pwr_july-2024 - 33

MARNIE SURFACEBLOW
seconds, as Maya swiftly intervened.
" LADIES! Five employees are hospitalized.
They could have died. You are brilliant
engineers beyond comparison-BE ENGINEERS,
NOT SQUABBLING AUNTIES! "
Preternatural silence reigned, then
Marnie broke the ice, " I apologize unreservedly,
Steffi. My sniping about the old
days was unprofessional. Let's get to the
bottom of what happened here, and how
we keep it from ever happening again. "
Steffi relaxed. " Thank you. I pledge my
ultimate cooperation to assist you. And,
thank you, Ms. Sharma. You impress me
yet further, " she said. Marnie gave Maya
a glance that Maya knew said the same.
A Modified Process
" Half a billion tonnes of coal mining
waste lays within 100 kilometers of this
facility, relatively rich in REE/CM. We use
a modular batch process with 12 identical
equipment lines, each capable of
independent operation. " As she spoke,
Steffi marked equipment locations on
a site plan. " Ten lines operate in synchrony,
and two are spares. Ball
tube
pulverizers start at 03:00 and operate
until 07:00, reducing the daily batch of
waste until 100% passes a 0.3 millimeter
screen. At 07:00 the crushed product
is dumped into a tank, then soaks four
hours in sulfuric acid to dissolve some
of the REE/CM. At 11:00 the mixture is
sluiced to liquid-solid separators, and the
tanks cleaned until the next day. "
" Hmm. Normally the soaking takes
days, not hours. What makes your process
so fast? " asked Marnie.
Steffi smiled. " Really, I am shocked the
Great Marnie did not guess already. " Interrupted
by Maya deliberately clearing her
throat, Steffi continued. " Three improvements
were made: the fine mine waste
pulverization, using stronger sulfuric acid,
and heating the tank while soaking. "
" How strong is the sulfuric acid? "
asked Maya.
" From 6 to 7 molarity, depending on REE/
CM content. " Steffi paused, smiling again.
" I eliminated acid storage risk by inventing a
device to make sulfuric acid on-demand by
a modified wet contact method. "
" Really? Most people don't do that
anymore because the reaction heat can
be dangerous, " Marnie commented with
a frown.
" I said modified wet contact method, "
replied Steffi. " We burn sulfur, catalyze
the sulfur dioxide to sulfur trioxide, then
bubble that with hundreds of ultra-fine
nozzles into a labyrinthine water chamber.
Each labyrinth surface is a high-conJuly
2024 | POWER
tact heat exchanger, with heat recovered
for use on-site. After formation of gaseous
sulfuric acid, we condense it to liquid,
removing additional heat, then mix
precisely with water. The system automatically
sets all flowrates, but operators
can over-ride this if needed. "
Marnie nodded understanding. " And
you use the waste heat from this to heat
the soak tank. Is that true? " she asked.
" Precisely! " Steffi replied. " All possible
energy is saved. "
" Ma'am, this process can release sulfur
compounds and hydrogen, the latter
perhaps being the cause of the explosion,
yes? " Maya asked.
" The tanks have hoods and scrubbers,
collecting and neutralizing dangerous
gases. Sulfur and hydrogen detectors are
at every connection. I have worked diligently
to make each segment of the process
safe, reliable, and efficient. " Steffi
paused, then appeared visibly drained.
" I have great shame five workers were
injured. I am sick at heart since the accident.
If I have been the cause, I will face
consequences without evasion. "
Friction in the Workforce
After an uncomfortable silence, Maya
spoke up. " Ma'am, I am tasked with leading
the accident re-enactment. To prepare, I
conducted remote anonymous interviews
with the workers in that process area and
have questions. First, the workers say on
the day of the accident the sulfur soaking
started at 06:10, after a lengthy argument
with the supervisor, when normal operation
begins at 07:00. Why? "
" I must provide some background, "
Steffi replied, looking somewhat downcast.
" There are ongoing personnel problems
here. All supervisors are European,
and all workers are Indian. Many workers
are smart, motivated, responsible, and
would be exceptional supervisors. It is
the home office that does not allow it,
saying they must have a bachelor's degree.
Imbeciles! I believe they simply
feel patronizing toward the workers.
Ironically, almost none of the European
supervisors wishes to be here. They
live in an ex-patriot enclave and refuse
to learn even basic Hindi or Marathi, except
for 'namaste.' There is endemic lack
of empathy for the workers, and I have
terminated several supervisors for disrespectful
attitudes. "
While Maya and Marnie sat stunned at
Steffi's no-nonsense criticism of her own
company. She continued: " To ensure
worker safety, I worked on the facility
lines for a month myself in various roles.
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At each station I witnessed safety concerns,
process inefficiencies, and working
conditions. I was even burned by a
hot pipe that was not shielded. " Steffi
held up her forearm, displaying a small
scar as if it was a badge of honor.
" The coal waste grinding and sulfur
soaking processes are outside the main
building, due to potential liquid or vapor
leaks. Thus, working there exposes one
to the elements. The morning heat can
be terrible, so I said if the forecasted heat
was excessive, we allow advancing startup
by up to three hours, which allows all
workers inside by 09:00, " explained Steffi.
" Very admirable, " Marnie added with
genuine feeling. " From Maya's interviews,
I understand the morning of the
accident, workers were concerned about
the forecasted heat and asked the supervisor
to start sulfur soaking at 05:00 instead
of 07:00. The supervisor refused,
since no one planned by starting the
grinders two hours earlier. Then, the supervisor
agreed to start sulfur soaking at
06:00, but the actual start was at 06:10.
Two questions: wouldn't that mean the
pulverized waste would not have enough
time to dissolve, and why start at 06:10 if
the supervisor agreed to 06:00? "
Steffi thought, frowning deeply. " There
are alternate procedures for soaking after
three hours of grinding, but those require
advance notice. We increase acid
molarity to 8 and apply greater tank heating.
Again, that requires advance notice
and approval from management. As to
the additional 10 minutes, I do not know, "
Steffi acknowledged.
Marnie stood up and said, " I think
it's time to conduct the re-enactment.
There's more here than meets the eye,
and I confess I'm honestly not sure what
went wrong. "
Reconstructing Events
It was late afternoon as the sulfur soak
supervisor and the seven-member work
crew not in the hospital gathered in the
shade of the process control building.
Marnie and Maya had inspected the sulfur
soaking tanks, both noting significant
passive barriers in place that shielded
most of the equipment from the workers.
" That must be why the five were injured,
and not worse, " commented Maya.
They joined Steffi and the work crew,
and Steffi introduced each worker by
name. She then announced, " First, a
prayer for our injured colleagues, " and
recited a Hindu prayer in Marathi.
" Ma'am! " Maya said with surprise.
" Did you memorize that or do you speak
33
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