Chemical Engineering Tutorials

Absorption: A mass transfer operation where a gas mixture is contacted with a liquid solvent to selectively dissolve one or more components.
Activation Energy (Ea): The minimum amount of energy required to initiate a chemical reaction.
Activity Coefficient: A factor used in thermodynamics to account for deviations from ideal behaviour in a mixture.
Adsorption: The adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a solid surface.
Agglomeration: A process where small particles are gathered and bound together into larger, stable clusters or granules.
Amorphous Polymer: A polymer structure where the molecular chains are arranged randomly without a defined crystalline structure.
Angle of Repose: The steepest angle of descent or dip relative to the horizontal plane to which a bulk granular material can be piled without slumping.
Anode: The electrode where oxidation occurs (electrons are lost) in an electrochemical or galvanic cell.
Arrhenius Equation: A formula that expresses the temperature dependence of reaction rates: k = Ae^(-Ea/RT).
Autoignition Temperature: The lowest temperature at which a substance will spontaneously ignite in a normal atmosphere without an external spark.
Azeotrope: A mixture of liquids that maintains a constant boiling point and composition throughout distillation.
Batch Reactor: A reactor where all reactants are loaded at once, mixed, and reacted over time without continuous inflow or outflow.
Biochemical Oxygen Demand (BOD): The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a water sample.
Bioreactor: A vessel or system that supports a biologically active environment for growing organisms like bacteria or yeast.
Bioremediation: The use of naturally occurring or deliberately introduced microorganisms to consume and break down environmental pollutants.
Blowdown: The intentional removal of a portion of water from a boiler or cooling tower to limit the buildup of dissolved solids.
Blower: A turbomachine that moves large volumes of gas at a relatively low pressure rise through a piping system.
Boundary Layer: The thin layer of fluid immediate to a bounding surface where viscous forces are significant.
Breakthrough Curve: A plot showing the effluent concentration of an adsorption column over time, indicating when the bed becomes saturated.
By-product: A secondary or incidental product made during the manufacture of a primary product.
Cake Filtration: A filtration mechanism where solid particles accumulate on top of the filter medium, forming a thick "cake" layer.
Capital Expenditure (CapEx): The money spent on purchasing, upgrading, and installing physical assets like machinery, reactors, or plants.
Carbon Capture and Storage (CCS): The process of trapping waste carbon dioxide from large point sources and depositing it where it will not enter the atmosphere.
Cascade Control: A control strategy that uses two concentric loops (inner and outer) to eliminate disturbances closer to their source.
Catalyst Deactivation: The loss over time of catalytic activity or selectivity due to fouling, poisoning, or sintering.
Catalyst: A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
Cathode: The electrode where reduction occurs (electrons are gained) in an electrochemical or galvanic cell.
Cavitation Index: A dimensionless number used to characterize the likelihood of cavitation occurring within a pump or control valve.
Cavitation: The formation of vapour bubbles within a liquid followed by their sudden collapse, causing mechanical erosion in pumps.
Cell Immobilisation: The restriction of cell mobility in a fixed space to improve bioreactor stability and allow continuous operation.
Chemical Kinetics: The study of chemical reaction rates and the factors that influence them.
Chemical Oxygen Demand (COD): An indicative measure of the amount of oxygen that can be consumed by reactions in a measured volume of water.
Chemical Potential: The change in Gibbs free energy when an additional mole of a substance is added to a system at constant temperature and pressure.
Chemostat: A bioreactor to which fresh medium is continuously added while culture liquid is continuously removed to maintain a constant volume.
Clarifier: A settling tank built with mechanical means for the continuous removal of solids deposited by sedimentation.
Coagulation: The destabilization of colloidal particles by the addition of a chemical reagent (coagulant) that neutralizes electrical charges.
Comminution: The mechanical reduction of solid materials into smaller particle sizes through crushing, grinding, or milling.
Composite Material: A material made from two or more constituent materials with significantly different physical or chemical properties.
Compressor: A mechanical device that increases the pressure of a gas by reducing its volume.
Condenser: A heat exchanger used to cool and condense vapor streams back into liquid phases.
Constitutive Equation: A relation between physical quantities that is specific to a material or substance (e.g., Ohm's law, ideal gas law).
Continuous Stirred-Tank Reactor (CSTR): A continuous reactor where reactants are thoroughly mixed, ensuring uniform composition and temperature throughout.
Control Valve: A valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller.
Convergence: The property of a numerical iteration method to approach a stable, true solution as calculations progress.
Conversion: The fraction of a specific limiting reactant that is converted into products during a chemical reaction.
Cooling Tower: A heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature.
Copolymer: A polymer made by polymerizing more than one type of monomer species together.
Corrosion Allowance: Extra material thickness added to the design of a vessel or pipe to compensate for expected metal loss over its operating lifespan.
Critical Point: The endpoint of a phase equilibrium curve where the liquid and gas phases of a substance become indistinguishable.
Cross-linking: The formation of chemical bonds that link one polymer chain to another, increasing material stiffness and thermal stability.
Crystallisation: A separation technique where a solid phase precipitates out of a liquid solution to form highly structured crystals.
Crystalline Polymer: A polymer structure featuring highly ordered, packed molecular chains, resulting in higher density and melting points.
Cyclone Separator: A device that utilizes centrifugal force to separate solid particles from a gas or liquid stream.
Damköhler Number (Da): A dimensionless number that relates the chemical reaction rate to the mass transport rate.
Dead Time: The time delay between when a change is made to a process and when the first measurable response is observed.
Desalination: Any process that removes salt and other minerals from saline water to generate fresh water.
Desorption: The phenomenon where a substance is released from or through a surface (the reverse of adsorption or absorption).
Degrees of Freedom (DoF): The number of independent variables that must be specified to completely define a chemical process system.
Dialysis: A separation process that utilizes a semipermeable membrane to separate solutes based on differences in diffusion rates.
Diffusivity: A proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species.
Dimensional Analysis: A mathematical tool used to reduce physical problems to minimal dimensionless parameters (e.g., Buckingham Pi Theorem).
Distillation: A process that separates components of a liquid mixture based on differences in their boiling points (volatilities).
Distributed Parameter System: A system where process variables vary with respect to spatial position as well as time (modeled with PDEs).
Downstream Processing: The stages of a bioprocess where target products are recovered, separated, and purified from a bioreactor broth.
Drying: A mass transfer process resulting in the removal of water or another solvent by evaporation from a solid, semi-solid or liquid.
Dynamic Simulation: Computer modeling that mimics the time-dependent behavior of a chemical process during startups, shutdowns, or upsets.
Elastomer: A polymer with viscoelasticity (both viscosity and elasticity) and very weak intermolecular forces, allowing it to stretch and return to shape.
Electrolysis: A technique that uses direct electric current to drive an otherwise non-spontaneous chemical reaction.
Endothermic Reaction: A chemical reaction that requires or absorbs thermal energy from its surroundings.
Energy Balance: An application of the conservation of energy to a system (Energy In = Energy Out + Accumulation).
Enthalpy (H): A thermodynamic property equal to the internal energy of a system plus the product of its pressure and volume.
Entropy (S): A measure of the thermal energy of a system per unit temperature that is unavailable for doing useful work; a measure of disorder.
Enzyme: A biological catalyst, typically a protein, that accelerates specific biochemical reactions.
Equation of State (EOS): A thermodynamic equation relating state variables (Pressure, Volume, Temperature) like the Ideal Gas Law or Peng-Robinson equation.
Evaporator: A device used to turn the liquid form of a chemical substance into its gaseous or vapor form, often to concentrate a solution.
Exothermic Reaction: A chemical reaction that releases energy by light or heat to its surroundings.
Extraction: Separating a substance from a liquid or solid mixture by contacting it with a solvent in which the target component is preferentially soluble.
Faraday's Laws of Electrolysis: Quantitative relationships asserting that the mass of a substance altered at an electrode is proportional to the electric charge passed.
Feedback Control: A control system loops that measures a process variable, compares it to a setpoint, and adjusts an actuator to minimize error.
Feedforward Control: A control system that measures disturbances before they affect the process and takes preemptive corrective action.
Fermentation: An anaerobic metabolic process that converts sugars to acids, gases, or alcohols using microorganisms.
Fick's Laws: Equations that describe chemical diffusion and define the relationship between flux and concentration gradients.
Filtration: The mechanical separation of solids from a fluid using a porous medium that retains the solids.
Flash Point: The lowest temperature at which a liquid can vaporize to form an ignitable mixture in air.
Flocculation: A wastewater treatment process where colloids come out of suspension in the form of floc or flake, either spontaneously or due to a clarifying agent.
Flooding: An undesirable operational limit in distillation or absorption columns where high fluid rates cause liquid to accumulate and fill the column.
Fluid Mechanics: The study of fluids (liquids and gases) at rest or in motion and their interactions with boundaries.
Fluidisation: A process where a bed of solid particles is transformed into a fluid-like state by forcing a gas or liquid upward through it.
Fluidised Bed: A physical phenomenon occurring when a solid particulate substance is placed under appropriate conditions to cause it to behave like a fluid.
Fouling Factor: A thermal resistance value added to account for the accumulation of unwanted material (like scale) on heat transfer surfaces.
Fourier's Law: A law stating that the time rate of heat transfer through a material is proportional to the negative gradient in the temperature.
Fuel Cell: An electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent into electricity.
Fugacity: An effective pressure used in real gas equilibrium calculations to replace the true mechanical pressure.
Fugitive Emissions: Unintentional emissions of gases or vapors from pressurized equipment, such as leaks from valves, pumps, or flanges.
Galvanic Corrosion: An electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, more noble metal.
Gelation: The formation of a continuous, three-dimensional polymer network (a gel) from a liquid polymer solution.
Gibbs Free Energy (G): A thermodynamic potential that can be used to calculate the maximum reversible work that may be performed by a thermodynamic system at a constant temperature and pressure.
Glass Transition Temperature (Tg): The temperature range where an amorphous polymer changes from a hard, rigid, glassy state to a flexible, rubbery state.
Green Engineering: The design, commercialization, and use of processes and products that minimize pollution and risk to human health.
Greenhouse Gas (GHG): Gas species in an atmosphere that absorb and emit radiation within the thermal infrared range, contributing to global warming.
Hazop (Hazard and Operability Study): A structured and systematic examination of a planned or existing process to identify risks to personnel or equipment.
Header: A main pipe or manifold that distributes fluid to, or collects fluid from, several smaller parallel branch pipes.
Heat Exchanger: A device built for efficient heat transfer from one fluid medium to another.
Height Equivalent to a Theoretical Plate (HETP): The vertical height of packing in a column that achieves the same separation as one theoretical tray.
HTU (Height of a Transfer Unit): A physical dimension that characterizes the mass transfer efficiency of a specific packing material under set flow rates.
Hydraulic Diameter: A commonly used term when handling flow in non-circular tubes, channels, and particle beds.
Inoculum: A small volume of microorganisms introduced into a bioreactor to initiate population growth and fermentation.
Instrument Air: Clean, dry, oil-free compressed air used to actuate pneumatic control valves and instruments safely.
Interlock: A safety mechanism or system that automatically prevents a process operation from occurring unless specific safety conditions are satisfied.
Laminar Flow: Smooth, parallel layers of fluid sliding past one another with minimal mixing (low Reynolds number).
Latent Heat: The energy absorbed or released by a substance during a phase change (e.g., melting, boiling) without changing its temperature.
Leaching: The process of extracting a soluble constituent from a solid matrix using a liquid solvent.
Limiting Current Density: The maximum current density achievable in an electrochemical process due to mass transport constraints of reactants.
Linear Programming (LP): A mathematical optimization method for a linear objective function, subject to linear equality and inequality constraints.
Life Cycle Assessment (LCA): A methodology for assessing environmental impacts associated with all the stages of a product's life-cycle.
Log Mean Temperature Difference (LMTD): A calculated average temperature driving force used to analyze heat transfer rates in heat exchangers.
Lower Explosive Limit (LEL): The lowest concentration of a gas or vapor in air capable of producing a flash of fire in the presence of an ignition source.
Lumped Parameter System: A system where spatial variations are ignored, and variables depend only on time (modeled with ODEs).
Lytic Cycle: A viral replication cycle that results in the destruction (lysis) of the host cell wall to release new viral particles.
Manipulated Variable (MV): The variable that is adjusted by a controller to maintain the process variable at the setpoint (e.g., valve opening).
Material Balance: An application of the conservation of mass to the analysis of physical systems (Input = Output + Accumulation).
Membrane Separation: Techniques (like reverse osmosis or ultrafiltration) that use semi-permeable barriers to selectively separate components.
Metabolic Engineering: The optimization of genetic and regulatory processes within cells to increase the production of specific substances.
Michaelis-Menten Kinetics: A model describing the rate of enzymatic reactions by relating reaction velocity to substrate concentration.
Monomer: A small molecule that can react chemically with other molecules to form a long polymer chain.
Monte Carlo Simulation: A computerized mathematical technique that allows engineers to account for risk and variability in quantitative analysis.
Murphree Efficiency: A measure of column tray performance, defined as the actual change in vapor composition divided by the ideal equilibrium change.
Net Positive Suction Head Available (NPSHa): The total fluid pressure experienced at the pump suction nozzle, calculated based on system design.
Net Positive Suction Head Required (NPSHr): The minimum suction pressure required by a pump manufacturer to prevent internal cavitation.
Newton's Law of Cooling: States that the rate of heat loss of a body is directly proportional to the difference in temperatures between the body and its surroundings.
Nonlinear Programming (NLP): An optimization method where the objective function or constraints contain nonlinear equations.
Non-Newtonian Fluid: A fluid whose viscosity changes under applied shear stress or force (e.g., cornstarch and water, paint).
NTU (Number of Transfer Units): A dimensionless measure of the difficulty of a mass transfer separation task.
Nusselt Number (Nu): The ratio of convective to conductive heat transfer across a boundary.
Operational Expenditure (OpEx): The ongoing, day-to-day costs of running a plant (e.g., raw materials, utilities, labor).
Optimization: The act of adjusting process variables to find the most efficient, cost-effective, or highest-yielding operating conditions.
Overpotential: The potential difference (voltage) between a cell's thermodynamically determined potential and its actual experimental potential under current flow.
Packed Bed: A hollow tube, pipe, or other vessel filled with packing materials designed to improve contact between different phases.
Passivation: The formation of a light, unreactive film (such as an oxide layer) on a metal surface that protects it against subsequent corrosion.
Pervaporation: A processing method for the separation of liquid mixtures by partial vaporization through a dense membrane.
Phase Equilibrium: A state where multiple phases (solid, liquid, gas) coexist without any net change over time.
PID Controller: A proportional-integral-derivative controller; a control loop feedback mechanism widely used in industrial control systems.
Piping and Instrumentation Diagram (P&ID): A highly detailed diagram showing the piping, vessels, control instrumentation, and safety interlocks.
Plug Flow Reactor (PFR): A continuous, tubular reactor where fluid passes through linearly without mixing with the fluid ahead or behind it.
Pneumatic Conveying: The movement of bulk solid materials through a pipeline using a stream of high-velocity air or gas.
Polydispersity Index (PDI): A measure of the distribution of molecular mass in a given polymer sample.
Polymerisation: A chemical process that combines several small monomer molecules to form a large chainlike network (a polymer).
Prandtl Number (Pr): A dimensionless number approximating the ratio of momentum diffusivity to thermal diffusivity.
Priming: The act of filling a pump casing and suction pipe with liquid to eliminate trapped air before starting operation.
Process Flow Diagram (PFD): A schematic drawing showing the major equipment and chemical streams within a chemical plant.
Process Variable (PV): The specific dynamic condition of a process that is being monitored or controlled (e.g., current flow rate).
Purge Stream: A bleed stream used to remove accumulated inert materials or impurities from a closed recycle loop.
Reboiler: A heat exchanger used to generate vapor feed for the bottom of an industrial distillation column.
Recycle Stream: A process stream that returns unreacted materials or energy from downstream equipment back to upstream units to maximize efficiency.
Reflux: The portion of an overhead distillation column product that is returned to the top of the column to improve separation efficiency.
Regression Analysis: A statistical process for estimating the relationships among variables, often used to fit empirical engineering data.
Relief Valve: A safety device designed to open automatically and vent excess pressure from a vessel to protect it from exploding.
Residence Time: The average amount of time a particle or fluid element spends inside a reactor vessel.
Reynolds Number (Re): A dimensionless quantity used to help predict fluid flow patterns (laminar vs. turbulent).
Runaway Reaction: A dangerous situation where an exothermic reaction accelerates out of control due to insufficient heat removal.
Scale-up: The process of converting a laboratory-scale chemical process into a fully functioning large-scale commercial factory.
Schmidt Number (Sc): A dimensionless number expressing the ratio of momentum diffusivity to mass diffusivity.
Scrubber: An air pollution control device used to remove particulates or gases (such as acid gases) from industrial exhaust streams.
Sedimentation: The tendency for particles in suspension to settle out of the fluid in which they are entrained due to gravity.
Selectivity Coeffecient: In extraction, the ratio of the distribution coefficient of the solute to the distribution coefficient of the diluent.
Selectivity: The ratio of the desired product formed to the undesired products formed in a parallel or competitive reaction network.
Sensible Heat: Thermal energy whose transfer to a system results in a change of temperature.
Sensitivity Analysis: The study of how the uncertainty in the output of a process model can be apportioned to different sources of uncertainty in its inputs.
Setpoint: The desired or target value for an essential process variable (e.g., target temperature or pressure).
Shear Thickening: An effect where a non-Newtonian fluid becomes more viscous (thickens) when subjected to shear stress.
Shear Thinning: An effect where a non-Newtonian fluid becomes less viscous (flows easier) when subjected to shear stress.
Shell and Tube Heat Exchanger: The most common design, consisting of a series of tubes inside a cylindrical shell through which two fluids exchange heat.
Sherwood Number (Sh): A dimensionless number representing the ratio of convective mass transfer to diffusive mass transport.
Sintering: The process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction.
Slurry: A semi-liquid mixture composed of insoluble solid particles suspended in a liquid medium.
Solvent Extraction: A method to separate compounds based on their relative solubilities in two different immiscible liquids.
Space Velocity: The volumetric flow rate of reactants divided by the reactor volume, indicating how many reactor volumes of feed can be processed in a unit of time.
Space-Time: The time necessary to process a volume of reactor feed equal to the reactor volume.
Sphericity: A dimensionless measure of how closely the shape of a solid particle resembles a perfect sphere.
Steady State: A condition in which all variables of a system remain constant with respect to time.
Steam Trap: An automatic valve that filters out condensed steam (condensate) and non-condensable gases without letting live steam escape.
Stochiometry: The calculation of quantitative relationships of the reactants and products in a balanced chemical reaction.
Stress Corrosion Cracking (SCC): The growth of crack formation in a corrosive environment, which can lead to sudden failure of normally ductile metals.
Stripping: A physical separation process where one or more components are removed from a liquid stream by a vapor or gas stream.
Substrate: The specific chemical or nutrient consumed by a microorganism or enzyme to produce a desired product.
Supercritical Fluid: Any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.
Supercritical Extraction: A separation process utilizing a supercritical fluid (like CO2) as a solvent to extract specific compounds.
Thermoplastic: A plastic material that becomes pliable or moldable above a specific temperature and solidifies upon cooling reversibly.
Thermoset: A polymer that irreversibly cures via heat or chemical reaction, creating a rigid network that cannot be remelted.
Transient State: A state in which process variables are changing over time (unsteady state).
Transmitter: A device that senses a process variable via a sensor and converts it into a standard signal (e.g., 4-20 mA) sent to a control system.
Turbidostat: A continuous bioreactor that uses a photoelectric device to measure culture turbidity and automatically adjust feed rate.
Turbulent Flow: Chaotic, fluid motion characterized by eddies, vortices, and rapid mixing (high Reynolds number).
Turndown Ratio: The ratio of the maximum design flow capacity to the minimum controllable flow capacity of a process unit or valve.
Unit Operations: Basic physical steps in a chemical process involving physical changes, such as distillation, evaporation, or filtration.
Unit Processes: Chemical reactions taking place in industrial settings, such as oxidation, hydrogenation, or nitration.
Upper Explosive Limit (UEL): The highest concentration of a gas or vapor in air that will burn or explode when an ignition source is present.
Upstream Processing: The initial stages of a bioprocess including strain selection, media preparation, and cell growth inoculation.
Utility: Ancillary services needed to operate a chemical plant, such as cooling water, steam, electricity, or instrument air.
Viscoelasticity: The property of materials that exhibit both viscous and elastic characteristics when undergoing deformation.
Viscosity: A measure of a fluid's resistance to gradual deformation by shear or tensile stress (thickness).
Voidage: The fraction of total volume occupied by open spaces (voids) between particles in a packed or fluidized bed.
Water Hammer: A pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly (e.g., fast valve closure).
Weeping: An undesirable condition in tray columns where gas pressure is too low, causing liquid to leak straight down through the tray perforations.
Yield Stress: The minimum stress level at which a material ceases to behave elastically and begins to permanently deform plastically.
Yield: The amount of desired product formed relative to the amount of reactant consumed.

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