Chemistry Equipment Sairem

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Agenda


1. What are microwaves?- Transverse electromagnetic waves- Frequency and wavelength- Electromagnetic spectrum- ITU allocated bands for ISM applications

2. Electromagnetic energy interactions with matter

3. Microwave energy vs. Other electromagnetic energy. Ionizing or non-ionizing?

4. Microwaves and their interactions with matter- Main parameters- Heating mechanisms- Classification of materials- The effect of wavelength (frequency) on heating homogeneity- Rates of heating for liquids and solids- Thermal effect

5. Microwave heating vs. Conventional heating

6. Microwave equipment for heating applications- Basic equipment- Multimode applicators- Single mode resonant cavities & standing wave formation

7. SAIREM’s microwave assisted chemistry/extraction

What are microwaves? Transverse electromagnetic waves


Electromagnetic waves propagated in free space have the electric and magnetic field perpendicular to each other and to the direction of propagation; they are known as transverse electromagnetic waves (TEM).

The plane of polarisation for a wave is, by convention, that of the electric field – vertical

WAVELENGTHλ= 12.2 cm for 2450 MHz

Direction of wave

E

E

E

H

H

H

What are microwaves? Frequency and Wavelength

Electromagnetic waves are characterized by three parameters:

frequency (f) = number of cycles/second

wavelength ()

photon energy (E)

Where:- c is the speed of light in vacuum, 3 x 108 m/s- is the dielectric constant of the propagating medium , for gases = 1- h is Planck’s constant, 6.62×10−34 J·s

For electromagnetic waves in free space, where f is in hertz:

Examples:- f = 2.45 GHz (2450 x 106 Hz) = 12.2 cm - f = 915 MHz (915 x 106 Hz) = 32.7 cm

fm

8103)(

fc

Hzf )(


hc

JE )(

What are microwaves? Electromagnetic Spectrum


What are microwaves? ITU allocated bands for ISM applications


Fig. 2. Frequency band regions allocated by ITU

R1- Europe, Africa, Turkey, Russia (Siberia)

& Mongolia, Middle East (without Iran)

R2 – South & North America

R3 – Remaining countries

Radio-frequency and Microwave bands for Industrial, Scientific and Medical (ISM) applications allocated by the International Telecommunications Union (ITU)

Frequency band Central frequency

Wavelength World regions covered

6.765 – 6.795 MHz 6.78 MHz 44.2 m Under consideration

13.553 – 13.567 MHz 13.56 MHz 22.1 m R1, R2, R3

26.957 – 27.283 MHz 27.120 MHz 11.1 m R1, R2, R3

40.66 – 40.70 MHz 40.68 MHz 7.4 m R1, R2, R3

433.05 – 434.79 MHz 433.92 MHz 0.69 m R1

902 – 915 MHz 915 MHz 0.33 m R1, R2, R3

2400 – 2500 MHz 2450 MHz 0.12 m R1, R2, R3

5725 – 5875 MHz 5800 MHz 0.05 m R1, R2, R3

24 – 24.25 GHz 24.125 GHz 1.24 cm R1, R2, R3

61 – 61.5 GHz 61.25 GHz 0.49 cm Under consideration

122 – 123 GHz 122.5 GHz 0.24 cm Under consideration

244 – 246 GHz 245 GHz 0.12 cm Under consideration

Electromagnetic energy interactions with matter


Region of the electromagnetic spectrum

Main interactions with matter

RadioCollective oscillation of charge carriers in bulk material (plasma oscillation). An example would be the oscillation of the electrons in an antenna.

Microwave through far infrared Plasma oscillation, molecular rotation

Near infrared Molecular vibration, plasma oscillation (in metals only)

VisibleMolecular electron excitation (including pigment molecules found in the human retina), plasma oscillations (in metals only)

UltravioletExcitation of molecular and atomic valence electrons, including ejection of the electrons (photoelectric effect)

X-rays Excitation and ejection of core atomic electrons

Gamma raysEnergetic ejection of core electrons in heavy elements, excitation of atomic nuclei, including dissociation of nuclei

High energy gamma raysCreation of particle-antiparticle pairs. At very high energies a single photon can create a shower of high energy particles and antiparticles upon interaction with matter.

Microwave energy versus other electromagnetic energyIonizing or non-ionizing?


Radiation type

Typical frequency

(MHz)

Quantum (photon) energy Chemical bond

type

Chemical bond energy (eV)

eV kcal/mol eV kcal/mol

Gamma ray

X-Ray

UV

Visible

Infrared

Microwaves

Radio-waves

3.0 x 1014

3.0 x 1013

1.0 x 109

6.0 x 108

3.0 x 106

2450

1

1.24 x 106

1.24 x 105

4.1

2.5

0.012

1.6 x 10-5

4 x 10-9

2.86 x 107

2.86 x 106

95

58

0.28

0.037

9 x 10-8

H-OH

H-CH3

H-NHCH3

H3C-CH3

PhCH2-COOH

H-O-H ... O-H

H

5.2

4.5

4.0

3.8

2.4

0.21

120

104

92

88

55

4.8

Microwaves & their interactions with matter


Pr

0

Material (’, ’’)

m

Air

d

Pa/e

Pa

Pi

Pf = forward power Pa = absorbed power

Pr = reflected power λm = wavelength in material

λ0 = wavelength in air ’ = permittivity (wavelength specific) = material capacity to stock energy

’’ = dielectric losses (absorption specific; absorption increases with ’’),

loss of energy by relaxation (important in microwaves) and conduction; in general, 10-2 < ’’

< 102

tg = loss tangent

λm < λ0

Dielectric constants ’ and ’’ are not constants; they depend on: - Wave frequency;- Material temperature;- Material phase, e.g. gas, liquid, solid, polymer etc.

Microwaves & their interactions with matterMain parameters


VtgKfEKVfER

VPa '2''2

2

V''

Pa = absorbed power (watts)K = constant, 0.55 x 10-10 V = sample volume (m3)f = frequency (Hz)E = electric field inside the sample (V/m)’’ = dielectric loss (F/m)

1. Absorption

VKf

PE a

''2

2. Penetration depth, d

d = penetration depth in to material where the power is Pa/e or 36% of the Pa calculated at the point of entrance

Material Penetration depth, d27 MHz 2450 MHz

Air many km many kmWater 10 cm 1.5 cmBalsa wood 2 m 20 cmOak 30 cm 3 cmRubber 15 cm 2 cmAluminium 16 microns 1.7 microns

Microwaves & their Interactions with Matter Heating mechanisms

Conduction mechanisms (electrical conductor)

Heating via charge carriers (electrons, ions etc.) polarisation P (in approx. 10-8s)

Dipolar polarisation or Dielectric heating (polar liquids)

The electric field interacts with dipolar molecules


Microwaves & their Interactions with Matter Classification of materials


INSULATOR Total Transparent ΔT = 0

CONDUCTOR None Reflective

DIELECTRIC Partial to totalAbsorptive ΔT> 0

Examples: quartz, ice, non-polar solvents

Examples: metals

Examples: water, polar solvents, zeolites

Material type Penetration

~ 2cm /2 ~ 6 cm (2450 MHz)

Hot area

Cold areas

Ea/2

Ea

~ 2 m /2 ~ 5.6 m (27 MHz)

Microwaves & their Interactions with Matter The effect of wavelength (frequency) on heating homogeneity


Video\progress wave MagnE face.aviVideo\progress wave MagnE.avi

Microwaves & their Interactions with Matter - Examples


Material Depth of penetration Classification

Glass Quartz 150 m Insulator

Pyrex 2 m Insulator

Plastics PTFE 25 m Insulator

Polyethylene high density 25 m Insulator

Polypropelene 18 m Insulator

Foods Ice 12 m Insulator

Water 30 mm Dielectric

Meat 12 mm Dielectric

Metals Aluminium 2 μm Conductor

The transmitted electromagnetic energy penetrates into the interior of materials and attenuates to an extent depending on the dielectric constant.

The inverse of the attenuation constant is defined as the skin depth/depth of penetration.

Microwaves & their Interactions with Matter Rates of heating for liquids


Solvent Dielectric constant ’

T 0C Bp 0C

Water 78.5 81 100

Methanol 32.6 65 65

Ethanol 24.3 78 78

1-Propanol 20.1 97 97

1-Butanol 17.8 109 117

1-Pentanol 13.9 106 137

1-Hexanol 13.3 92 158

Acetic acid 6.2 110 119

Acetone 20.7 56 56

Hexane 2.0 25 68

Heptane 2.0 26 98

CCl4 2.2 28 77

Temperature of 50 mL of several solvents after heating from room temperature 1 min at 560 W, 2.45 GHz

Polar solvents

Non-polar solvents

Rise of temperature depends on:- Dielectric constant- Specific heat capacity- Emissivity- Strength of applied field

Microwaves & their Interactions with Matter Rates of heating for solids (powder)


Effect of microwave heating on temperature of solids 1 kW, 2.45 GHz Sample 25g (particle size 5-80 μm)

Chemical T, 0C Time, min

Al 577 6

C 1283 16

Co2O3 1290 3

CuCl2 619 13

FeCl3 41 4

NaCl 83 7

Ni 384 1

NiO 1305 6.25

CaO 83 30

CuO 701 0.5

Fe2O3 88 30

Fe3O4 510 2

TiO2 122 30

WO3 530 0.5

B4C (>400μm) 214 2

B4C (5 - 80μm) 665 2

Microwaves & their Interactions with Matter – Thermal effect


The effect of microwave energy transfer in to a material results in its temperature increase

The relation between the absorbed power and temperature increase (without phase change)

where:Pa = absorbed power (W) m/t = sample weight per unit of time (gs-1)T = temperature gradient (K)Cp = specific heat capacity (J g-1 K-1)

! Pf > Pa

Efficiency of power (energy) transfer in to a material:- RF and microwaves 60 – 98 %- IR 20 – 60 %- Hot air 10 – 40 %

TCt

mP pa

Microwave heating vs. Conventional heating


Microwave heating / Dielectric heating

Conventional heating / Heat conduction

Heating of polar molecules with an electric dipole moment; energy transferred directly from the electric field to molecules if walls of containment vessel are ‘microwave transparent’

Transfer of thermal energy from outside - energy transferred indirectly from containment vessel to reaction mixture. The time of heating depends on the thermal conductivity of the material to be heated and the distance from the heating source to the material.

Superheating of absorptive molecules due to rapid & selective energy transfer from the electric field temperature gradients in solution

Temperature of containment vessel walls is higher than the reaction temperature

p = power density, = field frequency’’

r = relative permittivity; 0 = permittivity of free spaceE = electric field strength

Fourier’s law2

0'' Ep r

Microwave heating vs. Conventional heatingMagic effect?


RT

Ea

Aek

Arrhenius equation:

Temperature 0 C

Reaction rate increase

100 4.7 x 10-30 1

110 2.73 x 10-29 5.8

120 1.46 x 10-28 31

130 7.16 x 10-28 152

150 7.16 x 10-26 2914

RT

Ea

e

Ea = 50 kcal/mol

Microwave Equipment for Heating ApplicationsBasic equipment


Microwave generator

Antenna for direct irradiation

Multimode cavity

Monomode cavity

MICROWAVE

APPLICATOR

POWER SUPPLY

AND PROTECTION

SYSTEMS

MAGNETRON


Applicators are devices designed to ensure the transfer of electromagnetic energy from the transmission line to the material to be treated.

Waveguide launcherCirculator

Dummy load

MagnetronMode stirring

Sample

Waveguide

Antenna

Microwave Equipment for Heating Applications Multimodal Applicators

Microwave Equipment for Heating Applications Single Mode Resonant Cavities


Metallic enclosure into which a launched microwave signal of the correct electromagnetic field polarization will suffer multiple reflections between preferred directions. These cavities represent volumes of large stored energy which is transformed into heat via displacement and conduction currents flowing through the dielectric material as soon as it is placed within the heating zone.

Operation must be within narrow frequency bands in order to maintain high coupling efficiencies.

In general, a single mode resonant heater will establish much higher electric field strengths than a traveling wave or multimode applicator; these structures are in general more compact with extremely high power densities (107 kW/m3).

Microwave Equipment for Heating Applications Single Mode Resonant Cavities


a

b

E

Electric field distribution & intensity in TE10 mode waveguide, 2.45 GHz

Standard

waveguide

a mm

bmm

WR340 86.36 43.18

WR430 109.2 54.60

Microwave Equipment for Heating Applications Single Mode Resonant Cavities – Standing wave formation


The superposition of the incident and reflected waves gives rise to a standing wave pattern which for some simple structures is very well defined in space

Video\standing wave MagnE3.aviVideo\standing wave MagnE.aviVideo\standing wave MagnE2.avi

E1

E2

λ0/2

In air = 61 mm

2

1

E

EWVSR

References


1. Rochas, J.F., International Symposium on Microwave Science & its Applications to Related Fields, 28-30 July 2004, Takamatsu, Japan

2. Metaxas, A.C., Meredith, R.J., industrial Microwave Heating, IEE Power Engineering Series 4, 1993.

3. Kingston, H.M., Haswell, S.J., Microwave-Enhanced Chemistry, American Chemucal Society, Washington, DC.,1997.

More information:- CEM Corporation cem.com- General Microwave Corp. generalmicrowave.com- Holaday Industries Inc. holadayinc.com

SAIREM’s Microwave assisted SAIREM’s Microwave assisted Chemistry/ExtractionChemistry/Extraction

Process-specific combined high-frequency generators and reactors

Enhanced safety Process compatibility Minimum footprint Reduced cost of ownership

Innovative method for energy transmission directly into the reaction media via an Internal Transmission Line INTLI & U-waveguide (Sairem patents WO 2009/122101 and WO 2009/122102) combined with the latest generation of high-frequency generators and intelligent controllers.



HIGH FREQUENCY GENERATOR

REACTOR(APPLICATOR)

Energy transmission line


HIGH FREQUENCY GENERATORS

MICROWAVE GENERATORS915 MHz & 2450 MHz

RADIO-FREQUENCY GENERATORS13.56 MHz & 27.12 MHz

GENERATORS > 2450 MHz

Radio-frequency generators Radio-frequency generators 13.56 MHz & 27.12 MHz up to 90 kW13.56 MHz & 27.12 MHz up to 90 kW


13.56 MHz, 12 kW

Microwave generatorsMicrowave generators 915 MHz, 600 W – 100 kW 915 MHz, 600 W – 100 kW


600 W 5 kW 30 kW

Microwave generators 2450 MHzMicrowave generators 2450 MHz


Solid state 25 W – 120 W 300 W – 15 kW

2oo W generator 2 kW 6 kW

2oo W integral module 15 kW

Generators frequency > 2450 MHzGenerators frequency > 2450 MHz


2 kW @14 GHz & 18 GHz

Power supply 10 kV x 1A for klystron

10 kW @ 28 GHz

Power supply 30 kV x 1.5 A for gyrotron


ENERGY TRANSMISSION LINE

COAXIAL CABLE

WAVEGUIDE


REACTORS (APPLICATORS)

BATCH

CONTINUOUS FLOW


Industrial microwave chemistryTreatment of residual acids from nitrocellulose fabrication

Residual acid treatmentNitroglycerin destructionMicrowave: 8 kW (2 kW + 6 kW) 2.45 GHzCapacity: 300 kg/hProcess temperature: 150 °C

Preheated residual acid

PROCESS DIAGRAM

Residual acid mixture

Regenerated acids

Heat exchanger

MWHead


Industrial microwave chemistry Laurydone synthesis

6 kW 2.45 GHz Laurydone synthesis

MW reactor

Pyroglutamic acid + Lauryl alcohol NO NEED FOR CATALYST (p-toluene sulphonic acid) and solvent (toluene) Microwave powerMicrowave power : 6 kW 2.45 GHzBatch production : 150 kg in 4 hoursReaction time reduced 5 times


NEW!!!!

LABOTRON X & LABOTRON S

Minilabotron 2000

MICROWAVE ASSISTED MICROWAVE ASSISTED CHEMISTRY/EXTRACTIONCHEMISTRY/EXTRACTION

LABOTRONExtraction/Synthesis = Integrated microwave generator and reactor


+=

LABOTRON X and S

MW Generator ≤ 6 kW

2.45 GHz

INTLI + U-waveguide+

Batch ~ 0.5-17 L

REACTOR

Continuous flow CF

LABOTRON X and S, Microwave-assisted LABOTRON X and S, Microwave-assisted extraction and synthesis extraction and synthesis


LABOTRON 6 kW with batch reactor LABOTRON 2 kW with CF reactor

LABOTRON X and SLABOTRON X and S - Batch reactors- Batch reactors


Batch reactor 1.7 L Batch reactor 17 L

LABOTRONLABOTRON X and S - Continuous flow X and S - Continuous flow reactorsreactors


SPIN S SPIN M

LABOTRON X and SLABOTRON X and S - Batch Reactor- Batch Reactor


Minilabotron 2000 with batch reactorMinilabotron 2000 with batch reactor


Minilabotron 2000 with CF reactorsMinilabotron 2000 with CF reactors


Minilabotron 2000 with horizontal SPINreactor

Minilabotron 2000 with horizontal column reactor


PILOT-scale up to 30 kW, 915 PILOT-scale up to 30 kW, 915 MHzMHz


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Batch reactor 100 L Continuous flow reactor

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