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Process Overview-Refinery
Petroleum refining processes and operation can be separatedinto five basic areas:
• Fractionation(distillation) is the separation of crude oil in atmospheric and
vacuum distillation towers into groups of hydrocarbon compounds of differing
boiling point ranges called “fractions” or “cuts”
• Conversion Processes change the size and/or structure of hydrocarbon molecules.
These processes include:
- Decomposition(dividing) by thermal and catalytic cracking
- Unification(combining) through alkylation and polymerizationand
-Alteration(rearranging) with isomerization and catalytic reforming
• Treatment Processes to prepare hydrocarbon streams for additional processing
and to prepare finished products. Treatment may include removal or separation
of aromatics and naphthalenes, impurities and undesirable contaminants.
Treatment may involve chemical or physical separation e.. Dissolving, absorption
or precipitation using a variety and combination of processes including desalting,
drying, hydro-desulfurizing, solvent refining, sweating, solvent extraction and
solvent de-waxing.
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Process Overview-Refinery
• Formulating and Blending is the process of mixing and combining
hydrocarbon fractions, additives and other components to produce
finished products with specific performance properties.
• Other refining operations include:
-light-ends recovery
-sour-water stripping
-Solid waste, process-water and wastewater treatment
-Cooling, storage and handling and productmovement
-Hydrogen production
-Acid and tail-as treatment
-And sulfur recovery
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Process Control & Process
• Process control refers to the methods that are used to control
manufacturing a product
• Manufacturers control the production process for threereasons:
-Reduce variability
-Increase efficiency
-Ensure safety
What is ProcessControl?
A process variable, process value or process parameter is the current
status of a process under control. There are four commonly measured
variables which affect chemical and physical process: pressure,
temperature, level and flow.
These process parameters are controlled by controlsystem.
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Control System
What is a Control System?
A control system is a device, or set of devices, that manages, commands,
directs or regulates the behavior of other devices or systems. Industrial
control systems are used in industrial production for controlling
equipment ormachines.
Typical block diagram of control system
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Control System
SCADA
SCADA (or supervisory control and data acquisition)system.
It consists of many remote terminals units for collection of data
(field),that is being connected with master station through any
communication system, having main task of collection of accurate
data and controlling of process for smoothoperation
DCS
It stands for distributed Control System, controlling is performed by
embedded system (Microcontroller based or Microprocessor based
controlling unit for device or instrumentsfrom which data is to be
collect. It provides very intelligent analog control capability. It is very
sensitive for HMI (Human machine Interface) for easy and smooth
control ofprocess
PLC
A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an industrial computer
control system that continuously monitors the state of input devices and
makes decisions based upon a custom program to control the state of
outputdevices.
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DCS & PLC Comparison
Description DCS PLC
Response time A DCS takes much longer toprocess
data, so it’s not the right solution
when response times are critical. In
fact, safety systems require a
separate controller.
PLCs are fast, no doubt about it.
Response times of one-tenth of a
second make the PLC an ideal
controller for near real-time
actions such as a safety
shutdown or firing control
Scalability can handle many thousands of I/O
points and more easily accommodate
new equipment, process
enhancements and data integration
A PLC can only handle a few
thousand I/O points or less.It’s
just not as scalable as a DCS
Frequent process
changes
If your process is complex and
requires frequent adjustments ormust
aggregate and analyze a large
amount of data, a DCS is
typically the better solution. Of course,
the very flexibility of a DCS system
also makes it much more vulnerable
to “meddling” by operators that can
cause spurious shutdowns.
PLCs are best applied to a
dedicated process that doesn’t
change often
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Post Test
Questioner:
Choose the best answer
1. Process control is a method to control process parameter to .
a. Increase efficiency, reduce variability
b. Ensure safety
c. All the above.
2. Pressure, temperature, flow, level are .
a. Process control system
b. Process parameters
3. Which system is preferred for larger IO’s? .
a. DCS
b. PLC
4. Which system is preferred for safety shutdown? .
a. DCS
b. PLC
