Cryogenic Air Separation Process
The most common unit for air separation is the cryogenic air separation unit (ASU) which uses cryogenic distillation to produce high-purity nitrogen, oxygen, and often argon. Cryogenic separation gas products are separated from the air first by cooling until they liquefy, and then selectively distilling the components at their boiling points. The cryogenic gas separation process requires tight integration of heat exchangers and gas separation columns to obtain a good efficiency. The cooling of the gases requires a large amount of energy which is delivered by an air compressor. The modern air separation unit (ASU) uses expansion turbines for cooling in order to improve air compressor efficiency.
Non-Cryogenic Air Separation Process
Pressure swing adsorption unit provides separation of oxygen or nitrogen from air without cooling. The air separation process operates around ambient temperature with a high pressure where the air and an adsorbed film of the desired gas is released, using zeolite.
Vacuum swing adsorption for air separation process is a similar process as pressure swing adsorption, but the product gas is evolved from the zeolite at sub-atmospheric pressure.
Membrane air separation technologies operating at ambient or even higher temperatures can provide alternate, lower-energy approaches to air separation process. Membrane air separation technologies are mostly used to provide oxygen poor and nitrogen rich gases.
Some other air separation technologies also exist, but they are still in their early development stages.
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Primary Process Control Improvements for Air Separation Processes
Prior to any advanced process control (APC) project, even in air separation processes, base-level PID tuning and optimization is a critical pre-requisite step. Unless base-level PID control loops are well tuned, advanced process control (APC) cannot work well, since advanced process control (APC) will be manipulating the set points of the base-level PID control loops. Therefore, the first necessary step in the overall process control improvement procedure for air separation processes is PID tuning and optimization of primary or base-level PID controllers. The benefits of PID tuning and optimization in air separation unit is the reduction of the oscillation amplitude or increase of the controller action by a factor of 2 or 3. This allows to enable smoother running of the air separation plant with increased stability in all control loops avoiding unnecessary air separation plant problems such as: damage and/or to fast wear and tear of the equipment, plant irregular shutdowns or off spec product properties and/or grades.
PiControl Solutions LLC has extensive experience in PID tuning and optimization for air separation controllers in the cryogenic air separation industry.
We understand and know how to tackle with typical PID control loop problems and have customized PID tuning and optimization software tools to help optimize all air separation unit controllers.
Our unique and novel closed-loop system identification technology makes it possible to tune and optimize base-level PID control loops quickly, efficiently and precisely. 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 and PID tuning and optimization work can be easily performed remotely by PiControl Solutions LLC process control engineers.
Advanced Process Control (APC) Improvements for Air Separation Processes
PiControl Solutions LLC has extensive experience in advanced process control optimization for air separation processes in the cryogenic air separation industry.
We understand the economics factors that drive the profit margin and have customized multivariable closed-loop system identification and advanced process control (APC) design and optimization tools to help optimize and improve the air separation units.
Because of the relatively small size of many air separation plants, it is more cost-effective to implement DCS-based APC (advanced process control) rather than model predictive control (MPC) techniques. DCS-based APC (advanced process control) approach is fast, cost effective, all inside the existing DCS/PLC, avoiding the complications of OPC/other data communication links from computer to DCS.
Air Separation facilities can have many different process and process control configurations. We focus to analyze the process and provide the right economic advanced control solution for each air separation plant. Our DCS-based APC (advanced process control) methodology has proven particularly successful in this air separation area. Our DCS-based APC (advanced process control) design will result in the following air separation benefits:
- 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.
- Fast throughput modulation to honor real-time electricity power contracts.
- Increase automation and control to allow control room operators to focus and perform on more important and value-added duties.
- Optimize (improve) argon recovery.
Our DCS-based APC (advanced process control) technology works on all types of air separation processes – N2 gas only, N2/O2 gas only, N2/O2 gas /liquid, N2/O2/Argon gas/liquid. For air separation units (ASUs) making gas and liquid, we ensured 4% increase in profits. For smaller plants and plants making gas only, we ensured 1-2% savings in energy due to reduced venting (gas losses). There are other benefits from our DCS-based APC (advanced process control) technology, such as: smoother plant operation, automated loading and unloading and less work for the operators.
Application of PiControl Solutions LLC DCS-based APC (advanced process control) technology to air separation plants will improve plant-wide key performance indicators and accrue the following tangible and monetary benefits:
- Minimize air flow or increase production rate automatically pushing against the active constraint (process, equipment, economic or market), continuously in real-time. The overall DCS-based APC (advanced process control) approach constantly moves the air separation process in the most profitable direction.
- Minimize energy consumption by optimally running the unit at steady state and aggressively rejecting disturbances and running at lowest acceptable pressures.
- Maximize production yield by optimizing nitrogen, oxygen and argon product purities.
- Maintain pipeline pressures.
- Assure minimum liquefier suction pressure.
- Efficiently loading heat exchangers to maintain optimal warm end delta temperature (WEDT) and cold end delta temperature (CEDT).
- Increase overall process automation thus reducing the level of manual intervention needed from control room operators, thereby allowing them focus on more important, potentially money-saving tasks.
- Improve plant-wide process control quality by reducing deviation of product specifications and other critical controlled variables from their desired points.
After all DCS work on advanced process control (APC) schemes is complete and all advanced process control (APC) parameters are calculated and optimized, PiControl Solutions LLC will over factory acceptance test (FAT) make sure that the advanced process control (APC) design is complete, correct and operable. After completion of process control (APC) control project, PiControl Solutions LLC will conduct dedicated process control training for air separation company.
PiControl is an innovative process control software and services company that offers state of-the art, modern solutions at a lower cost, implemented in shorter time compared to competitors.
PiControl Solutions is the only process control and automation company in the world which can perform any advanced process control (APC) project completely remotely. Nowadays, every country uses high speed and reliable internet connection and with a help of medium to high resolution cheap web-cameras or even over widely used remote meeting and screen sharing applications it is possible to do complete design, tuning and optimization, FAT test and start-up of any advanced process control project. Over this low cost online/remote approach huge travel and accommodation costs can be saved and human health and safety can be kept on the high level.
For more information and details, please send us an email: info@PiControlSolutions.com or call the Tel: (832) 495 6436.