Q1: Unit operation involved in the prilling of urea is

ANS:D - both (b) and (c)

Sure, let's explain both drying and crystallization:

1. Drying: Drying is a unit operation used to remove moisture or solvent from a solid, liquid, or gas by evaporation or other means. It aims to reduce the moisture content to a desired level for further processing, storage, or use. Drying is commonly used in various industries such as food processing, pharmaceuticals, chemicals, and agriculture. The process of drying typically involves applying heat to the material to increase the rate of evaporation and remove moisture. The moisture evaporates into the surrounding air or is removed using a flow of dry air or other gases. Drying can be achieved through different methods such as air drying, vacuum drying, freeze drying, spray drying, or drum drying, depending on the nature of the material and the specific requirements of the process. Drying is important to prevent microbial growth, extend shelf life, improve product quality, and facilitate handling and transportation of materials. It is crucial in various applications such as drying of agricultural products (e.g., grains, fruits, vegetables), drying of pharmaceuticals and chemicals, drying of paper and textiles, and drying of industrial products.
2. Crystallization: Crystallization is a unit operation used to form solid crystals from a solution, melt, or gas phase. It involves the process of nucleation and growth of crystals from a supersaturated solution or a supercooled melt. Crystallization is widely used in industries such as chemicals, pharmaceuticals, food processing, and materials science for purification, separation, and production of crystalline products. The process of crystallization typically starts with the formation of tiny crystal nuclei in the solution or melt, followed by the growth of these nuclei into larger crystals. The conditions such as temperature, pressure, solvent composition, and rate of cooling or evaporation are carefully controlled to achieve the desired crystal size, shape, and purity. Crystallization can be carried out through various methods such as cooling crystallization, evaporation crystallization, antisolvent crystallization, and reactive crystallization, depending on the properties of the solute and solvent and the specific requirements of the process. Crystallization is used to purify substances, separate components from mixtures, produce high-value products with specific crystal forms, and control particle size and distribution. It is essential in applications such as production of pharmaceuticals, fine chemicals, fertilizers, food additives, and electronic materials.