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Waste Derived Carbons for Syngas Tar Removal Amal S. ARahbi*, Paul T. Williams University of Leeds

Waste Derived Carbons for Syngas Tar Removal - UESTuest.ntua.gr/athens2017/proceedings/presentations/Al-Rahbi.pdf · Waste Derived Carbons for Syngas Tar Removal ... H2 CO CO2 CH4

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Waste Derived Carbons for Syngas Tar Removal

Amal S. A‐Rahbi*, Paul T. WilliamsUniversity of Leeds

Conclusions

Results-Effect of carbon type-Effect of ash minerals-Tar composition

Experimental-Char production &characterization-Tar Collection & analysis-Experimental setup

Contents

Introduction

IntroductionExperimental setup

ResultsConclusion

• Hydrogen is considered as an important fuel of the future. There has been a growing interest to find a sustainable source for hydrogen production.

• Gasification is one of the effective thermochemical conversion processes of biomass energy for producing a hydrogen rich gas, however tar formation is a major problem.

• Carbonaceous char can act as a catalyst to degrade the tar components to useable gases.

Research goal:

• To investigate the use of waste-derived char as a catalyst for hydrogen production and tar cracking during the pyrolysis/reforming of biomass.

Introduction

Experimental setup

ResultsConclusion

EFFECT OF BEDTYPE

Tar cracking in theAbsence of steam

NO charTyre charRDF char

Date stones char

EFFECT OF CHAR ASH/with steam

Hydrogen-rich syngasproduction &tar reforming

Tyre char

Acid treated tyre char

Introduction

Experimental setup

ResultsConclusion

Char production

Water cooled condenser

To exhaust

N2

Furnace

Samplecrucible

waste

ThermocoupleT

Dry Ice cooled condensers

Water trap

Gas sampling

point

Conditions:√ Char: Waste Tyres, RDF, Date stones.√ Pyrolysis temperature: 800°C.√ Carrier gas: N2(Also de-mineralised pyrolysis tyre char was investigated)

Introduction

Experimental setup

ResultsConclusion

T

Char

Thermocouple

BiomassN2

Mass flow controller

Exhaust

Condenser system

Tar & gases

Gas sample bag

Experimental setup

Liquid product

Tar/oil+H2O

Karl-Fischer Titration

Water removal-Na2SO4 bed

Evaporation of DCM

GC-MS analysis

Water content

Tar

Pyrolysis temperature=500°C Biomass : char ratio=1:1

Introduction

Experimental setupResultsConclusion

Without char Tyre char RDF char Date stones char

Temperature (°C) 800 800 800 800Residual Biomass Char (wt.%)

23 23.5 23.5 24

Liquid (wt.%) 28.5 8.5 17 24.5Tar (wt.%) 15.3 4.6 7.6 13.9Water (wt.%) 13.3 3.9 9.4 10.6

Gas yield (wt.%) 46.6 57.5 59.5 50.6Gas composition (vol.%)CO 42.3 34 29.9 40.1H2 19.6 29 34 25CO2 16.2 20.3 21.7 16.2CH4 15.1 12.1 10.5 12.8C2─C4 6.7 4.7 3.9 5.9

Mass balance (%) 98 89.5 99.9 99.1

Influence of waste derived pyrolysis char on the product yield from the pyrolysis-gasification of biomass

Introduction

Experimental setupResultsConclusion

100 120 140 160 180 200 220 240

0

5

10

15

20

25

30

Wei

ght p

erce

ntag

e (%

)Molecular weight (g mol-1)

Date seeds char RDF char Tyre char NO char

Without char Tyre char RDF char Date seeds char0

10

20

30

40

50

60

70

Rel

ativ

e co

ncen

trat

ion

(%)

Phenols PAHs

Tar composition

• The main compounds detected were phenolic compounds and polycyclic aromatic hydrocarbons (PAH).• The fraction of polyromantic hydrocarbons decreased significantly with the use of tyre char compared to

the experiment without char.

Introduction

Experimental setupResultsConclusion

Effect of carbon type over tar composition at a cracking temperature of 800 °C

Introduction

Experimental setupResultsConclusion

Tyre char Acid treated tyre charTemperature (°C) 700 800 900 700 800 900

Mass balance based on the biomass sample + water (wt.%)

Gas 12.1 16.6 33.0 11.6 15.8 26.1

Liquid 82.8 76.87 61.4 84.5 79.9 69.5

Biomass char 5.6 5.8 5.5 5.5 5.9 5.5

Mass Balance 100.5 99.2 99.8 101.6 101.0 97.5

Tyre char recovered (%) 100.0 91.0 82.5 101.0 98.0 85.5

Mass balance based on the biomass sample (wt.%)

Gas 50.0 67.1 131.6 48.9 63.1 106.8

Biomass char 23.0 23.3 22.0 22.5 23.5 22.5

Gas characterization

HHV (MJ Kg-1) 48.3 52.5 66.1 27.9 44.3 63.6

H2 yield (mmol g-1) 8.4 12.5 39.2 2.7 8.6 30.5

H2/CO (mol mol-1) 1.31 1.37 2.11 0.37 0.75 1.41

The influence of simultaneous gasification of pyrolysis gases and char

Introduction

Experimental setupResultsConclusion

0

10

20

30

40

50

0

20

40

60

80

100

700 800 900 700 800 900

Hyd

roge

n yi

eld

(mm

ol g

-1)

Gas

com

posi

tion

(vol

.%)

Temperature (C°)

H2 CO CO2 CH4 CnHm H2 Yield (mmol/g)

Acid treated tyre charOriginal tyre char

Gas compositions and hydrogen yield with original and acid treated tyre chars

Introduction

Experimental setupResultsConclusion

H2, coke, CnHm,…

coke

Functional groups(FG)CO,CO2

Cracking of FG

Formation of FG

Active sites for tar conversion

Metal speciesFunctional groups

0

10

20

30

40

50

60

70

80

90

Original Tyre char Acid treated Tyre char

Peak

are

a (%

)

Class 2 Class 3 Class 4 Class 5

Concentration of classified tar compounds

Tar Analysis

• Carbonaceous chars simulates the cracking of tar in gasification syngas.

• Hydrogen production increased significantly with the use of tyre char in the 2nd stage to be about 39.20 mmol g-1 biomass due to the simultaneous reactions of tar reforming and char gasification.

• The difference in hydrogen production between the original and the acid treated tyre chars suggests that metals present in tyre char have a significant catalytic effect in enhancing the water gas shift, tar reforming and char steam reactions.

• Waste-derived chars would represent a low cost source of catalytic char material for hydrogen production during biomass gasification.

Introduction

Experimental setupResultsConclusion

Questions