Entegre demir ve çelik tesislerinde enerji tasarrufu yöntemleri ve Erdemir'de ikinci kanun analizi
Energy saving methods in integrated steel plant and second law analysis in Erdemir
- Tez No: 21979
- Danışmanlar: PROF. DR. AHMET KARAKAŞ
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical 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: 262
Özet
ÖZET Bu çalışmanın ilk bölümünde, demir-çelik sektörünün ekonomideki yeri ve önemi belirtilmiş ayrıca yine bu sektörde enerjinin büyük ölçüde kullanıldığı ifade edilerek, enerji tasarrufu yöntemlerinin uygulanabilirliği hakkında bilgi verilmiştir. Ayrıca enerji kullanım verimi ikinci kanun analizine göre tanımlanarak ikinci kanun analizinin öneminden bahsedilmiştir. İkinci bölümde entegre demir ve çelik fabrikalarında nihai mamul elde edilinceye kadar geçen işlemlere enerji tasarrufu yöntemlerinin uygulanabilirliği incelenmiş ve mümkün olan enerji tasarrufu yöntemlerinden örnekler verilmiştir. Üçüncü bölümde Ereğli Demir ve Çelik Fabrikaları tanıtılmış, ayrıca serbest ekonomisi içerisinde sektörlerin ayakta durabilmeleri ve rekabet şanslarını devam ettirebilmeleri için kapasite artırma ve modernizasyon projelerini uygulamaları gerektiğinden söz edilmiştir. Çalışmalarım dördüncü bölümünde termodinamik analiz yapılan Erdemir çelik üretim birimleri ; Yüksek Fırın ve Çelikhane konvertörü geniş olarak tanıtılmıştır. Beşinci bölümde termodinamiğin ikinci yasasından bahsedilerek, kullanılabilir enerji, tersinmezik ve tersinir iş kavramları tanıtılmıştır. Altıncı bölümde ise Erdemir 2 No.lu Yüksek Fırını“Zübeyde”ve 1 No.lu Çelikhane konvertörü ayrı ayrı sistem olarak düşünülerek 1 ton sıcak maden bazında her iki sistemden ısı kayıpları hesap edilmiş daha sonra Yüksek Fırın torpido arabası ve Çelikhane konvertörü bir tek sistem gibi düşünülmüş ve seçilen her bir sistem için ikinci kanun verim değerleri ve tersinmezi iki er bulunarak bunların çalışma sıcaklıklarına göre değişimi bilgisayar programı yardımıyla hesaplanmıştır. Yedinci bölümde ise altıncı bölümde bulunan değişimler yorumlanarak enerji kullanımı bakımından kritik olan, başka bir deyişle tersinmezikleri etkileyen parametreler belirtilmiştir. Ayrıca elde edilen sonuçlara göre enerji tasarrufu yöntemlerinin Erdemir Yüksek Fırın-Çelikhane arasında uygulanması gerektiği önerilmiştir.
Özet (Çeviri)
SCMİAHY : ENERGY SAVING METB3DS IN INTEGRATED STEEL PLANT AND SECOND LAW ANALYSIS IN ERDEMİR In this presented thesis we researched into the energy saving methods in integrated steel plant and, second law of Termodynamic Analysis in main steel production units of Ereğli Iron and Steel Plants. In the first section we have analysied the iron and steel sector's effects on both economy and total energy consumption in industry. Since second law of Termodynamic Analysis gives more reliable results than first law, in this section the importance of second law has been pointed out in detail. In the second section we have studied on energy saving methods for main iron and steel production units for integrated iron and steel plant, namely ; Coke Plant, Sinter Plant, Blast Furnaces, B.O.F. Shop, Hot Mill Shop and Cold Mill Shop. Blast Furnaces are important energy consumption units of iron and steel plants. So it is adventageous to save energy in these units such as increasing the heat efficiency of Blast Furnace by using heat of blast furnace gasses. In the Blast Furnace theory Si rate in pig iron must not exceed 0,8 % because the more Si rate in pig iron will require the more oxygen in B.O.F. Shop. Coke is the main energy source in Blast Furnace, if some fuels is coinjected by coke, coke consumption in Blast Furnace may be reduced. Steel is produced by burning C, Mn, Si, P in pig iron by blowing oxygen into the furnace. Heat of furnace gasses can be used in an heat exchanger for producing steam. The other important factor which affects the heat efficiency of furnace is tap to tap time because during the tap to tap time furnace losses heat by conduction and convection through the wall and radiation from the mouth. If sublance is used, this period can be reduced the required level. Slab and ingot are taken from continuous casting or B.O.F. Shop. If their temperature is not enough, heating will be needed. By reducing travelling time of slab and ingot between B.O.F. Shop and Hot Mill Shop, heat consumption in Heating Pit may be reduced. -viii-According to above explanations we have found that, the energy saving method for a facility should be chosen by considering the its effects on the other facilities. In the third section we have given information about Ereğli Iron and Steel Factory, which is the biggest integrated iron and steel factory in Turkey, and her Capacity Improvement and Modernization Project. Nowadays Turkey is planning to be a member of Europen Community for finding a new market and for being competetive, Erdemir has started a project of investment to increase production capacity improve quality, decrease production prices and for conservation of the energy. Erdemir's Capacity Improvement and Modernization Project cost which is the biggest project after GAP project is at the first stage 820 million $, and second stage 900 million $ approximate totally 1.720 billion $. 700 million $ will be provided from the suppliers as a credit and approximately 1 billion $ will be provided from Erdemir's own sources. After finishing the CIM Project planned at the end of 1994. Grade steel and finished product capacity ofg Erdemir will be increased from 700.000 tons to 1.600.000 tons and finished product tonnages will be 3 million tons. Beside that Erdemir's increasing the capacity to supply the domestic demands and to export, is taking necessary measures such as to improve the quality, prevent the enviromental pollution, conserve the energy and decrease the production costs. In the fourth section, we have given information about Erdemir's Blast Furnaces ; Ayşe and Zübeyde and B.O.F. Shop where second law analysis had been applied. In the Blast Furnace process, iron-bearing materials (iron ore, sinter, pellets, mill scale, open-hearth or basic-oxygen- process slag, iron or steel scrap etc.), fuel (coke), and flux (lime stone and/or dolomite) are charged into the top of the furnace. Heated air (blast) and, in some instances, fuel (gas, oil or powdered coal) are blown in at the bottom. The blast air burns part of the fuel to produce heat for the chemical reaction involved and for melting the iron, while the balance of the fuel and part of the gas from the combustion remove the oxygen combined with the metal. -IX-Erdemir's B.O.F. Shop that houses the Basic Oxygen Furnaces and their auxiliaries is divided into three aisles. The main building in the centre is 150 m long by 11 m wide and 32 m high. The main building of furnace aisle is divided into five levels, namely ; Ground floor. Charging Floor, Service Floor, Weigh Lorry Floor, and the Bin Floor. The charging aisle is 215 m long by 19 m wide by 25 m high. It is divided into two levels ; Ground Floor and Charging Floor. The teeming aisle is 258 m long by 19 m wide by 25 m high. From a thermal stand point, the basic oxygen process may be regarded as an operation in which fuel, the hot metal is burned to CO, C02, Sİ02, MıO, E205 and oxides of iron by blowing 02 into the vessel. The oxideration of the elements provides more than enough heat to raise the temperature of the furnace products to the required level, and to melt the flux added. The excess of heat may be employed in a variety of ways ; some of it is lost by conduction, convection and radiation to the outside ; the remainder may be used to make melt cold scrap, or to reduce iron ore to metal. In the fifth section the second law of thermodinamics, and the principle of entropy production together with the concept of entropy are defined as based on the“exergy”, and proved that reversibility concept mentioned in traditional explanations of the second law, in fact contains the“exergy”. So this section is an original approach to the def ination of the second law and to the law itself taking the“exergy”as the starting point and giving the decrease of exergy of a system as postulate. In this section we have profited by irreversibility and availability, at the same time we were interested in proverb main consumption in thermodynamic. We now look at what they are ? There are irreversibilities present as the process takes place, as in every real process. The work crossing the control surface during the process is W.c.v and the heat transfer is Q.c.v. all of the heat transfer is with the surroundings at temperature To. We now ask the following questions ; what if this working fluid had undergone exactly the same change in state, except in a completely revesible process ? How much work would have been done in such a process ? We realize, of course, that such a process does not really exist. Any process that actually occures can do so only with some irreversibilities. Thus, we are imagining an ideal process, to which we can compare the real process. This situation is similar to our discussion of cycles that let us to develope the ideal, completely reversible carnot cycle, to which we can compare the performance of real cycles. The situation is also similar to which we compared the performance the real machines (turbines, compressors, nozzles) to idealized model process. -x-In order that heat transfer between the control volume and the surroundings may occur reversibily when there is a difference in the temperature in the control volume and the surroundings, it is necessary that this heat transfer take place through a reversible heat engine. The work output of this reversible heat engine is designated Wc. The sum of the crossing the control surface for the reversible case and work output of the reversible heat engine is called the reversible work and is designated Wrev> That is, Wr_“ = (W_”)-~, + W_ (1) 'rev. »“c.v.'rev. ”c The difference between reversible work W^^ and that done in the first case, Wc#v> when irreversible process occur is called the irreversibility, which is designated I. I - Wrev“ Wc.v. (2) Quite obviously, if real process could take place in a completely reversible manner, the irreversibility would be zero. While we could calculate the reversible work for each problem that we might consider, it is advantageous at this point to develope a general expression for the reversible work. This process was described in section 5, and for this process the first law can be written, (Qc.v>rev. +Xmİ (hi2 + Vi2 + 9Zi) = (Wc-v)rev- + ST100 (he + Ve”+ gze) + [m<> (u2 + V2“ + gzr>) - mx (ux + VI”+ gZjHç v (3) 2 7 2 Since all process are to be reversible, the heat transfer with the surroundings must also be reversible, therefore, if the temperature within the control volume is different from the surroundings, this heat transfer must take place through a reversible engine. For the reversible heat engine work, Wc we could write first law, Wc = Qq - (Qc.v)rev. M -xi-Second law : since -9a. = (-V) dT rev. (5) It follows that, Wc = To O) rev. rev. (6) m2s2“ mlsl + Z^e - ][ misj = T rev. 0 (7) On rearranging this equation, we have.2 Wrev = Xmi (hi ”T° Si +- + ^“ X11^ (he ”To se +_^? + gze)“ &*> h*> - TQ so + V2^ + 92o) 2 - m± (ux - T0S! +_vr; + gzjHc.v 2 (8) for a steady -state, steady-flow process, in rate form, Wrev ”7 »i ^i ~ To si + Vİ? + 92i5“ J »e ^e ”To se + ^ + SPfe) (9) -xii-When there is a single flow of fluid into and out of the control volume in a steady-state, steady-flow process we can write, İtev_= wte = ttH - T0 Si + Vi2 + gzj) - (hg - T0 se + Ve2 + m ** 2 2 gze) (10) What is the maximum reversible work that can be done by a system in a given state ? We developed an expression for the reversible work for a given change of state of a system. But the question that arises is, what final state will make this reversible work the maximum ? The answer to this question is that when a system is in equilibrum with the enviroment, no spontaneous change of a state will occur and system will not be capable of doing any work. Therefore, if a system in a given state undergoes a completely reversible process until it reaches a state in which it is in equilibrum with the enviroment, the maximum reversible work will have been done by the system. Let us first consider the availability associated with a steady-state, steady-flow process in Eq. (10) we noted that when we consider a single flow, wrev = (hi - T0 Si + m? + gzi) - toe - TQ se + Ve2 + 2 2 gze) (11) This reversible work will be a maximum when the mass leaving the control volume is in equilibrum with the surroundings if we designate this state in which the fluid is in equilibrum with the surroundings with subscript 0, the reversible work vail be a maximum when hg = hQ, se = s0, Ve = 0 and Zq = Zq. Designating this maximum reversible work per unit mass flow as the availability per unit mass flow, and assigning this the symbol o^, we have Y - to ~ T0 s + V2 + gz) - (ho - TQ s0 + gz0) (12) According to thermodynamic concepts and rules we have defined availability ; jZf =nj(hoJ + Ah - Tos) (13) -xi i i-For each material, which combines into steel production process, and second law efficiencies ; C - wreal hl~£0i ~ £0e (14) C I0i - S ft» In the sixth section all the calculation has been made in Ereğli Iron and Steel Factory Blast Furnace, Zubeyde and No.l B.O.F. Furnace for production of one ton of pig iron. Vfe have also calculated the heat losses for one tone pig iron from main steel production units, Blast Furnace, B.O.F. Furnace and Torpido Car and put these results into equations (14) and (15). To be able to find the changes in S^ and 63 with working temperatures, we had developed computer programmes for each steel production units, and we have found real work, reversible work, maximum work and reversibilities for the chosen steel production units by means of computer programmes. In the Blast Furnace Process we have found second law efficiencies ; %* £2 *n turn 0*31 and 0.61 and showed the change with them and and working temperatures as figures by means of a computer programs. As you see from figure 6.2 when the temperature of Blast Furnace air is raised, there is increase in second law efficiencies and decrease in irrversibility. Therefore Blast Furnace temperature is an important parameter for efficincies in Blast Furnace. As it was indicated before, hot metal is taken from Blast Furnace to B.O.F. Shop by torpido car. If torpido car travelling time is reduced, heat losses from torpido car can be reduced and it causes less oxygen consumption in B.O.F. Shop. On the other hand, above mentioned of efficiencies for B.O.F. Shop vessel are 6^ = 0.43 and £2 = 0.29. As it is showed in figure 6.11 and 6.12 efficiencies increase and irreversibility decreases when hot metal temperature is raised. As for the general system defined in the sixth section, second law efficiencies ; S^, ?3 have found 0.30 and 0.46 respectively. -xiv-In conclusion, the results obtained in this study are not satisfactorily and it shows that, between Blast Furnace and B.O.F. Shop in Ereğli Iron and Steel Factories, applying of energy saving methods is compulsory. -xv-
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