otherwise indicated.
  • Slurry reactors are well known for carrying out highly exothermic, three phase, catalytic reactions. Usually called “bubble columns” these reactors have a liquid phase in which solid catalyst particles are dispersed or held in suspension by a gas phase bubbling through the liquid phase, thereby creating a slurry. These reactors provide improved heat transfer characteristics for the exothermic reaction, with the bubbling gas maintaining the catalyst as a disper ⁇ sion in the liquid phase.
  • Bubble column reactors typically have a multiplicity of tubes suspended within a shell-type housing, the tubes being filled with a heat transfer medium, e.g., boiling water, which absorbs the heat generated by the exothermic reaction occurring on the shell side of the tubes in the main body of the housing.
  • a heat transfer medium e.g., boiling water
  • the reactor can be of a similar multi-tube design housed in a common shell-type housing as previously described but wherein the gas and liquid are passed through the multiple tubes which function as the reactor tubes, with effluent being removed from the upper ends of the reactor tubes and heat transfer fluid being passed through the space along the outside surfaces of the reactor tubes.
  • the reactor tubes can be either multiple individual tubes with spaces between adjacent tubes, or multiple bundles of tubes with spaces between adjacent bundles of tubes.
  • the entire cross section of the reactor vessel may have a plurality of shafts disposed within it, the bottoms of said shafts being located above the reaction gas inlet but extending a distance above the top surface of the reaction slurry into the gas disengaging spaces so as to create multiple single columns of standing, non-circulating liquid with catalyst suspended and dispersed in said standing liquid.
  • the reaction zone therefor has multiple single columns, said columns having a common bottom reaction gas introduction zone and a common upper gas disengagement space.
  • additional tubes can be inserted into or between the multiple single columns to function as heat exchangers.
  • Figures 1, 2 and 3 present in graphical form the results of cold mock-up draft tube runs comparing slurry distribution in vessels with and without the use of added lift gas.
  • Figure 4 presents axial catalyst distribution comparisons at specific measurement moments before and during draft tube operation of an operating bubble column reactor (4 draft tubes and one rejuvenation tube in use).
  • Figure 5A presents catalyst activities and Figure 5B shows hydrogen rates in the continuous catalyst rejuvenation.
  • Figure 5A presents the efficacy of using draft tubes as continuous catalyst rejuvenation tubes using hydrogen as rejuvenating lift gas.
  • Figures 6A, B and C present three pairs of temperature profiles comparing temperatures inside the rejuvenator tube with temperature in the reactor slurry outside the rejuvenator tube at different temperatures in the reactor slurry.
  • Catalysts used in slurry phase reactors are circulated and uniformly distributed throughout the slurry phase reactor by use of a substantially vertical draft tube, open at both ends, fully immersed in the reaction slurry, the bottom of which draft tube preferably extends to near the bottom of the slurry reactor and the top of which preferably extends to just under the top of the slurry phase, preferably utilizing a lifting gas injected into the draft tube at or substantially near the bottom of said draft tube.
  • the draft tube is sized in terms of length and diameter so as to insure that flow in said tube is at or above that flow which provides catalyst lift.
  • Velocity of the gas in the draft tube is such that the slurry density in the draft tube is less than the slurry density in the overall reaction vessel.
  • Superficial gas velocities in the tube therefore, are in the range of at least 0 to 40 times the superficial gas velocities of the gases in the reactor vessel itself, preferably 2 to 20 times, more preferably 3 to 15 times the superfi ⁇ cial gas velocities of the gases rising in the reactor vessel.
  • Superficial gas velocities of the gas injected into the tube can range down to zero times the superficial gas velocities of the gases in the reactor vessel itself.
  • the volume fraction gas in the gas-liquid-solid slurry can be greater than that in the reactor, for the gas holdup depends upon the slip velocity between the gas and the liquid-solid slurry.
  • the draft tubes of the present invention are sized so as to fit within the reactor vessel and are also sized so as to not inter ⁇ fere with the fluid dynamics of the reactor vessel nor with the normal synthesis gas flow within such vessel.
  • These draft tubes occupy, on a cross sectional area basis, as measured in the horizontal plane through the vertical draft tubes, a total of from 0.2 to 10% of the cross sectional area of the reaction vessel, preferably from 0.40 to 8%, more preferably from 0.4 to 5% of the cross sectional area of the reaction vessel.
  • multiple tubes will be employed as to insure maximized catalyst circulation. When multiple tubes are employed no single tube will constitute more than 50%, preferably more than 30%, more preferably more than 10% of the total cross sectional area of the draft tube array.
  • Narrower diameter tubes are preferred so that fluid dynamics are more easily controlled and so that excessively high superficial gas velocities to achieve adequate lift can be avoided.
  • tubes having diameters of less than 12 inches, preferably less than 8 inches, more preferably less than 6 inches will be employed in commercial hydrocarbon synthesis vessels.
  • the length of the tube is important, since when all other conditions are constant it is believed the amount of slurry pumped by the lift tube increases as length is increased.
  • the length of the lift tube will be as long as the reactor design allows, i.e., approximately equal to the slurry height in the reactor.
  • the diameter will be set by flow regime considerations in the lift tube and by the amount of slurry that is to be pumped.
  • Successful lift tube operation depends upon the density of the gas-liquid-solid slurry inside the lift tube being less than the density of the gas-liquid-solid slurry in the reactor surrounding the lift tube. The greater the difference is in these two densities, the higher is the velocity in the lift tube.
  • the density inside the lift tube depends upon the flow regime therein, and that in turn depends upon the lift tube diameter and gas velocity.
  • An acceptable gas velocity range in a small diameter tube may be different from that in a larger tube, because the differences in densities between the lift tube and reactor slurries will be different for different lift tube diameters, at a given difference in velocity between the lift tube and reactor.
  • the upward velocity of the fluid in the lift tube must be greater than the settling velocity of the solids, otherwise the solids will not be carried up the lift tube.
  • Example 1 This was observed in the mock-up of Example 1 (see Figure 3), discussed in greater detail later, when the gas rate was increased from 0.4 to 0.8 CFM (superficial gas velocity in the tube increased from 46 to 92 cm/sec). The catalyst dispersion was poorer at the higher velocity.
  • Gases which may be used as lifting gases include gas feed, tail gases, volatile liquid product, light gaseous hydrocarbons, inert gases such as nitrogen, argon etc., steam, in general, any gas which can be easily disengaged from the product, and gases discharged from the reactor and recycled to the draft tubes.
  • Another gas which can be used as lifting gas is hydrogen or hydrogen rich gas which may contain inerts such as CH4, light hydro ⁇ carbons (e.g., C2-C10) etc., but which is substantially free of CO or other hydrocarbon synthesis feed gases which are reactive with hydrogen.
  • inerts such as CH4, light hydro ⁇ carbons (e.g., C2-C10) etc.
  • the draft tube can be used as a catalyst rejuvenation zone insofar as it has been discovered that hydrocarbon synthesis catalyst which has undergone short term reversible deactivation in the course of the HCS process can be rejuvenated in the presence of the hydrocarbon synthesis product using hydrogen, said catalyst rejuvenation occurring under the conditions of temperature and pressure similar to those employed for the hydrocarbon synthesis.
  • the use of draft tubes for catalyst rejuvenation is the subject matter of copending application USSN 994,215 filed even date herewith in the names of Behrmann, Mauldin and Pedrick.
  • Catalyst regeneration using hydrogen or hydrogen containing gas is the subject matter of copending application USSN 949,934 Filed 9/24/92 in the name of W. N. Mitchell.
  • the draft tube is fitted at its lower end with gas deflecting means, such as a bubble which curtails entry into the tube of synthesis gases yet promotes and facilitates entry of additional liquid and catalyst (slurry).
  • gas deflecting means such as a bubble which curtails entry into the tube of synthesis gases yet promotes and facilitates entry of additional liquid and catalyst (slurry).
  • the superficial gas velocity in the rejuvenation tubes is in the range of at least 0.2 to 40 times, preferably 0.5 to 20 times, more preferably 3 to 15 times the superficial gas velocities of the reaction gases rising in the reactor vessel itself.
  • the amount of hydrogen flow into the tube when used as a rejuvenation tube can be throttled such that at the beginning of the rejuvenation step flow is low enough so that minimal catalyst is displaced out of the tube through the open top. Flow is maintained at this level for a time sufficient to effect catalyst rejuvenation after which hydrogen flow is increased to lift the catalyst out of the tube to permit a fresh charge of additional catalyst and hydrocarbon synthesis product to be drawn into the tube.
  • hydrogen flow rate is adjusted so that catalyst is continuously being drawn into the tube from the bottom in response to the hydrogen lifting flow; catalyst residence time in the tube is sufficient to achieve the rejuvenation of the catalyst by the time any particular catalyst particle has completed its journey to the top of the tube for discharge back into the main reactive slurry.
  • the extent of the rejuvenation reaction occurring in the continuous mode using the draft tube as the rejuvenation vessel can be monitored by thermocouples placed inside the tube.
  • the measured temperature profile in the rejuvenation tube is compared with the temperature profile in the reactor slurry surrounding the rejuvenation tube, corresponding thermocouples inside and outside the tube being at equivalent heights above the bottom of the reaction vessel.
  • the difference in temperature between the rejuvenation tube and the reactor slurry is the temperature rise in the rejuvenation tube, which can be used as a measure of the extent of the rejuvenation reaction occurring there.
  • the efficacy of continuous rejuvenation in the draft tubes depends upon the temperature level in the rejuvenation tube which is generally controlled by the temperature in the reactor slurry itself. Rejuvenation at higher temperatures is preferred.
  • the amount of hydrogen passed to the tube in the rejuvena ⁇ tion mode so as to effect sufficient residence time depends on the degree or level of catalyst deactivation, the concentration of deacti ⁇ vating species in the wax present in the slurry, the diameter of the tube, are items all either within the control of the practitioner or dictated by the conditions of the synthesis reaction itself.
  • control of hydrogen flow rates to the rejuvenation tube is left to the individual practitioner to set in response to the specific conditions encountered.
  • the rejuvenation tube can occupy from 0.2 to 10% of the cross sectional area of the reaction vessel .
  • the degree of catalyst rejuvenation in the rejuvenation tubes can be controlled by independently controlling the rejuvenation temperatures in the rejuvenation tube as compared to the temperature of the surrounding reaction slurry. In many instances this involves conducting the rejuvenation at temperatures higher than those of the surrounding reactor.
  • This control of the temperature in the rejuvenation tubes can be achieved either by increasing the residence time in the rejuvenation tube so as to take advantage of the exothermic nature of the rejuvenation process itself and thereby increase the temperature, by deliberately introducing heat into the rejuvenation tube, by a combination thereof, or by introducing a cooling medium into the rejuvenation tube, thereby lowering the rejuvenation temperature.
  • the temperature in the rejuvenation tube should be high enough to react out any entrained and dissolved CO in the lower part of the rejuvenation tube and react deactivating species in the wax and on the catalyst, yet low enough to avoid excessive methane production and hydrolysis of the wax.
  • the rejuvenation temperature in the rejuvenation tubes to achieve effective catalyst rejuvenation may range from about 400 to 500 ⁇ F, preferably about 420 to 480 ⁇ F and more preferably about 440-470"F.
  • the lower temperatures are effective in those instances in which the catalyst and/or wax contain a minimum of deactivating species. Higher temperatures are needed in those instances when the catalyst and/or wax containing higher levels of deactivating species.
  • the rejuvenation tube be fitted with insulation means, thus trapping the heat in the rejuvenation tube.
  • This insulation means can take the form of a coating of material of low heat transfer coefficient, such as ceramic.
  • the rejuvenation tube can be surrounded by a larger diameter tube with the annular space between the rejuvenation tube and the larger diameter tube surrounding it acting to isolate it from the reaction slurry.
  • heat or cooling can be introduced into the rejuvenation tube by means of a separate, independent, controllable heating or cooling means source, such as a steam heat exchanger or electrical heater, run partially or totally up the interior of the rejuvenation tube.
  • a separate, independent, controllable heating or cooling means source such as a steam heat exchanger or electrical heater
  • Heating it would be preferably to provide the maximum heat exchange near the bottom of the rejuvenation tube to provide the maximum benefit in increasing the rate and extent of rejuvenation.
  • the heat exchanger extending totally up the inside the rejuvenation tube might serve the purpose of heating the contents of the rejuvenation tube in the lower region and mitigating the temperature rise (i.e. cooling) in the upper region, should reaction rates and heat of reaction be high enough to cause the temperature in the upper regions to rise to undesirable levels.
  • catalyst distribution and rejuvenation will be practiced simultaneously using the same draft tubes.
  • some of the tubes may be fed rejuvenating gas at a high enough superficial velocity for the purpose of accomplishing both catalyst rejuvenation and redistribu ⁇ tion.
  • the draft tubes are located in the reaction process zone so as to produce uniform catalyst redistribution through the reaction zone and mitigate or eliminate areas of catalyst stagnation and overcome the natural settling tendency of the catalyst that creates a higher concentration of the catalyst in the bottom of the reactor than at the top.
  • the lower ends of the draft tubes will be placed at or near the bottom of such reaction zones in those areas of low or minimal normal circulation in said zone, preferably from 0.1 to 1.0 foot from the bottom of the reaction zone, more preferably from 0.1 to 0.5 foot from the bottom, most preferably from 0.1 to 0.25 foot from the bottom of the reaction zone.
  • Such stagnant zones exist in bubble column reactors wherein the catalyst is on the shell side of the tube in a shell and tube reactor.
  • Bubble column synthesis gas is introduced into such reactor by gas introduction means such as bubble caps at the bottom of the reactor. Due to fluid dynamics stagnant zones are present at the bottom of the reactor surrounding the gas introduction means. Catalyst accumulating in those zones is not circulated or lifted by the incoming synthesis gas; such catalyst in effect is lost to the catalytic process. With more advanced gas introduction/distribution means such as multiple cone distributors, stagnant zones of uncirculating, standing catalyst are avoided, but poor catalyst distribution throughout the slurry remains a problem.
  • the catalyst maldistribution problem revolves around the axial gradient of catalyst concentration. While the energy impacted , by the gas bubbles tends to disperse the catalyst, gravity causes the catalyst to settle. The degree of dispersion increases with increasing gas velocity, increasing liquid velocity in the upward direction, increasing liquid viscosity, increasing liquid density, and decreasing particle size. For practical conditions encountered in commercial vessels, there is still a large gradient of catalyst concentration from the bottom to the top of the reactor even when multiple cone distributors are used so that there are no stagnant standing zones. It is this gradient which is flattened using the draft/rejuvenation tubes.
  • catalyst is carried by the rejuvenating gas from the high concentration zone in the bottom of the reactor to the low concentration zone at the top of the reactor. Gravity slowly pulls the catalyst particles back to the bottom of the reactor where they are again pushed up and lifted to the top.
  • Siting draft tubes around the e.g., bubble cap in such reactors would result in a siphoning of the catalyst up from the static zone into the draft tube in response to the suction created in the draft tube and the discharge of such formerly static catalyst out the top of the draft tube back into the main reactive slurry mass.
  • the present invention is of use in hydrocarbon synthesis processes wherein gas, i.e. hydrogen and carbon monoxide, in a ratio ranging from about 0.5 to 4, preferably 0.7 to 2.75, more preferably about 0.7 to 2.5, or other synthesis feed such as methanol , is injected at superficial gas velocities ranging from about 1 to 20 cm/sec through gas injection means such as a bubble cap gas injector grid or sparger into the main reaction zone in which is located hydro ⁇ carbon synthesis product (i.e. hydrocarbon liquids or liquid wax) and catalyst.
  • hydro ⁇ carbon synthesis product i.e. hydrocarbon liquids or liquid wax
  • the gas bubbles up through the reaction zone in contact with the catalyst in the hydrocarbon liquid and is converted into hydrocarbon product.
  • the rising synthesis gas supplies the energy to maintain the catalyst as a dispersion in the hydrocarbon liquid thereby creating a slurry.
  • Reaction takes place wherever there are synthesis gas, catalyst and suitable reaction conditions, which include pressures ranging from 1 to 100 atmospheres, preferably 10 to 50 atmospheres, more preferably about 15 to 40 atmospheres, and temperatures ranging from about 175 ⁇ C to about 450 ⁇ C, preferably about 175°C to 420 ⁇ C, more preferably about 175 ⁇ C to 300 ⁇ C.
  • the slurry phase liquids in which the catalyst is dispersed are those that are liquid at reaction conditions, generally inert, and a good solvent for synthesis gas.
  • the slurry is the product of the reaction and contains C5+ hydrocarbons, usually C5-C100 hydrocarbons.
  • the slurry liquid comprises primarily high boiling paraffins with small amounts of primary and secondary alcohols, acids, esters, or mixtures thereof. Sulfur, nitrogen, phosphorus, arsenic, or antimony heteroatoms are to be avoided since these tend to poison the hydrocarbon synthesis catalyst.
  • slurry liquids examples include dodecane, tetradecane, hexadecane, octadecane, tetracosane, and the like.
  • Preferred slurry materials are Fischer-Tropsch waxes and C16-C18 hydrocarbons.
  • the concentration of solids, including catalyst, in the slurry phase is usually about 10-50% by weight, preferably 20-40 wt% solids.
  • the hydrocarbon synthesis reaction is highly exothermic and the heat of reaction is removed by a heat transfer material which is either circulating on the shell side of a shell and tube reactor when the reaction takes place in the tube, or through the tubes when the reaction takes place on the shell side.
  • the heat transfer material can be any material having a high heat capacity, whether or not it undergoes a phase change.
  • the heat transfer fluid is boiling water.
  • the catalyst employed in the hydrocarbon synthesis process is any catalyst known to be active in Fischer-Tropsch synthesis.
  • Group VIII metals, whether supported or unsupported, are known Fischer-Tropsch catalysts. Of these, iron, cobalt and ruthenium are preferred, particularly iron and cobalt, most particularly cobalt.
  • a preferred catalyst is supported on an inorganic refractory oxide selected from Groups III, IV, V, VI, and VIII of the Periodic chart of the elements.
  • Preferred supports include silica, alumina, silica-alumina, the Group IVB oxides, most preferably titania (prima ⁇ rily in the rutile form), and generally supports having a surface area of less than about 100 m2/gm, preferably 70 m2/gm and less.
  • the catalytic metal is present in catalytically active amounts, usually about 1-100 wt% (the higher concentrations being typical when iron based catalysts are employed), preferably 2-40 wt%, more preferably about 2-25 wt%.
  • Promoters may be added to the catalyst and are well known in the Fischer-Tropsch catalyst art. Promoters can include ruthenium (when it is not the primary catalytic metal), rhenium, hafnium, cerium, and zirconium, and are usually present in amounts less than the primary catalytic metal (except for ruthenium which may be present in co-equal amounts), but the promoterrmetal ratio should be at least about 1:10. Preferred promoters are rhenium and hafnium. Useful catalysts are described in U.S. Patents 4,568,663; 4,663,305; 4,542,122.
  • Catalyst particle size is important and particle sizes may range from that which is reasonably separable from the synthesis products to that which is reasonably able to be dispersed in a slurry phase. Particle sizes of 1-200 microns, preferably about 20 to 150 microns meet these requirements. Particles of this size which are easily separable from the synthesis products are the most advanta ⁇ geously benefitted by use of draft tubes to provide improved disper ⁇ sion. Particles of this size tend to be more influenced by gravity than are smaller particles which tend to stay in suspension and not settle out. Catalyst preparation may be accomplished by a variety of techniques, although catalyst preparation does not play a part in this invention and the regeneration - rejuvenation treatment disclosed herein will improve the activity of the hydrocarbon synthesis catalyst however it is prepared.
  • a typical catalyst preparation may involve impregnation, by incipient wetness or other known techniques of, e.g., a cobalt nitrate salt onto a titania, silica, or alumina support, optionally followed or proceeded by impregnation with a promoter material, e.g., perrhenic acid. Excess liquid is removed and the catalyst precursor dried at 100 ⁇ C to 125°C. Following drying or as a continuation thereof, the catalyst is calcined at about 300 ⁇ C-500°C to convert the salt or compound to its corresponding oxide(s).
  • a promoter material e.g., perrhenic acid
  • the oxide is then reduced by treatment with hydrogen or a hydrogen containing, gas at about 300 ⁇ C- 500 ⁇ C for a period of time sufficient to substantially reduce the oxide to the elemental or catalytic form of the metal.
  • Another, and sometimes preferred method for catalyst preparation is disclosed in US 4,621,072 incorporated herein by reference.
  • a number of ambient temperature mock-up draft tube demon ⁇ strations were performed to demonstrate the ability of draft tubes to redistribute catalyst in a reaction vessel environment.
  • Various runs were conducted in a demonstration apparatus comprising a main vessel having an internal diameter of 5.75 inches in which was located a draft tube of 0.9 inch internal diameter, the draft tube occupying, in cross sectional area about 2.4% of the total cross sectional area of the reactor.
  • the draft tube was about 12 feet tall and extended from about 0.5 inch above the bottom of the main vessel and ended below the level of the hydrocarbon slurry, which level differed from run series to run series.
  • the liquid phase of the slurry consisted of predominantly C13H28 linear paraffin, which has viscosity, density, and gas hold-up properties similar to the liquid product present in the reactor under hydrocarbon synthesis (HCS) conditions.
  • Catalyst 12% Co-1% Re on 94% Ti ⁇ 2-6% AI2O3, 50% porosity, 4.2 g/cc skeletal density was used as the solid phase in the slurry.
  • Table 1 presents the different balances and the conditions employed during each balance in terms of the number of lift tubes and/or rejuvenation tubes in use, the superficial gas velocities through these tubes, the solids concen ⁇ trations, reactor densities and reactor axial temperatures within the reactor slurry at different elevations within the reactor vessel for each balance.
  • Reactor Productivity refers to the volume of CO converted per hour per volume of slurry (catalyst + wax + gas).
  • Lift tubes were employed to demonstrate the operability of continuous catalyst regeneration during the same set of runs used to demonstrate the efficacy of such tubes for catalyst redistribution using the apparatus described in Example 2.
  • the rejuvenation tubes are separate, distinct, and independent of the four previously described draft tubes and are tubes used in addition to the previously described draft tubes.
  • the rejuvenation tubes are pipes 3" in diameter and 31-32 feet long.
  • Figure 5A illustrates the good results obtained with contin ⁇ uous hydrogen rejuvenation using generally one rejuvenation tube, but never more than two tubes.
  • the numbers in boxes on the figures are material balance period numbers.
  • the upper plot, Figure 5A shows, between days 1 and 3, the typical rapid catalyst deactivation that occurred in the hydrocarbon synthesis reactor.
  • Figure 5B shows the number of rejuvenator tubes used and the hydrogen flow rate.
  • the extent of the rejuvenation reaction occurring in the continuous rejuvenation experiment was monitored by thermocouples placed inside one of the rejuvenation tubes.
  • the measured temperature profile in the rejuvenation tube is compared with the temperature profile in the reactor slurry surrounding the rejuvenation tube for three different balances in Figure 6.
  • the solid circles represent the axial temperature profile in the reactor slurry, while the open squares represent the axial temperature profile in the rejuvenation tube.
  • the abscissae represents the axial distance in feet above the bottom of the reactor, and the ordinate represents temperature in degrees Fahrenheit.
  • the difference in temperature between the rejuvenation tube and the reactor slurry is the temperature rise in the rejuvenation tube, which is a measure of the extent of the rejuvenation reaction occurring there.
  • a comparison of the top two plots shows the effect of the temperature level upon the extent of reaction occurring in the rejuvenation tube for two balances that were close to one another in time.
  • Balance 37 made at an average temperature in the reactor of 428.5 ⁇ F, showed a considerably greater temperature rise in the rejuvenation tube than was exhibited in Balance 33 made at an average reactor temperature of 418.5 ⁇ F.
  • the efficacy of continuous rejuvenation depends upon the temperature level in the rejuvenation tube, which in these experiments was controlled by the temperature in the reactor slurry itself.
  • Monitoring of the tempera ⁇ ture in the reactor and temperature rise in the regenerator tube is an efficient method for monitoring catalyst rejuvenation.
  • the gas rate to the rejuvenation tubes which determines the residence time of the reactor slurry in the tubes, was also found to be important in determining the efficacy of the rejuvenation.
  • rejuvenation was carried out in both one and two rejuvenation tubes. While activity was declining with only one rejuvenation tube in service, activity again increased when the second tube was put in service, even though the total amount of hydrogen being fed to the two rejuvenation tubes was held constant.
  • Residence time will of course be dependent on the degree of catalyst deactivation as well as rejuvenator tube diameter and is within the control of the practitioner. Too high a rate of hydrogen flow reduced the residence time in the tube to the point that insufficient time was available for the pre-cleanup and cleanup reactions to occur.
  • the following example gives the physical configuration and the beneficial effects obtained from a rejuvenation tube that has external insulation and internal heating or cooling.
  • the advantage is that the effectiveness of continuous catalyst rejuvenation can be controlled independently of temperature in the reactor.
  • the rejuvenation tube Prior to Run 16 of the hydrocarbon synthesis pilot demon ⁇ stration unit (HCS-PDU), the rejuvenation tube was altered by provid ⁇ ing (1) an external jacket for heat insulation and (2) an internal tube to provide either heating or cooling.
  • the rejuve ⁇ nation tube was a nominal 3-inch diameter pipe 46' in length. Attached concentrically to the outside of this rejuvenation pipe was a nominal 4-inch diameter pipe also 46' in length whose purpose was to reduce the rate of heat transfer between the rejuvenation pipe and the reactor slurry. The ends of the 4-inch pipe were sealed against the 3-inch pipe so that the gap between them served as a heat transfer barrier. Inside the 3-inch rejuvenation pipe and concentric with it was placed a nominal 1-inch pipe the bottom of which was sealed.
  • This pipe extended the length of and extended out of the top of the 3" pipe and ended in a "T" fitting.
  • This 1-inch pipe.could be heated or cooled with steam to control the temperature of the fluid inside the rejuvenation pipe independently of the temperature in the reactor. Steam was supplied to the upper end of the 1-inch pipe through the horizontal arm of the "T" fitting. Inside the 1-inch pipe and concen ⁇ tric with it was placed a length of 3/8-inch tubing that extended the length of the 1 inch pipe and extended out of the top of the "T" and exited into a steam trap.
  • This tubing was to provide an outlet for the condensate accumulating in the 1-inch pipe in the event the 1-inch pipe was used for heating or to provide an outlet for the exit steam in the event the 1-inch pipe was used for cooling.
  • the lower end of the 1-inch pipe was outfitted with six fins to increase the transfer of heat to the incoming liquid-catalyst slurry. Each fin was 1/4" thick, 1/2" wide, and 8' long.
  • the lower end of the rejuve ⁇ nation pipe was baffled to prevent, as much as possible, influx of reactant gases with the liquid-catalyst slurry into the lower end of the rejuvenation tube.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Combustion & Propulsion (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Abstract

On répartit uniformément un catalyseur dans un réacteur à phase de suspension à l'aide d'un tube de tirage sensiblement vertical, entièrement immergé dans la suspension, dans lequel un gaz de sustentation est injecté à proximité du fond du tube de tirage vertical. Le catalyseur se trouvant près du fond du réacteur à phase de suspension est aspiré vers le haut du tube et déchargé au sommet de ce dernier, à proximité du sommet de la phase de suspension dans le réacteur.
PCT/US1993/012120 1992-12-18 1993-12-10 Tube de tirage destine a la repartition d'un catalyseur Ceased WO1994014536A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU58004/94A AU5800494A (en) 1992-12-18 1993-12-10 Draft tube for catalyst distribution

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US99421292A 1992-12-18 1992-12-18
US07/994,212 1992-12-18

Publications (1)

Publication Number Publication Date
WO1994014536A1 true WO1994014536A1 (fr) 1994-07-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1993/012120 Ceased WO1994014536A1 (fr) 1992-12-18 1993-12-10 Tube de tirage destine a la repartition d'un catalyseur

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Country Link
AU (1) AU5800494A (fr)
WO (1) WO1994014536A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674682A (en) * 1970-01-16 1972-07-04 Chevron Res Heavy oil conversion using fine particles
US3759669A (en) * 1969-11-24 1973-09-18 Shell Oil Co Apparatus for contacting liquid and solid particles
US4342876A (en) * 1980-12-22 1982-08-03 Bechtel International Corporation Method for oxidation of p-xylene and method for preparing dimethylterephthalate
US5157054A (en) * 1990-04-04 1992-10-20 Exxon Research And Engineering Company Catalyst fluidization improvements (C-2546)

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3759669A (en) * 1969-11-24 1973-09-18 Shell Oil Co Apparatus for contacting liquid and solid particles
US3674682A (en) * 1970-01-16 1972-07-04 Chevron Res Heavy oil conversion using fine particles
US4342876A (en) * 1980-12-22 1982-08-03 Bechtel International Corporation Method for oxidation of p-xylene and method for preparing dimethylterephthalate
US5157054A (en) * 1990-04-04 1992-10-20 Exxon Research And Engineering Company Catalyst fluidization improvements (C-2546)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Fundamentals of Chemical Technology Process, Technology of Chemical and Related Industries, OTTO SALLE VERLAG PUBLISHERS, SAULANDER PUBLISHING FRANKFURT, GERMANY, 1985, Chapter 1, Reaction Technology in Bubble Columns "Deckwer", (Note page 5 and page 12). *

Also Published As

Publication number Publication date
AU5800494A (en) 1994-07-19

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