Formation of flammable gas mixtures in extraction towers and procedures for its avoidance

In the 1993 campaign a deflagration occured during welding works in the area of the tower extraction plant in one of the Südzucker factories. Measurements that were thereupon arranged for in the headspace of the extraction towers showed a formation of an inflammable gas in alarmingly high concentration. The detailed examination revealed hydrogen as the main component of the gas. Organic components, e.g. methane, alcohols, etc. could only be found in traces. Hydrogen is a metabolic product of thermophilic, anaerobic bacteria, known as clostridia. In the middle of the 1960s an infection of clostridia was observed in Austrian sugar factories. Due to the common practice of sulphurizing in those days, this resulted in formation of hydrogen sulphide gas in the extraction. In that case the gas formation could be suppressed by injection air into the extraction towers. As this report shows, the unwelcome formation of hydrogen can also be effectively combatted by injecting air into the extraction towers. The way of proportioning the air injection is described. Additionally, the examinations that are carried out up to now give some hints about possible technological advantages. They are also described in the report.