Mineral oils: processes and products – Asphalts – tars – pitches and resins; making – treating and...
Reexamination Certificate
2000-03-16
2002-03-26
Myers, Helane E. (Department: 1764)
Mineral oils: processes and products
Asphalts, tars, pitches and resins; making, treating and...
C208S044000
Reexamination Certificate
active
06361682
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a process and a plant for slurrying and oxidation of a petroleum resid with water. More particularly, the invention is directed to integrating the slurrying with oxidation, by prilling the resid at an elevated temperature to form liquid particles of the resid in a gaseous medium and directly quenching the particles with cooling water to form a pumpable slurry for oxidation.
BACKGROUND OF THE INVENTION
As the maturity of petroleum refining progresses, more and more of the crude oil is converted to useful light products. The bottom of the barrel, petroleum resid, becomes more and more difficult to dispose of in an economical, useful manner. The residue from petroleum refining has a wide number of uses, including paving asphalt, fuel and feedstock for gasification to form a synthesis gas. Each of these uses for the resid has a number of disadvantages. Paving grade asphalt used in road construction must meet a number of specifications, including viscosity (usually 200-5000 poises at 60° F.), penetration (usually greater than 30 to 200 dmm), penetration ratio 15° F./25° F. (usually above about 0.3), ductility, temperature susceptibility, and others. Because of the narrow specifications for paving asphalt, it is becoming more and more difficult for resids to meet the needed paving asphalt specifications.
In contrast to paving asphalt, the specifications for petroleum resid that is burned as a fuel or used as feed in a partial oxidation gasifier, are less stringent. The resid generally has a higher calorific value and better combustion characteristics compared to coal and petroleum coke. Unfortunately, heavy resid poses storage and handling problems for use as a liquid fuel since it must be kept at an elevated temperature or a high value lighter hydrocarbon is used as a diluent to keep it in liquid state.
In the gasification of resid, it is also typical for water or steam to be introduced into the gasifier as a temperature moderator and hydrogen source. In the gasification of coal and coke, these materials are commonly supplied to the gasification reactor in the form of a water slurry. Much work has gone into formation and maintenance of the coke/coal slurry. The coal or coke is usually ground to a fine particle size and mixed with water to make a pumpable slurry. Factors such as particle size and water content are usually critical to obtain a pumpable slurry which can be supplied to the gasification reactor. For example, if the particle size is too large or the water content is too low, the viscosity of the slurry will be too high to be easily pumped. On the other hand, if the water content is too high, it may be necessary to supplement the feed to the gasification reactor with a liquid hydrocarbon feedstock. Various references discussing slurrying of coke and/or coal for gasification or combustion include U.S. Pat. No. 3,996,026 to Cole; U.S. Pat. No. 4,526,588 to Lusch et al; U.S. Pat. Nos. 4,657,702 and 4,681,700 to Vasconcellos et al; U.S. Pat. No. 4,950,307 to Najjar et al; and WO 97/05216 to Isentropic Systems Ltd.
U.S. Pat. No. 5,478,365 to Nikanjam et al discloses a combustible heavy hydrocarbon-in-water emulsion containing a phosphate ester, a high molecular weight thickener, a high softening point hydrocarbon material and 25-50 weight percent water. The emulsion is made in a colloid mill by mixing the components at an elevated temperature and pressure to keep the hydrocarbon material from solidifying and the water from vaporizing, and then cooling the emulsion.
U.S. Pat. No. 4,931,231 to Teppo et al discloses a method for manufacturing discrete pellets of asphaltic material by flowing the asphaltic material in molten form as an elongated annular stream directly into cooling water to solidify and shatter the elongated stream into discrete solid particles. The particles formed as a result of shattering are not spherical and have undesirable flow and/or handling characteristics.
A pelletizer apparatus and method for pelletizing a hard petroleum resid is disclosed in our earlier copending application U.S. Ser. No. 09/447,408, filed Nov. 23, 1999. This disclosure involves the prilling of the resid at a temperature at which it is liquid, allowing the resid particles to form a substantially spherical shape, and then quenching the particles to solidify them in their spherical shape.
SUMMARY OF THE INVENTION
In the present invention liquid asphaltenes from solvent desasphalting or another petroleum resid material are pumped to an extrusion device to produce liquid particles in a gaseous medium that are quenched with water to form a slurry of hydrocarbon particles of the appropriate size distribution suitable for pumping and combustion/gasification without further grinding or processing.
In one aspect, the present invention provides a process for the slurrying and oxidation of a petroleum resid, comprising the steps of:
(a) heating petroleum resid to a temperature at which it is in a liquid state;
(b) forming the resid into finely divided particles in a gaseous medium;
(c) directly quenching the resid particles with water to form a pumpable slurry of solidified resid particles; (d) pumping the slurry to an oxidation reactor; and
(e) injecting the slurry into the oxidation reactor and oxidizing the resid in the reactor. The resid preferably has a softening point temperature above about 185° F. The process can also include solvent deasphalting a petroleum residue to form a deasphalted oil fraction, an optional resin fraction and an asphaltene fraction, and supplying the asphaltene fraction as the petroleum resid for the heating step (a).
The particle-forming step (b) and the quenching step (c) preferably comprise: (1) continuously feeding the liquid petroleum resid from step (a) to an inlet of a centrifugal prilling head comprising a plurality of radially arrayed discharge orifices; (2) rotating the prilling head to discharge liquid petroleum resid from the orifices into free space at an upper end of a prilling vessel having a diameter larger than a throw-away diameter of the discharged petroleum resid; (3) allowing the discharged resid to break apart and form into particles in a high temperature zone of the prilling vessel at which the petroleum resid is liquid and fall downwardly into a water bath maintained at a temperature effective to solidify the particles and form the pumpable slurry; and (4) withdrawing the slurry from the prilling vessel. The discharge orifices are preferably arrayed at a circumference of the prilling head in a plurality of vertically spaced upper and lower rows wherein the lower row or rows are disposed at a smaller radius from an axis of rotation of the prilling head than the upper row or rows. The prilling head can have a circumference tapered from an uppermost row to a lowermost row. Preferably, the prilling head is rotated at from about 200 to about 10,000 rpm, the prilling head has a diameter from about 2 inches to about 5 feet, the orifices have a diameter from about {fraction (1/32)}-inch to about 1-inch and a capacity of from about 1 to about 1000 lbs/hr of resid per orifice, the throw-away diameter is from about 1 foot to about 15 feet and the particles have a size range larger than about 0.01 mm and smaller than about 1 mm.
The water bath is preferably maintained in the prilling vessel at a temperature from about 40° to about 190° F. The water can be introduced into the prilling vessel as an inwardly directed spray in a cooling zone above the water bath to at least partially cool the particles before they enter the bath. The quenching water can pass once through the prilling vessel, essentially free of recirculation, and wherein the slurry from the prilling vessel has a solids content from 50 to 80 percent. If necessary, water can be added to or removed from the slurry and recirculated to the prilling vessel. A dispersant can be admixed into the slurry to aid pumpability. The slurry can have an apparent viscosity less than about 2000 cSt, and preferably comprises from 60 to 70 weight perc
Moretta Jon C.
Shah Pankaj M.
Subramanian Murugesan
Kellogg Brown & Root, Inc.
Myers Helane E.
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