In-line pH control and controller performance evaluation

Chemical process control has been dominated by linear control theory and technology over the last few decades. However, the use of linear system techniques is quite limiting, since a significant portion of the chemical processes are inherently nonlinear. Recent advances in computer software and hardware have paved way for the development of advanced nonlinear control methods and algorithms. Though linear systems have the advantage of computational simplicity, in many instances it may not be prudent to use them, especially for severely nonlinear processes. This has led to rapid development of nonlinear control methods during the last ten years.

To some extent, every process is nonlinear. Some nonlinear effects are mild and can be handled fairly well by conventional linear control methods. However, some nonlinearities can be extremely severe and controlling such processes would entail the usage of information inherent in process itself Thus sprang the concept of nonlinear process model based control, which despite its lack of simplicity, is positively seen as emerging technology, offering more efficient control (by having quicker settling times) than the conventional approaches.