U.S. patent number 3,773,653 [Application Number 05/124,059] was granted by the patent office on 1973-11-20 for production of coker feedstocks.
This patent grant is currently assigned to Hydrocarbon Research, Inc.. Invention is credited to Seymour B. Alpert, Govanon Nongbri, Ronald H. Wolk.
United States Patent |
3,773,653 |
Nongbri , et al. |
November 20, 1973 |
PRODUCTION OF COKER FEEDSTOCKS
Abstract
Coker feedstocks having minimum amounts of sulfur or metals are
produced from residuum feeds using an ebullated bed reaction zone.
The qualities of the coker feedstocks are controlled through the
use of selected operating conditions within the limits of
converting 30 to 60 percent of the material in the feed boiling
above 975.degree. F to lighter boiling products.
Inventors: |
Nongbri; Govanon (Trenton,
NJ), Alpert; Seymour B. (Princeton, NJ), Wolk; Ronald
H. (Lawrence Twp., Mercer County, NJ) |
Assignee: |
Hydrocarbon Research, Inc. (New
York, NY)
|
Family
ID: |
22412507 |
Appl.
No.: |
05/124,059 |
Filed: |
March 15, 1971 |
Current U.S.
Class: |
208/50; 208/58;
208/89; 208/102; 208/156; 208/212; 208/216R; 208/251H |
Current CPC
Class: |
C10B
55/00 (20130101) |
Current International
Class: |
C10B
55/00 (20060101); C10b 055/00 (); C10g
023/02 () |
Field of
Search: |
;208/89,50,58,212,216,251H |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Schmitkons; G. E.
Claims
We claim:
1. In a process for the production of coker feedstocks having
minimum amounts of sulfur or metals wherein a petroleum resid,
containing at least 25 percent of hydrocarbons boiling above
975.degree. F, and a hydrogen containing gas are fed in upflow
through an ebullated bed reaction zone while maintaining a
particulate hydrotreating catalyst in said reaction zone at a
hydrogen partial pressure between 1500 and 3000 psi, a temperature
between 700.degree. and 900.degree. F and at a space velocity
between 0.3 and 1.5 V.sub.f /hr/V.sub.r wherein the improvement
comprises:
a. converting, in said reaction zone, 30 to 60 percent of the
fraction boiling above 975.degree. F in the feed to lower boiling
fractions;
b. removing a liquid effluent from said reaction zone;
c. and separating, from said liquid effluent, the bottom fraction
boiling above 975.degree. F, having less than two weight percent
sulfur and less than 70 ppm vanadium.
2. The process of claim 1 wherein said liquid effluent removed in
step b) is passed to a second reaction zone, wherein said second
reaction zone is operated under conditions substantially the same
as the first reaction zone, before completing step c).
3. The process of claim 2 wherein the reaction zones are operated
at a temperature between 750.degree. and 840.degree. F and the
catalyst is replaced at a rate between 0.02 and 0.4 pounds of
catalyst per barrel of resid fed wherein said bottom fraction is
coked to yield a coke having less than 200 ppm vanadium and less
than 2.5 percent sulfur.
Description
BACKGROUND
With a large increase in light hydrocarbon product demand in the
United States, the petroleum refiner has had to increase his
throughput rate. As a result, he is faced with the problem of
discarding the increased residual fractions which arise from
refining more crude. Elimination of residuals has been the subject
of considerable study by the refining industry. This has led to a
substantial investment in processing facilities which provide a
wide variety of approaches to the solution of this problem. Among
the several processes either currently in operation or being
installed are:
1. coking (both delayed and fluid)
2. propane deasphalting
3. partial oxidation
4. residue hydrocracking; and
5. residue desulfurization.
U.S. Pat. No. 2,871,182 discloses one method of making coke from
long and short residua. This patent like other prior art teachings
fails to solve the problem of how to produce a coke with minimum
levels of metals or sulfur or how to handle the increased volume of
residua without requiring increased coker units. The metals and
sulfur content of the coke produced is dependent upon the
characteristics of the coker feedstocks. In today's ecology
oriented society, the restriction of pollutants such as sulfur and
metals in fuel sources poses a situation that requires new methods
by which fuels, such as coke, can be produced so that they will be
low in sulfur and metals. At the same time different consumers
require coke having different characteristics. This then leaves one
with the task of producing a coker feedstock by a method which will
allow one to control the sulfur and metals levels in the product.
The prior art teaches that there is increased desulfurization and
demetalization of residua feeds with increased severity of
hydrogenation conditions and conversions. This teaching does not
prove true when producing coker feedstocks from residua feeds.
SUMMARY
In this invention it was found that residua feeds could be
converted into coker feedstock having minimum levels of sulfur or
metals which would enable one to produce coke having specific
desired characteristics. It was discovered in the operation of this
invention that the level of sulfur and metals in a coke and,
therefore, in a coker feedstock is dependent upon the percent
conversion of the fraction in the feed boiling above 975.degree. F
to material boiling below 975.degree. F. It was further discovered
that the levels of sulfur and metals in the coker feedstock reach a
minimum, dependent upon feed and space velocity, level between 30
and 60 percent conversion of the 975.degree. F.sup.+ fraction.
The problems of handling the increasing volume of residue solved by
hydrogenating the residua through an ebullated bed reaction zone
prior to using it as a feedstock to a coker. The ebullated bed is a
three phase reaction zone in which the gas and liquid are passed
upwardly through the particulate solids in random motion in the
liquid. The operation of the ebullated bed reaction zone is
disclosed in U.S. Pat. Re. 25,770.
It was discovered that in the ebullated bed reaction zone the resid
is hydrocracked under conditions that can control the resid yield
to match existing coker capacity. No additional cokers are
necessary to handle the increased residua and operating conditions
can be further varied to control the level of sulfur and metals in
the coker feed.
A process has been discovered in this invention, wherein coke
having less than 200 ppm vanadium and less than 2.5 percent sulfur
can be produced from the residual fractions discarded in the
refining of crude petroleum. The levels of sulfur and metals,
hereinafter referred to as vanadium, vary with the source of the
crude which in turn affects the levels of the sulfur and metals in
the resid and, therefore, in the coker feedstock and the resulting
coke.
In this process the minimum sulfur and vanadium that can be present
in the product, coker feedstock, obtained from the hydrotreating of
the resid can be determined experimentally for each type of crude.
It has been determined that coke with the desired minimized sulfur
and vanadium content can be obtained by operating the ebullated bed
for the hydrotreating of the resid under pressures between 1,500
and 3,000 psig hydrogen partial pressure, temperatures between
700.degree. and 900.degree. F and preferably 750.degree. to
840.degree. F, a liquid space velocity of 0.3 to 1.5 volumes of
feed per hour per volume of reactor, V.sub.f /hr/V.sub.r, with a
suitable hydrotreating catalyst as hereinafter described, and a
conversion of between about 30 and about 60 percent of the
975.degree. F plus fraction, in the resid, to lower boiling
hydrocarbons. Within these conversion percentages the minimum of
sulfur or vanadium in the product is a function of the temperature,
space velocity, pressure and catalyst activity, i.e., replacement
rate.
When the resid is hydrotreated under the above conditions, a liquid
effluent is obtained from the reaction zone which has a 975.degree.
F plus fraction with less than 2 percent sulfur and less than 70
ppm vanadium.
The liquid effluent undergoes a separation to provide the coker
feedstock which will give a coke having the desired range of sulfur
and vanadium content.
DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram of the process for producing a coker
feedstock from a hydrocarbon residuum.
FIG. 2 shows the change in the level of sulfur in the 975.degree.
F+ fraction with a change in liquid space velocity and H.sub.2
pressure at a given percent conversion of the 975.degree. F+
material in the feed.
FIG. 3 shows the change in the level of vanadium in the 975.degree.
F+ fraction with a change in the liquid space velocity and H.sub.2
pressure at a given conversion of the 975.degree. F+ material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Generally, the ebullated bed hydrotreating of a hydrocarbon
residuum material is carried out as diagrammed in FIG. 1 and may be
described as follows:
The feed material which normally has at least 25 volume percent of
components boiling above about 975.degree. F at 1 together with
hydrogen in 5 passes in line 3 to reactor 2. Such a reactor will be
charged with a suitable catalyst having the required hydrotreating,
desulfurization or demetalization, characteristics. The catalyst
particles will have a narrow size distribution with a diameter in
the range from about 20 to about 325 USS mesh. Alternatively,
catalysts in the form of extrudates of about 1/2 inch to about 1/32
inch diameter may be used.
The catalyst may be of any type of material which can affect
hydrogenation of the sulfur and metal compounds in the feed.
Particular examples would be cobalt molybdate on alumina
(preferred), nickel molybdate on alumina, nickel tungstate on
alumina, alumina and the like as defined in the prior art.
Normally, the catalyst consists essentially of alumina promoted
with metals and compounds of metals selected from groups VIb and
VIII of the periodic table.
The residuum and hydrogen pass by upflow through the bed of
catalyst such that the bed will tend to expand to at least 10
percent of the rest volume of the bed and such that the catalyst
particles are all in random motion in the liquid. In such
condition, they are described as ebullated. As stated in the
Johanson patent cited hereinabove, one can operate the particular
process so as to cause the mass of contact material in the fluid to
become ebullated and to calculate the percent expansion of the
ebullated mass at any given set of reaction conditions.
Under the preferred conditions of temperature, and pressure set
forth, a total effluent is removed in 11 and passes with hydrogen
in 7 through 9 to reactor 4 for further hydrogenation in an
ebullated bed under the preferred operating conditions of reactor
2. Reactor 4 will also contain a suitable catalyst as hereinbefore
described. The conversion of the 975.degree. F plus fraction in the
resid feed by the hydrotreating process is between 30 and 60
percent.
A vapor overhead effluent is removed in 17 and a liquid effluent is
removed in 13 to separator 6. The liquid effluent coker feedstock
in 13 has less than 2 percent sulfur and less than 70 ppm vanadium
in the 975.degree. F plus fraction. An overhead is removed in 21
and the desired coker feed is passed in 25 to coker 10. Coker 10
may be any of several known coking operations existing in the art.
The 650.degree. F and lighter products from the coker are removed
in 29 while the heavy gas oils leave coker 10 in 33. The coke
leaves in 37. It has been found that a two or more stage
hydrogenation is preferred although a single stage may be used as
well.
FIG. 2 is a graph showing the effect of liquid space velocity and
hydrogen pressure on the sulfur content of the 975.degree. F+
fraction in the product. Point A represents the sulfur content of
the resid feed. The feed is subjected to operating conditions under
a liquid space velocity in volume of feed per hour per volume of
reactor having a value "Q" and at a hydrogen partial pressure
having a value "H." Curve B represents the sulfur level in the
975.degree. F+ product fraction when operating with a liquid space
velocity of Q and a hydrogen partial pressure of 0.67 H. Curve D
was operated at 0.5 Q and 0.67 H, curve C had operating conditions
of Q and H and curve E had operating conditions of 0.5 Q and H.
Line F is the locus of minimum points at a hydrogen partial
pressure of H while line G is the locus of minimums of sulfur in
the 975.degree. F+ fraction in the product at 0.67 H.
FIG. 3 is a graph showing the effect of liquid space velocity and
hydrogen pressure on the vanadium content of the 975.degree. F+
fraction in the product. Point Z represents the vanadium content of
the feed. The feed is subjected to operating conditions under a
liquid space velocity in volume of feed per hour per volume of
reactor, having a value "Q" and at a hydrogen partial pressure
having a value "H." Curve X represents the vanadium level in the
975.degree. F+ product fraction when operating with a liquid space
velocity of Q and a hydrogen partial pressure of H. Curve Y was
operated at Q and 0.67 H, curve W had operating conditions of 0.5 Q
and 0.67 H and curve V had operating conditions of 0.5 Q and H.
Line T is the locus of minimum vanadium content points at a
hydrogen partial pressure of 0.67 H while line U is the locus of
minimum points at a hydrogen partial pressure of H.
All minimums in FIGS. 2 and 3 fall between 30 and 60 percent
conversion of the 975.degree. F+ material in the feed.
In general, it is envisioned that the reaction conditions utilized
in hydrogenation process of this type would be within a temperature
range of between 700.degree. and 900.degree. F and preferably
between 750.degree. F and 840.degree. F, a hydrogen partial
pressure range of between 1,500 and 3,000 psig, a liquid space
velocity range of between 0.3 and 1.5 V.sub.f /hr/V.sub.r and a
catalyst replacement rate between 0.02 and 0.4 lbs/bbl.
It has been found, in accordance with this invention, that by
controlling the quality, that is to say sulfur, and vanadium
content of the coker feedstock, that the quality of the coke
produced therefrom is controlled. The quality of the coker
feedstock is, in turn, controlled by the operating conditions used
in the ebullated bed, hydrogenation reactor and the feedstock
characteristics.
In accordance with this invention the necessary quality of the coke
is obtained by controlling the quality of the coker feedstock.
Variations of the operating conditions in the ebullated bed
hydrotreating reactors results in conditions that will produce a
coker feedstock with the desired properties. That is to say, from a
given amount of feedstock, a known coker capacity and coke yield
requirements, the desired level of conversion of the 975.degree. F+
material in the ebullated bed unit is estimated to thereby produce
a coker feedstock that will produce coke having the desired levels
of sulfur and metals.
EXAMPLE I
To illustrate the hereinabove disclosure, the following cases on
West Texas resids are presented.
In Table I the yields and coke product properties obtained from
direct coker processing of virgin vacuum bottoms are given.
The yields and product properties obtained from the ebullated bed
hydroconversion processing of the virgin vacuum bottoms followed by
the coker processing of the ebullated bed pretreated vacuum bottoms
coker feedstock are summarized in Tables 2 and 3 respectively.
Tables 2 and 3 show that if one wanted a coke with about 1.5
percent sulfur and about 140 ppm of vanadium then one would need a
coker feedstock with about 1.2 percent sulfur and about 41 ppm of
vanadium. Starting with a residuum with 2.65 percent sulfur and 70
ppm of vanadium one would then find that ebullated bed reactor
should be operated at 780.degree. F, 2250 psig of hydrogen with a
space velocity of 1.0 V.sub.f /hr/V.sub.r to give the desired coker
feedstock. This results in a minimum sulfur of 1.2 percent in the
975.degree. F+ coker feedstock at the given operating conditions
when about 33 percent of the 975.degree. F+ fraction is converted
to lower boiling fractions.
Comparing the results from Tables 1 and 3 shows that; (1) the
sulfur and metal contents of the coke obtained wherein the
ebullated bed processing of the coker feedstock is performed are
lower than those of the coke obtained by direct coking of the
virgin resid; (2) the yield of coke by direct coking of the virgin
resid is about 30 percent of the total resid, as compared to 18.5
percent when processing the virgin resid through the ebullated bed
reactor prior to coking, thereby reducing the more valuable lower
boiling hydrocarbons obtained from the resid.
The sulfur and metals contents and the yield of coke depends
respectively on the sulfur content and metals content of the coker
feedstock. These are fixed properties of the virgin vacuum resid
and hence the coke yield and its sulfur and metals contents are
defined when the virgin vacuum resid is directly coked. On the
other hand, the properties of the coker feedstock are easily
changed in the ebullated bed by manipulating the operating
variables. Thus the coke yield and the sulfur and metals contents
of the coke can be adjusted to meet with different coke needs.
##SPC1## ##SPC2## ##SPC3##
Although the above example and discussions disclose a preferred
mode of embodiment of this invention, it is recognized that from
such disclosures, many modifications will now be made obvious to
those skilled in the art and it is understood, therefore, that this
invention is not limited to only those specific methods, steps or
combinations or sequence of method steps described, but covers all
equivalent steps or methods that may fall within the scope of the
appended claims.
* * * * *