Small Scale GTL Plant Oxygen Production via VPSA and ATR
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Solution Overview
Problem
Existing processes for small Gas-to-Liquid (GTL) plants are not energy efficient and cost-effective for converting natural gas to liquid hydrocarbons, particularly due to high energy requirements and capital costs associated with oxygen production and hydrogen handling.
Innovation Solution
The integration of a cryogenic air separation unit (ASU) with autothermal reforming or catalytic partial oxidation, combined with pressure swing adsorption (PSA) and Fischer-Tropsch tail gas recycle, to produce high-purity oxygen and hydrogen-rich streams, reducing energy consumption and capital expenses by utilizing smaller, less expensive equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cryogenic air separation unit is used to provide high-purity oxygen, then oxygen purity is improved, but capital cost and energy consumption increase
Solution Approach 1:
The patent uses VPSA technology to produce oxygen at lower pressures (2-10 bar) compared to conventional ASU, changing the operating pressure parameter to reduce energy consumption while maintaining sufficient purity (≥90%) for the reforming process
Solution Approach 2:
The patent employs adsorbent materials in the VPSA unit that can be regenerated cyclically, replacing the need for expensive and energy-intensive cryogenic separation equipment while achieving the required oxygen purity through periodic adsorption-desorption cycles
2Measurement precision
If a cryogenic air separation unit is used to provide high-purity oxygen, then oxygen purity is improved, but capital cost increases
Solution Approach 1:
The patent replaces expensive cryogenic ASU equipment with VPSA units using regenerable adsorbent materials, significantly reducing capital investment while achieving ≥90% oxygen purity suitable for autothermal reforming
Solution Approach 2:
The patent changes the oxygen production approach from cryogenic separation to pressure-swing adsorption, operating at lower pressures and using chemical adsorption principles to achieve the required purity at lower capital cost
3Loss of energy
If Fischer-Tropsch tail gas is recycled to the feed hydrocarbon stream, then energy efficiency is improved, but process complexity increases
Solution Approach 1:
The patent recycles Fischer-Tropsch tail gas containing unreacted CO and H2 back to the reforming unit feed, allowing the system to self-utilize its own byproducts as feedstock, improving energy efficiency by reducing fuel consumption and increasing overall carbon conversion efficiency
Solution Approach 2:
The patent implements a feedback loop where Fischer-Tropsch tail gas is routed back to the reforming unit, creating a closed-loop system that continuously optimizes gas utilization and minimizes energy loss while managing process complexity through integrated flow management
4Measurement precision
If pressure swing adsorption is used for hydrogen removal, then hydrogen purity is improved, but device complexity increases
Solution Approach 1:
The patent uses porous adsorbent materials in the PSA unit that selectively adsorb impurities from synthesis gas, producing high-purity hydrogen (≥99%) through physical adsorption mechanisms while maintaining relatively simple equipment configuration
Solution Approach 2:
The patent employs periodic adsorption-desorption cycles in the PSA unit, where adsorbent beds are alternately loaded with impurities and then regenerated by pressure reduction, achieving continuous high-purity hydrogen production through rhythmic operational phases
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 enhances energy efficiency and reduces costs by providing a more economical process for small GTL plants, capable of producing 500-5000 BPD of liquid hydrocarbons, while ensuring high oxygen purity and efficient hydrogen utilization.
Implementation Method 1
providing oxygen with a purity of at least 80% vol., preferably at least 85% vol., more preferably at least 90% vol., most preferably at least 95% vol., by using a cryogenic air separation unit (ASU)
Implementation Method 2
adding the oxygen of step (a) and the hydrocarbon-steam stream of step (b) to an autothermal reformer (ATR), or catalytic partial oxidation (CPO) unit
Implementation Method 3
mixing steam to the feed hydrocarbon stream to form a hydrocarbon-steam stream
Implementation Method 4
passing the second raw synthesis gas through a pressure swing adsorption (PSA) unit, withdrawing a hydrogen-rich stream and a PSA-off gas stream from the PSA unit
Implementation Method 5
converting the first raw synthesis gas from step (d) into liquid hydrocarbons through Fischer-Tropsch synthesis
Data Source
AI summary
A process and plant for conversion of a feed hydrocarbon stream to liquid hydrocarbon products in a small scale GTL plant, comprising the use of a cryogenic air separation unit (ASU), optionally together with vacuum pressure swing adsorption (VPSA), an autothermal reformer (ATR) or catalytic partial oxidation (CPO), and pressure swing adsorption (PSA) unit to produce a synthesis gas for downstream Fischer-Tropsch (FT) synthesis for production of liquid hydrocarbons.