Improving Air Quality by Using Biodiesel in Generators

[Yudhi Aswad]

Improving Air Quality by Using Biodiesel in Generators
EXECUTIVE SUMMARY
A biodiesel / petroleum fuel blend and practical low-cost methods of emission control were
sought to obtain reductions in oxides of nitrogen (NOx) and particulate matter (PM)
emissions from diesel generators. Secondary consideration was given to carbon monoxide
(CO) and hydrocarbon (HC) emissions reductions. The project had three parts: (1) Review
of Existing Technology; (2) Laboratory Evaluation of Biodiesel and Emission Controls, and
(3) Demonstration on a Peak Shaving Generator.
Little direct testing of biodiesel in diesel-powered electric generators (gensets) has been
done. Building on existing research on biodiesel fuels, the University of Minnesota’s
Center for Diesel Research (CDR) evaluated soy-based biodiesel fuels for reducing
exhaust emissions in gensets. After determining the types of engines used for standby
and peak shaving applications in Minnesota, and selecting blend levels and applicable
emission controls for use with those engines, a laboratory evaluation was conducted to
determine the influence of using biodiesel on diesel exhaust emissions from generators.
Neat biodiesel was blended with regular and premium commercial low-sulfur petroleum
diesel fuel. B20 (20% biodiesel / 80% petroleum diesel) was chosen because of
previously successful studies with this blend level, and because there is evidence that the
NOx emissions increase that results from using B20 can be controlled using existing
technology. B85 was selected because: 1) it is a “high blend,” which promised to give a
large decrease in PM at the expense of a larger increase in NOx than B20, and 2) the
Minnesota House of Representatives was considering legislation to provide financial
incentives for new generator facilities using B85. That legislation was not subsequently
adopted.
Two primary NOx control techniques were evaluated during the laboratory tests, chargeair
cooling and a cetane number improving fuel additive. For PM, CO, and HC
reduction, a diesel oxidation catalyst (DOC) was evaluated. A 276 kW Cummins model
ISM was selected to be the laboratory test engine because it is used in some models of
Cummins-powered electric generators and it was available for tests at CDR.
Initially, screening tests using a NOx-reducing fuel additive and biodiesel blends were
conducted to determine if the fuel additive could offset the increase in NOx emissions that
normally occurs using biodiesel. The fuel additive was not effective at reducing NOx in
the biodiesel blends. Full emissions tests of the biodiesel blends with charge-air cooling
demonstrated that significant PM, CO and gaseous HC reductions can be achieved using
B20 or B85 while lowering emissions of NOx. PM emissions were reduced by up to
30 %, while NOx reductions of up to 19 % were observed. The use of a DOC increased
PM emissions using B20, but PM emissions were reduced when the DOC was used with
B85.
Based on the results of the laboratory testing, CDR proceeded to evaluate B20 and the
most practical emission control (charge air-cooling) on a generator at the School of
Environmental Studies in Apple Valley, MN. The demonstration genset engine was a
Caterpillar model 3406 B, turbocharged and jacket-water aftercooled engine. The
generator was rated 400 kW standby and 365 kW prime at 60 Hz, 1800 rpm.
A separate supplemental cooling circuit for the engine intake air was designed and
installed that contained a separate shell & tube heat exchanger cooled with city water.
This cooling circuit enabled a 40 degree C reduction in the temperature of the intake air
charge to the engine to be attained, which closely duplicated laboratory test conditions.
A comparison of NOx, CO, and PM emissions for D2 at 90o C charge-air temperature and
B20 at 50 degrees C charge-air temperature demonstrates the emissions reduction that
may be achieved by switching from D2 with normal charge-air temperature to B20 with
supplemental charge air-cooling. Under this scenario, average NOx emissions are
reduced 15-18 percent. The NOx reductions seen in the field test matched those from the
lab tests very well. PM was reduced 39 to 47 percent. However, the PM reductions seen
during the field tests were significantly higher than those seen in the lab. The dilution
system used during the field sampling may have biased the PM emission results. The
commercial system used for the lab tests is designed to minimize any sampling losses.
The field dilution apparatus may have had sampling line losses due to condensation of
volatile material or thermophoretic deposition of PM. The lab results, where reductions of
up to 18% were measured while using B20, are closer to the expected PM reductions
associated with operating an engine on B20.
The laboratory and field tests demonstrated that a renewable fuel, such as B20, when
combined with supplemental cooling of the intake air, can be used in gensets to achieve
significant reductions in NOx and PM.

Sumber : Submitted by:
Kenneth L. Bickel                      University of Minnesota
Robert W. Waytulonis                Center for Diesel Research
Darrick R. Zarling                      30 June 2004

Semoga aja bermanfaat, sori ya dalam english belum sempat terjemahin 

[Adi Sunardy]

Posting yang menarik bro...

Mungkin bisa lebih menarik kalau sedikit di edit untuk mempermudah pembaca...dari sisi paragraph dan spasinya