About The Subject

Mechanical unit operations are fundamental processes in chemical engineering that involve the physical manipulation of materials to achieve desired separations, transformations, or reactions. These operations encompass a variety of techniques, including filtration, crystallization, size reduction, and mixing, each playing a critical role in the overall efficiency of chemical production. By leveraging principles of mechanics and material science, engineers design and optimize equipment and processes to enhance yield, improve quality, and reduce energy consumption. Understanding mechanical unit operations is essential for developing robust systems that can handle diverse materials and conditions, ensuring both reliability and sustainability in various industries such as food processing, pharmaceuticals, and petrochemicals.

Course Objectives

• Identify the important physical mechanisms occurring in processes involving particles.
• Discuss unit operations and its role in chemical industries and characterization of particulate solids.
• Understand size reduction, particle dynamics, separation of particles and handling
• Understand mixing of solids, selection and working of different industrial mixers
• Formulate and solve mathematical descriptions of settling, filtration and fluidization processes

Course Syllabus

• Particle characterization: Relevance of fluid and particle mechanics, Measurement of particle size, Particle size distribution, Mean particle size, Relationship among shape factors and particle dimensions, Particles in mixtures
• Particulate solids in bulk:General characteristics, Agglomeration, Resistance to shear and tensile forces, Angles of repose and of friction, Flow of solids in hoppers, Flow of solids through orifices
• Screen analysis: Standard screen series, industrial screening equipment, calculation of effectiveness of screening
• Storage of Solids: Bin and silos storage, Pressures in bins and silos, Flow out of bins
• Conveyors: conveying equipment (Screw conveyors, Belt Conveyors, Chain and Flight conveyors, bucket elevators, pneumatic conveyors), Design calculation of Belt Conveyors
• Mixing: Necessity of mixing and agitation in chemical industries,agitator selection, Calculation of power consumption in agitation, Mixers for cohesive solids, mixing equipment of free flowing solids, calculation of power requirement and mixing index of solid mixers
• Size reduction and enlargement: Size reduction equipment,Crushing efficiency, Empirical relationships, Open circuit and closed circuit grinding, Nucleation and growth of particles
• Separation of suspended solid particles from fluids: Froth flotation, magnetic separator, fiber and fabric filter, electrostatic precipitators, cyclone separator, hydro cyclone, Mineral jig, scrubbers, centrifuges, centrifugal clarifier
• Motion of particles through fluids: Drag force, Drag coefficients, skin and form drag, Stoke's law, Newton's law, Criterion for settling regime, Free and hindered settling
• Flow through packed beds: Void fraction, superficial velocity, channeling, Ergun equation and its derivation, Kozeny Carman equation, Burke-Plummer equation , Darcy's law and permeability, characteristics of fluidized systems, minimum fluidization velocity, types of fluidization, applications of fluidization technique, spouted beds and fixed bed
• Filtration: Classification of filtration, Filter media and filter aids, filtration equipments, pressure drop through filter cake, filter medium resistance, specific cake resistance, continuous filtration, washing and dewatering of filter cakes, Centrifugal filtration
• Membrane filtration: Classification, Nature of synthetic membranes, Cross flow microfiltration, Ultrafiltration, Reverse osmosis, Electro dialysis, Dialysis, Membrane Fouling
• Gravity Settling Processes: Gravity classifier, sorting classifier, Clarifiers and thickeners, sedimentation, kynch theory of sedimentation, Design of thickeners

Real-life applications

• Separation Processes:
  • Filtration: Used in water treatment plants to remove impurities.
  • Centrifugation: Employed in dairy industries to separate cream from milk and in pharmaceuticals to separate cellular components.
• Mixing:
  • Food Industry: Mixing ingredients for baked goods or sauces to ensure uniformity.
  • Chemical Engineering: Combining reactants in reactors to promote chemical reactions.
• Size Reduction:
  • Pharmaceuticals: Milling active ingredients to achieve the desired particle size for drug formulations.
  • Mining: Crushing and grinding ores to extract valuable minerals.
• Material Handling:
  • Logistics: Use of conveyors and automated systems to move products in warehouses and manufacturing facilities.
  • Construction: Handling bulk materials like cement, gravel, and aggregates during building projects.
• Heat Transfer:
  • HVAC Systems: Managing temperature and air quality in residential and commercial buildings.
  • Food Processing: Pasteurization and sterilization processes to ensure food safety.
• Fluid Flow:
  • Pipelines: Transporting oil, gas, and water through systems designed to manage flow rates and pressure.
  • Chemical Manufacturing: Designing reactors and columns to facilitate efficient flow of reactants.
• Drying:
  • Agriculture: Drying grains to prevent spoilage and extend shelf life.
  • Pharmaceuticals: Drying active ingredients to prepare for tablet formulation.
• Agitation:
  • Bioreactors: Mixing in fermentation processes to ensure proper nutrient distribution for microbial growth.
  • Cosmetics: Creating emulsions for creams and lotions.
• Crystallization:
  • Sugar Industry: Purifying sugar by crystallizing it from syrup.
  • Pharmaceuticals: Producing drug crystals to achieve specific solubility and bioavailability.
• Separation by Sedimentation:
  • Wastewater Treatment: Allowing solids to settle for efficient sludge removal.
  • Mining: Separating valuable minerals from waste through settling techniques.

Recommended books for mechanical unit operations

Here are some books that you may refer for this subject, they are easy to understand, based on concepts. Get the book PDF on one click, for FREE!

• Unit Operations of Chemical Engineering - Fifth Edition - J. C. Smith, Peter Harriot, Warren McCabe
• R C - Vol 2 - J. F. Richardson, J. H. Harker, J. R. Backhurst