Problem
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.
Action
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.
Solution
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.