Coalescing liquids will always present more of a problem. In addition to water, other compounds that are liquids at room temperature (e.g., sulphuric acid) may be present in the sample stream. The system can remove these higher-boiling-point compounds by condensation and subsequent filtration in a coalescing filter, while water remains in the sample stream until removed in the vapour state by a gas dryer. Alternatively, the Peltier cooler will remove all the condensing vapours at one go by condensation to a low temperature. Both of these methods are acceptable, providing one can live with the limitations of the system.
The improvement in the flue gas analyser has led to the need for better sample conditioning systems and hence advances in this field are to be expected. Thsi is a general discussion of the different types of sample conditioner and their various characteristics.
A good sample conditioning system requires a heated hose to connect the sample conditioner to the source of gas so as to receive the sample in good condition without losing any of the soluble components.
The permeation dryer is another, very powerful way of removing moisture from a gas stream and possesses advantages over other methods. This is mostly a discussion of the chemical background to permeation of gases through a membrane.