Evaporation Technology

MESSO TECHNOLOGIES GROUP

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What is evaporation?

Industrial evaporation isemployed for the large-scale production of concen-trated solutions, playing acritical role in the manufac-ture of a variety of productsin the process industry,including organic and inor-ganic chemicals, specialityand fine chemicals, poly-mers, fertilizers, pulp andpaper, pharmaceuticals andfoods. Nowadays evapora-

tion is also widely used toproduce water and to treateffluents and waste waters,often allowing the recoveryof valuable products.

Scope of evaporation sys-tems is to concentrate asolution consisting of a non-volatile solute and a volatilesolvent (usually water) byevaporation of the last one,obtaining a thick liquor or acrystalline slurry or a distil-late.

Even if this principle isessentially a simple one,industrial evaporation tech-nology requires efficientand economically optimizedsystems, designed specifi-cally for the solution mediaconcerned.

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Technology and experience

Our expertise is based onthe realization of more thanone thousand facilities. Besideplants for crystallizationmany of them are evapora-tion plants, or complex sys-tems with integrated evapo-ration processes. Basing onour field experience, on ourknowledge of the chemicaland physical properties ofintermediate and finishedproducts, on the result oftests performed in our Re-search Center and on theuse of MESSO proprietarycomputer programs we areable to carry out the mostsuitable and cost-efficientplant concept for each indi-vidual customer and to mini-mize operating costs, irre-spective of whether theproject concerns:■ Production■ Regeneration■ Environmental protection

1Spin bath regeneration plant

2Vinasse concentration unit with potassium sulfate crystallization

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Our experience in crystalliza-tion makes us predestinat-ed for those cases, whereprecipitation will occur dur-ing an evaporation process.

Evaporator types

Depending on the composi-tion of the solution, its tem-perature-related behaviourand its viscosity, the encrus-tation properties of the dis-solved substances, and lastnot least the productioncapacity required, we equipour systems with variousevaporator types based onthe following main designs:■ Forced circulation

evaporators■ Natural circulation

evaporators■ Falling film evaporators ■ Horizontal tube

evaporators■ Flash evaporators

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Maximum

cost-efficiency

Special attention is directedto the relationship betweencapital expenditure andenergy costs – the factorsgoverning the profitabilityof a plant. Each plant isdesigned and individuallyadapted to the special con-ditions of the customer’sapplications.

Efficient processes

According to the availabilityand the cost of the energy,the process conceptswhich we employ are asfollows:■ Multiple-effect

evaporators■ Thermal vapour

recompression■ Mechanical vapour

recompression■ Combined processes■ Flash evaporation

Vinasse concentration unit with potassium sulfate crystallization,32 t/h evaporation

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Evaporator designs – the ideal type for each application

The selection of the mostsuitable evaporator for eachapplication is based on thechemical and physical prop-erties of the solution inquestion.

Forced circulation

evaporator

The universal type, used toconcentrate scaling and/orviscous liquors and whencrystallization is consequentto concentration.

In this equipment, concen-trating liquor is kept in circu-lation by a high flow pumpthrough the heat transfersurface (that can be exter-nal or internal) and evapora-tion of heated liquor takesplace in the vapour body byflashing.

According to requirements,circulation inlet to vapourbody can be central or tan-gential, submerged or notsubmerged. Special designis provided to concentratefoaming liquors.

External heater can be sin-gle-pass vertical or horizon-tal multi-pass.

Natural circulation

evaporator

Compact, straightforwarddesign; used for not scalingsolutions not leading tocrystallization. Suitable forthe low-to-medium concen-tration duty range. It mayhave internal or externalheat exchanger.

Falling film evaporator

In a falling film evaporator,liquor is distributed at thetop of the tubular heat ex-changer and flows down-ward creating a film. Theturbulence of the descend-ing film, created by thevapour generated by boiling,results in high heat transfercoefficients and reducedcontact times. There is nostatic head to affect thetemperature driving force,so that the unit can operate

at very low ∆T betweenheating steam and liquor.

Vapour-liquid separation isperformed at the bottom ofthe heater, in an integratedvapour body or in a separat-ed one, obtaining very lowentrainments.

Film mechanism and short residence time makes this evaporator best suitable to treat non-crystallizing solutions whichare temperature-sensitive,even if very viscous.

Horizontal tube

evaporator

It employs horizontal tubebundles as heat transfersurface. Heating mediumflows inside tubes and pro-cess solution is distributedover the tube bundle form-ing a film.

Suitable for non-crystallizingsolutions which are temper-ature-sensitive. High specif-ic heat transfer.

Flash evaporator

Evaporation takes place byadiabatic expansion, so thatno heating surfaces are con-tacting the concentratedprocess solution. Suitableto treat solutions containingscaling and crystallizing sub-stances.

When used as a ”multi-flash”, up to 30 stages, thenet energy input can bevery low.

Forced circulation evaporator with internal heat exchanger (Roberts type)

Natural circulation evaporator:short tube vertical with external heater

Vapours

Concentratedliquor

Thinliquor

Condensate

Heatingsteam

Phosphoric acid concentration, 42 t/h evaporation

Vapours

Concentratedliquor

Thinliquor

Condensate

Heatingsteam

Vapours

Heatingsteam

Condensate

Thinliquor

Concentratedliquor

Forced circulation evaporator with external heat exchanger

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Horizontal tube evaporator

Falling film evaporatoronce-through, with external vapour body

Vapour

Concentratedliquor

Thin liquor

Condensate

Heating steam

Falling film evaporator with external recirculation, integrated vapour body

Flash evaporator, horizontal design

Concentratedliquor

Vapours

Thinliquor

Vapours

Concentratedliquor

Thin liquor

Condensate

Heating steam

XXXXXXXXXXXXXXX

Vapours

Concentratedliquor Thin

liquor

Conden-sate

Heating steam

Evaporator type Fluid viscosity Fluid conditions accepted

Horizontal film very low (<20 mPa s) non-crystallizing, moderate scaling or fouling, heat-sensitive

Natural circulation low (<50 mPa s) non-crystallizing, salting, low scaling

Flash type medium (<100 mPa s) crystallizing, scaling

Forced circulation high (<300 mPa s) crystallizing, high salting, high scaling

Falling film very high (<1500 mPa s) non-crystallizing, low scaling, heat-sensitive

Flash evaporator, vertical designKey to select an evaporator according to viscosity

Concentratedliquor

Vapours

Thinliquor

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Energy saving

One of the outstanding fea-tures of MESSO evaporationsystems is the reduction ofthe production cost to theminimum. This is achievedby minimizing the energyinput relative to vaporizationcapacity and obtaining longand stable operating cycleswith minimal maintenance.

We are able to meet thespecific requirements andsatisfy the conditions ofeach application by select-ing the most suitableprocess design.

Multiple effect

In multiple-effect configura-tion, vapours generated ineach evaporator body areused to heat the following.Last effect is maintained at high vacuum and itsvapours flow to a final con-denser. According to thevarious arrangements andproduct characteristics each effect can generate0.8 – 0.9 kg of vapour foreach kg of live steam condensed in first effectheater.

Co-current flow:solution and vapour flow in the same direction

Mixed flowwith the use of an air-cooled evapora-tor as last effect avoiding necessity ofcooling water

Concentratedliquor

Thinliquor

To condensationHeating steam

Concentratedliquor

Thinliquor

Heating steamAir out

Air in

Countercurrent flow:solution flows in the opposite direction to the vapour

Thinliquor

Concentratedliquor

To condensationHeating steam

Parallel flow:solution is fed in parallel to all stages

Concentratedliquor

Thinliquor

To condensationHeating steam

Pilot facility for the elimination of flue-gas serubber effluent water

Vinasse concentration unit with potassium sulfate crystallization,40 t/h evaporation

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Multiple stage flash evaporator

Thermal vapour

recompression

When high pressure steamis available, this can beused to compress a part ofthe vapours generated inthe evaporator to be re-used as heating medium.Balance is condensed orused to heat a followingeffect.

Mechanical vapour

recompression

In mechanical vapourrecompression (MVR) allthe vapours generated areincreased in pressure bymeans of a compressor tobe re-used as heating medi-um. No steam is needed(except for start-up) and nocooling water is required.

The compressor can becentrifugal, axial, volumetricor fan-type. MVR systemscan be arranged in single ormultiple-effect, single ormultiple stage.

Electrical consumption perkg of water evaporateddepends mainly on solutioncharacteristics (boiling pointelevation, heat transfercoefficient) and in generalcan vary from 15 to 40 kW/ton of evaporatedwater.

Flash evaporator

Flash evaporators are usually arranged in multiplestages, with generatedvapours preheating the feed solution.

Thermal recompression:single-effect

Mechanical vapour recompression:single-effect

Concentratedliquor

Heating steam

Thinliquor

To condensation

Mechanical vapour recompression:double-effect

Thermal recompression:triple-effect co-current

ConcentratedliquorThin

liquor

Motive steam

To condensation

Concentratedliquor

Motive steam

Thinliquor

To condensation

ConcentratedliquorThin

liquor

Electricalenergy M

Concentratedliquor

Electricalenergy

Thinliquor

M

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Phosphoric acid concentration plant,42 t/h evaporation capacity

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Products evaporated and concentrated in Messo evaporation facilities

Chemical and basic

process industry

■ Caustic soda■ Caustic potash■ Sodium chloride■ Potassium chloride■ Sodium chlorate■ Sodium carbonate■ Sodium sulphate ■ Sodium sulphite■ Ammonium nitrate ■ Ammonium sulphate■ Calcium chloride■ Magnesium chloride■ Sodium aluminate■ Pentaerythritol ■ Sodium formate■ Sulphuric acid■ Spin bath■ Caprolactam■ Phosphoric acid■ Superphosphoric acid■ Urea

The field of application ofMESSO evaporators is verywide, the following listbeing just indicative:

Life sciences industry

■ Citric acid■ Malic acid■ Tartaric acid■ Glucose■ Dextrose■ Fructose■ Erythritol■ Corn steep water■ Liquid sugar■ Distillery and yeast

vinasses ■ Corn stillages■ Vitamin C■ Monosodium glutamate ■ Amino acids■ Fish stick-water■ Gelatine■ Milk and whey

Environment protection

■ Landfill leachates■ Effluents from flue gas

scrubbers■ Cooling tower and

power plants blow-down■ Pharmaceutical waste

water■ Radioactive effluents■ Any liquid waste

reduction by concentration

7608_05

_2003

MESSO S.A.9, Av. du Val de Fontenay94132 Fontenay-sous-BoisFrancePhone (+33/1) 45 14 01 23Fax (+33/1) 48 75 02 12eMail: messo@messo.fr

MESSO AGBuerglistrasse 298401 WinterthurSwitzerlandPhone (+41/52) 2 62 52 00Fax (+41/52) 2 62 52 06eMail: contact@messo.ch

MESSO-CHEMIETECHNIK GmbHFriedrich-Ebert-Strasse 13447229 DuisburgGermanyPhone (+49/20 65) 90 30Fax (+49/20 65) 90 32 99eMail: info@messo.net

Bio-Ingenieurtechnik GmbHHans-Weigel-Strasse 204319 LeipzigGermanyPhone (+49/3 41) 2 57 54 20Fax (+49/3 41) 2 57 54 00eMail: sekretariat@bioingenieur.de

MESSO Inc.563 North Oak StreetHinsdale, IL. 60521USAPhone (+1/708) 6 72 10 68Fax (+1/708) 6 72 10 67eMail: t.fakatselis@messo.net

MESSO Italia S.r.l.Via E. Gadda, 320063 Cernusco sul NaviglioItalyPhone (+39/02) 9 24 00 46Fax (+39/02) 9 24 10 11eMail: messoitalia@libero.it

Range of Products

Crystallization andevaporation technolo-gies for the chemical,pharmaceutical andfood processing indus-tries, e.g.:(Entire technology con-cepts, based on precipita-tion, evaporation, crystalliza-tion)

■ Common salt productionplants

■ Reaction crystallizationplants for severalbase/acid reactions

Plants for environmen-tal protection (Based on precipitation, evaporation, crystallization)

■ Pickling bath liquor recy-cling plants

■ Spin bath regenerationplants

■ Landfill leachates concen-tration plants

■ Industrial waste waterelimination plants

■ Treatment plants for slagsfrom the secondary alu-minium industries

■ Vinasse concentration

Plants for chloralkalitechnology(Based on various unit oper-ations)

■ Chloralkali elektrolysisplants

■ Chlorine processing andhandling plants

■ Brine preparation andpurification plants

■ Production of inorganicchemicals

Plants for biologicalprocess technology forthe chemical, pharma-ceutical and food pro-cessing industries, e.g.:

■ Citric acid productionplants

■ Radical vinegar productionplants

■ ß-Carotin productionplants

MESSO TECHNOLOGIES GROUP