## 5 Analysis of Countermeasures for Yellow Plume  
### Discussion on Control Measures from Gas Turbine Side  
The yellow plume is mainly from the gas turbine side. As shown in Figure 20, the nozzles of the 6F unit are adjusted during the start-up period. As shown in Figure 21, the fuel flow rate and the opening angle of the compressor inlet guide vanes (IGV) of the 6F unit are changing during the start-up period. Figure 19: NO concentration at Point 3. Figure 17: CO concentration at Point 1 and Point 2. During the start-up period, the burner adjustment and unit pollutant emission are summarized as follows:  
1. The gas turbine starts to ignite, PM1 and PM2 open simultaneously. With the success of ignition, gas flow of PM2 gradually increases, while gas flow of PM1 gradually decreases. When only the PM2 nozzle is opened, the NO is relatively low. When the open degree of PM2 reaches 80%, there is a sudden increase of NO concentration. 2. When the rated speed of gas turbine reaches 95%, PM1 nozzle begins to open, while PM2 gradually reduces the amount of fuel until the fuel valve is fully closed. When only PM1 nozzle is open, the unit and the NOx concentrations change little. Then, the unit starts to connect to the grid. 3. When the gas turbine is connected to the grid successfully and begins to load up, the combustion mode is switched over and PM2 is put into operation. In the switching process, the combustion temperature is relatively high, and the NO reaches the highest value. With the open degrees of PM2 and PM1 entering a stable state, the NO rapidly drops back to normal, and the NO\({}_{2}\) enters a stable and high concentration period. After that, the open degree of PM1 increases, and the gas turbine load increases. With the increase of combustion temperature, NO concentration increases slightly from the previous stage, and NO\({}_{2}\) enters the highest concentration period. 4. When the gas turbine needs to increase to the base load, the combustion mode changes again. The open degrees of PM2 and PM1 decrease, PM3 and QUAT nozzles gradually open, and the switching moment has the characteristics of sudden increase of NO concentration. After switching successfully, PM1, PM2, PM3 and QUAT nozzles all open. Then, the nozzles gradually increase open degree, and the gas engine load increase. At this time, the combustion temperature of gas turbine increases gradually, the concentration of NO increases gradually, and the concentration of NO\({}_{2}\) has a gradual downward trend. Because the open degree of each nozzle is changing, the concentration of NO has small fluctuations. Although PM1 is in premixed mode, its fuel coefficient (fuel equivalent ratio) is relatively high, which plays a role in stabilizing the flame and adjusting combustion dynamic stability. PM2 and PM3 nozzles are in the lean combustion limit region or even slightly lower. Subsequently, the gas turbine reaches the stable base load; at this  
Figure 21: Open degree of inlet guide vanes (IGV) and fuel flow rate during the start-up period. Figure 20: Open degree of burner nozzles during the start-up period. time, the fuel flow rate of each nozzle reaches the optimal ratio, and the concentrations of NO and NO\({}_{2}\) reach a steady low state. Based on the above research and analysis, several measures to suppress the yellow plume from the gas turbine side are proposed as follows:  
1. The time from the unit being connected to the grid successfully to full load should be reduced, and the rate of load rise needs to increase. For the 6F unit, the running time of PM1 + PM2 premixed mode should be reduced to shorten the yellow plume time. 2. The start-up strategy of the gas turbine should be adjusted. The exhaust temperature of gas turbine during the start-up period should not exceed 500 \({}^{\circ}\)C to reduce the NO conversion to NO\({}_{2}\) in the HRSG, which can alleviate the phenomenon of yellow plume. 3.