Figure 1. Basis case flowsheet for one minute of operation of a continuous aluminum heating process. Gas stream flows are at 1 atm pressure. Flow of streams 2, 3, 4 and 5 were obtained from a material balance and the heat loss from a heat balance.
Previous columns in this series have illustrated the use of Excel for making material- and energy-balance calculations on industrial heating processes. If you’re lucky, you can get enough plant data to keep the material and heat balances separate. But once you extrapolate your balances to situations where you don’t have plant data, the material- and heat-balance equations often become coupled. In that case, both must be made together, which complicates the arithmetic. The combination of a material and heat balance is called a system balance. The purpose of a system balance is to explore what happens to the system when you change one of the process variables. Here we show how to use Excel’s Goal Seek tool to make a system balance on an aluminum heating process. In part 2, we’ll show how to use Excel’s Solver tool.