(59b) Comprehensive Modelling and Optimisation of Industrial Steam Systems

Energy conservation of site utility system with process integration technologies was initially proposed in early 1980s. Since then, there has been continuous research effort in this area. A series of technical progresses have been produced, including graphical analysis and mathematical programming approaches.  A lot of these approaches aim to reduce the energy cost for existing site utility systems. However, when it comes to the industrial implementation, due to the complex nature of the site utility system, there is a significant gap between the theoretical prediction and site practical. This often results in a less effective engineering implementation results than predicted.

In this paper, a new system mathematical modelling approach is proposed. This new approach has included the detailed hydraulic model for the steam pipeline system. As a result, the utility system can be modelled in a comprehensive manner, by combining together the central heat and power station, the steam distribution pipelines and utility system within individual processes as a complete system.

The comprehensive system modelling approach allows to take into account the practical features in the steam distribution pipelines, such as steam flow direction, mixing junctions, pressure drop, heat loss and condensate, etc. With such model, the steam conditions in various processes can be predicted more accurately.

The operational optimisation for the proposed complete system modelling approach is capable to handle more variables than conventional approaches, such as steam header pressures and some key temperatures. The produced optimal operating scenario can be practical in terms of implementation.

A case study based on a utility system energy conservation project with Sinopec is presented to demonstrate this new approach.