Stability

Polymerisation or deterioration of the liquid can be caused by temperatures above around 100°C which adversely affect physical properties such as viscosity, phase separation, and deposition of a bitumen-like substance. Heating the liquid to reduce viscosity for pumping or atomisation needs to be considered carefully and thoroughly tested, although in-line steam heating to 90°C has been used successfully in combustion trials (42). Exposure to air also causes deterioration, but at a slower rate than temperature increase. Maintenance in a sealed enclosure has been claimed to cause substantial pressure increases, so some minimal venting is necessary to avoid pressure build-up, but minimise exposure to oxygen. Pyrolysis liquid has been stored in this way in a useable form for up to two years without problems. Liquids produced from refuse/MSW appear to be much more unstable (119,131,132).

The low pH arises from the organic acid content (e. g. acetic and formic acids), and is therefore corrosive. Mild steel is not suitable for handling or storage. Polypropylene piping has been used to overcome this problem.