GB934510A - Process for the granulation of calcium nitrate melts containing ammonium nitrate of approximately the formula 5 ca(no) nhno .10ho - Google Patents

Abstract

<PICT:0934510/III/1> A calcium nitrate melt containing ammonium nitrate is granulated by division into drops which fall into a mineral oil containing a seed material so that the drops cool during the fall and solidify into granules, and the drops fall through a zone in the mineral oil with a seed material content of from 0,01 to 0,5% by weight and having a maximum temperature of 52 DEG C.; the seed material content is brought to or kept at the required value by addition of one or more of Ca(No3)22H2O, Ca(NO3)23H2O and Ca(NO3)24H2O. The approximate formula of the melt is 5Ca(NO3)2 NH4NO310H2O. The proportion by weight of water is between 12 and 17%, and the proportion by weight of ammonium nitrate does not exceed 0,44 times that of water. The solidified granules collect in the bottom of the oil shaft 5 from which they pass with oil through line 6 to a filter 11; the granules pass from here to a centrifuge 14, where adhering oil is flung off and passes to reservoir 13; oil also passes over the upper rim of shaft 5 and passes via line 8 through a cooler 9, which may also be used as a heater, to filter 11. The oil passes from filter 11 to reservoir 13, to which seed material may be added through line 19. The oil (with seed material) is then pumped back through line 23, where its temperature is maintained (by cooling or heating in cooler 9) above 30 DEG -40 DEG C. (according to viscosity) and below 52 DEG C., into shaft 5. The seed material in the oil flows slowly upward in shaft 5 and comes into contact with the drops to be solidified. Some unconsumed seed material will leave the shaft with the oil via line 8 and possibly also through line 6. A small proportion of the calcium nitrate melt will be converted into finer particles of calcium nitrate, which remain suspended in the oil and act, on recirculation as seed material. Hence the flow of fresh seed material through line 19 can be reduced or discontinued. The oil used may be kerosine, gas oil, spindle oil or light machine oil. If 10% or more normally soild hydrocarbon wax, e.g. macro- or micro-crystalline paraffin wax, or ceresine wax, is present in the oil, granules may be obtained having a layer of solid hydrocarbon to reduce moisture sensitivity, and delay the availability in soil. Specifications 313,652 and 794,855 are referred to.