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ÖZET Bu çalışma da, ülkemizdeki toz kömürlerin ekonomik bir biçimde değerlendirilmesiyle ilgili teknolojilerden birisi olan biriketleme yöntemi tanıtılmaya çalışılmış ve konu; katkı maddesi ve presleme konusundaki gelişmelerde ilave edilerek oldukça geniş tutulmuştur. Ülkemizde yapılan biriketleme çalışmaları ve bu çalışmalarda elde edilen optimum neticeler verilerek, Çanakkale-Çan linyit kömürünün sülfit atık çözeltisi, melas ve ataktikpolipropilen ile biriketlenebilme koşulları incelenmiştir. Deneyler; sonuçlar, grafikler ve tablolar yardımı ile izah edilerek Sonuçta; Çan bölgesi kömürlerinin katkı maddesiz biriketlenemiyeceği gözlenmiş, katkı maddeli biriketlemede en uygun katkı maddesi alarak ataktik polipropilen bulunmuş ve % 3 oranında katılmasının en optimal sonucu verdiği belirlenmiştir. -xv- BRIQUETTING STUDIES WHICH HAVE BEEN CARRIED OUT IN OUR COUNTRY DP TO DATE AND THEIR EVALUATION. SUMMARY A considerable amount of domestic fuel is required for office and household heating purposes in Turkey. It is inevitable to Use our lignites in the first place to meet some of this requirement. For this reason, a part of Turkey's lignite production should be used in lump size while other parts subjec ted to briquetting with or without binders. Our lignites required by various, especially the household needs, are inspected. Attempts made to increase lignite production requires mechanization which results in the generation of high proportion of fines in run-of-mine coal. One of the economical processes, presently employed in our country, for the beneficiation of coal fines is known to be briquetting. In general, the calorific value of Turkish coals are low and moisture, ash and sulphur contents are relatively high. Also, approximately 60 % of Turkish coals may be crushed into small particles during transportation and storage. These coals have moisture contents as high as 40-50 %. There fore, during their utilization at the households and boilers, some of the inherent. Binderless briquettes have been produced for more than 100 years. In this process, the coal particles are pressed at an optimum moisture content. Generally, cold and binderless briquetting can not be applied to all kinds of coal. Soft coals are generally briquetted by this process succesfully. -xvi-Binder less briquet ting may be divided into two sub groups as cold and hot briquetting. The classical cold briquetting in generally applicable to soft lignites having particle sizes 0-4 mm, 0-5 mm and 0-6 mm mois ture contents between 15-18 % and pressed at 60-80 C.. In the hot briquetting, coal particles are pressed at 380-400 C when the coal is at it's plastic behaviour at a suitable pressure. The briquettes are cooled to about 200°C and then is removed from press mold. Briquetting with binder is an old process which finds appli cation for hard coals that can not be briquetted with binderless briquetting. The amount of binder is important factors for the applicability of the process. Depending on the structure and characteristics of the coals, strong briquettes generally need 3 to 12 % binding material. In this type of briquetting the coal is crus hed using hammer mills. The.drying of the coals ace relaised using fluidizied bed and entrained flow type dryers. The homogenation of the coal particles with binder is made using single and double directional moving mixers. Homogenity of the mixture is mostly achieved in pug mill type mixers. At the last stage of briquetting the coal binder mixture is pressed using double roll presses. The strength of pressed briquettes are improved by storing them for a length of time. THe types of binding materials used in briquetting may be clas sified into three groups as organic, inorganic and combined type mate rials. The main organic binders are coal tar, coal pitch, petroleum bitumen and asphalt, wood tar, natural and synthetic resins. -xvii-heat is used to evaporate the water present in the coal. Also, due to the inapropriate burning appliances, small coal particles drop thorough the grates before complete combustion. Under these conditions, briquetting of the small coal particles may be an appropriate solution. The briquetting is a technique used for more than 150 years in various countries and is becoming important in our country in the latter years. Briquetting may be defined as the production of high calorific value, strong and homogenous fuel from coals by reducing the moisture to an optimum level. There has been theorical efforts to explain the briquetting technique the important briquetting theories may be named as adhesion, capillary, bitumen, moleculer energy and interlocking each other theories. In briquetting, adhesion theory is based on the adhesion for ces between particles that have optimum moisture. According to the capillary theory, coal under pressure gives out of it is capillary water. This, forms a water bridge between the particles, in this way water acts as a binder. In the bitumen theory, bitumes in the coals under heat and pressure softens and particles are held together. Moleculer Energy is assumed to tie particles together in moleculer energy theory. This is also known as Kegel Theory, in which the moleculer energyis propertional with particle size of the coal. The indensity of mole culer energy increases as the coal particle size decreases. This is in accordance that as the coal particle size decreases the total contact area between particles increase. This increases the bonding among the particles. Interlocking each other theory it is proposed that it is pos sible to produce stronger briquettes from coals without bitumen. Briquetting techniques may be classified into two groups depending on binding agent and temperature media. These are briquettes with and without binding agent and hot and cold briquettes. -xviii-Starch, sulphide ablauge and molasses. All of these may form strong briquettes but they have air pollution characteristics. The organic binding materials Include clay, lime, cement and some alkaline silicates. Inorganic binding materials are cheaper than organic types but they have the disadvantage of increasing the ash content of briquette. The combined binders are mixture of organic and inorganic types. The important combined binders are watersulphide ablauge, water-tar emilsions, asphaltiteclay and coal tar-lime. Selection of the proper binding agent is of paramount important in briquetting. A proper binding agent should have the following characteris tics; high binding capasity, hardening, water resistance coherence to the coal, combustion charasteristics and fast ignition, acceptable economics and avability. The advantages of briquetting technology may be summarized just below: 1. Moist coals have low calorific value. Before the briquet ting, coal is dried with on appropriate drying process. 2. It is difficult to burn or use industrial purposes the coals which have small particles. One of the solutions of this problem is to briquette with an appropriate Press. 3. Uncontrolling combustion of small coal particles may prevent with briquetting. A. Air pollution may be decreased important degree appropriate binders using in binding briquetting. 5. Because of pressing, the volume of coal particles may be decreased. So that, transporting and storing of coal particies can be easy before then. 6. Some Useless materials is evaluated by using as binder in briquettes. 7. Small coal particles may cause the pollution of environment, These small coal particles can be changed into stable form with briquetting.The fact that coal, after briquetting, is used as a fuel has begun to be Important in our country. In this study, the conditions of being able to briquette the dust of lignite obtained from Çan region with the sulphide ablauge, molasses and A. P. P. were investigated and effort has been made to increase the durability of the briquettes had against the water and atmospheric circumstances. The effect of the coal particle size, percentage of moisture and pressure on the quality of briquettes were assessed by determi ning the hardness, water resistance period and water absorption ratio. In order to determine the hardness of products, the drop (Shatter tests) are used. From binderless briquetting experiments it is understood that 14 % moisture is the optimum value for the best quality products. The relationship between the briquetting pressure and shatter index are investigated. For 50 tons briquetting pressure and 14 % moisture, the maximum shatter index was determined to be 659. These briquettes had a very low water resistance period (below 1 minutes). In these experiments, the optimum particle size was changed between 0-6 mm. Briefly, it was observed that the briquetting without binder was imposible. This conclusion is a results of comparison of the characteristics of briquettes with the national standarts. These standarts spesify a limiting shatter intex value of 1000 and water resistance period of 1 hr which are far from being satisfied by binderless briquettes. In briquetting with binder, the conditions that satisfy the standarts are determined. 5 % molasses, 8 % sulphide ablauge and 3 % A. P. P. the briquetting standarts are satisfied. Under 30 tones fixed briquetting pressure and 8 % sulphide ablauge, the average shatter index of 1269 and water resistance is sufficient. Under similar pressure and 5 % molasses, the average shatter index were determined to be 1508, but there is no water resistance. For 3 % A. P. P. the shatter index were 1364 and the water resistance is satisfied. As a general result, Çan coals may be briquetted satisfactorly using sulphide ablauge, molasses and A. P. P. The most favorable -xx-technical results are obtained for A. P. P. which may be proposed as the binder. The material contains less sulphur than sulphide ablauge. So that, it will less cause air pollution. -xxi- 215 |
