Two-Stage Slurry Hydrocracking for Residual Hydrocarbon Conversion
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Solution Overview
Problem
Existing resid hydrocracking processes face limitations in achieving high conversion rates due to the presence of high concentrations of asphaltenes and coke precursors, leading to fouling and reduced production of light distillates.
Innovation Solution
A process involving hydrocracking in a primary unit, followed by fractionation, mixing with hydrogen and catalyst, processing in a slurry hydrocracking reactor, and recycling unconverted residues to enhance conversion, utilizing a slurry hydrocracking reactor with dispersed catalysts to maximize distillate production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrocracking conversion is increased beyond optimum level, then light product yield is improved, but sediment and coke precursors form leading to increased fouling in downstream equipment
Solution Approach 1:
The hydrocracking process is divided into two distinct stages: a first hydrocracking unit operating at moderate conversion (70-80%) to produce initial light products while limiting coke formation, and a second hydrocracking unit processing the unconverted residue to achieve additional conversion. This segmentation allows each unit to operate within optimal parameters, preventing excessive coke precursor formation while maximizing overall light product yield.
Solution Approach 2:
The unconverted hydrocracked vacuum residue acts as an intermediary stream between the first and second hydrocracking units. This intermediate stream contains the heavy molecules that were not converted in the first unit, and serves as the feed for the second unit where further conversion occurs under controlled conditions with appropriate catalyst selection, thereby converting potential coke precursors into valuable light products.
2Productivity
If conversion of vacuum resid is increased to improve process economics, then light distillate production is improved, but high concentration of asphaltenes in unconverted portion limits further conversion
Solution Approach 1:
The process employs parameter changes by selecting different catalyst types for each hydrocracking unit. The first unit uses a catalyst optimized for initial cracking, while the second unit employs a different catalyst specifically selected to handle the challenging asphaltenic residue from the first unit. This catalyst parameter change enables effective conversion of the difficult-to-crack asphaltene-containing stream, improving overall conversion and process economics.
3Reliability
If moderate conversion is maintained to avoid fouling, then downstream equipment fouling is reduced, but light product yield is limited
Solution Approach 1:
The process merges two hydrocracking units with different operational characteristics into a unified two-stage system. The first unit operates at moderate conversion to protect downstream equipment, while the second unit processes the unconverted residue to generate additional light products. By combining these two units and integrating their functions, the process achieves both equipment reliability and enhanced light product yield that would not be possible with a single unit operating alone.
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
Achieves enhanced conversion of residual hydrocarbons to lighter distillates, reducing pitch yield and increasing overall process efficiency with conversions up to 97%, while minimizing unconverted residues.
Implementation Method 1
mixing the hydrocracked vacuum resid fraction (3b) with a diluent (6) in the presence of hydrogen (4) and a catalyst (5) to form a mixed feed stream, wherein the catalyst is dispersed in the mixed feed stream
Implementation Method 2
processing the mixed feed stream in a secondary conversion unit to obtain a stream of liquid effluents and vapour effluents, wherein the secondary conversion unit is a slurry hydrocracking reactor (7)
Implementation Method 3
sending the liquid effluents to a fractionation column (9) to separate a lighter distillate (9a), a middle distillate (9b), a vacuum gas oil (9c) an unconverted slurry hydrocracked pitch residue (9d) and a slurry hydrocracked bottom pitch (9e)
Data Source
Figure 1
AI summary
The present invention relates to a process for upgradation of cracked residual hydrocarbons. More specifically, the present invention relates to a process for upgradation of cracked residual hydrocarbons into distillates in the presence of a catalyst in a slurry hydrocracking reactor (7). The slurry hydrocracking reactor (7) maximizes the conversions of hydrocarbons to distillate products and reduces the bottom unconverted fraction. The slurry hydrocracking reactor (7) enhances residue conversions to greater than 97 % with reduced purge.