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In air separation industry atmospheric air is separated into its primary components such as: nitrogen and oxygen, and sometimes also argon and other rare inert gases.

The most common unit for cryogenic air separation is the cryogenic air separation unit (ASU), which employs cryogenic distillation to produce high-purity nitrogen, oxygen, and often argon. In this process, cryogenic separation of gas products is achieved by first cooling the air until it liquefies, followed by selective distillation of the components at their respective boiling points. The cryogenic gas separation process requires tight integration of heat exchangers and gas separation columns to achieve high efficiency. The cooling of the gases demands a substantial amount of energy, typically supplied by an air compressor. Modern air separation units (ASUs) enhance efficiency by using expansion turbines for cooling, thereby improving the performance of the air compressor.

Pressure swing adsorption units provide separation of oxygen or nitrogen from air without cooling. This air separation process operates at ambient temperature and high pressure, where air and an adsorbed film of the desired gas are released using zeolite.

Vacuum swing adsorption for air separation is a similar process to pressure swing adsorption, but the product gas is evolved from the zeolite at sub-atmospheric pressure.

Membrane air separation technologies operate at ambient or higher temperatures and offer lower-energy alternatives for the air separation process. These technologies are primarily used to produce oxygen-poor and nitrogen-rich gases.

Several other air separation technologies are in existence, though they are still in the early stages of development.

The benefits of PID tuning and optimization in an air separation unit include the reduction of oscillation amplitude and an increase in controller action by a factor of 2 or 3. This enables smoother operation of the air separation plant with increased stability in all control loops, avoiding unnecessary air separation plant problems such as equipment damage, rapid wear and tear, irregular shutdowns, or off-spec product properties and grades.

PiControl Solutions LLC has extensive experience in PID tuning and optimization of air separation controllers in the cryogenic air separation industry. We understand and can address typical PID control loop problems, and we offer customized PID tuning and optimization software tools for all air separation unit controllers.

Our unique and novel closed-loop system identification technology allows quick, efficient, and precise tuning and optimization of base-level PID control loops. With our closed-loop technology, we can perform system identification and PID tuning optimization of the following critical base-level PID controllers easily.

Moreover, all process and data analysis, as well as PID tuning and optimization work, can be easily performed remotely by PiControl Solutions LLC process control engineers.

• Improve air separation process operating efficiencies.
• Maximize production during high demand.
• Minimize product venting (gas losses) based on gas product line demand and liquid inventories.
• Enable fast throughput modulation to honor real-time electricity power contracts.
• Increase automation and control to allow control room operators to focus on more important and value-added duties.
• Optimize (improve) argon recovery.

Our modular PLC-based MPC technology is effective for all types of air separation processes—N2 gas only, N2/O2 gas only, N2/O2 gas/liquid, and N2/O2/Argon gas/liquid. For air separation units (ASUs) producing both gas and liquid, we have ensured a 4% increase in profits. For smaller plants and those producing gas only, we have ensured 1-2% savings in energy due to reduced venting (gas losses). Additional benefits of our modular PLC-based MPC  technology include smoother plant operation, automated loading and unloading, and less work for operators.

Application of PiControl Solutions LLC modular PLC-based MPC Technology to Air Separation Plants.

• Minimize air flow or increase production rate by automatically pushing against the active constraint (process, equipment, economic, or market) continuously in real-time. The overall modular PLC-based MPC approach consistently moves the air separation process in the most profitable direction.
• Minimize energy consumption by optimally running the unit at steady state, aggressively rejecting
  disturbances, and maintaining the lowest acceptable pressures.
• Maximize production yield by optimizing nitrogen, oxygen, and argon product purities.
• Maintain pipeline pressures.
• Ensure minimum liquefier suction pressure.
• Efficiently load heat exchangers to maintain optimal warm end delta temperature (WEDT) and cold end delta temperature (CEDT).
• Increase overall process automation, reducing the need for manual intervention from control room operators, allowing them to focus on more important, potentially money-saving tasks.
• Improve plant-wide process control quality by reducing deviations in product specifications and other critical controlled variables from their desired points.

After all advanced process control (APC) schemes are complete and all advanced process control (APC) parameters are calculated and optimized, PiControl Solutions LLC will conduct a factory acceptance test (FAT) to ensure that the advanced process control (APC) design is complete, correct, and operable. Upon completion of the process control (APC) project, PiControl Solutions LLC will provide dedicated process control training for the air separation company

PiControl is an innovative process control software and services company offering state-of-the-art, modern solutions at a lower cost and with shorter implementation times compared to competitors.

PiControl Solutions is the only process control and automation company worldwide capable of performing any advanced process control (APC) project completely remotely. With the widespread availability of high-speed and reliable internet connections, along with affordable medium to high-resolution webcams or widely used remote meeting and screen-sharing applications, it is possible to design, tune, optimize, FAT test, and start up any advanced process control project entirely online. This low-cost online/remote approach saves significant travel and accommodation costs while maintaining high levels of human health and safety.

For more information and details, please email us at [email protected]  or call Tel: (832) 495 6436.