Two-Stage Carbon Adsorption for Hydrocarbon Vapor Recovery
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Solution Overview
Problem
Current hydrocarbon vapor recovery systems are inefficient in capturing light hydrocarbons (C2-C3) and result in environmental and resource wastage, as these vapors are often vented or burned due to the selective adsorption of activated carbon beds, which preferentially adsorb heavier hydrocarbons (C4-C6 and greater).
Innovation Solution
A two-stage carbon bed adsorption system is employed, where the first stage captures heavier hydrocarbons (C4-C6 and greater) and the second stage targets light hydrocarbons (C2-C3), with both stages utilizing vacuum regeneration to convert the captured hydrocarbons into liquid or gaseous fuels for recovery and utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single activated carbon bed is used for vapor recovery, then heavy hydrocarbons (C4-C6 and greater) are effectively adsorbed, but light hydrocarbons (C2-C3) pass through unadsorbed and are vented or burned
Solution Approach 1:
The single carbon bed is divided into two separate carbon beds arranged in series. The first carbon bed is dedicated to adsorbing heavy hydrocarbons (C4-C6 and greater), while the second carbon bed is dedicated to adsorbing light hydrocarbons (C2-C3). This segmentation allows each bed to be optimized for its specific target hydrocarbon range, preventing the light hydrocarbons from passing through unadsorbed as would occur in a single bed system.
2Loss of substance
If light hydrocarbons are vented to atmosphere, then resource is wasted, but environmental pollution increases
Solution Approach 1:
The system converts the harmful act of venting light hydrocarbons to atmosphere into a beneficial resource recovery process. The second carbon bed adsorbs the light hydrocarbons that would otherwise be vented, and during regeneration, these adsorbed light hydrocarbons are desorbed and collected as a combustible gas that can be used as fuel. This transforms the harmful emission into a useful energy resource.
3Loss of substance
If light hydrocarbons are sent to flare for combustion, then resource is wasted, but carbon dioxide emissions occur
Solution Approach 1:
Instead of combusting the light hydrocarbons in a flare which produces CO2 emissions, the system recovers them in adsorbed form on the second carbon bed, then collects and stores them as a combustible gas during regeneration. This allows the light hydrocarbons to be preserved as a fuel resource rather than being destroyed in combustion, thereby eliminating the associated greenhouse gas emissions.
4Loss of substance
If a two-stage carbon bed system is implemented, then both light and heavy hydrocarbons are recovered, but system complexity increases
Solution Approach 1:
The system merges two separate carbon bed adsorption units into a unified vapor recovery process. Both beds operate in series handling the same vapor stream, with the first bed treating heavy hydrocarbons and the second bed treating light hydrocarbons. During regeneration, both beds are processed similarly through vacuum desorption, and the recovered hydrocarbons are combined and used as fuel gas. This merging approach achieves comprehensive recovery while maintaining operational simplicity through standardized regeneration procedures.
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 system effectively recovers and utilizes both light and heavy hydrocarbons, reducing environmental impact and resource wastage by converting vapors into usable fuels, improving the working capacity and efficiency of hydrocarbon recovery.
Implementation Method 1
Activated carbon attracts hydrocarbon material on its surface, with a higher preference for adsorbing the heavy hydrocarbons in the range of C4-C6 and greater
Implementation Method 2
it is then taken off line and regenerated by subjecting it to a vacuum. The hydrocarbons that were adsorbed onto the carbon bed will be drawn off by the vacuum
Implementation Method 3
the vapor will pass through a liquid hydrocarbon shower, such as for example gasoline, where the gaseous hydrocarbons will be absorbed in the liquid hydrocarbons
Data Source
AI summary
A vapor emission control system for recovering hydrocarbon vapors displaced as vessels are loading consisting of two stages of carbon adsorption vapor recovery units. The first stage with two or more parallel carbon beds recovers the heavier C4-C6+ hydrocarbons on a first carbon bed which are then removed as a gas via vacuum and then converted into a liquid product via a vapor-to-liquid conversion unit. Lighter C2-C3 hydrocarbon vapor discharged from the first stage is recovered on two or more parallel carbon beds of the second stage. The vapor is then removed via vacuum as a concentrated gas for use as fuel or sent to a flare. The hydrocarbon lean first portion of the off-gas from each vacuum desorption is recycled to the other in-parallel carbon bed. The load and regeneration cycles alternate for the two carbon beds in each of the two stages based on an optimized time cycle.