What is a vapor combustion unit (VCU) and how does it work?

Vapor combustion systems, or Vapor Combustion Units (VCUs), are essential tools in gasoline, crude oil, ethanol, diesel, and other hydrocarbon and petrochemical applications, designed to safely and efficiently manage volatile gases and vapors.


The Anatomy of a Vapor Combustion System

A vapor combustion system comprises several crucial components that work together seamlessly to ensure the safe disposal of volatile gases, including volatile organic compounds (VOCs). Let’s break down the key elements:


  1. Vapor Collection System: A truck arrives at a loading station, and as the truck is filled with liquid product, the vapors generated in the truck’s vapor space are collected using a vapor collection system. This system involves modifying the truck racks to include safety features and pipes to capture the vapors efficiently.
  2. Pressure Control: Safety is paramount when dealing with volatile gases. To maintain a controlled environment, the system incorporates pressure control mechanisms. An actuated valve opens and closes depending on pressure levels, ensuring that the system remains pressurized. This prevents the release of a constant stream of gas, conserving resources and system integrity.
  3. Flashback Prevention: Safety measures include flashback prevention, which is vital in preventing unexpected flames from traveling back into the system. Vapor combustion systems employ detonation arrestors (DAs) for this purpose. DAs are designed to protect against detonations and flames within the pipeline. They use crimped metal with gaps to minimize flame propagation and break up the vapor cloud into smaller pockets.
  4. Chemical Grouping: Selecting the appropriate detonation arrestor depends on the chemical composition of the vapor. Different chemicals exhibit unique detonation characteristics. Groupings such as Group D, often comprising constituents found in gasoline vapor like butanes and pentanes, are taken into account when selecting arrestors. This ensures that the system is tailored to handle specific chemicals effectively.
  5. Vapor Combustion Stack: After passing through pressure control and the detonation arrestor, the vapor enters the vapor combustion stack, a cylindrical shell where the actual combustion process takes place. The stack is designed to contain the flames, ensuring safety and minimizing environmental impact.


Temperature Control: A Game-Changer

One of the significant advancements in vapor combustion systems is temperature control. This feature ensures that the system operates efficiently and safely while meeting regulatory requirements. Here’s how it works:


  1. Temperature Modulation: Temperature control involves modulating the airflow to the combustion stack. Dampers on the stack regulate the airflow, maintaining the optimal temperature for combustion. This controlled combustion process is crucial for achieving high destruction efficiency, often mandated by environmental regulations.
  2. Supplemental Fuel: In colder climates, the ambient air temperature can affect the system’s performance. To maintain the required temperature, a supplemental fuel, often propane or natural gas, is introduced. This supplemental fuel helps heat the stack to the desired temperature, ensuring that the system operates efficiently even in frigid conditions.


Adapting to Environmental Challenges

Vapor combustion systems are engineered to adapt to various environmental challenges. Cold weather, for instance, can affect the system’s performance, as extremely low temperatures can impact the materials and efficiency of the system. To counteract these challenges, heat tracing, insulation, and other measures are often employed to ensure reliable operation.


Additionally, vapor combustion systems are equipped with safety features that prevent operation if conditions are not suitable. This ensures compliance with regulatory requirements and environmental standards.


Superior Performance, Proven in the Field

Vapor combustion systems are essential tools for industries that handle volatile gases and vapors. Their intricate design and sophisticated components work together to provide safe and efficient disposal of hazardous materials while adhering to environmental regulations.


Our VCUs can achieve VOC destruction efficiencies greater than 99 percent, resulting in hydrocarbon emissions less than 10 milligrams per liter of product transferred. In addition, our VCUs satisfy all the applicable requirements of 40 CFR 60.18.


With vapor control experience dating back several decades, we’ve earned our reputation as a leader in research and development, manufacturing, service and support, and more. In addition to VCUs, we offer vapor recovery units and other vapor control solutions.