ABSTRACT
The improvement of the combustion properties of coal and biomass by blending and carbonization was investigated. Proximate and ultimate analysis of coal, sawdust, corn cob and their blends were carried out using ASTM methods. The proximate and ultimate analyses were repeated on the five blends after carbonization at 500oC for one hour. Ten mixtures of coal-sawdust and coal-corn cob blends were made into briquettes using starch binder. The calorific values of the samples were determined using a bomb calorimeter, while the thermal efficiency of the briquettes was obtained using the water boiling test analysis. Pollution potential of the fuel samples were derived using a hypothetical power plant simulation. The quantity of CO2, NO2 and SO2 that would be emitted per hour in a 20MW power plant were calculated. The result of the proximate analysis of the raw samples (coal, sawdust and corn cob) showed that coal had the highest fixed carbon (42.38%) and the lowest moisture content (4.28%). Sawdust had the lowest fixed carbon (12.35%) while corn cob had a fixed carbon content of 15.65%. The results obtained showed considerable correlation between the uncarbonized coal-sawdust and coal-corn cob blends. The carbonized blends of both the coal-sawdust and coal-corn cob blends showed an improved fixed carbon content and volatile matter, relative to the uncarbonized. The calorific values and other fuel properties were of similar trends. The results of the ultimate analysis for coal were 70.04% carbon, 5.32% hydrogen, 2.03% nitrogen and 1.02% sulphur. Corn cob had 48% carbon, 5.79% hydrogen and 0.89% nitrogen while sawdust had 48.78% carbon, 5.79% hydrogen and 0.89% nitrogen. Corn cob and sawdust had no sulphur content, while the uncarbonized coal-sawdust and coal-corn cob blends showed decreasing carbon content. This study revealed that the fuel properties of coal and biomass can be improved by blending and carbonization. The simulated power plant analysis of the fuel showed that blending of coal with biomass reduced the SO2 and NO2 emissions to an extent. For NO2, the value of coal-sawdust blends ranged from 82.8-190.8 kg/hr, reduced from 198 kg/hr in coal, while the SO2 content was reduced from 60.5 kg/hr in coal to 5.6 – 50.4 kg/hr in different blends. Therefore, blending of coal with either sawdust or corn cob should be encouraged in coal fired power plants to reduce environmental pollution.
CHAPTER ONE
INTRODUCTION
1.1General
Introduction
History
has revealed that many centuries ago,man made use of energy in its natural form
to aid daily living. From burning wood for cooking, to utilizing the force of
flowing water for irrigation and using sun light to dry and preserve foods. The
use of energy has remained unabated till date, only that energy use has changed
from the brute and basic methods, into more sophisticated and industrial ways.
The
period from the late 1700s into early 1800s in England and Western Europe have
been called the Industrial Revolution. The dawn of the Industrial Revolution
paved way for an age of energy. This period witnessed drastic changes in
virtually every aspect of human life. It was an advent of machines and use of
mechanized methods. Ever since, man’s desire to live a better and civilized
life, with the help of modern technology has caused a great demand for energy
in its many forms. This also came with the adoption of lifestyles that has an
increased demand for energy use.The technological advances that occurred during
the industrial revolution of the 1700s have numerously been credited to coal.
Before this period, wood was the major source of energy.
Consequently, the increasing adoption of a lifestyle that was energy intensive came with the quest for a better energy resource. Today, these energy needs are majorly supplied by fossil fuels such as coal, natural gas and petroleum. These fuels are known as primary energy sources, and they provide most of the energy that powers man’s modern life. Petroleum was discovered by Edwin Drake in 1859 in the United States. It was first used for lightening lamps and other basic uses. With the breakthrough of petroleum refining into various fractions, and increased use of internal combustion engines in automobiles, motor cycles and aero planes, the demand for petroleum never dwindled. In 1992, the National Energy Strategy in the United States concluded that, “for the foreseeable future, oil [Petroleum] will remain a critical fuel for the United States and all other industrialized nations.” The quest for oil has continued up to the point that it has become a potential economic and security concern for developed countries, especially after the 1970s crisis. Despite these, coal has not been totally abandoned. It is used for electricity generation in countries with large coal reserves, with no cheaper alternative. For example, 73% of South Africa’s primary energy is derived from coal1. In China’s energy strategy, coal plays the most important role especially for its electricity sector2.
The availability of energy resources and its effective utilization has a bearing on national development and living standards. Energy is required for national development, and its presence directly betters the standard of living. The availability of vast amounts of energy resources in a nation is supposed to bring significant progress to the economy, and living standards of her citizenry. The effect of energy can be seen in its ability to multiply the work of a few labourers by many folds e.g an automobile would move many folds faster than man. The value of energy is noticed when its utilization results in a final product. Good management practices should aim at reducing the rate of exhaustion of the resource base, rather than increase or even sustain the rate of consumption3.Consumers and manufacturers, who enjoy the efficient use of energy, should become more knowledgeable about it.
EVALUATION OF THE FUEL PROPERTIES AND THERMAL EFFICIENCY OF SUB-BITUMINOUS COAL-BIOMASS BLENDS
