The Million Dollar Annual Payback: Realtime Combustion Optimization with Advanced Multi-Variable Control At PPL Colstrip

摘要

Advanced Model-Predictive Multi-Variable Control provides realtime control of complexcombustion processes, such as those found in a large modern utility boiler. Advancedrealtime MPC controls are capable of making periodic predictions and setpoint/biaschanges in less than 10 seconds, on a continuous basis, making them faster than theresponse times of combustion hardware and processes. This makes the MPC controlsuitable for true realtime combustion control and optimization.The current popular understanding of these controls is that they are used to control NOxproduction. However, there are multiple other financial benefits which equal or exceedthe value of NOx reductions. These are accomplished via controllable loss managementstrategies, including excess O2 balancing and reduction, as well as superheat and reheatspray flow reductions. A properly configured and tuned MPC controller will typicallyreduce NOx and these other variables from 10 to 40%. Based on direct project results,and EPRI-published heat rate improvement data, these factors combine for economicbenefits which far exceed the cost of the control implementation on larger utility boilersof 500MW and above. An example improvement program calculation shows the relativecontribution of each of these factors.As part of recent control system upgrades and retrofits, PPL Colstrip has installed andutilized new combustion optimization systems, based on advanced Model-PredictiveMulti-Variable controls. These COS’s provide realtime control of complex combustionprocesses on three of the four units at site, with the fourth one currently beingimplemented. These controls were tested for control of NOx production, which in and ofitself will provides significant cost benefits as the plant eventually comes under localNOx control environmental standards. Heat rate improvements contribute furtherfinancial benefits which equal or exceed the potential value of Nox reductions, and arelarge enough to pay for the controller in less than one year. Benefits can then continue toaccrue by providing ongoing annual savings that grow as the cost of fuel andenvironmental compliance increases.