A cutaway view of the Continental Controls Corp. EGC 4 electronic carburetor that is a key component of the new sensing and control system.
were central to the California Energy
Commission’s strategy of using CHP
as a way to reduce fuel consumption
and greenhouse gas emissions while
improving grid resiliency. In November
2007, therefore, SoCal Gas requested
a grant from PIER to develop the control technologies needed.
As SoCal Gas noted in its proposal
to PIER, “engine emissions control
technology is lagging the regulatory
requirement for criteria pollutants,” yet
because the regulation applied only to
the California market, there were no
cost-effective technologies for manu-
facturers to design systems that meet
the requirements. “Engine manufac-
turers are key to widespread mar-
ket acceptance of CHP,” the proposal
said, “but they have been unable or
unwilling to provide a factory solution
to California’s emissions requirements
or to integrate thermal systems into
their CHP packages.”
To address this market shortfall,
SoCal Gas proposed that it split the
cost of developing the new technology
with PIER, covering 52% of the total
funding. The aim of the two-year project
was to develop and demonstrate ultra-
low emissions technology and an up-fit
conversion kit for rich-burn gaseous-
fueled engines. The conversion kits
would be for engines in the 268 to 1070
hp range with a cost of $15,000 to
$40,000, depending on the size of the
engine. Upon completion of the dem-
onstration, the technology would be
prepared for commercial application for
both retrofit of engines and packaging in
new engines.
EMISSIONS TECHNOLOGY
Sensors placed after the catalyst
report whether the emissions comply
with the appropriate standards, but
there is no way to determine whether
a noncompliant condition is caused by
the AFR control malfunctioning by a
mechanical or electrical problem with
the engine (such as misfire or detonation) or a problem with the catalyst.
The testing was intended to establish a control system that would continue to meet the CARB emissions
limits over the long term or at a minimum be able to meet and maintain
the slightly higher distributed generation limits. After repeated tests, CCC
employed dithering of the electronic
gas carburetors to finally bring the
emissions levels into compliance with
the R1110.2 DG standards.
To provide real-world experience,
SoCal Gas identified a customer,
Fontana Wholesale Lumber (FWL),
as its test site. FWL treats wood with
heat or chemicals to make it resistant
to fire, insects and fungus. The company uses a 12-cylinder Waukesha
L3711 natural gas engine that drives
a 400 k W generator to provide power
for the facility. The exhaust heat is
recovered and used to dry the treated
lumber or provide heat for the boiler.
For the test, CCC finished the
design of a new larger electronic carburetor — the EGC 4, which along with
a new DCL catalyst was installed on
the engine. The exhaust and catalyst
were insulated to retain as much heat
as possible, both to improve the performance of the catalyst and to maximize the amount of heat available for
the cogen application. A data acquisition system was set up that monitored
temperatures and pressures as well
as NOx and CO emissions from more
than 25 sensors and other inputs on
and around the engine. The data was
available for monitoring in real time
and stored for later analysis.
The system operated properly, but
there were occasional CO excursions
that couldn’t be linked to changes in the
load or AFR control. As dithering was
integrated into the control scheme, the
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