Asst. Prof. Jewel A. CapunitanDepartment of Chemical EngineeringCollege of Engineering and Agro-Industrial TechnologyUniversity of the Philippines Los Baños
ChE 154 - Transfer Operations II1st sem. 2015-2016
INTRODUCTION
DIAGNOSTICS
One hundred kilograms of a mixture of materials A & B is
subjected to a separation process. If 80% of A from the feed
was recovered in one stream, which contains 40 kg of A,
what is the composition of the original mixture?
DIAGNOSTICS
UNIT OPERATION or UNIT PROCESS?
Evaporation
Filtration
Hydrogenation
Gas absorption
Fermentation
What is Chemical Engineering?
Application of the principles of the physical sciences,
economics, and human relations to fields that pertain directly
to processes and process equipment in which matter is
treated to effect a change in state, energy content or
composition (Foust et al., 1980)
Has something to do with industrial process in which raw
materials are changed or separated into useful products (Mc
Cabe et al., 1993)
Philippine Republic Act (RA) 9297
Chemical Engineering Law of 2004
Chemical engineering involves conceptualization,development, design, improvement and application of safe,
healthy, ethical and economic ways of utilizing materials
and energy in unit processes and operations for the benefit
of society and environment through the application of
chemical engineering subjects and the knowledge ofnatural and physical science, mathematics, information
technology and other general education subjects.
Tasks of the Chemical Engineer…
To develop, design and engineer a complete process andequipment used
To choose the appropriate raw materials
To ensure that the plant operates efficiently, safely andeconomically
To produce products that meet the standards of thecustomer
WAYS TO STUDY INDUSTRIAL PROCESSING
Each industry as a unit
Each unit operation with its functions
Example: SALT MANUFACTURE
Transportation of solids and liquids
Heat transfer
Evaporation
Crystallization
Drying
Screening
Example: PETROLEUM INDUSTRY
Transportation of solids and liquids
Heat transfer
Distillation
Mechanical Separation
UNIT OPERATION
shall mean the physical operation by which a desired step in an
industrial process is conducted or controlled. This includes, but
is not limited to: storage of gases, liquids, solids, heat transfer,
evaporation; mass transfer, i.e. distillation, absorption,
adsorption, drying, humidification, extraction, leaching, mixing
and dispersion, separation, i.e. filtration, screening, molecular
sieving and coalescing.
UNIT PROCESS
shall mean the chemical change which is involved in the
manufacture of industrial or consumer products or the
treatment of industrial or chemical wastes.
CLASSIFICATION OF UNIT OPERATIONS
Based on Functions and Phase Treated
Unit operations that treat solids
Unit operations that treat fluids
Mass transfer
Heat transfer
PROPERTIES OF SOLIDS
SOLIDS
Can be found in many forms (powders, rolls, sheets, etc.)
Difficult to handle as compared to liquids and gases
Many industries deal with solid materials either as feedstock, product or process intermediates
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TYPICAL SOLIDS PROCESSING OPERATIONS
Particle sizing & shaping Crushing/grinding Particle classification
(separation by size) Flocculation Settling Packing & compaction Caking
Drying
Adsorption/desorption
Crystallization
Flotation
Fluidization
Leaching
Filtration
Ion exchange
SOME INDUSTRIES THAT USE FLUID/PARTICLE PROCESSES
water conditioning
coal chemicals
industrial carbon
ceramics
paints
explosives and propellants
agriculture
fermentation wood
pulp and paper
synthetic fibers
petrochemicals
environmental cleanup
glass industry
phosphorous production
potassium production
nuclear industries
food and food processing
sugar and starch
chemicals
plastics
rubber industries
pharmaceuticals
SOLIDS
Particulate Solids - individual solid particles that arecharacterized in terms of their size, shape and density.
Mixture of Particles - described by average or total values ofdifferent parameters; can be homogeneous orheterogeneous.
PROPERTIES OF SOLIDS
Brown et al. (1950)
Specific Gravity
Density
Hardness
Brittleness or Friability
Toughness
Friction McCabe et al. (1993)
Size
Shape
Density
PROPERTIES OF SOLIDS
Foust et al. (1980)
1. Properties of individual particles and bulk particles
Size
Shape
Volume
Solid Density
Mass
Thermal Conductivity
Surface Area
Hardness
Hygroscopic Tendency
Specific Heat
PROPERTIES OF SOLIDS
Foust et al. (1980)
2. Properties of the solids-voids phase particles
Void fraction or porosity
Effective density
Surface area per cubic feet
Effective thermal conductivity
Permeability
Angle of repose or steepness
Definition of Some Selected Properties
1. DENSITY
For gases and liquids, we assume that the materialscompletely fill the volume of the holding container
For solids, the same assumption cannot be applieddue to the presence of voids (spaces or pores) withinthe material
1. DENSITY
Table 1. Density Terms
Term Symbol Formula
Porosity Єvoid volume /
total bed volume
Absolute (True Density)
ρa
mass of solids/ volume of solids
Bulk (Apparent density)
ρb
mass of solids / total bed volume
Note:• Bulk density (ρb) is not intrinsic characteristic of material but a function of
size distribution, porosity and kind of material.• If the material is non-porous, ρa = ρb = ρ.
1. DENSITY
Example 1
Suppose 600 g of crushed ore is placed in a graduated
cylinder, filling it to the 184-cm3 level. One hundred cubic
centimeters of water is then added to the cylinder,
whereupon the water level is observed to be 233.5 cm3.
Calculate the (a) porosity of the dry particle bed, (b) bulk
density of the ore in wet bed, that is ore plus water, and (c)
absolute density of the ore.
2. SPECIFIC GRAVITY
For solids and liquids, water is usually the reference material
SG =ρmaterial
ρreference
3. HARDNESS
Defined as the resistance toindentation (metals &plastics) or scratching (forminerals)
Hardness is expressed interms of the Mohs’ scale(based on a series ofminerals of increasinghardness)
Mohs’ Scale
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Feldspar
7. Quartz
8. Topaz
9. Sapphire
10. Diamond
Note:A mineral with higher Mohs’scale rating can scratch theothers having a lower rating.
4. BRITTLENESS or FRIABILITY
The ease with which a substance may be broken by impact
Influenced by the substance’s crystalline structure and size
After crushing, different outcome shape because of the“cleavage planes” which are the crystalline planes in whichcrystals are easily broken
Should not be equated to hardness because some softmaterials is not friable ( ex. plastic materials )
5. TOUGHNESS
Opposite of friability
For metals and alloys, this is termed as “impact resistance”
6. FRICTION
Resistance to sliding of one material against anothermaterial
7. PARTICLE SHAPE
Expressed in terms of sphericity or Φs (consider sphere ashaving the simplest shape)
surface area of a sphere havingSphericity = the same volume as the particle
surface area of the particle
For spherical particle, Φs = 1
7. PARTICLE SHAPE
For non-spherical particle
where :
Dp = equivalent diameter (equalto the computed diameterof a sphere having thesame volume as theparticle in question)
p = volume of one particle
Sp = surface area of one particle
Φs =6υ p
D p S p
υ
Example of sphericity values:
Crushed materials: 0.6-0.8
Particles rounded by abrasion:0.95
Cubes: 0.81
Table 28.1, p.928, McCabe,5th ed.,1993
7. PARTICLE SHAPE
Example 2
Determine the sphericity of a cylinder with height-todiameter ratio of 2.
8. SIZE
For an equidimensional particle, this is referred to as“diameter”
For non-equidimensional particle, the size is based on thesecond longest major dimension (not on the longest availabledimension)
8. SIZE
For an irregularly shaped particle, the size is based on the sizeof an equivalent sphere
Often expressed in different units depending on the size rangeof particles:
a. Coarse particles (inches, mm)
b. Fine particles (screen size, mesh no.)
c. Very fine particles (micrometer, nanometer)
d. Ultrafine particles (surface area per mass)
END OF LECTURE
REMINDERS!
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