Design of Flexible Utility Systems

In order to meet the energy demands from industrial processes, utility plants must convert fuel and water into steam, electricity, and rotational power. Site utility systems are operated with different scenarios or operating conditions, due to variable conditions, such as different electric power tariffs, changing load in processes and variable ambient temperature. A novel methodology for the design and transient analysis of site utility systems has been developed to improve operability and costeffectiveness of utility systems. There exist transient periods in which operating conditions of utility systems are changed from one scenario to another. The system must satisfy steam and power demands that change significantly according to process users’ demands in both steady periods and transient periods. In this study, such transient behaviour is systematically investigated by using dynamic modelling and simulation of site utility systems, which enables flexible utility systems to be designed. Operating policies at steady-state are optimised to maximize the system efficiency or minimise costs, while variation of steam conditions (flowrate, pressure) are kept within acceptable bounds. Transient analysis is performed to check the feasibility of utility system design, analyze the operability and reliability of utility systems, and provide operating strategies in both steady-state operations and transient periods. Better understanding of transient phenomena can lead to cost savings as better use of equipment and/or less using standby capacity. A case study is presented to illustrate significant benefits which can be gained from the modelling framework and transient analysis.