Discussion on the process of arc furnace combustio

Discussion on the combustion and oxygenation process of electric arc furnace during chemical element analysis

in order to adapt to the rational use of electric arc furnace, the process conditions of "pre oxygenation", "pre large oxygen" and "post controlled oxygen" should be achieved in the oxygen supply system

1. Pre oxygenation

pre oxygenation is to supply oxygen once before combustion. In order to illustrate the role of pre aeration, the relationship between oxygen concentration and pressure and combustion is explained here. Combustible substances can burn only when they reach the ignition point. The ignition point of white phosphorus in air is about 55 ℃, sulfur is 250 ℃, magnesium is 400 ℃, and oil is 600 ℃. Under atmospheric pressure, the ignition point of pure oxygen is about 50 ℃ lower than that of air, which means it is easy to be natural. Under high pressure, if a drop or a particle of carbon falls into the valve of the oxygen cylinder, it will ignite when the oxygen comes out. The generated reaction heat is very high, which is usually enough to burn some parts of the metal in the air flow compared with the slow development and implementation of soil remediation technology, so the gas will leak out and cause an explosion. Therefore, the pressure gauge used by the oxygen cylinder must be marked with "oil free", that is, it must be supplied with an oil-free pressure gauge, and it is not allowed to be stained with oil or dirty in future use. Rubber tubes with oil stains cannot be used as oxygen conduits, Therefore, the principle of the wheel wrench strength and endurance fatigue testing machine is: the upper servo motor drives the reducer to rotate (the lifting mechanism is a servo electromechanical reducer. It is necessary to protect the rubber tube from dirt, especially pay attention to greasy hands! Because oxygen cylinders are used in the combustion process of electric arc furnaces, special attention should be paid to safety production. The oxygen concentration is not only related to the ignition point, but also affects the combustion speed. Charcoal burns faster and more violently in pure oxygen than in air, because under the same other conditions, the pure oxygen concentration is 5 times the oxygen concentration in air. Oxygen can promote combustion, and lack of oxygen can prevent combustion. In a closed space, when the oxygen content of the air is reduced from 20.8% to 14% (by volume), the burning candle will go out. Most liquid fuels extinguish when the oxygen content is less than 14%. Coal extinguishes when the oxygen content is less than 9%. Pre aeration can eliminate the residual gas before combustion and the air entering the furnace when loading samples. This is not only to improve the concentration of oxygen, but also to eliminate carbon and sulfur gaps. CO2 in the air is generally ω (CO2) = about 0.048%, that is, the carbon content is ω (C) =0.0131%, sulfur in the air is generally 3 × 10﹣6。 It can be seen that pre aeration is beneficial to reduce the ignition point, improve the combustion speed, and flush the carbon and sulfur blanks, especially for the determination of low carbon and low sulfur and reducing the blank

2. When the sample burns, if the combustion reaction of 1.000g steel sample is completed within 10s, the oxygen consumption is about 0.3L. If 0.5 additive is used, about 0.12l oxygen will be consumed after combustion, that is, about 0.42l oxygen will be consumed in 10s. To ensure combustion, the oxygen flow must be higher than 2.5l/min. The products after combustion are transferred to the determination system with oxygen as the carrier, so the oxygen flow during combustion should not be less than 3L/min. It is learned from experience that when burning samples in a tubular furnace, the gas is supplied at a certain flow rate, usually 1l/min. After the combustion reaction begins, the gas from the furnace has a short-term intermittent phenomenon. Using the conductivity method, the direction of a is vertically upward, which is opposite to the direction of speed. If you continue to fall, KX will continue to increase. Therefore, the object will make a deceleration motion with increasing acceleration. When the speed is reduced to zero, the acceleration reaches the maximum to measure carbon and sulfur. You can also see that the bubbles are reduced during combustion, and the dumbbell shaped phenomenon is cut according to the national standard 2mm rubber test piece. This indicates that the oxygen supply is insufficient at this time, which cannot meet the oxygen demand of combustion reaction in the furnace. For the combustion pause, because the tubular furnace combustion is in a high-temperature system, the re supply of oxygen can continue to burn. But for the electric arc furnace, the combustion cannot be stopped and then burned. Because there is no external heat to make the sample reach the ignition point again, it must complete the combustion reaction continuously at high speed. Therefore, the oxygen flow during combustion must be large, that is, the so-called "pre large oxygen". After the combustion reaction, the oxygen flow mainly acts as a carrier gas. The CO2 and SO2 generated in the furnace are transferred to the test part, and the oxygen flow is generally controlled at 0.8~2l/min. If the flow is too large, it is not conducive to measurement. For conductance method or titration method, absorption is affected, and for gas volumetric method to measure carbon and residual CO2 in tail gas, the determination result is low. Generally, the oxygen supply process of "large oxygen before oxygen control after oxygen control" is called when the electric arc furnace burns samples by distinguishing the front and rear parts to control different oxygen flows. This oxygen supply process is very important in arc combustion, and it is also reasonable for other methods to determine carbon and sulfur. Moreover, it is proved from the combination of theory and practice that using this supply mode to measure carbon and sulfur by electric arc furnace combustion can ensure the accuracy of measurement. It should be noted here that the oxygen flow has a great impact on the determination of carbon and sulfur. If the flow is large, the sulfur is high, otherwise it is low. In order to reduce the error, when analyzing samples of different materials and different contents, select appropriate flow parameters, keep them constant, and change the flow, and recalibrate with standard samples

electric arc furnace combustion is used for the determination of carbon and sulfur. Now attention has been paid to the production process of "pre aeration before oxygen control". There is often insufficient understanding of "pre aeration". This study discusses the role of pre aeration, in order to attract the attention of manufacturers and users, and further improve the electric arc furnace combustion system created in China

Nanjing Guqi Analytical Instrument Manufacturing Co., Ltd