Mineral oils: processes and products – Chemical conversion of hydrocarbons – With preliminary treatment of feed
Reexamination Certificate
2001-09-25
2004-01-06
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With preliminary treatment of feed
C208S087000, C208S045000, C208S039000, C208S131000, C208S309000
Reexamination Certificate
active
06673234
ABSTRACT:
FIELD OF THE ART
The present invention is related to a multi-step process for treating hydrocarbon oil by means of a refining process and a cracking process in the absence of hydrogen. More particularly, it is a combined process of low degree solvent deasphalting and delayed coking.
BACKGROUND OF THE INVENTION
Solvent deasphalting is an important technology for upgrading residue. It is a physical liquid-liquid extraction process, the basic principle of which is to carry out separation according to the difference in the solubility of various components in residue in hydrocarbon solvents. Solvent mainly dissolves saturates and aromatics and removes most resin and asphaltene in residue by regulating the operation conditions and controlling the dissolving ability of the solvent, and thereby yields deasphalted oil which has high hydrogen/carbon ratio, low carbon residue, low impurity content and can meet the requirement of feed for the downstream process. A typical solvent deasphalting process comprises introducing the stock (usually vacuum residue) into the upper part of the extractor after heat exchange to attain an adequate temperature and introducing the solvent at a certain temperature from the lower part of the extractor. The two streams flow counter-currently and come into contact in the extractor. Resin and asphaltene settle in the bottom of the extractor and the deasphalted oil enters into the settling section via the pipe riser, and then the solvent in the deasphalted oil and the asphalt is recovered respectively. The solvent is recycled for reuse.
Delayed coking is a thermal processing technology which converts the residue into gas, gasoline, diesel, gas oil, and coke by deep thermal cracking. The process of the conventional delayed coking is: after preheating in the convection section of the furnace, the stock enters into the coking fractionator, and then enters into the radiation section of the furnace, wherein it is heated to 500° C. The heated stock enters the coker drum to carry out the coking reaction and producing coking distillate, oil and vapor escape from the top of the coker drum and enter into the fractionator to be separated into dry gas, gasoline, diesel, gas oil, while coke aggregates in the coker drum. The recycle ratio in the conventional delayed coking technology generally is 0.4.
The combination of solvent deasphalting with other heavy oil processing technologies has been a subject of research. For example, EP 209225A2 discloses a process for processing residues by combining a solvent deasphalting unit and a delayed coker. This process raises the linear velocity of the unrecovered solvent in the deoiled asphalt by vaporization in the furnace tube and makes full use of the heat source of the delayed coker to recover the solvent in the solvent deasphalting unit to achieve the goal of saving energy, but does not describe the reuse of the solvent.
V. K. Patel, et al set forth in “Economic Benefits of ROSE/Fluid Coking Integration, 1997 NPRA, AM-97-50” combining the solvent deasphalting ROSE technology with fluidized coking to process heavy residues at a deep degree. Meanwhile, they also suggest a scheme combined solvent deasphalting and delayed coking, i.e., coking the deoiled asphalt, but this technology has the problems that the deoiled asphalt becomes heavier and that the furnace tube is prone to coke, and so on.
U.S. Pat. No. 4,859,284 combines solvent deasphalting and coking for treating high softening point asphalt and applies a double-screw mixing reactor to the coking section. This process will encounter engineering problems in large-scale industrial production,
EP 673989A2 combines solvent deasphalting and pyrolysis and more than 50% of the obtained deasphalted oil selves as the feed of the pyrolysis unit to yield light oil products. Since the pyrolysis is restricted by coking, the conversion degree is affected.
The present invention uses a process which combines low degree solvent deasphalting and delayed coking, i.e. uses low degree deasphalted oil rather than deoiled asphalt as a part of the feed for delayed coking and thereby makes the yield of the deasphalted oil 70 wt %-95 wt % relative to the deasphalting stock. Only heavy asphalt is removed from the stock, and the soft asphalt still remains ill the feed for the delayed coker; therefore on the one hand, the coking of the furnace tube of the delayed coking is avoided and the operation period of the delayed coker is extended, on the other hand, the yield of the liquid products of delayed coking is raised. Meanwhile, the content of the impurities in coke is reduced, and the quality of the coke product is improved.
The object of the present invention is therefore to provide a combined process of low degree deasphalting and delayed coking based on the prior art.
In the steel production wherein high power electrode is used, it is necessary to use a high or ultra-high power graphite electrode being able to bear rapid changes in conditions in a short time. For the purpose of the electrodes not cracking due to a relatively large thermal stress in rapid heating or cooling, the coefficient of thermal expansion (CTE) becomes a key index of the petroleum coke product used for high power electrode. The petroleum coke used for high power electrode exhibits a needle shape in appearance after it is cracked, and has an obvious fiber structure in micrograph and has a strong anisotropy. It has a series of merits such as low CTE, and good graphitization ability. Therefore it is a skeleton material for fabricating high power electrodes and is widely applied in the fields of steel production, aerospace, etc.
The indices of the quality of the petroleum coke used for high power electrode are shown below:
Real density, g/cm
3
>2.12
CTE (RIPP method),×10
−6
/° C. 2.35-2.60
Sulfur content, wt % not more than 0.7
Ash, wt % not more than 0.15
The theoretical basis for the production technique of petroleum coke used for high power electrode is the formation mechanism of the mesophase and lie commonly used stock is catalytically cracking decanted oil, thermal cracking residue, extract from lube solvent refining and ethylene tar, etc. Although it is possible to produce petroleum coke used for high power electrode from the aforesaid stocks through different pretreating technologies, it is difficult to realize larger scale of production due to limited resources.
U.S. Pat. No. 4,178,229 discloses a process for producing premium petroleum coke from straight-run vacuum residue, wherein the vacuum residue first converts to distillate oil and asphalt, and the asphalt is cracked together with a hydrogen donor to produce the stock for producing premium petroleum coke. Since this patent uses a hydrocracking process to treat the residues the operation cost and expense are increased.
U.S. Pat. No. 4,130,475 discloses a process for producing premium petroleum coke from atmospheric residue, wherein the major stock is atmospheric residue and a small potion of residue for ethylene is incorporated therein. The mixture directly enter into a delayed coker without any other treatments, and the distillate oil produced in the coker subjects to thermal cracking reaction via two thermal cracking furnaces. The thermal cracking residue formed in the reaction returns to the feed inlet of the coker and mixes with the atmospheric residue. This patented technique exerts a special limit to the atmospheric residue stock since the atmospheric residue stock is not subjected to any chemical treatment, but only other stocks are added thereto and mixed. Therefore, the sources of the stock are restricted.
The present invention make the yield of the deasphalted oil 70 wt %-95 wt % by using a combined process of low degree deasphalting and delayed coking, wherein the low degree deasphalted oil rather than the deoiled asphalt serves as a part of the feed for the delayed coking. The low degree deasphalted oil is produced by only removing the asphaltene in the stock, and most of the oils and resins in the stock still remains, therefore on the one ha
Li Rui
Long Jun
Wang Zijun
Arnold Jr. James
China Petroleum and Chemical Corporation
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