Unit Operations in Chemical Engineering

Explore piping systems and mathematical models that relate pressure drop to flow for liquids, gases, and solids, emphasizing friction, Reynolds number, and energy implications.

Demonstrate how pipes are represented in P&ID symbols and process and instrumentation diagrams, using arrows and lines to show flow direction, and contrast with simpler process flow diagrams.

Identify fittings used to move fluids in pipes, such as elbows, tees, and crosses. Compare valves such as globe, gate, ball, and butterfly, and materials like steel, copper, and PVC.

Discover how to read P&ID symbols for fittings and identify safety valves and pressure meters to support process modeling and human operations in a chemical plant.

Explore fluid metering models for venturi and orifice plates, applying Bernoulli and continuity to relate pressure drops to velocity and area changes, with device-specific pressure drop coefficients.

Explore pipe and instrumentation diagrams and learn common fluid metering symbols, including rotameters, venturi tubes, differential pressure elements, and magnetic flow meters used to measure flow.

Examine how agitation and mixing differ: agitators rotate to create directed motion, while mixing relies on random movement to homogenize contents and promote concentration gradients, mass, and heat transfer.

Explore agitation and mixing in station tanks by examining vessel design, shaft-driven impellers (open, closed, and turbine types), and baffles that enhance blending and process control.

Explore agitation and mixing using P&ID symbols, highlighting tanks, shafts, impellers, jackets for heating or cooling, and various agitator types and mixing concepts.

Explore pumps in momentum operations, including positive displacement and kinetic pumps, to increase pressure and move fluids, explain cavitation, pump curve versus system curve, and pump selection.

Explore kinetic (dynamic) and centrifugal pumps, where impellers transfer work from the suction to the fluid, raising pressure and velocity through centrifugal force.

Explore centrifugal pump models and their energy balance, deriving shaft work from pressure and velocity changes while neglecting height and viscosity in simplified cases.

Understand cavitation in pumps: pressure drops cause bubble formation and impeller damage; keep head pressure above a minimum, often 1.3–1.5 bar, per supplier or calculations.

Fixed system, only flow rate changes; friction rises with flow. Aim for the intersection of system and pump curves, around 70 liters per second.

Explore system curve, showing how head relates to flow rate through height and friction in a pump piping system, and how pipe size and throttling affect friction and pump power.

Explore series and parallel pump arrangements, using system and pump curves to decide when to increase head versus flow; series raises pressure, parallel boosts flow, with cavitation considerations.

Explore piping and instrumentation diagram symbols for compressors, including turbine-driven versus electric drives, and distinguish compressors (gas) from pumps (liquids) in unit operations.

Explore fluidized bed applications, including absorption, combustion, and drying, through distributor plates and air flow that balance forces and maintain fluidization.

Review recommended heat transfer references for unit operations, including McCabe, Smith, and Herriott, Braden’s texts, and the Kurn process heat transfer book, used across the course.

Explore the shell and tube heat exchanger, the most common type, with a large shell housing many tubes, hot and cold fluids, baffles, multiple configurations, and maintenance considerations.

Explore how plate exchangers use metal plates to separate hot and cold fluids for exchanging heat without mixing, and cover design choices, maintenance, cleaning, and plate replacement.

Spiral exchangers deliver high heat exchange efficiency in a compact spherical design with enhanced temperature control. Observe high capital costs and maintenance challenges due to difficult cleaning.

Explore heat exchanger models to size equipment using the overall heat transfer coefficient and area, and compare counterflow and parallel flow with delta temperature and the log mean temperature difference.

Explore heat exchanger and heater symbols used in P&ID diagrams, including generic heat exchangers, shell and tube types, single and multi-pass designs, and flow direction indicators for heating or cooling.

Explore condenser utilities and refrigerants, from cheap cooling water with high specific heat and high boiling point to ammonia and freon-based options that condense heat efficiently.

Learn the P&ID symbol for condensers, why it's drawn upward to indicate condensation, and how the left side represents heating while the right side indicates cooling.

Study evaporators and boilers as high-energy unit operations used to boil materials, focusing on batch processes and the roles of natural convection, falling-film, and rising-film configurations.

Learn about batch evaporator operations in chemical engineering, using closed containers, filling liquids to 5–10%, with flute transfer or direct flame, in food processing where continuous evaporation is not useful.

Explore forced circulation evaporators, where a pump counters flow to cycle liquid. Gas flashed in the separator and liquid is recycled through the heater and tubes.

Utilize a shell-and-tube evaporator with natural convection, where density differences drive high-temperature, low-density fluid upward and low-temperature, high-density liquid downward to boiling.

Explore how a kettle reboiler uses a heating fluid to vaporize liquid in a distillation column, recycle liquid, and maintain vapor-liquid separation for continuous operation.

Explore mass transfer operations, including distillation columns, gas dispersion, and absorption, which separate components between two phases by transferring species into the organic phase or other phases.

Explore two recommended reference books for mass transfer and unit operations in chemical engineering, including Robert E. Crable's mass transfer operations book, available on Amazon and other sites.

Explore sparged vessels and bubble columns where gas bubbles rise through liquid, featuring cascade columns and designs such as perforated plates and static mixers to enhance gas–liquid contact.

Control gas and liquid flow in tray towers to optimize vapor-liquid contact, prevent priming and flooding, and use reflux and trays to separate volatile and nonvolatile components.

Describe how bubble cap trays regulate gas-liquid contact, with caps that lift under vapor flow, prevent liquid backflow, and allow control of gas flow and pressure drop.

Spray towers disperse liquid into gas to remove solid particles via multiple spray areas, stages, and slurry sprays, yielding clean gas with low pressure drop.

Explore how packed towers enhance mass transfer by forcing gas through packing while liquid flows countercurrently, increasing contact time and interaction for efficient separation.

Explore gas-liquid absorption, where a gas component transfers to a liquid for removal, using Henry's law for ideal systems and extending to multi-component cases.

Explain single-stage versus multi-stage gas–liquid absorption using successive equilibrium stages in columns. Show how multiple stages reduce contaminant concentration through staged mass transfer and absorption of volatile components.

Examine absorber columns, or scrubbers, that remove toxic gases by contacting gas with a liquid absorbent, aiming for lower concentrations; compare packed and tray columns and their multistage operations.

Learn how sour gas containing hydrogen sulfide and carbon dioxide is sweetened by absorption with lean amine, using an absorber and stripper to produce clean natural gas.

Learn how a flashing drum uses a pump and heater to set pressure and temperature, assigning composition and separating vapor and liquid streams.

Explore T-xy diagrams for composition versus temperature, using a methanol–ethanol system; show an envelope between 65 and 96 Celsius and the impact of ideal solutions on vapor composition.

Explore how a flash drum, a unit operation, uses pressure and temperature to separate a feed into vapor and liquid streams by volatility and boiling points.

Master binary distillation for two components, detailing stripping and rectifying sections with a boiler and condenser. Apply the McCabe–Thiele method to set feed stage and reflux, including tray efficiency.

Explore models and diagrams for binary distillation, distinguishing rectifying and stripping sections and feed conditions, then determine minimum stages from operating lines with an 85% liquid fraction example.

Study multicomponent distillation in a column with feeds, trays, a temperature profile, condenser, and top liquid LPG and asphalt-bottoms.

Learn how P&ID symbols define distillation and fractionation columns, with a distillation unit shown by a column, condenser, and boiler/reboiler to distinguish total versus partial condensers.

Read ternary diagrams for solvent, extract, and third component to predict final compositions and distributions. Use degrees of freedom to fix temperature and pressure and optimize solvent use.

Explore column equipment for liquid–liquid extraction, highlighting how increased bubble formation and phase contact, aided by baffles and agitators, enhance mass transfer between phase one and phase two.

Learn how mixer-settler units enable liquid-liquid extraction by mixing solvent and polluted electrolyte to form light and heavy phases, with single-stage and multistage cascade separation.

Describe an adsorption column using activated carbon to purify natural gas by removing impurities and moisture, then regenerate the bed with air for a continuous adsorption-desorption cycle.

Explore how adsorption columns differ from distillation columns and absorbers, and how packing with activated carbon drives separation and color transfer from the crude extract.

Explain the purpose of drying in unit operations by removing internal and external moisture from solids, including tobacco, across various dryer types and the concept of moisture separation by mass.

Explain the psychrometric chart at one atmosphere, linking ambient humidity to air properties. Calculate humidity ratio, wet-bulb temperature, entropy, and energy to evaporate water.

Operate batch dryers in closed, noncontinuous-flow chambers, maximizing air movement with turbulent flow for drying. After batch completion, open the exhaust to vent humid air, aiming for a dry interior.

Describe how tunnel dryers move food solids on a conveyor belt while dry air with low relative humidity flows over them, removing moisture to achieve reduced product humidity.

The rotatory dryer rotates trays of solid material, using center-heated warmth to drop and dry solids as hot gases flow through, with burners and leaf lifters guiding the drying process.

Explore crystallisation as the formation of organized solid structures from a solution, clarifying differences from precipitation, drying, and evaporation, and illustrating supersaturation driving crystal growth and filtration.

Explore batch and continuous crystallisation in evaporators, using solvent evaporation to concentrate salts and form crystals, with recycle loops, steam heating, condensation, and multi-stage crystallisers.

Explore reactor engineering within unit operations, covering batch reactors, tank reactors, and nuclear reactors. Learn about typical symbols and reference books for further study.

Explore essential reference books for reaction kinetics and reactor design, including Elements of Chemical Reaction Engineering, Essentials of Chemical Reaction Engineering, and Levenspiel's Chemical Reaction Engineering.

Batch reactors operate in cycles with high conversions, making them suitable for fine chemistry and kinetics considerations, but they pose temperature control, high operating costs, and scaling challenges.

Explore the continuous stirred tank reactor (CSTR): a single inlet, single outlet reactor with perfect mixing, low conversion per volume, and options like jackets or staged tanks to boost conversion.

Explore plug flow reactors in pipes, enabling continuous operation with high conversion per unit volume and low cost, emphasizing one-dimensional flow, concentration and temperature gradients, and role of multiple tubes.

The packed bed reactor enables high conversions per unit volume with a fixed bed catalyst in a continuous gas-phase process, but it faces high operating costs and pressure drops.

Explore process flow diagrams and pipe and instrumentation diagrams, showing major equipment and streams and their connections while omitting minor piping details.

Analyze a process flow diagram of a reactor-catalyst system with distillation column separation, condenser and off gas handling, fuel oil and phenolics streams, and catalyst regeneration with recycle loops.

Explore pipe and instrumentation diagrams (P&IDs), learn symbols and datums, and understand why real plants prefer showing actual piping, valves, and sizes.

Explore piping and instrumentation diagrams in a distillation process with a column, heat exchangers, pumps, vessels, and a recycle stream, guided by control loops, sensors, and valves.

Analyze P&ID diagrams by deducing components from partial information, identifying reactors, columns, pumps, and heat exchangers, and noting that plant designs evolve over time.

Wraps up unit operations in chemical engineering by reviewing momentum, mass transfer, reactors, and separation; explains reading process flow diagrams and pipelines and identifying units like tanks and heat exchangers.

Explore unit operations questions across four pillars—momentum transport in fluids, heat transfer with exchangers and condensers, mass transfer like distillation and extraction, and reactor engineering—plus pump curves and storage tanks.