تحليل خرابي و ديناميك سيالات محاسباتي لوله هاي سوپرهيتر پلاتن در يك نيروگاه 320 مگاواتي براي ارائه ي طرح چيدمان بهترين جايگزين

FAILURE an‎d COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF PLATEN SUPERHEATER TUBES IN A 320 MW POWER PLANT TO PROVIDE AN OPTIMAL LAYOUT DESIGN

بويلرها از مهم ترين اجزاي نيروگاه ها هستند. لوله هاي سوپرهيتر در بويلرها نقشي اساسي دارند. با توجه به شرايط كاري لوله هاي سوپرهيتر، معمولا بيشتر خرابي ها از اين قسمت گزارش مي شود. در نيروگاه مورد مطالعه، بيشتر خرابي ها در خم انتهايي سوپرهيتر پلاتن اتفاق افتاده است. هدف اين بررسي يافتن علت خرابي است. سپس راه حل هاي ممكن براي حل اين مشكل بررسي شد. با ملاحظات علت خرابي و مزايا و معايب اين روش ها و نيز با توجه به نوع خرابي، روش مناسب انتخاب مي شود كه بر اساس روش گزينش شده و انجام محاسبات لازم، طرح هاي پيشنهادي براي جايگزيني طرح فعلي سوپرهيتر پلاتن نيروگاه 320 مگاواتي بندرعباس ارايه شد. اين طرح ها در مقايسه با طرح فعلي نيروگاه اعتبارسنجي مي شود. شرط پذيرش طرح پيشنهادي، مساوي بودن طول كل لوله ها در طرح اوليه و طرح پيشنهادي است. براي انتخاب بهترين طرح، طرح هاي پيشنهادي تجزيه و تحليل سيالاتي و حرارتي مي شوند. با توجه به نتايج آناليز طرح جايگزين انتخاب خواهد شد.

Boilers are one of the most important parts of the power plants. Superheater tubes have the main role in boilers and are subject to degradation because of many working conditions. According to the pressure and temperature of the working condition of the superheater tubes in boiler, failure is usually reported from the superheater tubes. Therefore, identifying the causes of this failure and its prevention is quite important. The reports on the failure of platen superheaters in several similar boilers whose inlet and outlet header is the same for all tubes indicate that a particular part of the tubes is more vulnerable than the rest in tubes and the failures are concentrated there. Location of the most failures is at the end of the 135-degree bend of the platen superheater. Therefore, this case was investigated at a special 320 MW power plant where there were seven units. The objective of this investigation is to find the cause of the failure and solve the problem for working in a long time with safety. The preliminary examination showed that the damaged point in this group had a higher temperature than the other groups in the same position. To prove the existence of the higher temperature at these points, three methods were used: metallography, oxide layer thickness measurement, and CFD analysis and all the three methods confirm the results. In this paper, different solutions were introduced for the 320 MW power plant issue. Each of the solution methods is subject to certain advantages and disadvantage. Following the analysis, among the solution methods, one of them was selected as the best solution. Based on the method, some schemes were offered as suggested plans as an alternative to the platen superheater tubes. These schemes were validated in comparison to the power plant superheater. Then, the investigation focused on the geometry of schemes. In addition, all of the three schemes were analyzed by CFD method. Based on the analytical results, one of the schemes was chosen as an alternative plan to the platen superheater for the power plant.