Lesson 8 - Gases
In this lesson we take a closer look at gases, including compressed air. We will look at the quality requirements and specifications for use in the brewery. Different compressed air generation methods will be considered. For nitrogen and oxygen, we will look at the common uses, quality requirements, and options available for supply, storage, usage, and generation.
Point of Reflection – Reconvene
Welcome back. So, what were your thoughts?
Firstly, let’s look at the supply of air to your brewery. If the demand were suddenly high, the pressure would drop in the lines supplying air and the compressor would quickly have to start up and rectify this. In the time this takes, critical applications such as valves may fail because the pressure drops below the minimum required for them to operate correctly.
Secondly, the compressor would have to start and stop every time air is withdrawn by the brewery. This would be less efficient and use more power than if it ran continuously. Multiple starts/stops also increase wear and tear on the compressor and increase maintenance costs.
Thirdly, the compressors would have to be sized for maximum instantaneous demand, which means bigger, more expensive compressors as well as greater electrical demand. Compressors can also be damaged by high backpressures caused by a sudden drop in demand.
The main functions of an air receiver are to:
-
Minimise pressure fluctuations and sudden drops
-
Meet short-term demand peaks
-
Save energy
-
Safeguard against overpressures
Air distribution networks
In order to deliver air to the various users, a network of air pipes is used. The sizing of these is critical, as they need to be able to deliver the required volume of air at the correct pressure. Thus, the sizing must be such that the pressure drop across the line is not too great. The distribution systems are often in the form of ring mains, to aid in reducing pressure drop. Additionally, the pipes need to hold enough air so that the pressure will not drop when air use is at a peak. Whilst the networks can help to maintain pressure under normal circumstances, they are not designed to cater for abnormal circumstances such as an air line blowing off a valve. In a way, they are also air receivers.
Air pressure
Air pressure is controlled centrally at the discharge point of the air receiver. Where necessary in the plant, air regulators can be installed to provide the required air pressure to different processes.
Now we have covered compressed air, we will move on to other gases – oxygen and nitrogen.