CH98564A - Process for the manufacture of a fertilizer based on urea nitrate from cyanamide. - Google Patents

Description

  

  Process for the manufacture of a fertilizer based on ui nitrate from cyanamide. In order to prepare urea nitrate which can be used for the preparation of fertilizers from cyanamides, the free cyanamide in aqueous solution is generally treated with nitric acid. The acid converts cyanamide into urea and the latter into hardly soluble urea nitrate.



  The main drawbacks of this process are as follows: 1 The solutions of free cyanamide, generally very large, must be offset by evaporation, either at ordinary pressure or in a vacuum. According to a recent patent relating to this preparation, the concentration must be pushed to a syrupy consistency. However, it is impossible to economically eva pore aqueous solutions of cyanamide, this substance being volatile with water vapors and, moreover, very prone to polymerization.

   The cyanamide yields thus becoming highly defective, it goes without saying that the production of urea nitrate must suffer the consequences. Since nitric acid is a relatively expensive acid, it is obvious that any preparation based on the use of this product must be able to withstand high raw material costs.



  The object of the process which is the subject of the present invention aims to overcome these drawbacks, According to this process, - a concentrated solution of cyanamide is prepared while avoiding any evaporation and this solution is transformed into a fertilizer based on urea nitrate by adding sulfuric acid and a nitrate in an amount equivalent to the acid side. This nitrate can be for example an alkali nitrate (sodium, potassium), ammonium nitrate, a nitrate of an alkaline earth metal (calcium, magnesium) etc.



  For the implementation of this process, one can, for example, operate in the following manner: First decomposes nitrogenous lime with carbonic acid in the presence of water and a cyanamide solution is obtained. free which is filtered to get rid of the carbonate of lime, charcoal and other insoluble im purities.

   This operation is repeated with the filtered solution which thus returns to successive extractions, in order to be able to obtain as large a concentration as possible of cyanamide. Considering the instability of the concentrated solutions of this body, especially in the presence of weak bases, care must be taken to avoid prolonged contact of the solutions with nitrogenous lime; it is, on the other hand, necessary to rid the residue completely of all traces of free cyanamide retained by the carbon and carbonate of lime.

   To achieve these results without compromising the desired goal, the solutions used for multiple extractions should be monitored, taking care to slightly acidify them by adding small amounts of acid or keeping them away from the environment. 'air, that is to say in an atmosphere of carbon dioxide which will be introduced under pressure if possible.



  The concentrated cyanamide solution obtained is added to 53 or <B> 600 </B> B sulfuric acid and a corresponding amount of alkali, ammoniacal, magnesium nitrate, etc.



  The mixture is left to stand overnight and the mixture is heated in a water bath until the free cyanamide has completely disappeared, which generally requires one to two hours.



  The urea nitrate formed is deposited in the cold in transparent spangled crystals and can optionally be separated from the sulphate of ammonium, potassium, magnesium, etc. by filtration.



  The mixture of urea nitrate and ammonium or potassium sulphate can often be used as it is as a fertilizer after having been free of all excess moisture without prior separation.



  In view of the fact that the acid which is used for the conversion of cyanamide can be used within certain limits in variable quantities, it is also possible to obtain mixtures containing free urea and urea nitrate, or else urea, urea nitrate and alkali, ammoniacal, magnesian sulphates etc.



  Ammonium sulfate in solution, separated by filtration from the urea nitrate crystals, as described above, can be converted back to ammonium nitrate by treating the concentrated solution with nitrate of lime. Lime sulphate precipitates and absorbs two water molecules, turning into plaster. The ammonia nitrate in highly concentrated solution is evaporated to dryness and can be used again. The mixture of lime sulfate and ammonium nitrate obtained as a by-product can also be dried directly and used as it is as a fertilizer in the agi-ictiltui, e.

 

Claims (1)

CLAIM Process for the manufacture of urea nitrate-based fertilizers from cyanamide, characterized in that a solution of free cyanamide is first prepared, in that this is then enriched. solution while avoiding evaporation and in that sulfuric acid and a nitrate are added to this solution in an amount equivalent to this acid. SUB-CLAIM Process according to claim, in which ammonium nitrate is added to the solution of cyanainide and sulfuric acid, separates the precipitate from the liquid and regenerates the ammonium nitrate by the addition of nitrate of lime which forms with ammonium sulphate ammonium nitrate and insoluble lime sulphate.