APC Application Contributes to Air Liquide’s Operational Excellence Objectives

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An Advanced Process Control (APC) application upgrade was recently completed for Air Liquide in Charleroi (Belgium) on the Air Separation Unit. The APC is providing improved controllability of the plant and is significantly contributing to Air Liquide’s general business objective of enhanced automation and operational excellence.

The project scope included several parts as follows:

  • Migrating an existing APC application from Shell Multivariable Optimizing Controller to Yokogawa’s latest APC technology: Platform for Advanced Control and Estimation which supersedes the previous method
  • Upgrading the APC application with additional variables, an improved control strategy and a new model in line with the current plant operation and objectives
  • Training of Air Liquide staff about the use and maintenance of the APC application

The project was executed over a period of approximately four months as a joint project with Air Liquide. Activities in which Air Liquide staff have been involved include running the plant tests, after Yokogawa had provided the appropriate training, and helping with the fine tuning of the application.

The Air Separation Unit (ASU) produces high purity oxygen, nitrogen and argon; the products are gas and/or liquid. The process design at Charleroi is by Air Liquide. The O2 and N2 gas products are fed to pipelines, several hundred kilometers long, which supply various industrial clients.

The process scope for APC included feed, compressors, cold box, and distillation columns including Argon separation.

APC objectives:

An essential objective of the APC application for the ASU is to help Operations respond fast and smoothly to frequent load changes and product demand changes, while keeping critical product qualities within their desired specifications. The controller drives the main operating handles of the plant such as feed rate and product flows, which would otherwise be adjusted manually by the operator.

Another benefit of the APC application is to provide tighter control of product purities, as measured by on-line analyzers. This enhanced controllability enables optimizing operating conditions in such a way that the recovery of valuable Argon can be improved.

Illustration of the controller performance:

 Histograms of two key controlled variables, the Bubble purity and the Argon product purity, derived from data during 1 month of operation with the APC controller active.

Histograms of two key controlled variables, the Bubble purity and the Argon product purity, derived from data during 1 month of operation with the APC controller active.

What next?  Air Liquide is in the process of conducting a detailed evaluation of the impact of the APC on the plant efficiency and is reporting that they are very satisfied about the performance of the application. Yokogawa has made a proposal about executing a similar APC project on another Air Liquide plant in Europe.  In parallel, work is on-going by Air Liquide US to roll out Platform for Advanced Control and Estimation on the North American ASU plants.

Visit Yokogawa’s website for further information on Platform for Advanced Control and Estimation.