DIPLOMA ENGINEERING N. G. PATEL POLYTECHNIC 637 CHEMICAL
ENGINEERING 05 MECHANICAL OPERATION (CEO-I) 320013
MECHANICAL OPERATION (CEO-I) 3320013Semester - 03Kartik R.
DesaiHead, CHED, NGPP
:REFERENCE BOOKS:
Chapter 1: Properties of Particulate Solids
Definition of Unit Process & Unit Operation:
Unit process: It involves only chemical changes For example -
hydrogenation, halogenations, oxidation, reduction, nitration,
oxidation etc.
Unit operation: It is an operation in which only physical
changes takes place for example filtration, size reduction, heat
transfer, drying, distillation etc.Chapter 1: Properties of
Particulate SolidsDifferences of Unit Operation & Unit
Process:
Sr. No.Unit operationUnit process1It is an operation in which
only physical changes are occurred. It is a process in which
physical and chemical changes are occurred.22.1 Mechanical
operations like filtration, size reductions, screening,
sedimentation etc.2.2 Fluid flow operation like fluidization,
pumping, compression, flow control etc.2.3 Heat transfer operations
like evaporator, cooling, freezing, heat exchanging etc.2.4 Mass
transfer operations like extraction, leaching, distillation
etc.These includes hydrogenation, halogenation, oxidation,
reduction, nitration, sulphonation etc.Chapter 1: Properties of
Particulate SolidsSpecific properties of solids:
1) Specific surface area (Aw)2) Volume-surface mean diameter
(Ds)3) Sphericity (s)4) Mass mean diameter (Dw)5) Volume mean
diameter (Dv)6) Density () & bulk densityChapter 1: Properties
of Particulate SolidsSpecific surface area:If the particle density
(p) and sphericity (s) is known, the surface area of the particles
in each fraction may be calculated and the results for all
fractions are added to give the specific surface area, Aw. If (p)
and (s) are constant Aw is given by
Aw = (6x1 /p . s .Dp1) + (6x2 /p . s .Dp2) + .. + (6xn / p . s
.Dpn) = (6/p .s ) (xi/Dpi) 2) Volume-surface mean diameter:The
average particle size for a mixture of particles is defined by
volume surface mean diameter (Ds), which is related to specific
surface area Aw. (Ds) = 6/ p .s . Aw = 1/ (xi/Dpi)
Chapter 1: Properties of Particulate Solids3) Sphericity (s):A
measure of the particle size which is frequently used is the
sphericity (s).s = Surface area of sphere of same volume as
particle/ Surface area of particle For spherical particle of
diameter (Dp), s = 1. For non-spherical particle, the sphericity is
defined by the relation:s = 6. Vp/Dp . SpDp = Nominal diameter of
particle or equivalent diameter of particleSp = Surface area of the
particleVp = Volume of the particleFor crushed materials, s = 0.6
to 0.8For cubes, s = 0.81; For cylinders, s = 0.87Chapter 1:
Properties of Particulate Solids4) Mass mean diameter (Dw)The mass
mean diameter is given as:Dw = xi. Dpi4 / xi . Dpi3 5) Volume mean
diameter (Dv)The average volume of a particle is the volume mean
diameter given as : (Dv) = [1/ (xi/Dpi3) ]1/3 6) Density & Bulk
Density:Density = defined as its mass per unit volume. Bulk density
is defined as the mass of many particles of the material divided by
the total volume they occupy. The total volume includes particle
volume, inter-particle void volume and internal pore volume.Bulk
density = mass of particle/ volume as a whole
Chapter 1: Properties of Particulate SolidsSphericity s =
6vp/DpspNo. of particles in mixture N = m / pvpTotal surface area A
= N sp = 6 m / s p DpSpecific surface of mixture Aw = 6 / s p (xi /
Dpi)Average particle size Ds = 1 / (xi / Dpi)Mass mean diameter Dw
= (xi Dpi)
Chapter 1: Properties of Particulate SolidsCalculation of no. of
particles particulate solids:No. of particles in mixture N = m /
pvpm = mass of mixture p = density of a particle vp = volume of a
particleChapter 1: Properties of Particulate Solids
