4. thermochemical biomass

8/10/2019 4. Thermochemical Biomass

1/19

10/11/2012

1

Thermochemical conversion

Eko Heryadi

Biomass conversion

Thermochemical

combustion

gasification

pyrolysis Biochemical

fermentation (bioethanol)

agrochemical (biodiesel)

anaerobic digestion (biogas)


2/19

10/11/2012

2

Thermochemical

Thermochemical

Process to convert the biomass into energy by

using a thermal application

The oldest application of man has been used

Combustion, gasification, pyrolysis the

main process of thermochemical


3/19

10/11/2012

3

Combustion

The oldest energy technology used by man

Directly burnt in presence of air

Convert into : heat, mechanical power,

electricity

Combustion application


4/19

10/11/2012

4

Direct Combustion

Unprocess biomass

Process biomass

Stages of burn (combustion process)

Drying

Devolatilization

Char combustion


5/19

10/11/2012

5

3 rules of combustion

Times

Turbulence

Temperature


6/19

10/11/2012

6

Pellet application

(small scale)

Medium to large scale combustors

The major types of large scale biomass

boilers use one of the following

technologies: grate combustion systems

(stationary or travelling), stokers,pulverised fuel (PF) systems or fluidised

bed combustion (FBC) systems.


7/19

10/11/2012

7

Grate combustors Moving grate with primary air in two stages in the grate and

secondary air

With the techniques based on grates (such as inclined grate,traveling grate, chain grate and vibrating grate), the fuel isusually fed automatically onto the grate by gravity

Temperatures above the bed and in the freeboard normallyrange between 800 and 1000C. In the stationary grate design,ashes fall into a pit for collection. In contrast, a traveling gratesystem drops the ash into a hopper.

Stokers

Spreader stokers, which feed the fuel bydistributing it on the top of the bedthroughout the furnace, and retort(underfeed) stokers are successfully used insome boilers that have been converted fromcoal firing.

Understoker furnace with primary andsecondary air, mixing zone and postcombustion chamber


8/19

10/11/2012

8

Pulverised fuel (PF) systems Wood and agricultural residues powder is attractive

for larger plants, since it allows conversion to

biomass fuels with minimal investment for boiler

conversion.

Burners for wood powder are available in the range

of 1 to 30 MW. In pulverised fuel combustion, the

fuel is introduced with air in burners similar to those

used for oil or coal burners.

Fluidised bed system


9/19

10/11/2012

9

Gasification

Gasification

Convert biomass into combustible gas mixture bypartial oxidation in high temperature, heatedinsufficient air

CO + O2 CO2C + 1/2O2 CO

CO + 1/2O2 CO2CO2 + C 2CO

CO2 + 4H2 CH4 + 2H2O (methane formed)


10/19

10/11/2012

10

Technology platforms

Three categories of gasifiers can be

distinguished:

Fixed bed gasifiers.

Fluidised bed gasifiers.

Entrained flow gasifiers.

Fixed bed gasifiersFixed bed gasifiers Fluidised bed gasifiersFluidised bed gasifiers

Application

Firing in boilers or heat applications

Gas turbine operation

Co-firing with coal

Co-firing with natural gas Gasification systems for engine operation

Methanol, hydrogen and Fischer-Tropsch


11/19

10/11/2012

11

Pyrolysis

Pyrolysis

Breaking down of material by a heat

First step in combustion process

Devolatilization in absence of oxidizer

Temperature start 350-550o

C goes up 700o

C Biomass + heat charcoal, gases, bio-oil

Char or liquid yield is optimized

Types : slow pyrolysis, fast pyrolysis, flashpyrolysis, catalytic biomass pyrolysis


12/19

10/11/2012

12

The pyrolysis process and specifically the supply of heat may becarried out in three quite different ways:

The most primitive method is to treat the biomass feedstock batchwise andgenerate the heat required for pyrolysis by burning part of the biomass withadmission of air. This is the method used in charcoal kilns. This methodgives a slow pyrolysis and is mainly useful for charcoal production eventhough tar can also be obtained as a by-product

The second type of process is used for industrial production of charcoal. Thefeedstock is heated by inert combustion gases in complete absence ofoxygen. The industrial processes are continuous and the capacity is of the

order of 1 tonne of charcoal per hour or more. Modern charcoal processesare achieves efficiencies of over 30% by weight. The pyrolysis is started byburning fuel oil, but when combustible gases are released from thebiomass, these gases are burned instead of the oil. The continuous processmakes careful control of the emissions, unlike with the batchwise process.

The third type of process uses inert solid material as an energy carrier (e.g.sand in a FBC) to heat the biomass being pyrolysed. This process is suitablewhen fast heating of the biomass is desirable, i.e. when yields of gas orliquid product are the most interesting.


13/19

10/11/2012

13

Other

Fischer-Tropsch synhesis

The Fischer-Tropsch synhesis is a process

which is converted a gases form into a

liquid hydrocarbon form bases and over a

catalyst reactions

History

-1902 : French inventor Sabatier and Senderens discover :

CO could hydrogenated over Co, Fe and Ni into Methane

-1925 : Prof.Franz Fischer and Dr. Hans Tropsch :

Synthesis of hydrocarbon liquids and solid paraffins on Co-Fe

catalyst under mild conditions of 250 300oC


14/19

10/11/2012

14

Fischer Tropsch Process

1. Synthesis gas formation

CHn + O21/2n H2 + CO

2. Fischer Tropsch reaction

2nH2 + O2 -(CH2-)n- + H2O

3. Refining

- (CH2-)n- Fuels, lubricant, etc

Catalyst

Catalyst

Catalyst


15/19

10/11/2012

15

FT reactors Two classes of reactors are used :

Multi-tubular fixed bed

Fluidized bed reactor :

two-phase circulating fluidized bed reactor

two-phase fixed bed fluidized bed reactor

three-phase slurry reactor

Multi-tubular fixed bed

consist of thousands

of narrow tubes with

surrounding water

temperature is controlled

by releasing steam when

pressure is increased

FT reactors (cont.)


16/19

10/11/2012

16

Fluidized bed reactorContains immersed cooling coils and are excellent heat exchange systems

FT reactors (cont.)

circulating fluidized bed reactor fixed bed fluidized bed reactor slurry-phase bubbling bed reactor

Fischer-tropsch catalyst

4 catalyst for commercial application

Ni, very active catalyst but has a major drawbacks :

Produces much more methane than Co and Fe

Nickel forms volatile carbonyls resulting in continuous loss

of metal at operating conditions

Ru, most active catalyst but very expensive

Fe, cheaper catalyst, will result in lower heavy

hydrocarbon

Co, has a longer life and high activity


17/19

10/11/2012

17

Products The products of FT synthesis

range from C1 to high

molecular mass waxes

Important parameter :

temperature, partial

pressures of H2 and CO, feed

gas composition,reactor used

and reduction of the catalyst

General accepted reaction pathway for

the formation of higher

hydrocarbons in FT synthesis (steyberg.2004)

Technology status and operated plants

Choren, Freiburg

Figure. BIG FT pilot plants, Choren industries, Freiberg, Germany

a) -plant, fully operasional, b) -plant, currently under construction


18/19

10/11/2012

18

Carbo-V Process for manufacturing synthesis gas from solid biomass

Carbo-V

Wood as a feedstock

Circulating fluidized

bed reactor Two separate gas

streams are produced

The sensible heat of

two streams are used

for district heating

Technology status and operated plantsTechnology status and operated plants

Repotec, Gussing, Austr ia


19/19

10/11/2012

Process flow diagram for Gussing plant, Austria

Sekian

4. thermochemical biomass

Documents