US3708569A

US3708569A - Burning unconverted h-oil residual

Info

Publication number: US3708569A
Application number: US00099202A
Authority: US
Inventors: W Mounce
Original assignee: Cities Service Research and Development Co
Current assignee: Cities Service Research and Development Co
Priority date: 1970-12-17
Filing date: 1970-12-17
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02

Abstract

A method of treating a vacuum or atmospheric residuum oil containing sulfur is disclosed in which the residuum is subjected to a high pressure, high temperature hydrocracking and desulfurization evolving hydrogen sulfide (H2S) as a result. Afterward the unconverted residuum is used as fuel in a furnace, evolving sulfur dioxide (SO2) as one of the stack gases. The SO2 in the stack gas is removed and reacted with the H2S evolved during the residuum hydrocracking step to yield elemental sulfur.

Description

United States Patent [191 Mounce [111 3,708,569 1 Jan. 2, 1973 [54] BURNING UNCONVERTED H-OIL RESIDUAL [75] Inventor: William Mounce, Cranbury, NJ.

[73] Assignee: Cities Service Research & Development Company, New York, NY.

22 Filed: Dec. 17,1970

21 Appl. No.: 99,202

[52] US. Cl 423/574, 208/21 l [51] Int. Cl. ..C01d 17/04 [58] Field of Search ..23/224, 225; 208/211, 218

[5 6] I References Cited UNITED STATES PATENTS 3,451,923 6/1969 Welty et al. ..208/2ll 3,464,915 9/1969 Paterson et al.... 3,463,611 8/1969 l-Iaritatos et al ..23/225 P 2,664,345 12/1963 Kohletal. ..23/225 R25,770 4/1965 Johanson ..208/1O Primary Examiner--Oscar R. Vertiz Assistant ExaminerGeorge O. Peters Attorney-J. Richard Geaman [57] ABSTRACT A .method of treating a vacuum or atmospheric residuum oil containing sulfur is disclosed in which the residuum is subjected to a high pressure, high temperature hydrocracking and desulfurization evolving 4 Claims, 1 Drawing Figure 1 BURNING UNCONVERTED H-OIL RESIDUAL BACKGROUND OF THE INVENTION This invention relates to a process for eliminating sulfur contamination and emissions in hydrocarbon oils, while producing heat energy. More particularly this invention relates to a process for refining a high sulfur petroleum residuum and eliminating the waste gases while obtaining heat generation and free sulfur as a product.

It has been necessary for a considerable period to remove sulfur from the various products of petroleum oil refining, particularly the low boiling products such as gasoline and kerosine but also including relatively higher boiling fractions such as lubricating oils. In a given petroleum crude the concentration of sulfur and other undesirable elements such as nitrogen and oxygen generally increases as boiling points of the hydrocarbon constituents of the crude increase. Initial processing of the petroleum crude is atmospheric fractionation which may be followed by vacuum distillation after which the resulting bottoms fraction or residuum contains most of the sulfur.

It is now economically feasible to treat the heavy oil residuum further to obtain more desirable products by hydrocracking, hydrodesulfurization, etc. One such hydrocracking process is disclosed by U. S. Pat. No. Re. 25,770, issued Apr. 27, 1965 to Johanson for Gas- Liquid Contacting Process. This and other processes utilize large quantities of hydrogen to treat the heavy residuum at high pressure and temperature in the presence of a suitable catalyst to yield various desirable lower boiling products. A proportion of unconverted residuum remains and contains sulfur bearing compounds. Hydrogen sulfide is generally evolved during the hydrocracking of the residuum and is discharged along with the vapor effluent. The unconverted high sulfur residuum is unsuitable for many applications and may be employed as a cheap fuel. The material presence of sulfur presently precludes its use as a commercial fuel oil due to the necessity of reducing atmospheric pollution. I have, therefore, invented a process for utilizing such high sulfur unconverted residuum together with the hydrogen sulfide evolved from hydrotreating the residuum, to produce both heat energy and elemental sulfur.

SUMMARY OF THE INVENTION My invention is a method for producing free sulfur from a vacuum or atmospheric residuum which contains sulfur. The method comprises contacting the residuum with hydrogen in the presence of a particulate catalyst at high pressure and temperature to convert the residuum into lower boiling hydrocarbons, evolve H 8 and result in a proportion of unconverted residuum containing sulfur. The unconverted residuum is then burned to generate heat and evolve sulfur dioxide, after which the H 8 and S are reacted to produce elemental sulfur.

It is, therefore, an object of my invention to provide a process for producing elemental sulfur from a residual oil.

Another object of my invention is the production of useful heat energy from residual oils containing sulfur.

Yet another object of my invention is to provide a process for reducing atmospheric pollution from sulfur bearing stack gases.

Other objects and advantages of the process of my invention will be apparent from the brief description of the drawings and preferred embodiments which follow.

BRIEF DESCRIPTION OF THE DRAWINGS The process according to the invention is shown in schematic form in the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, vacuum or atmospheric residuum isfed to a vessel 12 together with a hydrogen containing gas. The vessel 12 may be a hydrocracking reactor of the type shown in the aforesaid U.S. Pat. No.

Re. 25,770 and is referred to as an H-Oil reactor vessel.

The H-Oil vessel is a high pressure, high temperature reactor, in which a particulate catalyst bed is maintained. Residuum and the hydrogen containing gas is fed into the bottom of the vessel 12 through a suitable feed conduit 14. An internal recycle conduit 16 may be mounted vertically in the reactor vessel to allow for recycling of liquid from the top portion of the reactor to its bottom in order to obtain sufficient upward fluid velocity through the catalyst bed to expand the bed up to five times its quiescent volume. Such an expanded catalyst bed is referred to herein as an ebullated bed. The resulting expansion causes random motion of the particulate catalyst with consequent homogeneity of the catalyst bed and fluid reactants, relatively uniform catalyst bed temperature and elimination of hot spots and excessive catalyst coking.

Alternatively, internal recycle of fluids in the reactor vessel may be dispensed with and a much smaller particulate catalyst utilized in consequence of the reduction of upward superficial velocity of fluids in the reactor vessel. Thus, where recycling is used the particulate catalyst may be spherical or elongated extrudates ranging in size from one thirty-second inch to three-eighths inch, while where no recycle is used the particles may range in size from 200 to 600 microns. The catalyst itself may be any suitable natural or synthetic hydrocracking catalyst although catalysts compounded of alumina carriers with cobalt and molybdenum cocatalyst are preferred. Temperatures are maintained in the range of from 650 to 950F, with a temperature of between 800F and 850F being preferred. Pressures in excess of 1,000 psig may be used, with a pressure in the range of from 2,000 psig to 3,000 psig being preferred.

Feedstock may be any residual oil derived from petroleum oils, shale oils or tar sands which contain sulfur and at least 25 percent material boiling above 975F. More particularly high sulfur containing atmospheric and vacuum residuums are the preferred feedstocks. They typically have a gravity of less than 20 API at 60F, and initial boiling point above 650F, and contain sulfur in excess of 2 percent weight. The hydrogen containing gas also introduced into the reactor vessel along with the feedstock is a mixture of light hydrocarbons and recycled and make-up hydrogen. The quantity of hydrogen is on the order of from 2,000 to 10,000 standard cubic feet of hydrogen per barrel of feedstock (scf/B) and preferably from 3,000 to 7,000 scf/B.

Effluent is withdrawn overhead from the upper portion of the reactor vessel 12 through an effluent withdrawal line 26 and introduced into a primary vapor-liquid separator 28. The primary vapor stream is withdrawn overhead via line 30. Heat exchanger 32 and cooler 33 are mounted in line 30 and serve to transfer heat to the hydrogen containing gas in line 22. The primary vapor stream is subjected, after cooling, to a second stage vapor-liquid separation in a secondary vapor-liquid separator 34 to remove any hydrocarbon components which were previously condensed. Vapor from the secondary separator 34 is withdrawn overhead through line 36, purged and returned to the reactor vessel as hydrogen gas. Purging is accomplished by:

use of a flow or pressure regulated valve 37. The purge gas stream is carried via line 38 to an amine unit 40 where the hydrogen sulfide is separated out. The hydrogen sulfide then is passed via line 42 to a Clause- Type Process unit 44 for conversion to sulfur as will be hereinafter described.

Separated liquid from the primary vapor-liquid separator 28 is withdrawn as a stream via line 46 to a secondary separation unit 48. Flow of the liquid stream from the primary separator 28 is controlled by a flow valve 50 mounted in line 46, which also acts to reduce system pressure to no more than 1,500 psig. Material boiling above 650F is withdrawn from the secondary separator 48 via line 52 and passed through a throttling valve 54 to a vacuum tower 56 where the heavy liquid stream is separated into a bottoms stream comprising material boiling above 975F and a heavy gas oil stream boiling between 650F and 975F. The heavy gas oil is withdrawn as a product stream, but part or all of the gas oil may be recycled to the reactor vessel via line 24, the latter line having pump 58 mounted therein to bring the recycle stream pressure up to reactor unit pressure.

Bottoms from the vacuum tower 56, constituting unconverted residuum and containing most of the remaining sulfur, are withdrawn via line 60 to a furnace 62 and burned as fuel for whatever heat generation purpose may be desired. Stack gases from the furnace which now contain sulfur dioxide pass to a recovery stage 64, utilizing any known process for separating the from the stack gases. Which produces a substantially pure S0 stream. The sulfur dioxide so removed is passed via line 66 to the unit 44 where it is reacted with the hydrogen sulfide also provided by the process of this invention to yield elemental sulfur, according to the following equation:

SO 2H S 38 21-1 0 As is readily apparent, the molar ratio of S0, to H 8 is l to 2 for this reaction.

Returning now to the secondary liquid separator 48, the vapor stream principally containing materials boiling below 650F is withdrawn overhead via pipe line 70 cooled in a cooler 72 before being mixed with another condensed liquid stream and introduced into a third stage gas liquid separator 74. The material boiling below C is separated as vapor from the remainder of the stream in the third stage separator 74 and passed to the gas purge line 38 via connecting line 76. Such a procedure assures substantially total removal of H 8 from the hydrocarbon product stream withdrawn as liquid from the separator 74. The liquid product stream is preferably introduced via line 78 to a fractionation tower 80 for separation into products as may be desired.

With a view to further detailing the process according to the present invention, the following example is given by way of illustration.

A feedstock comprising 20,000 BPSD (barrels per stream day) of vacuum residual oil, having an API gravity of 8.5 and 5.28 percent wt. sulfur is introduced into the process described above. Reactor vessel conditions are maintained at 3,000 psig and 840F with 6,000 cubic feet of hydrogen per barrel being used. The hydrogen sulfide being produced as a result of hydrocracking and hydrodesulfurization amounts to 6,870 lbs mole per day. Burning of the unconverted fraction of material boiling above 975F yields about 3,620 lbs mole per day of sulfur dioxide. Product yield of the hydrocracking operation in the reactor is as listed below.

% Weight BPSD Sulfur c1-c3 2.71 04-400? 11.41 3400 0.1 400-650F 21.12 5040 0.5 650-975F 29.16 6360 1.4 97s1=+ 33.44 6020 4.9 Totals: 101.48 20,820 1.9

With percent recovery of S0 in the stack gas recovery process, this represents 3,260 lbs mole per day of recovered S0 With percent removal of H 8 in removal amine scrubbing process, this represents 6,530 lbs moles per day of recovered H 8. The operating conditions and the catalyst activity in the hydrocracking reactor are controlled such that there is sufficient sulfur left in the unconverted 975F plus material such that the S0 recovered after combustion of this 975F plus oil is just sufficient to react with the H 8 recovered since the S0 to H 8 molar ratio is 1:2.

It can be seen that sulfur content of the final product fractions is measurably reduced. The unconverted residuum which contains most of the remaining sulfur is burned and the resulting SO, used as feed for a Claus type unit as a source of 80,.

Having described the process of my invention and wishing to cover those modifications and variations which would be apparent to those skilled in the art without departing from the spirit and scope thereof, I claim:

1. A process for producing sulfur from a residual oil containing sulfur, said method comprising a. contacting said residual oil with hydrogen in the presence of a particulate catalyst at high pressure and high temperature to desulfurize and convert said residual oil into lower boiling hydrocarbons, and resulting in the production of H 8 and a heavy oil fraction containing sulfur,

b. separating said converted desulfurized lower boiling hydrocarbons, said heavy oil and said H 8 into different streams,

c. burning said heavy oil as fuel, said burning resulting in the production of S0 and heat, and

d. reacting said S0 and H s to produce elemental sulfur and water.

2. The process of claim 1 wherein said step of contacting said residual oil with hydrogen comprises passing said residual oil and a hydrogen containing gas upwardly through a particulate catalyst bed at a superficial upward velocity sufl'icient to expand said catalyst bed up to five times the initial volume in a reaction" zone maintained under conditions of pressure between about 1,500 psig and 3,000 psig and temperature between about 800F and 900F.

3. The process of claim 2 wherein said step of separating said converted desulfurized lower boiling hydrocarbon oil, heavy oil and H s comprises withdrawing a liquid stream from said reaction zone,

separating said liquid stream into a said heavy oil fraction boiling above 975F, and into a lower boiling hydrocarbon fraction fractionating said lower boiling hydrocarbon fraction

Claims

2. The process of claim 1 wherein said step of contacting said residual oil with hydrogen comprises passing said residual oil and a hydrogen containing gas upwardly through a particulate catalyst bed at a superficial upward velocity sufficient to expand said catalyst bed up to five times the initial volume in a reaction zone maintained under conditions of pressure between about 1,500 psig and 3,000 psig and temperature between about 800*F and 900*F.
3. The process of claim 2 wherein said step of separating said converted desulfurized lower boiling hydrocarbon oil, heavy oil and H2S comprises withdrawing a liquid stream from said reaction zone, separating said liquid stream into a said heavy oil fraction boiling above 975*F, and into a lower boiling hydrocarbon fraction fractionating said lower boiling hydrocarbon fraction into a gas-oil fraction containing sulfur bearing material and into said desulfurized lower boiling hydrocarbon oil, and recycling said gas-oil fraction to said contacting zone.
4. The process of claim 1 in which the residual oil of step (a) is contacted with hydrogen under controlled operating conditions such that when the heavy oil fraction of step (a) is burned as fuel in step (c), the SO2 formed in the burning is just sufficient to react with the H2S produced in step (a) in the molar ratio of 1:2.