Brewing with Alicat: Controlling carbon dioxide sparging
Beer is the beverage of choice for billions of people around the world. Whether ale, lager, or stout, carbon dioxide sparging is the process by which beer gets carbonated – making it the not-so-subtle difference between a refreshing pint and a flat disappointment.
The average beer drinker is like to have strong feelings about what constitutes the “perfect” bubble size and amount of carbonation. While it is easy enough to demand a perfect beer from over the counter, the process used to make a perfectly carbonated beer is fairly complex.
The physics of carbonation
For commercial beers, carbonation most frequently involves sparging carbon dioxide into the bottom of a brite tank (the vessel containing chilled, filtered beer). The colder the beer is in the brite tank, the more CO2 it can hold, so the brite tank may be actively controlled to stay at a specific temperature.
At a given liquid temperature, the amount of carbon dioxide that can dissolve in the beer is directly dependent on the partial pressure of the supply CO2 in the tank.
The pressure differential enables the brewer to sparge carbon dioxide: the CO2 can be forced through a porous stone, which creates bubbles at the bottom of the tank. The multitude of tiny bubbles means that a great deal of gas surface area is in contact with the beer – which speeds up the dissolution of CO2 into the beer.
Controlling sparging using mass flow
Mass flow controllers offer a simple way of controlling CO2 sparging into the brite tank, as they can be used to control either pressure or flow rate of the CO2 that is delivered to the carbonation stone. Traditionally, pressure is the control variable used for carbonation. When the headspace pressure in the brite tank is equal to the pressure delivered to the carbonation stone, the brewer knows that the beer has reached equilibrium. At this point, the carbonation is complete.
While controlling the mass flow rate instead of the pressure is unorthodox, it offers the advantage of knowing exactly how many volumes (mass, for the non-brewers among us) of CO2 have entered the brite tank. This makes mass flow a more precise measurement for carbonation, as it is not susceptible to changes due to temperature fluctuations.
Alicat mass flow controllers specifically offer additional advantages to enable high-accuracy brewing. For one, they are multivariate, simultaneously measuring mass flow, volumetric flow, gas temperature, and gas pressure. They can also be ordered with a totalizer option, allowing the brewer to track the total mass of carbon dioxide delivered to the brite tank. The total number of desired CO2 volumes can be pre-programmed to be dispensed at a specified flow rate. This method enables control over both the amount of CO2 and the time period over which it is delivered. This allows the brewer to automate two process variables, maintaining maximum consistency between batches.
Mass flow controllers enable the brewer to automate the carbonation process. As such, precision carbon dioxide sparging can save brewers time and money, while allowing for a more consistent, predictable brewing process.