1.0 Introduction
Biodiesel is produced from biological source such as vegetable oils, animal fats and waste cooking oils using biochemical process known as transesterification. It is the mono alkyl esters of fatty acid (MAEFA) gotten when any of the biological source react chemically with an alcohol to produce fatty acid alkyl esters and glycerol. If waste groundnut oil reacts with an alkanol (methanol), biodiesel and glycerol are produced as end products (Jonvan. 2005). Due to the higher demanding of energy and pollution problems by the use of fossil fuel, as a result, it become necessary to develop an alternative fuel which is a renewable energy source that is non-toxic fuel, biodegradable and environmentally friendly fuel used in diesel engine.
Biodiesel does not contain any sulphur or aromatic compound and its combustion results in lower emission of carbon monoxides, hydrocarbons and particulates, which reduces greenhouse gas effect and does not contributes to global warming due to lesser emission (Sharama and Singh, 2009; Suppalakpanya et al., 2010). Biodiesel can be used easily and safely stored as a fuel in addition to its when compared to fossil fuel which affects the environment negatively (Ozcimen and Yucel, 2010).
No fuel system modification or engine conversion is needed to run the biodiesel on conventional diesel engines, biodiesel as an alternative fuel developed to reduce the challenges of environmental and higher demanding of fossil fuel, it became recognizable and attracted more attentions because of it renewable nature and it performance efficiency in diesel engines; biodiesel can be used as pure or mix with diesel fuel in unmodified diesel engines and it reduces some exhaust pollutants which are emitted to atmosphere as compared with fossil fuel exhaust emissions (Agarwal and Das, 2001). Biodiesel has a relatively high flash point (15 OC) which makes it less volatile and safer to transport or handle than petroleum based diesel (Krawczyk, 1996).
It provides lubricating properties that can reduce engine wear and extend engine life (Von Wedel, 1999) in brief, these merits of biodiesel makes it a good alternative to petroleum based fuel and led to its use in many countries, especially in environmentally sensitive area (Roseman, 2009). Biodiesel is a very modern and technological area for researchers due to the relevance that it is wining every day because of the increase in the petroleum price and environmental advantages, it describes sustainable feedstock options for production and improved conversion technologies (Siti, 2009).
The advantages of biodiesel as diesel fuel are it portability, higher combustion efficiency, availability, renewability, higher cetane number, lower sulphur and aromatic content and higher biodegradability (Siti, 2009). The main disadvantage of biodiesel as diesel fuel are its higher viscosity, lower energy content, higher cloud point and pour point, higher nitrogen oxide emission, lower engine speed and power, injector caking in engine compatibility and higher engine wear (Mustafa and Havva, 2010).
The rate consumption of fossil fuel which is faster than it can be replenished and their environmental pollution effect lead to the usage of an alternative renewable energy source in the recent years, biodiesel is an important renewable energy source that has being commonly produced presently in many countries of the world such as Germany, France, USA, Italy, Australia, Brazil, Argentina and Malaysia. With Germany and France as the two leading biodiesel producers in European countries (European Biodiesel Board, 2010) 1.9 million tone biodiesel were produced in European Union countries in 2009. Biodiesel is generally produced from different sources such as plant oils: Soybean oil (Silva et al., 2010, Cao et al., 2005, Lee et al., 2009) cottonseed oil (Dube et al., 2007; Issariyakul et al., 2008) sunflower oil (Madras et al., 2004) linseed oil (Veljkovic et al., 2006) palm oil (Melero et al., 2009) recycled cooking oils (Rahamanlar, 2010; Zhang et al., 2003; Demirbas, 2009) and animal fats.
Transesterification reaction process is one of the method used in biodiesel production. This process is conventional and most common method as a homogeneous catalyst (alkali or acid) or heterogeneous catalyst (Ozcimen and Yucel, 2010). In transeterification process fatty acid alkyl esters are produced by the reaction of triglyceride with an alcohol (ethanol or methanol) in the present of alkali, acid or enzyme catalyst (Ozcimen and Yucel, 2010). The sodium or potassium hydroxide which dissolved in alcohol, is generally used as catalyst in this is process ( Dubo et al., 2007) the product of the reaction are fatty acid methyl esters (FAME) which is the bioldiesel and glycerol (Vicente et al., 2004).
Ethanol can be used as alcohol instead of methanol if ethanol is used fatty acid ethyl ester (FAEE) is produced as product. The alkali catalysed transesterification reaction proceeds faster than acid catalysed transesterification and it is the one most commonly used commercially (Ozcimen and Yucel, 2010). The most commonly alkali catalyst used are NaOH, CH3ONa and KOH, the sodium hydroxide and potassium hydroxide. Alkyl oxides solutions of sodium methoxide or potassium methoxide in methanol which are now commercially available are preferred catalyst for large continous flow production processes (Singh et al., 2006).
Energy analysis is a method of evaluating the energy requirement in either a physical or chemical process operation. It involves carrying out energy balance of a system in which energy requirement is determined in every process unit (Dincer and Rosen, 2007). This analysis is based on first law of thermodynamics that helps in evaluating the efficiencies of the energy and aids the analysis of processes, system and devices for energy transfer and transformation to take place with no information on the degradation of energy resources and can not estimates the quality of energy stream flowing through the system (Dincer and Rosen, 2007).
Exergy analysis is a potential tool based on the second law of thermodynamic which highlights related possibilities and understanding means of identifying, assessing and comparing of processes and systems (Dincer and Rosen, 2007). Exergy is the most reliable tool of assessing the performance of thermodynamic resources, it is the maximum amount of useful work which can be produced by a flow of matter or energy as it comes to equilibrium with a reference environment (Dincer and Rosen, 2000).
This analysis identifies the primary sources of loss and provides more accurate performance relative to theoretical ideal (Dincer and Rosen, 2007). The true measure of how closely actual performance approaches the ideal are gotten from the efficiencies produced by exergy analysis and identified more better than the energy analysis the cause and locations of thermodynamic losses (Dincer and Rosen, 2007). However exergy analysis help in improving and optimizing system designs and processes (Dincer and Rosen, 2007). Exergy analysis has been used in the design, simulation, evaluation of energy performance of a system, it is also employed to detect and evaluate quantitatively the cause of thermodynamic irreversibilities in a system under the consideration (Dincer and Rosen, 2007).
This analysis indicates improvement possibilities of thermodynamic system and overcomes the limitation of the first law of thermodynamic; it also can quantify the quality of heat in a waste stream, (Dincer and Rosen 2007). The purpose of exergy analysis is to identify exergy efficiency, cause and true magnitudes if exergy losses. At steady state of a system, the evaluation of exergy for ethylene process and refrigeration system was conducted at three different ways such as the unit operation level, the subsystem and overall process (Hsuan, 2007)
Economic Analysis has long been considered as one of the most important element in production valuation, feasibility studies and production corporate decision in industries; and in establishing plant and equipment capacities of biodiesei production (Yii-Der et al., 2007). The cost estimation relationship in economic analysis are used to streamline the cost and span associated with proposal preparation, evaluation and agreement (Yii-Der et al., 2007). In biodiesel production process, so many factors are put into consideration for a successful analysis such as availability of raw materials (Feed stocks) capital, labour, site location, good network, roads for transportation purpose and availability of energy to power the production plant, for large scale production of biodiesel to be favourable, the economic analysis must be made the key deriving force which also determine reliability of biodiesel as an alternative fuel to petroleum based fuel, (Yii-Der et al., 2007).
In producing biodiesel, the economic aspect are considered important as the feedstock are readily available in order to make biodiesel profitable (Peter, et al., 2010).But it became obovious that the biodiesel which is more friendly to environment and diesel engines are more expensive than petrol based fuel as a result of insufficient feedstock which causes lower rate of production (Peter et al., 2010). A thermo-economic analysis is simply used to determine the flow of exergy and its associated economic values during operation (Mei and Göran, 1997). The price changes from inflows and outflows of the operating units of system, but the average price can be determined only if there is significant change of inflows and outflows of the operating units ((Mei. and Göran, 1997).. This analysis enhance the comparison of the economic cost of the exergy losses of the process units of concerns, but it dose not account for efficiency of a system or the effect of one part of the system to another part of the system (Mei and Göran, 1997).
Exergoeconomic analysis is a method of combining exergy and economic analysis, this method is a tool used in evaluating the cost of inefficiencies of individual process stream in production of biodiesel, including the intermediate and final product (Hsuan, 2007). The exergoeconomic analysis was reviewed by Tsatsaronis. (1993). Systematic methodology for the evaluation of cost associated with the stream exergy developed by Valero et al. (2010). It has been mostly reported that exergoeconomic method of analysis have been applied for analysis of energy conversion system such as power plant and cogeneration system with few application on chemical processes, the exergoeconomic analysis was for a typical ethylene process (Hsuan, 2007).
Exergy based economic method such as exergoeconomic, thermoeconomic, exergy based pricing, EXCEM analysis, analysis based on the ratio of thermodynamic loss to capital cost and the relationship between exergy and economic was reviewed by Rosen (2010). The eco-efficient biodiesel production process from waste vegetable oils using alkali catalysed transesterification process was designed by Sergio et al. (2010).
Wilmer et al. (2010) worked on exergy analysis of biodiesel production from palm oil. Economic comparison of the four continuous processes using acid and alkali catalysts in fresh vegetable oils (FVOs) and waste vegetable oils (WVOs) was carried out by (Zhang et al., 2003). It is evident that previous works have not investigated the efficiency of biodiesel production from groundnut oil from thermo-economic and exergetic point of view.However, this research work will focus on exergetic and economic analysis of biodiesel production from both fresh and waste groundnut oil using alkali catalysed transesterification process in order to know which production process is more efficient from exergetic and economic point of view.
1.1 Problem Statement
Several types of transesterification method of biodiesel production and process technology have been used to produce biodiesel either at laboratory or commercial scale by different researchers. Also there were several attempts to select biodiesel process route based on economic consideration.
In adequate investigation of biodiesel production process from thermo-economic point of view to establish the most efficient process route to produce biodiesel at commercial scale constitute the problem of this research.
1.2 Aim and Objectives of the Study
The aim of this research work is to use exergetic-economic analysis as a tool to select the most efficient process configuration for biodiesel production from groundnut oil using alkali based catalysed transesterification process.
The aim of this research can be achieved by the following objectives:
- Identification and selection of process configuration for commercial production of biodiesel.
- Simulation of selected biodiesel production process configurations for data generation.
- Energy and exergy analysis of the selected process configurations.
- Economic analysis of the selected process configurations.
- Comparison to select the best process configuration.
1.3 Scope of Study
This research work will involve the use of Aspen Hysys plant software package for simulation of biodiesel production from virgin and waste groundnut oil using alkali based catalyst with energy, exergy and economy analysis of the production process, the following are the scope of this research work:
- Fresh and waste groundnut oils were considered for the analysis.
- Aspen Hysys plant software version 8.0 was selected for this simulation process
- Exergy and economic analysis were the selected basis for comparison.
Basis:
- Feed specification: 50 250 tonne/year for both FGO and WGO.
- Product specification: 99.6 % purity of biodiesel from FGO and WGO.
1.4 Justification of Study
This research work will be justified as followed:
- To provide understanding of inefficiencies of biodesel production configuration and how it can be improved.
- To evaluate data and information generated for biodiesel production process in order to be used for the development of pilot plant.
- To prove the capability of exergy- economic analysis as a tool for the selection of efficient process route.
- To provide means of reducing the cost of biodiesel production.
- To provide means of environmental protection
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