Decision factors of silica fume active

Microstructure: chemical composition of silicon meet the requirements of indicators, has been get the best microstructure in refining, ensure its has the best activity to involve in the response, while pulverizing must minimize its deterioration effect of the natural micro structure, reduce the deformation between grain and grain, the majority of silica fume (more than 99.8%) remained in the original natural microstructure. Percussion method is the best method for pulverizing. Because it uses block way broken silicon, make it splintering with the weakest link in vivo, not squeezing, pressure, grinding to cause structure be out of shape.

Surface area: particle surface area is surface area per unit mass occupied, with m2/g as unit. It is involved in the chemical reaction ability. Silica fume’s specific surface area, the speed to participate in the reaction is fast, reaction is more perfect, high utilization ratio of silicon, the reaction region fluidized state is more ideal, silicon consumption rate is lowest, which shows its high activity. Therefore the surface area has become an important index of silicon powder activity.

Grain size distribution: direct synthesis is fluidized in multi-stage, grain size gradually changes, its surface constantly updated, complete reaction, silicon consumption has also decreased. Therefore, silica fume particle size match to particle, in order to obtain the best effect, to formulate the most suitable particle size distribution. Thus the milling method must ensure that the grain size composition is adjustable, and the yield was higher. Such as preparation of 1T 0.1mm~0.4mm silica particles approximately 85% is the most suitable for the synthesis reaction.

Surface protection: produce quality, grain index requirements of qualified products powder, surface active need to protect, there are three principles: be benefit to chemical reaction; be conducive to the prevention of combustion; helps maintain the loose and dry. Silicon has strong oxide performance, especially the fine powder, can burn in air when encounter fire, generating SiO2 and release a lot of heat.

In the storage and transport, delivery of finished powder, generally adopts a closed, N2 storage and N2 delivery, this is also the effective measures to protect silicon powder active. A silicon surface activity of the final judgment is the production practice, the effect of participating in chemical reactions and how well the ability in market competition performance. Of course, in order to obtain the high activity, there is also a master of flour milling method problem, need a process of knowledge, must stand the test of time.

Roll grinding method in milling process, need high energy consumption N2 protection, maintain the N2d 93% in pulverizing system, every per ton of product need to use N2 >300m3, due to the circulating N2 rising temperature in pulverizing system, reached 60 ~70 , which also contains 7% oxygen, silicon surface N2, O2 also inevitably. But in the milling process, the steel consumption is high, around 0.15kg/t, consumption of steel (iron ) adhered to the surface of silicon powder, the powder prepared by roller mill, the appearance is dark black. No N2 protection impact rotation method of silica fume, the appearance is bright. The percussion mechanism of powder system temperature is lower than 40 , steel consumption mainly in the blade, every per ton powder consume steel is about 0.1kg~0.05kg below.

Source:http://www.mhcmp.com