Riser Methanol Injection for Xylene Yield
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Solution Overview
Problem
In the methylation of aromatics in an aromatics complex, the existing riser style reactors face challenges with catalyst velocity gradients and methanol injection inefficiencies, leading to decreased yield of xylene isomers due to poor mixing and penetration of methanol into the catalyst flow.
Innovation Solution
The use of riser slip reduction technology, specifically baffles positioned around the circumference of the reactor, improves methanol feed and catalyst contacting by creating a core-annulus structure that enhances mixing and prevents catalyst from settling, while distributors ensure effective methanol delivery at various radial positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If methanol is injected from the side of the riser, then the injection system is simple, but the methanol cannot penetrate and mix into the main catalyst flow due to high upward momentum
Solution Approach 1:
The riser is divided into different zones: a lower section with catalyst injection and an upper section with methanol injection. This spatial segmentation allows each injection to occur in a zone where it can be effective, with the methanol being injected after the catalyst has slowed down in the upper section.
Solution Approach 2:
Instead of injecting methanol radially from the side wall, the injection is directed axially downward along the riser wall. This dimensional change in injection direction allows the methanol to counteract the upward catalyst flow and achieve proper mixing.
2Productivity
If catalyst flows co-currently up the riser with high velocity, then the riser operates efficiently, but catalyst slows down and falls along the wall creating velocity gradient
Solution Approach 1:
Different regions of the riser are given different functions: the lower section handles catalyst injection and upward transport, while the upper section is designed for methanol injection and mixing. This local differentiation allows each zone to optimize its specific function without compromising overall performance.
Solution Approach 2:
The riser wall acts as an intermediary surface where methanol is injected downward to interact with the upward catalyst flow. This wall-mediated injection method facilitates mixing between the two streams without requiring direct radial penetration against the high-velocity core flow.
3Productivity
If methanol injection is performed at various locations above main feed point, then yield advantage is achieved, but poor mixing reduces effectiveness
Solution Approach 1:
Multiple methanol injection points are distributed at different heights above the main feed point, creating periodic injection zones along the riser. This periodic arrangement ensures continuous mixing and reaction opportunities, maintaining high yield while improving mixing effectiveness at each location.
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 increases the yield of xylene isomers by improving the interaction between methanol and catalyst, leading to enhanced product yield rates and reduced catalyst settling, thus optimizing the methylation process.
Implementation Method 1
improving the methanol feed and catalyst contacting by creating a core-annulus structure that enhances mixing
Implementation Method 2
the feed and catalyst flowing co-currently up the riser
Data Source
AI summary
This present disclosure relates to apparatuses for methylation of aromatics in an aromatics complex for producing a xylene isomer product. More specifically, the present disclosure relates to apparatuses for producing para-xylene by the selective methylation of toluene and/or benzene in an aromatics complex using processed toluene instead of crude toluene.