Page 18 - Gi flipbook May 2018

Innovative solutions to complex problems

FIGURE 4: The Immersion Tube Thermosyphon Heater FIGURE 5: Temperature control using a
dual-phase system

HEAT EXCHANGER STEAM PIPE

to more than an hour.
Dual-phase technology, such as the
Immersion Tube Thermosyphon Heater
STEAM BOILER (ITTH) developed by ProHeat Systems
(depicted), relies on energy released
during a change of phase, rather than
The UK has made significant the difference in temperature between

commitments towards greenhouse a warm heating media and a cooler
process gas flow. Thermal lag is greatly
gas reductions, aiming to reduce reduced in the dual-phase system as
steam carries up to 25 times more
carbon emissions by 57 per cent by energy per unit of mass compared to
2030, based on 1990 levels traditional single-phase technology.
This largely resolves the issue of
system inertia by reducing the mass of
heat transfer fluid required, and
infrastructure is currently controlled by accurately using very large datasets of provides the basis for much more
heuristically-tuned PID (proportional, past gas flow fluctuations and, in turn, responsive and adaptive control.
integrating, differentiating) control this information may be used to The UK has made significant
structures. Over the past 70 years, perform smart control of a preheating commitments towards greenhouse gas
these have been commonly adopted unit by firing the heater prior to an reductions, aiming to reduce carbon
for industrial control use for their increase in morning gas flow, for emissions by 57 per cent by 2030,
reliability, simplicity and affordability. instance. The limitations of memory- based on 1990 levels. There are a
However, actuator constraints (and the enabled control are characterised by number of opportunities to improve
inability to have a memory or fluctuations, such as those highlighted indirect heater performance on gas
understand predictable patterns) limit in red, which do not happen on a daily networks. The most promising relates
performance, resulting in frequent basis and thus cannot be predicted. to modernising control systems to
deviations from an ideal process The magnitude of this discrepancy, maximise the effective use of energy
control value. however, is negligible and will not consumed. The adoption of memory-
Machine learning, neural networks cause considerable losses when enabled control has the potential to
and memory enabled control systems handled by traditional methods of optimise set-point performance,
are active fields of research as controlling gas temperatures. eliminate low temperature callouts and
building blocks for artificial Another limitation to accurate reduce carbon emissions associated
intelligence. Their industrial control of conventional indirect with pre-heat by as much as 15 per
application allows preventative heating processes are physical process cent. The introduction of dual-phase
control by mimicking the human constraints. When a temperature thermosyphons offers another example
brain’s reasoning process to recognise sensor identifies a value below a of an innovative solution to a complex
patterns that would be considered chosen operating setpoint, the problem, and represents an exciting
prohibitively subtle to analyse with controller sends a signal informing the opportunity for a new generation of
manpower or previous computational heater to run. However, the mass of fast responding preheat technologies
methods. For process heat, they can heat transfer fluid contained in the that easily adapt to changing heat
significantly improve temperature heater adds substantial inertia, demand whilst maintaining precise
control, as illustrated. lengthening the time for heat to reach temperature control. ■
Although large inter-day and the process gas and ultimately
inter-hour flow changes are displayed, contributing to response lag and ■ ProHeat Systems is a British design
the largest peaks (like those circled in poor control. Additionally, since the and professional engineering
grey, representing morning and heater and controller are separated consultancy specialising in energy
evening gas demand) are expected to by a length of pipe, thermal conservation for critical infrastructure.
occur daily. Their magnitude and transport delays determined by gas For more information,
occurrence can be predicted flows can range from a few minutes visit www.proheatsystems.com

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