Method for withdrawing particulate solid from a high pressure vessel

The particulate solid is maintained in a bed in contact with a liquid within a high pressure vessel. The particulate solid is supported in the vessel in a cone-like configuration. A discharge tube is provided communicating with the particulate solid running from the bottom of the cone externally of said vessel and pressure on the supported particulate is produced to discharge said particulate out of said vessel via the discharge tube.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved method and apparatus for 
discharging particulate solids maintained in contact with fluid within a 
high pressure vessel. 
The improvements provided in accordance with the present invention are 
broadly applicable to the discharge of particulate solids maintained in 
contact with fluids, i.e., liquid and/or gases, from vessels in which 
various types of reactions, conversions or the like operations are carried 
out at super-atmospheric pressure. However, the present invention is 
particularly useful in the withdrawal of particulate solids as for example 
catalyst material from a liquid hydrocarbon treatment zone. For example, 
the present invention has particular application in the removal of spent 
catalyst material from a treatment zone in which a heavy hydrocarbon oil 
is contacted with gaseous hydrogen at high temperatures as for example 
between about 200.degree. and 850.degree. C. and high pressures as for 
example between about 1000 and 5000 psig for the purpose of effecting 
hydrocracking, hydrodesulfurization or the like hydrogenation reactions. 
To effect hydrogenation reactions of this type, it has been found 
advantageous to pass the hydrocarbon material and hydrogen upwardly 
bed of particulate catalyst material under conditions such that the 
catalyst particles are maintained in random motion to become a so-called 
"ebullated" bed. 
It is an object of the present invention to provide an efficient, 
expeditious and effective method and apparatus for discharging particulate 
solid in admixture with fluid from a high pressure vessel. 
It is a further object of the present invention to provide a method and 
apparatus as aforesaid whereby the fluid may be efficiently and 
economically separated from the particulate solid. 
It is a still further object of the present invention to provide an 
improved process and apparatus as aforesaid for removing particulate solid 
in admixture with liquid hydrocarbon and hydrogen from a high pressure 
hydrogenation zone. 
The foregoing and further objects and advantages of the present invention 
will appear from a consideration of the following specification. 
SUMMARY OF THE INVENTION 
In accordance with the present invention it has been found that the 
foregoing objects and advantages of the present invention may be readily 
obtained. 
Thus, the method of the present invention relates to particulate solid 
maintained in a bed in contact with a liquid within a high pressure 
vessel. The method comprises providing a high pressure vessel having a 
bottom and a top and containing therein a bed of particulate solid in 
contact with a liquid, supporting the particulate solid in the vessel in a 
cone-like configuration spaced from the bottom of the vessel, providing a 
discharge tube communicating with the particulate solid running from the 
base of the cone externally of said vessel, and producing pressure on the 
supported particulate to discharge said particulate out of the vessel via 
said discharge tube. The particulate solid is preferably a hydrogenation 
catalyst. In the preferred embodiment liquid hydrocarbon and hydrogen feed 
is introduced into the reaction vessel, the feed is passed upwardly 
through the reaction vessel and particulate solid to perform a 
hydrogenation reaction, and liquid and gaseous reactor effluent is removed 
from the top of the reactor. It is preferred to introduce additional 
liquid hydrocarbon feed into the base of the bed at a point adjacent the 
discharge tube to produce pressure on the supported particulate and 
discharge same out of the vessel via the discharge tube. It is a 
significant advantage of the process of the present invention that one can 
remove at least a portion of the particulate solid during the course of 
the hydrogenation reaction. It has been found that such a procedure gives 
optimum results. 
The apparatus of the present invention is a device for withdrawing 
particulate solid maintained in a bed in contact with a liquid within a 
high pressure vessel. The device comprises a high pressure vessel having a 
bottom and a top, a bed of particulate solid within said vessel in contact 
with a liquid, means for supporting the bed in the vessel in a cone-like 
configuration spaced from the bottom of the vessel, a discharge tube 
communicating with the particulate solid running from the support means 
externally of said vessel, and means for producing pressure on the 
supported particulate to discharge said particulate out of said vessel via 
said discharge tube. As indicated hereinabove, the particulate solid is 
preferably a hydrogenation catalyst. Inlet means is preferably provided at 
the bottom of the vessel for introduction of feed comprising hydrocarbon 
and hydrogen material, and outlet means is preferably provided at the top 
of the vessel for removal of liquid and gaseous reactor effluent. 
Distribution baffles are preferably provided at the bottom of the vessel 
between the inlet means and the particulate solid to provide even 
distribution of the feed throughout the vessel. A second inlet is 
preferably provided for the introduction of additional liquid hydrocarbon 
feed beneath the bed. Tube means are provided passing from the second 
inlet to the bed at a point adjacent to the discharge tube to produce 
pressure on the supported particulate to separate the particulate into a 
free-flowing form and discharge the particulate out of the vessel via the 
discharge tube. 
The foregoing and other features of the present invention will appear 
hereinbelow.

DETAILED DESCRIPTION 
The present invention relates to an improved method and apparatus for 
removing particulate catalyst from a fixed bed, up-flow type reactor which 
operates at a high pressure using dynamic pressure without disturbing 
operation of the reactor and without damage to the catalyst. 
The catalyst and reactor operates at a high pressure and temperature. The 
catalyst is maintained in the reactor as a fixed bed and operates in the 
up-flow mode in a hydrogenation reaction with the liquid hydrocarbon and 
hydrogen feed passing upwardly through the catalyst bed. In accordance 
with the present invention the catalyst is supported in the reactor in the 
configuration of a fixed cone and the catalyst is withdrawn from the 
reactor either continuously or discontinuously in order to increase the 
performance of the bed. The withdrawal of the catalyst is accomplished 
with the use of a high linear velocity in the bottom of the cone where the 
catalyst is supported in order to separate the catalyst into a 
free-flowing form. A dynamic pressure is produced which breaks up the 
supported catalyst and starts movement of the particulate to a transfer 
line out of the reactor to a separator for separating catalyst from liquid 
and gaseous products. A controlled differential pressure is preferably 
provided between the bottom of the cone and the separator to help the 
transportation of the solid in the transfer line with the pressure 
differential preferably controlled to assure the minimum linear velocity 
in the transfer line and to maintain the catalyst in suspension in the 
transfer line. 
Preferably liquid hydrocarbon feed is introduced at a high linear velocity 
at the bottom of the cone to produce the dynamic pressure and separate the 
catalyst into a free-flowing form. The excess of liquid pumped into the 
reactor for this purpose is discharged with the catalyst via the transfer 
line to the separator without changing the conditions in the reactor. The 
fixed bed is not fluidized or disrupted because the action of the liquid 
stream is restricted only to the bottom of the catalyst supporting cone. 
During the catalyst withdrawal, therefore, the reactor continues to 
operate as an up-flow, fixed bed reactor with the fixed bed moving 
downwardly to accommodate the area vacated by catalyst removal. 
When the desired amount of catalyst is removed, fresh catalyst is added 
from a pressurized vessel with appropriate means, as a valve or using 
higher pressure than the reactor itself. 
The liquid and gaseous products are separated from the catalyst in the 
separator with the liquid and gaseous products leaving the top of the 
separator to a secondary high temperature, low pressure separator. Gas is 
removed from the top of the secondary separator and liquid from the 
bottom, both for recycling. Catalyst material is removed from the bottom 
of the separator for recycling. 
The reactor of the present invention is used for the hydrogenation of 
hydrocarbons, as heavy oils or its residuum, such as demetallization of 
heavy Tia Juana crude. Preferably a portion of the catalyst is 
periodically removed during the operation of the reactor, as for example 
10% catalyst removal each week. The withdrawal operation takes less than 
one hour and does not disturb operations. 
Any of the conventional hydrogenation catalysts can be used, for example, 
cobalt, iron, nickel, tungsten, molybdenum, etc., as well as their 
sulfides and oxides alone or together with other suitable catalysts or on 
supports. Generally speaking the catalyst particles can be extrudates or 
spheres or other irregular shapes and can have an average equivalent 
diameter between 1/32 and 1/5 inch, although other sizes or shapes can be 
readily accommodated. 
As indicated hereinabove, the reactor operates at high pressure and high 
temperature. The linear liquid velocity used in the particulate bed is 
between 0.1 and 0.7 cm/sec. The gas (hydrogen) to liquid ratio may be 
readily varied as between 300 to 10000 cc/liter. The feedstock could be 
partially vaporized in the reactor under the operating conditions; 
however, in all cases the liquid content of the feedstock in the reactor 
must be higher than 10% in order to maintain proper operation of the 
particulate bed and also in order to perform catalyst withdrawal by liquid 
with minimal differential pressure in the transfer line. Normally, heavier 
feedstocks are preferred. 
Referring specifically to the drawings, FIG. 1 represents a partially 
schematic flow sheet of the overall reaction and apparatus of the present 
invention. High pressure vessel or reactor 10 having a top 11 and bottom 
12 is provided with a bed of particulate solid catalyst material 13, see 
FIGS. 2 through 4 wherein the particulate material is partially shown in 
the reactor. The particulate material is supported in reactor 10 in a 
cone-like configuration as clearly shown in FIG. 3 by a supporting means 
14 which may be a bubble tray or the like permitting flow of liquids and 
gases therethrough arranged in a cone-like configuration disposed at the 
lower portion of the reactor spaced from the bottom of the reactor. In the 
top 11 of the reactor a disengaging plate 15 prevents expansion of the 
catalyst bed during the process. In addition, baffles 16 are provided at 
the bottom 12 of the reactor in order to properly distribute the feedstock 
throughout the reactor. The reactor itself can be a conventional 
hydrogenation reactor as for example a conventional hydrodesulfurization 
reactor providing that the length to diameter ratio is preferably higher 
than 5 in order to have a large hydrostatic pressure on the bottom cone. 
The baffles and the disengaging plate assist in proper catalyst 
distribution and appropriate liquid and gas distribution to prevent 
channeling. This is especially significant after fresh catalyst is loaded 
into the reactor since short circuiting could occur in the reactor. 
Naturally, it is desired to have proper catalyst and feedstock 
distribution throughout the reactor. Thus, as shown the bed of particulate 
catalyst fills the reactor from supporting means 14 to or below 
disengaging plate 15. 
Inlet means 20 are provided in the bottom of the reactor for introduction 
of feedstock from feedstock storage means shown schematically as reference 
numeral 23 via line 24. The feedstock flows upwardly in the reactor 
contacting baffles 16 for proper distribution throughout the reactor. A 
discharge tube 21 is provided communicating with the particulate solid 13 
and running from the support means externally of said vessel. In addition, 
means 22 are provided for producing pressure on the supported particles 13 
to discharge said particles out of reactor 10 via discharge tube 21. As 
shown in FIG. 3 the means 22 is a second inlet for introducing feedstock 
beneath the bed adjacent discharge tube 21. The introduction of additional 
feedstock via second inlet 22 creates a high linear velocity at the base 
of the cone. Normally, the particulate is supported on the cone. However, 
the high linear velocity of the feedstock from second inlet 22 creates a 
dynamic pressure, breaks up the supported particulate and causes flow of 
particulate and feedstock out of the reactor via discharge tube 21. 
Thus, in accordance with the operation of the reactor, liquid and gas 
feedstock enters reactor 10 from bottom inlet 20, is distributed 
throughout the reactor 10 via baffles 16 so as to be progressively 
distributed under cone 14 which supports the catalyst. Reactor effluent 
passes out of the top of the reactor via outlet 23. When it is desired to 
remove particulate from the reactor additional liquid feedstock is 
introduced via second inlet 22 at the bottom of the cone where the 
catalyst is supported in a solid mass-like arch. Normally unconverted 
liquid feedstock is pumped in through second inlet 22 in order to provide 
dynamic pressure on the supported arch of catalyst and break up the arch 
and force the catalyst out discharge tube 21 in a flow pattern shown by 
the arrows in FIG. 3. When the arch of catalyst is destroyed by the 
dynamic pressure of the additional feedstock via second inlet 22, catalyst 
and liquid is removed via discharge tube 21. This procedure is operative 
even when the catalyst is adhered together by for example vanadium and 
carbon material in view of the liquid pressure which breaks up the lumps 
of catalyst. This procedure has been found to be particularly effective 
and represents a significant advantage over procedures employed 
heretofore. 
Referring to FIG. 1, particulate material 13 removed from reactor 10 via 
discharge tube 21 is transported to high temperature separator 30. From 
separator 30 the particulate material is separated from the slurry and 
discharged out the bottom of separator 30 via discharge line 31 and a 
rotating high pressure, high temperature valve 32 for recycling, 
reprocessing, or storage. Liquid and gas are separated from the slurry via 
line 33 to second separator 34. Second separator 34 separates gas and 
discharges same from the top of the second separator via line 35 and valve 
36 for storage or recycling. Liquid is discharged from the bottom of 
second separator 34 via line 37 and high temperature, high pressure pump 
38. The bottom of second separator 34 may be provided with a filter system 
to avoid passing fines to pump 38. Pump 38 may transfer liquid to heater 
39 and from heater 39 to second inlet 22 for recycling. Alternatively, 
liquid may be transferred via valve 40 and line 41 for storage or 
recycling, or via line 42 to flush discharge line 31. 
Microprocessor 50 is provided to control the various functions as shown by 
the dashed lines running from the microprocessor. Naturally, if desired 
the functions may be manually controlled. Thus, solid level detector or 
detectors 51 and liquid level detector or detectors 52 may be provided in 
reactor 10 controlled by microprocessor 50 to insure proper solid and 
liquid levels in reactor 10. The microprocessor may also control solid 
level detectors 53 in separator 30 and valve 32 for discharge of 
particulate from separator 30. The microprocessor may also control valve 
36 for discharge of gas from second separator 34. The microprocessor can 
also control valve 40 for discharge of liquid from second separator 34. 
Catalyst feed is stored in high temperature, low pressure vessel 60 
connected to low pressure, low temperature vessel 61 via line 62 and valve 
63. Vessel 60 is connected to reactor 10 via line 64 and valve 65. Solid 
level detectors 66 are provided in veseel 60 to maintain particulate level 
in the vessel. Detectors 66 and valves 63 and 65 are controlled by 
microprocessor 50. 
Thus, in accordance with the present invention if it is desired to remove 
part or all of the catalyst from vessel 10, one would start to pump heated 
liquid via second inlet 22. Naturally, additional feedstock could be used 
if desired. The flow rate is gradually increased to break the solid arch 
of particulate at the base of the cone, with the actual flow rate 
depending on such variables as particle size and shape and conditions in 
the veseel 10. When solid removal commences, the liquid flow rate is 
maintained in second inlet 22 to complete withdrawal of the desired amount 
of particulate. 
Special attention should be paid to control of differential pressure 
between separator 30 and the particulate. Normally, the range of 
differential pressure is around 50-100 psig. This differential can be 
adjusted stage-by-stage during the particulate withdrawal procedure after 
particulate withdrawal commences as indicated by the solid level detector. 
If solid is not removed, the flow rate in inlet 22 is increased gradually 
until the solid detector or detectors 51 indicates solid removal. 
Normally, the maximum velocity is about 5 cm/second. Then the flow rate 
could be maintained or decreased to the minimum flow rate for solid 
transfer. To assist solid removal, the differential pressure between 
reactor 10 and separator 30 could be increased to at or near the maximum 
value indicated above. Above this value it is possible that the catalyst 
could be damaged and some solid carry over to second separator 34 take 
place. 
In the preferred embodiment, during discharge the microprocessor 50 starts 
the catalyst introduction into vessel 10 from vessel 60 using solid 
detector 51. Alternatively, liquid could be injected into vessel 60 to 
start particle flow via pump 70 and line 71 (FIG. 4) in a manner after 
liquid injection in vessel 10. 
When the desired amount of catalyst is discharged and fresh catalyst added, 
the microprocessor reduces the flow rate and could wash the discharge line 
31 if necessary to avoid particle sticking in the discharge line. 
In order to illustrate the process and apparatus of the present invention a 
comparative example (Test I) was run using a reactor as shown in FIG. 1 
using a flat catalyst support and without changing catalyst during the 
course of the run compared to a test in accordance with the process and 
apparatus of the present invention (Test II). Both Tests I and II were for 
one (1) month duration, and Test II replaced 10% of the catalyst each 5 
days of operation. Both tests were up-flow demetallization with a heavy 
crude feedstock as shown in Table I with hydrogen. In Test I the reactor 
temperature was increased progressively from 370.degree. C. (start-up 
temperature) to 400.degree. C. (end of run temperature). Test II was run 
at a constant temperature. The total pressure in Tests I and II was 1800 
psig and the LHSV (ratio of volumetric feed rate of fresh feed to the 
volume of the reactor) was 0.3. 
The level of demetallization in Test I was maintained at 75% and the 
quality of the product measured at different times. After one month in 
operation the product quality had changed. The results are shown in Table 
I and indicate that operating Test I results in quality changes and 
conversion increases during the course of the run. Considering that 
conversion is more remunerative than quality, it is clear that income is 
higher at the end of the run where conversion is higher. 
FIG. 5 shows a plot of temperature as a function of time on stream for Test 
I. FIG. 6 shows the vanadium and carbon loading and FIG. 7 presents the 
profile of vanadium in the catalyst for the top, the middle and the bottom 
of the reactor. 
In accordance with Test I, using constant demetallization level the rate of 
metal deposition on the catalyst is constant and metal loading on the 
catalyst increases linearly as a function of time. Vanadium on catalyst 
decreases with the length of the reactor. The rate of vanadium deposition 
on the catalyst is higher in the top of the reactor and lower in the 
bottom. Looking at the carbon profile the contrary held, there is a higher 
carbon content in the outlet area than the inlet. Vanadium distribution on 
the particle is inhomogeneous. More vanadium in the external part of the 
particle than in the center according to the microprobe analysis shown in 
FIG. 7. 
Using the present invention (Test II) can be observed in Table I that 
higher conversion of residuum, demetallization and desulfurization 
occurred. At the same time the initial and final quality of the product is 
slightly lower, but the change is negligible compared with Test I. The 
amount of distillate formed in Test II is nearly constant which is a large 
advantage. 
FIG. 8 shows the change in demetallization during the time on stream for 
Test II, and FIG. 9 shows the carbon and vanadium loading. The carbon and 
vanadium profile is completely different from Test I showing that up-flow 
behavior produces lower carbon accumulation and flat vanadium distribution 
along the bed. 
Vanadium distribution in the particle is also different showing that a high 
amount of vanadium is now accumulated in the center of the particle (see 
FIG. 10) which teaches that the better behavior of the process and 
apparatus of the present invention. 
TABLE I 
______________________________________ 
PROPERTIES OF THE PRODUCTS 
TEST I TEST II 
INI- FI- INI- FI- 
PROPERTIES FEED TIAL NAL TIAL NAL 
______________________________________ 
API.degree. 5.0 10.2 12.0 13.0 12.0 
S % WT 3.4 2.0 1.8 1.4 1.6 
V ppm 700 420 330 290 320 
H % WT 9.85 10.1 10.3 10.5 10.2 
C % WT 84.7 82.6 82.3 82.1 82.4 
N % WT 0.63 0.45 0.41 0.40 0.41 
CCR % WT 21.3 14.0 13.5 12.1 12.8 
ASPH. % WT 14.0 12.5 10.7 9.7 10.6 
TEMPERATURE = 
BOILING POINT 
C.sub.5 - 200 -- 4 5 9 6 
200-305 -- 9 11 14 12 
350-500 12 23 24 24 23 
500.degree. C.+ 
88 64 60 53 59 
H.sub.2 
CONSUMP./BBL. 
FT3/B 1000 1000 1000 1000 
OPERATING 
CONDITIONS 
P (PSIG) 1800 1800 1800 1800 
T (.degree.C.) 370 400 400 400 
LHSV 0.3 0.3 0.3 0.3 
H.sub.2 HC LT/LT 1000 1000 1000 1000 
______________________________________ 
This invention may be embodied in other forms or carried out in other ways 
without departing from the spirit or essential characteristics thereof. 
The present embodiment is therefore to be considered as in all respects 
illustrative and not restrictive, the scope of the invention being 
indicated by the appended claims, and all changes which come within the 
meaning and range of equivalency are intended to be embraced therein.