Advanced process control

Abstract

Qatar Petroleum implemented Advanced Process Control (APC) in a plant that designed to process condensate-rich gas to recover liquid products (NGL and condensate) for further processing and export. Process control refers to the techniques to control the variables in a process. As processing plants become more complex in order to increase efficiency, maximize production or reduce costs, advanced process control needs to be applied. This new control system can improve product yield, reduce energy consumption and increase capacity. Moreover, it can improve product quality and consistency, reduce giveaway, and improve the management of transition between plant operating modes. APC is expected to bring many benefits to plant operation. However, the extent of the benefits will be determined by specifics of the plant and how APC is applied. An analysis of the expected benefits is therefore required before a new control system can be implemented. This paper presents how APC was installed using four controllers in specific spots in the plant. It explains how it was installed in parallel with a new Distributed Control System (DCS) to improve control stability of the process, and improve thermodynamic efficiency of the plant by optimizing the pressure profile of the process. The study identifies significant benefits from implementing the APC in the plant, including economic advantages. The APC pushed the plant to optimum operation and this has assisted in the greater recovery of condensate and NGL. Therefore, this paper shows that the objectives of the APC have been met by reaching an increase of 0.99% in production. Also, the control stability of key process variables - manipulated variables (MVs), disturbance variables (DVs) and controlled viable (CVs) - has improved by 10-67%. In addition, the operator interactions with the plant have also been decreased significantly due to the automated DCS. Copyright 2012, Society of Petroleum Engineers.