What is a Vapor Recovery Tower? A Practical Oilfield Explanation

If you work around upstream production facilities, you have probably heard about vapor recovery units (VRUs) that capture tank vapors and route them to sales, fuel, or control equipment. A Vapor Recovery Tower (VRT) is a related piece of equipment that helps manage vapors earlier in the process. In plain terms, a VRT is a vertical separation vessel designed to reduce the vapor load that would otherwise reach atmospheric storage tanks, which can improve safety and cut emissions.

This article answers the question, “What is a Vapor Recovery Tower” in a practical way, with the basics of how it works, where it fits in a facility, and what to consider when specifying one.

What is a Vapor Recovery Tower?

A Vaport Recovery Tower, more commonly written as Vapor Recovery Tower (VRT), is a vessel installed in an oil and gas production system to separate and manage flash gas and vapors that evolve when pressure drops on produced liquids. Vapors can be released at multiple points in a facility, especially when liquids move from higher pressure equipment to lower pressure equipment and ultimately to storage tanks.

A VRT is typically placed upstream of the storage tanks so that some portion of the vapors can be removed and routed to a controlled destination before reaching the tanks. That matters because uncontrolled vapor buildup can contribute to venting events, hatches lifting, odors, and emissions.

VRTs are often used alongside vapor recovery systems and VRUs. The U.S. EPA explains that VRUs are commonly used to capture low pressure methane and other hydrocarbon vapors from storage tanks and other vented sources across oil and gas operations. A VRT can reduce how much vapor reaches the tanks in the first place, which can improve the overall effectiveness of a vapor recovery strategy.

Why Vapors Form in Upstream Facilities

To understand a VRT, it helps to understand why vapors appear at all.

Produced fluids come to the surface as a mixture of oil, water, and gas. Even after separation, the “liquid” stream can still contain dissolved light hydrocarbons. When that liquid experiences a pressure drop, some of those light components come out of solution as flash gas. The flash gas can show up when liquids transition between separators, treaters, pipelines, and tanks.

From an emissions standpoint, these vapors can include methane and volatile organic compounds. The EPA has long emphasized that vapor recovery equipment can significantly reduce hydrocarbon vapors that would otherwise be released.

Where a Vapor Recovery Tower Sits in the Process

Facility layouts vary, but a common concept is:

1. Produced fluids enter separation equipment (one stage or multiple stages).

2. Liquids are sent toward stabilization, treating, or storage.

3. As liquids move to lower pressure, vapors are generated.

4. Those vapors would normally travel with the liquid to tanks or appear in tank headspace.

A VRT is installed so that vapor can disengage from the liquid stream in a controlled vessel before that stream reaches the tanks. The separated vapor outlet can then be routed to a destination such as:

• A VRU suction

• A low pressure sales line if suitable

• A fuel gas system

• Another control device depending on site constraints

The exact routing depends on the operator’s design, gas quality, and local requirements.

How a Vapor Recovery Tower Works

At a high level, a VRT works using familiar separation principles:

1) Provide residence time and separation space

A vertical tower provides volume for the incoming two phase flow to slow down. When velocity drops, vapor can rise while liquid falls.

2) Improve liquid carryover control

Many designs incorporate internals that help reduce entrained liquid droplets in the vapor stream. This is important because downstream compressors and control equipment often do not tolerate liquids.

3) Route vapor to a controlled path

Once separated, the vapor outlet is connected to recovery, compression, or control equipment. This is where VRTs and VRUs often complement each other. EPA materials describing vapor recovery configurations show how recovered vapors can be routed for beneficial use rather than vented.

4) Send liquids onward with less vapor evolution

Liquids leaving the VRT continue to storage or the next process step. With less free vapor traveling with the liquid, the storage tanks see lower vapor loading.

Vapor Recovery Tower vs Vapor Recovery Unit

People sometimes mix these up, so here is the practical distinction:

• A Vapor Recovery Unit (VRU) is typically a package that includes a compressor and separation components to capture vapors from tanks or other vented sources and move them to a usable destination. The EPA describes VRUs as commonly used to capture methane emissions from crude oil and condensate storage tanks and other low pressure vented sources.

• A Vapor Recovery Tower (VRT) is typically a vessel used to reduce vapor loading and improve phase separation before vapors reach tanks or before they enter a recovery system. It is often part of a broader vapor management strategy that can include a VRU.

In many facilities, the two work together: the VRT conditions the flow and reduces vapor spikes, while the VRU captures and compresses vapors for routing.

What problems a VRT Helps Solve

When sized and integrated correctly, a VRT can help with several common issues:

Reduced venting and Hatch Events

Lower vapor loading on tanks can reduce the likelihood of pressure buildup that leads to venting through thief hatches or vents, especially during high vapor evolution periods.

Better performance for downstream recovery

If a VRU is installed, a VRT can help stabilize the vapor stream and reduce liquid carryover risk, which can improve reliability.

Emissions reduction support

Operators pursue vapor recovery for both operational and regulatory reasons. EPA guidance on vapor recovery highlights the value of capturing hydrocarbon vapors that would otherwise be released. 

Improved site safety conditions

Reducing uncontrolled vapor release can support safer working conditions around tank batteries and production equipment.

Key Specification Considerations

If you are evaluating “What is a Vapor Recovery Tower” because you need to specify one, here are the main areas to think through.

Tower size and geometry

VRTs are commonly specified by diameter and height. For example, Smith Industries is currently building VRTs ranging from 3′×30′ to 9′×40′. Larger diameters can support higher flow and better separation at lower velocities, while height can provide additional residence time and disengagement space.

Operating pressures and temperatures

Even “low pressure” systems can see meaningful fluctuations. Specify expected ranges, not just normal conditions.

Vapor and liquid rates, including peaks

Designing only for average conditions can lead to carryover, poor separation, or venting during spikes.

Internals and mist elimination

If the downstream destination is sensitive to liquids, specify the carryover requirements and consider demisting approaches accordingly.

Materials and corrosion considerations

Produced fluids can contain water, H2S, CO2, chlorides, and other corrosive components. Material selection should match the service environment and the owner’s corrosion control plan.

Code vs non-code construction

VRTs can be ASME code or non-code, depending on the operating conditions, owner requirements, and how the tower is classified within the facility design. If the tower will be stamped, the documentation and fabrication process will reflect ASME requirements. If it is non-code, owners still often require robust QA/QC practices, traceability, and testing aligned with their internal standards.

How VRTs fit into an Emissions Control Plan

Vapor management is rarely a single piece of equipment. It is usually a system: tanks, vapor piping, control valves, recovery, and sometimes combustion devices where recovery is not feasible. The EPA’s Natural Gas STAR resources emphasize capturing vapors from storage tanks and other vented sources using VRUs, which underscores why upstream vapor handling and proper system integration matter.

A VRT can be one of the tools that reduces the vapor burden and supports the overall objective: fewer uncontrolled releases, more stable operation, and better performance from recovery or control equipment.

Summary

So, what is a Vapor Recovery Tower? It is a separation vessel that helps manage flash gas and vapors before they overload storage tanks. By giving vapors a controlled place to disengage from liquids and routing them to a defined destination, a VRT can improve facility stability, support emissions reduction goals, and work alongside VRUs as part of a complete vapor recovery approach.