Patent GB-828882-A (GB)
Title: Production of fertilizers
IPC: C05B1/02
Filed: 1955-11-28
Abstract: A pelleted fertilizer containing phosphate is produced by moving small discrete particles of the product of the reaction between an inorganic acid material and phosphate rock upon themselves while they are still moist and acidic to form agglomerates approaching the size of the desired pellets and, while continuing the movement, coating with absorptive finely-divided material, all internal chemical reactions resulting from the acidity of the material being permitted to proceed unhindered by extraneous heating or neutralization and the water content of the reaction product being such as to permit the interiors of the pellets to dry substantially entirely by crystallization alone.  The product may contain from 16 to 50% P2O5, and the original phosphate rock may be low in phosphate and high in metal impurities such as iron and aluminium.  The inorganic acid material may be sulphuric acid which has been used in the purification of petroleum products and contains oils and gums, or a preponderantly dry acid sludge containing a mineral acid together with a fertilizer ingredient, as described in Specification 828,883 may be used.  Metal salts which may be added to the material at any stage before coating of the pellets are salts of aluminium, iron, copper, magnesium (e.g. as dolomitic limestone), manganese, zinc, barium, chromium cobalt, nickel, and strontium.  Other fertilizer ingredients that may be added are ammonium sulphate or nitrate, potassium nitrate, chloride or sulphate, or urea; these may be added either in finely-divided dry form or in moist or liquid form, and may be premixed with the discrete particles or added thereto at the start of the agglomerating operation and mixed by the movement thereof. Where an ammoniated liquid is used, it is first neutralized with sulphuric or other acid.  The moisture added by such additions is compensated for by adjustment of the moisture supplied by the acidic material.  The coating material may be ground phosphate rock, a mixture of such rock and charcoal, bone black, ground dolomite, bone char, lamp black, a nitrogen-containing organic material such as animal tankage or cottonseed meal, or a potassic or phosphatic dust. The pellets may be spread in shallow layers to dissipate the heat of secondary reactions.  When phosphoric acid is used, all the acid required is mixed with the rock and the mixture is broken up into discrete particles as soon as it has sufficiently hardened.  Example 1 describes the production of pellets from the product from ground Florida pebble rock and sulphuric acid, using ground rock for coating; Example 2 their production from raw superphosphate, potassium nitrate, urea, diammonium phosphate and potassium chloride, animal tankage being used as coating material; Example 3 their production from the product from ground phosphate rock and phosphoric acid, ground rock being used as coating material; and Example 4 their production from the product from ground phosphate rock and a mixture of sulphuric and phosphoric acids, ground rock being used as coating material.ALSO:A pelleted fertilizer containing phosphate is produced by moving small discrete particles of the product of the reaction between an inorganic material and phosphate rock upon themselves while they are still moist and acidic to form agglomerates approaching the size of the desired pellets and, while continuing the movement, coating with absorptive finely divided material, all internal chemical reactions resulting from the acidity of the material being permitted to proceed unhindered by extraneous heating or neutralization and the water content of the reaction product being such as to permit the interiors of the pellets to dry substantially entirely by crystallization alone.  The product may contain from 16 to 50% P2O5, and the original phosphate rock may be low in phosphate and high in metal impurities such as iron and aluminium.  The inorganic acid material may be sulphuric acid which has been used in the purification of petroleum products and contains oils and gums, or a preponderantly dry acid sludge containing a mineral acid together with a fertilizer ingredient as described in Specification 828,883 may be used.  Metal salts which may be added to the material at any stage before coating of the pellets are salts of aluminium, iron, copper, magnesium (e.g. as dolomitic limestone), manganese, zinc, barium, chromium cobalt, nickel, and strontium.  Other fertilizer ingredients that may be added are ammonium sulphate or nitrate, potassium nitrate, chloride or sulphate, or urea; these may be added either in finely-divided dry form or in moist or liquid form, and may be premixed with the discrete particles or added thereto at the start of the agglomerating operation and mixed by the movement thereof. Where an ammoniated liquid is used, it is first neutralized with sulphuric or other acid.  The moisture added by such additions is compensated for by adjustment of the moisture supplied by the acidic material.  The coating material may be ground phosphate rock, a mixture of such rock and charcoal, bone black, ground dolomites, bone char, lamp black, a nitrogen-containing organic material such as animal tankage or cottonseed meal, or a potassic or phosphatic dust. The pellets may be spread in shallow layers to dissipate the heat of secondary reactions.  When phosphoric acid is used, all the acid required is mixed with the rock and the mixture is broken up into discrete particles as soon as it has sufficiently hardened.  Example 1 describes the production of pellets from the product from ground Florida pebble rock and sulphuric acid, using ground rock for coating, Example 2 their production from raw superphosphate, potassium nitrate, urea, diammonium phosphate and potassium chloride, animal tankage being used as coating material, Example 3 their production from the product from ground phosphate rock and phosphoric acid, ground rock being used as coating material, and Example 4 their production from the product from ground phosphate rock and a mixture of sulphuric and phosphoric acids, ground rock being used as coating material.