Vapor Recovery Units – VRU

What is a Vapor Recovery Unit or VRU? 

This terminology is used to describe a wide range of systems all designed to accomplish the same goal but for a variety of applications.  They are designed for recovering vapors primarily from liquified gases like propane, butane, ammonia, refrigerant gases like R410a and R32, butadiene, chlorine, sulfur dioxide and even natural gas.

Regardless of the application, these liquefied gas recovery systems all have one thing in common – they require a compressor, suitable for handling the specific gas and operating parameters.

Custom Vapor Recovery Unit

S&S Technical was approached to assist with a custom Vapor Recovery Unit that would be able to evacuate isobutylene vapors mixed with small amounts of hydrogen sulfide from a process reactor, compress them and condense them.  The client had been venting these vapors to flare but due to the addition of the H2S vapors needed to eliminate flaring and recognized the value of being able to reuse the product.

The product was at a very high temperature and would ultimately need to be condensed as part of a closed loop process where zero emissions was the goal.  The gases would be evacuated from the reactor, cooled before entering the compressor, compressed to a higher pressure, and then condensed.

For this application, we chose a Blackmer NGH1023 6” x 3.25” oil-free, two-stage reciprocating compressor.  We had two challenges in the design: (1) Managing the temperature and pressure of the gas as it entered the compressor and passed through the interstage to ensure we did not condense the gas prematurely (2) eliminating the possibility of fugitive emissions.

The triple seal design of the NHG1023 compressor allowed us to use a nitrogen purge system to prevent isobutylene from escaping the compressor through the piston rod seals.  The oil free design also eliminated the need to remove oil from the gas stream which would have contaminated the process.

Temperature Management

For the temperature management, we worked closely with our heat exchanger supplier to design a pre-cooler and interstage cooler that would allow us very tight control of the heat transfer and with our custom logic design, we were able to ensure the gas stream would remain in vapor state throughout the skid.

Once through the final stage of compression, it would enter the custom tube and shell condenser and be recirculated back into the process thus achieving the goal of full recovery and zero emissions.

Vapor Recovery Unit Applications:

• Reduce harmful vapors into the atmosphere;
• Meet EPA emission standards;
• Meet Clean Air Act standards;
• Cut operational costs;
• Reclaim lost profit dollars.

Recovering gas vapors from tank batteries is not a new application for most owners and operators of oil and gas production companies and crude oil storage tank facilities. However, there have been questions as to the economic feasibility for the installation of Vapor Recovery Units (VRUs) on tank batteries.

In recent times, though, regulations required by the Clean Air Act (CAA), and increasing environmental regulations by the EPA are now impacting the requirements to recover these Hazardous Air Pollutants (HAPs). Additionally, through more efficient VRU designs, there can be positive return on investment.

Vapor Recovery Units Provide:

• On-site fuel gas – reducing the need to purchase additional resources;
• Revenue from gas sold to the pipelines;
• Valuable NGLs that can be offered to gas processing plants.

Vapor Recovery Unit Components:

• Industrial Powder Coated Skid Frame;
• Oil-Free Reciprocating Compressor;
• ASME Coded Knock-Out Vessel;
• Class 1, Div. 2 Rated Local Control Panel;
• Pressure & Temperature Switches and/or transmitters;
• Flanged Pipe-Away Safety Relief Valves;
• Welded interconnecting piping with ANSI class flanged process connections.

Advantages of using S&S Technical:

• Full in-house one-stop-shop experience. Our mechanical and electrical engineers use the latest 2 and 3D CAD and SolidWorks software to design every system;
• Integrated Process Automation Controls, PLC’s and HMI’s;
• ASME Pipe fabrication, assembly, and testing are all done at our facility just north of Atlanta, Georgia;
• Turnkey systems provide a single point of contact for your entire project;
• All systems are FAT (Factory Acceptance Tested) in house and will meet all safety, government and industry regulations our clients project may require;
• Single point of contact for technical support, operator training and start up commissioning;
• Complete set of manuals for every piece of equipment and system;
• Reduced installation and start up time – ready to move product shortly after arriving on site;
• Reduced delivery lead times, project costs, improved accuracy.

Give us a call today at (678) 250-9507 for more information on packaged Vapor Recovery Units for your next facility or upcoming project.