High pressure drop-tube pyrolysis of brown coal and its kinetics

Kevin Günther, Steffen Krzack, Jörg Kleeberg, Bernd MeyerInstitute of Energy Process Engineering and Chemical Engineering (IEC) / Virtuhcon – Virtual High Temperature conversionTU Bergakademie Freiberg

Berlin, Germany5th June 2018

Center for Innovation Competence:Virtual High Temperature Conversion

High pressure drop-tube pyrolysis

Outline

2

I. Motivation

II. Feedstock characterization

III. Drop-tube reactor and process balancing

IV. Product yields

V. Reaction kinetics

VI. Summary and outlook

High pressure drop-tube pyrolysis

Motivation

3

Waste processing for chemical

recycling

Availability of domestic

lignite

“Green” H2from renewable

electricity

Gasification of carbonaceous waste & coal

Chemical products from domestic

carbon resources

ClosedCarbon Cycle!

Minimized CO2 emissions

Syngas processing& chemicals synthesis

Gasification

Pyrolysis

VolatilesChar

Feed-stock

T p ΔTΔ t

Gasifyingagent

Ther

moc

hem

ical

conv

ersi

onpr

oces

ses

High pressure drop-tube pyrolysis – Feedstock

Feedstock characterization

4

Drying (105 °C)

Sieving

Pyrolysis in PYMEQ

CharCondensate (+THF) Gas

Tar/Oil

Destillation

THF + Water

Analysis

Analysis

MS, GC

Analysis

63…200 µm

Process balancing, reaction kinetics, residence time, …

Process modelling, process simulation and process optimization

Lignite (Central German coal-mining district)Feedstock

x10 72 µm

x50 131 µm

x90 190 µm

dV 131 µm

φ 0.89

Particle size distribution of 63…200 µm

High pressure drop-tube pyrolysis – Drop-tube reactor

High pressure drop-tube reactor PYMEQ

5

PYrolysis Measurement EQuipment

Gas supply:- Argon- Hydrogen- Carbon Dioxide- Methane- Steam

Argon

Argon

Pressure control system

Process gasanalysis

(permanent gases)

Thermal post combustion

Process gas

Stack

Gas sampling 1

Gas sampling 2

Char collector(electr. heated)

Char (4 samples)

Particle filter(electr. heated)

Condensationsystem

Purge gas, volatiles andentrained char particles

Char (1 sample)

Tar/Oil andReaction water

Process gas

Aerosol filter

Coal storage and feedingCoal

Reactor(electrical heating)

• T ≤ 800 °C• p ≤ 100 bar (g)• Ar, H2, CO2, CH4,

steam and mixtures

Process conditions

• Heated length: 2.5 m• Reactor ID: 20 mm• 2-stage condensing

system (-20 °C)• Online MS• 1 optical port

Feeding system• Max. 1.0 l, ≤ 10 g/min• 40…1,000 µm• Moisture ≤ 10 wt.%

Equipment

600 °C 700 °C 800 °C5 bar x

10 bar x

20 bar x x x

40 bar x x x

80 bar x x x

100 bar x

High pressure drop-tube pyrolysis – Characterization methods

Process balancing at high pressure drop-tube reactor PYMEQ

6

C 62.6 wt.-%H 4.7 wt.-%N 0.6 wt.-%SC 1.2 wt.-%O 17.2 wt.-%

Coal(4.8-6.0 g/min)

Char

Argonmax. 500 l/h

(STP)

5 heatedzones

(2.5 m)

Argonmax. 100 l/h

(STP)

Pyrolysis gas

Tar/Oil

Reactionwater

C 72.9 wt.-%H 1.8 wt.-%N 0.6 wt.-%SC 0.7 wt.-%O 0.7 wt.-%

LHV 27.0 MJ/kg

H2 30.1 vol.-%CO 18.2 vol.-%CO2 21.0 vol.-%CH4 28.0 vol.-%H2S 2.1 vol.-%C2+ 0.6 vol.-%LHV 16.5 MJ/m³

Experimental matrix

H 11.2 wt.-%O 88.8 wt.-%

*as received

Water* 9.7Ash (dry, 815 °C) 13.7Volatiles (dry) 50.9Cfix (dry) 35.4

Proximate analysis, wt.-%Ultimate analysis Energy content, kJ/kgHHV (dry) 25,350LHV (dry) 24,329

C 74.3 wt.-%H 8.1 wt.-%N 0.3 wt.-%S 1.1 wt.-%O 16.2 wt.-%

LHV 33.8 MJ/kg

(at dry state)

(at dry state)

(at dry state)

High pressure drop-tube pyrolysis – Results of pyrolysis investigations

Product yields (heated reactor length = 2.5 m)

7

54,9 58,0 51,2 51,0 55,5 52,9

43,4 36,1 43,5 44,7 39,8 46,3

0

20

40

60

80

100

5 10 20 40 80 100

Prod

uct y

ield

s in

wt.-

%

Pressure in barg

60,3 55,9 51,2

29,0 34,8 43,5

10,7 9,3 5,3

0

20

40

60

80

100

600 700 800

Prod

uct y

ield

s in

wt.-

%

Temperature in °C

5.3 0.75.81.8 4.74.3(1.0)(2.3)(3.8)

Yield Tar/Oil

• T ↑ char ↓gas ↑condensate ↓

• Significant degradation of tar/oil fraction athigher temperatures

• No consistent influence of process pressure• Maximum of char yield and condensate yield

at 10 barg

20 barg 800 °CCondensatePyrolysis gasChar

60.3 55.9 51.2 54.9 58.0 51.2 51.0 55.5 52.9

43.4 36.1 43.5 44.7 39.8 46.329.0 34.8 43.5

10.7 9.3 5.3

High pressure drop-tube pyrolysis – Reaction kinetics (model)

Model for determination of kinetic parameters

8

Representation of pyrolysis process as decomposition reaction

→

· with ,

Xi = concentration of reactive groups in the coal macro molecule

Condensable components(reaction water, tar/oil fraction)

Pyrolysis gas(CH4, CO, CO2, H2, C2H6, C2H4, C2H2, C3H8, C3H6, C3H4, …)

, with 0 0

Mathematical expression:

High pressure drop-tube pyrolysis – Reaction kinetics (model)

Model for determination of kinetic parameters

9

for → ·1

for → · · ·1

Description of pyrolysis process by isothermal approach of independent parallel reactions

Arrhenius plot

for → · 1 ·

f → 1·

Recalculation/Modelling of gas formation:

Substitution of k(T) by Arrhenius equation

High pressure drop-tube pyrolysis – Reaction kinetics (kinetic parameters)

Kinetic parameters of main gas components

10

n = 1 n = 220 barg 40 barg 80 barg 20 barg 40 barg 80 barg

EA in kJ/mol k0 in s-1 EA in

kJ/mol k0 in s-1 EA in kJ/mol k0 in s-1 EA in

kJ/mol k0 in s-1 EA in kJ/mol k0 in s-1 EA in

kJ/mol k0 in s-1

H2 126 354,978 103 3,690 140 1.4E+06 238 1.1E+10 118 80 253 5.5E+10

CH4 73 599 89 1,321 61 69 123 6,056 117 177 84 14

CO 100 7,413 137 2.4E+05 158 1.1E+07 133 7,751 164 32,478 273 6.6E+11

CO2 27 5 60 57 5 0.1 73 137 90 13 7 0

Total Gas 65 254 80 392 52 34 120 1,476 104 8 83 6

General tendency to higher values for higher overall pressures (except CH4) Gas formation is inhibited by high pressure

EA: CO2 < CH4 < CO < H2 (valid for n = 1 and n = 2)

High pressure drop-tube pyrolysis – Reaction kinetics (modelling of gas formation)

Formation of hydrogen and methane

11

20 barg, 800 °C

Hydrogen formation Product of at least one independent reaction curve fitting n = 1Methane formation Product of at least two independent reactions curve fitting n = 2

0

20

40

60

80

100

120

0 200 400 600 800 1000

Gas

yie

ld in

ml/g

coal

Temperature in °C

H2 (n=1)H2 (n=2)H2CH4 (n=1)CH4 (n=2)CH4

20 barg, P = 14.4 s

0

20

40

60

80

100

120

0 5 10 15 20

Gas

yie

ld in

ml/g

coal

Particle residence time in s

H2 (n=1)H2 (n=2)H2CH4 (n=1)CH4 (n=2)CH4

High pressure drop-tube pyrolysis – Reaction kinetics (modelling of gas formation)

Formation of carbon monoxide and carbon dioxide

12

0

20

40

60

80

100

0 5 10 15 20

Gas

yie

ld in

ml/g

coal

Particle residence time in s

CO (n=1)CO (n=2)COCO2 (n=1)CO2 (n=2)CO2

Carbon monoxide formation Product of at least two independent reactions curve fitting n = 2Carbon dioxide formation Product of at least two independent reactions curve fitting n = 2

20 barg, 800 °C

0

20

40

60

80

100

0 200 400 600 800 1000

Gas

yie

ld in

ml/g

coal

Temperature in °C

CO (n=1)CO (n=2)COCO2 (n=1)CO2 (n=2)CO2

20 barg, P = 14.4 s

High pressure drop-tube pyrolysis

Summary and outlook

13

FeedstockPressure 1 2 3 4 5p1 (5 bar) x x x x xp2 (10 bar) xp3 (20 bar) x x x x xp4 (40 bar) xp5 (80 bar) x x x x xp6 (100 bar) x

Exemplaryexperimental

matrixPYMEQ

Strong influence of temperature but less influence of total pressure on product yields Determined kinetic parameters comparable to literature Formation of main pyrolysis gas components can be described (in terms of residence time) by

approach of independent parallel reactions

Future Plans:• Further appropriate pyrolysis models for kinetics• Additional feedstocks (waste materials), also as blends with lignite• Determination of char reactivity by TG-measurements using modified magnetic

suspension balance with forced flow through sample containers

Balance

MagneticSuspensionCouplingMeasuringgas

Cooling

Furnace

Cooling

HP reactor

Reactiongas

SampleSampletemperature

Co-currentsample container

Thanks for your attention!

14

We gratefully acknowledge the German Federal Ministry of Education and Research (BMBF)that funded the research within the framework of the Centre for Innovation Competence Virtuhcon.