basic consideration in process equipment design

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Basic Consideration in

Process Equipment Design

Dr. A.K. Sharma


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Introduction

Setup of new plant and modification ofexisting units or expansion involves bothtechnical and economic evaluations.

Knowledge of the various technical subjects

such as unit operations, process design,equipment design, thermodynamics, reactionkinetics etc. is a prerequisite to theestablishment or development of any plant.

Of these the process along with theassociated equipment, governs the shapeand the size of the plant.


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Design

Two aspects:Structural design

Functional design

Structural design to withstand load, pressure andwhatever operating condition are, so knowledge of

material of equipment become importantStructural design includes: selection of material,

thickness/gauge, stress analysis, material characteristics,etc.

Functional design includes specification andselection of equipmentCapacity, Power, Matching other process equipment,

Operation and control, etc.


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The agro-food industry

Processing involves any type of value

addition to agricultural or horticultural

produce and also includes processes such

as grading, sorting, packaging which

enhance shelf life of food products.

The Industry provides vital linkages and

synergies between industry and agriculture.


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Difference in food and non food processing plants

Many of the elements of design are the same for food/agro

plants as they are for other plants particularly thoseprocessing industrial chemicals. However, there are manysignificant differences, basically in the areas of equipmentselection and sizing, and in working space design. Thesedifferences stem from the ways in which the processing of

foods differ from the processing of industrial chemicalsbecause offollowing considerations:

The storage life of foods is relatively limited and stronglyaffected by temperature, pH, water activity, maturity, priorhistory and initial microbial contamination levels

Very high and verifiable levels of product safety and sterilityhave to be provided

Foods are highly susceptible to microbial attack and insectand rodent infestation


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Difference in food and non food processing plants

Enzyme-catalyzed processes are used or occur in many cases. These,like microbial growth and fermentation are very sensitive to temperature,pH, water activity, and other environmental conditions

Many foods are still living organisms or biochemically active long afterharvest or slaughter

Living foods generate heat and consume and transform their ownsubstance at rates, which are strongly temperature dependent. Rates ofheat generation as functions of temperature for various F&V and forchickens

In some cases foods (e.g. ripening cheeses) contain active living micro-organisms, which induce chemical transformations for long periods oftime

Crop-based food raw materials may only be available in usable form ona seasonal basis. Therefore, design may involves the modeling of cropavailability

Raw material are highly variable and that variability is enhanced by theageing of raw material and uncontrollable variation in climatic conditions


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PROCESSING AND VALUE ADDITION

HARVESTED BIOMASS(RAW/FRESH FOOD MATERIALS)

CLEANINGGRADING

CONDITIONING

STORAGE(IF NEEDED)

PROCESSING

PRIMARY SECONDARY TERTIARY

PADDY INTO RICE RICE INTO RICE FLOUR COOKING OF RICE WHEAT INTO FLOUR TOMATO INTO KETCHUP MEAT PREPARATION PULSE INTO DAL DAL INTO BESAN TEA MAKING

AND SO ON AND SO ON AND SO ON

AT EVERY STAGE OF PROCESSINGVALUE IS ADDED TO THE PRODUCT

Flow diagram of value addition to the harvested biomass of plant and animal origin


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Processing? Combination of all forms of physical processing into a small number of

basic operations, which are called unit operations.

Agro-food processes may seem bewildering in their diversity, but carefulanalysis will show that these complicated and differing processes can bebroken down into a small number of unit operations.

For example, considerheating of which innumerable instances occur inevery agro-food industry. There are many reasons for heating and

cooling - for example, the baking of bread, the freezing of meat, the tempering of oils. But in process engineering, the prime considerations are

firstly, the extent of the heating or cooling that is required and

secondly, the conditions under which this must be accomplished.

Thus, this physical process qualifies to be called a unit operation. It is called'heat transfer'.

The essential concept is therefore to divide physical agro-foodprocesses into basic unit operations, each of which stands alone anddepends on coherent physical principles.

For example, heat transfer is a unit operation and the fundamental physicalprinciple underlying it is thatheat energy will be transferred spontaneouslyfrom hotter to colder bodies.


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Important unit operations in Agro-food industry

material handling,

drying and storage ,size reduction/milling,

heat transfer,

evaporation,contact equilibrium processes (which include

distillation, extraction, gas absorption, crystallization, andmembrane processes),

mechanical separations (which include filtration,centrifugation, sedimentation and sieving),

fluid flow and

mixing.


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M.V. Joshi2nd edition

MacMillan India Ltd


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Optimum process conditions

Appropriate material of construction

Strength & rigidity of components

Satisfactory performance of mechanismReliable method of fabrication

Ease of operation & control

Ease of maintenance & repairSafety requirement

Satisfactory performance & reliability of equipment


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Optimum process conditions (f)

Appropriate material of construction (f/s)

Strength & rigidity of components (s/f)

Satisfactory performance of mechanism (f/s)Reliable method of fabrication (s)

Ease of operation & control (f/s)

Ease of maintenance & repair (f/s)Safety requirement (f/s)

Satisfactory performance & reliability of equipment


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General Design Procedure

Specifying the problem precisely

Analyzing the probable solutions

Applying process principles and theory of

machines satisfying the conditions ofproblem

Selecting material & stress to suit processing

conditions

Evaluating & optimizing the design

Preparing drawing & specification


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MacMillan India Ltd

Chapter 1 Page 1-6


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Assignment 1

Functional Design

Ginger peeling


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Ginger peeling

Functional requirementProcess should remove as much skin from ginger

High peeling efficiency is associated with highmaterial loss

Peeling efficiency(X-Y)/X

Material loss[(Wb-X) - (Wa-Y)] / WbX-theoretical weight of skin on ginger, g

Y-Weight of skin removed by hand trimming, g

Wb-total weight of ginger before peeling, g

Wa-total weight of ginger after peeling, g


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machines satisfying the conditions ofproblem


conditions




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Traditional, advanced and modern practices

Rubbing between fiber i.e. gunny bags etc

Hand peeling with knife

Chemical methods i.e. caustic lyeFlash steam

Flame


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machines satisfying the conditions of

problem

Irregular shape & size

Cells underlying the skin contains essential gingeroil

Excessive or careless removal of peel will result in

damaging of these cells leading to the loss of theessential oil and its economical value

Rubbing between fiber i.e. gunny bags etc

Hand peeling with knife


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machines satisfying the conditions of

problem


conditions




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Ginger peeling machine-Brush type

Abrasion unit

Power transmission

system

Belt tensioner

Hopper and side cover Frame


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Ginger peeling machine-Brush type


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Ginger peeling machine-Brush typeSN Parts

1 Hopper2 Pulley

3 Plummer block

4 Side flap

5 Belt6 Brushes

7 Idler

8 Frame

9 V-Belt pulley10 V-Belt pulley

11 V-Belt pulley

12 Shaft


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Ginger peeling machine-Brush typeSN Parts Material

1 Hopper M.S.

2 Pulley C.I. 25

3 Plummer block C.I.

4 Side flap M.S. Sheet

5 Belt Canvas 30Wide

6 Brushes Steel 32Gauge

7 Idler G.I. Pipe 3

8 Frame M.S. Angle4x4

9 V-Belt pulley C.I. 30

10 V-Belt pulley C.I. 7.5

11 V-Belt pulley C.I. 20.3

12 Shaft M.S. 2.54Dimensions in CM


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Abrasion Unit:

Two Endless belts

370x30x1 cm giving

effective abrasive

surface area of 135x30each, which mounted

on a 25 cm diameter

and 35 cm wide case

iron flat pulleys. The

brushes were made by

threading 20 steelwires of 32 gauge at a

spacing of 1.9x1.9 cm,

and 2 cm length


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Equipment classification

3. Group involving rotational motion:

Consist equipment or component where a

rotational motion is necessary to satisfy

process requirements. A drive system and

power supply are essential features.Consideration of torque, dynamic stresses,

apart from other loading conditions form the

basis of design


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Power for rotational motion

Often involves assessment of power

requirements. In arriving at the maximum

horse power an analysis should be made of

the mechanical operation of the equipment in

terms of torque at the motor shaft, and alsothe speed requirements


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Power for rotational motion

Torque

Starting torquerequired to overcome static friction and produce motion

Accelerating torquerequired to accelerate the driven equipment to full speed

Running torquerequired to drive the equipment or machine under normal

conditions at a specified speed

Speedat constant speedat two or three speeds

at variable speeds


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MacMillan India Ltd

Chapter 1 Page 1-6


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Process?

A particular course of action intended to achieve a

result (Noun)

A sustained phenomenon or one marked by

gradual changes through a series of states (Noun)

Deal with in a routine way (Verb)

Subject to a process or treatment, with the aim of

readying for some purpose, improving, or

remedying a condition (Verb) "process cheese"; "process fruits"

Shape, form, or improve a material (Verb)


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M h d f i P Fl Ch


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Method for preparing Process Flow Chart

Flow charts are schematic

representation of theproduction process,

involving Various input resources,

Conversion steps (Unit

operations)Output and

Recycle streams.

The process flow may be

constructed stepwise i.e.

by identifying the inputs /output / wastes at each

stage of the process.

Raw material

Inputs Waste/ ByproductProcess Step 1

Inputs Waste/ Byproduct

Output

Process Step 2

M th d f i P Fl Ch t


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Method for preparing Process Flow Chart

Raw material



Output

Process Step 2

Raw material



Output

Process Step 2

Inputs include

raw materials,

water, steam,

energy (electricity,

etc)Process step/ Unit operation should be sequentially drawn

from raw material to finished product.

Intermediates and any other byproduct should also be

represented.

The operating process parameters such as temperature,

pressure, % concentration, etc. should be represented.

The flow rate of various streams should also be represented in

appropriate units like m3/h or kg/h.

In case of batch process the total cycle time should be

included.

Wastes/by-products could include solids, water,

chemicals, energy etc. For each process steps

(unit operation) as well as for an entire plant,energy and mass balance diagram should be

drawn.

Output of the

process is the final

product produced in

the plant.

Wh t P i Milli (C td)


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Wheat-Processing- Milling (Contd)



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HARVESTED BIOMASS(RAW/FRESH FOOD MATERIALS)

CLEANINGGRADING

CONDITIONING

STORAGE(IF NEEDED)

PROCESSING

PRIMARY SECONDARY TERTIARY

PADDY INTO RICE RICE INTO RICE FLOUR COOKING OF RICE WHEAT INTO FLOUR TOMATO INTO KETCHUP MEAT PREPARATION PULSE INTO DAL DAL INTO BESAN TEA MAKING

AND SO ON AND SO ON AND SO ON

AT EVERY STAGE OF PROCESSINGVALUE IS ADDED TO THE PRODUCT

Flow diagram of value addition to the harvested biomass of plant and animal origin

Estimated

valueadditions to

the raw food

materials

through

primary and

secondary/

tertiaryprocessing in

India are 75%

and 25%

respectively.


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U it ti & E i t


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Unit operations & Equipments

material handling,mechanical separations (sieving),

size reduction/milling,

drying


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basic consideration in process equipment design

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