Mineral oils: processes and products – Asphalts – tars – pitches and resins; making – treating and... – Solvent extraction
Reexamination Certificate
1999-07-27
2001-06-05
Myers, Helane (Department: 1764)
Mineral oils: processes and products
Asphalts, tars, pitches and resins; making, treating and...
Solvent extraction
C208S309000, C208S067000, C208S106000, C208S950000
Reexamination Certificate
active
06241874
ABSTRACT:
FIELD OF THE INVENTION
The invention relates a process for the extraction and gasification of asphaltenes from oil, heavy oil, or vacuum or distillate residuum. More particularly, the invention relates to the integration of the gasification process and the deasphalting process to utilize what is otherwise waste heat from the gasification process, and to convert the low value asphaltenes to high value synthesis gas.
BACKGROUND OF THE INVENTION
Many crude oils contain significant quantities of asphaltenes. It is desirable to remove the asphaltenes from the oil, because asphaltenes tend to solidify and foul subsequent processing equipment, and because removal of asphaltenes lowers the viscosity of the oil. Solvent extraction of asphaltenes is used to process residual crude that produces Deasphalted Oil (DAO) which is subsequently catalyticly cracked and made into predominantly diesel. The deasphalting process typically involves contacting a heavy oil with a solvent. The solvent is typically an alkane such as, propane to pentanes. The solubility of the solvent in the heavy oil decreases as the temperature increases. A temperature is selected wherein substantially all the paraffinic hydrocarbons go into solution, but where a portion of the resins and the asphaltenes precipitate. Because solubility of the asphaltenes is low in this solvent-oil mixture, the asphaltenes precipitate, and are separated from the oil.
Then high pressure steam or a fired heater is typically used to heat the deasphalted oil-solvent mixture to sufficient temperature. The oil portion then separates from the solvent without having to vaporize the solvent. This reduces energy consumption by about 20 to 30 percent over separating off and recovering the solvent for re-use.
The choice of solvent depends on the quality of the oil. As the molecular weight of the solvent increases, the amount of solvent needed decreases but the selectivity, for example to resins and aromatics, decreases. Propane requires more solvent but also does not extract as much aromatics and resins. Solvent recovery costs are generally greater with lower molecular weight solvents.
The process and advantages of gasifying hydrocarbon material into synthesis gas are generally known in the industry. Hydrocarbon materials that have been gasified include solids, liquids, and mixtures thereof. Gasification involves mixing an oxygen-containing gas at quantities and under conditions sufficient to cause the partial oxidation of the hydrocarbon material into carbon monoxide and hydrogen. The gasification process is very exothermic. Gas temperatures in the gasification reactor are often above 1100° C. (2000° F.). The hot synthesis gas is often quenched with water, and then a portion of the remaining sensible heat in the gas is used to make steam. There is a temperature at which steam generation is no longer feasible. Remaining heat in the gas is then typically released to the atmosphere via fan coolers.
SUMMARY OF THE INVENTION
The invention is the integration of a process of gasifying asphaltenes in a gasification zone by partial oxidation and the process of asphaltene extraction with a solvent. The integration allows low level heat from the gasification reaction to be utilized in the recovery of solvent that was used to extract asphaltenes from an asphaltene-containing hydrocarbon material. Asphaltenes are extracted from an asphaltene-containing hydrocarbon material by mixing a solvent in quantities sufficient to precipitate at least a fraction of the asphaltenes. The precipitated asphaltenes and the parafinnic hydrocarbon material are then separated by any conventional means. It is not necessary to completely separate the parafinnic hydrocarbon material from the precipitated asphaltenes. Minor quantities of the parafinnic hydrocarbon material can be gasified with the asphaltenes. However, it is not desirable to gasify the parafinnic material because it is more valuable as catalytic cracker feedstock.
The precipitated asphaltenes are then gasified in a gasification zone to synthesis gas. The gasification process is very exothermic and the synthesis gas is very hot when leaving the gasification zone. The synthesis gas is often quenched and cooled via heat exchangers, wherein it is advantageous to generate steam. Both high pressure (or high quality) steam and low pressure (or low quality) steam can be generated sequentially. However, as the temperature of the synthesis gas declines, the quality of the steam declines, and there is a temperature where steam production is no longer feasible.
The low level heat in the synthesis gas, either directly, or via an intermediate step of low pressure steam, can be used to remove and recover the solvent from the parafinnic hydrocarbon material, also called deasphalted oil (DAO). The low level heat can also advantageously be used to remove the solvent from the precipitated and separated asphaltenes prior to gasification, especially if the asphaltenes have appreciable deasphalted hydrocarbon material, such as in a slurry.
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Barkley R. Walter
Johnson Kay A.
Kasbaum Janice L.
Niccum Jacquelyn Gayle
Thacker Pradeep S.
Howrey Simon Arnold & White
Myers Helane
Reinisch Morris N.
Texaco Inc.
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