che_october-2023 - 23

Uncovering dust-explosion risks
One of the main hidden hazards in
the CPI is dust, as many people may
not understand the risks of dust explosions.
Crucial to advancing the
dust-control sector is to expand the
industry's understanding of the conditions
that can lead to dust explosivity
- from the size of particles to
the optimal operating conditions and
what type of protection devices might
be required (Figure 1). " MKOPSC
works closely with industry to analyze
data from many different substances
to provide guidance about under
which conditions dust could become
explosive, therefore demanding the
specification of an overpressure-protection
system, " states Khan.
One area where such guidance has
changed drastically in recent years is
in biomass-handling applications for
converting solids, such as sugar or
wood, into biofuels and bio-based
chemicals. " The operating envelopes
have changed significantly with new
applications for biomass. Guidance
can be as simple as changing the
size of particles, or potentially specifying
a device that can relieve excess
energy levels in the system to avoid
explosivity, " he adds. According to
Khan, the biomass-handling industries
have learned a great deal over
time and have built more robust systems
to better avoid explosivity limits
by maintaining certain operating conditions,
while at the same time installing
appropriate protection systems
that will enable them to safely relieve
pressures in case they must operate
outside their normal conditions.
Emerging energy systems
As the world continues to explore
lower-carbon energy options, such
as battery energy storage and hydrogen,
there are many challenges and
process-safety risks that must be
addressed. " In evolving fields, such
as hydrogen and batteries, overpressure
protection is one of the most important
elements, " says Khan.
Hydrogen - with its low ignition
energy, propensity to leak and its
detection difficulties - poses many
unique safety challenges that must
be addressed as larger volumes of
hydrogen enter
the
energy
landscape.
" Hydrogen absolutely works
in a totally different pressure domain
than what we typically expose traditional
protection devices to, so
those systems may not be directly
applicable to the particular environment
where hydrogen operates, "
says Khan. More research will be
required to provide more suitable
overpressure-protection solutions,
which not only must be vetted from
a technical standpoint, but also must
eventually be accepted by the public
as safe. " One thing that is very
clear is that overpressure protection
systems for hydrogen cannot be
open-release, which is very unique
when compared to other hydrocarbons
or fuels, where the protection
system can provide safe relieving
of the pressure to a relatively open
atmosphere. Unfortunately, in the
case of hydrogen, given its low ignition
energy, its release to an open
atmosphere is sufficient to ignite and
create an explosion, " explains Khan.
To address this added complexity,
work is underway to develop unique
pressure-protection systems that direct
the release into a safe, confined
space. Otherwise, says Khan, the
pressure-relieving action itself could
be the source of an accident. " In a
very simplistic system, you might
have a full cylinder of hydrogen being
transported, with an empty cylinder
beside it in the event of a possible
overpressure situation. Then
you could use the second cylinder
as the pressure-relieving system, "
he notes.
Batteries also have special characteristics
that make them prone to
overpressure events related runaway
reactions and overheating (Figure
2). However, as battery systems are
scaling up for utility-scale energy
storage, there is still a need to develop
proper overpressure protection
for individual battery packs. " We are
designing relief and overpressure devices
to be as miniscule as possible
at the pack level. This is a whole new
dimension for overpressure-protection
systems. The industry is working
to design such systems now, not
only to safely run battery systems at
a larger scale, but to also monitor
operation in abnormal conditions to
relieve pressure and avoid major accidents. "
says Khan. Indeed, there
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
OCTOBER 2023
Edison Sripaul, MKOPSC
FIGURE 2. Experimentation using reactor calorimeters
can help shed light on the conditions that
can lead to runaway reactions, such as those seen
sometimes in battery systems
have been significant commercial advancements
in installing relief devices
into individual battery pack systems,
but incidents can still occur at very
large scales. " We have witnessed
quite a few major accidents at those
levels of facilities due to overpressure
and explosions, where a single pack
experiences overpressure and ends
up creating overpressure over the
entire installation. We have a good
understanding at the smaller scale,
but at the utility level, there is still a
knowledge gap, " says Khan.
The next steps
Considering the current state of overpressure
protection, and looking
ahead at the next generation, Khan
sees sensors and process monitoring
as key elements. On the horizon
are devices that not only relieve
or divert pressure buildup, but that
minimize the pressure buildup itself.
" This means that we are monitoring
pressure conditions at the relief device
such that they can operate on a
continuous basis rather than based
on a certain threshold. " This enables
a more circular system where material
can be re-circulated through the
device continuously to avoid pressure
buildup in the system. " This is in stark
contrast to current threshold-based
models, where you allow pressure to
build up within the system and then it
is all released at once, " Khan adds. ■
Mary Page Bailey
23
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che_october-2023

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