化学工学英語：必須語彙とフレーズ

"heat exchanger"

A device that transfers thermal energy between two fluid streams without mixing them

"The shell-and-tube heat exchanger recovered waste heat from the reactor effluent to preheat the feed stream."

"distillation column"

A vertical vessel that separates a liquid mixture into its components by repeated vaporisation and condensation

"The distillation column operated at a reflux ratio of 3:1 to achieve 99.5% purity in the overhead product."

"mass transfer coefficient"

A parameter quantifying the rate at which a component moves from one phase to another across an interface

"Engineers calculated the mass transfer coefficient to size the packed absorption column for the gas scrubber."

"residence time"

The average time a fluid element spends inside a reactor or vessel

"Increasing the residence time from 20 to 45 minutes boosted conversion of the limiting reactant from 72% to 94%."

"pressure drop"

The loss of pressure experienced by a fluid as it flows through a pipe, valve, or packed bed

"Excessive pressure drop across the catalyst bed indicated fouling and prompted an unplanned shutdown for regeneration."

"packed bed"

A column or vessel filled with solid packing material to promote contact between gas and liquid phases

"The packed bed absorber reduced SO₂ emissions from 1,200 ppm to below the regulatory limit of 50 ppm."

"reflux ratio"

The ratio of liquid returned to the top of a distillation column to the distillate product withdrawn

"Reducing the reflux ratio from 4 to 2.5 cut steam consumption by 30% without sacrificing product specification."

"overall heat transfer coefficient"

A combined resistance parameter (U-value) describing how effectively heat passes through a composite wall or exchanger surface

"Fouling on the tube side reduced the overall heat transfer coefficient from 850 to 610 W/m²·K over six months of operation."

"continuous stirred-tank reactor"

A reactor with perfect mixing in which feed continuously enters and product continuously exits at steady state

"The pilot plant used a continuous stirred-tank reactor cascade to achieve the desired residence time distribution."

"plug flow reactor"

An idealised tubular reactor in which fluid moves in one direction with no axial mixing

"A plug flow reactor was selected for the polymerisation step because high conversion required a long mean residence time."

"conversion"

The fraction of a reactant that has been consumed in a chemical reaction

"The design specification called for 95% conversion of ethylene oxide before the product entered the purification train."

"selectivity"

The fraction of consumed reactant that is converted to the desired product rather than by-products

"Catalyst development efforts focused on improving selectivity for the target alcohol from 68% to above 85%."

"activation energy"

The minimum energy barrier that reactant molecules must overcome for a chemical reaction to proceed

"The Arrhenius plot revealed an activation energy of 85 kJ/mol, confirming that the reaction was kinetically controlled."

"space velocity"

The volumetric or mass flow rate of feed divided by the reactor volume, expressing how often the reactor volume is refreshed per unit time

"Operating at a higher space velocity reduced contact time and suppressed the undesirable consecutive decomposition reaction."

"heat of reaction"

The enthalpy change associated with a chemical reaction at constant pressure, indicating whether the reaction is exothermic or endothermic

"The large exothermic heat of reaction required a dedicated cooling jacket to prevent a runaway temperature rise."

"catalyst deactivation"

The loss of catalytic activity over time due to poisoning, sintering, fouling, or coking

"Catalyst deactivation by sulfur poisoning necessitated a guard bed of zinc oxide upstream of the main reactor."

"HAZOP study"

Hazard and Operability Study — a structured technique for systematically examining a process design for potential hazards and operating problems

"During the HAZOP study, the team identified a high-pressure deviation scenario that required an additional relief valve."

"layer of protection analysis"

A method for evaluating the adequacy of independent protection layers against a hazardous event

"Layer of protection analysis confirmed that three independent safeguards reduced the risk of a toxic release to an acceptable level."

"relief valve"

A pressure-activated safety device that automatically vents excess pressure from a vessel or pipeline to prevent catastrophic failure

"The relief valve lifted at 15 bar and safely discharged steam to the flare header during the blocked-outlet scenario."

"flammability limits"

The range of fuel-to-air concentrations between the lower explosive limit and upper explosive limit within which ignition can occur

"Nitrogen blanketing maintained the vapour space below the lower flammability limit of 1.4% for the stored hexane."

"inherently safer design"

An approach that eliminates or reduces hazards at the source rather than relying on added controls and barriers

"Substituting a less toxic solvent was an inherently safer design measure that removed the need for extensive containment."

"runaway reaction"

An uncontrolled exothermic reaction in which heat generation exceeds heat removal, causing a rapid temperature rise

"The investigation concluded that a runaway reaction was triggered by the accidental addition of a catalyst inhibitor at the wrong stage."

"safety integrity level"

A discrete level (SIL 1–4) quantifying the required probability of failure on demand for a safety instrumented function

"The emergency shutdown system was designed to SIL 2, requiring a probability of failure on demand below 10⁻³ per year."

"bow-tie analysis"

A risk visualisation method showing the causes and consequences of a hazardous event with preventive and mitigative barriers on either side

"The bow-tie analysis for the chlorine release scenario mapped eight preventive barriers and five emergency response measures."

"enthalpy"

A thermodynamic property equal to internal energy plus pressure–volume work, used to quantify heat flow at constant pressure

"The process engineer used enthalpy balances around each heat exchanger to verify the energy integration scheme."

"fugacity"

An effective pressure that accounts for non-ideal behaviour in a real gas or liquid mixture, used in phase equilibrium calculations

"Fugacity coefficients from the Peng–Robinson equation of state were used to predict vapour–liquid equilibrium at high pressure."

"equation of state"

A mathematical relationship linking the pressure, volume, and temperature of a substance or mixture

"The Soave–Redlich–Kwong equation of state accurately described the compressibility of the natural gas mixture across process conditions."

"Gibbs free energy"

A thermodynamic potential that predicts whether a process occurs spontaneously at constant temperature and pressure

"Minimising Gibbs free energy showed that the equilibrium methanol yield was 62% at 250 °C and 50 bar."

"thermal conductivity"

A material property quantifying its ability to conduct heat through molecular interactions

"The low thermal conductivity of the ceramic insulation reduced heat loss from the high-temperature calciner by 40%."

"viscosity"

A measure of a fluid's resistance to flow or deformation under shear stress

"The polymer melt viscosity rose sharply with molecular weight, complicating pumping and mixing operations."

"Prandtl number"

A dimensionless ratio of momentum diffusivity to thermal diffusivity, characterising heat transfer in fluid flow

"The high Prandtl number of the process oil indicated that the thermal boundary layer was much thinner than the velocity boundary layer."

"azeotrope"

A mixture of two or more liquids whose vapour has the same composition as the liquid, making separation by ordinary distillation impossible

"The ethanol–water azeotrope at 95.6 wt% ethanol required a molecular sieve drying step to produce anhydrous fuel-grade ethanol."

"liquid–liquid extraction"

A separation technique that exploits different solubilities of a solute in two immiscible liquid phases

"Liquid–liquid extraction with methyl isobutyl ketone recovered acetic acid from the aqueous fermentation broth."

"membrane filtration"

A pressure-driven separation process that uses a semi-permeable membrane to retain solutes or particles while allowing solvent to pass

"Nanofiltration membranes were selected to remove divalent ions while passing monovalent sodium chloride in the brine treatment unit."

"crystallisation"

A separation and purification process in which a solute precipitates from solution as a highly ordered solid crystal structure

"Cooling crystallisation produced pharmaceutical-grade paracetamol crystals with a particle size distribution meeting the specified d₅₀ of 100 μm."

"theoretical stage"

An idealised equilibrium contact between phases in a separation column, used as a basis for calculating the number of real trays or transfer units needed

"The simulation predicted that 24 theoretical stages were required to meet the product specification for the benzene–toluene separation."

"absorption"

A mass transfer operation in which a gas component is dissolved into a liquid solvent flowing counter-currently in a column

"Amine absorption removed CO₂ from the syngas stream to below 50 ppm before the methanation catalyst."

"adsorption isotherm"

A curve relating the equilibrium loading of an adsorbate on a solid at constant temperature across a range of concentrations or partial pressures

"The Langmuir adsorption isotherm fitted the experimental data well and was used to size the pressure swing adsorption unit."

"stripping factor"

A dimensionless parameter used in absorption design that relates the equilibrium constant to the ratio of gas to liquid flow rates

"Increasing the stripping factor from 1.2 to 1.8 reduced the number of theoretical stages required for the desired recovery."

"permeate flux"

The volumetric flow rate of fluid passing through a unit area of membrane per unit time

"Permeate flux declined steadily over 72 hours due to concentration polarisation and required a backwash cycle."

"piping and instrumentation diagram"

A detailed schematic showing all process equipment, piping, instrumentation, and control loops in a chemical plant

"The updated piping and instrumentation diagram was issued for construction after the HAZOP action items had been resolved."

"process flow diagram"

A simplified diagram showing the major pieces of equipment, streams, and operating conditions of a process

"The process flow diagram presented to management showed three alternative separation sequences with indicative capital costs."

"proportional–integral–derivative controller"

A feedback control algorithm that combines proportional, integral, and derivative terms to minimise the deviation of a process variable from its set point

"The proportional–integral–derivative controller on the reactor temperature loop was retuned after the heat exchanger was replaced."

"feed-forward control"

A control strategy that uses measurements of disturbances to make predictive corrections before the process variable deviates

"Feed-forward control of the steam flow compensated for variations in the cold feed temperature entering the heat exchanger."

"pinch analysis"

A systematic methodology for designing heat exchanger networks that minimise energy consumption by identifying the thermodynamic pinch point

"Pinch analysis identified potential energy savings of 2.4 MW, justifying the addition of two new cross-heat exchangers to the network."

"mass balance"

An accounting of all material entering and leaving a system boundary over a defined period, based on conservation of mass

"Closing the mass balance around the reactor revealed an unaccounted-for loss of 3% that was traced to a leaking flange."

"design basis"

A documented set of process conditions, throughput rates, and specifications that define the scope and constraints of an engineering design

"The design basis for the new ethylene cracker was issued to the contractor before the front-end engineering and design phase began."

"debottlenecking"

The process of identifying and removing constraints that limit throughput or performance in an existing chemical plant

"Debottlenecking the distillation train by replacing conventional trays with structured packing increased capacity by 25% without major capital expenditure."