Estimation and Analysis of Energy Utilities Consumption in Batch Chemical Industry through Thermal Losses Modeling

Abstract

A systematic approach for the estimation of energy utility consumption in chemical batch plants is presented and validated. This approach is based on bottom-up modeling of energy use and its conversion in usual energy carriers like steam, cooling water and brine, including estimation of thermal losses. The modeling involves a detailed energy balance of each unit operation using dynamic plant data. Thermal losses are determined using an empirical parametric equation for each equipment and utility. The method was applied to one monoproduct and one multiproduct building of a chemical batch plant comprising 20 main equipments (reactor vessels, heat exchangers and dryers) for the production of 5 specialty chemicals and intermediates over a period of 2 months. For fitting the parameters of the empirical thermal losses models it was crucial to determine the real energy consumption for the investigated equipments. In the lack of installed flowmeters it was tested whether this task can be performed through calibration of the valves controlling the utility distribution based on valve opening. A direct and an indirect calibration method were applied both providing satisfactory level of accuracy. Validation of the bottom-up models was performed at different aggregation levels, including equipment specific unit operations, production lines and overall building energy consumption. The results indicated that for all types of energy utility, equipment and unit operation the consumption could be estimated with a relative error between 5% and 35% depending on the aggregation level. These results can motivate plant managers and process engineers to consider model-based estimation and analysis of energy utilities for monitoring and optimization purposes in industrial practice.