(40c) Improving Operational Flexibility and Efficiency in Industrial Steam Systems

Modern industrial sites are often integrated with multiple processes and plants. Often in such a site, there is one or more centralised heat and power (CHP) stations to produce electricity and steam, which get distributed at various pressure levels of the steam network. Processes and plants take steam from the steam grid, and return excess steam to the grid. Operating the steam system can often be challenging due to the configuration complexity and the constraints on the operations. Constraints on the operation can severely restrict the scope for optimization. In extreme cases, the steam system can suffer from a form of ‘grid-lock’, in which operational flexibility can lead to steam venting. Additionally, there are many practical constraints presented in an integrated industrial site, including flow direction, steam quality assurance at steam pipe end and minimum flow through certain devices. These constraints cause difficulty to adjust operations to optimise for better operational efficiency.

This study uses steam system mathematical modelling and optimisation to improve steam system operational flexibility of the steam system, as well as to reduce energy cost of the steam system. With a site-wide steam network model, it is possible to quantitatively identify operational constraints that inhibit the scope for optimization and in extreme cases the causes of the ‘grid-lock’ problems. The approach can then identify where flexibility can be increased and suggest project ideas to unlock the network. Rigorous equipment models, such as the steam pipeline hydraulic model, have been integrated in the study to identify challenges of key practical constraints. The proposed operation strategies to reduce energy cost have also been verified with such detailed equipment models.

A case study based on a total site energy study with a large-scale industrial site in Western Europe is presented. Two aspects have been covered in this case study, one is to operationally optimise steam system operation cost, and the other is to tackle certain ‘grid-lock’ issues in the steam network. Practical aspects such as condensate prevention, handling dynamic demand swing in steam headers, throughput flowrate limits of steam pipelines and assuring steam temperature and pressure for end process users etc. are considered in the study. Thus, a series of operational optimisation strategies and retrofit project ideas to improve steam configuration flexibility are proposed.