Reducing Emissions and Capturing Value: How Activated Carbon-Based VRUs Work
Introduction
Vapor Recovery Units (VRUs) are among the most effective technologies for capturing hydrocarbon vapors generated during routine petroleum (crude oil, gasoline) product loading facilities and retail gasoline stations. Beyond controlling emissions, these systems transform what would be waste into a valuable recoverable and saleable product. This supports both environmental compliance and operational efficiency.
Activated carbon-based VRUs are especially well-suited for petroleum loading terminals and retail gasoline station applications. Their modular design and high capture efficiency make them the preferred choice where VOC control is needed.
These systems often employ dry vacuum pump technology due to its proven reliability and ability to minimize contamination of recovered vapors, ensuring cleaner product recovery and lower maintenance.
Activated carbon used in VRUs typically comes in pellet or granular form, with variations such as high-activity carbon for light hydrocarbons, impregnated carbon for targeted contaminants like sulfur compounds, and acid-washed grades for enhanced purity and performance in sensitive applications.
How Cimarron VRUs Work
Activated carbon VRUs operate on a cyclic basis involving adsorption, regeneration, and recovery:
1. Adsorption
For terminal loading as well as retail gasoline station tank truck unloading applications, an activated-carbon based VRU is preferred due to its high efficiency, reliability, and low maintenance. Terminal types include bulk storage facilities including standalone sites and those integrated with refineries, along with railcar and marine loading terminals.
In these systems, vapor-laden gas streams are directed into fixed vessels known as adsorption beds that are packed with activated carbon media. These beds are designed to maximize surface area and contact time with the vapor stream. The porous microstructure of the carbon adsorbs VOC molecules efficiently. Cimarron systems typically use a dual or multi-bed setup where one bed remains in active service while the other undergoes regeneration. This configuration supports continuous vapor recovery and maintains high operational uptime.
2. Regeneration of Activated Carbon
When a carbon bed becomes saturated with adsorbed VOCs and can no longer effectively remove vapors from the incoming gas stream, it is considered to have reached its adsorption capacity. To restore its effectiveness, the bed must undergo regeneration, also referred to as the desorption phase. During this phase, the saturated bed is isolated and purged of adsorbed compounds while vapor recovery continues using an alternate, regenerated carbon bed. This ensures continuous system operation.
Regeneration ‘cleans’ the carbon by driving off the trapped VOC molecules from the porous surface of the activated carbon. This is achieved by either reducing pressure or applying heat to disrupt the physical bonds holding the VOCs to the carbon.
Regeneration methods typically dry vacuum pumps, which apply a vacuum to the saturated carbon bed, reduce internal pressure below the vapor pressure of the adsorbed VOCs. This pressure differential causes the VOCs to desorb from the activated carbon and flow to a recovery system.
Cimarron uses dry vacuum pumps—primarily from HORI or Busch—because they offer high reliability and significantly reduce the risk of contaminating recovered vapors with lubricants or process fluids.
3. Emission Reduction/Product Recovery
Once VOCs are desorbed from the activated carbon during regeneration, they are routed to a vapor recovery system where they are cooled and condensed into liquid hydrocarbons. These recovered vapors are collected in storage tanks for reuse on site, resale as product, or other beneficial use. This process transforms what would be regulated emissions into a revenue-generating resource.
Carbon-based VRUs are highly effective at removing VOCs from vapor streams.
Systems are capable of achieving:
- VOC control efficiencies exceeding 99.9 percent
- Vent gas concentrations as low as 0.15 mg/L or 150 mg/Nm³, aligning with or surpassing applicable air quality permit limits
Unlike combustion-based control technologies, these VRU systems do not generate secondary emissions such as NOx, CO, CO2, or SO2.
4. System Engineering and Operational Features
Cimarron VRUs are designed with features that reflect decades of field feedback and engineering evolution:
– Cloud-based data management
– Dry vacuum pump technology for durability and purity
– Complete Human-Machine Interface (HMI) and PLC control
– Continuous Emission Monitoring (CEM) compatibility
– Real-time monitoring with dedicated field service support
– Custom reports and trending tools
– Design life exceeding 20 years
– Return on investment (ROI) within 12–24 months, depending on throughput
5. System Types and Application Specific Designs
Cimarron offers carbon bed VRUs tailored to diverse environments:
– Marine Terminal VRUs
– Rail and Truck Loading VRUs
– Retail Gasoline Station VRUs
– Oxygen Removal VRUs
– Custom-Engineered Systems
6. Applications and Compliance
Cimarron carbon-based VRUs serve:
– Bulk Loading Terminals
– Retail Refueling Stations
– Marine and Rail Loading Operations
– Crude and Refined Product Storage
– Mobile Vapor Recovery Needs
– Tank Venting
These carbon-based VRUs are engineered to comply with stringent EPA air quality regulations, including NSPS and NESHAP requirements under 40 CFR Parts 60 and 63. They enable facilities to meet regulatory standards while recovering valuable hydrocarbon vapors that would otherwise be emitted as losses.
7. Summary
Carbon-based Vapor Recovery Units (VRUs) are a highly effective solution for controlling volatile organic compound (VOC) emissions in petroleum loading, storage, and fueling operations. These systems use activated carbon to adsorb hydrocarbon vapors and incorporate vacuum or thermal regeneration to recover valuable product for resale or reuse. Their modular design and high efficiency, along with clean operation that avoids combustion byproducts, make them well suited for bulk terminals, marine and rail loading, and retail fueling applications. With performance levels exceeding 99.9 percent VOC removal and integration with digital monitoring and control systems, carbon based VRUs support both environmental compliance and economic value recovery across a wide range of operating environments.
8. Conclusions
Cimarron’s carbon-based VRUs are engineered to provide reliable control of VOC emissions while enabling hydrocarbon vapor recovery for operational reuse or resale. These systems are based on proven adsorption and regeneration principles and are supported by field-tested components including dry vacuum technology, HMI and PLC control systems, and integrated monitoring tools. Designed for continuous operation in demanding loading and storage environments, carbon-based VRUs meet applicable regulatory requirements and contribute to measurable reductions in emissions and product loss.
About Cimarron
With decades of experience and a legacy of innovation, Cimarron delivers advanced emissions management solutions for the global energy industry. Our technology-driven products and real-time monitoring systems help customers reduce emissions, optimize operations, and ensure regulatory compliance. We serve key sectors, including oil & gas production, energy storage & distribution, renewables & biogas, coal mine methane, and industrial applications. Our expertise spans tens of thousands of successful equipment installations worldwide.
Headquartered in Houston, Texas, Cimarron operates across more than 45 countries with 550+ employees and global engineering, manufacturing, and service locations in the U.S., Italy, India, England, and the UAE.
For more information, visit www.cimarron.com or contact us at sales@cimarron.com.