2. 22 RESPONSIBLE CANADIAN ENERGY : Progress Report
BONAVISTA/CONOCOPHILLIPS:
ELIMINATING BENZENE EMISSIONS
Two Canadian companies are getting creative in tackling the issue of benzene. They have reduced
their plants’ emissions of the known carcinogen to well below regulatory requirements. “We were
trying to think outside the box,” says Harold Gold, a regulatory and compliance technologist at
Bonavista Energy, whose company has found a way to eliminate more than 99 per cent of the
benzene emissions created during the glycol dehydration process.
In Alberta, the main source of benzene is motor vehicle exhaust, followed by industrial emissions
and other combustion sources. Significant reductions in benzene concentrations have come mainly
as the result of government regulations lowering its concentration in gasoline and improving vehicle
emission performance. But natural gas producers have taken on the challenge of reducing emissions
from their processes, over and above regulatory requirements.
Glycol dehydration is a common, economical method to remove water from natural gas. As glycol
absorbs water in the dehydration process, it also absorbs heavy hydrocarbons, along with some of
the benzene occurring in natural gas. The glycol is re-boiled, which allows it to be recycled through
the system. As the glycol is heated, water and benzene are vaporized and emitted. Benzene emission
reductions can be achieved using various types of condensing tanks, flares or incinerators.
Requirements set by the Energy Resources Conservation Board (ERCB), Alberta’s regulatory body for
energy, place benzene emission limits on industry, which vary depending on when the dehydrator
was built and how close it is to a public facility or permanent resident. Dehydrators installed after
January 1, 2007 have a limit of one tonne per year of benzene emissions.
With the goal of reducing emissions without affecting operating costs, Bonavista Energy retrofitted
one of its dehydrators east of Rocky Mountain House in March 2010. The operation now nearly
eliminates benzene emissions, while also reducing fuel consumption.
Bonavista Energy already had a condensing unit in place to capture vapors created during the
re-boiler stage and condense out the water and hydrocarbon liquids. “We knew we were halfway
there,” Gold says.
The remaining vapors in the condenser tank are now piped back to the re-boiler system for use as
the primary fuel source. Testing has demonstrated more than 99 per cent of the benzene emissions
are used and destroyed in this fuel combustion process.
Bonavista Energy is looking at applying the same technology in its other locations, Gold says.
Bonavista wants to be proactive in its approach to benzene emissions, rather than reacting when
emission levels approach or exceed the regulatory limits.
ConocoPhillips Canada began applying a similar approach in May 2010 with a JATCO BTEX Eliminator
at its site near Three Hills, Alberta. The company also now removes more than 99 per cent of
benzene emissions, without using additional fuel.
Vapors collected from the re-boiler are routed through a shell and tube heat exchanger, where the
glycol flowing toward the re-boiler acts as a coolant. This heat exchanger condenses most of the
benzene and hydrocarbons, which are deposited in a storage tank. Remaining vapours are routed
back to the re-boiler where they serve as fuel when the burner is firing, reducing fuel costs. When
the burner isn’t firing, the vapors are sent to a platinum glow plug, installed in the burner exhaust
stack, which stays hot long enough to combust the benzene emissions.
In addition, the new process decreases the load on the re-boiler because the glycol, arriving rich
with water and hydrocarbons, is 20 to 30 per cent warmer after acting as a coolant within the heat
exchanger. “We are currently evaluating some more potential sites to install the JATCO unit on,”
says Andrea Zabloski, an operations engineer in ConocoPhillips’ energy efficiencies group. “It’s
running well. It’s just a great project.”