104 TERMOTEHNICA 1/2011 ANALYSIS OF THE COGENERATION IMPLEMENTATION POTENTIAL INTO AN EXISTING SATURATED STEAM BOILER INDUSTRIAL PLANT Paula UNGURESAN, Florin BODE, Mugur BALAN, Andrei CECLAN TECHNICAL UNIVERSITY OF CLUJ-NAPOCA, Romania. Rezumat. Lucrarea prezintă o analiză tehnico-economică referitoare la potenţialul de implementare a unei instalaţii de cogenerare cu turbină cu abur, utilizând un cazan de abur existent în industria petrolieră.În acest sens s-a avut în vedere utilizarea unei turbine cu abur în condensaţie, în două regimuri posibile de operare: cu şi fără prize de presiune, utilizând debitul de abur produs de cazan. În realizarea studiului s-a utilizat programul Engineering Equation Solver (EES), pentru diferite temperaturi de supraîncălzire a aburului (Regim I) şi pentru diferite debite de abur prelevate din turbină (Regim II). Principala concluzie a studiului întreprins este că nu se justifică investiţia în echipamentele aferente unei instalaţii cogenerative cu turbină cu abur, la presiunea de lucru din cazan de 6 bar deoarece perioada de amortizare a investiţiei este mare. Cuvinte cheie: cogenerare, cazan de abur, turbină cu abur, analiză tehnico-economică. Abstract. The paper presents a techno-economical analysis concerning the potential implementation of a steam turbine cogeneration plant into an existing saturated steam boiler plant from the oil industry. It was analyzed the use of a condensing steam turbine in two possible operating conditions: with and without extractions, using the production of an existing saturated steam boiler. The study was carried out using the Engineering Equaton Solver (EES) software, for different superheat conditions (Regime I) and for different steam flow extractions (Regime II). The plant performances were determined and a comprehensive economic calculation was performed for the two operating conditions. The main conclusion of the study was that due to the low boiler operating pressure of only 6 bar the investment into cogeneration equipment is not justified, because of the too long payback period. Keywords: cogeneration, steam boiler, steam turbine, techno-economical analysis. 1. INTRODUCTION The paper deals with the possibility of implementing a steam turbine cogeneration plant into an existing steam boiler in the oil industry. Cogeneration is the simultaneous production of heat and power from the same primary energy source in a single system/unit. The two types of steam turbines most widely used are the back pressure and the extraction-condensing one. The choice between backpressure turbine and extraction-condensing turbine depends mainly on the quantities of power and heat, quality of heat, and economic factors [1,2]. The existing steam boiler, produced by Sieta Cluj-Napoca, of VAP 3D type, has the following nominal parameters: - Thermal load at 100°C: 3942 kW; - Nominal pressure: 8 bar; - Nominal steam flow rate : 6t/h; - Nominal temperature: 175°C; - Maximum working pressure: 8 bar. 2. FUNCTIONAL DESCRIPTION OF A COGENERATION PLANT AND OF POSSIBLE OPERATION CONDITIONS The cogeneration potential study has been done under the conditions determined by the measured parameters of the boiler steam output: steam pressure 6 bars and the steam mass flow rate: 1.212 kg/s. Because the plant comprises two steam boilers which never work simultaneously, one can support the whole technological process, while the second may be used to produce electricity through a Claussius-Rankine cycle. The most appropriate technological solution for the analised plant is the option of cogeneration with extractions condensing steam turbine. As the available pressure at the steam turbine inlet is very low, expansion in the steam turbine above atmosferic pressure would represent a low potential for producing mechanical power. The schematic diagram of a condensing steam turbine cogeneration plant and thermodynamic