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Teil 3 Seite 4-27
tion, contain the lowest possible concentrations of volatile free fatty acids which are
evaporated in particular as a result of high temperatures (� 130 °C) during drying.
Achieved environmental benefits
The ammonia from the water vapour from rendering is converted into an easy to use fer-
tilizer, where 25% of the nitrogen comes from the rendering process. This fertilizer can
replace the same product where all the nitrogen is chemically synthesized from molecular
nitrogen from air with about 1 kg of fuel oil consumption per kg of synthesized nitrogen.
On the other hand, nitrogen removal from waste water from rendering can be avoided
where ammonia is converted back into molecular nitrogen by bacterial processes (nitrifica-
tion and denitrification).
Cross media effects
The only immediate product of the process is a concentrated ammonium nitrate solution
(typically 55%) and an acidic vapour containing low molecular carboxylic acids (acetic
acid, propionic acid, butyric acid and others). These acids are ideal substrates for aerobic
and anaerobic waste water treatment processes, where they contribute either to the pro-
duction of biomasss or to the production of biogas. The nitric acid used to convert ammo-
nia into the corresponding ammonium cation can be a waste acid from nitrification proc-
esses in concentrations below 50%.
Operational data Applicability
The process can be used everywhere, where the water from drying during the rendering
process is still in the vapour form. This vapour can then flow through the packed column
before it is used in a second evaporating stage or condensed without any secondary use.
Economics
This process avoids the energy consuming biological nitrification and denitrification for
the removal of nitrogen from condensed water vapour from rendering processes. The
main energy consuming device in this process is the pump for the slightly acidic ammo-
nium nitrate solution.
Driving force for implementation
Easy control of ammonia nitrogen in water vapour from rendering. The nitrogen content
in the acidic vapour leaving the process can even be adapted to the nitrogen demand in
the subsequent biological waste water treatment plant.
The product formed in this process can easily be sold as a fertilizer in all countries,
where a concentrated ammonium nitrate urea solution containing 28% N is used as liquid
fertilizer.
Example plants
Currently, this type of ammonia converter is utilised at the Brögbern (Lingen) and Regau
(Upper Austria) animal carcass disposal plants (comp. 4.12.1c). The converter at the