Modeling the energy consumption of chemical batch plants using a combined top-down/bottom-up approach

Abstract

A top-down approach was used to investigate, whether or not it is possible to correlate the overall energy/utility consumption with the total amount of chemicals produced in a chemical batch plant. This approach was suitable for monoproduct batch plants but not for multiproduct and for multipurpose batch plants that produce a large variety of different products. For one of these latter plants, detailed measurements of steam, brine and electricity consumption on apparatus level (bottom-up approach) were undertaken and corresponding models for single unit operations were built. These models describe the most important physico-chemical phenomena of the different unit operations but also comprise empirical terms accounting for apparatus-specific energy losses. This leads to a bottom-up model of a multipurpose plant which was tested for different periods. The model results showed good agreement with the measurements and demonstrated the applicability of the postulated approach. It was therefore possible to analyze the consumption of the different energy carriers in more detail on the basis of the bottom-up modeling results. The obtained models can be used to forecast energy requirements and to allocate energy costs to different products in multipurpose/multiproduct chemical batch plants. Furthermore, they can be used for optimization purposes and for the design of new, energy efficient chemical batch processes.