Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2000-05-01
2003-02-11
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S158000, C422S214000, C422S215000
Reexamination Certificate
active
06517706
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process and apparatus for the treatment of hydrocarbon oils and, more particularly, to the hydroconversion of heavy hydrocarbon oils in the presence of particulate additives, e.g. iron and/or coal additives.
Hydroconversion processes for the conversion of heavy hydrocarbon oils to light and intermediate naphthas of good quality for reforming feedstocks, fuel oil and gas oil are well known. These heavy hydrocarbon oils can be such materials as petroleum crude oil, atmospheric tar bottoms products, vacuum tar bottoms products, heavy cycle oils, shale oils, coal derived liquids, crude oil residuum, topped crude oils and the heavy bituminous oils extracted from oil sands. Of particular interest are the oils extracted from oil sands and which contain wide boiling range materials from naphthas through kerosene, gas oil, pitch, etc., and which contain a large portion of material boiling above 524° C. equivalent atmospheric boiling point.
As the reserves of conventional crude oils decline, these heavy oils must be upgraded to meet the demand for lighter products. In this upgrading, the heavier materials are converted to lighter fractions and most of the sulphur, nitrogen and metals must be removed.
This can be done either by a coking process, such as delayed or fluidized coking, or by a hydrogen addition process such as thermal or catalytic hydrocracking. The distillate yield from the coking process is typically about 80 wt % and this process also yields substantial amounts of coke as by-product.
Work has also been done on a new processing route involving hydrogen addition at high pressures and temperatures and this has been found to be quite promising. In this process, hydrogen and heavy oil are pumped upwardly through an empty tubular reactor in the absence of any catalyst. It has been found that the high molecular weight compounds hydrogenate and/or hydrocrack into lower boiling materials. Simultaneous desulphurization, demetallization and denitrogenation reactions take place.
Additives have been developed which can suppress coking reactions or can remove the coke from the reactor. It has been shown in Khulbe et al, U.S. Pat. No. 4,923,838 issued May 8, 1990 that the formation of carbonaceous deposits in the reaction zone can be substantially reduced by mixing with a heavy oil feedstock a finely divided particulate consisting of carbonaceous particles and particles of an iron compound, e.g. an iron salt or oxide such as iron sulphate. The particles typically have average sizes of less than 10 &mgr;m. Canadian Patent No. 1,202,588 describes a process for hydrocracking heavy oils in the presence of an additive in the form of a dry mixture of coal and iron salt, such as iron sulphate.
A problem in the hydroprocessing of heavy hydrocarbon oil containing finely divided particulate, such as iron sulphate, is to achieve a good gas-liquid distribution in a reaction zone while avoiding coke formation and build-up. Bubble cap distribution plates are commonly used for gas-liquid distribution, e.g. as described in U.S. Pat. 4,874,583 issued Oct. 17, 1989, etc. However, when all gas, liquid and particulate are introduced into a lower region of a reaction zone below a bubble cap distribution plate, there is a problem that the bubble caps are quickly plugged and flow is reduced.
It is the object of the present invention to provide improvements to the mixing of hot hydrogen containing gas with heavy hydrocarbon oil in a hydrocracker and to ensure that additive particles are well mixed into the reactor contents and no settling occurs in the bottom head of the reactor.
SUMMARY OF THE INVENTION
According to the present invention, it has been discovered that further improvements in the hydroprocessing of heavy hydrocarbon oils containing additive particles to suppress coke formation are achieved by the manner in which the heavy hydrocarbon oil and additive particles are introduced into the bottom of a reactor and the manner in which hot hydrogen-containing gas is introduced into the mixture of heavy hydrocarbon oil and additive particles within the reactor.
Thus, one embodiment of the present invention in its broadest aspect relates to a process for hydrocracking a heavy hydrocarbon oil in which (a) a slurry feed comprising a mixture of a heavy hydrocarbon feedstock and from about 0.04 to 4.0% by weight (based on fresh feedstock) of coke-inhibiting additive particles having an average particle size of less than about 30 &mgr;m, preferably less than about 10 &mgr;m, and (b) a hydrogen-containing gas, are passed upwardly through a confined hydrocracking zone in a vertical, elongated, cylindrical vessel with a generally dome-shaped bottom head. The hydrocracking zone is maintained at a temperature between about 350° C. and 600° C. and a pressure of at least about 3.5 MPa. From the top of the hydrocracking zone there is removed a mixed effluent containing a gaseous phase comprising hydrogen and vaporous hydrocarbons and a liquid phase containing heavy hydrocarbons and particulates.
According to the novel features of this process, the slurry feed mixture and a portion of the hydrogen-containing gas (secondary gas) are fed into the hydrocracking zone through a feed injector at the bottom of the dome-shaped bottom head. The balance of the hydrogen-containing gas (main gas) is fed into the hydrocracking zone through a plurality of injection nozzles in the hydrocracking zone at a location above the slurry-feed injector. The temperature of the main hydrogen-containing gas entering through the nozzles is higher than the temperature of the combined slurry feed and hydrogen-containing gas entering through the bottom feed injector, and is generally sufficient to maintain the contents of the hydrocracking zone at a desired operating temperature. The main gas temperature is typically in the range of about 450 to 600° C., preferably about 450 to 540° C. The combined slurry feed and secondary gas entering through the bottom feed injector should enter at a velocity of at least 5 m/s whereby the additive particles are maintained in suspension throughout the reactor vessel and coking reactions are prevented. The combined slurry feed and secondary gas enters the reactor typically at a temperature in the range of about 300 to 430° C., preferably about 350 to 390° C. In a typical process according to the invention, the temperature of the vessel contents varies between about 440° C. in a lower region and 465° C. in an upper region.
The hydrogen-containing gas preferably comprises a recycle gas stream rich in hydrogen typically containing at least 60% hydrogen, and an important feature of this invention is the manner in which this hydrogen gas is introduced into the hydrocracking zone. In order to achieve a good contact between the main recycle hydrogen stream and the heavy hydrocarbon oil in the hydrocracking zone, it is important that the main recycle hydrogen stream be uniformly distributed within the hydrocracking zone in the form of high velocity jets, which provide high shear and mixing, producing small bubbles, to give large surface area for mass transfer from the hydrogen in the bubbles to the bulk liquid above the distributor.
In order to achieve these results, the main gas is preferably injected into the hydrocracking zone through injection nozzles that are arranged to assist in the uniform distribution of the content of the hydrocracking zone. The slurry feed and gas fed in through the bottom feed injector tends to create some central channelling of the flow within the hydrocracking zone. Thus, there is a tendency for much of the gas to flow up the middle of the reactor, with liquid and particulate flowing down the sides. It is, therefore, preferable to provide a lower central set of gas injector nozzles so that the gas flowing from the nozzles is adapted to disperse the central channelling in an outward direction toward the vessel walls. These lower nozzles are preferably arranged in a central circle with the nozzles aimed in an upward and outward direction.
Benham N. Kelly
Pruden Barry B.
Griffin Walter D.
Petro--Canada
LandOfFree
Hydrocracking of heavy hydrocarbon oils with improved gas... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrocracking of heavy hydrocarbon oils with improved gas..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrocracking of heavy hydrocarbon oils with improved gas... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3149762