Patents by Inventor Torstein Obrestad

Torstein Obrestad has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • NPK complex fertilizer
    Patent number: 4713108
    Abstract: 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.
    Type: Grant
    Filed: September 11, 1985
    Date of Patent: December 15, 1987
    Assignee: Norsk Hydro, a.s.
    Inventors: Olav Kjohl, Torstein Obrestad, Hans Groland