1WFGD运行关键因素剖析.ppt

Over! This figure, which was generated from data gathered during a pilot-scale FGD research program, shows that a significantly higher limestone loading (g-limestone/ L of slurry) level is required for the high calcium data to get the same removal level as the low calcium data. The reason is because it is more difficult for the limestone to dissolve in the presence of a high level of calcium due to the “common-ion” effect. The level of calcium in a process is normally determined by the level of dissolved chloride. As a result, systems with high chloride must operate at a higher limestone loading level to get equivalent removal performance. This figure, which is based on pilot-scale FGD research data, shows that, for a natural oxidation system, a higher limestone loading level must be maintained to achieve a specific removal performance compared to a force oxidation process. The reason is because the oxidation naturally strips CO2 gas from the slurry, reducing the dissolved carbonate concentration. This makes it easier for the limestone to dissolve. Dissolved aluminum in the scrubber slurry will inhibit the dissolution of limestone by forming a complex with dissolved fluoride which can interfere with the ability of the limestone to dissolve. This phenomena is called aluminum-fluoride blinding of the limestone. The source of the aluminum is fly ash that enters the scrubber. The source of fluoride is the flue gas. Normally the amount of fly ash entering the scrubber will determine if aluminum-fluoride blinding will occur. The data in the figure were obtained from a number of full-scale systems in the US. This figure shows that at any specific limestone loading level, a higher SO2 removal level will be obtained as you increase the dissolved magnesium concentration. The reason is that a higher magnesium concentration will increase the concentration of dissolved sulfite (SO3) which, in turn, increases the dissolved (liquid) alkalinity level of the slurry. Thi