Description
ABSTRACT
Anaerobic digestion is a biological process in which the organic material is converted by microorganisms to methane and carbon dioxide (biogas) in the absence of oxygen. This process is interesting but the control on industrial scale spontaneous biological reactions requires good knowledge of the phenomena involved. The search for appropriate models to be use in control theory is now a high priority to optimize fermentation processes and solve important problems, such as the development of renewable energy from biodegradable organic waste. The aim of this study is modeling of biokinetics of anaerobic digestion on several aspects such as microbial activity, substrate degradation and methane production. For this, we developed a mathematical model based on mass balances on biomass, the organic substrate and biogas. This model is then simulated on Matlab using the experimental data from the literature and comparison between other models and our experimental results. The sensitivity of the model to the process parameters was study by varying the initial concentration of the biomass and the dose of the organic substrate.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
CHAPTER ONE
- INTRODUCTION
- BACKGROUND OF THE STUDY
- AIM AND OBJECTIVE OF THE STUDY
- SCOPE OF THE PROJECT
- PURPOSE OF THE STUDY
- SIGNIFICANCE OF THE STUDY
CHAPTER TWO
LITERATURE REVIEW
- REVIEW OF THE STUDY
- BACKGROUND REVIEW OF ANAEROBIC DIGESTION
- PROCESS KEY FACTORS OF ANAEROBIC DIGESTION
- OVERVIEW OF BIOGAS
- DESCRIPTION OF DIGESTER
- TYPES OF SMALL-SCALE DIGESTERS
- REVIEW OF RELATED STUDY
- OVERVIEW OF THE STUDY AREA
CHAPTER THREE
METHODOLOGY
3.1 DEVELOPMENT MODEL
3.2 MATHEMATICAL MODEL
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
CHAPTER FIVE
- CONCLUSION
REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
According to Bastin et al (2011), an anaerobic digestion is a natural process where biodegradable material (biomass) is transformed by microorganisms to biogas in the absence of oxygen. The search for appropriate models to be use in control theory is now a major priority for optimizing the fermentation process and solve important problems, such as renewable energy development from biodegradable organic waste. Microbiological, biochemical and technological point of view, anaerobic digestion is generally composed of four major stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. During this stage, microorganisms convert the hydrogen and acetic acid to methane gas and carbon dioxide (Benyahia et al., 2012). The bacteria responsible for this conversion are call methanogens and are strict anaerobes. Several mathematical models associated with these phenomena are present in the literature but are often very complex and not suitable for control (Simeonov et al., 2013).
The modeling of a bioprocess is a virtual representation of biological, physical and chemical processes taking place in the digester. From this and a numerical calculation software, it is possible to simulate, quickly and cheaply, different treatments scenarios taking into account and evaluating the impact of input variations (quantities and qualities) and operation. Models can be classify according to their mode of conception: (i) the “black-box” models if the process is too complex (Hess et al., 2015). However, the modeling of biochemical processes remains difficult because there is no biological laws or universal models; unlike physics, where known and validated models for centuries (Principles of thermodynamics, ideal gas laws etc.) can be the basis for the construction of mechanistic models. Bacterial growth models are essentially empirical. In this context, we have established a biokinetic model based on mass balances on the substrate, biomass and methane production in order to predict the observed behavior of anaerobic digestion and better understand the internal phenomena that occur within digester. The model is simulate on Matlab software introducing experimental parameters of the literature.
1.2 AIM AND OBJECTIVES OF THE STUDY
The aim of this study is modeling of biokinetics of anaerobic digester for biogas production in reconstruction of the Apiastsi Community. The objectives are:
- To model an anaerobic digester using Matlab software
- To understand the construction requirement for different types of biogas digester
- To increase the biogas yields
1.3 SCOPE OF THE STUDY
The scope of this work covers the modeling an anaerobic digester using Matlab software. In this work, different types of biogas digester types were discussed and a description of the anaerobic process that takes place in biogas plants is presented. Also, the operational conditions and the available technologies—including their advantages and disadvantages—are thoroughly discussed. Specifically, parameters defining the reactor’s design, the operational conditions, and the monitoring procedures are summarized and discussed.
1.4 PURPOSE OF THE STUDY
The main purpose of this study is to model an anaerobic digester and to become familiar with different types of biogas digester and digester operating parameter thereby reducing the costs of the process, increasing the biogas yields.
1.5 SIGNIFICANCE OF THE STUDY
This study will serve as a means of becoming familiar with substrate, biomass and methane production in order to predict the observed behavior of anaerobic digestion and better understand the internal phenomena that occur within digester.
1.6 PROJECT ORGANISATION
The work is organized as follows: chapter one discuss the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the modeling methods applied, chapter four discusses the results and discussion of the work, chapter five summarizes the research outcomes.
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