Question

How is superphosphate of lime manufactured?

Short answer

Answer: The manufacturing process of superphosphate of lime involves grinding rock phosphate, reacting it with sulfuric acid to form a slurry, granulating or crystallizing the mixture, drying, cooling, and finally packaging or storage. These steps produce single superphosphate, a phosphorus-rich inorganic fertilizer used to promote plant growth.

Step-by-step solution

1. Understanding Superphosphate of Lime

Superphosphate of lime, also known as Single Superphosphate (SSP), is a widely used inorganic fertilizer that provides phosphorous to plants. It is made by reacting sulfuric acid with rock phosphate, which is a naturally occurring source of calcium phosphate.

2. Main Ingredients in Manufacturing Superphosphate of Lime

The main ingredients used in manufacturing superphosphate of lime are: 1. Rock phosphate (Ca3(PO4)2) – a source of calcium phosphate 2. Sulfuric acid (H2SO4) – used to convert phosphate rock into soluble phosphates.

3. Manufacturing Process of Superphosphate of Lime

The manufacturing process of superphosphate of lime consists of the following steps: Step 1: Grinding of Rock Phosphate Rock phosphate is ground into a fine powder using grinding mills. This increases the surface area to help in the chemical reaction with sulfuric acid in the next step. Step 2: Mixing and Reacting Rock Phosphate with Sulfuric Acid The ground rock phosphate powder is mixed with concentrated sulfuric acid (about 98% purity) in a mixing chamber called a den. The reaction of rock phosphate and sulfuric acid produces single superphosphate and calcium sulfate (gypsum) as a by-product. The chemical reaction can be represented as follows: Ca3(PO4)2 + 2H2SO4 → Ca(H2PO4)2 + 2CaSO4 Step 3: Formation of Superphosphate Slurry As a result of this reaction, a slurry mixture of single superphosphate and calcium sulfate is formed. Step 4: Granulation/Crystallization The slurry mixture is then moved to a granulation drum or crystallizer where the single superphosphate solidifies and granules or crystals are formed. The size and shape of the granules depend on the equipment used and the conditions of the process. Step 5: Drying and Cooling Superphosphate is then dried to remove excess water and moisture. The dried product is also cooled before being sent for storage or packaging. Step 6: Storage and Packaging The final product is stored either in bulk storage or bagged in smaller quantities for distribution. The packaged fertilizer is ready to be distributed and used in agriculture. In conclusion, superphosphate of lime is manufactured through a series of steps that involve grinding rock phosphate, reacting it with sulfuric acid, forming a slurry, granulating or crystallizing, drying, cooling, and storing or packaging. This fertilizer is used to provide phosphorous, a crucial nutrient for plant growth.