Hydrogen Recovery from Natural Gas Pipelines
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Solution Overview
Problem
Current methods for recovering hydrogen from hydrogen-enriched natural gas streams in natural gas pipeline grids are inefficient and costly, particularly when hydrogen content varies between 5 to 20 mol % to 50 mol %, as existing technologies like PSA and Pd membranes require higher hydrogen concentrations and are not economically viable for widespread use.
Innovation Solution
Implementing a multistage membrane separation process downstream of natural gas withdrawal sites, combined with pressure swing adsorption (PSA) for efficient recovery of pure hydrogen, using commercially available polymer membranes such as hollow fibre membranes based on polyimide or polyamide, which are flexible and adaptable to different capacities, and can handle impurities like O2 and CO2, followed by further purification in a PSA system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PSA or Pd membrane technology is used to recover hydrogen from hydrogen-enriched natural gas streams, then hydrogen recovery efficiency is improved, but the technology is not economically viable when hydrogen content is only 5 to 20 mol %
Solution Approach 1:
The patent employs a dynamic multistage separation approach where the number and configuration of membrane stages are adjusted based on the hydrogen concentration in the feed stream. For lower hydrogen concentrations (5-20 mol%), more stages are used, while for higher concentrations (30-50 mol%), fewer stages are sufficient. This dynamic adaptation allows the system to maintain economic viability across varying hydrogen content levels while achieving high recovery efficiency.
Solution Approach 2:
The system changes operational parameters including hydrogen concentration thresholds, pressure levels, and temperature conditions based on the feed composition. By monitoring the hydrogen content and adjusting separation parameters accordingly, the system optimizes the balance between recovery efficiency and economic feasibility for different hydrogen enrichment levels.
2Productivity
If dedicated hydrogen supply grid or complete conversion of natural gas conduits to hydrogen is implemented, then hydrogen transport capacity is improved, but capital costs become enormous
Solution Approach 1:
The patent enables natural gas pipelines to serve dual purposes: transporting both natural gas and hydrogen simultaneously. By implementing membrane separation units at strategic locations, the existing infrastructure can handle hydrogen blends without requiring complete pipeline replacement or dedicated hydrogen grid construction, thereby reducing capital investment while maintaining transport capacity.
Solution Approach 2:
Instead of complete conversion of the entire natural gas grid to hydrogen, the system implements partial hydrogen injection at specific points followed by selective recovery. This partial action approach allows utilization of existing infrastructure for the majority of the transport network, avoiding the enormous capital costs of full conversion while still achieving significant hydrogen transport capacity.
3Productivity
If multistage membrane separation is implemented downstream of natural gas withdrawal sites, then hydrogen recovery rate is improved, but system complexity increases
Solution Approach 1:
The separation system is divided into multiple independent membrane stages, each handling a specific portion of the hydrogen separation task. This segmentation allows each unit to be simpler in design while the collective system achieves high recovery rates. The modular nature of segmented stages also facilitates easier maintenance and operation compared to a single complex separation unit.
4Productivity
If hydrogen content in natural gas is increased to 50 mol % or higher, then hydrogen transport efficiency is improved, but regulatory limitations and material corrosion issues arise
Solution Approach 1:
The system performs preliminary hydrogen separation and recovery before the hydrogen-enriched natural gas reaches consumers or storage facilities. By removing excess hydrogen in advance through membrane units positioned downstream of injection points, the system prevents hydrogen from accumulating to levels that would cause corrosion or exceed regulatory limits, while still allowing efficient transport at moderate concentrations along the pipeline.
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 achieves high hydrogen recovery rates with lower losses to natural gas users, meets regulatory specifications, and allows for flexible adaptation to varying hydrogen demands, enabling efficient recovery of pure hydrogen from hydrogen-enriched natural gas streams, even at lower concentrations, and reduces capital and operating costs.
Implementation Method 1
separation of the discharged substream into a methane-enriched retentate stream and a hydrogen-enriched permeate stream
Implementation Method 2
the discharged substream is introduced into a PSA system, and a pure hydrogen stream and at least one PSA offgas stream are discharged from the PSA system
Data Source
AI summary
A method of transporting hydrogen and natural gas by means of a natural gas conduit system is proposed, especially by means of an existing natural gas conduit system. According to the invention, the hydrogen is recovered only downstream of one or preferably multiple natural gas consumers. This resulted in a stepwise increase in the hydrogen content in the natural gas-hydrogen mixture transported, and the subsequent recovery of the pure hydrogen can be affected more easily and efficiently.