Technologies to convert wood to

energy. Thermo-chemical conversion.

◊First thematic seminar and study visit in Tartu region.

INTEREG IVC Project BIO-EN –AREA.

Ülo KaskTallinn University of Technology, Thermal Engineering Department15.06.2011.

Preface

During last year strong interest for biomass

gasification topic has been emerged in our

country from one side and much efforts for

development of gasifiers has been done in the

world from other side.

Following I try shortly to introduce this field in

my presentation.

Topics

Biomass energy chain

Opportunities to convert wood and use it in

energy

Thermo-chemical conversion of biomass

(wood)

Wood gas and wood gasifiers

CHP running on wood gas

Automobiles running on wood gas

Biomass energy chain

Carbonization Grinding Aerobic degradation

Gasification Pressing Anaerobic digestion

Pyrolysis Esterification Fermentation (C2H5OH)

Cultivating, harvesting/gathering

Processing, transport, storage

Conversion

Thermo-chemical, Physical-chemical, Bio-chemical

Solid, liquid and gaseous products (fuels)

Combustion Thermo-mechanical conversion

Heat, electricity, motor-fuels

Opportunities to convert wood and

use it in energy

Physical-mechanical conversion of wood (pre-treatment) and combustion in fire places and energetical furnaces.

Bio-chemical conversion of wood (wood waste) (biogas, bio-ethanol, bio-methanol).

Thermo-chemical conversion of wood (decomposition) and combustion of products (wood gas, charcoal, wood oil) in large combustion facilities or in in internal combustion engines.

Physical-mechanical conversion of wood (pre-treatment) and

combustion in fire places and energetical furnaces

Wood chips (felling residues

chips), wood briquettes and

pellets, wood logs, saw dust etc

Termo-chemical conversion of biomass

(wood)

By thermo-chemical conversion processes (such

gasification, pyrolysis and carbonization), solid bio-

fuels are transformed into solid, liquid and/or

gaseous secondary energy carriers primarily using

heat.

2C + O2 2CO

CO + H2O CO2 + H2

Selection of decomposition products of

wood is presented on figure at right

During conversion of biomass at high temperature three main products are forming: gas, bio-oil and char.

Gasification

Within a thermo-chemical gasification solid biomass (bio-fuels) are preferably converted into gaseous energy carriers.

The process my be viewed as “combustion-like” conversion, but of less oxygen available than needed for burning,excess air is 0,2-0,4 (equivalence ratio), it means that up to 40% of oxygen needed for complete burning is given). This is the region of maximum energy transfer to the gas.

. The goal in gasification is to break down this wide variety of

forms into the simple fuel gasses of H2 and CO – hydrogen and carbon monoxide.

The produced gas may alternatively also be further converted into liquid or gaseous secondary energy carriers (e.g. methanol, Fisher-Tropsh-Diesel fuel, bio-SNG) suitable for use in transport sector.

Processes in gasification

Gasification –

like choked

combustion.

Gasification is

the “operating

system of fire”

Gasification is made up for 4 discrete thermal processes: Drying, Pyrolysis,

Combustion and Reduction. All 4 of these processes are naturally present in the flame

you see burning off a match. Gasification is merely the technology to pull

apart and isolate these separate processes, so that we might interrupt the

“fire” and pipe the resulting gasses elsewhere.

Chemical reactions of combustion

Through this process, CO2 is reduced to CO. And H2O is reduced to H2and CO.

Combustion products become fuel gasses again.

And those fuel gasses can then be piped off to do desired work elsewhere.

Gas quality and application fields

The gas produced by gasification of biomass

called a “medium-quality gas”, calorific (heating)

value is within 10-18 MJ/m3.

This gas may be used directly in Otto or Diesel

engines,

it may be used to drive heat pump compressor

or alternatively, it may be upgraded to pipe-line

quality gas (about 30 MJ/m3)

or converted to methanol.

Pyrolysis

For pyrolysis solid biomasses are treated exclusively by the use of thermal energy with the goal to maximize the share of liquid products.

Pyrolysis is dry distillation or retorting or cracking.

As the equivalence ratio (excess air) below 0,1 the gasification process is called pyrolysis. Only a modest fraction of the biomass energy is found in the gaseous product – the rest being in char and oil residues.

Pyrolysis 2

Biomass begins to “fast decompose” with once its temperature rises above around 240 °C. Typically it takes place at temperatures over 430 °C (800 °F). Word comes from Greece words pyr “fire" and lysis “exclusion".

Pyrolysis process of wood begin at temperatures 200–300 °C (390–570 °F). The biomass breaks down into a combination of solids, liquids and gasses. The solids that remain commonly is called “charcoal”. The gasses and liquids that are released collectively called “tars”.

Thus in review, pyrolysis is the application of heat to biomass in the absence of air/oxygen. The volatiles in the biomass are “evaporated” off as tars, and the fixed carbon-to-carbon chains are what remains – otherwise known as charcoal.

Pyrolysis 3

Highest efficiency of process is achieved by using fast

(flash) pyrolysis there raw material is heated quickly

for less than 2 seconds between ranges 350 up to 500

°C (660 and 930 °F).

Triangle diagram

Obtained

gaseous,

liquid and

solid stage

relations

depending

on

conditions of

pyrolysis.

Carbonization

Carbonization refers to the thermo-chemical conversion

of solid biomass aiming at a maximum output of solid

products (charcoal, bio-char).

Carbonization is the term used when complex

carbonaceous substances such as wood or agricultural

residues are broken down by heating into elemental

carbon and chemical compounds which may also

contain some carbon in their chemical structure.

The stages in charcoal formation

The three main stages requiring heat inputs in

charcoal making are:

- The drying of the wood,

- Raising the temperature of the oven dry wood

to 270°C to start spontaneous pyrolysis which

itself liberates heat,

- Final heating to around 500-550°C to drive off

tar and increase the fixed carbon to an

acceptable figure for good commercial charcoal.

Torrefaction or roasting

Torrefaction of biomass can be described as a mild form of pyrolysis at temperatures typically ranging between 200-320 °C.

During torrefaction the biomass properties are changed to obtain a much better fuel quality for combustion and gasification applications. Torrefaction combined with densification leads to a very energy dense fuel carrier of 20-25 GJ/ton .

Added value of torrefied biomass :

Higher energy density , More homogeneous composition, Hydrophobic behavior , Elimination of biological activity, Improved grindability

Energy density of 18 - 20 GJ/m3 compared to wood 10 - 11 GJ/m3 driving a 40 - 50% reduction in transportation costs.

Characteristics of solid fuels for comparison

Products of thermo-chemical conversion

Gas (wood gas)

Tars, oils, (bio-oil)

Coke (at high temperature, above 1000 °C )

Charcoal (barbeque coal, active coal)

Bio-char (not finalized pyrolysis product, at 200-300 °C)

Carbon fiber – diameter 0,005–0,010 mm and contain only

carbon atoms.

Liquid and gaseous bio fuels (methanol, Fisher-Tropsh-Diesel

fuel, bio-SNG).

Wood gas and wood gasifiers

Wood gas - produced by heating of wooden

material at temperature over 700°C and absence of

air or by dry distillation (pyrolysis) method.

Combustible part of wood gas consist of mainly

carbon monoxide (CO), hydrogen (H) and methane

(CH4) .

LHV is about 1,25 MWh/1000 m³. From 100 kg wood

can get 34...40 m³ wood gas.

Average composition of wood gas

Lämmastik - Nitrogen, N2 - 50.9% Vingugaas - Carbon monoxide, CO - 27.0% Vesinik – Hydrogen, H2: - 14.0% Süsihappegaas - Carbon dioxide, CO2 - 4.5% Metaan – Methane, CH4 - 3.0% Hapnik – Oxygen, O2 - 0.6%.

Source: Taylor, Charles Fayette (1985). Internal-Combustion Engine in Theory and Practice - Vol.1. Cambridge: The MIT Press. pp. 46–47. ISBN 0-262-70027-1.

Devices produced wood gas

The first device for producing of wood gas was made by Gustav Bischof on year 1839. The first car driving on wood gas was built by Thomas Hugh Parker on 1901.

1000 kg wood can replace 200...350 petrol(benzine) on normal driving conditions.

Imbert gas generator

Stratified down-draft gasifier

Self-made wood gas

generator and barbeque

with gas generator by

Estonian engineer

Pyrolysis reactor with rotating cone for treatment of wood waste,

250 kg/h. 50 t/d bio-oil. (75% oil, 15% char, 10% losses)

Biomass-to-Liquids (BTL) - Concept

Fast Pyrolysis

Slurry – lobri, pulp

Slurry with pyrolysis coke

Joint grinding of pyrolysis oil and cokegives pumpable/storable slurry.

Energy concentration from biomass toslurry by factor 13.

Ca. 80% of the energy content of thebiomass is contained in the slurry.

Crumble – lagunema, murenema

CHP running on wood gas

The wood gasification - a process known for centuries - has practically the only economically attractive option for the simultaneous production of electricity and heat from wood chips in small decentralized system.

The Spanner Wood-Power-Plant

consists of a gasifier JOOS ™ and a

CHP of the company KW

Energietechnik.

(www.kwenergie.de).

Spanner Re2 GmbH Wood-Power-Plant.

The special feature of the Joos-carburetor™ is a small, controlled fire bed. This allows us to produce systems in a power range from 30 - 50 kWel and 70 - 110 kWth .

The system operates using

commercial wood chips

with a maximum of 30%

fine particle and moisture

~15%.

Ratings of the wood-power-plant

Power range

Heat output

Carburetor

assemblyCHP unit Total

30 kW electrical

66 kW thermalca. 10 kW ca. 56 kW ca. 66 kW

40 kW electrical

88 kW thermalca. 12 kW ca. 76 kW ca. 88 kW

45 kW electrical

100 kW thermalca. 15 kW ca. 85 kW ca. 100 kW

Wood chips consumption: per 1 kW electrical about about

1 kg per hour.

Dimensions of the wood-power-plant

Dimensions Length Width Height

Wood-Gasifier

+ Control

cabinet

5000 mm +

350 mm

1350 mm +

700 mm2300 mm

CHP+ Control

cabinet 2250 mm 990 mm 1470 mm

.

Principle of this technology (Bazi) is the fluidization by

loop flow between the fluidized bed and pulverized

Scheme of present-day wood gas generator

Small wood gas generators (CHP)

Small wood

gas generator

fuelled by

pellets

Use wood waste and sawdust-

able to work off power grids

CHP, capacity 150KWhel and 300KWhth

1 Kg Wood = 1 kWh Electricity + 2 kWh Thermal

Urbas Combined Heat & Power (CHP)

Wood gas cars before World War II

http://krisdedecker.typepad.com/.a/6a00e0099229e888330120a7d2440d970b-pi

Van running 100% on gas from coffee grounds

Wood logs to fuel vessel

Wood logs to fuel vessel

Neighbours (Finns) with cars are used renewable

fuels

http://www.youtube.com/watch?v=ayLoOnTCS8I

http://www.youtube.com/watch?v=GiPoVkocQ3w&feature=related

Thank you for your attention!