Two-Stage Hydrotreating Process with Interstage Separation
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Solution Overview
Problem
Hydrotreating of residue streams, particularly desulfurization, faces challenges due to high severity requirements, metal saturation in catalysts, and coke buildup, leading to decreased reaction rates and inconsistent product quality.
Innovation Solution
The process involves injecting water into the feed and performing two-stage hydrotreating with interstage separation, where water improves HDM catalyst activity and separating hydrogen sulfide enhances HDS catalyst activity, resulting in a synergistic effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HDM catalyst is used at the reactor inlet to remove metals, then metal removal efficiency is improved, but catalyst activity decreases due to metal saturation and coke buildup
Solution Approach 1:
The hydrotreating process is divided into two separate stages: first stage with HDM catalyst for demetallization, and second stage with HDS catalyst for desulfurization. This segmentation allows each catalyst to perform its specific function without being poisoned by the other, resolving the contradiction between metal removal efficiency and catalyst activity maintenance
Solution Approach 2:
The harmful effect of metal saturation on HDM catalyst activity is extracted and addressed by removing metals in the first stage before the feed enters the HDS catalyst bed. The HDS catalyst is protected from metal poisoning by taking out the metal removal function into a separate preceding stage
2Productivity
If reactor temperature is increased to compensate for reaction rate decrease, then desulfurization rate is improved, but product quality consistency deteriorates
Solution Approach 1:
By segmenting the process into two stages with different catalyst functions, the system maintains stable reaction conditions in each stage. The HDM stage removes metals that would otherwise poison HDS catalyst, ensuring consistent HDS activity and product quality throughout the catalyst cycle life
Solution Approach 2:
Metal removal is performed as a preliminary action before desulfurization. By removing metals in advance in the first stage, the HDS catalyst maintains its activity without needing temperature compensation, thereby maintaining product quality consistency throughout operation
3Productivity
If HDM catalyst is fully utilized for metal removal, then metal saturation occurs, but downstream HDS catalyst activity is affected by metal breakthrough
Solution Approach 1:
The system is segmented into two functional stages: HDM catalyst bed for metal removal and HDS catalyst bed for desulfurization. This segmentation allows the HDM catalyst to be fully utilized for metal removal without compromising HDS catalyst activity, as metals are removed before the feed reaches the HDS catalyst
Solution Approach 2:
The metal removal function is extracted into a separate first stage, preventing metals from reaching and poisoning the HDS catalyst in the second stage. This extraction of the harmful metal-catalyst interaction resolves the contradiction between metal removal capacity and HDS catalyst activity
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 approach significantly improves demetallization and desulfurization rates, maintaining consistent temperature profiles and enhancing product quality by extending catalyst life and reducing unit shutdowns.
Implementation Method 1
Water injection improves the desulfurization activity of the HDM catalyst
Implementation Method 2
separating vapor comprising hydrogen sulfide from the demetallized effluent
Implementation Method 3
hydrotreating catalysts which are primarily active for the removal of heteroatoms, such as sulfur, nitrogen and metals
Data Source
Figure 1
AI summary
The subject process enhances catalytic activity for demetallization and desulfurization of a residue feed stream by injecting water into the feed and hydrotreating in two stages with interstage separation. Water injection improves the demetallation activity of the HDM catalyst and separating vapor comprising hydrogen sulfide from the demetallized effluent improves the activity of the HDS catalyst. We have discovered that the water injection and hydrogen sulfide removal together provide a profound synergetic effect.