Lesson 8 - Gases

Gases play a big role in a brewery, and interact with the product in many ways. In this lesson, we will focus on compressed air, oxygen, and nitrogen. Carbon dioxide will be covered in the next lesson.

Compressed air is critical to operate valves and other actuated equipment, and can also be used to provide top pressure. Oxygen is added to wort to ensure yeast growth during fermentation. Nitrogen is used in certain breweries where beer is nitrogenated. It can also be used as a purging gas in instances where CO₂ is not collected or is insufficient for all the brewery’s needs.

Gases have been covered in other lessons, so the focus here is on the supply of gases to the brewery and the equipment required for this. Gas laws and transfer mechanisms are covered in the Gases Unit. However, a basic understanding of gas laws is useful for understanding some of the principles in this lesson, so the following is a brief overview of some of the applicable gas laws. Gas laws assume that gases are ‘ideal’, i.e. that they act in accordance with gas laws. This is true under certain conditions, and is true to a large extent for the gases we will cover in this lesson.

Boyle’s law

Boyle’s law states that for a fixed mass of gas at a fixed temperature, that the pressure (P) is inversely proportional to its volume (V). This is shown below:

So, for the same mass of gas, the pressure multiplied by the volume will be the same.

It is important to note that we are referring to absolute pressure and not gauge pressure.

Universal gas law

Temperature also plays a part in the behaviour of gases. The universal gas law brings temperature into the equation.

The important thing to remember here is that the temperature relationship is measured in Kelvin (K) and not Celsius or Fahrenheit.

As mentioned, this lesson is not focused on these laws, but this basic knowledge makes some concepts easier.

Let’s now continue and look at compressed air in more detail.