The caking of granular fertilizers: An investigation on a laboratory scale

Abstract

Preliminary consideration suggested a technique for studying the caking of granular fertilizers on a laboratory scale similar to that used in soil mechanics. An apparatus and technique were devised, and details of these are given. Time of storage of the fertilizer is found to be an important factor, and caking is rapid in the first few days. Preliminary investigations on the effect of chemical composition showed setting to be more serious when ammonium sulphate (I), superphosphate (2) and muriate of potash (3) were all present than when only (I) and (2), or (2) and (3) were included. Free acid content seemed to have little effect nor had light ammoniation of the superphosphate. Moisture content is related to caking, which has been reduced to negligible amounts by drying down to less than I% free moisture. Caking increases with the temperature, and this indicates the desirability of cooling. The correlation between the test developed and the results obtained on the large scale is discussed, and is shown to be sufficiently good for the test to be of considerable value.

Caking of onion powder

“…I t has been postulated (Irani et al, 1959) that as the temperature falls, the saturated solutions which are present on the surface undergo crystallization thus binding one particle to another. However, other investigations (Whynes & Dee, 1957;Lazar & Morgan, 1966) have found that caking is rather related to an increase in temperature. Particle size was reported to become a significant factor below 100 p, since small particles tend to adhere (Craik & Miller, 1958;.…”

“…If a material is relatively insoluble in water the effect of water on its caking characteristics is greatly decreased (Irani, Calls & Liu, 1959). Caking was found to be related to moisture content of granular fertilizers and it was greatly reduced by drying to less than 1% moisture content (Whynes & Dee, 1957).…”

Evaluation method for agglomerating properties of granular detergents

“…2) For powders which partially agglomerate because of moisture adsorption, the percentage of powder agglomerated may be measured (13)(14). 3) For powders which have caked completely, the compressive strength necessary to break the cake may be measured (15)(16)(17)(18)(19)(20)(21). 4) IIygroscopicity, which may be related to agglomeration, is measured, for instance, by measuring the critical relative humidity or water vapor pressure in equilibrium with powder (22)(23)(24)(25)(26).…”

Powders: Particle-Particle Interactions

“…Ettle (713) used a penetrometer to detect caking in stored fcrtilizcr. U'hynes and Dee (77) have used a procedure adapted from the study of soil stability. I t measures the crushing strength of a cylinder of the preconditioned powder held in a rubber sleeve.…”