Separation Equipment Part 2

To identify different separation equipment, its parts and its function

To identify the processes involved in every equipment

Objectives

Separation Processes

•Filtration•Sedimentation•Centrifugation•Distillation

Filtration is the removal of solid particles from fluid by passing through a medium on which the solids are deposited.

Filtration

Filtration

CAKE FILTERSCake filters separate relatively large amounts of solids as a cake of crystals or sludge.

Types of Filtration

Types of Filtration

Cake Filters

CLARIFYING FILTERSClarifying filters remove small amounts of solids or liquid droplets from either liquids or gases. The particles are trapped inside the filter medium or on its surface.

Types of Filtration

Types of FiltrationClarifying Filters

CROSS-FLOW FILTERSIn a cross-flow filter the feed suspension flows under pressure at a fairly high velocity across the filter medium.

Types of Filtration

Types of Filtration

Cross-flow Filters

Filtration Equipment

Bed FilterA layer of sand or gravel on the bottom of a reservoir or tank, used to filter water or sewage.

Bed Filter Process1.Water is introduced at the

top wherein some design has baffles which spreads the water out.

2.The clarified liquid is drawn out at the bottom.


Filtration EquipmentBed Filter


Plate-and-Frame Filter Press

An alternate assembly of plates covered on both sides with a filter medium, usually a cloth, and hollow frames that provide space for cake accumulation during filtration.

Plate-and-Frame Filter Press Process

1.Slurry is pumped and fills the chambers at a high flow rate and low pressure which gradually builds-up as the cake gets thicker.

2.When pressure reaches 6-7 bars wash water is pumped through the filter cake.

3.Air blowing is applied to reduce cake moisture.


Plate-and-Frame Filter Press Process

4.The drip trays open and are ready for cake discharge.

5.The hydraulic plate closing piston retracts together with the follower.

6.The shuttle shifter moves the plates one by one towards the follower and the cake discharges.

7.The drip trays close and are ready for the next cycle.


Filtration EquipmentPlate-and-Frame Filter Press


Leaf FilterAlso called tank filters, they

consist of flat filtering elements (leaves) supported in a pressure shell. The leaves are circular, arc-sided, or rectangular, and they have filtering surfaces on both faces.

Filtration EquipmentLeaf Filter Process1.The slurry enters and the

shell is filled, and filtration occurs on the leaf surfaces.

2.Filtration is allowed to proceed only until a cake of the desired thickness has formed.

3.Air or gas is blown and the slurry heel that surrounds the leaves is pushed and displaced downwards.

4.Cake is dried and discharged.

Filtration EquipmentLeaf Filter

Continuous Rotary Vacuum Drum Filter Process

1.The drum is pre-coated.2.The drum rotates through the liquid and the vacuum sucks liquid and solids onto the drum pre-coat surface.3.The solids adhere to the outside of the drum.4.It passes a knife, cutting off the solids.


Filtration EquipmentContinuous Rotary Vacuum

Drum Filter

Filtration EquipmentContinuous Rotary Disk

FilterIt consists of concentric vertical disks

mounted on a horizontal rotating shaft.

Continuous Rotary Horizontal Filter

Vacuum filter with the rotating annular filtering surface divided into sectors

Both vacuum filters operate on the same principle as the vacuum rotary

drum filter.

Both vacuum filters operate on the same principle as the vacuum rotary

drum filter.


Continuous Rotary

Disk Filter

Continuous Rotary

Horizontal Filter

Filter Media• it must remove the solids to be filtered

from the slurry and give a clear filtrate• the pores should not become plugged so

that the rate of filtration becomes too slow

• it must the filter cake to be removed easily and cleanly• it must have sufficient strength and must be chemically resistant to the solutions used

Filter Aids• It is used as a precoat• It can also be added to the slurry

before filtration

DESIGN PROBLEM

ROTARY DRUM FILTER DESIGN

Design an appropriate rotary drum filter for the removal of suspended solids remaining in the production of rice bran oil. Determine the

tank capacity, tank dimensions, dry cake weight, form time, cake moisture correlation, dry time, cycle time based on rate-controlling

factors, over-all scale-up factor, design filtration rate, drum volume, drum dimensions, drum area, actual dry time, vacuum capacity and power requirement for the rotary drum filter. Feed entering the filter amounts to 1, 925 kg/day with the following properties:

ρ = 1.1018 g/mL = 1, 101.8 kg/m3

Parts of Rotary Drum Filter

1. Feed entering = 1, 925 kg/dayρ = 1.1018 g/mL = 1, 101.8 kg/m3

2. Equipment physical factors:Maximum effective submergence = 30%Maximum apparent submergence = 35%Portion of cycle under vacuum = 80%Percent of cycle arc required for cake discharge = 20%Maximum percent of cycle for dewatering (drying) = 50%

Data and Assumptions

drumdrying zone (50%)

submergence (forming) zone

(30%)

Discharge and

resubmergence zone

(20%)


3. Scale-up factors (Perry’s Handbook)On rate = 0.8 On area = 0.8

On discharge = 0.954. Minimum cake thickness (Perry’s

Chemical Engineers’ Handbook) is 0.6 mm.

5. Cake moisture content is 25 weight%.6. Ratio of tank length to diameter is 2:1.7. The drum occupies 80% of the total

volume of the tank8. Ratio of drum length to diameter is 2:1


1. 25% safety factor2. 85% filling capacity for the filter tank3. Material of Construction will be

Carbon Steel Alloy

Design Consideration

Factors to be Considered in the Continuous Rotary Drum Filter Design1. Tank Capacity2. Tank Dimension: Length and

Diameter3. Dry Cake Weight4. Form Time

Factors to be Considered in the Continuous Rotary Drum Filter Design5. Cake Moisture Correlation6. Dry Time7. Cycle Time Based on Rate-Controlling

Factors8. Overall Scale-up Factor9. Design Filtration Rate10.Drum Volume11.Drum Dimension: Diameter and Length12.Drum Area13.Actual Dry Time14.Vacuum Capacity15.Power Requirement

SedimentationThe separation of a dilute slurry or

suspension by gravity settling into a clear fluid and slurry of higher solids is called sedimentation.

Methods of Classification

Sink-and-Float Method-takes advantage on the density differences of the particles

Differential Settling Method-takes advantage on the settling velocities of the particles

Sedimentation Equipment

Simple Gravity Settling TankIt is a box-like chamber, with the inlet and outlet streams way up at the top, and as the fluid flows through, the particles fall out.

Simple ClassifierThe design is similar to that of the

straight gravity settling tank, except that the bottom half is divided into several equal partitions wherein the coarse particles get trapped in the first chamber, the intermediates get trapped in the middle partitions, and the fine particles, the dust, gets captured in the last section.

Sedimentation EquipmentClassifiers

Sedimentation EquipmentClassifiersThe Spitzkasten chamber

A series of conical vessels of increasing size is set up in the direction of flow. As the slurry enters the first vessel, the coarse particles get trapped, and the overflow continues on to the next, where more separation takes place.


Classifiers Simple

Classifier

Spitzkasten

Classifier


Clarifier/ ThickenerIt is used to concentrate suspended solids by gravity settling so that a steady-state material balance is achieved, solids being withdrawn continuously in the underflow at the rate they are supplied in the feed.

DESIGN PROBLEM

GRAVITY SETTLING TANK DESIGN

A gravity settling tank is to be designed for wastewater with a flow rate and density of 1223.52 kg/hr and 1500 kg/m3 respectively. The influent

wastewater has the following characteristics:

BOD5 content = 35.62 mg/LSuspended solid content 0.3018 kg/hrThe sedimentation tank is rectangular.

Parts of Gravity Settling Tank

1. The flow rate of influent wastewater is 1223.52 kg/hr based from the coagulation tank.

2. The density of wastewater is assumed to be equal to that of water, which is 1500 kg/ m3.

3. The average characteristics of the influent wastewater:– BOD5 content = 35.62 mg/L– Suspended solid content 0.3018 kg/hr– The sedimentation tank is rectangular.


1. Tank Capacity2. Tank Dimensions3. Sludge Removed4. Suspended Solids5. Amount Of Effluent6. Scour Velocity

Factors to be Considered in the Gravity Settling Tank Design

1. Tank CapacityV = 1223.52 kg/hr (2hr)

V = 2.45 m3

With 30 % allowanceV = 2.45 m3 (1.3)V = 3.18 m3

2. Tank DimensionV = LWH3.18 m3 = H (2H) (4H)3.18 m3 = 8H3

H = 0.74 mW = 1.47 m

L = 2.96 m

Design Computation:

3. Sludge Removed = 0.7 (1223.52 kg/hr) (35.62 mg/L)

Sludge Removed = 30.51 kg/hr

4. Suspended SolidsSuspended Solids = SS in – SS red= 0.3 (0.3018 kg/hr) = 0.91 kg/hr 5. Amount of EffluentEffluent= 1223.52 kg/hr- (30.51

kg/hr / 0.125) Effluent = 979.44 kg/hr

1L

1X106

1000L

1m3

6. Scour Velocity

Vh =

Where:Vh = horizontal velocity that will produce

scourk= scour constant s = specific gravityg= 9.8 m/s2 d = diameter of

suspended particlesf= Darcy Weisbach friction factor

Vh=

Vh = 0.087 m/s

8k

s 1 gd

f

0.5

8.06 X 0.06 X

1.4 1

9.81 m

s2

X 0.0001 m

0.025

0.5

Capacity: 3.18 m3

Sludge Removed: 30.51 kg/hr

Dimension:Width: 1.47 mHeight : 0.74 mLength: 2.96 m

Effluent Characteristics

Suspended Solid: 0.91 kg/hr

Amount of Effluent 979.44 kg/hr

Scour Velocity 0.087 m/s

Centrifugation

A mechanical method of separating immiscible liquids or solids from liquids by the application of centrifugal force.

Types of Centrifugation

Centrifugal Filtration-A centrifugal force is used

instead of a pressure different to cause the flow of slurry in a filter where a cake of solids builds upon a screen.

Centrifugal Sedimentation-It is the separation of a dilute

slurry or suspension using centrifugal force into a clear fluid and slurry of higher solids

Centrifugation Equipment

Tubular Bowl CentrifugeThe centrifugal force acts on the liquid entering and separates the two liquids according to their specific gravities. The lighter liquid forms the inside layer and heavier liquid forms the outer layer.

Disk Bowl Centrifuge


It consists of a vertical, rotating bowl with an integral disc stack.

Disk Bowl Centrifuge Process1.The feed enters the compartment at the bottom2.It travels upward through vertically spaced feed holes, filling the spaces between the disks.3.The holes divide the vertical assembly into an inner section, where mostly light liquid is present and outer section, where mainly heavy liquid is present.


Centrifugation EquipmentTop-Suspended Centrifuge A common type of batch centrifuge in industrial processing is the top-suspended centrifuge.1.Feed slurry enters the rotating basket through an inlet pipe or chute.2.Liquor drains through the filter medium. The cake is then spun to dry.3.The motor is shut off. With the basket slowly turning, the solids are discharged by cutting them out with an unloader knife, which peels the cake off the filter medium.4.The filter medium is rinsed clean, the motor turned on, and the cycle repeated.

Centrifugation EquipmentSuspendedBatchCentrifuge

Centrifugation EquipmentAutomatic Batch CentrifugeThe basket rotates at constant speed horizontal axis.1.Feed slurry, wash liquid, and screen rinse are successively sprayed into the basket at appropriate intervals for controlled lengths of time.2.The basket is unloaded while turning at full speed by a heavy knife that rises periodically and cuts the solids out with considerable force through a discharge chute.

Centrifugation EquipmentAutomatic Batch Centrifuge

Continuous Filtering CentrifugeA rotating basket with a slotted wall is fed through a revolving feed funnel. The purpose of the funnel is to accelerate the feed slurry gently and smoothly.


Centrifugation EquipmentContinuous Filtering Centrifuge

DESIGN PROBLEM

DUST COLLECTOR DESIGN

A dust collector is to be designed for an air flowrate, temperature and pressure are 150 m3/min, 350 K and 1 atm, respectively. The particles in the air have a

density of 1600 kg/m3. What are specifications of the said cyclone?

Parts of Dust Collector

1. The air flowrate, temperature and pressure are 150m3/min, 350 K and 1 atm respectively.

2. The particles in the air have a density of 1600 kg/m3.

3. The gas viscosity and gas density at 350 K are equal to 0.075 kg/m-hr and 1.01 kg/m3 respectively.

4. The conventional cyclone has a standard diameter of 1 meter. (7th ed. Perry’s Chemical Engineering Handbook; Air Pollution Control by C.D. Cooper & F.C Alley, 1986)


5. The size distribution are given from the table below

Particle size range, µm Mass Percent in size

range

0-2 1.0

2-4 9.0

4-6 10.0

6-10 30.0

10-18 30.0

18-30 14.0

30-50 5.0

50-100 1.0

1. Inlet Velocity2. Cut-point Diameter3. Overall Efficiency4. Cone Height5. Outlet Tube Diameter6. Dust Outlet Diameter7. Cyclone Height

Factors to be Considered in the Dust Collector Design

Distillation is a unit operation for separating mixtures based on differences in their volatilities in a boiling liquid mixture.

Distillation

Distillation

Simple distillation involves the production of a vapor by boiling the liquid mixture to be separated in a single stage and recovering and condensing the vapor. No liquid is allowed to return to the single-stage still to contact the rising vapors.

Types of Distillation

Types of DistillationTypes of Simple Distillation•Equilibrium or Flash Distillation-a liquid mixture is partially vaporized. The vapor is allowed to come to equilibrium with the liquid, and the vapor and liquid phases are then separated.

Types of Simple Distillation•Differential Distillation-liquid is first charged to a heated kettle. The liquid charge is boiled slowly and the vapors are withdrawn as rapidly as they form to a condenser, where the condensed vapor is collected.


Types of Simple Distillation•Simple Steam Distillation- method is often used to separate s high-boiling component from small amounts of non-volatile impurities.


Types of DistillationFractional Distillation

-It involves the returning of a portion of the condensate to the still.

-It is also known as distillation with reflux or rectification.

Azeotropic DistillationAny of several processes by which

liquid mixtures containing azeotropes may be separated into their pure components with the aid of an additional substance (called the entrainer, the solvent, or the mass separating agent) to facilitate the distillation.


Types of DistillationAzeotropic Distillation

• vertical shell where the separation of liquid components is carried out

• column internals such as trays/plates and/or packings which are used to enhance component separations

• reboiler to provide the necessary vaporization for the distillation process

• condenser to cool and condense the vapor leaving the top of the column

• reflux drum to hold the condensed vapor from the top of the column so that liquid (reflux) can be recycled back to the column

Distillation Equipment

Distillation Equipment

The performance of a distillation column is determined by many factors, for example:•feed conditions– state of feed– composition of feed– trace elements that can severely affect the

VLE of liquid mixtures•internal liquid and fluid flow•conditions state of trays (packings)•weather conditions

Factors Affecting Distillation Column Operation

END

FAUSTO, Joana Marie E..

Separation Equipment Part 2

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