GB426472A - Improvements in and relating to the production of granulated materials - Google Patents

Abstract

<PICT:0426472/III/1> <PICT:0426472/III/2> <PICT:0426472/III/3> Material to be granulated is first brought into a moist plastic condition, if necessary by moistening with liquid, solution or vapours or mixtures thereof, is then subdivided into loose particles corresponding to the grain size desired, and is then dried in an apparatus of the kind having a number of substantially flat trays maintained in vibratory motion so that the material is transferred from tray to tray, through the apparatus. In a modified process for treating material of which a portion is in the desired granular condition, the remainder is brought into the plastic condition, and the two portions are mixed before treatment in the vibratory drier. The first process may be applied to a single material such as potassium chloride or nitrate, ammonium sulphate or phosphate-containing and similar fertilizing materials, or to mixtures of materials, for example, a mixture of ammonium sulphate and nitrate. In a similar manner metal oxides and ores, potassium cyanamide-phosphate fertilizers, super-phosphate, Thomas meal, soda, sodium sulphate and salt may be granulated. Examples of the second method of treatment are also given, viz. (2) calcium nitrate grains of diameter 1--2\ba1/2\be mm. are mixed with ammonium nitrate solution and clay or loam or leucite meal, and the whole is subdivided and dried; (3) moist ammonium nitrate granules of ,5 to 1,5 mm. diameter are agitated with finely divided lime and dried; (4) ammonium nitrate and potassium chloride in granulated form are mixed with milled diammonium phosphate and an acidified solution of potassium chloride and ammonium nitrate and then conveyed to the drier. For subdividing material treated by the first method, a rotary miller and cutter having perforations corresponding to the desired grain size may be used. Plastic and granular materials may be mixed in a container having parallel spindles rotating in opposite directions the spindles having intermeshing vanes which subdivide and advance the materials, the space between the vanes corresponding to the grain size desired. The drying device may comprise a series of independently sprung trays, with baffles to guide the drying gas or the entire housing may oscillate, as in the form shown. The trays may be perforated or slotted and may have varying inclinations. In this form the material introduced through a shoot a is forced through a sieve by plungers k into the housing c, and passes alternately over domed and dished trays to the outlet m. Hot gas enters at g. The Specification as open to inspection under Sect. 91 comprises also the production by the second method of granules of pure and crude potassium chloride, using a mother liquor as moistening agent; and to the modification of the surface of a material, e.g. ammonium sulphate, by treatment with a liquid such as nitric acid. Further examples describe the production of a fertilizer containing precipitate meal or magnesium phosphate, milled ammonium nitrate or potassium chloride, ammonium nitrate solution, and granular potassium chloride or sulphate. Example 4 above may be modified by using monoammonium instead of di-ammonium phosphate, or potassium sulphate instead of potassium chloride. A simpler fertilizer may be made from superphosphate or precipitate and potassium chloride meal or solution and potassium sulphate. A meal of brown coal or peat, saturated with ammonia if desired, is mixed with di-ammonium phosphate, urea, potassium chloride or sulphate, and moisture, and dried in a rotating drum to form a fertilizer. Example 3 above may be modified by milling part of the ammonium nitrate and mixing it with the lime. A catalyst for the reaction of methane with steam is made from Chamotte material, zirconium dioxide meal, and a solution of cerium and nickel nitrates. Hydrated iron oxide may be mixed with zinc oxide, tragacanth powder and chromic acid solution, and the whole subdivided and dried. Iron and manganese ores, zinc blende and pyrites are similarly granulated. In other forms of drying apparatus described, the trays are arranged in two oscillating systems, each operated by an eccentric rotating mass, the trays of one system alternating in position with the trays of the second system. Various types of supporting springs may be used. The horizontal mixing, subdividing and conveying device having varied spindles as previously described is shown in Fig. 3 (Cancelled). The plastic material may be milled and subdivided by a perforated, horizontal or inclined, rotating or oscillating roll, the perforations having raised lip to effect milling. The weight of material in a bunker may give the necessary milling pressure, or the pressure may be given by one or more pistons, as shown in Fig. 7 (Cancelled), or by the bunker door, or a horizontal or vertical milling screen may be used. This subject-matter does not appear in the Specification as accepted.