Vacuum Residue Refining via Selective Deasphalting and Catalytic Cracking
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Solution Overview
Problem
Current processes for refining heavy hydrocarbon vacuum residue feedstocks with high sulfur, asphaltene, and metals content are inefficient, leading to suboptimal production of gasoline and light olefins, as they require preliminary conversion stages that result in poor quality products and operational challenges.
Innovation Solution
A process involving selective deasphalting followed by hydrotreatment and catalytic cracking, where a mixture of polar and apolar solvents is used for deasphalting under subcritical conditions to produce high-quality deasphalted oil, which is then treated in a fixed-bed reactor and further processed in a fluidized-bed reactor to maximize gasoline and light olefin production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional conversion units (visbreaking, coking, hydroconversion) are used to treat vacuum residue, then the feedstock can be processed, but the selectivity is directed towards diesel fuel cuts and the yields of gasoline and light olefins are disadvantaged
Solution Approach 1:
The invention changes the operating parameters and process conditions by using a fluidized-bed catalytic cracking unit with specific catalysts and conditions optimized for producing gasoline and light olefins, rather than the conventional diesel-oriented conversion units. This parameter change enables high-value product production from high-metals vacuum residue
Solution Approach 2:
The invention extracts and removes metals and sulfur from the vacuum residue feedstock through a desulfurization unit before the catalytic cracking stage. This preliminary extraction of harmful components enables the subsequent cracking unit to operate with high selectivity towards gasoline and light olefins without being poisoned by metals
2Reliability
If vacuum residue with high metals content (>70 ppm, even >200 ppm) is sent directly to RDS+RFCC scheme, then the process cannot be operated, but preliminary conversion stages are required which create operational difficulties
Solution Approach 1:
The invention performs preliminary desulfurization and metal removal in a dedicated unit before the RDS+RFCC scheme. This preliminary action of removing harmful components enables the main process to operate reliably without requiring multiple complex conversion stages
Solution Approach 2:
The invention introduces an intermediary desulfurization unit between the vacuum residue feedstock and the RDS+RFCC scheme. This intermediary unit acts as a mediator that prepares the feedstock by removing metals and sulfur, making it suitable for the subsequent process without requiring direct feeding of high-metals residue
3Ease of manufacture
If conversion units are used for vacuum residue, then processing is achieved, but the properties of light cuts are of poor quality and definitely require post-treatment
Solution Approach 1:
The invention changes the process parameters and sequence by performing desulfurization and metal removal before catalytic cracking, rather than after. This parameter change in process sequence and conditions produces light cuts with inherently better quality that require minimal or no post-treatment
4Productivity
If conventional deasphalting is used, then asphalt is removed, but the yield of deasphalted oil is not maximized and quality may not be sufficient for RDS+RFCC unit
Solution Approach 1:
The invention changes the deasphalting parameters by using specific solvent ratios, temperatures, and pressures optimized to maximize both the yield and quality of deasphalted oil. These parameter changes ensure the DAO is suitable for subsequent RDS+RFCC processing while achieving high yield
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the yield and quality of gasoline and light olefins, reduces metal and sulfur content, and optimizes the utilization of subsequent refining units, thereby improving overall production efficiency and product quality.
Implementation Method 1
a stage of selective deasphalting of the feedstock by a single-stage liquid/liquid extraction in an extractant, said extraction being carried out by means of a mixture of at least one polar solvent and at least one apolar solvent, said deasphalting stage being carried out under the subcritical conditions for the mixture of solvents
Implementation Method 2
a stage of hydrotreatment of at least a part of the deasphalted oil (DAO) phase originating from stage a) in the presence of hydrogen in at least one fixed-bed reactor containing at least one hydrodemetallization catalyst under conditions allowing an effluent to be obtained with a reduced content of metals and Conradson carbon
Implementation Method 3
a stage of hydrotreatment of at least a part of the deasphalted oil (DAO) phase originating from stage a) in the presence of hydrogen in at least one fixed-bed reactor containing at least one hydrodemetallization catalyst
Implementation Method 4
a stage of catalytic cracking of at least a part of the effluent from stage b) in at least one fluidized-bed reactor under conditions allowing a gasoline fraction and/or a light olefins fraction to be produced
Data Source
AI summary
The invention relates to a process for refining a heavy feedstock of the vacuum residue type. Selective deasphalting of the feedstock is conducted in a single-stage liquid/liquid extraction in an extractant. Extraction is carried out by means of a mixture of at least one polar solvent and at least one apolar solvent, to obtain an asphalt phase and a deasphalted oil (DAO) phase. The proportions of polar solvent and apolar solvent in the solvent mixture are adjusted according to properties of the feedstock, desired yield of asphalt and/or desired quality of the DAO. Deasphalting is implemented under subcritical conditions. At least a part of the DAO is subjected to hydrotreatment. At least a part of the effluent originating from the hydrotreatment is subjected to catalytic cracking in at least one fluidized-bed reactor under conditions allowing a gasoline fraction and/or a light olefins fraction to be produced.