Towards intensified separation processes in gas/vapour ... 2013_Kenig.pdf · Liège, 15.11.2013...

Liège, 15.11.2013

Chair of Fluid Process EngineeringProf. Dr.-Ing. Eugeny Kenig

Towards intensified separation processes in gas/vapour-liquid systems

Liège, 15.11.2013

Chair of Fluid Process Engineering

Why intensification? - Requests through global changes

Fast population growth

Rising life expectations

Rising life standards

Change in the way and intensity of communication („open World“)

Scarcer resources, price escalation

Rising environmental awareness of the society

More energy!

Change in energy policy Impact of Process Industries!

„Efficient“ energy, clean energy!

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Why Intensification? – Possibilities available

New materials

New manufacturing technologies

New investigation tools, both experimental and theoretical

New communication culture

Progress in the computer technology

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Why Intensification? – Possibilities available

New materials

New manufacturing technologies

New investigation tools, both experimental and theoretical

New communication culture


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Revolutionary improvements in power, memory capacity, data transfer,

operability, comfort

Advances in numerical data processing, new experimental methods (e.g.,

optics, tomography, nuclear magnetic resonance spectroscopy)

Powerful numerical methods und software tools

Facilitated/automated simulation steps

User friendly pre-processing and post-processing

Significant progress in numerical simulation of several processes

This is the factor that makes fast progress of process engineering possible!

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What is PI?

A simple definition:

PI = „any chemical engineering development that leads to a substantially smaller, cleaner, and more energy efficient technology“

Stankiewicz & Moulijn, Chem. Eng. Progress, 96 (2000)

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Idea:

To get the maximum out of any apparatus, tool or process

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PI from industrial point of view

Anticipated advantages/aims

+ Simplified process arrangement+ Smaller equipment/smaller units+ Increased safety+ Decreased energy consumption+ Decreased operational costs+ Shorter „Time to market“+ Decreased waste/side products+ Better company image

Barriers

- Reliability of conventional technology

- Risk due to lack of precedent- Expensive new pilot plant facilities- Concerns about safety and control- Knowledge about how and where

to intensify- Lack of validated PI units- Missing criteria to evaluate PI- Often more complex modelling

Stankiewicz & Moulijn, Re-engineering the chemical processing plant, Marcel Dekker, 2004;

Lutze et al., Chem. Eng. Process. 49, 2010

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Ways towards PI and their feasibility

Integration

Miniaturisation and modularisation

Application of innovative driving forces

(e.g. microwaves)

…

Rising complexityDeep understanding of the basic phenomena and their interactions is necessary

Possible, largely thanks to the significant progress in the computer technology

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Ways towards PI and their feasibility

Integration

Miniaturisation and modularisation

Application of innovative driving forces

(e.g. microwaves)

…

Rising complexityDeep understanding of the basic phenomena and their interactions is necessary

Possible, largely thanks to the significant progress in the computer technology

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PI via integration

What can be combined:

Single process stepsSeparation unitsColumn internalsHeat streamsFurther elements/components/functions

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PI via integration



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Integration of single process steps - reaction and separation

distillation

stripping

extraction

absorption

Classicalseparations

Reactive separations

reactive distillation

reactive stripping

reactiveextraction

reactiveabsorption

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Reactive distillation

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Reactive distillation: what for?

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Solution possibilities:1. conventional process: reactor + distillation column2. reactive distillation

Problem:

reaction (equilibrium limited)

products C and D required in pure formA + B C+ D

in addition: distillative separation possible and desired

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Reactive distillation as an alternative

Reaction

Separation

Traditional separation

Reactive distillation

Improved conversion

Increased selectivity

Direct heat integration

Separation of azeotropic and close boiling mixtures

Suppression of undesired side reactions

Reduced capital investment and operating cost!

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Synthesis of methyl acetate: Conventional scheme

acetic acid + methanol118 °C 65 °C

methyl acetate + water57 °C 100 °C

Kx 5

Binary azeotropesxMeAc[-] TB [°C]

MeAc - H2O 0,93 56,8

MeAc - MeOH 0,68 53,9

After Siirola, AIChE Symp. Ser., 1995

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Synthesis of methyl acetate: Reactive distillationDevelopment of a RD-processwith the goal to solve a) conversion problems (chem. equilibrium)

b) separation problems (MeOH-MeAc-

azeotrope)

RD-column with 4 zones:a) Reactive zone (MeAc-building)

b) Extractive distillation (MeOH-MeAc -

azeotrope is broken with the aid of HAc)

c) Rectifying section (HAc-separation)

d) Stripping section (MeOH-separation)

Sulphuric acid(catalyst)

Methyl acetate

Acetic acid

Methanol

Water(+ sulphuric acid)

Methyl acetateaccumulation (c)

Water extraction (b)

Reaction zone (a)

Methanol stripping (d)

Agreda et al., Chem. Eng. Progress, 1990

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Synthesis of methyl acetate: Reactive distillation

Conventional scheme:

9 columns + 1 reactor

RD:

1 RD-column

up to 99% product purity

significant equipment reduction

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Agreda et al., Chem. Eng. Progress, 1990

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Possible applications

Esterifications and transesterifications (e.g. MeAc, fatty acid esters, ...)

Etherifications (e.g. MTBE, TAME, ETBE, ...)

Alcylations (e.g. cumene from benzene and propylene)

Aldol condensation (e.g. DAA from acetone)

Hydrolysis of epoxides (e.g. ethylene glycol from EO)

......

Separation of closely boiling mixtures (e.g. m- and p-xylol)

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Reactive distillation: Reaction types

Homogeneously catalysed(e.g., strong inorganic acids)

Heterogeneously catalysed(e.g., ion exchangers)

High product purity

No special materials

No corrosion problems

Determined reaction zone

Catalyst poisoning

Temperature limit (130°C)

Difficult catalyst exchange

Low costs

Simpler simulation

Corrosion problems

Product contamination

Sometimes necessity of catalyst separation

Indefinite reaction zone

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Reactive distillation columns

MONTZ-PAK Type BSH-400

Sulzer KATAPAK-SP

Catalyticpackings(“sandwich”-formKATAPAK-SPby SulzerChemtech)

Structured packings(metal, plastic,gauze wire)

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Catalytic internals

Requirements:

sufficient residence timeplug-flow when consecutive reactionssufficient separation efficiencylow pressure droptemperature resistance

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Catalytic internals

Sulzer Katapak-SP 11 Sulzer Katapak-SP 12

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Behrens, Dissertation, Delft, 2006

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Reactive absorption

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Reactive absorption: What for?

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Some examples:

Gas purification (e. g. separation of CO2 and H2S from industrial waste gases)Manufacturing of chemicals (e.g. nitric acid, sulphuric acid)Drying (e. g. air drying)Removal of foul gases…

Numerous applications in food, paper, cement industries, naphtha and fuel sectors, emission treatment, etc.

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Reactive absorption: Important features

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Contrary to physical absorption, there is no need in

high partial pressures

significant physical solubility of gaseous species

Instead, a high solubility of the conversed species (product of the reaction

with the absorbed component) is advantageous

The effect of chemical reactions is favorable at low gas-phase concentrations

Compared to RD:

independent fluxes

often fast reactions – mass transfer is a crucial issue!

electrolyte systems, ion components

hardly any catalyst application

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Reactive absorption: A typical example

SO2-absorption plant in a maleic anhydride production factory

Multiplied reactions

Simplified flowsheet of a (reactive) closed-loop absorption/desorption

(wash) unit

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Reactive stripping

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Reactive stripping: what for?

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A supplementary operation to reactive absorption (homogeneous)

An alternative to reactive distillation (catalytic, heterogeneous)

a stripping (inert) gas is involved

temperature can be below boiling point

can be carried out both in co-current and counter-current mode

efficient removal of inhibiting components out of reaction zone

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Reactive stripping

Stripping in the counter-current mode and concentration profiles

A finned monolith:A photo and a simplified cross-section representation

Esterification of 1-octanol with hexanoicacid (with cumene as solvent) towards octyl hexanoate and water

Beers et al., Catalysis Today, 66 (2001)

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Hybrid separations

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An example of hybrid separations – Distillation & Membranes

Production of ethanol:

First step: Separation of a fermentation liquor in a combination of distillation & stripping

Distillate: a binary mixture ethanol/water Subsequently: azeotrope breaking via a combination of distillation &

vapour permeation

PI by coupling of unit operations

Keller et al., Chem. Ing. Techn. 83, 2011

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PI by coupling of unit operations

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Distillation & Stripping

(azeotrope)EthanolWaterFermentation

liquor

Water

Distillation & Vapour permeation

Ethanol

RecycleEthanolWater


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PI by coupling unit operations


+ Lower energy consumption+ Possibly enhanced product quality+ Avoiding entrainers+ Applicable to separation of close boiling and azeotropic mixtures

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- Insufficient long-term stability of membranes- Missing design methods for this complex process conjunction

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PI via integration



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Integration of separation units

Conventional column sequence to separate a ternary mixture

ABC

BA

C

BC1 2

Energy-integrated column(Petlyuk configuration)

ABC

A

C

B1 2

Problem: High energy demand

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Dividing wall column conceptIntegration of the Petyluk configuration in one column → dividing wall column

Liquid phase distribution

ABC

C

B

A

Pre-fractionator

Main column

Vapour distribution

Dividing wall

+ Lower equipment cost+ Lower energy consumption as

compared to common column configurations

+ More compact equipment+ Possibility to reach sharp separation of

a ternary mixture within only one column

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- More complex modelling, design and control

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PI via integration



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Integration of integrated units

distillation

Classicalseparations

Reactive separations

reactivedistillation

„Coupled“ separations

dividing wall column

reactive dividing wall column

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PI via integration



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Integration of internals - sandwich packing

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Internals as integration elements Structured packings with lower geometric

surface (de-entrainment layer) Structured packings with higher geometric

surface (hold-up layer)

Hold-up layer

De-entrainment layer

Gas

Liquid

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Integration of internals - sandwich packing

spray layer

floodedhold-up layer

gas

liquid

de-entrainment layer

hold-up layer

downcomers

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PI via integration



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Heat integration in distillation

Due to high energy consumption, distillative separation covers 40-70 % of investment & operating costs of a typical chemical plant

Distillation is inefficient from the energetic point of view, since the heating energy for the reboiler is supplied at high temperatures, whereas at the condenser, it is removed at low (mostly useless) temperature level

Improvement potential: Application of heat pipe principle, e.g. Vapour recompression column Heat integrated distillation

Bruinsma et al., Chem. Eng. Research & Design 90, 2012

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An example of heat integrated distillation columns (HIDiC)

Two units with different pressure levelHigh pressure region can be used to heat the low pressure region

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- High investment costs- Complex construction - Problems with process control

+ Reduction of total required energy

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Compressor

Feed

Top product

Heat transfer

Bottom product

Rectifying sectionStripping section

Throttle valveCompressor

Top product

Bottom product

Feed

Integrated unitExplanation of the function

Throttle valve

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PI via integration



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Further integration possibilities

Method: Mechanical mixer is replaced by a static mixerAim: a compact and energy-efficient method to mix fluids or to bring them in contactExample: static mixer reactor of Sulzer, with heat transfer tubes used as mixing elementsApplication: Processes, in which mixing and intensive heat supply/ removal must be performed simultaneously, e.g. in nitration or neutralisation reactions

Fa. Sulzer, static mixer reactor

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An example of a mixer reactor

Stankiewicz & Moulijn, Chem. Eng. Progress, 96 (2000)

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PI: important questions from industry

When is PI economically reasonable? Is the new variant too expensive?

Which process step should be intensified?

Which equipment is required?

Which criteria must be involved to evaluate different PI-options?

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Future problems in PI

New and reliable materials (e.g. catalysts or membranes) to extend feasible operational windows

Development of suitable tools for automatisation of process steps, for instance in integrated separation processes

Relevant modelling approaches

Design methods for complex process and unit combinations

….

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Process intensification: Concluding remarks

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PI is an inherent feature of today’s life of process industries, mostly due to the computer technology progress

Integration is one of the main ways towards PI

Integrable are single process steps, units, internals, heat streams, functionalities, etc.

Many integrated applications already exist

Integration is on its way to maturity: some problems have to be solved in order to make it fully convincing concept for industry

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Process intensification: Concluding remarks

Idea:

To get the maximum out of any apparatus, tool or process

„No more of the old formula: Let’s make it a foot bigger in diameter and 5 ft. higher just for good luck“

- Walter G. Whitman (1924)

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Thank you for your attention!

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Towards intensified separation processes in gas/vapour ... 2013_Kenig.pdf · Liège, 15.11.2013...

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