Download aiche PROCESS CONTROL

PROCESS CONTROL
Welcome to the world of chemical engineering. In this article we will discussing about a very important
branch of chemical engineering called PROCESS CONTROL. The concept of PROCESS CONTROL will be
unraveled and why it matters in Chemical Engineering.
WHAT IS PROCESS CONTROL
The word “control” simply means to manage therefore Process control is basically the science of
managing and optimizing chemical processes. Just like in a band, we have an orchestration of
instruments to produce good music. Process control involves orchestrating a set of elements to maintain
or manage a particular chemical process. Each element has a distinct and important responsibility in the
management and efficient running of the process.
A process is a dynamical system whose behavior changes over time and therefore process control is
needed to handle such changes in order to ensure that processes run efficiently, safely, and predictably.
Process control combines the disciplines of control engineering and chemical engineering – and uses
specialized industrial control systems. These systems control the flow, output, mixture, and other such
aspects of a process, based on feedback from sensors, data monitoring systems and more.
For example, consider what would offer better results when pasteurising milk( a PROCESS in which milk
is treated with mild heat in order to eliminate pathogens and extend shelf life) – an individual taking a
temperature reading manually, then shutting off the heat when the milk reaches the right temperature
OR a sensor in a pasteurization tank that automatically senses when the milk has been pasteurised
properly, and then automatically empties the machine, and moves the product onto the next step. Of
course, the latter would be preferred in controlling the process. This explains the intriguing concept of
process control.
Process control is an important tool that is implemented in several industries like power generation
plants, chemical processing, food and beverage industry, paper manufacturing, and oil refining. Process
control is basically needed anywhere we have a process.
Fig 1: An example of a process control system. This control system is that of a distillation column. It
involves several interconnected components including sensors, temperature indicators, pressure
controllers, flow controllers and many other elements that work together to regulate and manage the
process.
WHY DO WE NEED PROCESS CONTROL?
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Process control reduces safety concerns associated with employees in the workplace:
Process control isn't just a theoretical concept, it's a real-world superhero for chemical
engineers. In industrial processes, there are operating conditions that need to be maintained to
guarantee workplace safety. These operating conditions are crucial variables like flow,
composition temperature and pressure and must be meticulously monitored and controlled.
Note that this isn't just about avoiding explosions or catastrophes (although that's a cool part), it
also involves maintaining efficiency and minimizing waste production in order to ensure
compliance with health, safety and environmental regulations.
•
Process control helps to decrease human intervention and enable automation: Like in the
example of the process of milk pasteurization mentioned above, having a sensor has certainly
taken away the need for an individual to check for temperature manually. While human
intervention and oversight are always going to be necessary, automation allows for elimination
of redundancies and unnecessary manual checks thereby reducing human error and inefficiency.
It also helps to reduce time wastage and maximize the output of the plant.
•
Process control systems operate on a much more refined, powerful level than a system that is
purely controlled by humans and therefore this will help to increase product consistency, safety
and efficiency. For example, let’s say a food processing industry specializes in processed meat.
meat must be cooked to the proper temperature to make sure it’s edible and free of any foodborne contaminants – but it must not be overcooked, or the product may be ruined. A process
control system could be developed to analyse the amount of food products in a particular oven
or the cooking area, and the temperature of the oven – and calculate the optimal time for the
food to remain in the cooking area. Then, the product is placed in the oven, cooked, and
removed automatically. This ensures fast batch processing without human intervention, and
perfectly consistent results every time the system is used.
•
Of course, the purpose of a business is to make profit. Process Control can help companies
lower operational costs (imagine how much you will save replacing a portion of your workforce
with automated machinery), enhance productivity and increase customers satisfaction leading
to higher profits for the company.
COMPONENTS OF PROCESS CONTROL
The fundamental components of a control system can be understood by relating them to parts of
the human body:
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Sensors: These are the eyes and ears of the control system. Just like the eyes and ears act as
sense organs helping us to sense changes in our environment, the sensors of a control system
also help to collect data on process variables such as composition, temperature and pressure.
•
Controllers: Acting as the brain of the control system, controllers use algorithms to process data
and make decisions.
•
Actuators: Just like we use our hands to execute actions, the actuators function as the hands of
the control system executing and implementing the decisions made by controllers.
KEY INDUSTRIES THAT APPLY PROCESS CONTROL
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Pharmaceuticals: In the production of medications, high precision is usually required. The
slightest of errors can render a batch of medication or other such products completely unusable
so pharmaceutical companies try to minimise human intervention and error as much as they
possibly can by making use of advanced process control systems for efficient control of the
manufacturing process, minimizing product waste, and guaranteeing the safety of the
medications manufactured.
•
Manufacturing industries: Manufacturing companies of all types can make use of process
control (manufacturing is a PROCESS and of course, it has to be controlled). A company
manufacturing steel, for example, will likely make use of process controls for tasks such as
ensuring the proper temperature of blast furnaces or for controlling the viscosity of molten
metal, and for other such tasks that help ensure the right overall quality for the products. A
company manufacturing body care products like creams will need precise process control over
ingredient ratios to ensure that the final product meet desired specifications. Automated
systems can also be used to ensure sterility of the production processes.
•
Petrochemicals: In the petrochemical industry, product consistency is very important
particularly when creating products such as rubber and petroleum-derived plastics. Process
control can be used to closely monitor products during the refining and production process,
ensuring consistent quality, and uninterrupted, continuous production of a given petrochemical
product.
•
Food Industries: Process control when used to automate the production of food and dairy
products like milk is a great way to ensure that the food is safe and is of a consistent quality. An
example of automated pasteurization process was given earlier in this article to explain this. The
example involving meat production earlier mentioned also gives the application of process
control in the food industry.
•
Oil and Gas: The oil and gas industry is one of the industries in which process control is heavily
used. Critical variables like pressure, temperature, flow rate and composition must be closely
monitored and controlled and so process control systems are used for these purposes. The oil
companies apply process control to automatically adjust pipelines and product “through-put”
(amount of product that goes through something) keeping the pipeline reliable, safe, and
ensuring a steady flow of oil or gas. Refineries also make use of process controls to ensure
safety, product quality, and uninterrupted production.
•
Power Generation: Power plants do not create a physical product, but rather generate
electricity and power to be used elsewhere – and they must do so constantly, so they always
make use of a number of process control systems.
These systems are used to control power production, ensuring that excess power is not
generated and that the plant does not under-produce power. Important factors such as
temperature of the plant and delivery of the coolant must be monitored and controlled.
CONCLUSION
Chemical engineers are PROCESS engineers and are usually involved in the design of PROCESSES for the
production and manufacture of products. They translate these processes developed in the laboratory
into practical applications for the commercial production of products, and then work to improve and
maintain these processes. The processes developed must certainly be controlled for smooth and
effective running. This explains the importance of process control.
By implementing better process controls, companies of all sizes and industries of all kinds can benefit
from a more efficient production process, better product quality, higher output and many other
advantages.
Also, always keep in mind that process control is the heartbeat of chemical engineering. It's about
innovation, optimization, and making a tangible impact on the world.
Oluwaseyifunmi Adisa
ChE 400lvl