The Aspergillus Niger fungus converts the sugars in the molasses in about one
week into raw citric acid at a temperature of between 25 and 35 ˚C.
This is a surface fermentation taking place in trays in fermentation rooms.
Step 2 : Isolation
Fermentation is followed by filtration,
removing all solid impurities from the fermentation liquid.
Next, the
citric acid is isolated as calciumcitrate by adding lime to it.
This
precipitate is afterwards dissolved by adding sulphuric acid, producing gypsum
and citric acid in solution.
Step 3 : Purification
A further purification and decolouration
takes place by means of an ion transfer and activated carbon.
Next,
the remaining water is evaporated, crystallising the pure citric acid.
By carrying out the evaporation at different temperatures the various product
forms are created.
Step 4 : Conditioning
By sieving the crystallised citric acid, granulates are brought about having a
grain size of between 75 and 1200 µm, as specified by the customer.
The product is shipped or transported to customers in variously sized bags or
in tankers.
Stap 5 : Valorisation
During isolation co-products emerge in
addition to raw citric acid, and they are all re-used. They are used as feed,
fertiliser, filling agent or a filter medium.
