A lumped parameter dynamic model, using both Excel (R) and HYSYS (R) software, for industrial refinery/upgrader VGO hydrotreaters has been developed from proprietary and public steady state hydrotreater models. The model is based on industrial plant data to track changes in intrinsic reaction rate based on catalyst deactivation, wetting efficiency, feed properties and operating conditions to provide useful information, such as required operating temperature, outlet sulfur composition and chemical hydrogen consumed. The model credibly simulates local disturbances, and represents the three distinct operating zones during hydrotreater run length (start, middle and end). This correlative, partially predictive model can be applied to demonstrate the tangible economic benefits of increasing hydrogen use to improve the operation of a hydrotreater by increasing run length and/or improving crude processing. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.