evparation

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EVAPORATION

• HEAT TRANSFER COEFFICIENTS AND SINGLE EFFECT
  EVAPORATORS

By
T.Shivakumar B.Pharmacy Shiva.pharm
acist_at_gmail.com
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PROCESS DESCRIPTION

• OBJECTIVES
• CONCENTRATE SOLUTE
• RECOVER SOLVENT
• FORM CRYSTALS
• MECHANISM
• HEAT EXCHANGE WITH PHASE CHANGE
• BATCH OR CONTINUOUS

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DESIGN FACTORS

• SOLUTION FLUID VISCOSITY
• HEAT TRANSFER COEFFICIENTS
• PRESSURE DROPS
• SOLUTE SOLUBILITY
• SUPERSATURATED CONDITION
• MATERIALS (BIO-MATERIALS) MAY BE HEAT SENSITIVE
• DEGRADATION TEMPERATURE
• ELEVATED PRESSURE
• BOILING POINT ELEVATION

http//www.aai-csi.com/images/evaporator.jpg
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EVAPORATION DESIGN FACTORS

• HIGH TEMPERATURE REACTIONS
• FOAMING
• SCALING AND CORROSION

http//www.aquasant-mt.com/Foam.159.0.html?L1
http//www.champ-tech.com/images/products/pipe.jpg
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OTHER DESIGN FACTORS

• SPECIFIC HEAT
• HEAT OF CONCENTRATION
• FREEZING POINT VS. CONCENTRATION
• GAS LIBERATION
• TOXICITY
• EXPLOSION HAZARDS
• NEED FOR STERILITY

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EVAPORATION COMPARED WITH DISTILLATION

• SOLUTE IN EVAPORATION IS GENERALLY NON-VOLATILE,
  RELATIVE TO SOLVENT

http//www.novasep.com/technologies/img/evaporatio
n-graph2.gif
http//www.schoolscience.co.uk/content/4/chemistry
/petroleum/knowl/images/still.jpg
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EVAPORATION EQUIPMENT

• SUMMARIZED IN FIGURE 8.2-1

http//www.niroinc.com/html/evaporator/esys.html
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EVAPORATION EQUIPMENT

• FORCED CIRCULATION AND RECOMPRESSION UNITS

http//www.niroinc.com/html/evaporator/esys.html
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EVAPORATOR EQUIPMENT

• PLATE FRAME - CRYSTALLIZERS

http//www.niroinc.com/html/evaporator/esys.html
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OSLO TYPE CRYSTALLIZERS
http//www.niroinc.com/html/evaporator/esys.html
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OTHER CRYSTALLIZERS
http//www.niroinc.com/html/evaporator/esys.html
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THIN FILM EVAPORATORS

• USED FOR VISCOUS AND THERMALLY SENSITIVE MEDIA

http//www.artisanind.com/documents/pa_lecithin.pd
f
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INTEGRATED PLANT
http//www.niroinc.com/html/evaporator/flash-ppt/V
MPfcopy1.html
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EVAPORATOR CONFIGURATION

• SINGLE STAGE EVAPORATORS
• HEAT TRANSFER

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MULTI-EFFECT EVAPORATORS

• STEAM FROM ONE EFFECT IS THE HEAT SOURCE FOR THE
  SECOND EFFECT

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MULTI-EFFECT COUNTERFLOW CONFIGURATION

• FIGURE 8.2-3 FEED-FOREWARD
• PRESSURE IS REDUCED IN EACH STAGE
• FEED STEAM ENTER THE SAME STAGE IN THE TRAIN
• FIGURE 8.2-4 FEED-BACKWARD
• PRESSURE IS INCREASED IN EACH STAGE
• FEED STEAM ENTER FROM OPPOSITE ENDS OF THE TRAIN

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PARALLEL FEED

• SOLAR EVAPORATION SYSTEM

http//www.rio5.com/proceedings/Solar/da_Silva_et_
al_201-206.pdf
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EVAPORATOR HEAT TRANSFER

• OVERALL HEAT TRANSFER COEFFICIENTS SEE TABLE
  8.3-1
• NEED TO KNOW RANGE TO REVIEW QUOTED DESIGNS
• NOTE THAT PLATE FRAME CAN HAVE HIGHER
  COEFFICIENTS THAN SHELL TUBE.

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CHANGE OF PHASE HEAT TRANSFER

• SECTION 4.8 FOR SUMMARY OF MECHANISMS
• FIGURE 4.8-1
• CONVECTION
• NUCLEATE
• TRANSITION
• FILM

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HEAT TRANSFER COEFFICIENTS

• BASED ON ?T

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OTHER CORRELATIONS

• FOR EACH CONFIGURATION
• PERRYS PAGE 5-22
• HANDBOOK
• http//www.wlv.com/products/databook/ch5_3.pdf
• CONVECTIVE BOILING IN COILED TUBES
• http//www.graham-mfg.com/downloads/12.pdf
• BASED ON SURFACE
• http//www.energy.kth.se/index.asp?pnr10ID125l
  ang0

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SINGLE STAGE MODELS

• MASS AND ENERGY BALANCES

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MASS ENERGY BALANCES

• COMPONENT MASS BALANCE
• SYSTEM HEAT BALANCE

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OTHER DESIGN FACTORS

• LOWER EVAPORATION PRESSURE
• WILL INCREASE EFFECTIVE ?T
• LOWER EVAPORATOR AREA
• INCREASED SOLVENT CONDENSER AREA
• HIGHER VELOCITIES MIST ELIMINATION
• BOILING POINT ELEVATION
• REDUCES EFFECTIVE ?T WITH INCREASING CONCENTRATION

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BOILING POINT ELEVATION

• DÜRINGS RULE SOLUTION BOILING POINT IS
  LINEARLY RELATED TO PURE WATER NBPt AT PSYS
• FIGURE 8.4-2

http//www.nzifst.org.nz/unitoperations/unopsasset
s/fig8-3.gif
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ENTHALPY-CONCENTRATION

• HEAT OF MIXING EFFECTS
• NON-IDEAL

Dharmendira Kumar, M. Ashok Kumar, P.
Rajendran, M., Salt Effect on the Enthalpy of
Mixing of 1,4-Dioxane Acetic Acid at 303.15 K ,
J. Chem. Eng. Data (Article) 2003 48(6)
1422-1424.
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