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• Endothermic chemical reactor. Catalytic re-
forming process control.
• Furnace. Temperature control (eight coupled
control loops) driving two combustibles (fuel
and gas).
• Distillation column. Two control structures and
study of the economic and control aspects
integration.
• Blending. Process control and mixture pres-
cription specification.
• Automatic valves. Characterization of digital
valve positioners.
• Heat exchangers. Cascade and feedforward
compensators.
• Centrifugal compressors. Anti-surge mecha-
nism.
• Alternative compressors. Two control op-tions,
load steps or split-range control.
• Centrifugal pump. Minimum recycling control
of centrifugal pump.
• ON-OFF level controller. Dead band hysteresis
effect and logic controller.
The “Control techniques” modules are:
• Ratio Control. Two options comparative for
products mixture.
• Cascade control. Level tank control using
cascade controllers. Mainly the tuning and the
switching of the manual and automatic mode of
the nested controllers are outlined.
• Selective control. Two cases, case 1 is a
compression station control and case 2 is a
pumping station control. Particular interest in
the anti reset windup mechanism is shown.
• Feed forward control. Temperature control
comparative in a heat exchanger without
feedforward compensator and with a static or
dynamic one.
• Split range control. This technique is applied to
three systems. A pressure control in a
distillation column head, a pressure control in a
blanketing and a simultaneous flow and
temperature control.
When a module is selected, from one of the main
menus, the corresponding dynamic simulator and its
GUI are started. Later, some details about the
simulation are given. Now, the GUI of each module
will be the focus of attention.
The GUI of the selected module corresponds to a
P&ID (ISA, 1992), Piping and Instrumentation
Diagram. These schematics have passive
components that show information as standing or
running equipment indicators, trend and historical
charts, other types of charts (characteristic valve
curves), value displays,... and active components
that allow acting over the system: starting or
stopping pumps, valves or process units; selecting
automatic/manual/cascade mode in controllers;
modifying the boundary condition and the process
and control parameters,...
By default the simulation runs in real time, but
the user can change the simulation run speed using a
time factor that can be greater than 1 to accelerate it,
if the PC allows it, or lower than 1 to decelerate it
(Figure 2).
3 EXAMPLE
In order to show how works the simulation tool, one
of the simplest modules has been selected (minimum
recycling control of centrifugal pump). First, a
physical system description and the GUI will be
outlined. Second, an experiment is run.
Figure 2: Time factor.
The system (Figure 3) is composed by a tank that
receives a flow of water, a centrifugal pump
connected to the tank outlet, a recirculation valve
(V1) and an outlet valve (V2). The level controller
(LC1) output is connected, in cascade, with the flow
controller (FC2). The FC2 output drives V2. At the
pump outlet, there are two pipes; one is connected to
V2 and the other one to V1. The recirculated flow
(FI4) is governed by the flow controller (FC1) that
drives V1.
The aim of the control structure is ensure that,
regardless of the LC1 actions, the pumped flow
(FC1) must be always greater that a minimum value
in order to avoid both thermal, mechanical or
electrical problems and the pump cavitation. So, the
Set Point (SP) of FC1 is the minimum pumped flow,
which is a manufacturer specification. All
controllers are implemented by PIDs (Proportional,
Integral and Derivative). The process disturbance is
the external flow to the tank (FI3). Besides, there are
two alarm indicators to high and low level in the
tank. The module allows modifying the PIDs
parameters and observing the control structure
performance when the feed flow changes, in
SIMULATORS FOR CONTROL ENGINEERS ADVANCED LEARNING
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