Hong Kong's Kai Tak Airport, the world's busiest airport in 1997, became the world's largest remediation site once it was closed. When the airport was decommissioned in 1999 in favor of the new Chek Lap Kok Airport, the government planned to rapidly clean up the site for commercial and residential development. After many years of soil penetration by various fuels and chemicals, the site required an extensive and sophisticated groundwater cleanup. The project consultant needed a treatment system that could destroy at least 95% of the volatile organic compounds (VOCs) and minimize operating cost. The project was highly publicized and generated intense government and public interest; the chosen treatment system had to be proven and reliable.
After thorough technical and supplier evaluation, the consultant selected Global Technologies to provide the VOC treatment solution. Global's extensive engineering support and industry-leading reliability, and its history of solving difficult remediation problems around the world, made Global the obvious choice. Global engineers performed a careful evaluation of the application data and recommended the Model 80 Remedi-CatTM forced draft system. The system processes 8,000 SCFM (12,616 Nm3/min) of VOC-laden air and provides at least 95% destruction efficiency.
Global Technologies' engineering resources and experience processing large airflows and varied organic loadings were crucial to this project. The proven performance of Global treatment systems provided the Kai Tak project engineers the confidence to design an innovative remediation plan. Global's vapor treatment system was designed to be the heart of this cleanup strategy.
To aggressively remove the subsurface contaminants, the engineers blanketed the old airport tarmac with 2,000 soil vapor extraction (SVE) wells and 1,000 sparge wells.
The massive airflow was directed from the wells to a single treatment system. Compared to a modular approach that would require more treatment systems to treat a limited number of wells, this strategy provided significant savings in energy, fuel and personnel. Global was up to the challenge; their experience designing oxidation systems for some of the world's most difficult remediation sites led to an advanced vapor treatment system for Kai Tak.
Global selected a catalyst that utilizes a honeycomb construction to provide superior airflow and low pressure drop. The catalyst selected has undergone extensive technical development and field-testing and was chosen to accommodate the unique airflow volume, the amount and type of VOC, and the desired destruction efficiency of the Kai Tak project.
Another key design feature of Global's vapor treatment system was the inclusion of a variable frequency drive (VFD). The VFD controls the speed of the system fan, regulating airflow through the system and allowing the oxidizer to handle efficiently the air volume fluctuations from the 2,000-plus extraction wells. With a maximum turndown ratio of 10:1, the VFD can produce energy savings far superior to an inlet vane damper. Global provided the VFD with a particulate filter and housed it in a NEMA 4 enclosure to protect it from the sun and other elements.
Like all Global Technologies' systems, the Model 80 Remedi-CatTM was manufactured with the highest quality workmanship and materials of construction. The heat exchanger and reactor were constructed of 304L stainless steel with continuous, leak-tested welding around all seams. To withstand the natural elements, the exterior shell was constructed of aluminized steel with a coat of UV resistant polyurethane paint. High-density mineral wool was placed between the inner and outer shells to maintain external skin temperatures at safe levels.
A final significant consideration was worker and equipment safety, which is a major concern for every Global Technologies system and especially important on a high profile project like Kai Tak. With safety in mind, Global has developed a state-of-the-art Programmable Logic Controller (PLC) which allows safe and intelligent operation with minimum risk. The PLC provides immediate troubleshooting, first-out shutdown detection and operator assistance for start-up. Global's built-in, user-friendly features provide the on-site operators more control, increased up-time, and reduced maintenance costs.
Global Technologies' understanding of a customer's unique needs, coupled with the engineering know-how necessary to fulfill these needs, resulted in another satisfied Global customer. The cost-saving strategy of controlling numerous wells with one treatment system was made possible by Global's ability to accommodate the large and varied airflow from the wells. Global's aggressive and innovative treatment strategies are helping Kai Tak Airport move into a cleaner and safer 21st century.