Çan ve Yatağan linyitlerinin akışkan yataklı yakıcıda elde edilen küllerinde PAH'ların analizi
Investigation of PAH in Çan ve Yatagan lignite ashes from fluidized bed combustor
- Tez No: 21819
- Danışmanlar: DOÇ. DR. HÜSNÜ ATAKÜL
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 96
Özet
ÖZET içinde yaşadığımız çevrede hem doğa, hemde insanlar tarafından kontrol edilebilen çeşitli proseslerde bilinen en büyük kanserojen kimyasallar grubunu oluşturan Polisik- lik Aromatik Hidrokarbonlar (PAH) açığa çıkmaktadır. özel likle yakma sistemleri, otomobil eksozları, kömür isletmeleri, sigara dumanı vb. kaynaklardan yayımlanan PAH' lar solunum, içme suyu ve besin zinciri yollarıyla metaboliz maya girmekte ve basta kanser olmak üzere çok çeşitli rahatsızlıklara neden olmaktadır. Bu çalışmada Çan ve Yatağan linyitlerinin Akışkan Yataklı bir yakıcıda değişik yatak malzemeleri kullanılarak, değişik akıskanlastırıcı gaz hızlarında yakılması sonu cunda oluşan ve i. ve 2. siklondan elde edilen küllerinin PAH içerikleri incelenmiştir. Bu amaçla küllere atmosferik basınçta Soxhlet ekstraksiyonu işlemi uygulanmış ve ele geçen ekstraktın aromatik f raksiyonundaki PAH kimya salları Gaz Kromotogrof isi-Kütle Spektrometresi yöntemi ile tanımlanmıştır.
Özet (Çeviri)
INVEST I BAT I ON OF PAH IN CAN AND YATAĞAN LIGNITE ASHE9 FROM FLUI DI ZED BED COMBUSTOR SUMMARY Numerous polycyclic aromatic hydrocarbons (PAHs) compounds are produced by both natural and human-cont rolled processes. The compounds constitute the most dangerous carcinogenic chemical group ever known. PAH emitted from sources such as combustion system, coal mining, car exhausts, smoking get into human body via breathing, drinking water and nutrition and cause many fatal diseases including cancer. Studies done on PAH showed that there are hundreds of alkyls, in addition to thirty main compounds, having carcinogenic effect. At the beginning of this century the existence of BenzoC a ) pyrene and its carcinogenic effect have been determined. Results of the research carried out on the combustion of fossil fuels indicated that the solid particles produced during the combustion contain some mutagenic PAH containing nitrogen and oxygen. Coal, one of the most important energy resources, constitutes almost 75-80 7, of the fossil fuels techni cally and economically feasible for mining, At pre sent, coal sources suitable for economic production is 750 billion ton equal anthracite. It is estimated that with present consumption rate, it may meet coal needs for 250 years. Coal consumption, as a primary energy resource, increases with increase in electrical/power production. This results in many environmental and health problems. Whatever systems or methods are used for coal combusti on, an important amount of gas and solid products are produced during the combustion process. The products spread out and cause different environmental and health problems. The most dangerous products are S0X, N0X, viC02 j unburned hydrocarbons and various organic compo unds (particularly polycyclic aromatic hydrocarbons). It is reported that only in the USA, 900-1400 tons Benz (a } pyrene per year is pumped to the atmosphere. PAHs produced during combustion Bre absorbed on solid particles and spread out to environment. At present, ash emitted by modern industrial processes amounts to 50000 tons per year. Design of coal combustion systems gains importance as the amount of coal used in energy production incre ases. Various researches showed that the amount and compositions of PAHs vary with types of the combustion systems. In the recent years, development of fluidized bed combustors (FBC) provide a more effective way than the conventional systems to burn low-quality coals, ha ving high amount of ash, moisture, sulfur and low calo rific value. Studies done on the FBC combustion showed that ashes produced by FBC have lower PAH containing nitrogen than that of pulverized combustion systems. The mutagenic character of ash varies with conditions such as combustion temperature, fuel /air ratio and com bustion efficiency. Lignites having 8.1 billion tons resources, is the biggest fossil fuel resource in Turkey. But major part of them is low quality coals having low calorific value high ash, moisture and sulfur contents.Additional ly, properties of the lignite vary noticeably even in the same resource. Their low specific temperatures (initi al deformation, hemispherical and fusion temperatures) and deficiency of the conventional systems make the combustion of these lignites further complex. Because it is not possible to make simple and conventional com bustion systems more efficient, fludized bed systems need to developed for a more efficient and clean bur ning of Turkish lignites. In this study, PAH contents of ashes obtained by burning of two major Turkish lignites, Can and Yatağan lignites, in a fludized bed combustor were studied. The fluidized bed used in the experiments was 0.18 cm i.d., 1 m high and made of stainless steel. It was connected to two cyclones in serial. Three types of distributor plates were used in the experiments. These were perforated distributor plate, slanted perforated distributor plate and nozzle type distributor plate. VllThe system was computer - controlled. Coal was fed into bed by using a screw feeder having adjustable feeding rate. Five Ni-Cr type thermocouples were used for tem perature measurement. They were located at, 0.01, 0.05, 0.10, 0.15 and 0.30 m away from the distributor along the bed exis. The PAH content of ashes from the cyclones were determined by applying of extraction-separation-charec- terization technique. Extraction was carried out in a 250 cc Sohxlet extractor using a toluene-Methanol mix ture with toluene/methanol ratio of 7/3. In order to determine the PAH compounds, extract obtained by soxh- let extraction was fractionated into the aliphatic, aromatic and polar fractions by column adsorption chro matography. 70-200 mesh silica gel was used as a sta tionary phase in column chromatography. Silica gel was previously dried in an oven at 200“C to remove any physically absorbed water. Adsorption column was glass tube of 0.015 m i. d. and 0.50 m high. Extract phase from Soxhlet extraction was eluated in the column by using 100 cc n^-hexane, 100 cc toluene and 100 cc met hanol respectively. PAH compounds in the aromatic fraction were determined by using a gas chromatography- mass spectrophotometer. Lignite samples were burnt in limestone and quartz sand fluidized beds at various air fluidizing velociti es. Lignite particle size was 1-2 mm and 4-5 mm, and bed materials particle size was 0.31-0.64 mm and 0.64- 1.04 mm. 1-2 mm lignites were burnt in 0.64-1.04 mm bed materials, while 4-5 mm lignite fractions were burnt in 0.31-0.64 mm bed materials in order to esta blish ”lignite-flotsam“ rich and ”lignite-jetsam" rich combustion systems. Combustion was performed at tempe ratures varying between 850 °C and 950 °C. Result obtained from ash extraction showed that extraction yield of ashes from second cyclone increased as coal particle size increased. Type of bed material and fluidizing air velocity also affected the extracti on yield of ashes. The extraction efficiency of ashes from the second cyclone was higher for limestone-bed than quartz sand-bed. The extraction yield of the se cond cyclone ashes obtained by 4-5 rom Yatağan lignite- quartz sand combustion system did not change conside rably with increase of air velocity. However, yield of the second cyclone increased with increase in the air- velocity for 1-2 mm Yatağan lignite-quartz sand vmvelocity for 1-2 mm Yatağan lignite-quartz sand combus tion system. The similar results were obtained for i-2 mm Can lignite-quartz sand systems. The extraction yield of the second cyclone also did not change with increas in the air velocity for the systems in which 4- 5 mm Can lignite burnt in quartz sand bed, while for the limestone bed it increased with increase of the air velocity. Result of chromatographic analysis of both lignite ashes showed that the major part of organic structure of ashes is consisted of polar compounds, Nearly 50 7. of extract fraction was polar compounds. Aliphatic fraction was the largest fraction in the extract phase. Aromatic fraction was of the lowest amount for all experiments. Analysis of PAH compounds in the aromatic fraction was carried out by a BC-MS. A capillary separation column lined with SP biphenyl type material of 25 m # 0.50 mm i.d. size was used in the GC- MS analysis. Table 1 shows the number of the PAH which is iden tified in cyclone's ashes. BC-MS analysis showed that coal ashes from both cyclones did not contain any dangerous active carcino genic compounds. However, compounds such as pbenanth- rene, anthracene-, flouranthene and pyrene which, accor ding to the preliminary studies, have carcinorogeine effect but do not show any activity in short term tests, were presented in the aromatic fraction. These compounds were determined in all experimental conditi ons. ÎX(U X 4J XI IB
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