A Case Study on Process and Energy Optimization at Captive Power Plant of NRL

The old saying “Excellence is the gradual result of always striving to do better……. The noblest search is the search for excellence” An integrated approach to achieve continuous improvement and reach towards excellence in Utility Boiler Operation. This paper highlights the case study carried out regarding the successful trial run of the Flue Gas Recirculation of the Utility Boiler of Co-generation plant of the Numaligarh Refinery Limited, Golaghat, Assam. The study was carried out as to why the Flue Gas Recirculation (FGR) fans trip, why it troubles the burner and why it trips the boiler. It brings into light the different factors leading to the problems and hurdles in the trial run of the Flue Gas Recirculation (FGR) fans. Since the boiler's commissioning, this fan has been unable to be used. The issues could be found and resolved after a comprehensive investigation, and the fans could be successfully operated without tripping the boiler. Many favourable results are noted and resulted in the process and energy optimization in the operation of the utility boiler after it is successfully put into service. In Numaligarh Refinery Limited (NRL), Co-generation plant (CGP), Utility Boiler (UB) is used to produce High pressure super-heated steam. One of the accessories named Flue Gas Recirculation (FGR) could not be put into service due to certain problems. FGR is a combustion modification process. The combustion process is a process of rapid oxidation, followed by light phenomena and the release of large amounts of energy, able to maintain it at high temperatures. As the name implies, a portion of the combustion products exiting the boiler are recirculate and introduced into the primary combustion zone. In UB, there are two nos. of FGR fans. But they could not put into service for a long time since commissioning. After a series of studies and experiments, the problems or factors were identified viz. selection of correct UB load at which the fan should be started, dampers adjustment, burner flame stability, etc. After identification and trouble shooting of these problems, the FGR fans could be run successfully and put into continuous service. Following advantages were achieved in UB after the service of the FGR fans: Increases steaming rate of the UB Saves Energy (Fuel optimization) Reduced harmful NOx gas Emissions Increased in flue gas back end temperature Lowers Greenhouse gas CO2 emission as the amount of fossil fuel is reduced Thus the above case study helped one of the important UB accessories to successfully put into service leading to various benefits, flexibility and process optimization in the operation of the UB.