PSA Integration with Hydrocracking for Hydrogen Recovery
Solution Overview
Problem
Current hydroprocessing units face inefficiencies in hydrogen recovery and utilization, particularly in complexes lacking a pressure swing adsorption (PSA) unit, which affects the overall economics and requires methods to enhance hydrogen balance and recovery.
Innovation Solution
Operating a PSA unit at higher pressures (500 to 1000 psig) within the make-up gas compression system of a hydrocracker, incorporating a thermal swing adsorption unit to treat external purge gases and using a protective adsorbent layer in the PSA unit to improve hydrogen recovery, and utilizing a membrane unit to separate hydrogen from hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a PSA unit is operated at conventional pressure (300-400 psig), then the equipment count is lower, but hydrogen recovery rate is limited to 85-90%
Solution Approach 1:
The patent applies parameter changes by operating the PSA unit at significantly higher pressure (500-1000 psig) compared to conventional operations (300-400 psig). This pressure increase enhances the driving force for hydrogen separation and recovery, achieving 3-6 percentage point improvement in hydrogen recovery rate while maintaining system reliability through proper equipment design for high-pressure operation.
2Loss of energy
If a PSA unit is operated at higher pressure (500-1000 psig), then hydrogen recovery increases by 3-6 percentage points, but equipment complexity increases due to high-pressure requirements
Solution Approach 1:
The patent merges the PSA unit with the existing make-up gas compression system of the hydrocracker. By integrating the PSA unit into this existing high-pressure system, the patent avoids the need for separate booster compressors and reduces overall equipment complexity despite operating at high pressures. This integration leverages existing infrastructure to minimize additional equipment requirements.
Solution Approach 2:
The PSA unit serves multiple functions: it produces high-purity hydrogen for reactor feed, generates purge gas for the hydrocracking unit, and enables higher recovery rates. This multi-functionality reduces the need for separate equipment and simplifies the overall process configuration despite high-pressure operation.
3Ease of operation
If external purge gas is used without treatment, then the PSA unit can be purged, but water and other impurities may contaminate the adsorbent
Solution Approach 1:
The patent applies preliminary action by treating the external purge gas with a thermal swing adsorption (TSA) unit before it enters the PSA unit. This pre-treatment removes water and other impurities from the purge gas, preventing contamination of the PSA adsorbent and ensuring reliable long-term operation. The TSA unit prepares the purge gas in advance to protect the downstream PSA system.
Solution Approach 2:
The TSA unit acts as an intermediary between the source of external purge gas and the PSA unit. It mediates by removing harmful impurities (water, etc.) from the purge gas before it reaches the PSA adsorbent, protecting the adsorbent performance while still enabling effective purge operation. This intermediary treatment ensures compatibility between the purge gas and the PSA system.
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 increases hydrogen recovery by 3 to 6 percentage points, reduces equipment count by eliminating booster compressors, and generates additional revenue streams from liquefied petroleum gas and light naphtha, thereby improving the overall economics of the hydroprocessing complex.
Implementation Method 1
a pressure swing adsorption unit to separate the compressed gas stream into a hydrogen stream and a fuel gas stream
Implementation Method 2
using a protective adsorbent layer in the pressure swing adsorption unit to adsorb impurities from the external purge gas
Implementation Method 3
treating the external purge gas stream with a thermal swing adsorption unit to remove water and other impurities
Implementation Method 4
treating the external purge gas stream with a thermal swing adsorption unit to remove water and other impurities
Implementation Method 5
The process treated purge gas stream may be sent through a membrane unit to produce a non-permeate stream depleted in hydrogen and a permeate hydrogen stream
Implementation Method 6
compressing the gas stream to a pressure of at least 300 psig to produce a compressed gas stream
Data Source
AI summary
The invention provides a process for producing hydrogen for a hydrogen consuming process comprising obtaining a net gas stream containing hydrogen, compressing the gas stream to a pressure of 20.7 to 68.9 bar (300 to 1000 psig) to produce a compressed gas stream; sending the compressed gas stream to a pressure swing adsorption unit to be separated into a hydrogen stream and a fuel gas stream; purging the pressure swing adsorption unit with an external purge gas stream from a hydroprocessing unit off gas; treating the off gas with a thermal swing adsorption unit to remove water and other impurities prior to purging the pressure swing adsorption unit, and using a protective adsorbent layer in the pressure swing adsorption unit to adsorb impurities from the external purge gas.