Two-Stage Hydrotreating Process for Silicon Removal
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Solution Overview
Problem
Hydrotreating catalysts in refineries face premature deactivation due to silicon deposits from silicone oils, leading to reduced cycle lengths and increased costs from frequent catalyst replacement and downtime, especially when processing coker naphthas.
Innovation Solution
A process involving at least two reactors in series for catalytic hydrotreating, where the first reactor operates at up to 410°C to reduce silicon compounds, followed by cooling and further treatment with a second reactor to reduce sulfur and nitrogen compounds, utilizing catalysts with metals like Co, Mo, and Ni on porous inorganic oxide supports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydrotreating reactor is used to treat silicon containing feedstock, then the process is simpler, but the catalyst deactivates prematurely due to silicon deposits reducing cycle length
Solution Approach 1:
The hydrotreating process is divided into two separate reactors: a first reactor dedicated to silicon removal and a second reactor for HDS/HDN. This segmentation allows each catalyst to be optimized for its specific function, preventing premature deactivation and extending overall cycle length despite increased system complexity.
Solution Approach 2:
The first reactor performs preliminary treatment by removing silicon compounds from the feedstock before it enters the second reactor. This preliminary action protects the second catalyst from silicon deposition, enabling longer operation times and extending the overall process cycle length.
2Quantity of substance
If temperature is increased to enhance silicon removal, then silicon uptake by catalyst increases, but sulfur recombination occurs in the product stream
Solution Approach 1:
The process separates silicon removal (first reactor at higher temperature) from HDS/HDN (second reactor at lower temperature). This segmentation allows high-temperature silicon uptake without causing sulfur recombination, as each function occurs in its own optimized temperature zone.
Solution Approach 2:
Silicon removal is performed as a preliminary step in the first reactor at elevated temperatures before the feed enters the second reactor. This preliminary action removes silicon before HDS/HDN reactions, preventing sulfur recombination while maintaining effective silicon uptake.
3Reliability
If catalyst replacement is performed frequently to maintain performance, then product quality is maintained, but production costs increase due to downtime and lost revenue
Solution Approach 1:
By segmenting the catalyst functions into two separate reactors with different operational requirements, the system extends the cycle length of each catalyst. This reduces the frequency of replacements and minimizes downtime, lowering production costs while maintaining product quality.
Solution Approach 2:
The first reactor performs preliminary silicon removal that protects the second catalyst, extending its operational life. This preliminary protection reduces the frequency of catalyst replacements and minimizes downtime, reducing losses from lost revenue and production interruptions.
4Loss of energy
If hydrogen partial pressure is reduced to lower operation pressure, then energy consumption decreases, but silicon removal efficiency is reduced
Solution Approach 1:
The process segments the functional requirements: the first reactor operates at higher hydrogen partial pressure for efficient silicon removal, while the second reactor operates at lower pressure for HDS/HDN. This segmentation allows energy-efficient operation overall while maintaining effective silicon removal in the dedicated reactor.
Solution Approach 2:
Different hydrogen partial pressures are applied locally to different reactors based on their specific functions. The first reactor receives higher hydrogen partial pressure for silicon removal, while the second reactor operates at lower pressure, optimizing both energy efficiency and removal effectiveness for each function.
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 extends the operation time and silicon capacity of hydrotreating catalysts, allowing for catalyst replacement without downtime and reducing production costs by maintaining efficient hydrogen partial-pressure and preventing sulfur recombination.
Implementation Method 1
contacting the feed stock in presence of hydrogen with a first hydrotreating catalyst being arranged in at least two reactors being connected in series at an outlet temperature of up to 410° C. to reduce content of the silicon compounds in the feed stock
Implementation Method 2
contacting the feed stock in presence of hydrogen with a first hydrotreating catalyst
Implementation Method 3
cooling of the such treated feed stock to a temperature of between 250° and 350° C.
Implementation Method 4
contacting the cooled feed stock with a second hydrotreating catalyst at conditions being effective in reduction of sulphur compound and nitrogen compound concentration
Implementation Method 5
contacting the cooled feed stock with a second hydrotreating catalyst
Data Source
AI summary
Process for the catalytic hydrotreating of a hydrocarbon feed stock containing silicon compounds comprising the steps ofcontacting the feed stock in presence of hydrogen with a first hydrotreating catalyst being arranged in at least two reactors being connected in series at an outlet temperature of up to 410° C. to reduce content of the silicon compounds in the feed stock;cooling of the feed stock such treated to a temperature of between 280° and 350° C.; andcontacting the cooled feed stock with a second hydrotreating catalyst at conditions being effective in reduction of sulphur compound and nitrogen compound concentration.