Description
ABSTRACT
Biomass is a promising sustainable and renewable energy source, due to its high diversity of sources, and as it is profusely obtainable everywhere in the world. It is the third most important fuel source used to generate electricity and for thermal applications, as 50% of the global population depends on biomass. The increase in availability and technological developments of recent years allow the use of biomass as a renewable energy source with low levels of emissions and environmental impacts. Biomass energy can be in the forms of biogas, bio-liquid, and bio-solid fuels. It can be used to replace fossil fuels in the power and transportation sectors. In this work we investigate the potential for producing liquid fuel (diesel) from shredded PWS in a custom-made pyrolytic equipment using a ternary mixture of Al2O3-SiO2-Fe2O3 (generated locally) as catalyst. Samples of PWS sourced locally from the Imo State University were dried in air and shredded into small pieces using a pair of scissors. The shredded pieces were fed into a reactor that also served as catalytic cracking chamber. Varying amounts of the catalyst were added to the shredded mass followed by heating to temperatures ranging from 300-500 °C after which the resulting gaseous hydrocarbon mixture was condensed into liquid in a measuring cylinder that serves as a condenser. Physical properties like colour, density and flashpoint of samples of the liquid produced were determined and compared to conventional liquid fuels. It was observed that limited amount of liquid was generated in the absence of the catalyst; the amount of liquid produced showed a dramatic increase in the presence of the catalyst and it increased progressively with the amount of catalyst loaded into the cracking chamber. At temperatures below 350 °C in the catalytic chamber the condensed liquid turned waxy over time, suggesting poor catalytic cracking of long chain hydrocarbons. The waxy appearance disappeared when temperatures in the catalytic chamber exceeded 350 °C. Whilst the colour appeared closer to the colour of diesel, the density and flashpoint appeared in range that corresponded to those of diesel and kerosene. We conclude that liquid fuel production is a potential route for diverting end-of-life plastics from landfill sites.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
- AIM OF THE STUDY
- OBJECTIVE OF THE STUDY
- SCOPE OF THE STUDY
- SIGNIFICANCE OF THE STUDY
- PROJECT ORGANISATION
CHAPTER TWO
LITERATURE REVIEW
- REVIEW OF BIOMASS PYROLYSIS
- MECHANISM OF PYROLYSIS PROCESS
- SOURCES OF BIOMASS AND THEIR PROPERTIES
- REVIEW OF PYROLYSIS TECHNOLOGY
- THE PRODUCTS OF PYROLYSIS PROCESS
- REACTORS EMPLOYED IN THE PYROLYSIS PROCESS
- PYROLYSIS OPERATING PARAMETERS
CHAPTER THREE
- MATERIALS AND METHODS
- MATERIALS
- METHODS
- CATALYTIC PYROLYSIS
- DETERMINATION OF SOME PROPERTIES OF OILS PRODUCED
CHAPTER FOUR
- RESULT AND DISCUSSION
- CHARACTERISATION OF MATERIALS
- RESULTS OF THERMAL DEGRADATION (NON- CATALYTIC PYROLYSIS)
- RESULTS OF CATALYTIC PYROLYSIS
- PRODUCT YIELD ANALYSIS
CHAPTER FIVE
- CONCLUSION
- RECOMMENDATION
- REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
Only a small fraction of end-of-life ‘pure’ water sachets (PWS) is currently recycled in Nigeria, with the rest being illegally discarded or inappropriately landfilled. Pure water sachets are currently one of the most difficult plastics to deal with by various Metropolitan, Municipal and District assemblies in Nigeria. Large volumes of this waste material are created daily, with practically no avenues of recycling or treating them. Owing to their low densities they occupy large landfill space and are generally not biodegradable. Attempts made by various district, municipal and metropolitan authorities to contain the surge and menace caused by this category of the waste stream have failed to yield the desired effects, culminating in calls by a section of civil society and Government for a ban on plastics materials. However, a ban will compound the already precarious unemployment situation in the country as several thousands of vendors could potentially be thrown onto the streets. Pure water sachets are produced from the thermoplastic polymer high density polyethylene (HDPE). Globally, production of plastics has seen an increase from around 1.3 million tonnes in 1950 to 245 million tonnes in 2006 at an annual growth rate of around 10%, [1]. From the point of view of individual plastics, polyolefins account for 53% of the total consumption [3] Polyethylene constitutes about one- third of the global consumption of plastics with an estimated annual growth rate of around 4.4% up to 2020 (Panda et al., 2010).
In an attempt to address the plastics waste menace, several measures are currently in place or have been proposed, among which are mechanical recycling, landfilling, incineration and lately the call for the adoption of biodegradable plastics [3,4]
Of all the measures enumerated above, the proposed adoption of biodegradable polymers appear to be the most popular based on the belief that biodegradable polymers can be converted back to biomass in a realistic time period. However, there are a number of difficulties over the use of degradable plastics [5,6]. First, appropriate conditions (such as presence of light for the photodegradable plastics) are necessary for the degradation of such plastics. Second, greenhouse gases such as methane are released when plastics degrade anaerobically. Based on the current reckless ‘throw away culture’ of most vendors of pure water sachets, the use of biodegradable plastics may not achieve the desired results.
A chemical method for recycling waste polymers that is currently gaining the attention of researchers is cracking, made up of thermal or catalytic cracking. The process of cracking breaks down long polymeric chains into smaller but useful molecular weight compounds that can be utilised as fuels or chemicals in various applications. The pyrolysis reaction can be carried out in the presence of a catalyst (catalytic cracking) or absence of a catalyst (thermal cracking or thermolysis). Various researchers have investigated the conversion of various forms of waste plastics into liquid fuels [5].
Although waste pure water sachets are manufactured from HDPE, its utilisation in the production of liquid fuels has not been documented as a potential route to waste plastics recycling. Accordingly, in this investigation, we report preliminary results on the production of liquid fuels from power water sachets using a simple catalyst generated from a ternary Al2O3-SiO2-Fe2O3 system.
1.1 BACKGROUND OF THE STUDY
Nowadays, energy usage is prodigious, and a significant key factor for the advancement of a nation, and the scarcity of energy has become an economic threat for the development of nations around the world [1,2]. It is said that ‘‘Energy is a critical component of our lives. Without energy, we can’t even dream of economic growth. But despite its central role, not everyone has access to modern energy services’’ [3,4]. Today’s energy requirement is increasing in trend, due to population growth and ongoing economic and technological advancement around the world [4]. Currently, fossil fuels are the main source of energy because of their high calorific values, good anti-knocking properties, and high heating values; meanwhile, reserves are limited. Therefore, the development of alternative energy resources can lower the depletion of fossil fuel by reducing their consumption [5,6,7]. On the other hand, the world’s heating condition is increasing every day. The atmospheric CO2 level has crossed the risky level that was forecast to happen in another 10 years [8]. Furthermore, the depletion of fossil fuels and extreme change of climate have driven the search for alternative energies and renewable energy sources that can meet the world’s energy demand, reduce greenhouse gas emissions, curb pollution, and maintain the planet’s temperature at a stable level [9,10,11].
Among the alternative energy sources, biomass can become a promising sustainable energy source, due to its high diversity and availability [12]. Biomass can be defined as all biodegradable organic material derived from animals, plants, or microorganisms. This definition also includes products, by-products, waste originating in agricultural activities, as well as non-fossil organic waste produced by industrial and municipal waste [13]. Biomass can be considered as a blend of organic resources and minor amounts of minerals, which also contains carbon, oxygen, hydrogen, nitrogen, sulphur, and chlorine [18].
Different types of energy can be produced through the thermal conversion of biomass, such as combustion, pyrolysis, gasification, fermentation, and anaerobic decomposition. Combustion is a thermochemical process used for the production of heat, which consists of a chemical reaction in which a fuel is oxidised, and a large amount of energy is released in the form of heat (exothermic reaction). Pyrolysis is a thermal decomposition process which takes place in the absence of oxygen [19,20]. In combustion and gasification processes, the first step is pyrolysis, followed by total or partial oxidation of primary products. Gasification is the process of generating electricity by applying heat to organic material in the presence of less oxygen. In the fermentation process, organic materials are used to produce alcohol, with the help of yeast, to generate power in automobiles. Anaerobic decomposition is the process of producing biogas, and generates electricity.
Among all the conversion techniques of biomass conversion, the pyrolysis process offers a number of benefits, including less emissions and that all the by-products can be reused. In addition, during the process, pyrolysis produces solid or carbonised products, liquid products (bio-oils, tars, and water) and a gas mixture composed mainly of CO2, CO, H2, and CH4 [21,22,23]. The oil resulting from the pyrolysis of biomass, usually referred to as bio-oil, is a renewable liquid fuel, which is the main advantage over petroleum products. It can be used for the production of various chemical substances [24]. The pyrolysis process has three stages: the dosing and feeding of the raw material, the transformation of the organic mass and, finally, the obtaining and separation of the products (coke, bio-oil, and gas). The factors that influence the distribution of the products are the heating rate, final temperature, composition of the raw material, and pressure [25].
The pyrolysis process has great market potential; in this process, biomass is used as raw material in order to produce energy. Therefore, intense research is taking place around the world to improve this method of energy production. Among the technologies, such as digestion, fermentation, and mechanical conversion, thermo-conversion for producing energy from biomass is relatively newer from a commercial perspective, and gaining more attention because of its technical and strategical advantages. In addition, the production of waste is constantly increasing, and the economic activity linked to it is becoming increasingly important. The elimination or attenuation of environmental problems and obtaining profitability in the process of managing them is a very favourable step. Therefore, pyrolysis could be an alternative means of energy recovery, obtaining different fractions that are also recoverable not only from the energy point of view.
Though the research into pyrolysis technology indicated that pyrolysis is a more promising option to the sustainable development, pyrolysis technology still needs further improvement, and several challenges need to be tackled to gain its full potential benefits. Furthermore, several types of research have been carried out recently, focusing on the use of pyrolysis technology, but only a few papers have been analysed and reviewed by the researchers. Thus, the main aims of this study are to present a brief review of the development of pyrolysis technology, including their present status and future challenges, to provide information to the researchers who are interested in pyrolysis technology. A number of studies from highly rated journals in scientific indexes are reviewed, including the most recent publications.
1.3 AIM / OBJECTIVES OF THE STUDY
The main aim of this work is to produce high-value bio-oil from the pyrolysis biomass of pure water sachet waste.
1.4 SIGNIFICANCE OF THE STUDY
Pyrolysis technology has the capability to produce bio-fuel with high fuel-to-feed ratios. Therefore, pyrolysis has been receiving more attention as an efficient method in converting biomass into bio-fuel during recent decades [17]. The ultimate goal of this technology is to produce high-value bio-oil for competing with and eventually replacing non-renewable fossil fuels. However, the development of advanced technologies is the next challenge for pyrolysis researchers to achieve this target. It is necessary to convert biomass into liquid fuels for direct use in vehicles, trains, ships and aeroplanes to replace petrol and diesel [18–20].
1.5 SCOPE OF THE STUDY
There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient conversion method compared to other thermo-chemical conversion technologies. However, this technology is not yet fully developed with respect to its commercial applications. In this study, more than two hundred publications are reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production. Aspects of pyrolysis technology such as pyrolysis principles, biomass sources and characteristics, types of pyrolysis, pyrolysis reactor design, pyrolysis products and their characteristics and economics of bio-fuel production are presented. It is found from this study that conversion of biomass to bio-fuel has to overcome challenges such as understanding the trade-off between the size of the pyrolysis plant and feedstock, improvement of the reliability of pyrolysis reactors and processes to become viable for commercial applications.
1.6 PROJECT ORGANISATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
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