Kömür Neminin Verim Ve Emisyonlara Etkisi

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Tarih
1998
Yazarlar
Doğan, Erhan Şükrü
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Özet
Bu çalışmada, deneysel verilerin ışığında, kömür neminin yanmaya ve emisyonlara olan etkisinin bir değerlendirmesi yapılmıştır. Doğal nem içerikli kömürlerde, nem oranı %20 ile %30 arasında olduğu zaman, iç yapıdaki su kendisini aşın bir basmçla dışarıya atmak istemektedir. Bu basınç özellikle uçucu maddelerin çıkışı aşamasında, kömürün parçalanarak daha iyi yanmasına, CO emisyonlarının azalmasına, NOx emisyonlarının, verimin ve iletkenliğin artmasına neden olmaktadır. %30 ile %35 arası doğal nem içerikli kömürlerde ise, iç yapıdaki su herhangi bir parçalanma ile değilde, difuzyon ile kömürün bünyesini terk ettiği için, CO emisyonları artmakta, NOx emisyonları, iletkenlik ve verim azalmaktadır. Suni nemlendirme ile nem oranı artırılmış kömürlerde ise, nem, katalitik bir etki yaparak CO emisyonlarmı azaltmakta, yatak sıcaklığını ve dolayısı ile NOx emisyonlarını düşürmektedir. Ayrıca, suni nemlendirme ile nem oranı %3 civarında artırılmış kömürlerde, verim ve alev cephesi hızları artmakta, %3 oranının üzerine çıkılması durumunda ise, bu parametreler tekrar azalmaktadır.
Energy is one of the most important input in industry and in everyday life. Due to the population increase, improvement of technology and living standards energy consumption increases day by day. Petroleum, natural gas and coal have been used for the purpose of producing energy. Expending high amount of energy caused a reduction in the reserves. This let an increase in the prices of petroleum. The interest in the use of coal as a largely available alternative fuel was stimulated by the oil crisis situation of the early seventies. After the oil crisis in early 70's, producing energy from coal has gained importance again. Nearly 20 percent of total energy consumption in Turkey is met by combustion of lignite. The prevalent characteristics of Turkish lignite are high volatile matter, moisture, ash, and sulfur content and low calorific value. The accurate determination of moisture in coal of various ranks has long been a subject of discussion and investigation. As has been pointed out in the reference, one of the major difficulties in assigning absolute merit to a particular procedure is the multiplicity of conditions under which water exists in coal and the difficulties involved in optioning sharp separation and distinction among these conditions. As stated by Gauger water recoverable from coal is obtained from the following source: 1 - Decomposition of organic molecules (Sometimes called combined water) 2 - Surface adsorbed water 3 - Capillary condensed water 4 - Dissolved water 5 - Water of hydration of inorganic constituents of the coal Brown further refers to: 1 - Free or adherent moisture (essentially surface adsorbed) possessing the physical properties of ordinary water. 2 - Physically bound or inherent moisture of vapor pressure lowered by the small diameter of the pores of the coal structure in which it is absorbed. X1U 3 - Chemically bound water of hydration or combined water. Moisture in the structure of coal is more important, from angle of chemical and physical properties of coal and also using of the coal. As a matter of fact, volatile matter, ash, constant carbon and moisture is parameter characterizing coal, from angle of short analysis. While carbonizing degree decrease, amount of moisture in the structure of coal increase and great part of the structure of some new coals take form water. For example; in Turkey, Czechoslovakia, Poland, Hungary, Bulgaria, Spain, German and USA there are some different low quality coal that their original moisture content change sequencely between these values, %10 - 55, %6 - 55, %9 - 55, %19- 48, %14- 62, %13 - 24, %48 -63 and %10 - 42. Therefore, from thecnologic angle, both drying operation of coal and studying of mixtured coal with water is gaining significance. In German, in using condition of coal having high portion of moisture, far from source, to decrease transport expense and increase calorific quality, drying operation of coal is gaining importance. 2 million tons coal have been dried by using this study for 20 years. Moisture influence the coal chemically, physically and economically. Existing water in the coal can influence reactivity of coal, gas mechanism, drying, exit of volatile matter, temperature of catching fire, crumbling tendency, transport economy and another properties of coal. In 1995 - 1996 winter the moisture content of coals that will be used in Istanbul is determined 15% and with a tolerance amount 18% excepted. If the level is above 18% depending on the burning system combustion efficiency is effected negatively and the role in air pollution possibility increases. Because with increasing moisture content we have to use more coal to be able to have the same amount of energy. Beside those while transporting the coal more vehicles and more fuel will be used. And SOx, NOx and other emissions will increase. But these are no experimental results that will support the idea of effect of moisture in air pollution. This topic should be exalted in detail and must be experimented in laboratories. We have seen that there are no experimental results that will support the idea of the effect of moisture in environmental pollution and this topic is not mentioned in literature. To have a certain idea and to be able to take precautions this idea should be supported by experimental data in literature. In this study we had planned to make experiments in a stove and investigate the effect of moisture in combustion. In installation of experiment: Stand having base, side and back signboard is put on a balance weighing the least 50gr. After that the empty stove is put on the stand and funnel connections are done. For measurements and gas analysis, to take sample, surgeon's probes are attached funnel connection near the stove. Moreover to measure inner temperature of the stove, 4 thermo elements are put 4 different points of the stove. In this experimental study, three different type of coal were used. Moisture content of XIV these coal were natural and artificial. To prepare artificial moisture content coal for experiments: Appropriate size of natural moisture content coal are selected and put in buckets Which is full with water. After that coal are waited enough time in this situation and taken out buckets. Then taken out coal are put in plastic bag and waited a week. After all these process, coal have artificial moisture in its structure. After putting coal in the stove, to prevent volatile matter going out not burn, coal is lighted upper part of the stove. After that one time in ten minutes, total mass of coal (kg), temperature of funnel gas (°C), pressure of funnel gas (Pa), CO2 (%), NOx (ppm), C>2(%), coefficient of excess air, CO (ppm) and, at 4 different points, inner temperature of the stove are measured. In this study, moisture content of used coal is shown at the below. After finishing experiments, tables were prepared and graphs were drawn between time and CO, O2, CO2, NOx, efficiency, pressure of funnel gas, temperature of funnel gas and inner temperature of the stove. When graphs between time and CO are examined: It is seen that all of the graphs show the typical similarity. At the beginning of the graphs, in the course of the time, high emission of CO decrease and have stationary values; however, at the end of the graphs, emission of CO increase. To learn effect of moisture in emission of CO: Arithmetical averages of emission of CO were calculated and the results were shown at the below. XV When graphs between time and O2 are examined: The same characteristic variations are seen, like graphs between time and emission of CO. Firstly, values of O2 decrease and then increase until end of the experiments. To learn effect of moisture onC^: Arithmetical averages of funnel temperature and values of O2 were calculated and the results were shown at the below. When graphs between time and emission of NOx are examined: At the beginning of the experiments, emission of NOx have low values and in the course of time, emission of NOx increase because of increasing inner temperature of the stove; however at the end of the experiments, inner temperature of the stove decrease. To learn effect of moisture in emissions of NOx : Approximate curves were made up graphs between time and emission of NOx. After that maximum values of emission of NOx were established and showed at the below together with maximum inner temperature of the stove. When graphs between time and inner temperature of the stove are examined: It is seen that front flame reach firstly thermo element of number 4 upper part of the stove and seqencely number 3, 2 and 1. It is seen that, graphs of inner temperature of the stove have two peak points. First peak point take form because of combustion of volatile matter; however, second peak point take form because of combustion of carbon. After approximate curves were made up graphs between inner temperature of the stove and time, distance between thermo elements were divided into time and XVI calculated speed of front flame. To compare speed of front flame with each other, graphs were drawn. When graphs between time and efficiency are examined: At the beginning of the graphs, in the course of time, low values of efficiency increase and, reach maximum values; however at the end of the graphs, these values decrease. At the below, maximum values of efficiency are shown. General results of this study were written at the below. 1 - If coal have artificial moisture content in its structure, moisture decrease inner temperature of the stove, emission of NOx, funnel temperature, funnel pressure, emission of CO2 and emission of CO. 2 - If coal have three percent of artificial moisture content in its structure, moisture increase speed of front flame and efficiency, because of catalytic effect of moisture on combustion; however, if coal have more than three percent of artificial moisture content in its structure, moisture decrease speed of front flame and efficiency, because of losing catalytic effect of moisture on combustion. 3 - If coal have natural moisture content in its structure between %20 and %30, emission of CO2, efficiency, emission of NOX) inner temperature of the stove and speed of front flame have maximum values; however, emission of CO have minimum values. Because moisture want to get off structure of coal by applying excessive pressure, structure is broken into pieces and combustion get better. On the other hand, if coal have more than %30 natural moisture content in its structure, moisture get off structure by diffusion and combustion get worse.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1998
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998
Anahtar kelimeler
Emisyon, Nem, Emission, Moisture
Alıntı