Modelling & Experimental Study of Biomass Gasifier For

8/10/2019 Modelling & Experimental Study of Biomass Gasifier For

1/22

MODELLING & EXPERIMENTAL

STUDY OF BIOMASS GASIFIERFOR ELECTRIC POWER

APPLICATION

By-

Tarun Kumar (MEB11034)

Ankur Gupta (MEB11040)

Avinash K. Singh (MEB11044)

Project Supervisor-

Partha Pratim Dutta

Assistant Professor


2/22

INTRODUCTION Biomass is biological material derived from living organisms. It most

often refers to plants or plant-based materials.

As an energy source, biomass can either be used directly viacombustion to produce heat, or indirectly after converting it tovarious forms of biofuel.

Wood remains the largest biomass energy source to date.

Gasification is a process that converts organic or fossilfuel based carbonaceous materials into carbonmonoxide, hydrogen ,carbon dioxide, methane and rest is Nitrogenin limited supply of air.

The resulting gas mixture is called syngas (from synthesis gas orsynthetic gas) or producer gas and is itself a fuel.

The power derived from gasification and combustion of the

resultant gas is considered to be a source of renewable energy if thegasified compounds were obtained from biomass.


3/22

Objective of study

Theoretical study of biomass gasification.

Experimental study of biomass gasification

for electrical application


4/22

DOWNDRAFT BIOMASS GASIFIER

Sectional view


5/22

Experimental Setup


6/22

Literature Review

Equivalence ratio ()

=(Flow rate of air supply)(Duration of the run)

(Mass input of wood)(A/F for = 1)

(A/F) for = 1 is 5.22 m3of air/kg of wood.

The equivalence ratio for the gasifier was found to be inthe range 0.2680.43, which was within the range for

ideal and theoretical gasification (0.190.43).

The average gas composition is:

1.69% O2, 43.62% N2,

14.05% H2, 24.04% CO,

14.66% CO2, 2.02% CH4


7/22

Variation of percentage of

oxygen with equivalence ratio[1]

Variation of percentage ofnitrogen with equivalenceratio[1]


8/22

Variation of percentage of

hydrogen with equivalence ratio

[1]

Variation of percentage of CO

with equivalence ratio [1]


9/22

Variation of percentage of carbon

dioxide with equivalence ratio. [1]Variation of percentage of methanewith equivalence ratio [1]


10/22

Variation of caloric value withequivalence ratio [1]

Variation of gas production ratewith equivalence ratio [1]


11/22

Variation of gas production rate per unit weight of the

fuel with equivalence ratio [1]

Therefore the optimum equivalence ratio for the best

performance of downdraft biomass gasifier is 0.388


12/22

The above experimental analysis and research

led to the following results-

Overall efficiency = 11.15 % (average)

Maximum efficiency = 15.46 %

Specific consumption of biomass material = 1.98

kg/kWh Minimum consumptions of biomass material = 1.49

kg/kWh

Carbon content in ash is about 10% of carboncontent in feed at optimum equivalence ratio.

Minimum carbon content at optimum equivalence

ratio


13/22

Steps of GASIFICATION

Drying (the moisture content of biomass we will usewill be 15%-20%)

Pyrolysis

Gasification

Combustion

BIOMASS to be used by us are---

1) Jack Fruit (Artocarpus heterophyllus)wood

2) Mango Tree (Mangifera indica) wood3) Drumstick (Moringa Oleifera) wood

4) Ashok tree (Polyalthia Longifera) wood

5) Jamun (Syzygium cumini) wood


14/22

MATHEMATICAL MODELLING [2]

The main gasification reaction is

n

H2)

H

2

+ n

CO)

CO + n

CO2)

CO

2

+ n

H2O)

H

2

O + n

CH4)

CH

4

+

z/2+3.76m)N

2

All inputs on the left-hand side of the eq. are

defined at 25C. On the right-hand side, niis thenumber of moles of the species i which areunknown.


15/22

Molar quantity of water per one kmol of biomass

can be written as

w = M

bm

x MC

M

H2O

x 1-MC)

where MC is moisture content

Mbmandare the masses of biomass and

water.

Air/fuel ratio can be calculated as +0.25-0.5)

for a fuel with a chemical formula of CHON.


16/22

The following simplified Chemical formulas describe the basic

gasification process :

1) Boudouard reaction : C + CO2 2CO

2) Water-gas reaction : C+H2OCO + H2

3)Hydrogenating gasification : C + 2H2CH4 (+75 KJ/mol)

4)Water-gas shift : CO+H2OCO2+H2 (+41.2 KJ/mol)5)Steam reforming : CH4+ H2OCO+3H2

Water gas shift reaction together with hydrogenating

gasification is chosen to play the role of two

independent equations.


17/22

These equations with their equilibrium constants generate

two of five equations required to obtain the five unknown

species of the produced syngas (H2, CO, CO2, H2O, and CH4).

The remaining three equations are formulated by balancing

each chemical element consisting of carbon, hydrogen and

oxygen.

where R is universal gas constant

GT is the standard Gibbs function of formation

Fi ll t


18/22

Finally we get

dt + I

where hfis the enthalpy/heat of formation

ALSO

where I is constant of integration

J is a const.

A, B, C and D are the coefficients for determining the

specific heats.

Having known the I and J constants together with hfandG, theequilibrium constant (k) can be determined.


19/22

For instance, the equilibrium constant for water-gas shift

reaction is obtained as follows:

If the temperature in the Gasification Zone is T and the inlet state

is

assumed to be 298 K , the enthalpy balance for this process can bewritten as

nj ( h

f,j+

hT,j) =

nj ( h

f,i+

h

T,i)where h

T

represents the enthalpy difference between any given

state and reference state.

j= react i= prod


20/22

When the equilibrium constants are defined, a system of

non linear equations are obtained which can be solved by

NewtonRaphson method together with convergencestrategies.

The equations are solved with the use of iterative

methods.


21/22

References http://www.sciencedirect.com/science/article/pii/S0961953

402000594

[1] Zainal, Z.A,Rifau, Ali, Quadir, G.A , Seetharamu, K.N.

Experimental investigation of a downdraft biomass gasifier ,

Biomass and Bioenergy 23(4) ,2002

profdoc.um.ac.ir/articles/a/1008098.pdf

[2] Vaezi,M. ,Passandideh-Fard,M. ,Moghiman ,M. ,Charmchi,

M. MODELING BIOMASS GASIFICATION:A NEW APPROACH

TO UTILIZE RENEWABLE SOURCES OF ENERGY , Energy, 2008


22/22

THANK YOU

Documents

Modelling & Experimental Study of Biomass Gasifier For