Analytical Study of a Small Scale Biomass Gasifier
Chapter One
Aim and objectives
Aim
The aim of this project is to carry out an analytical study of a small scale biomass gasifier
Objectives
The objectives of this project are as follows:
- To demonstrate the use of alternative sources of energy
- To design a small scale gasifier that employs the use of wood as its fuel
- To carry out an analysis of the gasifier design
CHAPTER TWO
LITERATURE REVIEW
Biomass Gasification: Historical Review
Gasification was discovered independently in both France and England in 1798, and by 1850 the technology had been developed to the point that it was possible to light much of London with manufactured gas or “town gas” from coal (Singer 1958; Kaupp 1984). Manufactured gas soon crossed the Atlantic to the United States and, by 1920, most American towns and cities supplied gas to the residents for cooking and lighting through the local “gasworks.”
Starting about the time of World War I, small gasifiers were developed around charcoal and biomass feedstock to operate vehicles, boats, trains, and small electric generators (Rambush 1923). Between the two world wars, development was pursued mostly by amateur enthusiasts because gasoline was relatively inexpensive and simpler to use than biomass. In 1939 the German blockade halted all oil transport to Europe. Military use of gasoline received top priority, and the civilian populations had to fend for themselves for transport fuels. Approximately one million gasifiers were used to operate vehicles worldwide during the war years. (Egloff 1941, 1943; Gengas 1950; NAS 1983; Kaupp 1984).
At the beginning of World War II, there was a great deal of interest in all forms of alternative fuels (Egloff 1941, 1943). By 1943, 90% of the vehicles in Sweden were powered by gasifiers (Egloff 1943). By the end of the war, there were more than 700,000 wood-gas generators powering trucks, cars, and buses in Europe and probably more than a million worldwide (Egloff1943). However, these impressive numbers included only six wood-fueled vehicles in the United States and two in Canada, where low-cost gasoline continued to be available throughout the war. Soon after the war,low-cost gasoline became available again, and most users went back to burning gasoline because of its convenience.
The history of gasification may be divided into four periods, thus: 1850–1940: During this early stage, the gas produced from coal was utilized mainly in the lighting of homes and streets and for heating. Major commercial gasification technologies such as Winkler’s fluidized-bed gasifier in 1926, Lurgi’s pressurized moving-bed gasifier in 1931, and Koppers-Totzek’s entrained-flow gasifier were invented and grew in prominence during this period. 1940–1975: In the period 1940–1975 a large number of vehicles in Europe operated on coal or biomass gasified in onboard gasifiers. During this period over a million small gasifiers were built primarily for transportation. The end of the Second World War and the availability of abundant oil from the Middle East gradually eliminated the demand for gasification. Figure 2.1 describes such vehicles used in this period.
1975–2000: The third phase in the history of gasification began after the Yom Kippur War, which triggered the 1973 oil embargo. On October 15, 1973, members of the Organization of Arab Petroleum Exporting Countries (OPEC) banned oil exports to the United States and other western countries, which were at that time heavily reliant on oil from the Middle East.
This gave a strong impetus to the development of alternative energy techniques like gasification in order to reduce dependence on imported oil. The subsequent drop in oil price, however, reduced the apparent move for gasification although some governments, realizing the need for a cleaner and friendlier environment, gave support to development of integrated gasification combined cycle (IGCC) power plants. Post-2000: Global warming and political instability in some oil-producing countries added fresh momentum to gasification. The threat of climatic change prompted the need for moving away from carbon-rich fossil fuels. Gasification as a natural choice for conversion of renewable carbon-neutral biomass into gas is being employed.
Energy and power
Energy is usually defined as the capacity to do work.It is viewed a fundamental entity of nature transferred between parts of a system in the production of physical change within the aforementioned system. Energy is power derived from the utilization of physical or chemical resources, especially to provide light and heat and other forms of power to operate machines
Power simply put is the rate at which work is done or energy is consumed.Energy and power can be related in the sense that the more energy transferred in a certain time the greater the power.Different forms of energy exist though broadly classified under kinetic and potential forms of energy; energy could be broken down to various forms as follows;
- Kinetic energy
- Potential energy
- Thermal or heat energy
- Chemical
- Electrical
- Electro chemical
Chapter Three
Design methodology
Design considerations
Economic design considerations
The economic considerations taken into account include:
- a) Machine would be constructed with locally available material to minimize fabrication and maintenance costs.
- b) The ease of fabrication of machine components was considered, bearing in mind flexibility of the design in cases of transportation and disassembly in maintenance times
- c) The overall cost was considered as regards the design, material selection and production phases and priority placed on its minimization.
Technical design considerations
Most of the technical considerations were determined from pre design experimentation so many of which have been established from research and documented. They include;
- Wood physiological factors such as size, shape and moisture content were considered for effective production of product gas.
- Strength, ductility and thermal conductivity were considered in the selection of appropriate materials for the machine components to ensure optimum reliability.
- Ergonomic consideration were also accounted for.
CHAPTER FOUR
RESULTS AND DISCUSSION
Combustion results
Following the modeling and analysis based the relevant design variables, assumptions and hypothetical inputs, 1g of biomass would react with 0.6 g of oxygen
Air requirement for combustion of biomass is 2.6 g of air
Chapter five
Conclusion and recommendations
Conclusion
Results obtained from the biomass gasifier design analysis showed functionality in an eventual developed prototype. The combustion analysis carried out on a 1g of biomass showed that sufficient biogas can be produced by biomass gasification. The thermal simulation analysis of mild steel as gasifier material showed that it is capable ofsupporting the operational requirements of a practicalgasifier. The average production cost of the machine stands at 35,000 which satisfy the assertion of the biomass gasifier being a low cost machine though capable of generating energy that can be utilized in many areas. Nigeria rich in vast wood reserves is a place where investment on biomass gassifier will be highly profitable Biomass gasification would hence go a long way in addressing the energy needs of Nigeria in particular
Recommendations
The current research work was focused on the design analysis and material selection of biomass gasifier which can be put into operation. Further work is recommended to put into consideration wider operating variables to intensively simulate the biomass gasifier. The data collected from this research work and subsequent ones should be a precept and or guide for the practical design and development of a functional biomass gasifier with improved material and biomass selectionfor maximum biogas productivity. Government intervention and funding is highly recommended to promote research works and development of biomass gasifier in Ngeria as this will develop and put into optimum utilization our non renewable energy resources, create employment through direct and indirect investment on biomass gassifer and reduce our dependence on oil.
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