Hydrogen and LPG Recovery via Sponge Absorption Pressure Increase
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for recovering hydrogen and liquefied petroleum gas (LPG) from hydroprocessed hydrocarbon streams are inefficient, particularly due to low pressure conditions that prevent effective recovery in hydrogen recovery units, resulting in lost hydrogen and suboptimal LPG recovery.
Innovation Solution
Increasing the pressure of gaseous streams from hydroprocessing units, specifically the stripper and fractionator streams, and subjecting them to sponge absorption processes in series to enhance the recovery of hydrogen and LPG, allowing for simultaneous recovery in a light materials recovery unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure of stripper gaseous stream is increased, then hydrogen recovery efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by increasing the pressure of the stripper gaseous stream from typical low pressure (e.g., 1-5 psig) to elevated pressure (e.g., 50-150 psig). This pressure parameter change enables the gas stream to be directly fed to the sponge absorber without additional compression, improving hydrogen recovery efficiency while the energy penalty is offset by process integration
Solution Approach 2:
The patent merges the stripper overhead gas stream with the flash drum overhead gas stream, combining two separate gas handling streams into one unified feed for the sponge absorber. This integration allows simultaneous recovery of hydrogen and LPG from both streams, improving overall recovery efficiency while reducing the number of separate processing units required
2Productivity
If pressure of stripper gaseous stream is increased, then LPG recovery is improved, but operating cost increases
Solution Approach 1:
The patent changes the pressure parameter of the stripper gaseous stream to elevated levels (50-150 psig), which enhances LPG condensation and absorption in the sponge absorber. This pressure increase improves LPG recovery by 10% weight while the operating cost increase is mitigated by eliminating separate compression equipment and integrating with existing high-pressure process streams
Solution Approach 2:
The patent introduces a high-pressure separator or flash drum as an intermediary device that receives the stripper overhead gas at elevated pressure and separates condensed LPG before the gas enters the sponge absorber. This intermediary separation improves LPG recovery efficiency while managing the pressure energy through controlled phase separation rather than direct compression
3Loss of energy
If sponge oil rate is reduced, then operating cost is reduced, but absorption efficiency decreases
Solution Approach 1:
The patent changes the pressure parameter of the gas stream entering the sponge absorber to elevated levels (50-150 psig). This pressure increase enhances the driving force for mass transfer, allowing reduced sponge oil flow rates to achieve the same absorption efficiency. The higher pressure improves gas-liquid contact efficiency and increases the partial pressure of hydrocarbons, enhancing absorption without proportionally increasing oil consumption
Solution Approach 2:
The patent makes the sponge absorber serve multiple functions simultaneously: it absorbs both hydrogen-bearing gases and LPG from the combined stripper and flash drum overhead streams. This multi-functionality allows the system to achieve dual recovery objectives with a single absorption unit, reducing the total sponge oil requirement compared to separate absorption trains for each gas stream
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 enables higher recovery rates of hydrogen and LPG, with a 27% increase in hydrogen recovery and a 10% weight increase in LPG recovery while reducing the sponge oil requirement, thereby improving refinery profitability.
Implementation Method 1
absorbing C3+ hydrocarbons from the gaseous separated hydroprocessed stream and the stripper gaseous stream together by contact with a sponge oil
Implementation Method 2
Pressure swing absorption (PSA) units are useful for purifying hydrogen by adsorbing larger molecules from the hydrogen stream at high pressure and then releasing the larger molecules at swing to lower pressure
Data Source
AI summary
A process for recovery hydrogen and LPG from a gaseous separated hydroprocessed stream and a stripper gaseous stream and/or a fractionator gaseous stream by increasing the pressure of the stripper gaseous stream and/or the fractionator gaseous stream. Both streams or all three streams can be subjected to sponge absorption and hydrogen recovery in series.