ParTech Prelims LEC 1

Soild-fluid Process

process based on interaction of fluid (gas and liquid) with solid particles

1. Mechanical

2. Electro-chemical

3. Chemical

What are the three classifications of solid-fluid processes?

• Sizing and transportation of solid

• Chemical synthesis in the presence of catalyst particle

• Mineral benefication, recovery of valuable solids from ores

• Drying of solid, coating of particle, mixing by mechanical means

• Separation of contamination from the effluent, etc. by membrane

Where are solid-fluid processes generally applied?

Mechanical Process

• Slurry Transport

• Solid Transport

• Crushing and Grinding

• Mixing

• Mechanical

• Fluidization

• Decantation

• Minerals recovery by froth flotation

Chemical Processes

• Crystallization

• Drying

• Adsorption

• Copper Extraction

• Trickle bed reactor

• Slurry bubble column

Particle Separation

• Gravity chamber

• Cyclone

• Bag filter

• Electrostatic Precipitator

Conveying

• Engineers prefer to transport in the form of liquids, solutions, or suspensions

• Choice of equipment depends on the necessary capacity, natural shape and size of the materials, the distance through which the material has to be transported.

Comminution

the process of particle size reduction

• Compression

• Impact

• Attrition

Size reduction mainly occurs by?

Crushing and Grinding

What are the primary comminution processes?

Crushing

It is a process of breaking materials into the desired size (to specified size range) by mechanical device.

Grinding

It is a process of a surface generation by producing micro or nano size particle.

• Based on compression mechanism (jaw and cone crushers)

• Based on impact mechanism (bar blow crushers, vertical shaft impactors)

What are the types of crushing equipment based on size reduction?

• jig grinders

• gear grinders

• ball mill

• rod mill

• autogenous mill

• pebble mill

• buhrstone mill

• tower milll

• gap mill

• blade mill

What are the most common types of grinders?

Screening

A process of segregating solid particles into multiple grades according to their opening sizes.

Coarser materials above about 250 microns

What material is suitable for screening for its efficiency decreases with decreasing size of particle.

Classification

It is a process for separating mixtures of particles into two or more fractions based on the velocity with which the particles fall through a fluid medium.

Finer size below about 250 microns

What type of materials are usually processed by classification?

Filtration Process

the separation of solid particles from solid-fluid mixture by a filter medium by a driving force

Cross-flow filters

It is a filter designed to concentrate suspensions of fine particles or colloidal material, solutions of macromolecules. It is generally used for particles in the range of 0.1 to 5 micrometer. Examples include microscreens, porous tube filters, microstraining filters.

Cake Filter

A cake acts as a filter which is formed by the accumulation of the solids on a septum (e.g., filter press, shell and leaf filters, rotary vacuum filters etc.)

Syrings and capsule filters

The filter is designed with a loack at inlet and a fitting on the outlet of a syringe.

It is used when the filtration columes is less than 200 mL. (Capsule filters)

Membrane

Different types of filters made of various materials such as silver, cellulose, nylon, ceramic, etc.

Particulate Matter

a solid particle or liquid droplet having a size 10 micrometer in diameter or less suspended in the atmosphere (aerosol)

PM sub d

What is the conventional symbol used to denote particulate matter?

Using various methods like wet scrubbing, cyclones, candle filters or a combination of these, sedimentation, filtration, and biological treatment

How can particulate matters be separated?

Settling and sedimentation

the process by which particulates are separated from the fluid either by gravity or centrifugal force (gravity settlers and centrifuges)

Thickening

a gravitational settling of solid particles that are suspended in a liquid whereas classifications imply fractionation of solid particles based upon their rates of flow or settling through fluids

Flotation process

• It is a process for separating suspended particles based on hydrophobic and hydrophilic nature of particles by the introduction of gas bubbles

• It is done in a _____ machine which are mechanically agitated tanks, ____ columns, Jameson cells etc.

• the adhesion of gas bubbles to the solid particles makes them buoyant and results in separation

Agitation and Mixing

• It is the central feature of many chemical processes

• It is the process to make the homogeneous mixing of (concentration, phase, temperature) in order to achieve the desired process - yield by increase mass and/or heat transfer, reaction rate, or product properties.

Processes Involving Mechanical Separations

• Screening

• Classification

• Filtration

• Separation of PM

• Settling and Sedimentation

• Thickening

• Flotation

• Agitation and Mixing

Thermo-chemical Processes

• Drying process

• Crystallization Process

• Leaching Process

• Calcination Process

• Roasting Process

• Reaction Process

Drying Process

• Process of removing liquid from a solid at a temp below the boiling point by circulating air or some other carrier gas over the solid

• adiabatic and non-adiabatic

Crystallization

• Process driven by mass transfer of a solute from the liquid solution to a crystalline phase

• formation of crystals precipitating from a super saturated solution (obtained by cooling or solvent evaporation) containing dissolved solids (solute), melts, vapor at a fixed temperature is called crystallization

• first step is called nucleation

Leaching

• Process of separation of a solute from a solid by an insoluble solvent. Solutes are separated based on absorption capability of solute to the solvent

• Material (ore) is graded chemically with a solvent by dissolving the active component into the solvent

• One example is the grading of bauxite using NaOH solution at 150 C, dissolving aluminum oxide in NaOH, extraction of silver from its ores by sodium cyanide, and grading gold-containing ore in potassium cyanide

Calcination

• conversion of concentrated ore into oxide by heating in absence of air

• also helps in separating CO2, SO2, organic impurities, and moisture from the source at a fixed temperature

Roasting

• process of converting ore (usually sulphide, at below its melting T) into an oxide in presence of excess hot air

• also known as metallurgical process of gas-solid reactions at a temperature for purifying the metal components in a blast furnace

• also referred to as frying at a fixed tep, generally done in fluidized bed

Reaction

• a process that leads to the formation of new molecules by the rearrangement or redistribution of the constituent atoms

• depends on T, P, composition, catalyst, and residence time

• chemical reactor

• nuclear reactor

• fusion reactor

• bioreactor

What are the general four types of reactors?

• Electrostatic separation

• Magnetic separation

• Electrodialysis

• Electro-osmosis

• Electrophoresis

• Ion-Exchange

• Pervaporation

• Gas Permeation

What are examples of electrochemical processes?

Electrostatic Separation

• a process of separation of solid particle by means of utilizing forces acting on charged or polarized bodies in an electrical field

• important in the produuction of valuable minerals, for the recovery of other valuable materials

Magnetic Separation

• process to separate magnetic materials from a mixture by using a magnet

• magnetic and hematite ores (pyrolusite (MnO2) and chromite (FeOCr2O3) are upgraded based on magnetic properties of the ore and gangue particles.

Electrodialysis

• process by which charged particles migrate by diffusion and convective flow towards a less charged area by electroosmotic effect

• this is done in an ______ cell where the salt ions move over the membranes under applied electric potential

Electro-osmosis

• applied for separation of ions contained within electrolytes and solvents

• the ______ effect can greatly affect the behavior of the liquid

• a transport process of salt ions through selective semi permeable membrane (cationic or anionic, called ion-exchange membrane), under the influence of an electric potential

• motions of electrolytes and solvent are driven by an applied potential across a porous material, capillary tube, membrane, or in microfluidic devices

Electrophoresis

• a separation technique to separate biological molecules such as DNA, RNA, or protein-based on their size and electrical charge

• electric current moves the molecules through a porous gel

• the pore in the gel works like a sieve which allows smaller molecules to move faster than larger molecules

• protein transport towards a positive charge is an example of this process

Ion - Exchange

• used in water treatment, the cations are exchanged with positively charged ions available on the surface of ion exchanged material (usually sodium)

• separation of unwanted dissolved ions (e.g., nitrate, fluoride, sulfate, and arsenic etc.) in water are exchanged with a similar charge by an ion exchanged material (e.g., resin or a zeolite)

• the anions are exchanged with negatively charged ions (e.g., usually chloride)

Pervaporation

• a process of separation of binary or multi-component mixtures of liquids based on partial vaporization through a polymeric or ceramic membrane

• the feed after heating at the operaing temp pass through the feed side of the ______ membrane

• the desired component passes through the membrane and is continuously taken out in the form of vapour from the permeate side of the membrane

• this concentration gradient (in terms of partial vapour pressure) acts as a driving force for the process

Gas Permeation

• a fractionation of gas mixtures based on permeability to gas according to a dissolution-diffusion mechanism through a membrane

• the gas diffusion through polymers includes random thermal movement of gas molecules in the polymer structure

• graphene oxide, rubbery polymer membranes, and MOFs are some example of promising material for gas permeation

• Properties of Particle

• Particle Shape

• Aspect ratio

• Sphericity

• Zeta Potential

What are the characteristics of a single particle?

Particle shape

This characteristic has a considerable impact upon the performance or processing of particulate materials.

Needle-shaped, rigid

How to know if particle is acicular in shape?

Edgy, hard angles

How to know if particle is angular in shape?

Thread-like, non-rigid

How to know if particle is fibrous in shape?

Irregular-shaped

How to know if particle is granular/blocky in shape?

Regular-shaped

How to know if particle is spherical/cuboid/cylindrical/cone/cube in shape?

• Aspect ratio

• Sphericity

• Roundness

• Particle outline

What are the shape factors or parameters?

• sedimentation rate

• maximum length

• minimum length

• volume

• surface area

• weight

• sieve aperture

A particle can be characterized through a sphere with same ____?

• equivalent circle diameter

• feret’s diameter

• martin’s diameter

• shear diameter

What are the different diameters used in microscopy?

Equivalent circle diameter

circle with area equal to projected area of particle

Feret’s diameter

distance between two tangents on opposite sides of the particle

Martin’s diameter

length of the line which bisects the particle image

Shear diameter

particle width obtained using an image shearing device

Aspect ratio

• ration of the width to the height of an image of a solid body

• normalized ______ varies from approacing zero for a very elongated particle, such as a grain in a cold-worked metal, to near unity for an equiaxed grain

Sphericity

it is the measure of degree of closeness of the shape of a particle to the perfect spherical particle

0.873

What is the sphericity of cylinder?

0.806

What is the sphericity of a cube?

0.47

What is the sphericity of a cuboid with 1:2:3 dimensions?

0.7-0.9

What is the sphericity of activated carbon? which happens to be the same with silica gel?

0.86, 0.66

What is the sphericity of sand?

0.84

What is the sphericity of common salt?

Particle Outline

• it provides information about properties such as surface roughness

• for calculating ______ diameter, a concept known as the convex hull perimeter is used

Convex hull perimeter

the total length of the boundary of the smallest convex polygon that encloses a given set of 2D points

• convexity

• solidity

• circularity

On determining the convex hull perimeter, parameters based on it can be defined, such as _____

Convexity

convex hull perimeter / actual perimeter

Solidity

area bound by actual perimeter / area bound by convex hull perimeter

Circularity

actual perimeter / perimeter of an equivalent area circle

Circularity

What is the most commonlyused parameter in determining the convex hull perimeter?

Geldart Powder Classification

• It is a classification method that categorizes solid particle into 4 groups based on their fluidization behavior when suspended in a fluid

• determined by particle size (average diameter) and density difference between the particle and the fluid

Group C

the geldart classification which describes particles as cohesive or very fine with particle sizes ranging from 20 to 30 micrometers (ex: flour, fly ash)

hardly used

Group A

the geldart classification which describes particles as aeratable or smooth fluidization with sizes ranging from 30 to 100 micrometers (ex: Fluid Catalytic Cracking catalyst)

Group B

the geldart classification which describes particles as bubbly or sand-like with sizes ranging from 100 to 800 micrometers (ex: glass beads, sand)

Group D

the geldart classification which describes particles as spoutable or large with sizes ranging from more than 1 mm (ex: grains, coffee beans, pellets)

1. Ultra-fine powder

2. Superfine powder

3. Granular powder

4. Granular solid

5. Broken solid

Five categories of powder according to Richards and Brown (1970)

Zeta Potential

• the measure of the magnitude of the electrostatic charge repulsion or attraction between particles in a liquid suspension

• one of the key parameters known to affect dispersion stability

• can be applied to improve the formulation of dispersions, emulsions, and suspensions

Smoluchowski equation

The zeta potential is estimated by what equation?

• higher zeta = colloidal particles show good dispersibility as electrostatic repulsion becomes stronger

• as zeta approaches 0 = particles become more unstable and are likely to aggregate

What is the significance of zeta potential?

Rapid coagulation and flocculation

What is the stability behavior of the colloid if the zeta potential is from 0 to (+-) 5 mV?

Incipient instability

What is the stability behavior of the colloid if the zeta potential is from 10 to (+-) 30 mV?

Moderate stability

What is the stability behavior of the colloid if the zeta potential is from 30 to (+-) 40 mV?

Good stability

What is the stability behavior of the colloid if the zeta potential is from 40 to (+-) 60 mV?

Excellent stability

What is the stability behavior of the colloid if the zeta potential is fmore than (+-) 61

Slurry

a mixture of a solid and a liquid

Paricle size distribution

• describes the population of particles in a particle mixture

• necessary to know the mean size of particles and the spread of sizes

• may be expressed as frequency distribution curves or cumulative curves

Single peak

What will be the behavior of the curve for the particle size distribution of naturally occurring materials?

Peaks are as many as components in mixture

What will be the behavior of the curve for the particle size distribution of mixture of materials?

The curve may have more peaks

What will be the behavior of the curve for the particle size distribution if the particles are formed by crushing larger particles?

Cumulative distribution

• the integral of the frequency distribution

• denoted as F, then frequency distribution is dF/dd

number or surface, or mass or volume

The distribution can be by either ____.

Mass distribution

• the same as volume distribution (particle density does not vary with size)

ASTM E 11 test Sieves

What is the standard for segregating particles based on size?