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.

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