Hydrocracking Process for LPG and BTX Production
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Solution Overview
Problem
Existing processes for converting naphtha to LPG suffer from an undesirably high ratio of C4 to C3 hydrocarbons and excessive methane production, which imbalances the C3 and C4 derivatives' volumes and limits the production of valuable petrochemicals like ethylene and propylene, and lack control over C4 production and composition.
Innovation Solution
A process where part of the C4 and C5 hydrocarbons from the first hydrocracking product stream are recycled back to the first hydrocracking unit instead of being subjected to a second hydrocracking, with the second hydrocracking being more severe to produce BTX, optimizing conditions to increase C2-C3 yield and decrease C1 production, while controlling the LPG composition by separating and recycling C4/C5 hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the severity of hydrocracking is increased to shift the products slate to ethane and propane, then the production of desired products (ethane and propane) is improved, but excessive methane is produced
Solution Approach 1:
The hydrocracking process is divided into two distinct stages with different severity levels. The first stage uses milder conditions to produce a balanced mixture, while the second stage uses severe conditions specifically to convert remaining heavy hydrocarbons to BTX. This segmentation allows optimization of each stage independently, achieving high ethane/propane production without excessive methane.
Solution Approach 2:
The process employs different operating parameters (temperature, pressure, catalyst type, WHSV) for the two hydrocracking stages. The first stage uses milder parameters to avoid excessive methane, while the second stage uses severe parameters to maximize BTX production from heavy fractions, thereby controlling the overall product distribution.
2Productivity
If a single hydrocracking reactor is used with high severity to maximize C2 production, then ethane production is improved, but methane production increases excessively
Solution Approach 1:
Instead of using a single reactor, the process employs two sequential hydrocracking reactors with different severity levels. The first reactor operates under milder conditions to produce ethane and propane with controlled methane generation, while the second reactor operates under severe conditions to convert remaining heavy hydrocarbons to BTX, thereby achieving high ethane production without excessive methane.
Solution Approach 2:
The process maintains continuous hydrocracking action through two sequential reactors, where the first reactor performs initial cracking to produce valuable C2-C4 products, and the second reactor continues the cracking of heavier fractions. This continuous action ensures complete conversion of feedstock while controlling product distribution to maximize ethane and minimize methane.
3Productivity
If C4 and C5 are subjected to second hydrocracking to produce BTX, then BTX production is improved, but C1 production increases due to more severe conditions
Solution Approach 1:
The process segments the hydrocarbon stream into different fractions based on carbon number before entering the second hydrocracking reactor. By separating C4-C6 from heavier fractions and processing them separately, the system can optimize the second hydrocracking conditions for BTX production from the heavier fractions while controlling the conversion of C4-C6 to minimize C1 formation.
Solution Approach 2:
Different portions of the hydrocarbon stream receive different treatment in the second hydrocracking unit. The C4-C6 fraction is processed under conditions optimized for BTX production, while the heavier fractions are processed under more severe conditions. This local differentiation of processing conditions allows simultaneous optimization of BTX production and control of C1 generation.
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 increases the proportion of valuable C2-C3 hydrocarbons and decreases the proportion of less valuable C1, C4, and C5 in the final product, achieving a balanced C3/C4 ratio and enhancing the production of desired petrochemicals like ethylene and propylene.
Implementation Method 1
A first hydrocracking unit (101) arranged for performing first hydrocracking of a mixed hydrocarbon feed stream (105) in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream (106)
Implementation Method 2
a separation unit (102) for separating the first hydrocracking product stream (106) arranged to provide at least a light hydrocarbon stream (107) comprising at least C2 and C3, a middle hydrocarbon stream (108) comprising C4 and/or C5 and a heavy hydrocarbon stream (112) comprising at least C6+
Implementation Method 3
a second hydrocracking unit (103) arranged for performing second hydrocracking of the heavy hydrocarbon stream (112) in the presence of a second hydrocracking catalyst to produce a second hydrocracking product stream (114) comprising BTX
Data Source
Figure 1
AI summary
The invention relates to a process for producing LPG and BTX, comprising a) subjecting a mixed hydrocarbon feedstream to first hydrocracking in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide at least a light hydrocarbon stream comprising at least C2 and C3 hydrocarbons, a middle hydrocarbon stream comprising C4 and/or C5 hydrocarbons and a heavy hydrocarbon stream comprising at least C6+ hydrocarbons and c) subjecting the heavy hydrocarbon stream to second hydrocracking to produce a second hydrocracking product stream comprising BTX, wherein the second hydrocracking is more severe than the first hydrocracking, wherein at least part of the middle hydrocarbon stream is recycled back to the first hydrocracking in step a).