Chemical Engineering March 2017 - 20

Newsfront
Building a Better Burner
Burner manufacturers provide low-NOx equipment that meets both emissions
and performance goals
John Zink Hamworthy
IN BRIEF
BURNER IMPROVEMENTS
TIGHTER CONTROLS
HEAT RECOVERY
EQUIPMENT
S
everal decades ago, regulatory action
that necessitated reductions
in oxides of nitrogen (NOx) from
industrial sources led to the development
of new technologies, such as lowNOx
and ultra-low-NOx burners. In the years
following, burner technologies were studied
and changed until they were eventually able
to achieve startlingly low levels of NOx emissions
as mandated by ever tightening regulations.
However, after actively using this
specialized equipment in chemical and other
processes for extended periods of time,
both end users and burner manufacturers
discovered that achieving these very low
levels of NOx emissions often resulted in a
tradeoff, in the form of reduced efficiency of
the equipment. Now, burner manufacturers
are working to improve the performance of
low-NOx and ultra-low NOx burners.
Burner improvements
" Historically, process burners were supplied
to provide heat to a process, so the requirement
was simply to provide reliable heat and
reliable combustion, " explains Erwin Platvoet,
process burner product director with
John Zink Hamworthy Combustion (Tulsa,
Okla.; www.johnzinkhamworthy.com).
" However, in the early 1990s, emissions of
[NOx] became very important and required a
redesign of their burners in order to generate
less nitrogen oxides. "
Platvoet says the burner industry developed
new fuel- and air-staging principles
and combustion techniques that allowed
burners to generate low NOx and found that
within their own test furnaces, the burners
achieved all emissions and performance
goals. " But by the time these were in the field
for several years, it was noted that a lot of
the designs did not behave as well as older
burners with simpler combustion principles, "
he says. " So for the last several years, the
industry has begun to examine and understand
what happens inside low- and ultralow-NOx
burners. "
Platvoet says that the increasing feasibil20
FIGURE
1. The COOLstar burner applies internal fluegas recirculation
and fuel staging, which results in stable, compact
flames and low NOx emissions
ity of computational fluid dynamics (CFD)
studies has allowed burner manufacturers
to study what is transpiring inside process
heaters when low- and ultra-low-NOx burners
are placed inside. " CFD studies have
revealed that, in many cases, the burners
themselves are not the root cause for the issues,
but more the way they are arranged inside
the firebox, so rather than trying to build
a better mousetrap to provide even lower
NOx levels, burner manufacturers are focusing
on how to improve existing designs.
We have created rules-of-thumb for burner
placement and firebox design that allow us to
get much better behavior out of these burners, "
he says. " This better understanding of
firebox aerodynamics and different arrangements
inside the firebox allows us to not only
lower emissions, but also to improve heatflux
profiles, prevent hot spots and improve
the efficiency of this equipment. "
For example, John Zink Hamworthy Combustion's
COOLstar burner applies internal
fluegas recirculation and fuel staging (Figure
1). This results in stable, compact flames
and guaranteed NOx emissions as low as
15 parts per million by volume, dry (ppmvd)
while minimizing CO emissions during
startup and turndown conditions.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2017
http://www.johnzinkhamworthy.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2017

Table of Contents for the Digital Edition of Chemical Engineering March 2017
