Mass flow measurement of steam coupled with an associated control system has saved Matt Brewing Company in Utica, N.Y. up to $630 a day for wort boiling. The savings resulted from reduced natural gas and water usage. The new system typically reduces steam use by about a third. It also saves about 1,200 gallons of water per brew. Brewing supervisor Rich Michaels estimates that the payback time for the instrumentation project is three to four months.
The new instrument system measures the steam flow rate and temperature to derive mass flow for controlling heat delivered to the wort, a sugary solution. The process takes place in one of a pair of 500 bbl (15,000-gallon) kettles. One kettle boils wort while the other undergoes cleaning. Boiling continues for 90 minutes, evaporating about 5 to 10 per cent of the solution. The operation, which includes addition of hops, sterilizes the wort and affects flavour, stability and consistency.
From the steam header, the saturated steam flows through a control valve and ABB Swirl flowmeter before reaching the operating kettle. Michaels notes that the Swirl meter requires minimal upstream and downstream straight pipe compared to other flowmeter types. "Our existing piping geometry was tight," says Michaels, "leaving very little space for straight pipe to condition the steam flow. The Swirl meter contains built-in straightening vanes, saving us the expense of re-piping the brewhouse."
When starting a batch, the operator dials data representing the volume of wort in the kettle into an ABB ControlMaster CM10. This unit calculates the optimum mass flow rate of steam based on wort volume, and feeds that rate to the unit as a setpoint. It provides indication, recording, math functions, and proportional/integral control of the steam mass flow.
Control signals from the unit enter intelligent electro-pneumatic positioners installed on the existing Fisher control valves. An I/P module within the positioner precisely regulates air flow to pressurize and depressurize the valve while minimizing air consumption. The system maintains the optimum mass flow of saturated steam for wort boiling, avoiding overheating that can adversely affect the brew.
"The results," says Michaels, "are better quality and shelf life for our products with the added benefits of reduced energy and water usage."