Calcium Ammonium Nitrate (CAN) – A nitrogenous fertilizer derived from ammonium nitrate which contains a minimum of 20% calcium material (e.g., calcite or dolomite) and a maximum of 27% nitrogen. The material can be substituted with calcium sulphate (gypsum). It is a source of water-soluble nitrogen but not a source of water-soluble calcium.
Calcium Ammonium Nitrate (CAN) is created by adding powered limestone or calcium nitrate to ammonium nitrate. It is commonly sold as granular or prilled product in various sizes (SGN) as white to pale yellow in colour. CAN is hygroscopic – avoid extended storage, particularly in humid environments.
The advantage of using CAN is that the presence of calcium (roughly 8%) adds an agronomic advantage, but also stabilizes the product, making it a safer alternative to conventional ammonium nitrate. Also, the combination of ammonium and nitrate nitrogen is readily available for crop uptake.
First, ammonium nitrate solution is prepared by reacting preheated ammonia with nitric acid in a neutralizer. The heat of reaction is utilized for evaporation and 80–83% ammonium nitrate solution is obtained. This concentrated solution is further concentrated to obtain 92–94% solution in a vacuum concentrator.
Concentrated ammonium nitrate solution is then sprayed into the granulator along with a regulated quantity of limestone powder and the recycle fines from the screens. The hot granules are dried in a rotary drier by hot air, screened and cooled in coolers to obtain the product.
Most calcium ammonium nitrate is used as a fertilizer. Fertilizer grade CAN contains roughly 8% calcium and 21-27% nitrogen. CAN is preferred for use on acid soils, as it acidifies soil less than many common nitrogen fertilizers. The application could be as stand-alone product or more commonly in blends with varying combinations of N, K and micronutrients, typically in specialty crops. The simplest way is broadcast (surface-applied).
Calcium ammonium nitrate has been used in improvised explosives. The CAN is not used directly, but instead is first converted to ammonium nitrate.