Foam is a very common element of industrial processes where liquids are stirred or liquids and gases are mixed. Foaming affects almost every industrial sector: from pharmaceuticals to brewing, from paint manufacture to waste water treatment, from oil & gas to food processing, from textiles to pulp and paper. Foam may be an integral and important part of a process or it may be an unwanted side effect. It has the appearance of a simple material, but in practice foam is a very complex, dynamic material with its production involving physical, chemical and biological processes. This can have significant impact on industrial processes. Foam-over events can damage equipment, ruin product batches and lead to enviromental pollution.
Foam measurement is difficult because foam, by its very nature, is insubstantial and highly variable, containing a small quantity of water or other liquid and a large quantity of air or other gas. What we see when looking at foam are liquid surfaces made up of thin films. It may appear to have physical substance but inside it is almost entirely gas and so is hardly distinguishable from the surrounding atmosphere. In practice the measurement of foam has to be able to detect very thin films of liquid which may be less than 1% by volume of the total foam. Additional factors such as poor system design and leaking pumps can exacerbate foaming problems. In all instances, in order to minimise the impact of foam, it needs to be effectively monitored, measured and controlled.
To control foam it is essential to understand the characteristics of the foam and then measure its thickness and, in some applications, where the foam-liquid interface resides. The traditional approach to foam control is to add a defoamer chemical to the process at a constant rate. This is a very hit and miss approach which is expensive, wasteful and not very reliable. By measuring the foam and detecting it has reached a significant level, it is possible to automatically use the optimum amount of antifoam only when it is required. This significantly reduces the cost while also improving the process control and reducing the risk of high levels of foam. It is therefore clear how important it is to implement effective foam control.
There have been attempts to monitor foam using existing level probe technologies adapted for foam measurement. In most applications, these fall short of providing either an adequate and sustainable solution.
Now, a highly versatile range of foam control systems have been specifically developed by Hycontrol to fulfil a variety of functions, including:
- Measuring the thickness of foam in a process
- Detecting foam-liquid interfaces
- Measuring liquid levels whilst ignoring the presence of any foam
The technology behind these systems originated from detailed research into foam control during pharmaceutical fermentation. The special measuring sensors and control equipment have been designed specifically for foam control and are not modified level sensors. It is important to emphasise that Hycontrol’s foam detection sensors are tools that have been specifically created for this task alone.