Syngas Stage Segmentation for CO2 Conversion and H2:CO Ratio Control
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Solution Overview
Problem
Existing carbon capture and utilization technologies face challenges in converting CO2 and H2 to synthesis gas with a desired H2:CO ratio without external hydrocarbon feeds, leading to inefficient energy use and by-product formation, and fail to fully utilize internal hydrocarbon streams for additional synthesis gas production.
Innovation Solution
A plant design incorporating a syngas stage with methanation and autothermal reforming sections, utilizing hydrogen and CO2 feeds to produce synthesis gas without external hydrocarbons, and recycling hydrocarbon streams for enhanced CO2 utilization, allowing for a desired H2:CO ratio and increased carbon dioxide conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If reverse water gas shift reaction is used to convert CO2 and H2 to synthesis gas, then carbon dioxide conversion is achieved, but very high temperatures are needed and significant energy input is required
Solution Approach 1:
The syngas stage is divided into multiple functional sections: a first section for water gas shift reaction, a second section for reverse water gas shift reaction, and a third section for methanation reaction. This segmentation allows each reaction to occur under optimized conditions, with the first section operating at lower temperatures and the subsequent sections handling CO2 conversion more efficiently, thereby reducing the overall energy input required compared to using a single high-temperature rWGS process.
Solution Approach 2:
The patent utilizes parameter changes by adjusting temperature, pressure, and gas composition across different reactor sections. The water gas shift section operates at conditions favoring CO2 production, while the reverse water gas shift section operates at conditions favoring CO production from CO2. This dynamic parameter adjustment enables efficient CO2 conversion without requiring uniformly high temperatures throughout the entire process, thus reducing energy consumption.
2Quantity of substance
If high H2/CO2 ratio is used to obtain high conversions of carbon dioxide, then carbon dioxide conversion is improved, but synthesis gas with too high H2/CO ratio is produced for downstream synthesis
Solution Approach 1:
The patent implements feedback control through the methanation section, which consumes excess H2 and CO to produce CH4. This section acts as a buffer that adjusts the H2/CO ratio of the synthesis gas based on the conversion needs of the rWGS section. By controlling the methanation reaction conditions, the system can maintain the desired H2/CO ratio in the final synthesis gas while still achieving high CO2 conversion through the rWGS reaction.
Solution Approach 2:
Different sections of the syngas stage have different local qualities optimized for specific functions. The water gas shift section has conditions optimized for CO2 production, the reverse water gas shift section has conditions optimized for CO production from CO2, and the methanation section has conditions optimized for adjusting the H2/CO ratio. This local optimization allows each section to perform its specific function efficiently, achieving both high CO2 conversion and precise H2/CO ratio control.
3Quantity of substance
If stand-alone reverse water gas shift process is used, then CO2 utilization is achieved, but internal hydrocarbon streams from downstream synthesis cannot be processed
Solution Approach 1:
The syngas stage is designed with multi-functionality to handle both CO2-rich streams and hydrocarbon-containing streams. The water gas shift section can process hydrocarbons to produce CO and H2, while the reverse water gas shift section can process CO2 to produce CO. The methanation section can process both CO and hydrocarbons. This universal design allows the system to effectively utilize both CO2 feeds and internal hydrocarbon streams from downstream synthesis, achieving high adaptability and versatility.
4Quantity of substance
If very high temperatures are used for reverse water gas shift reaction, then sufficient conversion of carbon dioxide is achieved, but undesired by-product formation such as methane occurs
Solution Approach 1:
The patent segments the CO2 conversion process into distinct sections: the water gas shift section that produces CO2 at moderate temperatures, the reverse water gas shift section that converts CO2 to CO at controlled temperatures, and the methanation section that handles methane production separately. This segmentation prevents the formation of unwanted methane by-products during the CO2 conversion process by keeping the rWGS section at temperatures that favor CO production while directing methane-forming reactions to the dedicated methanation section where they can be controlled.
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 solution enables efficient production of synthesis gas with a desired H2:CO ratio, reduces energy consumption, and maximizes CO2 utilization, making the process more economically feasible by eliminating the need for external hydrocarbon feeds and utilizing internal hydrocarbon streams for additional synthesis gas production.
Implementation Method 1
The reverse water gas shift reaction proceeds according to the following reaction: CO2+H2↔CO+H2O
Implementation Method 2
an autothermal reforming (ATR) section
Implementation Method 3
The ATR section is arranged to convert the fourth feed comprising hydrocarbons and the third feed comprising oxygen along with the remaining portions of the first and second feeds to a second syngas stream
Implementation Method 4
a syngas stage, said syngas stage comprising a methanation section and/or a reverse water gas shift (rWGS) section
Data Source
AI summary
A plant, such as a hydrocarbon plant, is provided, which has a syngas stage for syngas generation and a synthesis stage where the syngas is synthesized to produce syngas derived product, such as hydrocarbon product. The plant makes effective use of various streams; in particular, CO2 and H2. The plant does not comprise an external feed of hydrocarbons. A method for producing a product stream, such as a hydrocarbon product stream is also provided.