A hydrocarbon conversion process, such as catalytic desulfurization of a vaporized petroleum feedstock with hydrogen or catalytic reforming of a vaporized hydrocarbon feedstock, is carried out by passing the gaseous medium upwardly through a fluidized bed of magnetizable composite particles having catalytic activity for hydrocarbon conversion and which contain 2 to 40 volume % ferro- or ferrimagnetic material to in a nontime varying (direct current) and substantially uniform applied magnetic field having a substantial component along the direction of gravity such that the composite particles have a component of magnetization along the direction of gravity. The gaseous medium is also the fluidizing medium passing upwardly at a superficial gas velocity ranging between:
(1) at least twice the normal minimum superficial gas velocity required to fluidize the bed in the absence of said applied magnetic field, and
(2) less than the superficial gas velocity required to cause time-varying fluctuations of pressure difference through said bed for a 0.1 to 1 second time interval during continuous fluidization in the presence of said applied magnetic field.
|
26. A process for carrying out a hydrocarbon conversion of a fluid stream of a hydrocarbon feedstock in a fluidized bed, which process comprises:
(a) carrying out said hydrocarbon conversion process under hydrocarbon conversion conditions, passing said stream through at least one controllably transported hydrocarbon conversion fluidized bed containing an admixture of magnetizable and catalytic particles, said bed of particles being expanded and levitated by said stream, and (b) controllably transporting said bed in response to a pressure differential in said bed, wherein at least a portion of said bed is subjected to an applied magnetic field having a substantial component along the direction of the external force field within said bed at a strength such that gross solids backmixing and fluid by-passing in said bed are suppressed but less than that which impairs the fluid-like properties of the bed.
7. A process for carrying out a hydrocarbon conversion of a fluid stream of a hydrocarbon feedstock in a fluidized bed, which process comprises:
(a) carrying out said hydrocarbon conversion process under hydrocarbon conversion conditions, passing said stream through at least one controllably transported hydrocarbon conversion fluidized bed containing magnetizable composite particles which contain 2 to 40 volume % ferro- or ferrimagnetic material, said bed of particles being expanded and levitated by said stream, and (b) controllably transporting said bed in response to a pressure differential in said bed, wherein at least a portion of said bed is subjected to an applied magnetic field having a substantial component along the direction of the external force field within said bed at a strength such that gross solids backmixing and fluid by-passing in said bed are suppressed but less than that which impairs the fluid-like properties of the bed.
1. A fluidized hydrocarbon conversion process which comprises:
(a) subjecting a fluidized bed comprised of magnetizable, fluidizable composite particles which have catalytic activity for hydrocarbon conversion and which contain 2 to 40 volume % ferro- or ferrimagnetic material to a nontime varying and substantially uniform applied magnetic field having a substantial component along the direction of gravity such that said composite particles have a component of magnetization along the direction of gravity, and (b) passing a fluidizing gaseous medium comprising a vaporized hydrocarbon feedstock upwardly through said bed at a superficial gas velocity ranging between: (i) at least 10% greater than the normal minimum superficial gas velocity required to fluidize the bed in the absence of said applied magnetic field; and (ii) less than the superficial gas velocity required to cause time-varying fluctuations of pressure difference through said bed for a 0.1 to 1 second time interval during continuous fluidization in the presence of said applied magnetic field.
2. The process of
3. The process of
4. The process of
5. The process of
6. The process of
8. The process of
9. The process of
10. The process of
11. The process of
12. The process of
13. The process of
15. The process of
16. The process of
17. The process of claims, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 wherein said applied magnetic field is nontime-varying and substantially uniform.
18. The process of
(1) more than the normal fluidization superficial fluid velocity required to expand and levitate said bed in the absence of said applied magnetic field; and (2) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said expanded and levitated bed over a finite period of time during continuous operation in the presence of said applied magnetic field.
20. The process of
21. The process of
23. The process of
24. The process of
|
|||||||||||||||||||||||||||||
This application is a division of application Ser. No. 786,613, filed Apr. 11, 1977, now U.S. Pat. No. 4,115,927, granted Sept. 26, 1978, which in turn is a continuation-in-part of application Ser. No. 610,071, filed Sept. 3, 1975, and now abandoned, which in turn is a continuation-in-part of application Ser. No. 514,003, filed Oct. 11, 1974, now abandoned.
This invention relates to a fluidized bed process. More particularly, the present invention is concerned with a process for operating a magnetically stabilized fluidized bed under conditions such that the flow of gas used to fluidize solid particulate magnetizable and fluidizable particles and an applied magnetic field are controlled to the extent that there is substantially no time-varying fluctuation of pressure at a point taken in the bed. Such a magnetically stabilized medium has the appearance of an expanded fixed bed; there is no gross solids circulation and very little or no gas bypassing. A bed of the magnetically stabilized medium shares many qualities of the normal fluidized bed; pressure drop is effectively equal to the weight of the bed divided by its cross sectional area, and independent of gas flow rate or of particle size; the medium will flow, permitting continuous solids throughput. Beds of the magnetically stabilized media also share some of the qualities of a fixed bed; countercurrent contacting can be readily attained; gas bypassing is small or absent, making it possible to achieve high conversions and attrition is minimal or absent.
The simultaneous possession of properties usually associated with the media of fixed and of fluid beds is highlighted, for example, in the use of a magnetically stabilized medium to trap particulates. Like the medium of a fixed bed, it will trap the particulates; like the medium of a fluid bed, it will not clog--the pressure drop of a bed of the medium will increase only by as much as due to the weight of the trapped material.
Many chemical and physical processes such as catalytic cracking, hydrogenation, oxidation, reduction, drying, polymerization, coating, filtering and the like are carried out in fluidized beds. A fluidized bed briefly, consists of a mass of solid particulate fluidizable material in which the individual particles are neutrally levitated free of each other by fluid drag forces whereby the mass or fluidized bed possesses the characteristics of a liquid. Like a liquid, it will flow or pour freely, there is a hydrostatic head pressure, it seeks a constant level, it will permit the immersion of objects and will support relatively buoyant objects, and in many other properties it acts like a liquid. A fluidized bed is conventionally produced by effecting a flow of a fluid, usually gas, through a porous or perforated plate or membrane underlying the particulate mass, at a sufficient rate to support the individual particles against the force of gravity. Conditions at the minimum fluid flow required to produce the fluid-like, or fluidized condition, i.e., the incipient fluidization point are dependent on many parameters including particle size, particle density, etc. Any increase in the fluid flow beyond the incipient fluidization point causes an expansion of the fluidized bed to accommodate the increased fluid flow until the gas velocity exceeds the free falling velocity of the particles which are then carried out of the apparatus, a condition otherwise known as entrainment.
Fluidized beds possess many desirable attributes, for example, in temperature control, heat transfer, catalytic reactions, and various chemical and physical reactions such as oxidation, reduction, drying, polymerization, coating, diffusion, filtering and the like.
Among the problems associated with fluidized beds, a most basic one is that of bubble formation, frequently resulting in slugging, channeling, spouting, attrition and pneumatic transport. This problem is most common in gas-fluidized systems. Bubbling causes both chemical and mechanical difficulties: for example, in gas-solids reaction gas bubbles may bypass the particles altogether resulting in lowered contacting efficiency while chaotic motion of the bed solids may set up detrimental mechanical stresses tending to deteriorate the vessel and its contents. Many procedures and systems have been proposed to effect improvements, for example, by the use of baffles, gas distribution perforated plates, mechanical vibration and mixing devices, the use of mixed particle sizes, gas plus liquid flow schemes, special flow control valves, etc.
DateUmr, Lm, cmUMF, LM
Ammonia catalyst of 3 to 6 mm. particle size was crushed and sieved to U.S. mesh -20/+30. This catalyst was previously magnetized in an applied field of 5000 oersteds. Due to its remament magnetization the material had the texture of wet sand, noticeable when pouring or screening.
A quantity of 1280 grams was added to a fluidization vessel having inside diameter of 7.33 cm. The depth of solids over the fitted porous distributor was 17.8 cm.
In the absence of applied field as air flow was increased the bed of solids was observed to develop voidage layers of separation in the upper one-third of the bed at a superficial velocity of 10.3 cm/s. Pressure drop through the bed increased smoothly with increase of superficial velocity until at 38.3 cm/s a spout formed in the bed and the pressure drop decreased from about 6.4 cm. of dibutylphthalate (DBP) to 2.9 cm. The spout had formed along the length of the 6 mm O.D. by 4 mm I.D. glass tube used as the pressure probe that was inserted at a 9 cm. depth within the bed. Thus, these solids failed to fluidize properly in the absence of applied field.
When uniform, axially oriented magnetic field of 40 oersteds was applied the measured pressure drop increased smoothly with increase of air flow rate up to a superficial velocity of 42.7 cm/s. A further increase of superficial velocity to 46.6 cm/s then caused a spout to form adjacent to the probe and the measured pressure drop decreased by about 47%. Again the bed structure deteriorated and lead to bypassing of the gas stream.
Finally, with applied field of 80 oersteds and the probe tip located about 5 mm. above the support grid, the bed retained its structural integrity throughout a test sequence in which superficial velocity ranged up to 100.4 cm/s. Pressure drop initially increased linearly with superficial velocity, then plateaued at 25.6 cm. DBP. The break in the curve of pressure drop vs. superficial velocity defined a point of minimum fluidization of 40.0 cm/s. The bed length was constant at 17.8 cm. up to the point of minimum fluidization, then expanded to 24.0 cm. at the said maximum flow rate of 100.4 cm/s. The bed remained free of bubbles or agitation at all flow rates studied. The test was repeated and displayed the similar behavior with maximum superficial velocity reacing 115 cm/s.
Magnetic moment of this ammonia catalyst is given in Table XVIII. The amount of 0.03 emu/g at zero applied field pertains to a powder sample of the -20/+30 mesh material that had previously been subjected to 5000 oersteds applied field. The low moment indicates the sample particles were nearly randomly oriented since the remanent magnetization is large for an undisturbed sample, i.e., 18.4 emu/g after exposure to applied field intensity of 16,000 oersteds.
| TABLE XVIII |
| ______________________________________ |
| MAGNETIC MOMENT OF AMMONIA CATALYST |
| Applied Field H., re. |
| Magnetic Moment emu/g |
| ______________________________________ |
| 0 0.03 |
| 40 1.58 |
| 80 3.26 |
| 5,000 144 |
| 16,000 166 |
| 0 18.4 |
| ______________________________________ |
This example illustrates that fluctuations of gas pressure distinguish the bubbling state of magnetized, fluidized solids from the stably fluidized state. In the stably fluidized state fluctuations are not detected.
Two thousand nine hundred and seventy grams of 177-250 micron spherical particles of C1018 steel described in Example 13 were placed in a fluidization vessel having inside diameter of 7.32 centimeters. The vessel was fitted with a pressure tap in the sidewall at a point 4 centimeters above the porous support grid. The pressure tap contained a wire mesh screen that prevented particles from leaving the vessel. One side of a U-tube manometer containing water was connected to the tap and the other end of the manometer kept open to the atmosphere as was the top of the fluidization vessel. Uniform, axially oriented magnetic field of 48 oersteds intensity was applied to the solids using the pair of six inch bore electromagnets. Increasing rates of steady air flow were admitted to the vessel to obtain measurement of pressure drop ΔPo read as difference in height of water in the manometer legs. When the bed became stably fluidized, its length gradually expanded with increased gas flow. Observation was also made of pressure drop fluctuation ±ΔP', if any, and presence or absence of visible bubbling or motion in the fluidized medium. The fluctuations in pressure drop represent values detected over about a ten second interval. The observed values of pressure drop, pressure drop fluctuations, bed length and other parameters, are listed in Table XIX.
From the data in Table XIX it may be seen that the stably fluidized state is clearly distinguishable from the settled state (fixed bed state) as well as from the unstably fluidized state. Thus, only in the stably fluidized state is pressure drop variant of flow rate, and bed length increasing with an increase of flow rate, while pressure fluctuations are absent. Comparative behavior of the states is summarized in Table XX.
It is noted that in the fluidized states the constant value of average pressure drop indicates the solids in the vessel were supported entirely by fluid forces. Visual observation of initial bubbling and motion in the bed coincide with the first detectable fluctuation of pressure drop (pressure difference).
| TABLE XIX |
| ______________________________________ |
| PRESSURE DROP, PRESSURE FLUCTUATIONS, AND |
| BED LENGTH CHANGE OF AIR FLUIDIZED C1018 |
| STEEL SPHERES OF 177-250 MICRON DIAMETER IN 48 |
| OERSTED APPLIED FIELD |
| Bubbles |
| U ΔP. |
| ±ΔP' |
| ΔL, |
| State of or |
| cm/s cm H2 O |
| cm H2 O |
| cm the solids Motion |
| ______________________________________ |
| 5.6 19.1 0 0 Settled No |
| 8.5 34.8 0 0 Settled No |
| 12.7 54.0 0 0 Settled No |
| 15.2 51.6 0 0.5 Stably Fluidized |
| No |
| 19.8 55.8 0 1.3 Stably Fluidized |
| No |
| 25.4 56.5 0 2.0 Stably Fluidized |
| No |
| 31.7 56.6 0.05 2.7 Unstably Fluidized |
| Yes |
| 40.9 51.0 3.0 3.5 Unstably Fluidized |
| Yes |
| 56.5 53.0 3.0 3.5 Unstably Fluidized |
| Yes |
| ______________________________________ |
| TABLE XX |
| ______________________________________ |
| DISTINGUISHABLE |
| STATES OF THE PARTICULATE SOLIDS |
| State Pressure drop |
| Bed Length |
| of increase increase Pressure |
| Solids with flow with flow Fluctuates |
| ______________________________________ |
| Settled Yes No No |
| Stably Fluidized |
| No Yes No |
| Unstably Fluidized |
| No Yes Yes |
| ______________________________________ |
As can be seen from the above examples and description of the invention, the present invention provides a means for conducting a fluidization process at a wide range of flow rates before the bubble transition point is reached. For example, as discussed above, it has been found that the larger the magnetization M of the fluidizable and magnetizible particles up to the point of agglomeration, the higher will be the transition velocity UT up to which the stably fluidized bed may be operated without bubbling and time-varying fluctuation, all other variables being equal. It will be recognized that in practicing the invention, it is the intent to operate the process in the stable, non-fluctuation manner wherein the stably fluidized bed is bubble-free. Accordingly, the size of bubbles in the stabilized fluidized media, if they do exist, will be about no larger than the spacing between particles and consequently do not cause time-varying fluctuations of the pressure difference through the fluidized bed over a finite period of time, e.g., 10 seconds, preferably a 100 second time interval during continuous fluidization.
As earlier indicated, the fluidization process of the present invention is useful in many applications heretofore used in the fluidization art. Of particular importance are the petroleum processes such as hydrofining, hydrocracking, hydrodesulfurization, catalytic cracking and catalytic reforming. The Table XXI summarizes typical hydrocarbon conversion process conditions effective in the present invention.
The feedstocks suitable for conversion in accordance with the invention include any of the well-known feeds conventionally employed in hydrocarbon conversion processes. Usually, they will be petroleum derived, although other sources such as shale oil and coal are not to be excluded. Typical of such feeds are heavy and light virgin gas oils, coker gas oils, steam-cracked gas oils, middle distillates, steam-cracked naphthas, coker naphthas, cycle oils, deasphalted residua, etc.
Generally, the magnetization M of a particle as obtained from a magnetometer when a given magnetizing field Ha is applied will not provide a value which is the same as the magnetization of the particle in response to the same intensity of magnetic field in the fluidized bed to be used in accordance with the teachings of the present invention.
The purpose of the following is to indicate a method for determinng the magnetization Mp of a typical particle in a bed from those values obtained from a magnetometer. Generally, this will require a calculation since the effective field that a bed particle is subjected to depends on the applied field, the bed geometry, the particle geometry, the bed voidage and particle magnetization. A general expression has been derived to relate these quantities based on the classical approximation of the Lorentz cavity that is employed in analogous physical problems such as the polarization of dielectric molecules.
Ha =He +Mp [dp +(1-εo)(db -1/3)](1)
Ha is the applied magnetic field as measured in the absence of the particles, He the magnetic field within a particle, Mp the particle magnetization, dp the particle demagnetization coefficient, εo the voidage in the particle bed, and db the bed demagnetization coefficient. The term -1/3 is due to the magnetizing influence of a (virtual) sphere surrounding the bed particle.
The expression above applies as well to a sample of particles such as used in a magnetometer measurement. In that case db is the demagnetization coefficient ds corresponding to shape of the cavity in the sample holder.
Magnetometer measurement produces a graph of Mp vs. Ha. Using the above equation and known values of dp, ds, εo, Mp and Ha a corresponding value of He may be computed. When the value of He is small its value found in this manner is determined by a difference between large numbers, hence is subject to cumulative errors. Accordingly, a modified approach is useful as described in the following.
Thus it is useful to define a reference quantity Hs representing the calculated field in a spherical cavity at the location of the particle. It is imagined that the magnetization of surrounding particles is unchanged when the said particle is removed.
Hs =Ha -Mp [(1-εo)(db -1/3)](2)
Combining the two expression gives an alternate relationship for Hs, in which Ha is eliminated.
Hs =He +Mp dp (3)
This expression is recognized to give Hs as the change of field in passing from the inside of a particle to the outside of the particle.
Denoting Km as the following constant ##EQU5## then from (2) Km equals the quantity Mp /Ha -Hs) i.e.
Km =Mp /Ha-Hs) (5)
Thus, on the graph of Mp vs. Ha straight lines of slope Km intersecting the measured curve and the Ha axis relate corresponding values of Mp and Hs. Accordingly a graph may be constructed of Mp vs. Hs. For example, when the sample is contained in a spherical cavity ds =1/3, Km is infinite, and Hs equals Ha. For a long sample such that ds =0, Km is negative and Ha is less than Hs i.e. the field magnetizing a particle of the sample is greater than the field applied to the sample.
Additionally, for a process bed, a constant Kp may be defined as follows: ##EQU6##
It may also be seen from Eq. (2) that a line of slope--Kp passing through a point Ha on the horizontal axis of the graph of Mp vs. Hs intersects the curve on the graph at a value of Mp giving the particle magnetization in the bed. Thus, the particle magnetization Mp in a process bed has been related to the field Ha applied to the process bed.
The relationship of Eq. (1) is an approximation more likely to be accurate for beds having high voidage than for very densely packed samples.
It is to be understood that the term "applied magnetic field" used throughout the specification and claims refers to an empty vessel applied magnetic field.
| TABLE XXI |
| ______________________________________ |
| Reaction Conditions |
| Principal Tem- Hydrogen |
| Conversion |
| perature Pressure Feed Rate |
| Rate |
| Desired °F. |
| psig V/V/Hr. scf/Bbl |
| ______________________________________ |
| Hydrofining |
| 500-800 50-2000 0.1-10.0 |
| 500-10,000 |
| Hydrocracking |
| 450-850 200-2000 0.1-10.0 |
| 500-10,000 |
| Catalytic 700-1000 0-50 0.1-20.0 |
| 0 |
| Cracking |
| Catalytic 800-1000 50-1000 0.1-20.0 |
| 500-10,000 |
| Reforming |
| ______________________________________ |
It will be understood by those skilled in the art that various modifications of the present invention as described in the foregoing examples may be employed without departing from the scope of the invention. Many variations and modifications thereof will be apparent to those skilled in the art and can be made without departing from the spirit and scope of the invention herein described.
| Patent | Priority | Assignee | Title |
| 10330511, | Jun 22 2017 | Saudi Arabian Oil Company | Alternating magnetic field flow meters |
| 10557730, | Jun 22 2017 | Saudi Arabian Oil Company | Alternating magnetic field flow meters with embedded quality assurance and control |
| 10690531, | Jun 22 2017 | Saudi Arabian Oil Company | Piezoelectric alternating magnetic field flow meters |
| 11341830, | Aug 06 2020 | Saudi Arabian Oil Company | Infrastructure construction digital integrated twin (ICDIT) |
| 11687053, | Mar 08 2021 | Saudi Arabian Oil Company | Intelligent safety motor control center (ISMCC) |
| 11881094, | Aug 06 2020 | Saudi Arabian Oil Company | Infrastructure construction digital integrated twin (ICDIT) |
| 9511343, | Mar 25 2011 | HOWARD UNIVERSITY | Methods and apparatus to control reaction rates of chemical reactions by applying a magnetic field |
| Patent | Priority | Assignee | Title |
| 2614064, | |||
| 2987468, | |||
| 3440731, | |||
| 4115927, | Oct 11 1974 | Exxon Research & Engineering Co. | Process for operating a magnetically stabilized fluidized bed |
| 4136016, | Oct 11 1974 | Exxon Research & Engineering Co. | Hydrocarbon conversion process utilizing a magnetic field in a fluidized bed of catalitic particles |
| 25770, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Dec 30 1980 | Exxon Research and Engineering Co. | (assignment on the face of the patent) | / |
| Date | Maintenance Fee Events |
| Jul 01 1994 | ASPN: Payor Number Assigned. |
| Oct 07 1994 | R169: Refund of Excess Payments Processed. |
| Date | Maintenance Schedule |
| Mar 22 1986 | 4 years fee payment window open |
| Sep 22 1986 | 6 months grace period start (w surcharge) |
| Mar 22 1987 | patent expiry (for year 4) |
| Mar 22 1989 | 2 years to revive unintentionally abandoned end. (for year 4) |
| Mar 22 1990 | 8 years fee payment window open |
| Sep 22 1990 | 6 months grace period start (w surcharge) |
| Mar 22 1991 | patent expiry (for year 8) |
| Mar 22 1993 | 2 years to revive unintentionally abandoned end. (for year 8) |
| Mar 22 1994 | 12 years fee payment window open |
| Sep 22 1994 | 6 months grace period start (w surcharge) |
| Mar 22 1995 | patent expiry (for year 12) |
| Mar 22 1997 | 2 years to revive unintentionally abandoned end. (for year 12) |