Kojenerasyon teknolojisi ve kombine çevrim santralinde çalışma şartlarının belirlenmesi /
Yazar: AHMET SÖNMEZ
Danışman: YRD. DOÇ. DR. SEYHAN UYGUR
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Enerji Bilim Dalı
Derece: Yüksek Lisans, 1998
Konu: Makine Mühendisliği = Mechanical Engineering
Dizin: Gaz türbini = Gas turbine ; Gazlı motorlar = Gas motors ; Kojenerasyon = Cogeneration ; Kombine çevrim santralleri = Combine cycle plants

Özet:
ÖZET Kojenerasyon hakkında tanımlamalar ve bazı bilgi ve karşılaştırmalarla başlayan ilk bölümde; bileşik ısı güç tanımı, faydalı olduğu sektörler ve ısı geri kazanım şekilleri, gaz motorları ile gaz türbinleri arasındaki temel farklar, kullanılan yakıt seçeneklerinin kıyaslanmasına yer verilmiştir. ikinci bölümde kombine çevrim santralinin tanıtımı, çevrim elemanlarının termodinamik ve çevrimin ekonomik analizleri yapılmıştır. Bir sonraki adım olarak çevrimin birinci kanuna göre termodinamik optimizasyonu yapılarak optimum sıkıştırma oranı elde edilmiştir. Üçüncü bölümde ikinci kanuna girilerek, elemanların her biri için ikinci kanun verimleri ve tersinmezlik hesapları yapılmıştır. Kayıp ekserji, kimyasal ekserji gibi kavramlar tanımlanmıştır. Bu bilgiler ışığında bir örnek çalışma için yapılan bilgisayar programı sayesinde çalışma şartları tespit edilmiş, ikinci kanun ve tersinmezlikler bir tablo halinde sunulmuştur. Bu programlamaya ait algoritma ve hesap prosedürü anlatılmaya çalışılmıştır. Ayrıca Ek.l'de verilen formüller ile referans [1]'de karşılaşılabilecek eşitlikler için bir ön bilgi oluşturulmaya çalışılmıştır. Sonuç olarak ısıl ihtiyaç tespitinin doğru belirlenmesinin önemi eğrilerle açıklanmaya çalışılmıştır. Ülkemize kojenerasyonun elektrik üretim öncelikli girmesi bu konunun yeterli ehemmiyet görmediği izlenimini uyandırmaktadır. Batılı ülkelerdeki örnekleri gibi hem ısı, hem elektrik açısından en uygun santrallerin seçilebilmesi çok daha faydalı olacaktır. IX

Abstract:
SUMMARY In general, cogeneration is the production of more than one useful form of energy (such as process heat and electrical power) from the same energy source. In this study's first chapter, cogeneration is described by the questions of what the cogeneration is, what kind of fuels can be used, which drivers are used, what these drivers' advantages or disadvantages are, which heat recovery options we have on cogeneration etc. The various descriptions of gas power cycles and vapor power cycles deal with systems for which the sole purpose is electric power production.lt must be recognized that there are industrial and commercial situations where thermal energy is also required. For example, a power plant on a collage campus may provide steam or hot water for heating buildings as well as for electric power. Consider also the following seven major energy-intensive industries: Chemicals, oil refining, steel making, food processing, pulp and paper, ceramic and textile. In these industries, thermal energy requirement is very high besides electric power. In this kind of applications where cogeneration is used, the cost of energy is reduced by about 50%. Basically two different type of drivers are used to produce electricity on thermal power plants. Gas or heavy fuel engines and gas turbines. The significant diffrence of these two engines is, gas engines have a greater electrical efficiency where gas turbines have more heat power output. Above 2 or 3 MW electrical power demand, this difference is one of the most important point that is the application a gas engine or a gas turbine application. There are several heat recovery chances such as; steam or hot water raising, producing extra electrical power by waste heat or direct driying by exhaust gas. Producing chiller water by absorption cooling systems can be another choice. When we come to fuels, we can use natural gas, propane, diesel, heavy fuel oil or landfill gas on gas and heavy fuel engines. On gas turbines, LPG, naphta, naturel gas and diesel can be burnt. Fuel comparision of cent/kWh basis can be seen in this study. In today's new world order, everybody knows the importance of producing goods less expensively with a high quality. On energy intensive industries, investors become a more competitive situation by producing their energy with modern cogeneration power plants.In the second section, a combined cycle is described. 5 AIR AC GT PT REC. EXHAUST ±r cc fueL HRSG -V\ Electrical Power 0 ST CONDENSER Electrical Power steam to process from process Brayton and Rankine Cycles are together on a combined cycle. A modified Brayton Cycle Gas Turbine, consisting of air compressor(AC), combustion chamber (CC), recuparator(R), gas turbine(GT), and power turbine(PT) is used with the turbine exhaust gas going to a heat recovery steam generator(HRSG) to generate superheated steam. The superheated steam is used in a standart steam cycle, which consists of turbine(ST), condenser(C), pump(P).The gas leaves the HRSG to the stack. That exhaust gas is used to preheat compressed gas at (R). Both power and steam turbines generate electricity. Also thermodynamic analysis of this cycle is given on this section. T-s diagram of Brayton and Rankine Cycle is shown as ideal and real cycles. For each component of this cycle, turbines, compressor, condenser, recuparator, combustion chamber, heat recovery steam generator, XIpump, equations related to the first law of thermodaynamics was given. Compression ratio of the compressor is a very important value on this kind of studies. This is why it is also calculated in this section. After giving the performance equations of a combined cycle, the optimum compression ratio is calculated by making the heat efficiency of the cycle maximize according to the first law of thermodynamics: T4 T4 (1 - %ec ) ( 1 ) (- )r\T ( 2Tlrec - 1 ) T1 T, a = ( + ) cp * ^Icomp TJconrip b = T4 2(- hT(1-2Tirec) T, Tlcomp T4 c = (- )m(2Tlrec-1) T4 T4 T, nT(T)(1 -Tlrec) d ) + 1 1 ' 1 T|comp In the third chapter, some explanation is made about the second law of thermodynamics. Availability and irreversibility was described and formulized. In the next step, second law efficiency, availability and irreversibility rates of each equipment was formulized. Chapter four is a case study section of the thesis. A plant description was made in this chapter. Given, unknown and required values are written on this section. In addition to this, computer program procedure is explained. How enthalpy, entropy, temperature values of the steam cycle side are found by using some complex formulas. Computer program algorithm is shown in the last page of this summary. XllOn the last chapter, all solutions are given by different tables. These are temperature, pressure, entalpy, entropy values, second law efficiencies, irreversibilities and cycle thermal and fuel utilization efficiency. On the last figures, it is seen that availabilities of condenser, HRSG, compressor and combustor is more sensitive to changes of heat requirement than electrical power. Therefore, before making this kind of application, main purpose should not be only electrical power production but also useful heat usage. The more heat power usage, the higher total efficiency. XlllCOMPUTER PROGRAMME ALGORITHM INPUT ASSUME TÜRBİNE INPUT TEM.,TC STEAM TURBINE THERMODYNAMIC ANALYSIS -Ne- ASSUME EXHAUST TEMPERATUREJs ASSUME GAS TÜRBİNE INPUT TEMPERATURE,T4 GAS TURBINE CYCLE THERMODYNAMIC ANALYSIS Tc=Tc+1 K T4 HT4+1K T6=T 3+1 XIV