Page 31 - Energize February 2021

TECHNICAL

More than 50% of the thermal energy demand in the F&B
industry is at a low temperature level (below 100°C). Heat pumps,
using waste process heat as the heat source, can deliver heat in
this temperature range for use in process heating, and represent a
worthwhile method of improving the energy efficiency of FBI
processes. Heat recovery can effectively be applied to the
production of hot water, which is an essential product in FBI. The
medium and low temperature thermal energy demand offers a high
potential for integrating solar thermal energy in FBI processes.

Health, safety and environmental issues
The FBI offers a harsh environment for electrical equipment. The
environment in an FBI plant is also characterised by extended high
temperatures and heat cycling, all of which affect the lifetime and
Figure 3: Peak shaving (ABB) safe functioning of electrical equipment. Electrical plant needs to
be able to withstand these conditions.
Peak shaving is like load levelling but is aimed at particular
time-based peak demands and has a different charge discharge Corrosion and ingress protection
profile (Figure 3). Energy is stored when the actual demand is Corrosive agents such as acidic food products, moisture and harsh
lower than the scheduled power demand and is used when cleaning chemicals are everyday realities in food and beverage
demand is higher than scheduled demand. processing. Processing leaves food and additive residue on
Peak shaving has an advantage for factories working day shifts equipment, which is removed by a “washdown” process, using high
where the early part of operations will require high demand due to pressure water jets and chemicals at the end of a production run.
motor start-up, thermal system ramp up, compressor pressure This exposes electrical equipment to water, plus whatever gets
build up etc. washed away, and adequate protection of electrical components is
required to ensure continued functioning, and safety of staff
Load shedding working in the plant. This is offset by using corrosion resistant
Emergency load-shedding (LS) systems reduce the total plant load materials such as stainless steel, aluminium, special alloys, high-
automatically to keep key plant processes operating on the tech non-metallics and coated materials.
available capacity in the event of utility or generator loss. LS Motors form an integral part of FBI machinery and are subject
systems constantly observe power system load configurations and to the full effect of washdowns. The industry has produced a range
evaluate which loads could be shed if a source were to be lost. of motors and switchgear devices that are suitable for the harsh
The load-shedding capability balances the power supply and conditions of the FBI. This involves not only internal protection but
draws from on-site power generators when power outages occur. protection of the motor casing as well. Motor casing corrosion and
Individual load shedding can also be used to implement demand chemical accumulation can affect the heat dissipation capabilities
response (DR) systems. of the motor.
Implementation of a load shedding system involves Liquid ingress can deteriorate or short out an electrical system
identification and classification of load points, into interruptible immediately or over time. Exposed metal parts such as cable trays
(UL) and non-interruptible (NUL) loads. This classification can be are susceptible to corrosion and corrosion resistant types such as
affected by the stage at which a process is. Some loads may be stainless steel should be used. Waterproof connectors are an
interrupted if the process can be interrupted but become ULs at a essential item. Most manufacturers make items that are suitable
different stage, and information on the process stage requirements for use in the FBI.
is also necessary.
Power management systems can build a “load shed table” Anti-microbial wiring devices
based on the steady state conditions, the instantaneous electrical Feedstock in the FBI is organic in nature, and despite regular
system topology, and priority table designated by the user. PMS washdowns, organic residue can accumulate on wiring and
also allow configuration of load-shedding priorities based on electrical devices. This can result in the growth of bacteria,
production requirements. The load shedding controller makes moulds, mildew, and fungi, microorganisms which can rapidly
flexible load shedding possible, where the priority of a load can sicken many people.
change depending on the stage of operation. Instead of applying an external disinfectant to subdue bacteria,
antimicrobial wiring has additives that are manufactured directly
Waste heat recovery into the product. The components are gradually released to the
FBIs commonly have a need for heating, refrigeration, HVAC, as surface, providing continuous, long-lasting protection against the
well as air compression. Products subject to heat processes such growth of harmful foodborne illnesses such as E.coli, listeria, and
as baking, cooking UHT treatment, and so on, need to cool down salmonella. Components include cabling, switch, and plug covers,
before packaging, and this offers a further potential for energy and other equipment with exposed surfaces. n
savings. In addition, heat is lost to the environment or is vented
during thermal processes. Refrigeration and HVAC systems References available on request
remove this heat from the plant, and much of this waste heat could
be recovered. Send your comments to rogerl@nowmedia.co.za

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