DESIGN AND TESTING OF A STRATIFIED WATER HYACINTH GASIFIER

By: Aggrey Ogola

A Research proposal submitted to Graduate School in partial fulfillment for the

requirement Masters of Science in Engineering Systems and Management of

Egerton University.

Department of Industrial and Energy Engineering

EGERTON UNIVERSITY

2008

Declaration

I hereby declare that this my original work and has not been presented or

published before.

Recommendation

I declare that this work has been presented to me

i. Prof. S. F. O Owido.

ii

Abstract

Biomass constitutes the biggest source of energy in rural areas in Africa. However, its

utilization in the domestic sector is mostly inefficient and polluting, resulting in resource

wastage, indoor and environmental air pollution. Use of energy sources such as electricity

and liquefiable petroleum gas (LPG) to eliminate air pollution and increase cooking

efficiency has failed due to sharp increase their prices, which is not affordable to many

families in rural areas. This project aims at designing and determining the performance

characteristics of a stratified gasifier that will use water hyacinth that is an environmental

problem as its source of fuel. The fabrication of the gasifier will be carried out in Eldoret

Polytechnic Engineering workshop. Determination of energy conversion efficiency to be

done using Water-boiling test (WBT). The data obtained from WBT will be recorded in a

standard data and calculation form from which burning rate, thermal efficiency, specific

fuel consumption, firepower and turn down ratio will be determined. The overall results

obtained thereafter will then be presented in a seminar.

iii

Table of content

DECLARATION................................................................................................................i

RECOMMENDATION....................................................................................................II

ABSTRACT.....................................................................................................................III

TABLE OF CONTENT..................................................................................................IV

LIST OF TABLES.........................................................................................................VII

LIST OF FIGURES.....................................................................................................VIII

LIST OF SYMBOLS....................................................................................................VIII

CHAPTER ONE................................................................................................................1

1.1 Introduction............................................................................................................1

1.2 Background of the problem..................................................................................1

1.3 Problem Statement................................................................................................3

1.4 Purpose of the Study..............................................................................................5

1.5 Objectives of the Study..........................................................................................6

1.5.1 Main objective....................................................................................................6

1.5.2 Specific objectives..............................................................................................6

1.6 Hypothesis..............................................................................................................6

1.7 Conceptual Framework.........................................................................................6

1.7.1 Theory.................................................................................................................6

1.8 Significance of the Study.......................................................................................8

1.9 Scope of the study..................................................................................................9

1.10 Limitation of the study..........................................................................................9

1.11 Assumptions...........................................................................................................9

iv

CHAPTER TWO.............................................................................................................10

2.1 Literature Review................................................................................................10

2.2 Fixed Bed Gasification System...............................Error! Bookmark not defined.

2.2.1 History..............................................................................................................13

2.3 Types of Fixed Bed Gasifier Systems.................................................................13

2.3.1 Updraft Gasification Systems.............................Error! Bookmark not defined.

2.3.2 High Temperature Agent Gasification (HiTAG) in Updraft GasifiersError!

Bookmark not defined.

2.3.3 Application of Updraft Gasifier Systems...........Error! Bookmark not defined.

2.4 Imbert Downdraft Gasification System.................Error! Bookmark not defined.

2.4.1 Modifications in Throated Downdraft Gasifier System Error! Bookmark not

defined.

2.4.2 Gasification of Non-Woody Biomass in Throated Downdraft GasifierError!

Bookmark not defined.

2.5 Throatless Downdraft Gasification Systems.........Error! Bookmark not defined.

2.5.1 Principle................................................................Error! Bookmark not defined.

2.5.2 Modifications in Design of Throatless GasifiersError! Bookmark not defined.

2.5.3 Optimization of Operating Conditions of Throatless Gasifiers............Error!

Bookmark not defined.

2.6 A Comparison of Producer Gas from Compressed Hyacinth of Up Draft and

Down Draft Furnaces......................................................................................................13

2.7 Stratified water hyacinth gasifier.......................................................................14

CHAPTER THREE.........................................................................................................16

3.1 MATERIALS AND METHODS........................................................................16

3.1.1 Design and fabrication of the gasifier............................................................16

3.1.2 Functional parts of the gasifier.......................................................................16

v

3.2 Construction Materials.......................................................................................17

3.3 Fabrication procedure.........................................................................................18

3.4 Specific objective one, determination of performance characteristics...........18

3.4.1 Test parameters...............................................................................................23

3.4.2 Data collection format.....................................................................................25

3.5 Specific objective two: Determination of energy conversion efficiency..........26

3.5.1 Water boiling test.............................................................................................20

CHAPTER FOUR...........................................................................................................26

4.1 WORK PLAN......................................................................................................26

4.2 BUDGET..............................................................................................................28

REFERENCES................................................................................................................29

APPENDICES..................................................................................................................36

APPENDIX 1. PARTS OF THE GASIFIER................................................................36

Appendix 2. Sample test data sheet................................................................................38

vi

List of tables

Table 1 List of materials needed fabricating six units of Water hyacinth gasifier............17Table 2: Operating test results of the stratified water hyacinth gasifier...........................25Table 3 Operating performance of the stratified gasifier...................................................26Table 4 Test results from water boiling test......................................................................22Table 5 Design details of the gasifier................................................................................38Table 6 Design details of the gasifier................................................................................38

vii

List of figures

Figure 1: Gasification Process (Adopted from)...................................................................8Figure 2: Updraft gasifier for high temperature air gasification (Adopted from).....Error! Bookmark not defined.Figure 3: Updraft gasifier using O2 as gasifying medium..Error! Bookmark not defined.Figure 4: Updraft gasifier for corn drying.........................Error! Bookmark not defined.Figure 5: Downdraft gasifier modified for non-woody biomass....Error! Bookmark not defined.Figure 6: Stratified Gasifier with gas recirculation...........Error! Bookmark not defined.Figure 7: Stratified downdraft gasifier using wood pellets............Error! Bookmark not defined.Figure 8: Throatless gasifier for gasification of rice husk Error! Bookmark not defined.Figure 9: Proposed Stratified gasifier...............................................................................15Figure 10: Part of the gasifier reactor not drawn to scale. All dimensions in mm............36Figure 11: Detail of the char chamber not drawn to scale (All dimensions are in mm)....37

viii

List of symbols

η - Gasification efficiency (η)

List of Abbreviations/Definitions

- Specific Gasification Rate

- Fuel Consumption Rate

- Equivalence Ratio

- Turn-Down ratio

- Water Boiling Test

- Controlled Cooking Test

– Liquefiable Petroleum Gas

- Kitchen Performance Test

- Gross calorific value (dry hyacinth)

- Net calorific value (dry hyacinth)

– Hyacinth moisture content (% - wet basis)

- Effective calorific value

- Dry weight of empty Pot (grams)

- Weight of empty container for char

- Local boiling point of water

– Burning rate

– Dry hyacinth consumed

– Time at start of test (min)

– Time at end of test (min)

- Specific fuel consumption

– Equivalent dry hyacinth consumed

– Weight of pot with water after test (g)

– Weight of pot (g)

- Firepower

PHU - Percent Heat Utilized

- Mass of dry fuel in kg

ix

-calorific value of dry fuel KJ/kg

-Net weight of charcoal remaining in kg

-Calorific value of charcoal in KJ/kg

- Mass of water used in kg at start

- Mass of water in kg at finish

- Temperature of water in 0C at start

- Temperature of water in 0C at finish

- Hydrogen sulphite

- Methane

– high temperature agent gasification

x

CHAPTER ONE

1.0 Introduction

1.1 Background of the problem

More than 50% of the world’s populations rely on dung, wood, crop waste or charcoal to

meet their most basic energy needs. Cooking and heating with such solid fuels on open

fires or stoves without chimneys leads to indoor air pollution. (WHO 2005) The use of

polluting fuels thus poses a major burden on the health of poor families in developing

countries. (UNDP, 2005).

It is currently estimated that around two-thirds of all households in the developing

countries still rely primarily on unprocessed biomass fuels (wood, dung, charcoal, crop

residues) for their daily cooking and heating needs (World Resources Institute, 2005). In

many of these households, fuel, is burnt indoors on open fires or poorly functioning stoves,

often with no means of ventilation or smoke extraction. Consequently, very large numbers

of women and young children are exposed to high levels of air pollution, every day of the

year. Indeed, it has recently been argued that the greatest global burden of air pollution

exposure occurs not outdoors in the cities of the developed world, but indoors in poor rural

communities (WHO 1997). The survey carried out in Western Kenya, Nyanza and Kajiado

revealed that women and children suffer from illnesses resulting from indoor air pollution

and this has lead subsequent death. (WHO 2005)

Access to electricity in Kenya is only up to 15% of the households in urban areas and 4%

in rural areas, and less than 1% uses it for cooking. The remaining households rely on

traditional fuels for cooking and heating. (Pisces 2008)

More than 80% of Kenya rural populations depend on biomass (dung, wood, crop residues

or charcoal) to meet their most basic domestic energy needs. (WHO, 2005) Cooking and

heating with such solid fuels on open fires or stoves without chimneys leads to indoor air

pollution. This indoor smoke contains a range of health-damaging pollutants including

small soot or dust particles that are able to penetrate deep into the lungs. In poorly

ventilated dwellings, indoor smoke can exceed acceptable levels for small particles in

outdoor air. (WHO/UNDP, 2004) Exposure is particularly high among women and

children, who spend the most time near the domestic hearth. Every year, indoor air

1

pollution is responsible for the death of 1.6 million people i.e. one death every 20 seconds.

(WHO, 2005)

Rural Kenya has been the site of various applied research projects to determine the

intensity of emissions that commonly occur from use of biomass fuels, particularly wood,

charcoal, dung, and crop residue. Smoke is the result of the incomplete combustion of solid

fuel which women and children are exposed to up to seven hours each day in closed

environments. (Kammen, 2003)

There is now consistent evidence that indoor air pollution (IAP) increases the risk of

childhood acute respiratory infections, the most important cause of death of children below

five years in Kenya and there is association with birth weight, infant and prenatal

mortality, pulmonary tuberculosis and some forms of cancer. Although the risks are poorly

quantified, indoor air pollution may be responsible for nearly two million excess deaths in

Least Developed Countries (LDCs), and around 4% of the global burden of disease

(Bruce, Perez-Padilla, Albalak, 2000).

In Kenya, the reliance on biomass fuels appears to be growing because of population

growth and the unavailability of or increases in the price of alternatives such as kerosene

and liquid petroleum gas. Despite the magnitude of this growing problem, the health

impacts of exposure to indoor air pollution have yet to become a central focus of research

development aid and policy-making. (WHO, 2005) This research focuses on the

elimination of biomass fuel that causes indoor air pollution with a cleaner technology using

the process of gasification. Biomass gasification is a process that converts carbonaceous

materials, such as coal, petroleum, or biomass, into carbon monoxide (CO), hydrogen (H2)

and traces of methane(CH4) by reacting the raw material at high temperatures with a

controlled amount of oxygen and/or steam. The resulting gas mixture is called synthesis

gas (syngas) or producer gas and is itself a fuel. Gasification is a very efficient method for

extracting energy from many different types of organic materials, and has applications as a

clean waste disposal technique. (Bhattacharya et al. 2003)

This research aims at designing and testing a water hyacinth gasifier, compares its energy

conversion efficiency and emission characteristics with those of the traditional woodstove

(three-stone fire), charcoal stove (jiko) and paraffin stove.

2

1.2 Problem Statement

An overview of the energy sector in Kenya shows that wood fuel is the largest form of

energy consumed in Kenya accounting for about 68% followed by Petroleum and then

electricity accounting for 22% and 9% respectively. Other sources of energy including

solar, wind, biogas, bagasse and micro-hydropower together accounting for the remaining

1 %.( Mbuthi, 2005) Kenya’s pre-dominant energy source is biomass, providing more than

90 per cent of rural household energy needs, about one-third in the form of charcoal and

the rest from firewood. (UNDP, 2005)

Because many Kenyan women in the rural areas utilize a three-stone fire, one kilogram of

burning wood produces tiny particles of soot, which can clog and irritate the bronchial

pathways. The smoke also contains various poisonous gases such as carbon monoxide

(CO), nitrogen oxides, sulphur dioxides and benzene. This has led to indoor air pollution

(IAP). Indoor air pollution is the presence of one or more contaminants indoors that carry a

certain degree of human health risk.

Various studies show that people spend 65 to 90 percent of their time indoors; 65 percent

of that time is spent at home. Field studies of human exposure to air pollutants indicate that

indoor air levels of many pollutants may be two to five times, and on some occasion more

than one hundred times, higher than outdoor levels. (Pisces 2008)

Exposure to indoor air pollution (IAP) from combustion of solid fuels has been implicated,

with varying degrees of evidence, as a causal agent of several diseases. (Ezzati et al, 2002).

Acute lower respiratory infections (ALRI) and chronic obstructive pulmonary disease

(COPD) are the leading causes of disease and death from exposure to smoke. (WHO,

2005) There is mounting evidence that the resulting indoor air pollution (IAP) increases

common serious health problems, including childhood pneumonia and chronic lung

disease. Previous attempts to reduce this have often failed due to lack of community

involvement in developing appropriate sustainable solutions which depend on biomass

(wood, dung, crop residues) for domestic energy.

The current conventional energy sources (kerosene, liquefiable petroleum gas and

electricity) are not easily accessible to many communities in the rural areas in Kenya due

to the increase in their prices while the increasing scarce wood fuel resources are

3

combusted in traditional devices (stoves) that are characterized by low efficiency and

emission of pollutants. (Bhattacharya et al. 2003)

The table below shows the amount of pollutants found in one kilogram of wood per hour in

mg/m3 emitted from kitchen from a survey carried out in western Kenya using firewood

Table 1:

Pollutants Emissions (mg/m3) Allowable standards

(mg/m3)

Carbon dioxide 150 10

Particles 3.3 0.1

Benzene 0.8 0.002

Sulphur dioxide 0.002 0.0003

NOx 0.7 0.1

Source: Based on the UNDP/DESA/WEC World Energy Assessment

Records from a survey taken from Kisumu and Kajiado reflect the impact of kitchen smoke

on the health of women and their children. Table 2 below is a summary of the health

problems reported by the cooks in the questionnaires, and is intended to give an overview

of the smoke-related health problems experienced in each community. (Source)

Table 2. Health problems identified by the cooks

Problem Complication Kajiado KisumuNo. of

records% with

ProblemNo. of records

% with Problem

Cough i) First thing in the morning 74 24.32 97 16.49ii)During day (or at night in wettest coldest season)

65 27.69 76 21.05

If 'yes' to i) or ii), cough most days for up to 3 months a year

23 26.09 26 26.92

Phlegm i)From chest in the morning during cold/wet season

73 20.55 102 20.59

ii)During day (or at night in wettest coldest season)

70 21.43 87 21.84

If 'yes' to i) or ii), phlegm most days for up to 3 months a year

17 5.88 44 13.64

4

Cough & phlegm

In last three years, cough and phlegm together lasting 3 weeks or more

73 13.70 98 18.37

Wheezing Wheezing or whistling in chest in last 12 months

74 13.51 79 24.05

Woken up last 12mths at night with shortness of breath

73 10.96 90 27.78

Chest illness During past 3 years preventing usual activities for as much as a week

74 17.57 78 28.21

TB Ever been told by a doctor that suffering from tuberculosis

74 0.00 98 4.08

Eyes Red, watering eyes sometimes or much of time

47 55.32 67 17.91

Sore, sometimes or much of time

47 27.66 66 13.64

Swollen, sometimes or much of time

47 12.77 66 10.61

Affected by light, sometimes or much of time

47 61.70 64 20.31

Vision impaired, sometimes or much of time

47 29.79 67 38.81

Source: Reducing indoor air pollution in rural households in Kenya:

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1.3 Objectives of the Study

1.3.1 Main objective

The general objective of this research will be to design and test a stratified water hyacinth

gasifier.

1.3.2 Specific objectives

i. Compare energy conversion efficiency of the stratified water hyacinth gasifier with

those of the traditional woodstove (three-stone fire), charcoal stove (jiko) and

paraffin stove.

ii. To determine the emission characteristic of the stratified water hyacinth gasifier

and compare with those of the traditional woodstove (three-stone fire), charcoal

stove (jiko) and paraffin stove.

1.4 Research Hypothesis

HO1: The conversion efficiency of stratified water hyacinth gasifier varies

significantly compared with other stoves. (Woodstove, charcoal stove, and

paraffin stove)

H02: The emission characteristics of the stratified water hyacinth varies

significantly compared to other stoves (woodstove, charcoal stove, and

paraffin stove)

1.5 Significance of the Study

In developing countries, biomass is the predominant form of energy and accounts

for about 38 % of their primary energy consumption and in rural areas 90 % of

their total energy supplies. (Kucuk et al 1997, Sims 2003 and Pathak, 2005). The

use of biomass to generate energy for heating and cooking processes in traditional

devices (stoves) are characterized low efficiency and emission of pollutants leading

indoor air pollution that has affected the health of women and children who spend

hours cooking indoors. (Young-Zhi Ren. 2005) The use of Liquefiable Petroleum

Gas (LPG) and electricity which are clean and efficient sources of energy have

6

their prices increasing by 20% and 28% respectively every year thus becoming

unaffordable to people leaving in the rural areas (Ramirez et al. 2007)

A well-designed gasifier that produces clean gas for heating and cooking processes

will solve the energy crisis and health problems of the people leaving along the lake

side where water hyacinth to be used as fuel is equally an environmental problem.

Water hyacinth has caused problems to the people leaving along the lakeside such

as hindrance to water transport, clogging of intake of irrigation, and hindrance to

fishing.

1.6 Research Justification

The domestic use of water hyacinth as source energy in Kenya would provide the

following advantages:

i. Affordable renewable source of energy would improve both domestic and

industrial growth and this translates into reduction of commodity prices. Domestic

users of water hyacinth as a fuel would be less vulnerable to price manipulations or

unexpected disruption of supplies of fossil of fuel.

ii. Production of renewable energy particularly biomass based energy, would save the

foreign exchange earnings due to high rising cost of oil. In 1980, biomass energy

provided close to 77% of Kenya’s national energy requirements, petroleum fuels

provided close to 20% and electricity 1.2% (Watubengo, 2004)

iii. The use of water hyacinth would reduce the dependency on wood fuel as a source

of renewable energy. This will reduce the wide spread and overexploitation of

deforestation and desertification that are potentially very serious in the long term.

1.7 Scope of the study

The proposed study will focus stratified gasifier to use water hyacinth as its source

of fuel. This research work aims at designing, fabricating and testing a stratified

water hyacinth gasifier. The testing will comprise of a series of experiments to

compare the energy conversion efficiency of the designed gasifier with the

traditional woodstove (three stone fire), charcoal stove (jiko) and paraffin stove

using three method namely water boiling test, controlled cooking test and kitchen

performance test. The emission characteristics of the gases produced by the gasifier

7

will be analyzed and compared by those wood stove, charcoal stove and paraffin

stove.

1.8 Limitations

Reliable sampling and analysis of products from biomass gasification are essential

for the successful process development and economical operation of a gasifier. One

of the most important and difficult analytical tasks is to characterize the emission

from the gasifier. (Stahlberg et al 1998).

The equipment for carrying out the analysis of the pollutant emission from biomass

gasification is very expensive and is not available locally. Due to lack of

availability of funds, this research will carry out test on the composition of

individual gases in the producer gas by percentages and not impurities, which are

formed during gasification process.

These effluents include particles entrained from the gasifier that is low and high

molecular mass organic compounds (tars), hydrogen sulphite (H2S) and other

nitrogen containing impurities.

8

1.9 Assumptions

This research project work will be carried out based on the following assumptions

1) The combustion properties of water hyacinth are the same as those of other

fuels.

2) The bio-waste gasifier will operate at the optimal operation point where just

enough oxygen is added to avoid solid carbon formation

9

CHAPTER TWO2

2.0 Literature Review

2.1 Introduction

Bio-energy is the energy recovered from biomass that is initially stored as chemical

by plants. Before the discovery of fossil fuels, biomass supplied all the energy for

all both industrial and domestic activities. Wood is still the most significant fuel

source in developing countries accounting for 35% of their demand. Biomass fuels

include urban refuse, industrial waste, agricultural waste animal waste and sewage

sludge. In addition to the benefits of power generation, energy from waste plants

can dramatically reduce the volume of waste to be disposed off in the landfill sites.

In particular, household and industrial wastes are in many cases being deposited in

landfills at a considerable financial and environmental cost. (Hall and Overland).

2.2 Current Biomass Situation.

In the 1995 biomass, derived energy was about 930 million tones oil equivalent

virtually all from the direct combustion. This is about 14% of consumption.

Ironically, its share of the world energy market has declined since the nineteenth

century, although actual quantities consumed have increased. Its share is now on

the increase again, mainly due to population growth in the rural economies but also

because of environmental concern for fossils in the industrialized world. Current

consumption in industrialized countries is low, whereas some African countries for

example Angola, Ethiopia, Kenya and Congo rely on this type of fuel for 80-90%

of all energy needs. Biomass represents similar proportions in the poorest Indian

sub-continent for example Napal and Bangladesh (Atkins et al, 1996)

10

2.2.1 Environmental Impact

Biomass energy source is now strongly linked to environmental impact. Biomass

energy is carbon dioxide neutral with the alternate reduction (fixation) and

oxidation (release) of carbon and thus the benefits from biomass is as a replacement

for fossil fuel. However, biomass conversion to liquid fuel such as gasohol and bio

diesel may be negative and create problems such effluent to side stream (Atkinson

et al, 1996)

Biogas generation has similar problems; the conversion of sludge gas is only 50%

efficient and achieves a lower degree of pasteurization than the alternative

incineration that generates a toxic ash residue. Fundamentally, biomass has two

major problems: one is the high water requirement and content, the other is the

slow growth and yield from photosynthesis (about 1% efficient). Food growth in

developing and bioconversion of habitat in industrialized countries will create

alternative demands on agricultural land. There will also be strong completion from

improved energy efficiency, clean burn and other renewable. (ENDS Report 257,

1997)

2.2.2 Biomass processing

The water content of the biomass is also a basic to the choice of fuel produced e.g.

dry homogenous biomass will be mostly efficiently converted into energy by direct

combustion or co-combustion with fossil fuel. Hydrocarbons content of biomass

can be enriched and modified to produce premium bio-fuels such as oils and gases.

This often resembles an accelerated fossilization process using hot flushing without

oxygen to avoid combustion i.e. pyrolysis. (Mulder E, 1996)

2.2.3 Global Biomass Energy

Biomass was the first fuel used for major energy by humanity and has

predominated through history as a major resource. However, the rise in the global

consumption of fossil fuels since the industrial revolution has seen a decline in the

use of biomass as primary source in the developed world. The use of biomass is

11

dependent of a number of factors, which include; wealth and population of a

country living in urban and rural areas.

About 70% of domestic energy in developing countries is derived from biomass. In

sub-Sahara, this can be over 90% of the fuel available for heating and an estimated

2.4 billion people rely on non-commercial biomass for fuel. This type of biomass

depends upon availability and cultural values e.g. in China half of biomass use

comes from agricultural residue and South Asia animal dung and crop residue

accounts for half the biomass. Whereas in South America and sub-Sahara the

majority of biomass used is wood fuel or charcoal.

Because of the dominance biomass in the developing countries, it would be

appropriate to develop technologies to improve the efficiency of energy production.

This is important, as the growing population does not only need biomass energy,

but also food from agricultural land. It has been estimated that improvements in

energy efficiency of biomass energy production could save 326 million tones of

biomass fuel per year from residential and commercial activities. This would

include 152 million tone of residential wood fuel. (IEA, 2000)

2.2.4 Direct Combustion of biomass

The combustion process for biomass fuel is consisting of three main stages namely

drying, pyrolysis and oxidation. The effect of each stage on the overall efficiency

of the combustion process will depend on the fuel moisture content, calorific value

of dry matter, ash content, content of volatile matter and particle size and size

variation.

12

2.3 Performance of Compressed Hyacinth of Up Draft and Down Draft Furnaces

This research is to study the production of producer gas from up-flow and down-

flow gasifier using compressed water hyacinth as fuel. Airflow rates in each

gasifier were adjusted in three levels as follow: up-flow gasifier 3.59 x, 4.31 x and

5.03 x m3/s; down-flow gasifier 2.33 x, 3.42 x and 4.66 x m3/s. The results were

compared to investigate tile optimum heat condition by using gas chromatography.

The experimental results showed that the up flow gasifier provided high heating

value 4545.9 kJ/Nm3 at the air flow rate 4.31 x m3/s and down-flow gasifier

provided high heating value 2135.76 kJ/Nm3 at the air flow rate 3.42 x m3/s. It

could be concluded that the producer gas from up-flow gasifier at airflow rate 4.31

x m3/s should be utilized as it provided highest heating value. (Klaimukh 2007)

2.4 Stratified water hyacinth gasifier

This research work aims at using stratified downdraft gasifier because of several

advantages over the others. Stratified downdraft gasifiers consist of cylindrical

vessel with a hearth at the bottom. During the operation of a stratified downdraft

gasifier, air and biomass pass uniformly through four zones hence the name

stratified. Open top ensures uniform access of air or oxygen to the flaming

pyrolysis zone and permits the fuel to be fed more easily. It also allows easy access

for instruments to measure conditions within the bed. The uppermost layer is

composed of unreacted biomass fuel through which air enters. The uniform passage

of air and fuel down the gasifier keeps local temperatures from becoming either too

high or too low while the average temperature is high. The cylindrical construction

is easy to fabricate and permits continues flow for otherwise troublesome fuels

without causing bridging or channeling. Finally, the various strata are more

accessible for measuring compositions and temperatures within the bed so that it is

possible to compare modeling results with empirical observation. (Citation)

The choice for a given design of gasifier depends on several factors such as the

type of biomass, the moisture content, and energy content of the fuel. Water

hyacinth as biomass has proved to have a considerable high heating value of

13

4545.9KJ/Nm3 at flow rate 4.31m3/s. after several prototypes were tested in both

updraft and downdraft gasifiers (Klaimukh 2007) .

Entry point

They reach this conclusion it seems after deciding that chimneys just divert

smoke so that now it pollutes the overall environment, while the other

possibility (in my opinion) is that we can design more efficient biomass

stoves so that the smoke (a combustible gas in most cases) is burned inside

the stove to extract the maximum energy from the fuel. A central problem

not addressed by WHO is that modern fuels need to be purchased (and

petroleum based ones are non-renewable), while the people using wood

stoves tend to do so because the fuel is free or available at a low cost.

Figure 1: Proposed Stratified gasifier

14

CHAPTER THREE3.0

Methodology

Experimental location

This research will be carried in the Department of Industrial and energy

Engineering laboratory. The stratified gasifier will be used to analyze the

combustion characteristics of water hyacinth under different condition.

The analysis of the producer gas will be done at Moi University in the department

of Environmental and Natural resources. Water Boiling Test (WBT) will to be used

in determination of energy conversion efficiency and will be carried out at the

Eldoret Polytechnic in the department of Chemical Engineering. Controlled

Cooking Test (CCT) and Kitchen Performance Test (KPT) will carried out in

several homestead along the shores Lake Victoria in Kisumu.

Research Materials and Equipment

Approximately 10m3 of dried Water hyacinth will be required to carry out the

experiment. This will be harvested from shores of Lake Victoria and will be dried

in the sun until it attains a moisture content of approximately 14%, which is

recommended for the performance. The dried water hyacinth then is chopped to

approximately 10mm in size. A gas analyzer will be use to analyze the composition

of the producer gas (CO, CO2, CH4, NOX). Standard sheets for Water Boiling Test

(WBT), Controlled Cooking Test (CCT) and Kitchen Performance Test (KPT) will

be used to record date collected during the performance of the experiment.

Functional parts of the gasifier.

a) Reactor

This is the compartment in which water hyacinths is gasified. The wider the cross-

sectional area of the reactor, the stronger the power output of the stove. Uniform

gasification can be achieved when the reactor is designed in circular rather than in

square or in rectangular cross section.

b) Char chamber

15

The char chamber serves as the storage for char produced after each operation. It is

located beneath the reactor to easily catch the char that is falling from the reactor.

This chamber is provided with a door that can be opened for easy disposal of char

and it must be kept always closed when operating the gasifier. The char chamber is

tightly fitted in all sides to prevent the air given off by the fan from escaping the

chamber hence, minimizing excessive loss of draft in the system in gasifying the

fuel.

c) Burner

The burner design affects the quality of burning gas in the stove. The size and the

number of holes in the burner affect the amount of gas generated by the stove. The

holes should be closer as possible, at about 1/8 inch distance, to allow proper

burning of gas in the burner. Secondary air should also be provided for the

combustible gas to improve the combustion of the fuel. Moreover, the gap between

the pot hole and the burner should not be too narrow in order to avoid quenching of

the combustion of fuel neither should it be too wide in order to limit the heat

released from the stove

d) Support legs.

Support legs with rubber caps are provided beneath for the chamber to support the

entire gasifier.

Construction Materials

The Water hyacinth gasifier will require the following materials for its fabrication:

Table 1 List of materials needed fabricating six units of Water hyacinth gasifier

Quantity Unit Description.3 Sheets Mild Steel gauge 131 Piece Stainless Steel Plate gauge 222 Length Mild Steel pipe ½ inch2 Length Mild steel rod 5/16 inch2 Pieces Mild steel rod 3/16 inch2 Feet Stainless Steel rod ¼ inch4 Pieces Thermocouples 2 Pieces Switches4 Pairs Hinges4 Pieces Lock

16

2 Liter Enamel Paint12 Pieces Rubber shoes6 Pieces Hooks 2 Sacks Water hyacinth

As shown, the list of materials may include materials to be fabricated such as metal

sheets and bars, and standard materials such as hinges, door lock, switches, and

rubber shoes.

Mild steel sheet will be used for the construction of the reactor and the char

chamber. For the burner assembly the outer cylinder will be made by mild steel

sheet material with the same gauge as that of the reactor. The inner cylinder, the

part of the burner, which is directly in contact with the flammable gases, requires

stainless steel because of its good resistance to heat. The pot support, the handle of

the burner assembly including the frame for the char grate and the lever will be

made of mild steel rod for better durability.

Fabrication procedure

Layout of each of the different components of the gasifier will be made on a metal

sheet. For six units of the stove, two mild steel sheets and a sheet of stainless steel

are needed.

The metal sheet will be cut according to the dimension specified in the layout using

a tin snip. For thicker materials, use of bench snip cutter will facilitate cutting of

the metal sheet.

Metal sheets will be rolled with a rolling machine in forming the inner and the

outer cylinders of the reactor, as well as the cylindrical parts of the burner

assembly. Welding will be done to all parts that need to be joined together. Oxy-

acetylene welding unit is advisable for welding thinner metal sheets, particularly in

forming the inner reactor and the burner assembly where proper sealing is required.

The outer reactor, char chamber, pot holder, support legs, char frame, and grate

lever will be welded using the arc-welding machine. After all the different parts are

properly welded and constructed to the desired form, the surface of the welded

parts will be smoothened using a portable electric grinder. The outer surface of the

gasifier will then be painted.

17

Experimental Procedure

Standard testing protocol series (2003) developed by University of California at

Berkeley will be used to determine the energy conversion efficiencies of the

stratified water hyacinth gasifier.

In this protocol, the following are identified as indicators of gasifier performance:

i. Burning rate

ii. Efficiency

iii. Specific fuel consumption

iv. Turn-Down ratio (TDR)

In this protocol, the following three stove performance tests are recommended to

evaluate the indicators of performance

i. Water Boiling Test (WBT).

This is a laboratory based test which provides four (4) of the six (6) indicators of

stove performance i.e. thermal efficiency, fuel consumption, turn down ratio and

speed of cooking. The goal in this test is to measure fuel consumption and time to

boil water under a variety of conditions. Each water-boiling test consists of three

parts: high power cold start, high power hot start, low power (simmer).

ii. Controlled Cooking Test (CCT).

The goal in this test is to measure fuel consumption and time to cook a typical

meal. It is similar to a lab-controlled test and it is used to compare stoves

performing the task of cooking the same meal. The controlled cooking test (CCT)

is designed to assess the performance of the improved stove relative to the common

or traditional stoves that the improved model is meant to replace. Stoves are

compared as they perform a standard cooking task that is closer to the actual

cooking that local people do every day. However, the tests are designed in a way

that minimizes the influence of other factors and allows the test conditions to be

reproduced.

18

iii. Kitchen Performance Test (KPT).

The Kitchen Performance Test (KPT) is the principal field–based procedure to

demonstrate the effect of stove interventions on household fuel consumption. There

are two main goals of the KPT: (1) to assess qualitative aspects of stove

performance through household surveys and (2) to compare the impact of improved

stove(s) on fuel consumption in the kitchens of real households. To meet these

aims, the KPT includes quantitative surveys of fuel consumption and qualitative

surveys of stove performance and acceptability. This type of testing, when

conducted carefully, is the best way to understand the stove’s impact on fuel use

and on general household characteristics and behaviors because it occurs in the

homes of stove users.

3.1.1 Water Boiling Test (WBT)

Water Boiling Test procedure:

1) Same pot will be used in all tests (to be carried out indoor) for all types of

stoves.

2) A constant uniform amount (same weight, species and sizes) of fuel will be

used in each type of stove.

3) The pots will be filled with a constant amount of water.

4) Water temperature T1 will then be determined and fire started in a

reproducible manner.

5) High Power Phase: Stoves will be started at room temperature and water

temperature recorded every five minutes as water is brought as rapidly as

possible to a boil without being wasteful of heat.

6) When the water boils, amount of fuel used and time to boil will be recorded.

7) Low Power Phase: The heat will then be reduced so that water remains at

boiling point and remaining fuel used until it is all used up and the time

recorded.

8) The flame is then extinguished, the pot removed from the stove and the

remaining water measured. The amount of charcoal left will then be

weighed.

19

9) A minimum of three trials will be necessary for each loading capacity.

10) In this test, the following variables are considered constant throughout each

phase.

i. HHV - Gross calorific value (dry hyacinth) (MJ/kg)

ii. LHV - Net calorific value (dry hyacinth) (MJ/kg)

iii. m – Hyacinth moisture content (14 % - wet basis)

iv. Ceff - Effective calorific value (accounting for moisture content of hyacinth)

v. P - Dry weight of empty Pot (grams)

vi. k - Weight of empty container for char (grams)

vii. Tb - Local boiling point of water (deg C)

The following indicators will then be calculated using the formulae as shown

below:

Burning rate Rcb: This is a measure of the rate of hyacinth consumption while

bringing water to a boil. It is calculated by dividing the equivalent dry hyacinth

consumed by the time of the test.

Where – burning rate (Kg/min)

– Dry hyacinth consumed (Kg)

– Time at start of test (min)

– Time at end of test (min)

Specific fuel consumption : This is the fuel required to produce a unit output i.e.

it is a measure of the amount of hyacinth required to produce one liter (or a kilo) of

boiling water starting with cold stove

Where – Equivalent dry hyacinth consumed

– Weight of pot with water after test (g)

– Weight of pot (g)

20

Firepower : This is a ratio of the wood energy consumed by the stove per unit time. It tells the average power output of the stove (in Watts) during the high-power test.

Percent Heat Utilized (PHU) is a measure of the energy conversion efficiency. It is the

ratio of energy into a cooking task (e.g. to boil water) to that of energy in fuel used and is

given by:

= mass of dry fuel in kg

= calorific value of dry fuel KJ/kg

= net weight of charcoal remaining in kg

= calorific value of charcoal in KJ/kg

= mass of water used in kg at start

= mass of water in kg at finish

= temperature of water in 0C at start

= temperature of water in 0C at finish

4.186KJ/kg0C = specific heat capacity of water

2260KJ/kg = latent heat of vaporization of water

3.1.2 Controlled Cooking Test. (CCT)

Test procedure

i. The first step in conducting the CCT is to consult with people in the location where

the gasifier is going to be introduced in order to choose an appropriate cooking

task. This should be done well ahead of time, to ensure that sufficient food can be

obtained to conduct all of the necessary tests.

ii. After deciding on a cooking task, the procedure should be described in as much

detail as possible and recorded in a way that both stove users and testers can

understand and follow. This is important to ensure that the cooking task is

performed identically on each stove. If possible, include an objective measure of

21

when the meal is “done”. In other words, it is preferable to define the end of the

cooking task by an observable factor like “the skins come off the beans” rather than

a subjective measure like “the sauce tastes right

After sufficient ingredients and fuel have been obtained and the steps of the

cooking task are written up and well understood by all participants, the actual

testing can begin. The cooking itself should be done by a local person who is

familiar with both the meal that is being cooked and the operation of the stove to be

tested. If the stove is a new design that differs significantly from traditional

cooking practices, some training will probably be required before conducting the

actual tests. When comparing stoves with the CCT, if more than one cook is used,

each cook should test each stove the same number of times, in order to remove the

cook as a potential source of bias in the tests. In addition, to ensure that the testers

have control over the testing environment, the tests should be conducted in a

controllable setting such as a lab or workshop rather than in a private home.

iii. Record local conditions as instructed on the Data and Calculation form.

iv. Weigh the predetermined ingredients and do all of the preparations (washing,

peeling, cutting, etc). To save time, for non-perishable food, the preparation can be

done in bulk, so that food for all of the tests is prepared at once.

v. Start with a pre-weighed bundle of fuel that is roughly double the amount that local

people consider necessary to complete the cooking task. Record the weight in the

appropriate place on the Data and Calculation form.

vi. Starting with a cool stove, allow the cook(s) to light the fire in a way that reflects

local practices. Start the timer and record the time on the Data and Calculation

form.

vii. While the cook performs the cooking task, record any relevant observations and

comments that the cook makes (for example, difficulties that they encounter,

excessive heat, smoke, instability of the stove or pot, etc).

viii. When the task is finished, record the time in the Data and Calculation form (see the

comments on determining when the task is complete in step 2 above).

ix. Remove the pot(s) of food from the stove and weigh each pot with its food on the

balance. Record the weight in grams on the Data and Calculation form.

22

x. Remove the unburned wood from the fire and extinguish it. Knock the charcoal

from the ends of the unburned wood. Weigh the unburned wood from the stove

with the remaining wood from the original bundle. Place all of the charcoal in the

designated tray and weigh this too. Record both measurements on the Data and

Calculation form.

xi. The test is now complete – you may now enjoy the food that was cooked or

proceed by testing the next stove – each stove should be tested at least 3 times.

Specific objective two: Determination of emission characteristics.

3.1.3 Test parameters

The following parameters are used in evaluating the performance of the gasifier

1. Start-Up Time (T1) – This is the time required to ignite the water hyacinth and

consequently to produce combustible gas. This parameter is measured from the

time the burning pieces of paper are introduced to the fuel in the reactor until

combustible gas is produced at the burner.

2. Operating Time (T2) – This is the duration from the time the gasifier produces a

combustible gas until no more gas is obtained from the burning water hyacinth.

3. Total Operating Time (T3) – This is the duration from the time water hyacinth is

ignited, until no more combustible gas is produced in the stove. It is the sum of the

startup time and the operating time of the gasifier.

4. Fuel Consumption Rate (FCR) – This is the amount of water hyacinth fuel used

in operating the stove divided by the operating time. This is computed using the

formula,

5. Specific Gasification Rate (SGR) – This is the amount of water hyacinth fuel

used per unit time per unit area of the reactor. This is calculated using the weight of

dry water hyacinth gasified for a run, net operating period and cross sectional area

of the reactor. This is computed using the formula,

23

6. Equivalence Ratio (ER)

This is the actual air used in a run to stiochiometric air requirement for the run.

This is computed the formula,

7. Gasification efficiency (η)

This the percentage of energy of the water hyacinth converted into cold producer

gas (free from tar). The expression below is used to compute gasification

efficiency.

24

3.1.4 Data collection

Determination gasifier performance in the laboratory

Results of the performance testing of the gasifier will be carried out in laboratory. This will

be done in three modes that is, on full load, three quarter load and half load. In each mode

three trials will be recorded as shown in table 2 below

Table 2: Operating test results of the stratified water hyacinth gasifier

Loading Capacity

Weight Of Fuel

(Kg)

Fuel Start Up Time

(Min)

Gas Ignition Time

(Sec)

Total Operating Time(Min)

Full Load

Trial 1Trial 2

Trial 3Average¾ Load

Trial 1

Trail 2

Trial 3

Average

½ Load

Trial 1

Trial 2

Trial 3

Average

25

Table 3 Operating performance of the stratified gasifier

Loading capacity Fuel consumption rate. (kg/hr)

Char produced(%)

Specific gasification rate(Kg/hr-m2 )

Full Load

¾ Load

½ Load

Table 4: Power Output and efficiency of the stove.

Loading Capacity

Power Input(kW)

Thermal Efficiency (%)

Power output(kW)

Full Load

¾ Load

½ Load

Expected Results

1) Determination of the amount of energy that can be produced by water hyacinth

would lead to the use of water hyacinth as an alterative source of renewable energy

in Kenya.

2) Determination of emission characteristics of water hyacinth for the formation of

pollutant gases will allow for the safe use of water hyacinth without polluting the

environment.

3) Utilization of water hyacinth as a source of energy will reduce the dependency on

wood-biomass as a source of energy in Kenya.

4) Savings from reduced important of fuel can be used to expand enterprises that

would create employment opportunities in Kenya.

5) Commercialization of water hyacinth will generate additional income to farmers

living along the lake region.

Specific objective two: Determination of energy conversion efficiency

26

CHAPTER FOUR

4.0

WORK PLAN

Year 2008 2009Month N D J F M A M J J A S O NNumber 1 2 3 4 5 6 7 8 9 10 11 12 13

1 Problem Definition2 Literature Review3 Methodology4 Work plan5 Budget6 Design of Gasifier7 Fabrication8 Testing of Gasifier9 Analysis &

Evaluation10 Conclusion11 Presentation

27

BUDGET

Description Cost in Ksh.1. CommunicationE mail and internet browsing 10,000Internet modem 3,000Phone 1,000Sub total 14,0002. Stationary Flash disk 1,000Printer cartridge 3,000Printing papers 5,000Binding 1,000Sub total 9,0003. Traveling 10,0004. Construction of prototypeConstruction of materials 25,000Tools and equipment 8,000Labour 5,000Sub total 38,0005. Testing and analysisTesting equipment 20,000Total 81,0006. Contingency (10% of total) 8,100Grand total 89,100

28

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Appendices

Appendix 1. Parts of the gasifier

Figure 2: Part of the gasifier reactor not drawn to scale. All dimensions in mm

36

Figure 3: Detail of the char chamber not drawn to scale (All dimensions are in mm)

37

Appendix 2. Sample test data sheet

Water boiling test

Date :

Place :

Tester :

Table 4 Design details of the gasifier

Stove model

Fuel reactor diameter (mm)

Fuel reactor height (mm)

Kind and Thickness of insulation

Table 5 Design details of the gasifier

Run 1 Run 2 Run 3 Average

Type of test

Ambient condition

Temperature (0C)

Fuel Weight

Initial, kg

Final, kg

Time operated

Started

Finished

Volume of water

Initial (liters)

Final (liters)

Water temperature

Initial (0C)

Final (0C)

Boiling time (min)

Summering time (min)

38

39