Driver Selection, Design and Optimisation
Prof Robin Smith, Dr Jin-Kuk Kim and Mr Simon Perry
Abstract
This project deals with the selection and configuration of drivers to provide mechanical power in the context of the overall total site. Gas turbines steam turbines and electric motors can all be used to drive process machines. The configuration of the overall system needs to account for capital and operating costs, varying demands and cost tariffs, and availability.
Project description
Site utility systems deliver heat and power to a number of processes. The steam system requires a costly water system to provide the feedwater for boilers and heat recovery steam generators. The generated steam is expanded in steam turbines, prior to being passed to the processes to satisfy heating demands. The steam turbines provide power for the site, either in the form of electricity generated, or as direct drives for compressors, fans, and pumps. The drive towards increasing cogeneration has seen the integration of gas turbines and heat recovery steam generators to provide the necessary heat and power. Various tools have been developed for the design, simulation, and optimisation of such systems. However, the tools developed have failed to take account of the configuration of available drivers required to meet the mechanical demands of the total site.
A number of processes, such as LNG, ethylene, and cryogenic air separation, have very high power demands in relation to their heat demands, particularly associated with gas compression. The drivers available to meet the mechanical demands are required to be configured to meet variations in daily and seasonal demands and power tariffs, operability, and maintainability. In some cases the low heat demand of the site processes may not justify the cost of providing an expensive water/steam system. The economies of scale in some plants force the design of the utility system towards the integration of large drivers to meet the mechanical demands, which are often only available in discrete sizes. The high capital cost of the drivers and their discrete size requires the integration of the utility system and the processes to produce optimal designs.
New tools have been developed that account for the configuration of drivers required to meet the mechanical demands of total site systems under various operating scenarios. The tools have been tested on industrial problems, and have produced cost effective designs.