The Future of Domestic Micro Silicon Powder

Micro-silica fume, also known as silica fume, is a kind of micro-silica dust recovered from flue gas purification and dust removal equipment of submerged arc furnace, which has been used as garbage to be treated by the company. With the development of science and technology, micro-silicon powder has been applied in more and more markets. The utilization of micro-silicon powder abroad has been ahead of China.

The main application fields of high-purity micro-silica powder abroad are as follows: 1. Marine anti-corrosive Building Specialty accounts for 30% of the market micro-silica powder output; 2. Advanced refractory industry accounts for 30% of the market micro-silica powder output; 3. Highway, bridge and special cement account for 30% of the market micro-silica powder output; 4. Chemical industry and electronics account for 5% of the market micro-silica powder output; 5. Other industries. 5% of the market output of micro-silicon powder

So where is the prospect of domestic micro-silicon powder, Xiaobian here for you to introduce.

I. Main Application Areas of Micro Silicon Powder

1. Application in concrete industry

Using micro-silica powder as admixture in concrete industry is one of the earliest, most fruitful and most widely used fields in the comprehensive utilization of micro-silica powder abroad. Because of the fine particle size, large specific area, high purity of Sio2 and strong pozzolanic activity of micro-silica fume, many properties of concrete are improved by adding micro-silica fume as admixture.

(1) Increasing the Early and Final Strength of Concrete

Foreign studies have proved that when the substitution rate of micro-silica powder for cement is less than 30%, the autoclave curing temperature is 80 C, the compressive strength of mortar in one day is twice as high as that without micro-silica powder (100 MPa). If autoclave curing is adopted, the compressive strength of mortar is almost three times (150 MPa). When standard curing is adopted, the compressive strength of mortar is also significantly improved. H.H. Bache of Canada proposed that when micro-silica powder was used in combination with high-efficiency alkali water agent, the water gelatinization (W/C+Si) of concrete could be reduced to 0.13-0.18, the cement particles were filled with micro-silica powder, and the compressive strength of concrete was 3-5 times that of non-silica powder. At present, the United States, Denmark, Norway and other countries have prepared concrete with high strength of 1100kg/cm2 using micro-silicon powder as admixture, and the technology is simple, economic benefits are good, so it is widely used.

(2) Increasing compactness

The content of reactive silicon is increased by adding micro-silica powder in concrete. Crystal growth is observed in the void of cement paste of concrete with micro-silica powder under electron microscope. In addition, the silica fume particles are very small and uniformly filled with concrete micro-pore. The microporous volume of concrete cement paste mixed with silica fume is obviously reduced under any curing conditions determined by cement injection method abroad.

(3) Improving segregation and sand-water properties of concrete

After pouring concrete, water is often separated from concrete, that is, water film is formed on the surface, also known as floating slurry, which makes the distribution of superstructure uneven and affects the quality of building. Foreign studies have proved that the more Si/(Si+C) substitution rate is added, the more difficult it is for concrete materials to segregate and bleed. When the replacement rate reaches 15%, the slump of concrete can hardly produce segregation and bleeding even if it reaches 15-20 cm. When the substitution rate is 20-30%, it is not easy to segregate the concrete directly into tap water. Due to the improvement of segregation and sand-water performance of concrete by micro-silica fume, concrete mixed with micro-silica fume can be used in underwater projects such as ports and tunnels.

(4) Improving the impermeability, chemical corrosion resistance and specific resistance of concrete

As the addition of micro-silica fume improves the compactness of concrete and greatly reduces the cement voids, the impermeability of micro-silica fume concrete is improved. According to foreign research and diagnosis, when the substitution rate of micro-silica powder in concrete is 10-20%, the impermeability and chemical corrosion resistance of concrete are significantly improved, and the corrosion resistance of steel bar is also improved. This is due to the increase of compactness and SiO 2 content, which effectively prevents the invasion and corrosion of acid ions. In addition, the specific resistance of concrete can be increased by 1.9-1.6 times due to the high specific resistance of silica fume (up to 1.2X10-sup1; & sup1; & Omega;.Cm, 90-150 C).

Because of the above advantages of concrete with micro-silica fume, micro-silica fume has been widely used as a new material abroad, and has been extensively and deeply studied, which lays a foundation for the formulation of national or international standards for the use of micro-silica fume. The United States, Canada, Norway and other countries have formulated specifications (standards) for the use of micro-silicon powder, as shown in the table.

2. As Return Furnace Charge

The United States has proposed that pellets should be used as raw materials for electric furnace smelting. The pellet ratio is 453.6 kg of silica with 22.7 kg of micro-silica powder to make pellets. The maximum size of the pellet is 19-25mm. The pellet is too big to be dried through. It is easy to break in the electric furnace, which affects smelting. If the pellet is too small, the permeability of the material layer is not good, and the furnace condition is also affected. The water content in the pellet can reach 20%, the density is 0.83-0.92, the dry pellet is (0.72-0.75) X10-sup3; kg/m3, which is dried in the air day and night. Sufficient mechanical strength can be obtained. It has been proved by electric furnace smelting that when adding a large number of pellets, the furnace runs for three weeks, and no reduction of silicon recovery and increase of unit power consumption are found. The Norwegian company Ecken has also produced 100 M & sup3 of 20,000 kW metal silicon furnace per day and night. The micro-silicon powder is pelleted and returned to the furnace for smelting test. The pellets with a diameter of 1-5 cm were prepared by mixing water without binder. The pellets were sintered in a shaft furnace at 800-1200 C. The sintered pellets had sufficient mechanical strength. The pellets need not be dried before they are added to the shaft furnace, and there is no problem of bursting and unsuitability of the sintered pellets. Moreover, because there are few impurities in the pellets without additional binder, the pellets can be returned to the electric furnace as smelting materials.