What are the factors that affect the desulfurization efficiency of limestone?

The preparation of limestone powder has become a prerequisite for thermal power desulfurization and improving desulfurization efficiency. What are the factors that affect the desulfurization efficiency of limestone?

1. Quality of limestone

Normally, the CaSO4 content in limestone should be higher than 85%. If the content is too low, it may cause some problems in operation due to the high amount of impurities. The quality of limestone is determined by the content of CaO, and the higher the purity of limestone, the better the desulfurization efficiency. But limestone does not necessarily have a higher CaO content. Limestone with CaO>54% is not suitable as a desulfurizer due to its high purity, difficulty in grinding, and strong chemical stability.

2. Fineness and gradation

The fineness and gradation of limestone powder are important factors affecting desulfurization efficiency. Desulfurization in a circulating fluidized bed boiler not only requires the fineness of limestone, but also the particle size distribution of limestone. Wet flue gas desulfurization after the furnace is a solid-liquid two-phase reaction due to the dissolution reaction of limestone. Therefore, finer limestone powder has better dissolution performance and higher desulfurization efficiency.

3. The impact of the reactivity of limestone on the performance of desulfurization systems

The characteristics of limestone as an absorbent not only include its chemical composition, but also its reactivity. The alkalinity of the desulfurization system is provided by the dissolution of limestone powder, and the activity of the absorbent affects its solubility and dissolution rate. The activity of an absorbent includes the type of absorbent, its physicochemical properties, and the acidic environment in which it reacts. The physical and chemical properties of limestone include purity, crystal structure, impurity content, particle size distribution, and unit total surface area and particle density including internal surface area (i.e. porosity). Limestone with high activity can achieve high SO2 removal efficiency while maintaining the same limestone utilization rate.

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