BİYOGAZ MOTORU ATIK ISISININ REKÜPERATÖRLÜ ORGANİK RANKİNE ÇEVRİMİ İLE GERİ KAZANIMINDA İŞ AKIŞKANI SEÇİMİ VE OPTİMİZASYONU

Öz

Bu çalışmada, birincil enerji kaynağını daha verimli kullanmak amacıyla biyogaz motoruna entegrasyonu önerilen reküperatifli bir Organik Rankine Çevrimi (ORC) sistemi analiz edilmektedir. İncelenen motor, Zonguldak katı atık sahasından toplanan biyogazla çalışan 1498 kW gücündeki bir gaz motorudur. Motorun 410 °C sıcaklığındaki egzoz gazıyla salınan ısıl enerji potansiyelinin tamamını en yüksek verimle elektriğe dönüştürebilecek ORC sistemi için en uygun iş akışkanı belirlenmekte ve optimum tasarım parametreleri ortaya konmaktadır. Önerilen reküperatifli ORC sisteminde ısı transferi aracı akışkanı olarak Therminol 66 kullanılmıştır. İş akışkanı adayı olarak doğal hidrokarbonlardan oluşan dört farklı organik iş akışkanı (n-Pentane, Toluene, n-Decane ve n-Dodecane) belirlenmiştir. Evaporatör girişindeki sıkışma noktası sıcaklığı 10 °C kabul edilerek, Termodinamiğin II. Yasasına ve uygulamada gerçekleştirilebilir işletme koşullarına uygun kızdırma sıcaklıkları tespit edilmiştir. Kızdırma sıcaklığı değişiminin her bir organik akışkan üzerindeki etkisi parametrik olarak incelenmiş ve optimum kızdırma sıcaklıkları bulunmuştur. Yapılan hesaplamalar, biyogaz motorunun atık ısı potansiyelinin 621,4 kW olduğunu ve bu potansiyelin optimum kızdırma sıcaklıklarında n-Pentane, Toluene, n-Decane ve nDodecane iş akışkanları için sırasıyla 120,3 kW, 125,8 kW, 139,5 kW ve 138,2 kW net elektrik üretimine dönüştürülebileceğini göstermiştir. En uygun iş akışkanı olarak termodinamik açıdan n-Decane, uygulamada işletme kolaylığı açısından Toluene olduğu belirlenmiştir.

Anahtar Kelimeler

• Biyogaz Motoru
• Reküperatif Organik Rankine Çevrimi
• Atık Isı Geri Kazanımı

Working Fluid Selection and Optimization in a Recuperative Organic Rankine Cycle for Biogas Engine Waste Heat Recovery

Öz

A recuperative Organic Rankine Cycle (ORC) is proposed and analyzed to recover waste heat of biogas engine. The engine power is 1498 kW and operates on biogas collected from the Zonguldak municipal solid waste landfill, and exhaust gases temperature is 410 °C. Therminol 66 is used as heat transfer fluid. Four working fluids based on natural hydrocarbons (n-pentane, toluene, n-decane and ndodecane) are evaluated as candidates. The pinch-point temperature at evaporator inlet is fixed at 10 °C, and superheating temperatures that satisfy the second law of thermodynamics and are compatible with realistic operating conditions are determined. The effect of superheating temperature on cycle performance is investigated parametrically, and the corresponding optimal superheating temperatures are obtained. The results indicate that the engine has a waste heat potential of 621.4 kW, which can be converted into 120.3 kW, 125.8 kW, 139.5 kW and 138.2 kW of net electrical power for n-pentane, toluene, n-decane and ndodecane, respectively, at the optimum conditions. Overall, n-decane is identified as the most favorable working fluid from a thermodynamic standpoint, while toluene offers advantages in terms of operational practicality. 

Anahtar Kelimeler

• Biogas Engine
• Recuperative Organic Rankine Cycle
• Waste Heat Recovery

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