Dual-Stage Bio-Based LPG Synthesis for Low-Loss Gas Recycling
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Solution Overview
Problem
Conventional methods for producing liquefied petroleum gas (LPG) from bio-based sources face challenges such as high losses of hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2), and inefficiencies in recycling unreacted synthesis gas components, leading to reduced yields and increased energy costs.
Innovation Solution
A dual-stage process involving an oxygenate synthesis reaction zone and an oxygenate conversion reaction zone, combined with selective absorption and adsorption techniques, to recover LPG while recycling unreacted gases, minimizing pressure loss and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional recycling processes are used to recover unreacted synthesis gas, then hydrogen recovery is achieved, but significant energy costs are incurred due to recompression
Solution Approach 1:
The patent segments the synthesis gas stream into different components and recycles them through different pathways. Light gases (H2, CO, CO2) are separated from the effluent and recycled without recompression, while the heavier hydrocarbon products are condensed and separated. This segmentation allows hydrogen-rich streams to be recycled with minimal energy input.
Solution Approach 2:
The patent introduces an intermediary cooling and condensation step that separates the synthesis gas components based on their condensation temperatures. By using temperature as the separation mechanism, the system avoids the need for mechanical recompression of the recycled gas streams, thereby reducing energy consumption.
2Productivity
If conventional processing is used, then synthesis gas is converted to LPG, but over 10% of carbon is lost as carbon dioxide
Solution Approach 1:
The patent recovers carbon dioxide that would otherwise be discarded by incorporating it back into the synthesis gas feed stream. The CO2 separated during the recycling process is blended with the synthesis gas, thereby recovering the carbon resource and reducing overall carbon loss to the atmosphere.
Solution Approach 2:
The patent implements a feedback loop where unreacted synthesis gas components including CO2 are recycled back to the reactor inlet. This feedback mechanism ensures that carbon atoms that did not convert to LPG in one pass are given another opportunity to react, thereby reducing carbon loss and improving overall conversion efficiency.
3Productivity
If dual-stage synthesis is used to produce LPG from bio-based sources, then high LPG yields are achieved, but complex separation and recycling systems are required
Solution Approach 1:
The patent utilizes phase transitions (condensation) to simplify the separation process. By cooling the effluent stream, hydrocarbon products condense into the liquid phase while synthesis gas components remain in the gas phase, enabling straightforward separation without complex separation equipment.
Solution Approach 2:
The patent changes the temperature parameter to achieve separation. By controlling the temperature of the effluent stream, the system exploits the different condensation points of hydrocarbons and synthesis gas components to separate them, avoiding the need for complex mechanical separation systems.
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 high LPG yields with minimal loss of valuable synthesis gas components, reducing energy consumption and environmental footprint by efficiently recycling unreacted gases and recovering LPG.
Implementation Method 1
contacting the third effluent with a liquid absorption solvent in an absorption zone, absorbing C3+ hydrocarbons from the third effluent
Implementation Method 2
contacting a fourth effluent with a solid adsorbent for adsorbing at least a portion of the light gases
Data Source
AI summary
A method is provided for synthesizing bio-based LPG from renewable sources via a bio-based synthetic gas feedstock, in a dual-stage reaction system comprising an oxygenate synthesis reaction zone and an oxygenate conversion reaction zone that are configured for producing and converting a methanol intermediate for reduced CO2 selectivity. The method includes recovering LPG from either the full reaction zone effluent or from a purge stream separated from the full reaction zone effluent for LPG recovery.