Partial Condensation and PSA for Low-Hydrogen Refinery Gas
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Solution Overview
Problem
Current methods for recovering hydrogen from refinery gas streams with low hydrogen concentration are economically unfavorable due to high capital and operational costs, as they require extensive purification steps and high compression, making it uneconomical to recover hydrogen from streams with less than 30% hydrogen content.
Innovation Solution
A process utilizing partial condensation in an auto-refrigeration cold box and pressure swing adsorption (PSA) to recover high purity hydrogen and hydrocarbon-rich products from feed gases with less than 50 mole % hydrogen, which includes compressing and treating the feed gas, cooling it in a cold box, separating it to maximize hydrogen and hydrocarbon recovery, and using Joule-Thomson expansion for refrigeration, allowing for more flexible and cost-effective hydrogen recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional separation technologies are used to recover hydrogen from refinery gases with less than 30% hydrogen content, then hydrogen recovery is achieved, but the process becomes economically unfavorable due to high capital and operational costs
Solution Approach 1:
The patent changes the temperature parameter by implementing a cold box system that cools the feed gas to approximately -100°F, causing hydrocarbons to condense while hydrogen remains gaseous. This temperature parameter change enables separation of hydrogen from low-concentration refinery gases without requiring complex multi-step purification processes, making the recovery economically viable for gases with less than 30% hydrogen content
Solution Approach 2:
The patent utilizes phase transition by condensing hydrocarbons from the gas phase to liquid phase in the cold box at approximately -100°F, while hydrogen remains in the gas phase. This phase difference allows for simple gravitational separation, avoiding the need for complex separation technologies and reducing both capital and operational costs
2Manufacturing precision
If extensive purification steps and high compression are used to recover hydrogen, then high purity hydrogen is achieved, but capital and operational costs increase significantly
Solution Approach 1:
The patent performs preliminary cooling and condensation of hydrocarbons in the cold box before the PSA process. This preliminary action removes the majority of hydrocarbons from the feed gas, so that the subsequent PSA unit only needs to handle trace amounts, reducing the compression energy required and lowering both capital and operational costs while achieving high hydrogen purity
Solution Approach 2:
The patent extracts the bulk of hydrocarbons from the feed gas through condensation in the cold box, separating them from hydrogen before the PSA process. This extraction reduces the load on the PSA system, minimizing the compression energy needed for purification and reducing operational costs while maintaining high hydrogen purity
3Quantity of substance
If PSA is used on low hydrogen concentration streams, then hydrogen recovery is possible, but the process becomes uneconomical without pre-concentration
Solution Approach 1:
The patent changes the temperature parameter to approximately -100°F in the cold box, causing hydrocarbons to condense while hydrogen remains gaseous. This parameter change pre-concentrates hydrogen in the gas phase, enabling economical PSA operation on originally low-concentration streams and improving economic feasibility
Solution Approach 2:
The patent performs preliminary cooling and condensation in the cold box to concentrate hydrogen in the gas phase before PSA. This preliminary action transforms low-concentration refinery gases into a stream suitable for economical PSA operation, enabling hydrogen recovery that would otherwise be uneconomical
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 process reduces capital costs by simplifying the configuration and achieving high purity hydrogen recovery with lower hydrogen concentration requirements, enabling efficient recovery of hydrogen and hydrocarbon-rich products, such as methane-rich gas and LPG, while minimizing recompression needs and operational expenses.
Implementation Method 1
utilizing partial condensation in an auto-refrigeration cold box
Implementation Method 2
partial condensation in an auto-refrigeration cold box
Implementation Method 3
pressure swing adsorption (PSA) to recover high purity hydrogen
Data Source
AI summary
A process and system for recovering valuable by-products (e.g., hydrogen) from refinery gas streams. For hydrogen-only recovery, the invention comprises a partial condensation step to upgrade the refinery fuel gas to a minimum of 60% hydrogen, which is further purified in a pressure swing adsorption process. When configured to recover hydrogen, methane-rich gas and raw LPG (methane depleted gas containing C2 hydrocarbons and heavier), the invention comprises two partial condensation steps where the feed is cooled in the first step to allow separation of ethane and heavier hydrocarbons, and the resulting vapor is cooled to a lower temperature in a second step for hydrogen recovery.