CHARACTERIZATION OF MAIGANGA AND OKABA COAL BLEND FOR
SOLID FUEL COMBUSTION
Department:
Engineering – Chemical Engineering
CHAPTER ONE
1.0 BACK GROUND
OF STUDY
1.1 INTRODUCTION
Power generation in
any country is very essential to its economic growth, Nigeria generates about
4,000 megawatts(MW) of electricity (Ediri, 2014), but this is deficient as the
country still faces the challenge of epileptic power supply, it is expected
that power generation reaches 40,000 megawatts(MW) in the year 2020 (Ediri,
2014), to achieve this feat the government has planned the construction of various
power generating stations of which coal would be a vital raw material used in
some of these plants, although generation of energy from coal is accompanied by
the emission of greenhouse gases, the development of clean coal technologies
have helped to reduce this emissions.Coal which is a product of long periods of
accumulation and subsequent physical and chemical alteration of plant material
is an organic rock (as opposed to most other rocks in the earth’s crust, such
as clays and sandstone, which are inorganic; it contains mostly carbon (C), but
it also has hydrogen (H), oxygen (O), sulfur (S) and nitrogen (N), as well as
some inorganic constituents (minerals) and water (H2O).
(Radovic, 2009) Different types of coals are classified based on their composition
of these constituent elements, based on this coal is classified as lignite,
subbituminous, bituminous and anthracite. the combustion of coal under
specified conditions leaves behind a residue known as ―ash‖ which is composed
mainly of oxides and sulphate depending on the source of the coal sample.
(Folahan , 2012).
The combustion of
coal produces sulphur and some other gases and a solid residue known as coal
ash or fly ash. Fly ash is either deposited as dry or hydraulic ash, the
sulphur content of coal varies considerably with the nature and origin of the
fossil deposits (Folahan , 2012) the utilization of coals for both energy
production and various coal conversion processes is limited by the presence of
sulphur in the coal, sourcing for the right type of coal and inconsistency in
composition. Many of these plants will not be able to source for coal that meet
up to their specification and will have to combine samples available to them to
obtain the required quality of coal. The high sulphur dioxide emissions caused
by the utilization of coals as a major fossil fuel leads to worldwide
environmental problems. When coal is burnt its sulphur content combines with
oxygen to form sulphur dioxide (SO2), which contributes
to both pollution and acid rain. Acid rain resulting from SO2 has a harmful effect on agriculture and destroys the ecological
balance. Also naturally occurring elements in the environment become part of
the coal structure through the coalification process. The use of large quantity
of coal results in significant emissions of these trace elements, although
these trace elements are present in small amounts in the coal. Another serious
problem of sulphur in coalis the formation of clinker in furnaces. The causes
of clinker formation are low quality coal having low gross calorific value,
more ash content, high mineral content, low fusion temperature of ash below
1500 C, and over-firing of the molten slag.
The presence of
sulphur in coal also reduces the quality of metallurgical coal (Folahan ,
2012). Blending of coals results in a combination of characteristics from each
of the
individual coals in
the blend. Some coal characteristics, such as ash, sulphur and
moisture content,
are additive and can be calculated from the proportions of
the different coals
in the blend, it is therefore necessary to know the characteristics of the
individual samples and that of the final blend before it is used in any power
plant, this will enable a plant to understand the advantage and problems
related to each blend of coal. The work done involves the chemical
andthermo-gravimetric analysis of maiganga and okaba coal blend.
1.2 Problem
Statement
The heat content in
a fluidized bed or furnace of a power plant may be reduced greatly due to the
presence of slags or foul formed as a result of the deposition of some
constituent compounds in coal such as sulphur, alkalis and some trace metals,
it is therefore important to find solutions to the usage of low quality coal by
blending them with another sample that complement for the lacking quality.
1.3 Scope
To blend two coal
samples and perform physical, chemical and thermal analysis on the blend
obtained.
1.4 Aim and
Objectives
The aim of this
research is to blend and characterizes coal obtained from two coal mines in
Nigeria. This aim will be achieved through the following objectives;
i. Performing TGA on individual samples.
ii. Blending of the samples.
iii. Performing TGA on the final blend.
iv. Proximate and ultimate analysis of the coal blend.
v. FT-IR analysis of the samples.
vi. SEM analysis of
the sample.
1.5 Justification
ü Coal is one of the leading natural sources available for power
generation and will remain relevant even in the near future.
ü
Although CO2is produced as the major combustion product of coal, development and
demonstration of new clean coal technologies has formed areas of research over
the years, research has also being ongoing on coal ash reduction,
desulphurization and coal briquette technology.
ü Nigeria has a large deposit of coal which is underutilized for power
generation.
ü Nigeria needs alternative sources of power generation apart from
hydroelectric power generation which depends on seasons.