Afşin-Elbistan linyit kömürünün briketlenmesi
Briquetting of lignite
- Tez No: 66560
- Danışmanlar: PROF. DR. SADRİYE KÜÇÜKBAYRAK (OSKAY)
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Briketleme, Kahramanmaraş-Afşin, Kahramanmaraş-Elbistan, Kömür, Kömür briketleri, Linyit, Briquetting, Kahramanmaraş-Afşin, Kahramanmaraş-Elbistan, Coal, Coal briquettes, Lignite
- Yıl: 1997
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Yozlaşan kömür kaytanı önlemek için uzun yulardan beti birçok ülkede uygulanan briketleme, son yıllarda ülkemizde de uygulama alam bulmuştur. Bu konuda, henüz yeterli olmamasına karşın çeşitti araştırmalar yapılmaktadır. Bu çalışmada kömürün briketlenmesinin yararları ve ülkemiz açısından önemi üzerinde durulmuş, Afşin-Elbistan yöresine ait linyit numunesinin katkı maddesi/ ve değişik katkı maddeleriyle briketlenme koşulları araştırılmıştır. Briketlerin nem içeriği, presleme basıncı, kullanılan katkı maddesinin cinsi ve oranı değiştirilerek oluşturulan briketlerin, kırılma ve ufalanmaya karat dayanıklılıkları ısıl değerleri, yanar kükürt içerikleri, suya dayanıklılıkları ve bıraktıkları kul miktarları Bu deneysel sonuçlar çerçevesinde; ısıl değeri oldukça düşük, nem içeriği yüksek olan ve kolayca ufalanabilen Afşin-Elbistan linyitlerinin yakıt önselliklerinin, briketleme yoluyla iyileştirilebileceği ve uygun özellikte kömür briketleri üretilebileceği Linyit kömürünün ısı üretimine katkısı olmayan, buharlaşması için de ısının harcanmasını gerektiren yüksek nem içeriği, briketleme aşamalarında azaltılarak yakıtın ısıl değeri artırılırken, yanma olayı kolaylaştırılmaktadır. Kömür tozlanma briketlemeden önce belirli bir nem oranına kadar kurutulması, tartma ve depolama masraflarım dil azaltmaktadır Ayrıca, linyitlerimizin kükürt içerikleri ile bıraktıkları kül miktarlarının yüksek olması, bu kaynaklarımızdan kaliteli ve çevreye daha az zararlı olan bir yakıt elde etmek için briketleme yönteminin kullanılmasını gerekli kılmaktadır. Türkiye linyit rezervinin bu gün için 8375 milyon ton civarında olduğu bilinmektedir. Ülkemizin; petrol rezervinin düşük olduğu ve ithalatın ekonomimize getirdiği yük gözönüne alındığında, ulusal enerji kaynağımız olan linyit kömürünü değerlendirmede uygun bir yöntem olan briketlemeye büyük önem verilmesi gerektiği açıkça görülmektedir.
Özet (Çeviri)
BRIQETTING OF LIGNITE SUMMARY The pfocess of briquetting consists in appiying pressure to a maaş of paıticles wiihor vnthoui the additioa of a hinder to fbnn a compact mel By briguetting, coal is CûflVefted fiofiü antHflimhfli friflhtfe fnoterial anntent ît tA a hafld ftmmmaf JMöduct whİcb. hflg a highar calûfific vahıe. Britpıettes may also be catbonized to yield smokeless çeke briguettes of stili bigher quality. Manythâoreticalappfoachestobriguetiingpra tvihımı*n «vıl^ııtflf anatyy ftflpîltflfy aftyrç-gjrt fmA fflteriıvlfing «ıeh ı^h^r fh<yvty la brûn^ting, adh^ıîoo âımy is based on fl» adhâsûm fotces bâtıvcâa tfflrticles ftmt have optimum moûftme. Tn bimmea theoıy, bitumea tu the coûl ı«ifW beaf anA t&easûte so&eo. <*“^ partides aıehcld tog^ter. m capillaty meoy, coal uoder pıessure gimsa «it üs capükty wate- wfaMı forma a water brid^ betweea patikte, in mis way water acts as a bimî». Mblficular eoKfiy is assumed to tic fHg particimi together in «yyl^vular eaetgy fluay. Thjg iğ fllflrt koron as K^el H^ocy, in whkh tbe «u%lafliılflf esutfgy is pfifyprtftjrtnat yyith payete ^”^ ^f^hff *>n<M Tt^ jnt<>ngüy <>f mnlaftiılar ^>m>fgy «K>fiMi^ffs as me CM! particle size decreases. As the eoal particim size decteases fltt total cooiact atça betwecu pûtticlcs toctcasc. This iucRsasfis tf**^ btmdiıut otM^np ttı<> particim. Tptefİftfttring ^a<*h OÜDâf fbââfY İS g**M*atty fîjT htmferit^aı bfİOUetteS an^ daim ibatüispDssibktopfDdııcestıafi^bnq|Ktiie»â^(XMls^^Nodoubt fbis may oaty apply to soft coals. The brUpj^tmg Üıeory in lealüy may be tbe ftrtttıhitMiiîftn «f ati ihf*» RrifflifftfTp <MMI be <fat*ft vvifh OT vvitbiMit a btodcr. Bindâfl^s briauettiııg may be divided into two sub groups as cold anH but bnquetimg. Tbe classical cold briqiKltmg in gâ&mlty appli^ble to soft lignües baving pûtticle size 0-4 mm^ 0-5 mm and 0^ mm, moisÜMB contents betweea 15-18%andpıessedat333-353K. Iamehûtbriqıı^tiflg, coal partide atepıessed at 653-673 K. Whfia the eoal is atplasticbehavioratasuitablepıessure. Tbebnquettesatecooledtoaboııt473Katd men rernoved fran pnas moUL Oenemlly, cold and famderiess briqiKtting can not be applied to ali ktnds of coaL Soft coals are genecally briquâtted bjr mis pcocess successfulfy. Btown coal may be convected into briquettes wimout the aid of a binder. Pressurc alone is used to compact the coal, and tbe success of the ptocess depends on the catefiıl pıepatation of the coal and proper design of fhe pcesses. As coal mamıes, it becomes hatdef ««^ moıe Hifficıılt to briquette without a binder. There have been numetom atfempts to briquette bituminous coal wifhout a binder, «“^ in geneual, mneb higber pıessme is ıequired man mat needed by fatown coaL in nust cases me mechanical stabîliiy and water ıcsistance of fbe briguettes ate not satis&ctoıy because an elastic defomıaüon occura during nfessing at a highpressure. Bituminous coal often softens when heated. With increased temperature, coal becomes progressively less elastic and more plastic, but this change is not tegular. Using binder in briquetting is an old process which finds application for hard coals which can not be briquetted without a binder wMrfyrtaj The hinder helps in agglomeration and also gives cohesive strength to the briquette. The amount of binder is an important actor for applicability of the process. The binders used m briquetting are generally much more expensive than the coal itself, and thus a balance has to be maintained between the cost of the additive and the quantity needed to make a desirable briquette. For most purposes, a water resistant briquette is required and this factor has so far limited the choke of the binder to some extent Thft following ttf» thft priT*pt<* wtqtwfiMiMmtg nf hrnka ııaad in the «wniifaMnn» of coal briquettes: * ttijgfa ifrengtaand high rate of agglomeration, * Absence of inert material, * Simplicity of use, * Provision of adequate mechanical strength, wet strength and hot strength in * Absence of objectionable operating conditions for operators. The types of binding materials used in briquetting may be classified into three groups as organic, inorganic and combined type materials. The main organic binders are coal tar, coal pitch, petroleum bitumen and asphalt, wood tar, natural and synthetic resins, starch, sulfide ablauge and molasses. All of these may form strong briquettes but some of mem have air pollution characteristics. The organic binding materials include clay, lime, cement and some ntlralin». ailtftatea Tnftfg^mifl binding materials are generally cheap but mey have the disadvantage of increasing the ash content of briquette. The combined binders are mixtures of organic and inorganic types. The important combined binders are water-sulfide ablauge, water-tar emulsions, asphaltite- elay and coal tar-lime. Temperature, briquetting pressure, pressing time, binder, type of coal, moisture, petrografine composition, humic acid ratio, volume of capillaries, size of the coal, type of press and pretreatment are the most important factors that influence the coal Briquettes are made in different shapes and sizes, rectangular, ovoid, cylindrical, tetrahedral, pillow and spherical. The shape and size of bimminous coal briquettes depend essentially on their application. The briquetting of coal involves the stages of grinding, drying, metering, mixing, heating the coal, pressing and cooling tiie briquettes before loading them. The technological assessment of briquetting process includes an analysis of coal characteristics, experimentation to formulate a suitable briquette and an engineering Crushing and Grinding: The aim of crushing the coal is to obtain a uniform product which has a high-bulk density so that regular and uniform füliııg of the moulds Xllcan be achieved. In all grinding processes it is necessary to use grinding equipment that minimizes the production of additional dost Drying: Water has a great influence on the hriquetting process, especially on the wetting and flfttrawvn between the coal and the bituminous additive and on the strength of the resultant briquette. To achieve a coal with a constant moisture content, producers use different lypes of coal dryers. Metering of Coat and Binder: To obtain briquettes with uniform «w^bfltH^l properties and to retain uniform briquetting conditiom,ü is necessary to meter the coal htrater <HMJ Ainriliflty materials act-iwateiy and imiformly Mixing and Heating: The step of mixing coal with. a binder and heating the mixture, determines, to a great extent, the quality of the final product After the metered addition of the solid or liquid binder (ifused) me mixture is raised to about 20- 25 K above the softening point of the binder. Evaporation of Water (Tempering): The hot mixture leaving the steam-heated pug mill at about 363-373 K, is cooled in a horizontal conveyor to a temperature within a few degrees of the softening point of the additivebefbre entering the press. This temperature stage is necessary to reduce the temperature of the mixture to a level at which the material is still sufficiently plastic to be moulded but not too plastic to prevent pressing and subsequent handling. Pressing: The briquetting press may generally be divided into: J2 * Low pressure presses: with p£ 500 kg/cm: * Medium pressure presses: wifh6G0<p£l2G0kg/cm.: * High pressure presses: with 1200 < p £ 2500 kg/cm2 The first group may comprise table and roller presses which are used for briquetting with binders. High pressure briquetting of hard lignite is carried out by means of ring roller presses. Cooting Conveyor Belts and Loading: When the pressed material leaves the pressing machine, it should be cooled until it acquires a resistance suitable for loading and fawnffing conditions. The cooling process is performed with low speed conveyor belts under ambient conditions. Lignite is the primary national energy source of Turkey and its reserves are approximately 8.4 billion tons. Turkish lignites are characterized by high moisture, sulphur and ash content Their low calorific value is another disadvantage in energy production. Direct combustion of high sulphur lignites produces flue gases containing large amounts of sulphur dioxide which is one of the major atmospheric pollutant Therefore, mere is an. urgent need for the reduction, of sulphur dioxide and particulate matter fttwiggirtna mstead of using petroleum based fuels, a technology using Turkish raw materials and lignites as a ”fuel" should be developed. The major method of upgrading of low quality lignites for household heating is the briquetting process. By briquetting Xlllthe lignite dusts, these low grade fuels can be converted into a compact, stable and inexpensive fuel to be used for household heating. Some of the Turkish lignites were easily hriquetted without a binder and briquettes having acceptable properties were obtained. However, in general, Turkish lignites cannot be hriquetted successfully, and therefore a binder may have to be used. Briquetiing parameters such as binder material water content, pressure and temperature of heat treatment are the most important process variables. Although Turkish Lignites known as not suitable or very difficult for hriquetting researches have shown that it is possible to obtain reasonable briquettes by using special procedures and different bind It is necessary to make systematic and multiple tests to reach the goal Afşin-Elbistan lignites are located in Eastern Anatolia and their total reserves ate estimated as 3.S billion tonnes. They have low calorific value, high ash level and high moisture content and dust easily during mining and utilization processes. Because of their properties the increasing use of Afşin-Elbistan lignites presents some environmental problems. The most promising technology available for the ırfilfaatirm of these low-grade lignites are reported as pulverized combustion and hriquetting. Pulverized combustion is being applied at the 4x430 MW capacity power station plant located m the Afşin-Elbistan region. Afşin-Elbistan lignites can be evaluated for household heating purposes in the eastern provinces of Turkey. For this reason, in this work, lignite samples from the Afşin-Elbistan area were hriquetted with and without additive to obtain a solid fuel with higher quality. The lignite sample was first air dried to 20% moisture content and th**» crushed and sieved to 0-6 mm particles, taking care to wmim«i«» oxidation The sample was men dried at 378 K to different moisture contents. The moisture content values were chosen according to the optimum moisture range, known to be S- 15%, for hriquetting of Afşin-Elbistan lignite. A series of experiments was carried out to determine the effects of different moisture contents of me lignite samples (8, 10, 12 and 15%) and of the hriquetting pressures (4246 kg/cm3, 5662 kg/cm2, 7077 kg/cm3 and 8493 kg/cm3) on the shatter index and compressive stress of the briquettes obtained without additive. Another series of experiments were conducted at 15% moisture content and under 5662kg/cmz, 7077 kg/cm3 briquetttng pressures using sunflower shell, potatoes shell, sawdust and molasses as additives. The blends oflignite and additive were prepared to contain 5%, 10%, 15%, and 20 wt% additives mentioned above. During these experiments, the effect of percentage of additive (in (he sample blend) on the «hatter index and compressive stress of briquettes obtained at 5662 kg/cm3 and 7077 kg/cm3 hriquetting pressures were observed. Since the purpose of briquetting is me benefication of low quality lignite, the percentage oflignite in me briquettes should be kept as high as possible. Therefore, the highest additive percentage to be studied here was selected as 20%. In another series of experiments, the blends containing lignite and Siberia coal were hriquetted. In these blends, the percentage of Siberia coal were selected at 30, 40 and 50%. The briquettes obtained, each 15 g in weight, were cylindrical in shape with a cross sectional area of » 7 cm2 and â volume of about 21cm3. All briquette samples were stored under ambient conditions for seven days before testing. Three briquettes were prepared for each set of experimental conditions and the arithmetic averages of the measurements were calculated. XIVImpact resistance kmeasııred using arbi^ The shatter indices were determined by dropping the each briqueto from a heigM of 180 cm onto a steel plate and measuring the percentage of the sample retained on the sieve; this was repeated until all the particles leaned by «nattering passed through a 20 mm sieve. Finally, the sum of the all percentages was added to find the shatter index. Crushing strength is a measure of the volumetric breakage of the briquette and is dependent upon pre-existing gross flows, fissures and pores of size greater than the size of particles used in the micro strength tests. The compressive stress of each briquette was measured in a standard manner using an Instron table model 1195 testing machine. The fiat surface of the briquette sample was placed on the horizontal metal plate of the machine. A motorized screw slowly reduced the distance between this metal plate and a second one parallel to it An increased load was applied at a constant rate until the test sample failed by wa^lrifig or breaking. The load at the fracture point, ie. the maximum load, was converted to compressive stress. The water resistance of the briquettes was arbitrarily tested by immersing the briquettes in a container filled with cold tap water and measuring the fime required for the onset of dispersion in water. The results suggest that the moisture contents of the lignite samples significantly increased the gtmfter index and compressive stress of the briquettes obtained. Moisture contents higher than 15% were not studied since it is known that an increase in moisture content causes a decrease in the calorific value of coal Therefore, the optimum moisture content of Afşin-Elbistan lignite was chosen as 15%. It can be concluded thai Afşin-Elbistan lignite can be briquetted successfully without binder, with a moisture content as high as 15%atabriquetfingpressureasktwa3 4246 kg/cm2. The effect of additive percentages on the compressive stress and shatter index of the briquettes were also determined. It is clear from the results that the compressive stress increases as the additive percentage is increased. The compressive stress of all briquettes produced using lignite-additive blends was greater than the nrnrnmim value of 130 kg/cm2. The shatter indices of all briquettes were also greater than the minimum value of 2000 which are dictated by briquetting standarts generally. The blends containing of lignite and Siberia coal were briquetted with, and without additive in order to increase the calorific valu« of n^ produced briquettes. In these blends, the percentage of Afşin Elbistan lignite content was restricted to 50% since the purpose of this study is the evaluation of low quality Afşin-Elbistan lignite. The briquette aafnpw produced without additive have low gfarffep index, compressive strength and water resistance. In order to increase these properties of briquettes Afşin Elbistan lignite and import coal blend was briquen^ usmg additives such as sawdust, sunfiower shell and molasses. The compressive stress value of all briquette samples containing Afşin- Elbistan lignite, import coal and molasses, sawdust or sunfiower shell was greater than the mtntmnm value of 130 kg/cm2. The shatter indices of them were also greater than themtrimum value of 2000. Therefore, it can be said that molasses, sawdust and sunfiower shell are good additives for the briquetting of Aişm-Elbistan lignite, and may be used successfully. Potatoes shell additive was not suitable for Afşin Elbistan lignite as additive. The briquettes prepared using Aişm Ettnstan lignite, import coal, sawdust and molasses gave the highest ahqtfer index ««d compressive stress. XVUsing import coal, sawdust,molasses sunflower shell as additives in enqueuing Afşin-Elbistan lignite increased the quality of the produced briquettes. Briquettes produced from Aişin-Elbistan lignite with and without any additive were not water resistant XVI
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