Hydrothermal Gasification of Woody Biomass

Hydrothermal Gasification of Woody Biomass

LEM – Laboratory for Energy and Materials Cycles

Catalytic Process Engineering– M.H. Waldner, F. Vogel

Contact: Frédéric Vogel, Paul Scherrer Institute, OVGA/104, 5232 Villigen-PSI, Switzerland - phone: +41-(0)56-310-2135 fax: +41-(0)56-310-2199 / email: frederic.vogel@psi.ch ID: 14 mm

Š Introduction

Wet biomass (liquid manure, wood) contains large energy potentials. Synthetic natural gas (SNG) is produced today by a conventional route (gasification of biomass to syngas, gas cleaning and methanation to SNG). The hydrothermal route is a promising new technology, as the thermal efficiency is higher and nutrient saltscan be extracted from the biomass for further use. In addition, the expensive process of drying has become obsolete.

Š Results

240 mm

Š Experimental

Equipment:

ƒBatch reactor(316SS) for high feed conc.

(w_wood< 30 wt%); with cooler or as bomb

ƒHeating in a fluidizedsandbath

ƒQuenchingby immersing into waterbath

ƒOnline dataanalysis with LabView software Analytics:

ƒGas Chromatography & HPLC

ƒDohrmann DC-190 TOC Analyzer

ƒKarl Fischer Titration

ƒXPS / TPO

Reactant mixture and liquid product:

Complete Conversion

Products:

pure water and gases

Gas composition achieved (selected experiments):

0 10 20 30 40 90 100

0 5 10 15 20 25 30 35 40 45 50 55

CH4 / vol%

time (T > 374 °C) / min.

HB400R05 HB400R04 HB400R06 HB400R07 HB400NC1

Promoted with Ni-catalyst Thermodynamic equilibrium (Peng Robinson EOS)

No catalyst added

T = 400°C, p ≈ 30 MPa

Very close to thermodynamic equilibrium

Residual carbon in liquid product (water):

H OH

O Wood (Fir)

Cellulose Hemicellulose (Xylan) Lignin Inorganics

hydrolysis Glucose Xylose Glucuronic acid

5-HMF - H2O

Coniferylalcohol

catalytic influence

Polyphenols

& Phenols

Tars

Alcohols Carboxylic acids Aldehydes Ketones

CO₂ CO H2 CH4

CH4 Methanation

CO₂ + H₂ CO + H₂O ^WGS CO₂ + H₂

+ H2O

hydrolysis

cat.?

cat.

cat.?

cat.

CO₂ + 4 H₂ CH₄ + 2 H₂O Decarboxylation

Methanation

CH₃COOH CH₄ + CO₂ Reformation

Decarboxylation Decarbonylation

Decarboxylation Cresols

Phenols Guaiacols Indenes

Benzols Toluol Xylols

cat. cat.

- H2O

coke - H2

PAH ^{- H2} + H2O

+ H2O + H₂O + H2O

cat.

+ H2O + H2O

+ H2O

Proposed reaction network:

Economics:

For a 20 MWthplant (70% thermal process efficiency), SNG can be produced at a cost of:

ƒ10 USD/GJ for wood (price for wood 3.5 USD/GJ)

ƒ6 USD/GJ for zero-cost liquid manure

0.1 1 10 100 1000

HB400R08 HB400R07 HB400R06 HB400R04 HB400R05 HB400NC1 HB300R01

TOC / g L^-1

32.0%

24.9%

8.5%

1.4%

1.9%

1.3%

0.8%

Residual TOC in liquid Experimental TOC Input

Experimental TOC Input (wood) Residual TOC in liquid after experiment

Liquefaction, Products w/o catalyst and

quench experiment

„Successful“

gasifications

Vogel F., Hildebrand F. (2002) Catalytic Hydrothermal Gasification of Woody Biomass at High Feed Concentrations. Chem. Eng. Trans., 2: 771-777.