Term Definition Section
“and” gate The event only happens when all of the input events occur. When we compute the frequency of the event, we multiply the frequencies of all input events. Because all frequencies are smaller than 1, the resulting frequency will be smaller than any of the input frequencies. Hazard Identification
“or” gate The event happens when any of the input events occur. When we compute the frequency of the event, we add the frequencies of all input events. The resulting frequency will be larger than any of the input event frequencies. Hazard Identification
Abiotic depletion potential (ADP) Consumption of nonliving resources, such as fossil fuels, minerals, clay, and peat Life Cycle Assessment
Absolute pressure The absolute pressure is the actual pressure at the point of interest. The absolute pressure is 0 in a vacuum and cannot be negative. Pressure Definition; Absolute & Gauge Pressure
Absolute temperature Absolute temperature is temperature measured with reference to the absolute zero. Temperature
Accident The occurrence of a sequence of events that produce unintended injury, death or property damage An Introduction to Process Safety
Acidification potential (AP) The precursor compounds of acid rain. Life Cycle Assessment
Activation energy The activation energy (Ea) represents the energy needed for the reactants to collide and get to a state such that their bonds can rearrange to form the products. Arrhenius Equation
Amgat’s Law Amgat’s is analogous to Dalton’s law but is applied to the volume of the gas. The partial volume that each gas occupies will add up to the total system volume. Ideal Gas Properties
Antoine equation log10(p∗)=A−B/(T+C), Used to estimate the vapour pressure of a substance at a certain temperature Estimating Vapour Pressure
Arrhenius equation The Arrhenius Equation describes the relationship between the reaction rate and temperature. Arrhenius Equation
Basic design package This document is provided to clients by engineers and may consist of the following: process definition, process control strategy, equipment design, selection and sizing, plant layout, safety review, environment assessment, economic analysis. Project Scoping
Basic engineering The scale of the plant, the draft of the process flow diagram (PFD, we will introduce this later in the course), cost estimation, preliminary schedule, etc. Project Scoping
Basic event A basic initiating fault (component failure) Hazard Identification
Bimolecular reaction Two molecules collide, interact, and undergo some kind of change. It can be two of the same or different molecules. Reaction Mechanisms – Elementary Reactions
Binary mixture A combination of two substances is called a binary mixture. Multicomponent Equilibrium
Block flow diagram (BFD) Flowsheets that break down chemical and biological processes (or any other process) into units representing equipment (unit operations). Block Flow Diagrams
Boundary The boundary is what separates the system from the surroundings. Introduction to Energy Balances
Boundary conditions Boundary conditions are solutions to specific ordinary differential equations at specified conditions. Introduction to Unsteady-state Operations
Bubble point The point (pressure or temperature) at which the first bubble (gas) in a multicomponent system appears. Multicomponent Equilibrium
Capillary connection A fluid flow control connection. Piping and Instrumentation Diagrams (P&IDs)
Capital costs (CC) Cost of designing and construction of the plant. Basic Economic Analysis
Catalysts Catalysts speed up the reactions usually by decreasing the activation energy. Sometimes catalysts can affect frequency factors as well, but the effect of frequency factor is minor in comparison to the decrease of activation energy. Arrhenius Equation
Checklist analysis Using a checklist to suggest common safety issues to assess. It can be combined with what-if technique to enhance that technique. Hazard Identification
Chemical engineering plant cost index A common type of cost index that is used to estimate the overall plant cost (including installation, piping, etc.) over time. Purchased Equipment (PE) Cost
Closed systems Energy, but no mass transfer between system and surroundings Introduction to Energy Balances
Consecutive elementary reactions A set of reactions that proceed through the formation of one or more intermediate(s). Reaction Mechanisms – Elementary Reactions
Consumption Mass and/or energy that is consumed in the system. Introduction to Unsteady-state Operations
Continuous stirred tank reactor (CSTR) CSTRs are reactors with continuous feed and exit streams and some kind of mixer. Separable Differential Equations
Controlled variable The output process variable we compare to the set-point. Process Control
Cost of manufacturing (COM) The total cost associated with making the product. Divided into direct manufacturing costs, fixed manufacturing costs, and general expenses. Costs of Manufacturing
Cost of operating labour The total cost of paying the salary of the operators. Cost of Operating Labour
Cradle-to-gate The scope of life cycle assessment that includes all aspects of a product from raw material extraction to production, but does not include the product’s use or disposal. Life Cycle Assessment
Cradle-to-grave The scope of life cycle assessment that includes all aspects of a product, starting from raw material extraction to the product’s end of life (use and disposal). Life Cycle Assessment
Critical point In a phase diagram, we can observe that the boiling point curve (the line that distinguishes liquid and vapour phases) ends at a point, which is called a critical point. Phase Diagram
Dalton’s Law The total pressure is the sum of partial pressures of the component gases, assuming ideal gas behavior and no chemical reactions between the components. Ideal Gas Properties
Degrees of freedom The number of intensive variables that needs to be specified. Gibb’s Phase Rule
Depreciation The expenses required to build a plant that are written off over time. Calculated based on the purchase value of equipment minus the salvage value and evaluated over a number of years specified. Costs of Manufacturing
Design basis memorandum (DBM) This document contains key information and data related to the project deliverables. Project Scoping
Dew point The point (pressure or temperature) at which the first dewdrop (liquid) in a multicomponent system appears. Multicomponent Equilibrium
Differential pressure cell A differential pressure cell measures the deflection of the membrane and correlates it to change in pressure. Process Control
Direct costs in FCI Costs related to tangible things or products such as process equipment. Plant Capital Cost
Direct manufacturing costs Factors that vary directly with the rate of production. e.g. raw materials, plant operators Costs of Manufacturing
Disturbance variable A variable that we have no control over in the process but affects the material or heat flow of the process. Process Control
Ecological toxicity potential (EcoTP) The potential of biological, chemical or physical toxicity to ecosystems Life Cycle Assessment
Electrical connection An electrical currents control connection. Piping and Instrumentation Diagrams (P&IDs)
Electrical temperature measure Thermocouples or resistance temperature devices measure changes in electrical properties and correlate them to temperature. Electrical temperature measurements are the most commonly used in plants as switching combination of metals can adapt to a wide range of temperatures. Process Control
Elementary reactions The stepwise changes are collectively called the reaction mechanism. Each step of the reaction is called an elementary reaction. The sum of the elementary reactions in the mechanism must give the balanced chemical equation for the overall reaction. Reaction Mechanisms – Elementary Reactions
Elimination Remove the need for harmful materials or choosing other process pathways to eliminate the production of harmful products. An Introduction to Process Safety
End-of-life (EOL) The EOL bar may be negative in life cycle assessment to signify recovery of the material at the end of the product’s life, which reduced the life-cycle impact. Life Cycle Assessment
Endothermic If more energy is absorbed in breaking bonds than released in forming bonds, then the reaction is endothermic. Reactive Energy Balances
Endothermic control loop A temperature control loop for a system that is absorbing thermal energy. Process Control
Environmental fate Where substances will go when released into the environment. Environmental Fate of Contaminants
Equilibrium constants The product of the activities of compounds at equilibrium raised to the stoichiometric coefficient. Reaction Rate Law
Eutrophication potential (EP) The leak of nutrition sources into aquatic systems Life Cycle Assessment
Exothermic If more energy is released in forming bonds than absorbed in breaking bonds, then the reaction is exothermic Reactive Energy Balances
Expansion-based temperature measure Expansion-based thermometers measure fluid expansion and correlate it to temperature. Process Control
Extensive variables Variables that depend on the size of a system. Intensive & Extensive Variables
Extent of hazards The strength or magnitude of the hazard (e.g the area affected by a flood, the strength of an earthquake described by the Richter Scale) Hazard Identification
Failure modes and effect analysis (FMEA) Tabulation of plant equipment, failure modes (how the equipment can fail), and the effects of these failures.
Identify failure modes then analyze the result of these failures individually.
Hazard Identification
FAR Fatal Accident rate: Fatalities per 1000 employee over their working life (10E8 hours of exposure) An Introduction to Process Safety
Fatality rate The fatality rate per person per year An Introduction to Process Safety
Fault-tree analysis Identifies relevant events and potential failure pathways leading to one particular incident. Uses logic diagrams to express relations between initiating events and an incident. It can be implemented for PHA analysis at any stage of a process from design to the end of life Hazard Identification
First Law of Thermodynamics The First Law of Thermodynamics is defined as:
E(system,final) – E(system,initial) = E(system,transferred)When we expand the energy terms for a closed system, we get:
ΔU + ΔEk + ΔEp = Q + W
Introduction to Energy Balances
Fixed capital investment (FCI) Fixed capital investment is the total price to purchase equipment, get it installed and tested. Plant Capital Cost
Fixed manufacturing costs Factors not affected by the level of production, but related to manufacturing. e.g. taxes and insurance Cost of Operating Labour
Float measure A device that measures the length of the line to float, which translates the line length to the liquid level in the tank. Process Control
Flow work Flow work is work done on process fluid (inlet minus outlet). For the work flow in, the surroundings do work on the system, therefore it is positive. For the work flow out, the system does work on the surroundings, therefore it is negative. Introduction to Energy Balances
Formation reaction A reaction in which the compound is formed from its elemental constituents as they would normally occur in nature. Reactive Energy Balances
Frequency factor The frequency factor describes the frequency that molecules collide with the correct orientation to possibly make a chemical reaction. Arrhenius Equation
Functional unit A measure of the function of the studied system. It provides a reference to which the inputs and outputs can be related and enables a comparison of two essentially different systems. Multicomponent Equilibrium
Gate-to-gate The scope of life cycle assessment that includes the manufacturing/production and processing aspects of a product only. Life Cycle Assessment
Gauge pressure Gauge pressure is defined to be the difference between the absolute pressure and atmospheric pressure. Pressure Definition; Absolute & Gauge Pressure
General expenses Management and administrative expenses not related to manufacturing. Plant Capital Cost
Generation Mass and/or energy that is produced in the system. Introduction to Unsteady-state Operations
Gibb’s Phase Rule Gibb’s phase rule is used to determine the number of intensive variables required to fully specify the thermodynamic properties of a system (thermodynamic degrees of freedom). Gibb’s Phase Rule
Global warming potential (GWP) Contribution to global warming caused by the release of gas. Life Cycle Assessment
Goal definition and scoping Identify the LCA’s purpose, the products of the study, and determine the study boundaries. This can include things like what is included and what is not included in the study. Life Cycle Assessment
Green engineering The design, commercialization, and use of processes and products in a way that reduces pollution, promotes sustainability and minimizes risks to human health and the environment without sacrificing economic viability and efficiency. Green Engineering
Gross economic potential (GEP) GEP = Value of Products – Value of Feeds Basic Economic Analysis
Group contribution method Taking common chemical groups from a molecule, we can use the interactions from these groups to predict the properties the molecule will have based on parameters regressed from known molecules. Environmental Fate of Contaminants
Half-life The time it takes for half of the species to be consumed. Integrated Rate Laws
Hazard A chemical or physical condition that has the potential to cause an accident (example of significant chemical plant hazard: flammable, explosive, reactive & toxic hazards). Hazard Identification
Heat Heat is the energy flow due to temperature difference Introduction to Energy Balances
Heat capacity Heat capacities are physical properties that describe how much heat is needed to increase the temperature of a compound for a unit temperature per unit mass of a compound Phase Change and Heat Capacity
Heat of formation The heat of a reaction in which the compound is formed from its elemental constituents as they would normally occur in nature. The change in enthalpy of a reaction can be calculated by summing up the heats of formations of the reactants and the products multiplied by the reaction coefficients independently. Reactive Energy Balances
Heat of fusion The enthalpy change for phase change from solid to liquid occurring at constant temperature and pressure. Phase Change and Heat Capacity
Heat of reaction The stoichiometric enthalpy difference when reactants react completely to form products at a specified constant temperature and pressure. Reactive Energy Balances
Heat of vapourization The enthalpy change for phase change from liquid to gas occurring at constant temperature and pressure. Phase Change and Heat Capacity
Heat transfer Heat transfer is the movement of energy from one place or material to another as a result of a difference in temperature. Introduction to Energy Balances
Henry’s Law pi=yi×P=xi×Hi(T) used to describe the concentration of a gas (or very volatile component) dissolved in a liquid. Multicomponent Equilibrium
Hess’s Law The total enthalpy change of an overall reaction will be the sum of the enthalpies of the individual reactions that sum up to the total overall reactions. Reactive Energy Balances
Human toxicity potential (HTP) A measure of the potential harm caused by chemicals released into the environment Life Cycle Assessment
Ideal Gas Law Relates pressure (P), volume (V), temperature (T) and the number of moles (n) of an ideal gas species using the ideal gas constant (R): PV=nRT Ideal Gas Properties
Ideal mixture An ideal mixture contains substances with similar molecular interactions (which usually means similar structures or functional groups). Ideal Gas Properties
Impact analysis Assess the impacts on human health and the environment. Life Cycle Assessment
Incident Loss of control of material of energy (e.g. leak in a pipe). An Introduction to Process Safety
Incompressible The density does not change significantly with changes in pressure. Ideal Gas Properties
Indirect costs in FCI Costs related to intangible items, these won’t stay at the end of building the plant, for example, supervision and project management expenses. Plant Capital Cost
Inherently safer design Permanently and inseparably reduce or eliminate process hazards -> what we don’t have in the process we don’t need to control. An Introduction to Process Safety
Input Mass and/or energy that enters through the system boundaries. Input-Output Diagrams
Input-output diagram These diagrams are considered to be the simplest of process flow sheets. In input-output diagrams, the entire process is represented by 1 block only. They usually only reference the main process streams in and out of a process. Input-Output Diagrams
Inside battery limit Equipment and components that are associated with the main process feed streams, such as piping on process fluid streams. Introduction to Chemical Processes and Process Diagrams
Integrated rate law Rate laws are differential equations that can be integrated to find how the concentrations of reactants and products change with time. Integrated Rate Laws
Intensive variables Variables that do not depend on the size of a system. Intensive & Extensive Variables
Intermediate event Occurs as a result of events at a lower level acting through logic gates. Hazard Identification
Intermediates Species that are produced in one step and consumed in a subsequent step are called intermediates. Reaction Mechanisms – Elementary Reactions
Intermolecular forces Intermolecular forces are forces that take place between individual molecules. Ideal Gas Properties
Internal energy Internal energy can be described as all other energy present in a system, including motion, and molecular interaction. Introduction to Energy Balances
Isolated systems No energy or mass transfer between system and surroundings, energy may change form within the system Introduction to Energy Balances
Isolation method A method used for determining the rate constant in a reaction rate with multiple species. This method takes one of the species as a constant by adding a high concentration to the system and performing a concentration over time analysis on the species with a small concentration. Reaction Order
Kinetic control (of a set of reactions) Controlling the products resulting from a reactant or reactants through reaction rates. Kinetic & Thermodynamic Control
Kinetic energy The energy associated with motion, which can be described as translational or rotational energy. Introduction to Energy Balances
Lang Factor Relates purchased equipment cost to total capital investment (TCI) and fixed capital investment(FCI). This factor represents the cost of building a major expansion onto an existing chemical plant, including other costs such as piping, control, etc. Lang Factor and Return on Investment
Life Cycle Assessment (LCA) A technique used to quantify the environmental impact of a product from raw material acquisition through end of life disposition (cradle-to-grave). Life Cycle Assessment
Life cycle inventory Quantifies the energy and raw material inputs and environmental releases associated with each life cycle phase. Life Cycle Assessment
Life of equipment The amount of time the equipment is in use. Costs of Manufacturing
Linearize the equation (for reaction rate laws) Plot log(r0) vs log([A0]), where the slope is the reaction order in A; and y-intercept equals to log(keff). Reaction Order
Loss prevention Prevention of injury to people, damage to the environment, loss of equipment, inventory, production, reputation or economic loss. An Introduction to Process Safety
Manipulated variable A variable that we can control in the process and directly affects the output of the process. Process Control
Manometer a U-shaped tube containing some kind of fluid with known density, and one side is connected to the region of interest while the reference pressure is applied to the other. The difference in liquid level represents the applied pressure. Process Control
Marshall and Swift equipment cost index A common type of cost index that is used to estimate the price of equipment over time. Purchased Equipment (PE) Cost
Method of initial rates This method measures the concentration of a species over time (the species with the lower concentration) and takes the logarithm of the rate law to find the order of the reactant from the slope. Reaction Order
Mixer Has multiple feed streams and mixes these streams into one output stream Unit Operations and Material Balances
Molar volume The molar volume is the volume divided by the moles. Ideal Gas Properties
Molarity The molar concentration is expressed in units of mole per (volume*time). Definitions of Reaction Rate and Extent of Reactions
Mole fraction The mole fraction is the moles of the component over the total moles in the container. Multicomponent Equilibrium
Molecularity The molecularity is the number of molecules or atoms coming together to react in an elementary reaction. Reaction Mechanisms – Elementary Reactions
Net economic potential (NEP) NEP = GEP – Production Costs (utilities, labour, maintenance) Basic Economic Analysis
Non-scenario based methods Look at a process in general; effectiveness of the output depends largely on the expertise of the PHA team members, such as checklist analysis. Hazard Identification
Nonseparable differential equation Non-separable differential equations are differential equations where the variables cannot be isolated. These equations cannot be easily solved and require numerical or analytical methods that will be taught in future courses. Unsteady-state Operations and Process Control
Number of operating labour The number of operators needed in the plant at a given time (per shift) to ensure it runs smoothly. Cost of Operating Labour
Obstruction meter An obstruction meter measures the change in pressure and correlates it to flow. Process Control
Occupational cancer hazard (OCH) Release of substances that can potentially cause cancer, such as certain chemicals, dust, radiation. Life Cycle Assessment
Occupational non-cancer hazard (OnCH) Cause of potential diseases, injuries, or other health problems. Life Cycle Assessment
Octanol/water partition coefficient The ratio of the concentration of a substance dissolved in n-octanol and in water. Environmental Fate of Contaminants
Open systems Energy and mass transfer between systems and surroundings, typically use a dot with quantities that change over time in these open systems to denote the flow rate of energy or mass. Introduction to Energy Balances
Operating history Process changes, failures, past incidents. An Introduction to Process Safety
OSHA Occupational Safety & Health Administration An Introduction to Process Safety
Outcome / Consequence The physical manifestation of an accident. An Introduction to Process Safety
Output Mass and/or energy that exits through the system boundaries. Input-Output Diagrams
Outside battery limit Equipment, components, utilities, and other facilities acting on the utilities or waste treatment (not included in inside battery limits) that are associated with the process, but not related to the current design scope. Project Scoping
Overall order The overall order of a reaction is the sum of the orders of all substances involved. Reaction Order
Partial pressure The pressure produced by one gaseous component if it occupies the whole system volume at the same temperature, commonly used for gasses. Multicomponent Equilibrium
Phase change Phase changes take place when a compound or mixture of compounds undergoes a change in their state of matter (i.e. gas to liquid). Reactive Energy Balances
Phase diagram Plots of pressure versus temperature showing the phase in each region provide considerable insight into the thermal properties of substances. Phase Diagram
Phase transitions The phase of a substance and separation between molecules are related to the intermolecular forces in a substance. Therefore, a source of energy needs to be supplied when the substance transitions to a higher energy state to separate the molecules in the substance. Phase Diagram
Photochemical oxidation potential (POP) Releasing chemicals that react in the sunlight and release harmful products into the environment Life Cycle Assessment
Physical properties Physical properties are properties that can be measured without changing the molecular structure of the substance (volume, temperature, and pressure). Phase Equilibrium
Piping and instrumentation diagram (P&ID) P&IDs are based on PFDs but include more specific information. P&IDs do not include: operating conditions (T, P) Stream flows Equipment locations Supports, structures, and foundations Pipe routings (lengths, fittings such as elbows, but connections above a certain size are generally shown). A P&ID often depicts one unit operation in thorough detail. Piping and Instrumentation Diagrams (P&IDs)
Pneumatic connection An air or gas flow control connection. Piping and Instrumentation Diagrams (P&IDs)
Potential energy Energy present due to position in a field, such as gravitational position or magnetic position. Usually, for chemical processes, we consider the potential energy change due to the gravitational position of the process equipment. Introduction to Energy Balances
Pre-equilibria The pre-equilibrium approximation assumes that the reactants and intermediates of a multi-step reaction exist in dynamic equilibrium. Steady-State Approximation
Pressure The amount of force exerted per area in a system. Pressure Definition; Absolute & Gauge Pressure
Process flow diagram (PFD) More detailed chemical process flowsheets. Look at the section for a more detailed definition. Process Flow Diagrams (PFDs)
Process path A real or hypothetical path that a system goes through from an initial to a final equilibrium state. Process paths usually progress in steps that change on state property at a time Phase Change and Heat Capacity
Process variable The variable in the system or process that we desire to control. Introduction to Unsteady-state Operations
Purchased equipment cost The purchased price of equipment from a vendor (someone selling the equipment). It is one of the major factors in the TCI direct costs. Purchased Equipment (PE) Cost
Purchased value The cost of buying a piece of equipment. Purchased Equipment (PE) Cost
Pxy diagram Multicomponent diagrams with the pressure on the y-axis and the liquid and vapour mole fractions on the x-axis. Pxy Diagram
Raoult’s Law pi=yi×P=xi×pi(T) used when all components are in relatively significant quantities or they are chemically very similar Multicomponent Equilibrium
Rate constant The rate constant is a constant in the rate law expression that independent of species’ concentrations, but generally dependent on temperature. Integrated Rate Laws
Rate-determining step The rate-determining step is the step that determines the overall rate of reaction in a series of reactions. Reaction Order
Reaction mechanism The sequence of events that occur at the molecular level during a reaction is the mechanism of the reaction. Reaction Mechanisms – Elementary Reactions
Reaction order in a substance The dependence of the rate of reaction on the reactant concentrations can often be expressed as a direct proportionality, in which the concentrations may be raised to be the zeroth, first, or second power. The exponent is known as the order of the reaction with respect to that substance. Reaction Order
Reaction rate A reaction rate shows the rates of production of a chemical species. It can also show the rate of consumption of a species; for example, a reactant. Reaction Rate Law
Reaction rate law The relationship between the rate of reaction and the concentration of reactants. Reaction Rate Law
Reactor A reactor typically consists of a vessel in which a reaction (or multiple reactions) takes place. Unit Operations and Material Balances
Recycling Putting energy or materials back into use. Concepts and Definitions
Reduced properties Reduced properties are defined as variables (pressure, temperature) scaled by their values at the critical point. Reduced properties can be useful in coming up with general equations describing different substances. Ideal Gas Properties
Reference state A state of a substance at some pressure, temperature, and state of aggregation (solid, liquid, gas; pure, or mixture) used as a reference for calculation purposes. Introduction to Energy Balances
Results interpretation Evaluate opportunities to reduce energy, material inputs, or environmental impacts at each stage of the product life-cycle. Life Cycle Assessment
Return on investments (ROI) The ratio of net profit and total capital investment.
Lang Factor and Return on Investment
Revenue The total profit we generated from selling the product without deducting the cost of production. Lang Factor and Return on Investment
Risk The probability of an accident occurring and the consequence of it An Introduction to Process Safety
Rotational or turbine flowmeter A rotational or turbine flowmeter measures the speed of the rotation of the turbine and correlates it to flow. Process Control
Safety The strategy of accident prevention An Introduction to Process Safety
Safety triangle The safety triangle shows three essential aspects to achieve workplace safety:
Technical – characterization and control of hazards
Management – policies and procedures for safety
Cultural – motivating people to do things safely
An Introduction to Process Safety
Salvage value The value we can recover from a piece of equipment’s end of life. Costs of Manufacturing
Saturated liquid Liquid that is about to vapourize. It will vapourize with any little amount of decrease in pressure or increase in temperature. Txy Diagram
Saturated vapour Vapour that is about to condense. It will condense to a liquid with any little amount of increase in pressure or decrease in temperature. Txy Diagram
Scenario A sequence of events causing the hazard to result in an accident Hazard Identification
Scenario-based methods Used to predict accident scenarios; a lot more detailed and specific, such as what-if analysis Hazard Identification
Separable differential equation Separable differential equations are differential equations where the variables can be isolated to one side of the equation. Separable Differential Equations
Separator A separator is similar to a splitter but has the ability to split streams into different exiting compositions Unit Operations and Material Balances
Set-point This is a target or desired value of a variable in the system (such as flowrate, temperature, etc.) Process Control
Shaft work Shaft work is work done on process fluid by a moving part, such as a pump, rotor, or a stirrer. Introduction to Energy Balances
Solubility The ability of a substance to dissolve. Environmental Fate of Contaminants
Sonic / Radar A sonic or radar device measures the level of the tank by measuring the time for a wave to reach the liquid-gas interphase and reflect back to the device and correlating the time to distance. The sonic or radar device can be installed from the top or bottom of the tank. Process Control
Specific property This denotes an intensive property obtained by dividing an extensive property by a total amount of flow rate (can be the total number of moles or total mass). Introduction to Energy Balances
Splitter A splitter will split a feed stream into multiple streams with the same composition. The exiting streams are not necessarily equal in terms of flow rates, but will always have the same composition Unit Operations and Material Balances
Standard specific heat of formation The enthalpy change associated with forming 1 mole of the compound of interest at standard temperature 25°C and pressure (1 atm). Reactive Energy Balances
Steady-state approximation This approximation assumes that the intermediate concentration is very low so that it does not change with time. Steady-State Approximation
Steady-state open system energy balance An energy balance performed on a steady-state (unchanging) open system (mass and energy are transferred between the system and the surroundings).
Q̇ + Ẇ = Σout(Ėj) – Σin(Ėj)
Introduction to Energy Balances
Steam table Detailed information on water’s state properties at different temperatures and pressures available in a tabulated form Introduction to Energy Balances
Stoichiometric coefficient Stoichiometric coefficients are the numerical coefficients associated with each reactant or product. Definitions of Reaction Rate and Extent of Reactions
Substitution Using less harmful materials, or optimizing the process to reduce the formation rate of harmful by-products. Concepts and Definitions
Supercritical fluid Above the critical point, liquid and gas can no longer be distinguished and are classified as a supercritical fluid. Phase Diagram
Surroundings / Environment The environment that is ‘outside’ of the system’s boundaries. Introduction to Energy Balances
Temperature A measure of the average kinetic energy of a system. Temperature
Thermodynamic control (of a set of reactions) Controlling the products resulting from a reactant or reactants through reaction equilibrium Kinetic & Thermodynamic Control
Thermodynamic system A thermodynamic system includes anything whose thermodynamic properties are of interest. It is embedded in its surroundings or environment; it can exchange heat with and do work on its environment through a boundary. Kinetic & Thermodynamic Control
Total capital investment (TCI) The amount of money (aka. capital) needed for a project to proceed. TCI is the total amount of funds needed to build and start a chemical plant, including the testing and troubleshooting stages before the actual production. It does not include operating expenses or maintenance during the production process. Basic Economic Analysis
Transient balances Transient balances are any balances that where some quantities involved in the balance are functions with time. Introduction to Unsteady-state Operations
Triple point The triple point is defined to be the set of pressure and temperature that solid, liquid and vapour are in equilibrium together. Phase Diagram
Txy diagram Multicomponent diagrams with the temperature on the y-axis and the liquid and vapour mole fractions on the x-axis. Txy Diagram
Undeveloped event Undeveloped event due to lack of information or significance. Treated like a basic event in the analysis, but could have been developed into another fault tree. Process Safety
Unimolecular reaction Only one molecule is involved, examples might include an isomerization or decomposition Reaction Mechanisms – Elementary Reactions
Unit operation Major chemical and biological processing equipment. They are usually drawn as circles or squares in BFDs. Unit Operations and Material Balances
Unsteady-state In unsteady-state processes, mass and energy in the system are changing with time (not constant). Introduction to Unsteady-state Operations
Utilities Utilities are services at a site such as water, electricity, and gas. Phase Change and Heat Capacity
Vapour pressure Vapour pressure is defined as the pressure at which a gas coexists with its solid or liquid phase. Estimating Vapour Pressure
Vapour temperature Vapour temperature is defined as the temperature at which a gas coexists with its solid or liquid phase. Estimating Vapour Pressure
Vapour-liquid equilibrium The same number of molecules vapourizing and condensing at any given period of time (meaning no net change in the system). Multicomponent Equilibrium
Volatility How likely a compound will evaporate. Multicomponent Equilibrium
Volume The space occupied by a system. Ideal Gas Properties
Waste management hierarchy A hierarchy describing actions for managing waste that goes from most desirable to least desirable. Concepts and Definitions
What-if analysis What-if analysis is a scenario PHA method as it investigates specific problems and traces what would happen if they occur. Results in a list of potential consequences and suggestions of mitigation methods (if needed). Hazard Identification
Work Work is energy resulting from driving forces (not temperature) such as force, torque, or voltage. Introduction to Energy Balances
Working capital (WC) The initial money required to start the plant. It is the money needed for supplies or people that is not recovered until after the plant closes. Since this is generally a long-time in the future, it is considered a capital investment rather than a manufacturing cost. Plant Capital Cost
Zeroth/first/second-order rate law The overall reaction orders for rate laws. Each of these rate laws has distinct graphical characteristics. Reaction Order


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