Problem
Endurance testing of outboard motors for boats has
typically been done in lakes and sometimes on barges. This testing
was time consuming, presented logistic problems and removed the
testing from the R & D department and the factory. When a
company in Oklahoma decided to build their own endurance test cell
area, the Environmental Protection Agency required them to control
the emissions from the test engines. Four test cells were
considered for pollution abatement. The initial design exhaust
volume was in excess of 4,400 SCFM (6,940 Nm3/Hr) per test cell.
This high exhaust volume per cell posed a significant capital and
operating cost problem when the company considered pollution
control equipment.
Action
The customer believed a thermal incinerator would be the
preferred solution because of the low cost of natural gas in
Oklahoma. After looking at equipment capital cost and operating
costs the company recognized the benefit of considering a catalytic
oxidizer. After thorough technical evaluation, Anguil Environmental
Systems, INC. was selected and contracted to solve their VOC
problem and insure that the new test cells were in EPA
compliance.
Solution
Automotive catalysts have proven effective in handling exhaust
gases from internal combustion engines, where both unburned
hydrocarbons and carbon monoxide are destroyed. Anguil analyzed the
operation and concluded that the enclosed engine test cells needed
significantly less exhaust volume than the 4,400 SCFM (6,940
Nm3/Hr) proposed. Anguil determined that the exhaust from even the
largest stern drive engine was under 800 SCFM (1,262 Nm3/Hr) of
air. Exhausting 800 SCFM (1,262 Nm3/Hr) from each test cell would
place each tank under negative pressure, therefore no carbon
monoxide would leak into the test facility. Using 850 SCFM (1,341
Nm3/Hr) as a design criteria, it was determined that a 6,800 SCFM
(10,725 Nm3/Hr) catalytic oxidizer could handle the initial four
test cells with the additional capacity for four future test
cells.
Anguil supplied and installed the catalytic oxidizer inside the
building on a mezzanine adjacent to the test area. Only enough
catalyst to handle the initial loading from four test cells was
supplied which reduced the initial capital cost. An exhaust stack
test analysis was performed to determine what concentration of
carbon monoxide and hydrocarbons could be anticipated. The presence
of carbon monoxide dictated a total enclosure around the catalytic
oxidizer. An exhaust fan was placed in the enclosure creating
negative pressure and eliminating the possibility of carbon
monoxide leaking into the facility. The oxidizer was equipped with
a variable speed/variable frequency drive to provide a high degree
of turndown if only one test cell was being run. A stainless steel
plate and frame type heat exchanger was used to accommodate high
exotherm across the catalyst.
Some of the engines in the facility were diesel engines and some
endurance runs were lengthy. Since these engines potentially could
go out of tune, a ceramic particulate filter was installed within
the catalytic oxidizer down-stream of the gas burner to protect the
catalyst from unburned carbonaceous materials. The periodic cycling
and high fire of the gas burner eventually vaporizes these
carbonaceous materials and allows them to be oxidized by the
catalyst.
After approximately eight months of successful operation, the
company decided to expand and add the four additional test cells.
The new exhaust fans and ductwork were completed by Anguil's
installation crew and additional catalyst was added to meet the
company's increased capacity. The result is a state of the art
engine test facility in compliance with EPA requirements.