Göynük bitümlü şistlerinin akışkan yatakta su buharı pirolizi
Steam pyrolysis of Göynük oil shales in a fluidised bed
- Tez No: 39234
- Danışmanlar: PROF.DR. EKREM EKİNCİ
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 62
Özet
ÖZET Petrol kaynaklarının az olması ve giderek de azalıyor olması insanlığı, hem enerji kaynağı olarak hem de hammadde olarak kullanılmak amacıyla petrol eşdeğeri sentetik maddelerin üretimi için çeşitli araştırmalara teşvik etmektedir. Türkiye'nin petrol rezervleri oldukça kısıtlı olmasına rağmen taşkömürü, linyit ve bitümlü şist rezervleri oldukça geniştir. Bu da Türkiye'yi, sentetik pertol üretimi açısından bu daha geniş kaynaklarını değerlendirme çalışmalarına itmektedir. Piroliz, organik yapı bakımından zengin maddelerden petrol türevi sıvı ve gaz üretiminde kullanılan metotlardandır. Bu çalışmada, (Bolu) Göynük A ve B şistlerinin akışkan yatak kullanılarak değişik şartlarda ve ortamlarda pirolizi yapılarak sıvı ürün verimleri incelenmiştir. Deneylerde 5°C/dakika ısıtma hızıyla 550°C ye çıkılmış bu sıcaklıkta 30 dakika beklenmiştir. De neylerde gaz debisi akışkanlaşma noktası altında, akışkanlaşma noktasında ve akışkanlaşma noktası üzerinde olacak şekilde ayarlanmıştır. Gerek azot gazının kullanıldığı deneylerde, gerekse su buharının kullanıldığı deneylerde akışkanlaştırıcı gaz debisinin artışıyla birlikte sıvı ürün verimleri de artmıştır. Azot gazının akışkanlaştırmada kullanıldığı deneyler de normal atmosfer şartlarında elde edilen sıvı ürün verimlerine nazaran Göynük A bitümlü şisti için %61 ve Göynük B bitümlü şisti için % 56'lık bir verim artışı gözlenmiştir. Kızgın su buharının kullanıldığı deneylerde ise Göynük A bitümlü şisti için %91 ve B bitümlü şisti için % 134'lük verim artışları kaydedilmiştir. Akışkanlaşma kalitesinin iyi olmadığı, özellikle düşük akışkanlaştırma hızlarında sıvı ürün verimlerinin oldukça düşük olduğu gözlenmiştir. Akış kan yatak geometrisinin dolayısıyla iyi bir akışkanlaşmanın piroliz veriminde artış sağlayabileceği gösterilmiştir.
Özet (Çeviri)
STEAM PYROLYSIS OF GÖYNÜK OIL SHALES İN A FLUIDISED BED SUMMARY All kinds of sediments involve vorying amounts of organic matter. Although it is present in high concentrations in coal and peat deposits and accumulations of petroleum, natural gas and tar sands, much larger quantities occur as finely dispersed discrete organic particles in clastic sediments. Such sediments containing high concentration of organic metter are refered to as oil shales. Oil shales were formed in ancient shallow lakes by the slow deposition of aquatic organisms, spors, pollen grains and vegetable matter such as shreads of wood, bark and leaves, along with inorganic matter intimately mingled. The inorganic material consists mainly of clay with fine sand, calcite, dolamite and iron compounds. As the lakes dried out, the deposits became compacted and over geoligic time were transformed into impermeable rocks. Oil from oil shale is often referred to as a“synthetic”fuel, but the organic matter in oil shale is a naturally occurring fossil fuel. In fact oil shale's organic matter is the world's largest supply of fossil fuel. Source rocks are classified in terms of the amount and type of organic matter. Two main approaches are used for characterizing the organic components in sedimentary rocks. Organic petrography used optical methods to identify and semiquantify the individual organic maturation. Organic geochemistry uses elemental and physico-chemical analyses to determine the composition and alteration of organic compounds and macerals in sediments. The total global proven, probable and possible crude oil reserves have been estimated at 1.8 x 1012 barrels or 257 x 109 tonnes, but shale oil resources may amount to 400 x 109 tonnes. Of this about 30 x 109 tonnes of shale oil are recoverable with current technology. The USA is thought to contain 700x1 03 barrels of currently recoverable shale al while in Green VIRiver Shales of Colorado, total reserves of shale oil are estimated at 1500 x 109 barrels. With current knowledge, the USA is believed to have the largest reserves, amountingto 293x1 09 tonnes, while South America is thought to contain reserves of 124 x 109 tonnes of oil shale, africa and Asia contain an estimated 15.5 x 109 tonnes and 16.2 x 109 tonnes respectively. Whilst European oil shale reserves are calculated at 1 1.8 x 109 tonnes. Oil shales comprise the second largest solid fuel reserves in Turkey after lignites, with reserves totalling approximately 5 x 109 tonnes. The largest reserve Göynük, is estimated to have 1 x 109 tonnes and seyitömer 0.5x1 09 tonnes. These two oil shales are previously studied in the Chemical Engineering department of İTÜ and found that the 900°C Heinze retorted shale oil yield were 10.1 % and 26.6% respectively for Seyitömer and Göynük oil shales. The technology of oil shale and lignite retorting is based upon pyrolysis of the rock at a temperature around 500°C. Various bonds in the kerogen macromolecule are broken, liberating liquid and gaseous hydrocarbons, and also nitrogen, sulphur and oxygen compounds. However, due to shale quickly reaching a high temperature, chemical transformations and their kinetics are somewhat different from those leading to petroleum formation during catagenesis over prolonged periods of geological time. For example, shale oil contation higher proportions of olefins which are not found in petroleum. The need to evaluate the chemical nature of petroleums, coals, oil shales and tar sands when considering their utilization, spesification and formation is self evident. The most important methods for the detailed chemical analysis of solid fuels, their extractable organic matter and pyrolysis tars are elemental analysis, Infra-red (IR), nuclear magnetic resonance (NMR), adsorbtion (Liquid) chromotography and gas chromotography (GC) often in conjuction with mass spectrometry. The studies so far showed potential for economic oil production especially from Göynük reserve. For the purpose of increasing the yield, new techniques are employed on the Heinze retort and fluidised beds. They included: a) - Controlling the pyrolysis atmosphere with nitrogen atmosphere or carrying out at normal atmosphere. b) - Pyrolysing mixtures of oil shale and lignite at different proportions. c) - Pyrolysing with steam. VIId) - Hydropyrolysing and catalytic hydropyrolysing. Two kinds of oil shale and a lignite are used in this study. These samples were from Göynük fields of Bolu. Table 1 Short analyses of this samples are shown below. Oil shales are first pyrolysed in a Heinze Retort without any sweep gas. The retort was heated at a speed of 5°C / minute to 550°C and was weited for 30 minutes at this temperature. The tar yields are reached at Heinze Retort is 31% for A oil shale and 22% for B oil shale in dry ash free (daf%) basis. When the same oil shales are pyrolysed at a fluidised bed by using nitrogen as a fluidising medium the yields of oil shale were rised to 50 % and the yields of B oil shale were rised to 34 % at a gas speed of 5.85 cm/s. After, the pyrolysis of those oil shales using water Vapour as a fluidising medium the yields were rised once more as 59.5 % for A oil shales and 51.7 % for B oil shale at maximum water vapour speeds. The same heating program with the Heinze retort is applied to the fluidising beds. There has been increases of tar yields at increasing fludising gas velocities in the same reactors and same environments. Two different fluidising beds are used in this study. One is made of quartz and the other is made of stainless steel. The quartz fluidised bed has a perforated plate of sinterised quartz and the other fluidised bed has a stainless steel single perforated plate. Because of the different perforated plates the fluidised bed performances are different so that the different tar and char yields are reached at the same fluidising gas velocities. The sinterised perforated plate ensure better fluidising regimes than single perforated plate at low gas velocities. Because of this the tar yields rise quickly at quartz fluidised bed. But at high velocities of fluidising gases the two fluidising beds are reached to the same tar yields. VIIITable 2 The results of expriments at different pyrölysing environment is shown below. The results are at dry ash free basis. In this study copyrolysis of oil shales and lignites in a fludised bed using water vapour as fluidising medium is examined. On copyrolysis of Göynük A oil shale and Göynük lignite a tar yield of 31 % has been reached and copyrolysis of Göynük B oil shale and Göynük lignite a tar yield of 28 % has been reached which are higher yields than the theoreticaly calculated yields. This effect is a result of synergic effect. Table 3 Copyrolysis results are shown below. IXOil shale A and lignite copyrolysing tar yield is found to be 17% higher than theoretical yield and oil shale B and lignite copyrolysing tar yield is found to be13% higher than theoretical yield. The improvement in the oil yield for steam is attributed to a number of factors. Some of these include: i) steam preventing some of the char forming and cracking reactions. ii) Water vapour helping to consende smaller molecular weight hydrocarbons. iii) Steam has been found to improve the porosity of the structure immencely to help release the volatile matter and, iv) Steam is beleived to be involved in hydrogen transfer reactions to stabilise some of the redicals otherwise recondense to char. The improvements observed in copyrolysis in also explained in terms of preventition of some char forming reactions and hydrogen transfer. For this reoson the changes brought along by steam and copyrolysis result in similar product classification changes. The present state of oil in the world market seems to be settled and running at low prices. However the forecasts for the future of crude oil in the world is not optimistic. It is claimed that the crude oil reserves in Middle East will diminish at a slower rate than the other resources. This will cause the bargaining power of Middle Eastern countries to increase. It is very unlikly that the world economies would be able to absorbe steep petroleum price increases especially if it happens in manner which may be formed as“third energy crisis”. In case of an energy crisis Turkey will be one the greatest suffers since her dependance on important crude is at a considerable level. To overcome such a crisis Turkey may plan to provide her petrol from lignites, asphaltites and oil shale. The lignites need comperativly higher techonlogies resource have high sulphur contents and have lover liguid yields. Therefore the 5 billion tonnes of Turkish oil shales would be the most realistic alternative for synthetic fuel processes. The finding of this study should be applied to pilot and industriel scale as soon as possible. It is also worth pointing out that the oil shales that are mined as a part of lignite utilisation when used together with oil shales will provide great adventage.
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