Bazı Türk kömürlerinin yanma profillerinin çıkarılması
Obtaining the burning profiles of some Turkish lignites
- Tez No: 21820
- Danışmanlar: DOÇ. DR. SADRİYE KÜÇÜKBAYRAK
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 145
Özet
ÖZET Ülkemizde, düşük değerli linyitlerden, kaliteli linyitlere kadar çak çeşitli linyitler bulunmaktadır ve ne yazıktır ki düşük değerli linyitlerin toplam rezerv için deki payı oldukça yüksektir. Uygun koşulların sağlanmadığı yakma sistemlerinin kullanılması, kömürden yararlanma oranını önemli ölçüde düşürmekte ve çevre kirliliğine neden olmaktadır. Endüstriyel kömür yakma sistemlerinin tasarımı yapılırken, o sistemde yakılması planlanan kömürün reaktivitesi hakkında bilgi sahibi olmak gerekmektedir.Veya, mevcut bir yakma sisteminde kullanılmakta olan yakıt de ğiştirilecek ise, yakıt adayının reaktivite ve yanma hızı açısından eski yakıtla kıyaslanabilmesi için, yanma karakteristiklerini gösteren bir testin yapılması gerekmektedir. Kömürün termogravimetrik analizinin hava ortamında gerçekleştirilmesi sonucu oluşan eğriye“yanma profili”diferansiyel termal analizin hava ortamında yürütülmesi sonucu oluşan eğriye ise“yanma eğrisi”denir. Bu eğriler kömürün yanma karakteristikleri konusunda standart analiz yöntemlerinden elde edilemeyen önemli bilgileri içerirler. Türkiye'nin değişik yörelerinden toplanmış olan 25 linyit kömürü numunesinin yanma profilleri ve yanma eğrilerini belirlemek suretiyle, yanma karakteristikleri araştırılmıştır. vı
Özet (Çeviri)
DBTAININE THE BURNING PROFILES OF SOME TURKISH LIGNITES SUMMARY In the 1960' s coal was lasing ground as the principal primary fuel far electricity generation. Oil mas plentiful and cheap, and nuclear power appeared to be poised for rapid growth. By the mid 1970's the fuel situation had undergone a drastic change. The price of liquid fuel had increased sharply and, with the exception of the oil-exporting countries, hardly any new oil fired power stations have been built anywhere else since that date. It was inevitable, therefore, that there should have been renewed interest in utilizing coal for power generation. Coal is Turkey's major fossil fuel resource which is used primarily for the production of electrical energy. The combustion of coal, either in a bed or as pulveri zed coal in a suspension, is primarily a matter of com bustion of carbon and volatile matter. It is agreed that the burning of coal involves three stages: D- The release of the volatile matter resulting from the heating of the coal, 2)~ The burning of the volatile matter in the gas phase, and 3)- The burning of the solid residue of carbonaceous matter. Thermal analysis plays an important role in deter mining the combustion characteristics of coal. VllThermal analyses are those instrumental dynamic analysis methods that monitor the physical and chemical transformations which take place in the structure of a substance being heated or cooled. Dn this principle, a large array of instrumental methods has been developed based on variations in mass, volume, and temperature between sample under analysis and a thermally inert substance. Among previously mentioned methods, those that have given the most encouraging results in compositional analysis are Differential Thermal Analysis (DTA), Thermogravimetry (TB) and Derivative Thermogravimetry (DTG). DTA covers those techniques which record the tempera ture difference between a substance and a thermally inert material when the two substances are undergoing identical temperature changes within an enviroment which is heated and cooled in a controlled ratio. This method was developed following the perfection of thermocouples as precise temperature gauges. The thermal analysis technique of thermogravimetry (TG) is one in which the change in sample mass (mass- loss or gain) is determined as a function of temperature anqV&r time. Three modes of thermogravimetry are commonly used: a)- Isothermal thermogravimetry, in which the sample mass is recorded as a function of time at constant tempe rature, b)- Quasi-isothermal 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 enviroment whose temperature is changing in a predetermined manner, preferably at a linear rate. The resulting mass-change versus temperature curve provides information concerning the thermal stability and Vlllcomposition of the initial sample, the thermal stability and composition of and intermediate compounds that may be formed, and the composition of the residue, if any. To yield useful information with this technique, the sample must evolve a volatile product, uihich can originate by various physical and chemical processes. The rate of decomposition reactions occurring in coal under the action of heat may best be studied by means af TB..The weight curves obtained make it possible to derive the rate of loss in weight as a function of tempe rature and time. In the design of industrial coal-fired boiler furnaces, it is of importance to have an assessment of the reactivity of the intended fuel. Alternatively, if it is proposed to change the fuel supply for an existing installation, it is advantageous to have a test which allows the burning characteristics of the candidate fuels to be compared with the original in terms of reactivity or burning rate. It has been established a test in which the rate of weight loss of a coal sample burning in air was plotted against temperature and named the“burning prof ile”test. The DTA determinations of coal in air are essentially exothermic and their configurations, although influenced by compositional variations, both organic, inorganic and rank, represent the large amounts of heat generated by burning. The information obtainable under these conditions is relatable to combustion characteristics, ignition temperatures, and relative resultant heats of combustion. The term“combustion curves”has been suggested for the application of DTA to the monitoring of burning coal to distinguish it from the TE curves (burning profiles). The purpose of this study was to obtain the burning profiles and combustion curves of some Turkish lignites. The lignite samples used are from: IXD- Çayırhan- Ankara, 2)- Aşkale- Erzurum, 3)- Bağyaka- Muğla, 4)- Merkeşler- Bolu, 5)- Çan- Çanakkale, 6)- Dodurga- Çorum, 7)- Akpınar- İstanbul, 8)- Çiftalan- İstanbul, 9)- Gediz- Kütahya, 10)-Ilgm- Hanya, 11)-Mengen- Bolu, 12)-Mihalıçcık-Eskişehir, 13)-Mila&- Muğla, 14)-0rhaneli- Bursa, 15)-Seyitömer- Kütahya, 16)-Soma- Manisa, 17 ) -Tep eb aşı -Konya, 18)-Tınaz- Muğla, 19)-Karakaya- Tekirdağ, 20)-Tunçbilek- Kütahya, 21)-Yatağan- Muğla, 22)-Merzif an- Amasya, 23)-Sargun- Yozgat, 24)-Yeniköy- İstanbul, and 25)-Elbistan- Kahramanmaraş All coal samples studied were prepared as for the ASTM standard proximate analysis, i.e. less than Q.25mm. According to the ASTM standards the moisture content of the lignite samples varies between 2.0-48.0%; the ash content between 6.2-40.6%; the volatile matter content between 22.2-46.4%; the fixed carbon between 11.8-53.4%; and the heat content between 10.3-27.7 MJ /kg.Differential Thermal Analysis was carried DUt using a Shimadzu DTC ^0 analyser. 2D mg lignite samples were spread uniformly an the bottom of the crucible and the furnace heated at a constant 10K/min while being swept by air at a rate of kQ cc/min until 1D73 K and held for 1Ü minutes at constant tempera ture. Reference material was oi. -Alumina, Thermogravimetric analysis was carried out using a Shimadzu TG **1 thermal analyser. The work conditions were the same as with DTA measurements. The areas under the exothermic peaks of the combus tion curves (DTA plots) are proportional to the amounts of active material present in the coal and to the calorific value of the coal sample measured by using oxygen bomb calorimeter. The combustion curves of the lignite samples contain initially a small endothermic peak, due to water loss and one or two exothermic maxima due to the combustion of the volatile matter released on heating, followed by the burning Df the residual carbon. Decreasing volatile matter yield and increasing car bon content of the lignite sample appear to cause increased peak temperatures of the combustion curve. The heat release rate of the lignite samples differ considerable. The DTG curves of the lignite samples contain generally two maxima due to the moisture loss and combus tion. The main characterising paint an the DTG curve af a coal is the“peak temperature”where the rate of weight Idss due to cumbustion is at a maximum. This maximum ranges for the burned Turkish lignites between 6G0-85G H depending on the carbon content of the sample. A high XIpeak temperature is indicative of a less reactive coal, Kinetic parameters, such as activation energy and order of reaction are obtained using DTE date of the lignite samples. Xll
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