Autothermal Reformer CO2 Membrane Separation
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Solution Overview
Problem
Conventional autothermal reforming processes for hydrogen production from natural gas result in residual tail gas that is not pure carbon dioxide, requiring additional purification steps and leading to losses of methane and carbon monoxide, while also consuming excess steam and oxygen.
Innovation Solution
A gas separation process that includes a membrane-based carbon dioxide separation step followed by recycling the residual gas back to the autothermal reformer, utilizing membranes with high selectivity to carbon dioxide over hydrogen, which reduces steam consumption and minimizes losses of methane and carbon monoxide, allowing for efficient carbon dioxide recovery and increased hydrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional ATR process is used with PSA for hydrogen separation, then hydrogen production is achieved, but carbon dioxide recovery is incomplete and methane/carbon monoxide losses occur
Solution Approach 1:
The patent changes the separation mechanism from adsorption-based PSA to membrane-based separation, utilizing differences in gas permeability parameters. The membrane selectively allows CO2 to pass through while retaining CH4 and CO, fundamentally changing the separation parameter from adsorption affinity to permeability selectivity.
Solution Approach 2:
The membrane acts as an intermediary separation medium between the reformer and the product streams. It selectively transports CO2 from the synthesis gas while allowing CH4 and CO to remain in the retentate stream for recycling, serving as a selective gatekeeper that resolves the contradiction between CO2 recovery and hydrocarbon preservation.
2Productivity
If steam methane reforming is used, then hydrogen production is achieved, but large heat transfer surface and high capital cost are required
Solution Approach 1:
The patent merges the reforming reaction zone with the separation function by integrating the membrane directly into the reformer system. This allows the exothermic oxidation reactions to occur in close proximity to the membrane, utilizing the heat generated to drive the endothermic reforming reactions while simultaneously separating CO2 at the reaction site, eliminating the need for separate heat transfer surfaces.
Solution Approach 2:
The patent extracts the heat transfer requirement from the overall system by using the exothermic oxidation reactions to directly provide heat for the reforming reactions within the same reactor. This self-heating approach removes the need for external heat transfer surfaces and separate heating systems, reducing device complexity while maintaining hydrogen production efficiency.
3Ease of operation
If conventional ATR with tail gas discharge is used, then process simplicity is maintained, but carbon dioxide purification and impurity recovery are insufficient
Solution Approach 1:
The membrane serves as an intermediary separation device that automatically provides high-purity CO2 separation without complex control systems or multiple processing stages. The selective permeability of the membrane inherently achieves the required purity level, maintaining operational simplicity while dramatically improving CO2 purification precision.
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 process achieves substantial carbon dioxide recovery with minimized methane and carbon monoxide losses, reduces steam consumption, and enhances hydrogen yield by up to 20% compared to conventional methods, while maintaining comparable oxygen consumption.
Implementation Method 1
a membrane having a feed side and a permeate side, wherein the membrane is selective to carbon dioxide over hydrogen; passing the hydrogen-depleted gas mixture across the feed side; withdrawing from the permeate side a permeate stream that is enriched in carbon dioxide
Implementation Method 2
cooling the gas mixture to condense out water
Implementation Method 3
oxygen is added to the process, resulting in the additional reactions: CH4+O2→CO2+2H2; CH4+1⁄2O2→CO+2H2. The above reactions are exothermic
Implementation Method 4
Both methods work by exposing natural gas and steam to a catalyst (typically nickel) at high temperature
Data Source
AI summary
Disclosed herein is a process for the production of hydrogen by autothermal reforming of natural gas, with simultaneous recovery of carbon dioxide using carbon dioxide-selective membrane separation. Residual gas from the hydrogen and carbon dioxide recovery is recycled back to the autothermal reformer.