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Basic Chemical Engineering

Lecture - 3

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Process & Process Variables

Process:

A process is any operation or series of operations

by which a particular objective is accomplished.

They can be of two types: Chemical

Example : Chemical Dissolving, pH Balance, Softening of Hard

Water

Physical Example : Drying, Separation, Grinding, Crushing, Mixing

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Process Flow DiagramInputor

Feed

Output

or

Product

Process Unit

Process

Stream

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Difference between Design &

Operation

Design:

Design includes formulation of process flow sheet

(layout) as well as specification of individual process

units (such as reactors, separation equipment & heatexchangers) and associated process variables.

Operation:

Operation involves the day to day running of the

process. The process and all the equipment must

produce product at designated rate and with specified

characteristics.

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Troubleshooting

Debottlenecking

Turn-down.

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Quick Review

Density:

Specific Volume:

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Quick Review

Specific Gravity:

Do it Yourself(DIY):

Example 3.1 1

Example 3.1 2

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Process Variables

Flow Rate:

(DIY) Question 1 & 2, Pg. 47.

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Process Variables

Composition of Mixtures:

Moles:

A gram mole of a specie is the amount of that specie

whose mass in gram is numerically equal to itsmolecular weight.

34 kg NH3 = how much number of moles?

(DIY) Example 3.3 - 1

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Process Variables

Molar Flow Rate

Mass & Mole Fraction

Mass Fraction

Mole Fraction

(DIY) Example 3.3 2

(DIY) Example 3.3 3

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Process Variables

Concentration:

Mass Concentration:

Mass of the component per unit volume of the mixture (g/cm3 ,

lbm/ft3)

Mole Concentration:

Moles of the component per unit volume of the mixture (kmol/m3

, lb-moles/ft3

)

Molarity

Molar concentration of the solute expressed per liter of solution.

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Process Variables

Pressure:

Pressure is force per unit area P = F/A = N/m2 = Pascal

Hydrostatic Pressure

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Process Variables

Atmospheric Pressure

Guage Pressure

Absolute Pressure

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Process Variables

Temperature:

Temperature of a substance is the measure of average kinetic energy

possesed by the substance molecules.

It is measured in Celsius, Fahrenheit, Kelvin & Rankine

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Process Variables

The following co-relations are used to

interconvert temperature scales.

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Process Variables

Example 3.5-2

(DIY) Convert the answers of above to Kelvin &Rankine.

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Course Outline for

BSc. Chemical Engineering CHE116 Basic Chemical Engineering

Introduction to chemical engineering: Introduction to Engineering Profession.

Responsibilities and ethics for engineers. Role of chemical engineer. History of

profession and future directions. Career opportunities in Chemical Engineering.

Basic concepts of Chemical Engineering: Units and dimensions, conversion of

units. Process variables; pressure, temperature, concentrations and Compositionof mixtures.

Material balances: Fundamentals of material balances; Program of analysis of

material balance problems, material balance calculations, Balances on non

reactive systems, balance on reactive systems and Processes, Recycle, By-pass and

purge calculations, Case studies on balances for important industrial processes.

Ideal gases, equations of state for real gases. The compressibility factor equationof state.

Energy Balance: Concepts and units, Forms of energy: The first law of

thermodynamics. Calculation of enthalpy changes. Applications of the general

energy balance without reactions occurring.

Ethics: Professional ethics: The ethics challenge and ethical case studies.

Credit hours/ Contact Hours - 2