Evaporator Train Heat and Material Balance Development for Use as a Troubleshooting Tool, TAPPICon25

Kraft pulp mills depend on efficient operation of multiple effect evaporators to consistently achieve optimal pulp production levels. While improvements in technology have simplified Evaporator Train (Set) troubleshooting, operating problems still occur where having a comprehensive, steady-state simultaneous Heat and Material Balance (HMB) offers a look inside the evaporator train “black box” to either pinpoint the source of the problem or to narrow down the list of suspects. While the science and fundamentals behind the Evaporator HMB are well established, many kraft mills do not take full advantage of this proven troubleshooting tool.

This paper narrates the development of a Multiple Effect Evaporator (MEE) HMB based on a real-world example. It reviews techniques for identifying and collecting required data and describes how to validate a working HMB. Microsoft Excel with Visual Basic for Applications (VBA) macros was the chosen software for this exercise, but the fundamental simulation techniques and troubleshooting capabilities apply regardless of software platform (such as WinGEMS, CADSIM Plus, or IPSEpro). Steam properties are determined using WinSteam as an Excel add-in. A Rising Film Evaporator train (with tubes) coupled with a Falling Film Concentrator (with tubes) was selected as the example for this exercise, but the fundamental techniques apply to other Falling Film equipment as well.

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