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|Title:||Kolza Sap-samanı Isıl Davranımının Termogravimetrik Yöntemle İncelenmesi|
|Other Titles:||Investigation Of Thermal Behaviour Of Straw And Stalk Of Rape Seed Plant Using Thermogravimetric Analysis|
Çift, Bülent D.
|Publisher:||Fen Bilimleri Enstitüsü|
Institute of Science and Technology
|Abstract:||Sosyo-ekonomik kalkınmanın en önemli göstergesi olan enerjinin zamanında, kaliteli, yeterli miktarda ve çevreye zarar vermeden temini ülkemiz kalkınma planlarının ana hedefini oluşturmaktadır. Enerji tüketimi, uygar dünyada kalkınmışlık ölçüsü olarak alınmaktadır. Türkiye birincil enerji kaynaklan açısından kendisine yeterli olmayan ülkeler grubundadır ve ekonomik ve sosyal hayatımız büyük ölçüde ithal enerji ile sürdürülebilmektedir. Ülkemiz nüfusunun hızla artması ve insanların yüksek yaşam standardına ulaşma isteği sonucunda gelecekte enerji problemi ile karşı karşıya kalmamız kaçınılmaz olacaktır. 1973 ve 1977 yıllarında yaşanan enerji krizleri ülkemiz için fosil kökenli ve dışa bağımlı enerji kaynaklarına güvenmemiz gerektiğini göstermiştir. Bu nedenle, enerji tasarrufu ve bunun yanında da yenilenebilir enerji kaynaklarına yatırım yapmamız gerektiği ortaya çıkmaktadır. Yenilenebilir enerji kaynaklarının termokimyasal dönüşümü sonucu elde edilecek ürünler, enerji ihtiyacımızı karşılamak amacıyla gelecekte kullanılacak aday biyoyakıtlar arasında bulunmaktadır. Biyokütleden biyoyakıt eldesinde ilkel madde tanımlaması önemlidir. Bu sebeple kolza sap-samanını ısıl davranımının belirlenmesine çalışılmıştır. Kolza sap-samanı termogravimetrik analizi (TGA) hava ve azot ortamlarında gerçekleştirilmiştir. Diferansiyel termal analiz deneyleri de yine ısıl davranımın tespiti için azot ortamında gerçekleştirilmiştir. Termogravimetrik analiz değerlerinden faydalanarak ısıl bozunma reaksiyonuna ait kinetik değişkenler bulunmuştur. Hava ve azot ortamındaki deneyler 25, 50 ve 100 C/dakika' lık ısıtma hızlarında gerçekleşmiştir. Hava ortamında gerçekleştirilen termogravimetrik analiz deney sonuçları şu şekildedir; artan ısıtma hızı ile birlikte ani ısınma etkisi sonucunda ağırlık değişimleri eğriye daha yüksek sıcaklıklarda yansımaktadır. Bu nedenle ısıtma hızının artması ile ilk bozunma sıcaklıkları artmaktadır. Örneğin 25 C/dakika ısıtma hızında 74 C olan ilk bozunma sıcaklığı 50 C/dakika ısıtma hızında 94 C'a 100 C/dakika ısıtma hızında 100 C'a yükselmiştir. 600 C sonunda kalan ağırlık, artan ısıtma hızı ile birlikte artmaktadır. Azot ortamında gerçekleştirilen termogravimetrik analiz deneylerinde de artan ısıtma hızı ile birlikte ilk bozunma sıcaklığı artmaktadır. Hava ortamında 25, 50 ve 100 C/dakika ısıtma hızlan için bulunan reaksiyon mertebeleri sırasıyla 2.2, 1.6 ve 1.3 'tür. Azot ortamı için aynı ısıtma hızlarında bulunan kinetik değişkenler sırasıyla 3.3, 1.6 ve 1.7' dir|
All organic matter, or biomass, can in one way or another be used as fuel. It is composed mainly of carbohydrate compounds the building blocks of which are the elements carbon, hydrogen and oxygen. All ultimately derive from the process of photosynthesis in alternatives to the conventional fossil fuels are renewable fuels. Renewables cover sources of energy such as solar, wind, hydro, geothermal, wave, tidal and biomass. The economic feasibility of any energy from biomass scheme depends ultimately on the cost of competetive conventional fuels. Apart from this their practical realisation, if technically feasible, will be influenced by the value of the feedstock as determined by the demand for it for other uses. For example some straw may have a higher value as bedding for animals. Some schemes appear to make sense only on a small scale and when integrated with existing activities like farming. Others like the proposed large-scale forest energy plantations will involve major land-use changes with large social and environmental impacts. The use of oil is predominantly a phenomenon of this century and is likely to die out in the next. These fuels upon which our current civilisation is largely based, are non-renewable and the limits to their availability are clearly seen. It is for this reason that so much attention is now being given to the search for alternative and supplementary fuel supplies including biomass, which has the advantage of being renewable. Also even in its large-scale exploitation it is likely to be relatively non-polluting. Turkey, whose energy production depends heavily on import fuels, has to explore the mays of increasing the use of biomass in energy production without destroying its valuable forest resources. One of the most promising options is the utilization of waste streams from forestry, agricultural residues produced in Turkey and 60% of this total can be recovered for energy production. Agricultural residues, with an annual recoverable potential of 30-40 million dry tonnes and a primary energy equivalent of 525-700 PJ, are in important renewable source that can replace all the lignite and coal used in electrical power generation plants in Turkey. This potential is expected to grow with the implementation of new irrigation projects. Turkey's geographic and climatic conditions are suitable for growing energy crops which are another sustainable option for Turkey to improve the environmental quality by providing and alternative to fossil fuels. Sorghum, switchgrass, short rotation woody crops and hybrid poplar are among the high-productivity energy crops. Anature of biomass as a fuel: Advantages and disadvantages. Disadvantages are: IX . Biofuels usually have only a modest thermal content compared with fossil fuels.. They often have a high moisture content, which has the effects of inhibiting ready combustion, causing major energy loss on combustion, mainly as latent heat of steam, and also rendering the material putrifiable so that it can not be readily stored.. They usually have a low density and, in particular, a low bulk density, factors which increase the necessary size of equipment for handling, storage and burning.. The physical form is rarely homogeneous and free flowing, which militates against automatic feeding to combustion plant. Advantageous are;. They constitute a continualley renewable resource whose use leads to no long-term increase in the atmospheric carbondioxide.. They may be cheap and readily available. Energy can be obtained from biomass in three ways: 1) Direct combustion 2) Physical processes 3) Conversion processes All organic materials decompose upon heating. At temperatures above 200°C, biomass (lignocellulosic materials) thermally degrade to produce gases, liquids (tars), and solids (chars) as primary products. Depending on reaction parameters such as heating rate, final temperature, and residence time at temperature, as well as particle size, moisture or ash content, presence or absence of air or oxygen, and so on, these primary can undergo secondary reactions affecting yields and qualities of the final products. In thermal conversion processes of biomass to biofuel to design a reactor and to determine the operation conditions of thermal degradation processes, using thermogravimetric analysis methods is going to be useful. By the way besides physical and chemical properties thermal behaviour of biomass can be indentified and datum for thermal degradation can be obtained. On the other hand from the datum obtained by thermal analysis kinetic parameters of the degradation reactions can be determined. Thermal analysis can be introduced as a brief outline of the history and meaning of the two basic quantities: heat and temperature. Thermometry, calorimetry, termomechanical analysis and diatometry, thermogravimetry and differential thermal analysis are the branches of thermal analysis. Among these branches thermogravimetry and differential thermal analysis are examined in details. Thermogravimetry (TG) is a technique in which the change in sample mass is recorded as a function of temperature. The modes of thermogravimetry may be described: a) isothermal or static thermogravimetry, in which the sample mass is recorded as a function of time at constant temperature; b) quasistatic thermogravimetry, in which the sample is heated to constant mass at each of a series of increasing temperatures, and c) dynamic thermogravimetry, in which the sample is heated in an environment whose temperature is changing in a predetermined manner, preferably at a linear rate. Differential thermal analysis (DTA) is a thermal technique in which the temperature of a sample, compared with the temperature of a thermally inert material, is recorded as a function of the sample, inert material, or furnace temperature as the sample is heated or cooled at a uniform rate. Temperature changes in the sample are due to endotherrnic or exothermic entalpic transitions or reactions such as those caused by phase changes, fusion, crystalline structure inversions, boiling, sublimation, and vaporization, dehydration reactions, dissociation or decomposition reactions, oxidation and reduction reactions, destruction of crystalline lattice structure, and other chemical reactions. Generally speaking, phase transitions, dehydration, reduction, and some decomposition reactions produce endotherrnic effects, whereas crystallization, oxidation, and some decomposition reactions produce exothermic effects. In this study, thermal behaviour of straw and stalk of rapeseed plant is determined by using thermogravimetric analysis, and kinetic parameters are determined by using a basic computer program. The straw-stalk has been collected from arable field in Çorlu- Thrace, the reduced organic materials is not uniformly distributed throughout the plant. Therefore, the sample was air dried and grinded in a wiley mill and then mixed throughly for uniform sampling. Thermogravimetric analysis were performed on a Perkin-Elmer TGS 2 thermogravimetric analyzer with a Perkin-Elmer System 7/4 thermal analysis controller, Perkin-Elmer TGS-2 balance control and Perkin-Elmer heater control units. Samples of 5-6 mg were sent to Chemical&Bioresearch Department of The University of British Columbia, Canada and experiments were performed at this University laboratory analyzer. In order to see the effect of heating rate on thermal degradation and kinetic parameters of thermal degradation reactions, five different heating rates namely 25°C/min., 50°C/min. and 100°C/min. were conducted both in air and nitrogen atmosphere. It is determined that total degradation in air atmosphere is more than nitrogen since air atmosphere is an oxidizing media. And with the increasing of the heating rate remaining undegraded part is increasing. Kinetic parameters of thermal degradation reaction is determined for the active zone where nearly the whole thermal degradation occurs. In the theoretical part of this study thermal anlysis methods and the principles of thermogravimetry and differential thermogravimetric analysis is illustrated. In Table 1 the effect of heating rate on total thermal degradation can be seen. Table 1. Effect of heating rate on total thermal degradation of the straw&stalk of the rapeseed plant. Heating Rate (°C/min.) Active Zone Temperature Range m Total Degradation 25 50 100 271-400 289-464 231-483 64.66 58.37 58.34 XI Differential thermal analysis (DTA) experiments were performed on Shmizadzu DTC 40 analyzer. The analyzer can work up to a maximum temperature of 1500°C. Experiments were conducted in nitrogen atmosphere at heating rates of 10, 30, 50°C/min. 10 mg of straw&stalks were heated up to a final temperature of 850°C. Endothermic and exothermic peaks were observed at various temperatures. In table 2 the kinetic parameters are given obtained from the thermal degradation of straw&stalk of rapeseed in nitrogen and air atmosphere at three different heating rates. And in table 3 and 4 evaluation of thermal degradation of straw and stalk of rapeseed plant in air and in nitrogen atmosphere can be seen. Xll e D, O <="" )="" «m="" o="" i="" a="" fi="" o.s="" n3.s="" ö="" ?s="" x111 2="" İ="" co="" c="" (d="" bû="" tİ=""
|Description:||Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1998|
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998
|Appears in Collections:||Kimya Mühendisliği Lisansüstü Programı - Yüksek Lisans|
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