GB1558476A - Basic slag/superphosphate composition - Google Patents

Description

(54) BASIC SLAG/SUPERPHOSPHATE COMPOSITION (71) We, FISONS LIMITED, a British Company of Fison House, 9 Grosvenor Street, London W1X OAH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a fertilizer composition, notably one comprising a mixture of a low P2OJ slag and single superphosphate and is a modification or improvement in the invention described and claimed in our British Patent No. 1,395,504, hereinafter termed the Parent Patent.

The Parent Patent describes and claims a mixture comprising at least 60 parts by weight of basic slag and less than 40 parts by weight of a superphosphate; the slag and the superphosphate both having particle sizes of less than 1,000 micrometres. We have now found that agronomically acceptable mixtures having properties closely resembling basic slags may be prepared using lower proportions of slag.

Accordingly, the present invention provides a mixture comprising a slag containing less than 8% by weight of P2O and single superphosphate in weight proportions of more than 0.8:1 to less than 1.5:1 respectively.

The slag for present use contains less than 8% w/w P2O, and is a slag derived from a steel making process, notably the LD process. Typically the slag contains 2 to 5% by weight of P2O,-.

The slag is desirably in comminuted form, e.g. as a powder or granules, and has a mean particle size of less than 1,000 micro metres.

Such comminuted slag is commercially available.

The single superphosphate for present use is conventionally that used in the fertilizer industry. As with the slag, the superphosphate is desirably in comminuted form and has a preferred mean particle size of less than 1,000 micrometres.

The precise proportion of superphosphate to slag in the mixture will vary according to the desired final phosphorus level in the mixture and the initial phosphorus levels in the slag and superphosphate. It is usually desired that the mixture contain a total of from 10 to 20%, preferably from 12 to 15%, e.g. about 13%, by weight of P205. Thus, a typical mixture of the invention will contain 45 to 59%, e.g. 50% by weight of LD slag and from 55 to 41%, e.g. 50%, by weight of single superphosphate.

Tn addition to the slag and superphosphate, the mixture of the invention may contain other fertilizer ingredients, such as potassium chloride or potassium sulphate; pigments or dyestuffs; herbicides; fungicides and binders. The mixture may also contain some water, although it is preferred to use substantially dry ingredients and to limit the amount of water to less than 2% by weight of the total dry weight of the mixture.

The mixture of the invention may be made merely by dry mixing the various ingredients.

Some reaction may occur between the slag and the superphosphate which would cause the mixture to solidify on standing. We therefore prefer to carry out the mixing under such conditions that the reaction takes place during the mixing. Conveniently, this is achieved by milling, a mixture of slag and superphosphate particles having sizes greater that that desired until the particles have the desired size. Typically, crushing is carried out in ball or tube mill for a period of about 20 to 30 minutes to ensure adequate drying and mixing of the mixture and to ensure substantial completion of all chemical reactions.

The mixture of the invention is used as a fertilizer in the same way as comminuted basic slag. The mixture is of especial use on acid soils.

The invention will be illustrated by way of the following Example in which all parts are by weight: Example Basic slag obtained during the LD steelmaking process (3% P2Ob, and of particle size from 4 inches downwards) and single superphosphate (26% P2Os, 5% H2O and of particle size 10 to 3,000 micrometres) were fed to a tube mill in a weight ratio of 11: 9.

The mixture was crushed to an overall particle size in the range 1 to 100 micrometres, for some 20 minutes. The temperature attained during crushing was 65"C.

The product from the mill crusher was a free flowing material with a pH of more than 10 (as measured for a 10% slurry in distilled water using glass electrodes), having a total P20 content of 13.3 ó of which 95 '.

of the P2O, was citric acid soluble.

WHAT WE CLAIM IS:- 1. A mixture comprising slag containing less than 8% by weight of P2O and single superphosphate in weight proportions of from more than 0.8:1 to less than 1.5:1 respectively.

2. A mixture as claimed in claim 1 wherein the slag is LD slag.

3. A mixture as claimed in either of claims 1 or 2 wherein the slag and superphosphate both have a mean particle size of less than 1,000 micrometers.

4. A mixture as claimed in any one of the preceding claims which contains a total of from 10 to 20% by weight of P2O.

5. A mixture as claimed in any one of the preceding claims comprising from 41 to 55% by weight of superphosphate.

6. A mixture as claimed in any one of the preceding claims which contains less than 2% by weight of water based on the total dry weight of the mixture.

7. A mixture substantialiy as hercinbefore described.

8. A mixture substantially as hereinbefore described in the Example.

9. A method for preparing a mixture as claimed in any of the preceding claims which comprises dry mixing the ingredients.

10. A method as claimed in claim 9 wherein particles of slag and superphosphate having sizes greater than that desired are milled together until the particles have the desired size.

11. A method as claimed in claim 10 wherein milling is done in a ball or tube mill.

12. A method as claimed in claim 9 substantially as hereinbefore described.

13. A method substantially as hereinbefore described in the Example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. superphosphate (26% P2Os, 5% H2O and of particle size 10 to 3,000 micrometres) were fed to a tube mill in a weight ratio of 11: 9. The mixture was crushed to an overall particle size in the range 1 to 100 micrometres, for some 20 minutes. The temperature attained during crushing was 65"C. The product from the mill crusher was a free flowing material with a pH of more than 10 (as measured for a 10% slurry in distilled water using glass electrodes), having a total P20 content of 13.3 ó of which 95 '. of the P2O, was citric acid soluble. WHAT WE CLAIM IS:-

1. A mixture comprising slag containing less than 8% by weight of P2O and single superphosphate in weight proportions of from more than 0.8:1 to less than 1.5:1 respectively.

2. A mixture as claimed in claim 1 wherein the slag is LD slag.

3. A mixture as claimed in either of claims 1 or 2 wherein the slag and superphosphate both have a mean particle size of less than 1,000 micrometers.

4. A mixture as claimed in any one of the preceding claims which contains a total of from 10 to 20% by weight of P2O.

5. A mixture as claimed in any one of the preceding claims comprising from 41 to 55% by weight of superphosphate.

6. A mixture as claimed in any one of the preceding claims which contains less than 2% by weight of water based on the total dry weight of the mixture.

7. A mixture substantialiy as hercinbefore described.

8. A mixture substantially as hereinbefore described in the Example.

9. A method for preparing a mixture as claimed in any of the preceding claims which comprises dry mixing the ingredients.

10. A method as claimed in claim 9 wherein particles of slag and superphosphate having sizes greater than that desired are milled together until the particles have the desired size.

11. A method as claimed in claim 10 wherein milling is done in a ball or tube mill.

12. A method as claimed in claim 9 substantially as hereinbefore described.

13. A method substantially as hereinbefore described in the Example.