1996 Shirley Laroche 5514307 process for reducing emissions during prilling
This invention relates to an improvement in prilling whereby water is atomized into a prill tower to affect faster solidification of the prill, and in particular, the outside surface of the prill by providing an increased rate of surface cooling while reducing the required air flows in the tower. This results in a major reduction in air pollution potential in the form of both fume and particulate while at the same time allowing substantial production rate increases. Specifically, the invention relates to quick freezing the outside surface of the prill by flash evaporation of finely atomized water particles on the surface of the prill or in extremely close proximity to the prill to greatly lower the vapor pressure at the prill’s surface and by continued flash evaporation to enhance cooling so as to allow upward flowing air to be reduced to a point where micro-prills which are formed in prilling can settle in the prill tower while obtaining the same or increased production rates. More specifically, the present invention relates to an improvement in melt prilling of water sensitive materials, in particular, ammonium nitrate, urea, potassium nitrate and other water soluble melts which normally absorb water or go into solution readily at ambient conditions in their solid state.