Electrically Heated Steam Methane Reforming for Hydrogen Production
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Solution Overview
Problem
The steam methane reforming (SMR) process for hydrogen production has a high carbon footprint due to the combustion of hydrocarbon fuels, leading to significant carbon dioxide emissions, and electrically heated SMR setups do not significantly reduce overall emissions when relying on PSA tail gas combustion for heat balance.
Innovation Solution
A process that includes a steam methane reforming step with electrical heat, a water-gas shift step, chemical scrubbing for carbon dioxide capture, and recycling of the off-gas stream to the feedstock, allowing for internal heat generation and reduced hydrocarbon consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hydrocarbon fuel combustion is used to provide heat for SMR, then the required heat for the endothermic reforming reaction is provided, but significant carbon dioxide emissions are generated
Solution Approach 1:
The patent changes the energy source parameter from hydrocarbon combustion to electricity conversion, transforming the heating mechanism while maintaining the required temperature for endothermic reforming. This parameter change eliminates direct CO2 emissions from the heating process.
Solution Approach 2:
The patent substitutes the chemical combustion process with an electrical heating process. Instead of using hydrocarbon fuel combustion to generate heat, the system uses electricity converted to heat through resistive or inductive heating elements, replacing the chemical energy conversion mechanism with an electrical one.
2Use of energy by moving object
If PSA tail gas combustion is used for heat balance in electrically heated SMR, then heat requirements are met, but overall carbon dioxide emissions are not significantly reduced
Solution Approach 1:
The patent extracts and removes the PSA tail gas combustion step from the process configuration. By eliminating this combustion source, the system avoids the associated CO2 emissions while meeting heat requirements through alternative means such as electrical heating or optimized heat integration from other process streams.
Solution Approach 2:
The patent implements self-service by using the off-gas stream recycled to the feedstock to internally satisfy heat requirements through the reforming reaction itself, rather than requiring external combustion. The system becomes self-sufficient by utilizing its own process streams for heat balance.
3Use of energy by moving object
If off-gas stream is burned for heat generation, then heat balance is achieved, but hydrocarbon feedstock consumption increases
Solution Approach 1:
The patent converts the previously harmful off-gas stream (which would be burned and cause emissions) into a beneficial recycled feedstock. By injecting the off-gas back into the reformer with the hydrocarbon feedstock, the system transforms a waste stream into a useful resource that contributes to the reforming reaction and reduces net feedstock consumption.
Solution Approach 2:
The patent recovers the off-gas stream that would otherwise be discarded through combustion. By recycling this stream back to the feedstock inlet, the system recovers valuable hydrocarbon content and uses it productively in the reforming reaction, eliminating the need to discard it via combustion.
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 significantly lowers direct and indirect carbon dioxide emissions and hydrocarbon feedstock consumption by utilizing recycled off-gas for heat generation, enhancing energy efficiency and reducing the carbon footprint of hydrogen production.
Implementation Method 1
wherein the heat for the endothermic reforming reaction is at least partially provided by converting electrical energy into heat
Implementation Method 2
The carbon dioxide in the shifted synthesis gas makes about 60% of the total direct carbon dioxide emissions of the SMR process. This share can be captured with relative ease owing to the high concentration/partial pressure of carbon dioxide in the shifted synthesis gas.
Implementation Method 3
steam methane reforming (SMR) step, wherein the heat for the endothermic reforming reaction is at least partially provided by converting electrical energy into heat
Data Source
AI summary
The invention relates to a process for producing hydrogen, having a steam methane reforming step for producing synthesis gas, in which heat for the endothermic reaction is at least partially provided by converting electrical energy into heat. The synthesis gas is subject to a water-gas shift step and the shift product is subject to a chemical scrubbing step, to afford a carbon dioxide product stream and a hydrogen raw product stream. The hydrogen raw product stream is further purified by means of a hydrogen production step, which affords pure hydrogen and an off-gas stream. The off-gas stream, rich in carbon monoxide and methane, is recycled to the hydrocarbon containing feedstock stream, so that a combined stream of hydrocarbon containing feedstock, off-gas and steam is supplied to the steam methane reforming (SMR) step.