Afşin Elbistan Linyit Kömürü Ve Rdf’den Üretilen Yarıkok Karışımlarının Yanma Davranımlarının Belirlenmesi

Abstract

Ülkemizde artan enerji ihtiyacı ve petrol, doğalgaz rezervlerinin kısıtlı oluşu buna karşı linyit kömürünün rezervlerinin fazla olmasından dolayı, gelecekte linyit kömürünün öneminin daha da artacağı öngörülmektedir. Ülkemizde kaliteli linyitlerden nem, kül ve kükürt içeriği yüksek, ısıl değeri düşük olan kalitesiz linyitlere kadar çok çeşitli kömürler bulunmaktadır. Ancak, düşük kaliteli linyitlerin toplam rezerv içindeki payı oldukça yüksektir. Uygun koşulların sağlanamadığı yakma sistemlerinin kullanılması, kömürden enerji üretim verimini önemli ölçüde düşürmekte ve çevre kirliliğine neden olmaktadır. Bu çerçevede, düşük kaliteli linyit potansiyelinin değerlendirilmesi için uygun teknolojilerin geliştirilmesi, ülkemizin öncelikli enerji politikaları arasında yer almaktadır. RDF; evsel, ticari veya endüstri proseslerinden çıkan tehlikeli ve tehlikesiz atıkların, geri kazanılabilen malzemeleri (cam, plastik, metal vb.) ayrıştırıldıktan sonra geriye kalan yanabilir özelliğe sahip geri dönüşümsüz malzemeden türetilen alternatif katı yakıttır. Ülkemiz biyokütle potansiyeli içinde RDF’nin payı oldukça yüksektir. RDF’nin kömürle birlikte kullanılması, yenilenebilir enerji kaynaklarının kullanılması konusunda önemli bir seçenek sunmaktadır. Kömür ve RDF’den enerji üretimi dünya genelinde yaygın olarak yakma yoluyla sağlanmaktadır. Kömür ve RDF’den üretilen yarıkoklardan birlikte yakma yoluyla kaliteli yakıt üretilebilir. Kömür yarıkoku ve RDF yarıkoku yakan yakma sistemlerinin ticari boyuttaki modellenmesi, tasarımı ve işletilmesi için kömür yarıkoku ve RDF yarıkoku karışımlarının yanma davranımları ve aralarındaki etkileşimin bilinmesi gereklidir. Bu çalışmada, düşük kaliteli Afşin Elbistan linyit kömürü ve RDF (Refuse Derived Fuel-Atıklardan Türetilmiş Yakıt) kullanılarak kaliteli yakıt üretmek hedeflenmiştir. Kömür ve RDF'den farklı sıcaklıklarda (400oC, 500oC, 600oC, 700oC, 800oC, 900oC) yarıkoklar üretilmiş ve ısıl değeri en yüksek olan kömür yarıkoku ve RDF yarıkoku seçilerek, farklı oranlarda RDF yarıkoku içeren (%10, %20, %30, %40, %50) karışımlar hazırlanmıştır. Linyit kömürü ve RDF ana numunesine, yarıkoklarına ve farklı oranlarda hazırlanan karışımlarına yanma davranımlarını belirlemek amacıyla farklı analizler (kısa analiz, elementel analiz, ısıl değer analizi, FTIR, XRD, XRF, SEM, BET ve tanecik boyutu analizleri) uygulanmıştır. Ayrıca, aynı numunelere yanma davranımlarını belirlemek amacıyla termal analizler (TGA, DTA, DSC, DTG) uygulanmıştır. Deneysel çalışmalar sonucunda, Afşin Elbistan linyit kömürü ve RDF’den üretilen yarıkok karışımlarından yüksek ısıl değerli yakıt üretimi gerçekleştirilmiştir.

The big part of the world energy requirement, which increases in parallel with population and industrialization, is provided from fossil fuels. The difference between energy supply and consumption in our country increases every year and accordingly, our foreign dependence on energy in terms of sources increases as well. Today, issues which are dealing with the environmental pollution resulting from production and consumption of fossil fuels and restricted reserves of fossil resources are the most important problems. Coal which is a kind of sedimentary rock has a very important share of world energy production. Also, coal is the most important energy source of Turkey and most of the Turkish coal’s are low quality lignites having high ash, sulfur, moisture content and low heating value. The amount of low quality lignites inthe total lignite reserves is extremely high. Using inconvenient combustion systems causes significant reduction in the efficiency of energy production from coal and also environmental pollution. Coal burning is a major contributor to global warming. Thus, the development of appropriate technologies for the evaluation of low-quality lignite potential must be one of the most important energy policy of our country. Electricity generation using coal burning produces approximately twice the greenhouse gasses per kilowatt compared to generation using natural gas. Refuse-Derived Fuel (RDF) is a kind of alternative solid fuel that is obtained by proper methods out of domestic waste, industrial waste and toxic waste, and has calorific value. Recycling waste, reuse of waste and use of those that have calorific value allows significant decrease in the waste amount that will be sent for storage, and such practice enables a management that complies with the strategy developed by European Union in the subject of waste management. RDF production and use needs to be reformed and standardized within this scope. Refuse-derived fuel typically consists of pelletized or fluffy MSW that remains after the removal of noncombustible materials such as ferrous materials, glass, grit, and other noncombustible materials. The remaining material is then called RDF. Energy production through the direct combustion of coal and RDF is the oldest known method. In recent years, combustion systems for burning coal-RDF blends together, are being developed. Energy production from coal and RDF is widely provided by combustion. Co-combustion of coal and RDF blends gains more importance in terms of the utilization of low quality coals and RDF economically and reducing the total pollutant emissions. Investigation of the combustion behaviour and combustion kinetics of coal-RDF blends is essential for the modelling, design and operation of the combustion systems at industrial scale. Co-combustion means simultaneous combustion of two or more fuels in the same plant for energy production. Although this mode of combustion has been applied for many years, the interest has been enhanced recently. Co-combustion can be carried out in various ways for various purposes. A coarse classification could be as follows, covering new plants as well as existing ones converted for the purpose. First, a small amount (a few percent of total fuel power) of biofuel or waste is fired together with coal in a boiler, originally designed for coal. Turkey’s large lignite reserves and agricultural wastes, which are important with regard to reduce our energy dependency, are widely evaluated by burning together. In this study, instead of the raw coal and RDF, coal and RDF char, which have higher calorific values are burned together. Various governments worldwide are beginning to put regulations in place and to encourage development of more sustainable sources of power generation in order to protect populations worldwide from the immediate harmful effects on life and health, and to protect the environment for future generation. RDF is appeared to be an important feedstock for three main reasons. First, it is a renewable resource that could be sustainably developed in the future. Second, it appears to have formidably positive environmental properties, reduced greenhouse gas (GHG) emissions, possibly reduced NOx and SOx depending on the fossil fuels displaced. However, it also has negative impacts, such as emissions of polycyclic aromatic hydrocarbons including polycyclic aromatic hydrocarbons, dioxins, furans, volatile organic compounds and heavy metals especially when combusted in traditional stoves. The purpose is to get rid of waste or to replace coal by RDF utilisation. Second, a small amount of fuel with a high heating value is fired together with a fuel having a low heating value that needs thermal support to attain a desired combustion temperature. Third, spontaneous use of co-combustion with fuels in any ratio, depending on price, availability and local supply conditions. The first type is of greatest significance due to its potential ability to reduce the consumption of coal, thereby decreasing the emissions of greenhouse gases. It is of interest to assess the possibility and reliability of such utilisation of RDF and waste in a plant designed for the base fuel (normally coal). Secondly, addition of high-value fuel to a low-value one, or in general terms, combination of any fuels with different properties, may have useful secondary consequences, such as reduction of emissions or improving reliability of operation. Coal and RDF are quite different in composition. Co-firing RDF with coal has the capability to reduce both NOx and SOx levels from existing pulverized coal fired power plants. This could enhance the interest for combinations of fuels, because certain fuel constituents may influence each other, “synergy effects” may take place, leading to an improvement of operation of a boiler and to avoidance of inconveniences related to some fuels. Residues from agricultural production and processing industries are readily availablein large quantities and solid wastes are generated by every social activity. Combustion of these residues can reduce the volume of wastes, allowing for energy recovery and increase of economic returns to rustic communities. Co-combustion of solid residues and wastes with coal in existing power plants is a most interesting option, because apart from the environmental benefits it offers technical and economic benefits, by replacing part of conventional energy sources, while at the same time using existing infrastructures. The knowledge of the behaviour of coal and RDF during combustion not only separately but also together, is essential, as interactions may occur between them that may affect the overall efficiency of the process. It is necessary to know the combustion behaviour and kinetics of RDF-coal or RDF char-coal char blends for the desining of combustion systems to be used. Combustion characteristics of a fuel before it is used in energy production can be determined by using thermo-analytical techniques such as TG, DTG, DSC and DTA which cover a wide range of applications in research, development and economic assessment of fuels. They have been used in a wide variety of areas related to proximate analysis, coal reactivity and heat effects associated with coal pyrolysis, combustion and heat of hydrogenation. Although thermogravimetric analysis technique (TGA) operates in a different condition compared to a real combustor, it provides a rapid and reliable quantitative method for thermochemical processes.