Norsk Hydro, A.s.

Aksjeselskapet Norcem

Olav Kjohl

Torstein Obrestad

Paul Henrik Olstad

Per F Gustavsen

Ellen Brekke

Arne O Egner

Tore Elstrom, Deceased

Hans Groland

The present invention relates to NPK-fertilizer manufactured during application of KCl and/or K.sub.2 SO.sub.4 as potassium source and which also contains magnesium in an amount of 0.2-3.0% calculated as MgO and added in the product as MgO, and method for manufacture of this product. The special features of the method is that to an evaporated nitrogen, phosphorous solution 0.2-3.0% reactive MgO and potassium salts are added before prilling or before/during granulation. MgO is preferably added as lightly calcined MgO having an average particle size of 0.2-3.0 mm, and is added in the mixer just before the prilling means. The new product has reduced tendency to swelling and caking.

NPK complex fertilizer

The present invention relates to ammonium nitrate or products having a high content of ammonium nitrate stabilized against swelling and break-down by thermal cycling, and a method for manufacturing such products. An amount of 0.05-1.0 weight % porous particles having a surface area of 150-400 m.sup.2 /g and a pore size of 100-300 .ANG.ngstroms are included in the products. As porous particles, preferably silicon dioxide particles having a surface area of 250-350 m.sup.2 /g and a pore size of 100-250 .ANG.ngstroms are used. The products are made by first drying granulated or prilled ammonium nitrate or products having a high content of ammonium nitrate and thereupon coating them with the porous particles, and if desired also adding a dust-binding agent and/or an anticaking agent. Ammonium nitrate thus conditioned is both as stable and porous as required for use in explosives and in addition it meets the requirements for so-called tropical grade ammonium nitrate. Fertilizers according to the invention, having a high content of ammonium nitrate, will also have an improved caking number and reduced tendency to dust formation because the water present will be bound in the pores of the conditioning agent.

Stabilized ammonium nitrate or stabilized products having a high content

A method for the production of urea of high mechanical strength by the crystallizing process or the evaporation process, including a prilling or granulating step, utilizing 0.01-1% by weight of formaldehyde in the form of a formaldehyde polymer, which comprises, before prilling or granulating, incorporating in the urea, a formaldehyde polymer with a formaldehyde content of 82-97% and with a melting point of about 90.degree.-160.degree. C.

Method for the production of urea of high mechanical strength

Concrete having high resistance to corrosion is prepared by using low aluminate (C.sub.3 A) cement, preferably having less than 5 weight per cent of aluminate, and, in addition to conventional concrete constituents, at least 10 weight per cent of finely divided, reactive silica based on the cement weight. A highly corrosion resistant cement composition comprises, in addition to conventional cement constituents, 70 - 90 parts by weight of low aluminate cement and 10 - 30 parts by weight of reactive silica. An additive useful for making concrete highly corrosion resistant comprises 80 - 90 weight per cent of reactive silica, 0 - 10 weight per cent of low aluminate cement, 3 - 8 weight per cent of formaldehyde condensed sodium sulfonate, 3 - 8 weight per cent of lignosulfonate.

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Heistad, Norway

Olav Kjohl