Two-Stage Hydrocracking with Gas-Liquid Separator
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Solution Overview
Problem
Current hydrocracking processes are inefficient in converting heavy petroleum cuts into lighter fractions, leading to significant unconverted residues and overcracking of middle distillates, which reduces selectivity and yield of desired products like diesel oil.
Innovation Solution
A two-stage hydrocracking process incorporating an innovative gas/liquid separator in the first hydrocracking stage to recover diesel oil and limit cracking, combined with hydrodesulfurization, optimizing the process for higher selectivity and yield of middle distillates by minimizing sulfur and nitrogen exposure on catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-stage hydrocracking process is used to convert heavy petroleum cuts into lighter fractions, then the conversion of heavy feedstocks is achieved, but significant unconverted residues remain and selectivity for middle distillates is reduced
Solution Approach 1:
The hydrocracking process is divided into two distinct stages: a first hydrocracking stage operating at severe conditions to achieve high conversion of heavy feedstocks, followed by a second hydrocracking stage operating at mild conditions to selectively produce middle distillates. This segmentation allows each stage to be optimized for its specific function, resolving the contradiction between overall conversion and selective production.
Solution Approach 2:
A fractionation section is introduced as an intermediary between the two hydrocracking stages. This fractionation section separates the effluent from the first stage into converted products and unconverted fraction, directing the unconverted fraction to the second stage. This intermediary enables the process to maintain high conversion while protecting middle distillate selectivity in the second stage.
2Productivity
If the unconverted fraction is recycled to increase conversion, then the conversion increases, but the selectivity for gas oil and kerosene also increases due to overcracking
Solution Approach 1:
The process segments the hydrocracking operation into two stages with distinct functions. The first stage handles the bulk conversion of heavy feedstocks, while the second stage, receiving recycled unconverted fraction, is optimized to minimize overcracking. This segmentation allows the system to achieve high overall conversion while controlling unwanted overcracking reactions.
Solution Approach 2:
The process employs different operating parameters for the two stages. The first stage operates at severe conditions (higher temperature, pressure, and catalyst activity) to maximize conversion, while the second stage operates at mild conditions (lower temperature, pressure, and catalyst activity) to minimize overcracking. This parameter differentiation resolves the contradiction between conversion and overcracking control.
3Adaptability or versatility
If sulfur and nitrogen are present in the hydrocracking reactor, then the process can handle real feedstocks, but catalyst sensitivity increases and selectivity decreases
Solution Approach 1:
The process segments the treatment of different feedstock components across two stages. The first stage handles the bulk of sulfur and nitrogen removal through severe hydrocracking conditions, while the second stage operates with reduced sulfur and nitrogen content. This segmentation protects the catalyst in the second stage from excessive poisoning while maintaining the ability to treat real, sulfur-containing feedstocks.
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
The process enhances the yield and selectivity of middle distillates while reducing catalyst inhibitors, such as hydrogen disulfide and ammonia, thereby improving the overall efficiency and reducing capital costs by minimizing the volume of the hydrocracking section.
Implementation Method 1
a gas/liquid separation (S1) of the effluent from stage A with a separation device which comprises a chamber compartmentalized into an upstream degassing compartment and a downstream stripping compartment
Implementation Method 2
A hydrodesulfurization HDS of the gaseous effluent obtained in stage B and of an external liquid hydrocarbon feedstock
Implementation Method 3
A first hydrocracking HCK1 of the liquid effluent resulting from stage B in the presence of hydrogen and of a hydrocracking catalyst
Data Source
AI summary
A hydrocracking process:A. hydrotreating HDT the feedstocks,B. gas/liquid separation of effluent from A with a separation device having a chamber compartmentalized into an upstream degassing compartment and a downstream stripping compartment, the passage of the degassed liquid from the degassing compartment to the stripping compartment being provided by an opening made in the internal wall and/or by overflowing above the said internal wall separating the said compartments,C. hydrodesulfurization of gaseous effluent obtained in B and of an external feedstock,D. a first hydrocracking of liquid effluent resulting from B,E. gas/liquid separation of liquid effluent from D and of the liquid effluent from C,F. a fractionation of liquid effluent from E,G. a second hydrocracking of unconverted liquid fraction from F.