ABSTRACT
This chapter reviews the Odda process as developed and used by Norsk Hydro. A significant part of the required cooling load, approximately 75%, is obtained through evaporation of the ammonia used in the neutralization and conversion sections. The cold mother liquor can be utilized for precooling of the crystallizer coolant before it is pumped to the neutralization section. A substantial part of the water content of the mother liquor is evaporated by the heat of neutralization. In the Norsk Hydro process, the water content of the neutralized liquid is reduced to 0.5% at about 180 C by low pressure evaporation. Due to chemical reactions when mixing these salts with the hot melt the viscosity of the mixture has a tendency to increase to such a degree that prilling is seriously impeded. The main components in vent air from digestion, crystallization, and filtration are fluorine compounds, nitrogen oxides, and nitric acid vapor.
