Yanma ve yanma ürünlerinin hava kirliliğine etkileri ve Ağaçlı-Keşan linyitlerinin Km. 9003 analizörü ile baca gazlarının analizi

Abstract

Bu çalışma da, yakıtlar, özellikleri ve yanma alayı incelenmiş, fosil yakıtların yanma sonucunda açığa çıkardıkları ürünlerin hava ve çevre kirliliğine alan etkileleri araştırılmıştır. Yanma sonucu oluşan SD2 ve CG gibi gazların açığa çıkmasının önlenmesi için yanma öncesi ve yanma sırasında alınabilecek önlemler irdelenmiştir. Hava kirliliğini önlemede yakılan yakıt kadar yakma sisteminin uygunluğu da önem taşımaktadır. Bu konu dik kate alınarak yakma sistemleri, iyi bir yakma için uyulması gereken koşullar araştırılmış, yakma sistemleri genel hatları ile tanıtılmıştır. Son senelerde özellikle kış aylarında Ankara, İstan bul, Erzurum gibi büyük kentelerimiz hava kirliliğinden şikayetçi hale gelmişlerdir. Hava ve çevre kirliliği konusunda basında ve kamuoyunda oluşan tepkiler takip edilerek basında, bu konu hakkında çıkan makaleler toplanmış ve ekler kısmında verilmiştir. Oluşacak hava kirliliğinin en aza indirilebilmesi için ideal bir yanmanın sağlanması gerekmektedir. Yakma işleminin ehliyetli kişilerce yapılması halinde bunu sağlamak ve yanma veriminin yükseltmek mümkündür. Ayrıca yanma verimi ve oluşan gazlar otomatik ölçüm aletleri ile ölçülebilir. Yapılan deneysel çalışmada bu amaca yönelik olarak Universal KM.9DG3 baca gazı analizörü kullanılmıştır. Deneylerde Ağaçlı ve Keşan kömürleri yakılmış elde edilen sonuçlar tablo ve grafikler halinde gösterilmiştir. Yanma sonucu oluşacak Sü2 gazının yanma sırasında tutulması için kireç katılarak yapılan deneylerde, SD2 gazının tutulması açısından olumlu sonuçlar alınmış olmasına rağmen ısı kaybına ve curuflaşmaya sebebiyet vererek ocağa hava girişini engellediğinden, böyle bir uygulamanın ekonomik ve prafik olmadığı gözlenmiştir.

A bailer requires a source of heat at a sufficent temperature level to produce steam. Fossil fuel, utilized for the geration of steam, is generally burned directly for this purpose in the furnace of the boiler, although it may be used in the from of waste heat from another process. Combustion may be defined as the rapid chemical com bination of oxygen with the combustible elements of a fuel There are just three combustible chemical elements of significance-carbon, hydrogen and sulfur. Sulfur is of minor significance in corrosion and pollution problems, During combustion coal react uith oxygen from the air to liberate heat energy. The fuel elements-princi- pally carbon and hydrogen-are converted into carbon dioxide (CGg) and uater vapour (H20). As with other fuels it is most important to ensure that coal is com pletely burned in the combustion process. In practice it is impassible ta achieve complete combustion by supplying the exact amount of air required ta burn each kilogram of coal present so that excess air has to be supplied. An insufficient supply of combustion air is responsible for unburnt fuel in the form of vola- tiles (mainly carbon monoxide and hydrogen) and also in the from af non-valatiles, namely unburnt carbon. If too much combustion air is supplied unused air absorbs heat from the combustion zone. The heated air is then entrained in the flue gas stream and it is subsequently lost to atmosphere. To minimise the loss of heat from the combustion equipment XUl it is necessary ta supply the correct amount of excess air, no more and no less. The boiler operator therefore requires guidelines on the quantity of excess air which must be supplied to minimise heat losses. Fortunately there is an easily measurable parameter which is directly related to the quantity of excess air supplied for combustion. This parameter is the percentage carbon dioxide (%CD2) in the flue gas. In practice if the % C0Z is in the range 12% /\k% for caal firing the air supply is satisfactory. In practice the supply of combustion air to a bed of coal consists of two air streams known as primary air and secondary air. Primary air is supplied beneath the grate and travels up through the fuel bed. Oxygen in the primary air combines with coal on the grate to achieve the first part of the combustion process. The remaining air necessary for completing combustion is admitted separately as secondary air. The secondary air completes the combustion of all volatile matter, including smoke, which iş released from the coal during the preliminary stage of its combustion. Secondary air is supplied above the fuelbed and is admitted through ports is the furnace door. Complete combustion of coal is achieved by the use of primary and secondary air in the right proportions. The secondary air supply must be adequately controlled and correctly mixed with the com bustible gases leaving the fuelbed to ensure that the fuel is completely burned with the use of as little air as possible. To conserve energy in coal fired installations it is necessary to minimise the loss of fuel and heat from the combustion equipment. The major heat losses asso ciated with coal firing are; * Heat loss in flue gas * Heat lass due tD carbon in ash Heat loss in dust and flyash (grit lass) * * Heat loss due to radiation and convection xiv The quantity of heat last to the atmosphere in the from of flue gas depends on the level of excess air used for combustion and the temperature Df the flue gas. Flue gas losses can be minimised by maintaining: * % C02 content in the range 12% - 14% * Lou flue gas temperatures (200° C, - 24G° C) * Little or no smoke. Heat loss in the flue gas can be reduced by lowering flue gas temperatures. This can be achieved by maintining clean heat transfer surfaces in combustion equipment, that is by removing deposits of soot and fly ash on the flue gas side of the heat transfer tubes and by removing deposits of scale on the water side of the tubes. The properties and quantities in coal are of major im portance in the desing and operation of steam generating equipment. Although bailers are often designed and equip ped to use a wide range of coals satisfactorily, no boiler installation will perform equally well with all types of coal. All coals have certain properties which place limita tion on their most advantageous use. These limitations are particularly stringent for many of the older installations. As found in seams, coal is a heterogeneous mixture of organic and inorganic materials. Not only are there large differences in the properties of coal from different seams but also of coal removed from different elevations and different locations in a signle seam. Impurities can be divided into two general classifica tions-inherent and removable. The inherent impurities are inseparably combined with the coal. The removable impuri ties are segregated and can be eliminated, by available cleaning methods, to the extent economically justified. Mineral matter is always present in raw coal and forms ash when the coal is burned. The ash-forming mineral mat ter is usually classified as either inherent or extraneous. Ash-forming material organically combined with the coal is considered as inherent mineral matter. This portion came from the chemical elements existing in the plants from which the coal was formed. Generally the inherenet mineral matter contained in coal is about 2% or less of the total ash. xv Extraneous mineral matter is ash-farming material that is foreign to the plant material from whichthe coal was for med, the bulk of this material is from detrital matter which settled into the deposit, crystalline deposite from water that penetrated into the coal through fracture cracks and clevages both during and after coal formation, or from saline deposits from water before and during formation of peat from which the coal was formed. It consists usually of blate, shale, sandstone or limestone and includes pieces ranging from microscopic size to thick layers. Sulfur is always present in raw coal in amounts rang ing from traces to as high as 8% or more. This results in the emission of sulfur oxides in the stack gases when the coal is burned. Since control of air pollution is now a national concern, some important areas already have laws or regulations prohibiting the use of fuels containing more than a certain amount of sulfur. As a consequence the demand for low-sulfur, coals has increased. There forms of sulfur are recognized as occur in coal pyritic sulfur, which sulfur is combined with iron in the farm of mineral pyrite or marcasite. Organic sulfur, which sulfur is combined with the coal substance, and sulfate sulfur, in the form of calcium or iron sulfate. Sulfate sulfur in caal as mined is usually not over 0.1% and consequently not very important. Pyritic sulfur in coal may occur in lenses, bands, veins, joints, bells, fossils or finely disseminated particles, Pyrites may vary in size from a few microns to balls several feet in diameter. The larger pieces are generally removed in cleaning teh coal. However the finely divided pyrites and organic sulfur must be considered, with inherent mineral matter, as nonremovable impurities on the basis of current techno logy and economics. The principal methods used cleaning coals are; cleaning at mine face, picking aut of impurities manually or mechanically, froth flotation and gravity con centration. The by-products of combustion are stack gases, which are present with all fossil fuels, and ash, which is pre sent in substantial quantity with coal and in lesser quantity with oil. xvi Thus stack gases contain particulate matter as uell as certain gaseous products of combubtion which produce air pollution if discharged in sufficient quantity- Stack gases may contain CD and carbon particles but, with proper operation, these can be, and normally are, largely elimina ted in boilers for electric power generation and industrial application. The problems with stack gases arise princi pally from fly ash and oxides of sulfur and nitrogen. More sulfur dioxide and nitrogen oxides, along with other combustion products, climb skyward. There they cir culate with the greta air masses that farm our weather systems. It is these venturesome travelers that become the chief contributors to acid precipitation. The pollutant molecules interact chemically with sun light, moisture, oxidants, and catalysts to change into other compounds are captured within clouds or by raindrops and snowflakes to from acid rain and snow. The remaining sulfur and nitrogen compounds sift down as gases and dry particles, awaiting the first rainstorm or dewfall to transform them into droplets of acid, which kills. aquatic life, stunts vegetation, and corrodes structures. Another effect of stack gases is greephouse. Coal burning is a major culprit in pumping carbon dioxide into the atmosphere, which, is creating a greenhouse effect. They fear a planetary warming that will change weather and agricultural patterns and melt polar ice caps enough to raise the ocean levels. In this study, fuels that characteristics and event of combustion is examined. The effects of fosilfuels that which air pollution is investigated. Especially, in winter season air pollution, to with together using fossil fuels in relationship connection is examinated. The products of combustion which SG2, CG, NO and ashso that necessary precautions are inspected. Combustion systems and required conditions are generally introduced. In our country, lignite is the most important recource for heating and energy generation. The utulizatian of lignites that in this section causes air pollution expandly, Especially, in big cities tha İstanbul, Ankara, İzmir, Erzu rum and Kayseri have complaint from air pollution. This xvii problem is discussed in press and public opinion. In this subject articles and ideas is given at suffix section. The ideal combustion is requiredfar minimum air pollu tion so that event of combustion is followed uell. In ad dition, combustion efficiency and products of combustion must be measure with automatically devices. In this experiment study, KM 9DQ3 Universal automatic stack gases measure device had used. In experiments Ağaçlı and Keşan lignites had burned, and results are showed at table and graphically. Limestone (CaCQ3) had mixed to keeping SG2 gases. Because of heat loss and slaging, using of limestone that to be noneconomic and unpractically is determined.