Additives as chemical products have specifications. Constant carbon, sulfur determination, use of analytical purity, low content determination, sometimes with pure or electronic pure reagents, requires less impurities, carbon, sulfur content should be low. In addition, attention should be paid to the physical properties of the additives such as the geometry, particle size, and voidage. Such as tungsten series flux, particle size of 0.84 ~ 0.42mm, porosity of about 15%, so that good air permeability, fast response, is conducive to oxidation combustion. More importantly, there is a blank problem for additives. The blank value of additives is required to be small, which should generally be less than 10% of the carbon and sulfur content of the tested substances. This requirement does not cause much trouble for the determination of high carbon and sulfur content. For the determination of low carbon and low sulfur, it is a big problem. For samples with a carbon content of 0.005% and a sulfur content of 0.0005%, the carbon content in the additive shall be less than 0.0005%, the sulfur content shall be less than 0.00005%, the carbon content shall be 5×10-6%, and the sulfur content shall be 0.5×10-. 6% of the additive is very difficult, even if it can be prepared, it is difficult to determine its content. Therefore, the blank problem of additives is the most difficult problem to be solved in the determination of low-carbon and low-sulfur processes.
Sometimes use some special additives or composite additives, electric arc furnace combustion additives selected silicon molybdenum powder, high-frequency furnace combustion use tin particles containing tungsten, are composite additives. Because of the different composition and different nature of the additives, they play different roles in the combustion process.
The role of additives 1 flux The melting point of iron is about 1529 °C, in the 1500K temperature is difficult to melt, although iron contains other elements, the freezing point is reduced, but can not make iron melt into a liquid. CO2 and SO2 cannot escape in the solid phase and can only be released in the liquid phase. Therefore, fluxes must be added to lower the melting point. Due to the importance of this point, additives were often called fluxes.
2 Among the additives used in the heating effect, some are metal and non-metal elements. Oxidation and combustion in the oxygen stream can release a large amount of heat, which can increase the furnace temperature, especially for the electric arc furnace combustion.
3 Adjusting the acid-base oxidation of the medium to generate CO2 and SO2 are both acidic oxides. The alkaline medium is not conducive to the release of CO2 and SO2. Selecting the appropriate amount of partial acidic additives to the combustion system can make the medium neutral or weakly acidic. , is conducive to the escape of CO2 and SO2. In particular, SO2 is more sensitive to the acidity and alkalinity of the media. Therefore, pay attention to adjust the pH of the medium.
4 Stirring action Stirring accelerates the diffusion of sulfur ions, which is conducive to contact with oxygen and accelerates the oxidation reaction. Additives such as SiO2 can accelerate the diffusion of sulfur ions as the liquid density is lower than that of iron oxides in the process of upward floatation in the system. Some additives generate gas after heating, and when the gas escapes, they play a good stirring effect.
5 Catalytic action such as copper oxide, in the combustion process, carbon and sulfur can seize the oxygen in CuO to generate CO2 and SO2, and then oxygen and copper to CuO, catalytic acceleration.
6 Stabilizing effect The combustion of the electric arc furnace is sometimes not stable. If appropriate amounts of tin particles or silica are added to the electric arc furnace combustion, it will help stabilize the combustion.
7 Anti-jamming effect The dust generated after combustion such as Fe2O3, SnO2, etc., has an adsorption effect on SO2, resulting in low test results. Adding relevant additives can prevent adsorption and reduce interference.
8 It is important to participate in the chemical reaction. It is very useful in the high-speed determination of sulfates and the combustion of nitrogen.
Sometimes use some special additives or composite additives, electric arc furnace combustion additives selected silicon molybdenum powder, high-frequency furnace combustion use tin particles containing tungsten, are composite additives. Because of the different composition and different nature of the additives, they play different roles in the combustion process.
The role of additives 1 flux The melting point of iron is about 1529 °C, in the 1500K temperature is difficult to melt, although iron contains other elements, the freezing point is reduced, but can not make iron melt into a liquid. CO2 and SO2 cannot escape in the solid phase and can only be released in the liquid phase. Therefore, fluxes must be added to lower the melting point. Due to the importance of this point, additives were often called fluxes.
2 Among the additives used in the heating effect, some are metal and non-metal elements. Oxidation and combustion in the oxygen stream can release a large amount of heat, which can increase the furnace temperature, especially for the electric arc furnace combustion.
3 Adjusting the acid-base oxidation of the medium to generate CO2 and SO2 are both acidic oxides. The alkaline medium is not conducive to the release of CO2 and SO2. Selecting the appropriate amount of partial acidic additives to the combustion system can make the medium neutral or weakly acidic. , is conducive to the escape of CO2 and SO2. In particular, SO2 is more sensitive to the acidity and alkalinity of the media. Therefore, pay attention to adjust the pH of the medium.
4 Stirring action Stirring accelerates the diffusion of sulfur ions, which is conducive to contact with oxygen and accelerates the oxidation reaction. Additives such as SiO2 can accelerate the diffusion of sulfur ions as the liquid density is lower than that of iron oxides in the process of upward floatation in the system. Some additives generate gas after heating, and when the gas escapes, they play a good stirring effect.
5 Catalytic action such as copper oxide, in the combustion process, carbon and sulfur can seize the oxygen in CuO to generate CO2 and SO2, and then oxygen and copper to CuO, catalytic acceleration.
6 Stabilizing effect The combustion of the electric arc furnace is sometimes not stable. If appropriate amounts of tin particles or silica are added to the electric arc furnace combustion, it will help stabilize the combustion.
7 Anti-jamming effect The dust generated after combustion such as Fe2O3, SnO2, etc., has an adsorption effect on SO2, resulting in low test results. Adding relevant additives can prevent adsorption and reduce interference.
8 It is important to participate in the chemical reaction. It is very useful in the high-speed determination of sulfates and the combustion of nitrogen.
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