Alkaline Extraction of Refinery Streams for Silicon Removal
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Solution Overview
Problem
Silicon-containing compounds, particularly polydimethylsiloxanes, pose a significant challenge in refinery hydrocarbon streams by causing catalyst deactivation in downstream refining units, leading to diminished catalyst performance and reduced cycle life.
Innovation Solution
Implementing an alkaline extraction step using agents like sodium hydroxide or potassium hydroxide to remove silicon compounds from refinery hydrocarbon streams before catalytic treatment, utilizing configurations such as scrubbing beds or trayed columns to enhance contact and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon trap catalysts are used to remove silicon compounds, then silicon removal capacity is improved, but hydroprocessing activity decreases
Solution Approach 1:
The process is divided into two distinct stages: first, an alkaline treatment stage that selectively removes silicon compounds; second, a hydroprocessing stage that performs sulfur and nitrogen removal. This segmentation allows each stage to be optimized independently, with the alkaline stage protecting catalysts from silicon poisoning while the hydroprocessing stage maintaining high activity for its specific function.
Solution Approach 2:
The alkaline treatment is applied as a preliminary step before hydroprocessing to pre-remove silicon compounds from the feed stream. This preliminary action protects the subsequent hydroprocessing catalyst from silicon poisoning, extending its lifecycle and maintaining its activity without requiring the catalyst to simultaneously perform both silicon removal and hydroprocessing functions.
2Duration of action of stationary object
If silicon trap catalysts are used to extend catalyst lifecycle, then catalyst life is improved, but reactor cycle duration decreases
Solution Approach 1:
By performing alkaline treatment as a preliminary step before hydroprocessing, silicon compounds are removed in advance, protecting the hydroprocessing catalyst from poisoning throughout the reactor cycle. This allows the catalyst to maintain full activity for the entire cycle duration without premature deactivation, effectively extending both catalyst life and reactor cycle duration.
Solution Approach 2:
The harmful silicon compounds are extracted from the feed stream through alkaline treatment before entering the hydroprocessing reactor. This extraction removes the catalyst poison separately from the main hydroprocessing function, allowing the reactor to operate at full capacity for extended periods without interruption for catalyst replacement or regeneration.
3Reliability
If alkaline extraction is implemented to remove silicon compounds, then catalyst protection is improved, but process complexity increases
Solution Approach 1:
An alkaline agent serves as an intermediary substance that facilitates the removal of silicon compounds through chemical reaction. The alkaline treatment unit acts as an intermediate step between the feed stream and the hydroprocessing catalyst, using a simple chemical mechanism (alkaline hydrolysis of silicon compounds) to protect the catalyst without requiring complex physical or chemical processes.
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
Significantly reduces silicon content in hydrocarbon streams, protecting catalysts from poisoning, enhancing process efficiency, and extending catalyst life by minimizing the need for silicon trap catalysts.
Implementation Method 1
a refinery hydrocarbon stream containing silicon compounds is contacted with an alkaline agent, such as sodium hydroxide, potassium hydroxide, or an amine. The contact facilitates the extraction of silicon-containing compounds from the hydrocarbon stream.
Data Source
AI summary
A method, process, and system are disclosed for removing silicon-containing compounds from refinery hydrocarbon streams using alkaline treatment. The refinery stream, which may originate from units such as a crude stream, delayed coker, or other process unit, is contacted with an alkaline agent, such as a solid or an aqueous solution of sodium hydroxide, potassium hydroxide, or an amine. This treatment extracts at least a portion of the silicon-containing compounds, including organic silicon species, from the hydrocarbon stream. The process may be applied to whole streams or specific fractions such as LPG, naphtha, kerosene, diesel, or coker gas oil. Following alkaline treatment, the hydrocarbon stream may be directed to a hydrotreating unit, where reduced silicon content reduces catalyst poisoning.