pwr_january-2025 - 28

MARNIE SURFACEBLOW
Hector called from the tent door and
invited everyone inside. Electric space
heaters gave welcome relief from the
cold. Both steam-driven compressors
were completely disassembled and
cleaned, only waiting on inspection for
re-assembly.
When asked about the compressors,
Hector was happy to tell their story. " We
use multi-stage compressors to boost
the syngas pressure to 200 bar [2,900
psi]-assuming everything's working.
Typically, we manage 160 to 175 bar, and
at 150 bar or lower pressure, we come
offline for servicing. We have two small
electric compressors for startup, but
they're not rated for continuous use. "
Looking over the compressor parts,
Maya noticed something unusual. " Sir,
looking at these bearing journals, I see
scalloping and burnt lubricant. Did the
system lose oil pressure? " she asked.
Hector shrugged. " No, and we use
good quality oil. For some reason, it goes
bad very early. Once we changed the oil
each year, now it's every three months,
and we still have problems, " he said.
Marnie looked around the compressor
area, then Maya noted Marnie doing a
classic double take upon reading the labels
on the lube oil drums. Turning to the
group, Marnie announced, " OK! I have
ideas to share. Inside, to coffee, warmth,
and more coffee! "
Scientific and Practical Solutions
After everyone returned to the meeting
room and had replaced a large percentage
of their blood with hot coffee, Marnie
commenced the great reveal. " You're
fortunate that you increased the maintenance
budget and preventive maintenance
at the plant, Wayne, otherwise
this would be a basket case, " she began.
" Let's start with the primary reformer.
Maya, your thoughts? "
" I propose as other plant systems
suffered more frequent outages, the primary
reformer underwent many more
startup cycles. Already much past its
operating life, rapid heating cycles led to
accelerated failure in parts already suffering
from creep stress. " Maya paused,
reading Marnie's expression. " But I see
there is something I missed, yes? "
" Yes. Consider the location of the temperature
spikes. If the natural gas burners
were impinging on the tubes, the failures
would occur near the burners. But instead,
they form on the opposite side of
the reformer, where the syngas has the
highest hydrogen content. What if hydrogen
embrittlement leads to pinhole tube
28
leaks, where a jet of hydrogen and carbon
monoxide ignites and overheat the nearby
catalyst tubes? " Marnie suggested.
" Wow, " said Wayne, who in one word
captured the reaction of the room. " How
do we fix that problem? "
" It's easy, but expensive. Your best
bet at this point is a complete re-tubing,
because any bad tubes that remain can
damage the new tubes, " she replied.
Stunned silence reigned, and Marnie,
fully in character as the engineering detective,
said, " Now, Maya will discuss
the problems of das Methanator. Maya? "
Crossing her arms and giving Marnie a
stern glare, Maya replied, " Yes, ma'am,
but not with that outrageous accent. We
know the methanator catalyst can suffer
runaway overheating if too much CO
enters the system. Some posited the
water shift systems were defective. I performed
a data analysis on the CO probe
readings and find with 99% confidence
the CO probes produce random results
within their span. The water shift systems
are, unfortunately, trying to control
their operations to those values, leading
to poor efficiency. The solution? Replace
the CO probes, " submitted Maya.
" Great
job, Maya! "
congratulated
Marnie. " Now, as to the compressors, I
think there are a couple of components.
First, I think changing the type of oil will
do the trick. You're currently using polyalkylene
glycol-PAG-oil, and it's good
for ammonia refrigeration compressors
because it mixes with ammonia, and
even though it's hydrophilic, it tolerates
some water without compromising lubrication.
But with your condenser underperforming
and allowing greater water
in your syngas, the PAG is drawing more
water into the system, leading to loss of
lubrication. I recommend switching to an
oil that doesn't mix with water, and installing
an oil drying system, fixing your
condenser, or both. "
Wayne and his team started peppering
Marnie and Maya with questions about
the path forward, when Marnie dramatically
held a finger to her lips to quiet the
room. " Some of you may have thought
I forgot about the primary reformer's exhaust
gas cooler, and how to bring it back
into service. Well, come outside, and
watch some magic! " she encouraged.
About 15 minutes later, Marnie had
assembled the group in front of the disabled
exhaust gas cooler. A laptop was
set up on a tripod, as well as a thermal
imaging camera that was also attached
to the laptop for screen mirroring.
Marnie addressed the team again, while
www.powermag.com
2. A thermal camera provided the insight
needed to find shallow underground piping.
Source: POWER
in the background two plant staff ran water
hoses out to the exhaust gas cooler header.
" This idea came to me after my aunt
passed away last year. As executrix, I had
to sell her house, but before I could sell her
house, the county required a map showing
the septic tank and its main lateral lines.
Unfortunately, no such map existed, and I
didn't want to destroy her backyard looking
for the lines. I knew the lines weren't
buried very deep, so I waited for a really
cold morning, ran hot water continuously
down the sinks, and used my thermal imaging
camera to see the heat flowing to
the septic tank, and then slowly out to the
laterals, which was enough information to
satisfy the county, " she explained.
Turning to the plant staff, who had finished
hooking up the water lines, Marnie
gave them a thumbs-up signal. " Luckily,
we don't have to wait for a cold day here.
Wayne, I hope you don't mind my borrowing
two of your maintenance crew. They
just attached hot water lines to the exhaust
cooler header, and in about 10 minutes, we
should see some magic, " she said.
The group waited patiently, conversing
quietly, until after just five minutes,
Marnie squealed with joy as her laptop
screen showed yellow, then orange
traces of heat slowly moving along the
ground, outlining the underground piping.
Guided by the camera, the two maintenance
crew members began placing
stakes in the ground to note the water
line locations (Figure 2). Wayne turned to
Marnie, and with obvious respect showing,
shook her hand.
" OK, you win, " he said. " Science isn't
boring. "
" It never is, " replied Maya and Marnie
in unison.■
-Una Nowling, PE is an adjunct professor
of mechanical engineering at the
University of Missouri-Kansas City.
POWER | January 2025
http://www.powermag.com
pwr_january-2025

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