Solids Circulation Loop for Char Conversion in Syngas Reactors
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Solution Overview
Problem
The challenge is to enhance carbon conversion in a steam reformer system while maintaining throughput and managing the increased demands on pulsed heater metallurgy due to higher operating temperatures, which results in suboptimal carbon conversion rates and requires additional processing steps to achieve high carbon conversion targets.
Innovation Solution
A solids circulation system is implemented, comprising a first reactor, a second reactor with a dense fluid bed, a riser, and separation devices to form a solids circulation loop that captures and converts char fines from the first reactor, providing additional residence time and a reactive environment for enhanced carbon conversion, and includes mechanisms to control fluid flow and pressure drops to optimize the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reformer operating temperature is increased to improve carbon conversion, then carbon conversion improves, but throughput decreases
Solution Approach 1:
The system divides the carbon conversion process into two stages: a steam reformer for initial processing and a char converter for additional carbon conversion. This segmentation allows the reformer to operate at optimal temperatures for throughput while the char converter handles the additional carbon conversion requirement, resolving the contradiction between conversion efficiency and throughput.
Solution Approach 2:
A char converter is introduced as an intermediary device between the steam reformer and the product output. This intermediary captures char fines from the reformer and provides additional residence time for carbon conversion, enabling the reformer to maintain higher throughput while achieving target carbon conversion levels through the combined system.
2Reliability
If reformer operating temperature is increased to improve carbon conversion, then carbon conversion improves, but heat dumping rate decreases while heat required increases
Solution Approach 1:
The system changes the operating parameters of the char converter, operating it at lower temperatures (650-1200°C) compared to the steam reformer. This parameter change allows the char converter to handle carbon conversion with different thermal requirements, reducing the overall heat demand while maintaining high carbon conversion through the combined process.
3Strength
If reformer temperature is set lower to reduce metallurgy demands, then metallurgy demands decrease, but carbon conversion does not approach target
Solution Approach 1:
The system segments the thermal processing into two distinct units: a steam reformer that can operate at lower temperatures with reduced metallurgy demands, and a char converter that provides the additional carbon conversion capability. This segmentation allows each unit to be optimized for its specific function, resolving the contradiction between metallurgy capability and carbon conversion target.
4Reliability
If a char converter is added to achieve high carbon conversion, then carbon conversion approaches target, but device complexity increases
Solution Approach 1:
The char converter is designed to be integrated with the existing steam reformer system, sharing common infrastructure such as the solids circulation loop, cyclone separators, and control systems. This merging approach reduces the incremental complexity of adding the char converter while achieving the target carbon conversion through the combined system.
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 allows for improved carbon conversion rates by capturing and converting char fines, maintaining efficient throughput, and achieving a desirable H2 to CO ratio for biofuel production, thereby overcoming the limitations of lower reformer temperatures and feedstock reactivity.
Implementation Method 1
The converter operates as a trim fluidized bed with an oxygen containing gas (air or enriched air or oxygen) as the fluidization medium and in a substoichiometric mode to gasify the carbon to primarily CO
Implementation Method 2
The converter operates as a trim fluidized bed with an oxygen containing gas (air or enriched air or oxygen) as the fluidization medium
Implementation Method 3
The products from the converter pass through third stage cyclone for solids retention and recycle and fourth stage cyclone to drop out the fly ash
Data Source
AI summary
A solids circulation system receives a gas stream containing char or other reacting solids from a first reactor. The solids circulation system includes a cyclone configured to receive the gas stream from the first reactor, a dipleg from the cyclone to a second reactor, and a riser from the second reactor which merges with the gas stream received by the cyclone. The second reactor has a dense fluid bed and converts the received materials to gaseous products. A conveying fluid transports a portion of the bed media from the second reactor through the riser to mix with the gas stream prior to cyclone entry. The bed media helps manipulate the solids that is received by the cyclone to facilitate flow of solids down the dipleg into the second reactor. The second reactor provides additional residence time, mixing and gas-solid contact for efficient conversion of char or reacting solids.