Fluidized Bed Reactor With Coke Control Zones for DMTO Selectivity
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Solution Overview
Problem
Existing DMTO industrial devices struggle to fully utilize the advantages of new generation DMTO catalysts with high methanol processing capacity and light olefin selectivity, particularly due to challenges in controlling coke content distribution and species, leading to inefficient light olefin production.
Innovation Solution
A fluidized bed reactor system with a coke control zone divided into subzones by baffles, allowing controlled catalyst residence time and coke content distribution, and a method for on-line modification of the catalyst using specific coke control raw materials to convert inactive large-molecule coke species into active small-molecule species like polymethylbenzene and polymethylnaphthalene, enhancing catalyst selectivity for light olefins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional DMTO device is used, then the basic light olefin production is achieved, but the coke content distribution in the catalyst is wide and light olefin selectivity is insufficient
Solution Approach 1:
The reaction zone is divided into multiple subzones (first subzone, second subzone, third subzone) with different operating conditions. The first subzone operates at lower temperature for initial conversion, while subsequent subzones operate at higher temperatures to progressively increase coke content and light olefin selectivity, thereby achieving narrow coke content distribution and high light olefin selectivity simultaneously
Solution Approach 2:
Different regions of the catalyst bed are assigned different functional qualities: the first subzone focuses on controlled conversion with lower temperature, while the second and third subzones are optimized for coke deposition and selectivity enhancement at higher temperatures. This local differentiation allows precise control over coke content distribution and light olefin selectivity
2Productivity
If the reaction temperature is increased to improve light olefin selectivity, then the selectivity increases, but the coking rate increases and heat transfer control becomes difficult
Solution Approach 1:
The reaction zone is segmented into multiple temperature zones (first subzone at lower temperature, second and third subzones at progressively higher temperatures). This segmentation allows the system to achieve high overall light olefin selectivity while maintaining controllable local temperatures, preventing runaway coking reactions that would occur in a single high-temperature zone
Solution Approach 2:
The first subzone performs preliminary conversion at lower temperature before the catalyst enters the higher temperature subzones. This preliminary action prepares the catalyst in a controlled manner, allowing subsequent high-temperature zones to operate more safely with better heat transfer control and reduced risk of excessive coking
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
The system achieves high selectivity for light olefins, with product gas containing 80-96 wt% light olefins, and reduces coking rates by controlling temperature and coke species, enabling direct use of regenerated catalyst without additional treatment.
Implementation Method 1
fluidized bed reactor
Implementation Method 2
DMTO (methanol-to-olefin) technology
Data Source
Figure 1
Figure 2
AI summary
The present application discloses a fluidized bed reactor, a device, and a production method. The fluidized bed reactor includes a main shell and a coke control zone shell; the main shell includes an upper shell and a lower shell; the upper shell encloses a gas-solid separation zone, and the lower shell encloses a reaction zone; the reaction zone axially communicates with the gas-solid separation zone; the coke control zone shell is circumferentially arranged on an outer wall of the main shell; the coke control zone shell and the main shell enclose an annular cavity, and the annular cavity is a coke control zone; n baffles are radially arranged in the coke control zone, and the n baffles divide the coke control zone into n coke control zone subzones, where n is an integer; the coke control zone subzones are provided with a coke control raw material inlet; and a catalyst circulation hole is formed in each of n-1 of the baffles, such that a catalyst entering the coke control zone flows in an annular direction. The fluidized bed reactor can control the coke content, coke content distribution, and coke species in a dimethyl ether/methanol to olefins (DMTO) catalyst, thereby controlling the performance of the DMTO catalyst and improving the selectivity for low-carbon olefins.