Power Plant Desulfurization

So far, the flue gas desulfurization of large-scale thermal power plants built or under construction at home and abroad is mainly based on the limestone-gypsum flue gas desulfurization wet process (FGD). The desulfurizing agent is limestone powder, and the quality and fineness of limestone powder The degree and particle distribution are one of the key factors affecting the desulfurization effect. Therefore, the preparation of limestone powder for desulfurization plays a vital role in the entire desulfurization process.

One. Several main factors affecting desulfurization efficiency in the preparation process of limestone powder

1. Limestone Grade

The grade of limestone is determined by the content of CaO. The maximum content of CaO in pure limestone is 56%. The higher the purity of the limestone, the better the desulfurization efficiency. As a process designer, when designing ingredients, he must not only calculate its chemical composition, but also understand its physical properties. The calcium oxide content of the first grade limestone is 48%-54%; limestone does not necessarily require the higher the CaO content, the better. Limestone with CaO>54% has high purity and is marbled, not easy to grind, and has strong chemical stability, so it is not suitable for use as a desulfurizer.

2. The Fineness Of Limestone Powder

The smaller the particle size of limestone powder particles, the larger the mass specific surface area. Since the dissolution reaction of limestone is a solid-liquid two-phase reaction, the reaction rate is proportional to the specific surface area of limestone particles. Therefore, finer limestone particles have good dissolution performance, various related reaction rates are higher, desulfurization efficiency and limestone utilization rate Higher, but the smaller the particle size of limestone, the higher the energy consumption of crushing. Generally required limestone powder has a sieving rate of 95% through a 325-mesh sieve (44 microns).

At the same time, the particle size of limestone powder is related to the quality of limestone. In order to ensure the desulfurization efficiency and the utilization rate of limestone reach a certain level, when the impurity content in the limestone is high, the limestone should be ground to be finer.

3. Limestone Powder Preparation Technology Using Vertical Milling Process

FGD process using limestone powder as a desulfurizer, the limestone powder needs to pass through a solid-liquid two-phase dissolution reaction, and the reaction rate is positive with the specific surface area of the limestone particles. The smaller the particle size of the limestone powder particles, the larger the mass specific surface area, the better the dissolution performance of the limestone particles, and the higher the various related reaction rates. 

However, the smaller the particle size of limestone, the higher the energy consumption of crushing. Generally required limestone powder has a sieving rate of 95% through a 325-mesh sieve (44 microns). At the same time, the particle size of limestone powder is related to the quality of limestone. In order to ensure that the desulfurization efficiency and the utilization rate of limestone reach a certain level, when the impurity content in the limestone is high, the limestone should be ground to be finer. 

Using traditional tube mill technology to prepare limestone powder has high energy consumption, low output, complex process flow, and difficult to control fineness and particle gradation. With the development of grinding technology, vertical grinding technology is adopted. 

Due to the principle of material layer grinding, the energy consumption is low (20-30% lower than the power consumption of the tube mill), the chemical composition of the product is stable, and the particle gradation is All are uniform and the process flow is simple.

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