JP2007177269A - Method for preventing gas from leaking from chute for charging auxiliary material in molten metal smelting furnace, and apparatus for preventing gas leakage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing a gas from leaking from a chute for charging an auxiliary material in a molten metal smelting furnace so that CO can not be detected in the vicinity of a bunker arranged above the furnace, and to provide an apparatus for preventing the gas leakage. <P>SOLUTION: When smelting a molten metal by using the molten metal smelting furnace provided with the chute for charging the auxiliary material, which is arranged adjacent to a hood covering a furnace opening so as to collect an exhaust gas, and has an opening/closing gate for preventing back fire, this method for preventing the gas leakage comprises the steps of: toppling the molten metal smelting furnace over in an empty state before operation or moving it to another place; and passing water into the inside of the charging chute from an upstream of a position at which the opening/closing gate of the charging chute is installed to clean and remove a deposit. As a result, CO has not been detected in the vicinity of the bunker arranged above the furnace. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas leakage prevention method and a gas leakage prevention device from an auxiliary material charging chute of a molten metal smelting furnace, and more specifically, smelting reduction smelting chromium ore with a carbon material and melting stainless steel. Impurities are further removed from the smelting reduction furnace that melts the necessary mother molten metal, or the top blowing, bottom blowing, or top bottom blowing converter that melts molten steel by blowing oxygen gas into the hot metal and decarburizing and refining it. The present invention relates to a technique for preventing exhaust gas from leaking and being released into the atmosphere from an auxiliary raw material charging chute of a so-called “molten metal melting furnace” such as an AOD furnace used for (secondary refining).

  For example, one type of smelting reduction furnace that uses smelting reduction smelting of chrome ore with carbonaceous material and smelting the mother molten metal necessary for melting stainless steel uses an upper bottom blown converter type smelting vessel. . In this case, as shown in FIG. 5, on the molten metal 1 made of hot metal and iron scrap as the main raw material, the chrome ore 2 is introduced, and the auxiliary raw material such as the carbonaceous material 3 is introduced and disposed above. For blowing the oxygen-containing gas 6 through the blowing lance 4 and the bottom blowing tuyere 5 provided at the furnace bottom, blowing, melting and reducing the chromium ore with the generated heat and reducing atmosphere, and melting the stainless steel. Melt the necessary mother melt. Similarly, even in converters and secondary refining operations in which ordinary molten steel is melted, various types of converters hold hot metal that has been desiliconized, dephosphorized, and desulfurized in advance by pretreatment as necessary. In addition, a slagging material such as lime is added on top of it, and an oxygen-containing gas is blown through the top blowing lance, and the reaction is performed mainly by blowing and decarburizing reaction. Adjustment is performed to obtain molten steel having a desired composition.

  When such an operation is performed, a large amount of exhaust gas containing CO is inevitably generated. Even though a small amount of CO gas is not preferable for the human body, it is useful as an energy source. Therefore, the exhaust gas is generally recovered and reused. That is, as shown in FIG. 4, the opening of a molten metal melting furnace (hereinafter simply referred to as a converter) 7 is covered with a hood 8, the exhaust gas 10 is sucked with a blower 9, and dust is removed with a dust catcher 11. The gas holder 12 collects the gas. At that time, part of the exhaust gas is diffused to the atmosphere via the chimney 13.

  By the way, the hot metal and iron scrap of the main raw material are put into the furnace through the opening in a state where the furnace body is tilted before the start of operation, but the remaining chromium ore and the auxiliary raw material carbonaceous material and ironmaking material. In addition, during operation, the ferro-alloy and the like are charged using gravity through a charging chute 15 connected to the hood 8 from a bunker 14 provided above the furnace (see, for example, Patent Document 1). An example of this charging device is shown in FIGS. 3 (a) and 3 (b), which includes a bunker 14 equipped with a hopper scale 16 for weighing auxiliary materials, a charging chute (usually cylindrical) 15, The charging chute 15 is provided with a sealing device 17 (referred to as a backfire gate) that stops the backflow of the flame (backfire) and exhaust gas from the furnace. The backfire gate 17 is driven by a cylinder 18 when charging is not performed during operation, blocks the passage of the charging chute 15, and seals exhaust gas and the like.

However, even if the operator confirms that the backfire gate 17 is closed with the limit switch and operates, CO of about several tens of ppm may be detected in the vicinity of the bunker 14. This is not only inadequate to ensure the safety of the workplace, but also causes environmental problems.
JP 2003-253321 A

  In view of such circumstances, the present invention provides a gas leakage prevention method and a gas leakage prevention device from an auxiliary material charging chute of a converter type molten metal melting furnace in which CO is not detected in the vicinity of a bunker on the furnace. The purpose is to provide.

  The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention.

  That is, the present invention melts molten metal using a molten metal melting furnace provided with an auxiliary material charging chute having an openable gate that is connected to an exhaust gas recovery hood that covers the furnace opening and prevents backfire. When manufacturing, the molten metal melting furnace in an empty furnace state before operation is laid sideways or moved to another place so that water does not enter the furnace, upstream of the installation position of the open / close gate of the charging chute From the above, a method for preventing gas leakage from the auxiliary material charging chute of the converter type molten metal melting furnace is characterized in that water is poured into the charging chute to wash and remove deposits.

In this case, it is preferable to perform the cleaning and removal at a frequency of once after the operation of three charges. In addition, the flow rate of water used per washing is adjusted to 100 to 300 liters / minute · m ² (chute cross-sectional area) according to the properties of the auxiliary raw material, and the washing time is set to 4 to 8 minutes. Is preferred. Furthermore, it is preferable that the water is industrial water, or the molten metal is a mother molten metal necessary for melting stainless steel, and the auxiliary material is a carbonaceous material.

  In addition, the present invention provides an auxiliary material charging chute that is connected to an exhaust gas recovery hood that covers a furnace opening of a molten metal melting furnace and has an openable gate that prevents backfire, and the opening and closing of the charging chute An apparatus for preventing gas leakage from an auxiliary material charging chute of a molten metal melting furnace is provided with a water injection nozzle for cleaning and removing deposits in the chute on the upstream side of the type gate. In this case, 1 to 4 spray nozzles may be disposed on the outer periphery of the charging chute.

  According to the present invention, even during operation, the backfire gate of the input chute is surely closed, the backflow of exhaust gas to the bunker is stopped, and CO is detected in the vicinity of the bunker on the furnace. It will not be.

  Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.

  First, the inventor decided to investigate the cause of CO being detected in the vicinity of the bunker 14 on the furnace. Initially, the charging chute 15 was cylindrical, but it was examined in detail whether there was a hole somewhere and no leakage occurred, but such a hole could not be found. Next, since the deposit in the charging chute 15 has been conventionally purged and removed with nitrogen gas (see Patent Document 1), it was also investigated whether the flow rate of nitrogen gas was insufficient. As a result, it was found that purging with a large amount of nitrogen gas could remove the deposits produced when the dried secondary raw material was charged, but not when the wet secondary raw material was charged. Therefore, it was found that purging with nitrogen gas is hardly useful even at a high flow rate for deposits that are generated in a yard such as a carbonaceous material and produced by a secondary material that is often moist. Therefore, there is doubt about the sealing performance by the backfire gate 17 and when a detailed check is made, if the limit switch is activated and the closed state of the gate 17 is confirmed on the work, if the deposit 20 is attached, As shown in FIG. 2, it was found that there was a gap depending on the shape of the deposit 20.

  Therefore, the inventor continued to examine various countermeasures. As a result, it was determined that it would not be a good idea to dry the auxiliary material so as to prevent the formation of deposits, or to modify the backfire gate, and it was considered that it would not be a good idea. However, since water causes a steam explosion, it cannot be used during operation. Therefore, an experiment in an actual furnace was conducted using the time when the converter was not operated.

  Specifically, in the input chute of the auxiliary material having an openable backfire gate connected to the exhaust gas recovery hood that covers the furnace opening of the converter type molten metal melting furnace, the backfire gate is prevented. 1, a water injection nozzle 21 is provided on the upstream side of the gate 17, and the molten metal melting furnace in an empty furnace state before operation is laid down or moved to another place, and then water is poured into the chute 15. It was washed away.

  As a result, deposits could be removed, and when the furnace was operated again, gas leakage during the operation was completely prevented, so the molten metal melting furnace in an empty furnace state before the operation was laid down or moved to another place. After moving, the present invention was completed with the requirement that water flow from the upstream side of the gate 17 into the charging chute.

  In the present invention, it is preferable to perform the cleaning of the charging chute 15 with water and the removal of the deposits 20 at a frequency of once after three charge operations. Although it is desirable to perform the cleaning effect for each operation, it is economically preferable to reduce the frequency as much as possible. However, after the operation of continuous 4 charges, gas leakage may occur unless water cleaning is performed. Therefore, it is preferable to perform water cleaning once every 3 charges.

Also, the flow rate of water used for each water washing is adjusted at 100 to 300 liters / minute per unit cross-sectional area of the input chute according to the properties of the auxiliary raw material, and the washing time is 4 to 8 minutes. Is good. If it is less than 100 liters / minute · m ² (chute cross-sectional area), cleaning is insufficient and the removal of adhering matter is not performed quickly, and if it exceeds 300 liters / minute · m ² (chute cross-sectional area), the cleaning effect is saturated. Because it becomes excessive. This is because if the cleaning time is less than 4 minutes, the cleaning is not sufficiently performed and deposits remain, and if the cleaning time exceeds 8 minutes, the cleaning effect is saturated and further cleaning is wasted. In this case, a water pressure of about 2 kg / cm ² is sufficient. Note that the flow rate and time of water used for cleaning may be adjusted according to the state of adhesion. This is because the amount of adhesion varies depending on the properties of the auxiliary material.

  Furthermore, the water used for washing is not particularly limited in the present invention in terms of water temperature and water quality, but it is preferable to use industrial water. This is because it is more economical than using clean water. At that time, a solvent that promotes water dissolution of the deposit so as not to cause environmental problems may be added separately.

  In addition, in the present invention, one to four spray nozzles may be disposed on the outer periphery of the charging chute. The more spray nozzles are effective for shortening the cleaning time, but the cleaning effect is saturated even when there are more than four nozzles. In addition, the attachment angle of the injection nozzle is not particularly limited in the present invention. In short, any angle is acceptable as long as the deposits can be removed.

  Using a smelting reduction furnace capable of blowing an oxygen gas having a capacity of 180 tons at the bottom, chrome ore was smelted and reduced with carbonaceous material, and a molten metal necessary for melting stainless steel was smelted. A charging chute is connected to the hood that covers the furnace for the purpose of charging auxiliary materials. Further, the injection chute is provided with 1 to 4 water injection nozzles according to the present invention per chute.

  In these operations, the method for preventing gas leakage from the auxiliary material charging chute of the molten metal melting furnace according to the present invention was applied, and CO gas leakage was detected using a fixed CO monitor on the work floor above the furnace. In addition, in order to confirm the effect of this invention, the operation which does not perform water washing was also performed separately, and the CO gas leak was checked. Table 1 collectively shows the types of auxiliary raw materials used, the amount used per charge, the implementation status of water washing, and the presence or absence of CO gas leakage in the subsequent operation.

  From Table 1, according to the present invention, the backfire gate of the input chute is surely closed, the backflow of exhaust gas to the bunker is stopped, and CO is not detected in the vicinity of the bunker on the furnace. it is obvious.

It is a sectional side view explaining the gas leak prevention apparatus from the auxiliary material injection chute of the converter type molten metal melting furnace which concerns on this invention. It is a sectional side view of the making chute explaining the seal failure of the backfire gate. It is a figure which shows the auxiliary | assistant raw material injection | throwing-in apparatus of a molten metal melting furnace, (a) is a figure explaining the whole, (b) is a side cross section of the injection | pouring chute. It is a figure which shows the waste gas treatment equipment of a molten metal melting furnace. It is a sectional side view of the furnace explaining the reaction in the furnace which arises by the smelting reduction operation of chromium ore.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molten metal 2 Chrome ore 3 Carbon material 4 Top blowing lance 5 Bottom blowing tuyere 6 Oxygen containing gas 7 Molten metal melting furnace (converter)
8 Hood 9 Blower 10 Exhaust gas 11 Dust catcher 12 Gas holder 13 Chimney 14 Bunker 15 Input chute 16 Hopper scale 17 Backfire gate 18 Cylinder 20 Deposit 21 Water injection nozzle 22 Water piping 23 Nitrogen gas purge nozzle

Claims (7)

When melting molten metal using a molten metal melting furnace provided with an auxiliary material charging chute connected to an exhaust gas recovery hood covering the furnace opening and having an openable gate that prevents backfire,
Prior to operation, the molten metal smelting furnace in an empty furnace state was laid down or moved to another place, and water was poured into the charging chute from the upstream position of the opening / closing gate of the charging chute to clean and remove deposits. A method for preventing gas leakage from an auxiliary material charging chute of a molten metal melting furnace.   The method for preventing gas leakage from the auxiliary material charging chute of the molten metal melting furnace according to claim 1, wherein the cleaning and removal are performed once after the operation of three charges. The flow rate of water used for each washing is 100 to 300 liters / minute · m ² (chute cross-sectional area), and the washing time is 4 to 8 minutes. A method for preventing gas leakage from the auxiliary material charging chute of a molten metal melting furnace.   The method for preventing gas leakage from an auxiliary material charging chute of a molten metal melting furnace according to any one of claims 1 to 3, wherein the water is industrial water.   The said molten metal is a mother molten metal required for melting stainless steel, and an auxiliary material is a carbonaceous material, The auxiliary material of the molten metal melting furnace in any one of Claims 1-4 characterized by the above-mentioned. How to prevent gas leakage from the input chute. In the input chute of the secondary material that is connected to the exhaust gas recovery hood that covers the furnace opening of the molten metal melting furnace and has an openable gate that prevents backfire,
Gas leakage from an auxiliary material charging chute of a molten metal melting furnace characterized in that a water injection nozzle for cleaning and removing deposits in the chute is provided upstream of the open / close gate of the charging chute. Prevention device. The apparatus for preventing gas leakage from an auxiliary material charging chute of a molten metal melting furnace according to claim 6, wherein one to four of the injection nozzles are disposed on the outer periphery of the charging chute.

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