Cleaning with liquid nitrogen (LN2 ) is a highly effective solution for the most tenacious deposits that are encountered in petroleum refinery and petrochemical process equipment. Like so many important technologies that have trickled down to find utility in unforeseen industries, liquid nitrogen cleaning technology has too.
The advancement of liquid nitrogen as an effective tool for cleaning didn’t begin at a petrochemical plant or power generation site but was spearheaded by the U.S. government. It began in the 1990s when the United States Department of Energy (DOE) developed the use of high-pressure super-cooled liquid nitrogen as a tool for cleaning components and for cutting into metal storage tanks that contained radioactive material. Liquid nitrogen was an ideal tool for the DOE to utilize for this task because it would not ignite the hazardous contents of the tanks being worked on.
Down the road, in 2003, NASA began to use high-pressure liquid nitrogen to clean the Space Shuttle. Wearing a face mask and protective suit, a NASA technician at Kennedy Space Center aimed a nozzle at the Shuttle’s surface. A controlled stream of liquid nitrogen flowed out of the nozzle and sandstone rubble flew off the surface of the vehicle like powder, leaving the valuable components clean and intact.
Because liquid nitrogen evaporates into the atmosphere after use, cleanup requires only the removal of the post-cleaning dry powder waste. The benefits of using liquid nitrogen for the Department of Energy and NASA were safe and effective cleaning action, no risk of explosion, and no secondary waste stream or cross contamination because liquid nitrogen cleaning does not require the use of water.
There are three basic mechanisms of action that enable super-cooled liquid nitrogen to remove fouling: mechanical pressure, super-cooling, and thermal-volumetric expansion. Using a rotating carrier wand with a multi-port orifice configuration, the Nitrolance quickly and effectively removes the fouling deposits utilizing the three mechanisms:
- Mechanical pressure is the pressure exerted at the nozzle tip of the Nitrolance and is regulated from 5,000 PSI to 55,000 PSI, based on the equipment being cleaned and characteristics of the deposits that are present.
- Super Cooling is the essential feature that enables liquid nitrogen to be highly effective. Nitrolance technology employs liquid nitrogen at temperatures from -160°F to -250°F, and in this range is highly effective in the fracture of semi-porous fouling deposits.
- Thermal/Volumetric Expansion occurs when the high-density LN2 vapor penetrates the cracks and crevices of the fouling deposit, rapidly converting to a gas and expanding to nearly 700 times its volume. This rapid expansion, combined with the mechanical pressure and super cooling, causes the fouling deposit to quickly break apart and release its bond to the parent metal.
The benefits of liquid nitrogen for cleaning are now well established in the petrochemical industry. A good case in point was a 2016 Conco Nitrolance™ application at a plant in Southern Louisiana. The 2,000-acre site north of New Orleans is a vast and bustling petrochemical/manufacturing complex that produces a wide variety of industrial products, from pharmaceuticals to fabric softener.
The heat exchanger tubes in one of the plant’s Butanol Units were coated with a hard varnish-like substance that had built up over time and had become significant enough to impact heat transfer. Plant engineers and maintenance staff had tried hydroblasting, abrasive blasting, and mechanical tube cleaners to remove the fouling, but the hard deposits proved too tough for all of these methods. Abrasive blasting provided some removal of the tube deposits but resulted in tube damage that required the replacement of numerous tubes with each application. In the wake of multiple unsuccessful cleaning applications, the plant understood that the severity of the deposits would require a next-level cleaning solution like liquid nitrogen.
Nitrolance is a leading-edge LN2 cleaning technology and the cleaning system put to good use in Louisiana. To determine if liquid nitrogen would be effective at removing the hard varnish deposits in the Butanol Unit, Conco technicians first removed two of the unit’s tubes and tested the Nitrolance on the hard deposits within at a Conco lab in Deer Park, Texas. The Nitrolance test found the flow of liquid nitrogen turned the hard varnish deposit into a powder, leaving the tube surface like new. These results confirmed the value of the method for the plant, and the successful cleaning of the vertical heat exchangers proceeded. In an effort to prevent the formation of such severe fouling, the plant will clean the Butanol Units every two to three years.
In addition to Butanol Units, the Conco Nitrolance system has effectively cleaned Ljüngstrom™ air heater basket elements, economizer fin tube surfaces, steam coil air preheaters and waste heat recovery boilers in sulfur recovery units.
Contact Conco to find out more about Nitrolance and other advanced cleaning system technologies that can benefit your facility. You can request information or a quotation, and pose your questions to the Ask the Expert portal.
Email: info@concosystems.com; web: www.conco.net; phone: 1-800-345-3476.
