Expanded Slurry Bed Reactor Aspect Ratio and Gas Velocity
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Solution Overview
Problem
There is a common belief that conversion in slurry bed hydrocarbon synthesis reactors declines with increasing gas velocity due to enhanced mixing at higher velocities, restricting conversion at high velocities, especially in reactors with a small aspect ratio of less than 5.
Innovation Solution
A process involving feeding gaseous reactants, such as CO and H2, into an expanded slurry bed of non-shifting hydrocarbon synthesis catalyst particles in a vessel with an aspect ratio of less than 5, maintaining catalyst suspension through high inlet superficial gas velocities of at least 35 cm/s, and recycling gases to achieve high CO plus H2 conversion and product formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas velocity is increased to improve mixing and mass transfer, then mass transfer efficiency improves, but conversion rapidly declines due to excessive mixing in reactors with small aspect ratio
Solution Approach 1:
The patent changes the geometric parameter of the reactor by using a large aspect ratio (greater than 5), which fundamentally alters the flow and mixing patterns within the reactor. This geometric parameter change allows the system to operate at high gas velocities while maintaining stable conversion, resolving the contradiction between mass transfer efficiency and conversion stability.
2Ease of operation
If high inlet superficial gas velocity is used to maintain catalyst suspension, then catalyst suspension is improved, but conversion is expected to decline according to conventional belief
Solution Approach 1:
The patent applies a large aspect ratio geometric parameter change that decouples the relationship between gas velocity and conversion. This allows the system to operate at high gas velocities (at least 35 cm/s) to maintain catalyst suspension while achieving high per pass conversion (at least 60%), contradicting conventional beliefs that high velocity necessarily reduces conversion.
3Device complexity
If reactor aspect ratio is kept small for compact design, then device complexity is reduced, but conversion is restricted at high gas velocities
Solution Approach 1:
The patent deliberately changes the geometric parameter by using a large aspect ratio (greater than 5), which increases device complexity but enables high conversion (at least 60% per pass) at high gas velocities. This parameter change resolves the contradiction by prioritizing productivity over compactness.
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 achieves high per pass CO plus H2 conversion rates of at least 60%, maintaining catalyst suspension and improving reactor productivity, contrary to the belief that conversion declines at high velocities, allowing for overall syngas conversions exceeding 80% in a single stage reactor.
Implementation Method 1
gaseous reactants and any recycled gas to react with a per pass CO plus H2 conversion of at least 60% as they pass upwardly through the slurry bed
Implementation Method 2
gaseous reactants and any recycled gas and any gaseous product assisting in maintaining the solid catalyst particles in suspension in the suspension liquid
Data Source
AI summary
A process for producing liquid and, optionally, gaseous products from gaseous reactants includes feeding at a low level a gaseous reactants feed comprising at least CO and H2 into an expanded slurry bed of solid non-shifting hydrocarbon synthesis catalyst particles suspended in a suspension liquid, the expanded slurry bed having an aspect ratio of less than 5. The gaseous reactants and any recycled gas are allowed to react with a per pass CO plus H2 conversion of at least 60% as they pass upwardly through the slurry bed at a gas velocity of at least 35 cm/s, thereby to form liquid and, optionally, gaseous products, and with the gaseous reactants and any recycled gas and any gaseous product assisting in maintaining the solid catalyst particles in suspension in the suspension liquid, and with the liquid product forming together with the suspension liquid, a liquid phase of the slurry bed.