VERFAHREN ZUR GÄRUNG VON BESONDERS ZÄHFLÜSSIGEN SUBSTRATEN UND VORRICHTUNG FÜR DIE EINMISCHUNG VON LUFT IN DAS SUBSTRAT

摘要

A method for fermentation of especially highly viscous substrate is carried through with a controlled mixing of air. The addition of air takes place in two steps, where in the first step a small amount of substrate is mixed with a larger amount of air such that a foam containing air bubbles is formed. In the second step the foam is distributed and mixed into the substrate in a mixing zone, at which very small air bubbles are formed. The rising speed of the bubbles is so low that the degree of utilization of oxygen in the added air is above 20 %. An arrangement for addition of air in highly viscous substrate comprises a tube (1) for addition of air to a rotating foam forming means (2) which is submerged in the substrate in a fermentation tank. The means comprises two elements where at least one of the elements has a side with a structure with lowered and/or raised parts. The elements are arranged to be movable in a transversal way in relation to each other with a mutual distance corresponding to the desired size of the liquid lamella. The spaces which are present in the lowered parts in the structure are connected to the tube for addition of air and surrounding substrate.