Residue Hydrotreating and Catalytic Cracking Process
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Solution Overview
Problem
The existing processes for hydrotreating and catalytic cracking of residue face challenges such as poor operational stability, increased sulfur content, and reduced yield of light oils due to the circulation of heavy cycle oils and decanted oils, which also lead to higher coking quantities and increased load on regenerators, affecting the economic benefits of the catalytic cracking unit.
Innovation Solution
A combined process that includes a step for removing acidic solid impurities from catalytic cracking recycle oils before hydrotreating, ensuring they contain less than 30 ppm of particles smaller than 10 μm, followed by hydrotreating and catalytic cracking, which improves the stability and efficiency of both units by reducing carbon deposits and increasing the yield of light oils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic cracking heavy cycle oil is circulated to the catalytic cracking unit for further treatment, then the residue conversion is maximized, but the yield of light oil decreases and coking quantity increases
Solution Approach 1:
The circulation stream is segmented into two paths: one for hydrogenated tail oil that can be safely circulated, and another for heavy cycle oil that requires desulfurization treatment before circulation. This segmentation allows selective management of different feedstock streams based on their sulfur content and suitability for catalytic cracking.
Solution Approach 2:
Sulfur is extracted from the heavy cycle oil through a desulfurization unit before the oil is circulated back to the catalytic cracking unit. This extraction removes the harmful sulfur component that would otherwise increase coking and reduce light oil yield, while allowing the hydrocarbon portion to be reused.
2Productivity
If heavy cycle oil is circulated to the catalytic cracking unit, then residue utilization is improved, but sulfur content of products increases
Solution Approach 1:
The desulfurization unit converts the harmful sulfur component of heavy cycle oil into removable sulfur compounds, transforming a harmful feedstock into a beneficial low-sulfur circulation stream. This allows the hydrocarbon portion to be reused while eliminating the sulfur that would otherwise contaminate products.
3Productivity
If heavy cycle oil with high sulfur content is circulated, then catalytic cracking capacity is maintained, but regenerator load increases
Solution Approach 1:
Sulfur is extracted from heavy cycle oil before circulation, removing the source of excessive coking that would otherwise burden the regenerator. This extraction maintains catalytic cracking capacity by preserving hydrocarbon feedstock while eliminating the sulfur component that increases regenerator load.
4Reliability
If residue is hydrotreated and then catalytically cracked, then impurities are removed and hydrogen content increases, but operational stability decreases due to solid impurities in circulated oils
Solution Approach 1:
A desulfurization unit is introduced as an intermediary between the catalytic cracking unit and the hydrotreating unit. This intermediary removes solid impurities and sulfur from the circulated heavy cycle oil, preventing operational instability in the hydrotreating unit while maintaining the benefits of residue conversion.
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 process enhances the operational stability and efficiency of the hydrotreating and catalytic cracking units, increases the yield of light oils, decreases sulfur content, and prolongs the operation cycle of the hydrotreating unit by removing detrimental acidic solid particulates and optimizing the properties of the feedstock, thereby improving the overall refinery benefits.
Implementation Method 1
introducing residue and decanted oil together into residue hydrotreating unit to carry out hydrogenation reaction in the presence of hydrogen gas and hydrogenation catalysts
Implementation Method 2
introducing the hydrogenated residue obtained into catalytic cracking unit to carry out cracking reaction in the presence of cracking catalyst
Data Source
AI summary
Disclosed is a combined process for hydrotreating and catalytic cracking of residue, wherein the residue, catalytic cracking heavy cycle oil with acidic solid impurity being removed, optional distillate oil and adistillate of catalytic cracking slurry oil from which the acidic solid impurity is removed are fed into residue hydrotreating unit, the hydrogenated residue obtained and optional vacuum gas oil are fed into catalytic cracking unit to obtain various products; the catalytic cracking heavy cycle oil from which the acidic solid impurity is removed is circulated to the residue hydrotreating unit; the catalytic cracking slurry oil is separated by distilling, the distillate of the catalytic cracking slurry oil after removing off the acidic solid impurity is circulated to the residue hydrotreating unit. This process makes the residue hydrotreating and catalytic cracking being combined together more effectively such that it is not only able to improve product quality of the residue hydrotreating, elongate operation cycle of the residue hydrotreating unit, but also increases the yield of the hydrogenated diesel oil and catalytic cracking light oil, and decreases coking quantity of the catalytic cracking.