Integrated FCCU Desulfurization via Second-Stage Cracking
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Solution Overview
Problem
Conventional fluid catalytic cracking units (FCCUs) face challenges in efficiently processing low aromatic sulfur feedstocks, leading to heat balance issues and limited sulfur reduction in gasoline products, particularly when handling severely hydrotreated or tar sands-derived feedstocks, which require additional processing steps and energy consumption.
Innovation Solution
The integration of a second-stage cracking system with a Riser Termination Device (RTD) and the use of sulfur reduction additives like RESOLVE®, where condensed aromatics are injected into the stripper to generate coke and adjust heat balance, and light cycle oil is converted into coke in a high catalyst-to-oil ratio system, decoupling heat balance from hydrotreating unit severity and reducing sulfur recombination reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional FCCU processes are used to process low aromatic sulfur feedstocks, then the existing processing configuration is maintained, but heat balance issues occur and sulfur reduction in gasoline products is limited
Solution Approach 1:
The FCCU process is divided into two independent cracking systems: a first-stage cracking system for initial feedstock conversion and a second-stage cracking system for targeted sulfur reduction. This segmentation allows each stage to be optimized independently, with the second stage specifically designed to address sulfur content while the first stage maintains overall process heat balance.
Solution Approach 2:
A cyclic intermediate stream is introduced between the first and second cracking stages. This intermediate stream acts as a mediator that carries selected hydrocarbon components from the first stage to the second stage, enabling controlled sulfur reduction while maintaining heat balance through the cyclic nature of the intermediate stream.
2Manufacturing precision
If additional processing steps are added to reduce sulfur content, then sulfur reduction efficiency improves, but processing complexity and energy consumption increase
Solution Approach 1:
Two cracking functions (initial conversion and sulfur reduction) are merged into a single integrated FCCU system with two stages. This combining approach achieves sophisticated sulfur reduction without requiring separate standalone processing units, thereby limiting the increase in overall processing complexity while still delivering enhanced sulfur removal capability.
Solution Approach 2:
The second-stage cracking system serves multiple functions simultaneously: it reduces sulfur content in the gasoline product, processes the cyclic intermediate stream from the first stage, and contributes to overall heat balance management. This multi-functionality reduces the need for additional dedicated processing steps.
3Manufacturing precision
If hydrotreating unit severity is increased to improve sulfur removal, then sulfur reduction improves, but energy consumption and processing complexity increase
Solution Approach 1:
The cyclic intermediate stream serves as an intermediary that selectively transports hydrocarbon components requiring sulfur reduction to the second cracking stage. This targeted approach allows sulfur removal to be concentrated in the second stage rather than requiring severe hydrotreating of the entire feedstream, thereby reducing overall energy consumption.
Solution Approach 2:
The sulfur reduction function is segmented and concentrated in the second-stage cracking system rather than being distributed throughout the entire processing system. This segmentation allows the second stage to be optimized specifically for sulfur removal using catalysts and conditions tailored for this purpose, while the first stage maintains milder operating conditions for overall heat balance.
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 configuration enables independent heat balance control, reduces delta coke, enhances sulfur reduction efficiency, and allows processing of a wider range of feedstocks, including high sulfur content materials, while simplifying the hydroprocessing scheme and improving energy efficiency.
Implementation Method 1
contacting the feedstock with a catalyst in a reactor to crack the feedstock and produce a cracked product
Implementation Method 2
burning off coke from the catalyst in a regenerator
Data Source
AI summary
The present invention is describes a novel technique for producing commercial hydrocarbon materials using a fluid catalytic cracking unit employing recycling of light cycle oil in combination with desulfurization catalysts.