Direct answer: Refinery and tank terminal vapor control combines closed vapor collection with either recovery or oxidation. Use a vapor recovery unit when hydrocarbons can be returned as gas or liquid; use a vapor combustion unit, catalytic oxidizer or thermal oxidizer when recovery is impractical. The decision depends on vapor composition, flow, pressure, value, contaminants and operating schedule.
Common refinery and terminal vapor sources
- Fixed-roof and internal-floating-roof storage tanks.
- Truck, rail, ship and barge loading racks.
- Separators, sumps, wastewater and oily-water systems.
- Product blending, sampling and transfer operations.
- Tank breathing, filling and flash vapor.
Each source has a different pressure limit and flow pattern. Combining them without a hydraulic and process review can cause high backpressure, air ingress or liquid carryover.
Recovery or destruction?
| Condition | Preferred evaluation |
|---|---|
| Reusable hydrocarbon vapor and available destination | Vapor recovery unit |
| Loading vapor suitable for adsorption | Activated carbon vapor recovery |
| Heavier hydrocarbons that condense economically | Compression and condensation |
| Low-value or contaminated vapor | Vapor combustion or oxidation |
| Large dilute VOC exhaust | RTO |
| Catalyst-compatible VOC exhaust | Catalytic oxidizer |
Tank vapor recovery system design
Storage tank vapor flow includes filling displacement, breathing and flashing. Estimate minimum, normal, maximum and simultaneous peak flow. The header must remain within the safe pressure range of every connected tank. Read the storage tank vapor recovery design guide.
Loading rack vapor control
Truck and rail loading can create short high-flow vapor events. The system should consider loading rate, number of simultaneous bays, product switching, vapor balance, hose pressure drop and liquid protection. Adsorption, absorption and condensation can recover hydrocarbons, while combustion is an alternative when recovery is unsuitable.
Vapor recovery tower and absorption
A vapor recovery tower uses contact with a liquid absorbent to remove selected hydrocarbon components. Performance depends on gas-liquid equilibrium, temperature, pressure, solvent circulation and mass-transfer contact. The absorbed hydrocarbon must have a suitable downstream destination or regeneration step.
Refinery vapor header design
Segment sources by pressure and compatibility where necessary. Slope piping toward closed drains or knockout vessels. Avoid air ingress through leaking hatches and open drains. Use pressure transmitters, flow measurement, oxygen monitoring and liquid-level shutdowns according to the process risk.
Marine and terminal integration
Ship-loading vapor can create large short-duration flow and strict vessel pressure limits. A terminal system may need to handle storage tanks and marine loading simultaneously. See the marine vapor recovery system guide.
Data required for selection
- Vapor flow for every source and operating combination.
- Full gas composition, molecular weight and heating value.
- Inlet pressure and allowable source pressure range.
- Temperature, humidity and ambient design conditions.
- Hydrogen sulfide, water, oxygen and corrosive compounds.
- Liquid carryover and aerosol.
- Recovered product destination and required outlet pressure.
- Emissions requirement, utilities and area classification.
Frequently asked questions
What is refinery vapor control?
It is the collection and treatment of hydrocarbon vapor from storage, loading and process sources using recovery, combustion or oxidation.
Is a VRU the same as a vapor recovery tower?
No. VRU is a broad equipment term. A vapor recovery tower is typically an absorption contactor and may be one part of a complete VRU system.
Can a VRU handle several products?
Possibly, but vapor compatibility, carbon affinity, solvent selection, condensation behavior and recovered-product routing must be reviewed for every product.
When should an oxidizer be used instead?
Oxidation may be more practical when the vapor has little recovery value, contains difficult contaminants or lacks a safe recovery destination.
Build a complete vapor control plan
Start with how an oil and gas VRU works and the VRU selection guide. Contact PollutionCtrl for refinery and terminal vapor control equipment selection.
