Two-Zone Catalyst Stripping for Volatile Hydrocarbon Removal
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Solution Overview
Problem
Current catalyst stripping processes are inefficient in removing volatile hydrocarbons, leading to equipment damage and reduced plant operation time due to incomplete stripping at low temperature conditions, which fails to effectively prepare catalysts for regeneration.
Innovation Solution
A two-zone process is implemented, where a stripping zone operates at higher severity conditions to remove a substantial portion of residual volatile hydrocarbons, followed by a cooling zone at lower severity conditions to ensure minimal hydrocarbons remain on the catalyst, using counter-current gas flows and temperature control between 200°C to 650°C and 38°C to 300°C respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low temperature stripping is used to operate the stripper, then the catalyst can be lifted or transported to the regenerator, but insufficient stripping of volatile hydrocarbon species occurs
Solution Approach 1:
The stripping process is divided into two distinct zones: a high-temperature stripping zone (200-650°C) for removing volatile hydrocarbons and a low-temperature cooling zone (38-300°C) for catalyst cooling and transport preparation. This segmentation allows each zone to optimize its specific function, resolving the contradiction between stripping effectiveness and ease of operation.
Solution Approach 2:
Different temperature conditions are applied to different parts of the catalyst bed: the upper portion experiences high temperature for efficient stripping, while the lower portion experiences low temperature for safe transport. This local quality approach allows simultaneous achievement of effective stripping and safe handling.
2Reliability
If high severity temperatures are used to strip volatile hydrocarbons, then substantial removal of volatilizable carbonaceous materials is achieved, but equipment damage and plant shutdowns occur due to improper stripping
Solution Approach 1:
The high-temperature stripping zone performs preliminary removal of volatile hydrocarbons before the catalyst enters the regenerator. By conducting this preliminary action at controlled temperatures, the system prevents the harmful effects of residual hydrocarbons decomposing in downstream equipment while avoiding the need for excessively high temperatures that would cause equipment damage.
Solution Approach 2:
The two-zone stripping system acts as an intermediary between the catalyst and the regenerator, removing problematic volatile hydrocarbons in a controlled manner before the catalyst enters the regenerator, thereby protecting downstream equipment from damage.
3Device complexity
If a single stripping zone is used, then device complexity is reduced, but insufficient removal of residual volatile hydrocarbons occurs
Solution Approach 1:
The stripper is segmented into two functional zones within a single vessel: an upper stripping zone with high-temperature gas flow for hydrocarbon removal and a lower cooling zone with low-temperature gas flow for catalyst cooling. This segmentation achieves effective multi-functionality while maintaining relative structural simplicity.
Solution Approach 2:
The single stripper vessel performs multiple functions: high-temperature stripping of volatile hydrocarbons, cooling of the catalyst, and preparation for transport. By integrating these functions into one device with zoned operation, the system achieves multi-functionality without requiring multiple separate units.
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 effectively eliminates high levels of residual volatile hydrocarbons, preventing downstream equipment issues and ensuring the catalyst is suitable for regeneration, while maintaining a minimal stripping zone size.
Implementation Method 1
a first gas stream comprising gas is passed to an upper stripping zone... to remove a substantial portion of residual volatile hydrocarbons
Implementation Method 2
The first gas is distributed around the stripping zone and flows through the catalyst countercurrently passing up through the first stripping zone
Implementation Method 3
The second gas flows up through the cooling zone and flows counter currently against the catalyst before exiting the cooling zone
Implementation Method 4
the stripped catalyst moves to a cooling zone to be cooled at lower severity conditions
Data Source
AI summary
A process is disclosed for an improved catalyst stripping process. The stripping vessel is divided into two zones. The first zone is a stripping zone where a substantial portion of the volatile hydrocarbons is removed at higher severity conditions. After the catalyst is stripped, the stripped catalyst moves to the lower cooling zone to be cooled at lower severity conditions. The flow rates, temperatures, pressures and the stripping and cooling zones are designed to ensure there is minimal volatile hydrocarbons on the catalyst by the time it leaves the stripping vessel. This design enables efficient stripping of volatile hydrocarbons at high severity conditions and eliminates these components from being stripped off elsewhere in the unit causing process and equipment issues.