JP2005530923A - Method for sintering iron oxide-containing materials in a sintering machine - Google Patents

Abstract

The invention relates to a method for sintering materials containing iron oxide in a sintering machine. According to said method, a sinter mixture containing a solid fuel is ignited, gases containing oxygen are conducted through the sinter mixture and the hot final sinter product is cooled after discharge. One portion of the waste gas is returned to the sintering machine as recycled gas and the other portion of the waste gas is evacuated as residual gas. The division of the total waste gas quantity into recycled gas and residual gas is achieved by a variation of the process surface (sinter strand).

Description

  The present invention relates to a method according to the preamble of claim 1 for sintering an iron oxide-containing substance in a sintering machine comprising a sintering belt, a suction box and an ignition furnace.

Sintering of iron oxide-containing materials, in particular iron ore or iron ore concentrate, is carried out in a sintering machine. A sintering mixture consisting of iron ore, return ore, solid fuel and flux is loaded onto a sintering belt and the fuel on the material bed surface is ignited under an ignition furnace. Subsequently, fresh air is sucked through the sintering bed, and the sintering front moves from top to bottom in the sintering bed. Waste gas is drawn into the gas collection system from the suction box below the carrying side of the sinter bed and sent to the atmosphere after cleaning. The sintering process requires heat transfer between the hot combustion gas and the cold solid. The amount of solid and the amount of air are thermally equivalent. This heat exchange requires a large amount of air and therefore a large amount of waste gas. The waste gas contains moisture evaporating from the sintering mixture, CO ₂ from the fuel combustion and calcination processes, from sulfur combustion-mainly from added fuel-sulfur oxides, CO from incomplete combustion. Intrusion air is air that reaches waste gas without being utilized from between the pallet side wall and the charge. Further, the waste gas includes dioxins and furans, and particularly includes waste gas taken out from the rear part of the sintered belt. Furthermore, the waste gas carries the dust together and the dust needs to be removed.

  Even if the operators of such sintering machines take into account the increasingly stringent conditions of each authorized authority, they reduce the amount of waste gas and dioxins and furans that are still contained in the flue air. We strive to keep it as low as possible.

  In order to reduce the amount of waste gas, it has already been proposed to divide a waste gas flow and circulate and guide a partial amount (Patent Document 1, Non-Patent Document 1). A special adjustment of the amount of waste gas divided is proposed in Patent Document 2. This known method is equivalent to the sum of the gas produced during the sintering process, the oxygen-enriched gas added for oxygen enrichment, and the ingress air entering from the outside minus the oxygen consumption. Only the amount of waste gas to be discharged is discharged as exhaust gas. Another waste gas partial stream is returned as a recycle gas and enriched to an oxygen content of up to 24% by addition of an oxygen enriched gas prior to loading the sintering mixture.

  Non-Patent Document 2 introduces equipment constructed according to the method described in Patent Document 2 under the title “Environmental protection by returning waste gas in iron ore sintering equipment”.

  Mainly the waste gas is partially trapped, on the one hand being returned to the sintering belt as circulating gas and on the other hand being discharged as exhaust gas. A fresh air supply line is in communication with the circulation line so that the oxygen content in the returned waste gas stream can be set to a reference value.

Patent Document 3 discloses a method for removing harmful contained substances from waste gas of a sintering facility. In this known method, a powdered adsorbent is added to the waste gas stream in the form of lignite coke, and the waste gas stream mixed with the adsorbent is subsequently passed through an electrostatic precipitator. The adsorbed admixture is supplied again to the sintering process after filtration. This method can be improved when the waste gas stream is passed through a pre-separator before passing through the electrostatic precipitator.
JP 52-116703 A European Patent Application No. 0535727 German Patent Invention No. 19623981 Steel (Stahl und Eisen) 99 (1979) No. 7, pp. 327/33 Steel (Stahl und Eisen) 115 (1995) No. 11, pp. 37-40

  The object of the present invention is to further optimize the sintering process, and in the process a small amount of waste gas and good sintering quality, especially dioxins, furans and dust content still contained in the exhaust gas. To ensure that it is below the limits set by the authorizing authority.

  This problem is solved together with the features of the features starting from the preamble of claim 1. Advantageous configurations are each the subject of the dependent claims.

  According to the teachings of the present invention, the process volume changes result in a division of the total amount of waste gas for circulating gas and exhaust gas, where the intersection between the suction of circulating gas and the suction of exhaust gas is determined by sintering quality and The maximum amount of waste gas is selected to be circulated and guided without impairing the sintering performance. The exhaust gas is a partial amount having a low harmful substance concentration, and the circulating gas is a partial amount having a high harmful substance concentration. Furthermore, the heat energy of the extracted circulating gas is used for heating the exhaust gas, and heating is carried out to a temperature to avoid falling below the dew point, but this temperature was ensured when discharging the entire amount of waste gas. Below the mixing temperature.

  Dividing the sintered belt process surface into a partial area where the amount of waste gas is guided as a circulating gas and an area where the waste gas is discharged as an exhaust gas is a burden on the concentration of harmful substances. The purpose is to divide the waste gas stream into a small amount and a high concentration. The part with less burden is separated from dust and the adsorbent brought in, including dioxins and furans adsorbed to it, and then heated to avoid the dew point of acids, and then the chimney is discharged as exhaust waste gas. Can be discharged through. A large amount of dioxins and furans is circulated and guided to the circulation, and when returned to the high-temperature sintering mixture, most dioxins and furans are decomposed and harmless. it can.

  Furthermore, the adsorbent charged into the waste gas stream is used to be particularly effective when the temperature in the waste gas stream is low. This will be achieved by dividing the amount of waste gas into circulating gas and exhaust gas.

Exhaust gas is withdrawn from the sintering belt region in the charging region and the subsequent region. This region has a lower temperature compared to the circulating gas region, despite being heated to avoid going below the H ₂ SO ₄ dew point. According to the present invention,
-Dividing the amount of waste gas;
-Multiple goals are achieved by combination with heating before exhaust emission.
-The total amount of waste gas to be discharged is kept small.
-Adsorbents blown into the exhaust gas are particularly effective because the temperature of the exhaust gas is low, and the proportion of harmful substances remaining in the exhaust gas to be exhausted meets the standards of the authorities.
-Below the H ₂ SO ₄ dew point is avoided by heating the exhaust gas.
-The thermal energy of the circulating gas is used energetically to heat the exhaust gas.

  This proposed change of process plane split is a very simple but effective means of optimizing the process. That is, on the other hand, it can be achieved that the ratio of the oxygen supply amount and the oxygen consumption amount approaches the ideal state 1, and therefore the amount of waste gas becomes very small. On the other hand, the performance of the equipment can be adjusted with consistently good sintering quality. By changing the main parameters controlling the process, optimum conditions can be achieved with regard to waste gas quantity, performance and quality.

  The amount of waste gas that is circulated further has the further effect that the required oxygen supply is low compared to the standard process. Therefore, in extreme cases, the demand can be covered by oxygen brought in by the sucked ingress air. At the same time, fresh air to be supplied separately, which is necessary in addition, is saved.

In a specific case, when fresh air is additionally required to supplement the sucked ingress air, suction air generated in the cold sieving area for dust removal instead of the conventional suction ambient air Is considered advantageous. In the steps of the proposed method, two goals are achieved simultaneously.
-The necessary dust removal in the cold screening area is used as oxygen carrier for the sintering process.
-The sintering mixture is used as a filter for dusted suction air, eliminating the need for a separate filter.

  Other features, advantages and details of the invention will become apparent from the following description of one embodiment shown in the drawings.

  FIG. 1 is a schematic flow diagram illustrating a sintering facility operating in accordance with the present invention. The core of the equipment is a sintered belt 1, in which the charging of the mixture for sintering takes place on the right side and the sintered product is dropped on the left side. This transport direction is indicated by arrow 2. Suction boxes and attached waste gas pipes 3 and 4 are arranged on both the left and right sides of the sintering belt 1, and the waste gas taken out at the start end region of the sintering belt 1 is discharged as exhaust gas, and the sintering belt The waste gas taken out in the end region 1 is circulated and guided. The waste gas to be circulated is supplied to the heat exchanger 6 through the pipe 5 and then supplied to the filter 8 disposed in the middle through the other pipe 7. This filter has a function of separating dust from waste gas.

  After passing through the filter 8, the return gas is supplied to the sintered belt 1 through the pipe 9 by the exhaust fan 22 and is uniformly distributed on the sintered belt 1. The written arrow reveals the charging of the return waste gas onto the sintered belt 1. The exhaust gas to be discharged is supplied to the existing heat exchanger 6 through the pipe line 10, and the heat of the circulating gas is used for heating the exhaust gas. This should avoid going below the dew point of sulfuric acid. After passing through the heat exchanger 6, the exhaust gas is supplied to the spouted bed reactor 12 via the pipe 11. In this spouted bed reactor 12, as is well known, brown coal dust coke is blown as an adsorbent so that harmful substances such as dioxins and furans in the exhaust gas can be deposited thereon. After passing through the spouted bed reactor 12, the exhaust gas is supplied to the filter 14 via the pipe line 13, and the dust and the adsorbent blown in advance are separated in the filter. Thereafter, the exhaust gas purified in this way is supplied to the chimney 16 via the pipe line 15 by the exhaust fan 23 and released into the atmosphere.

  The selective and individual fresh air supply 21 written in FIG. 1 is only necessary if too little oxygen is being brought in by the aspirated ingress air. The sintered product is dropped at the end of the sintered belt 1 and cooled in the rotary coolers 17 and 18. The air sucked in the rotary coolers 17 and 18 is supplied to the filter 20 through the pipe line 19, and the accompanying dust is separated.

  As is known, the dust sucked in the sintering equipment itself, the blast furnace gas generated from the blast furnace, and the cast hole dust are aggregated into conical particles (mini-pellets) with water while adding quick lime. This agglomeration takes place in a mechanical vortex mixer 24, also called “Eirich mixer”. The wet agglomerates are continuously fed into the sintering mixture in the charging zone.

  2 and 3, the sintering method according to the state of the art (FIG. 2) is compared with the method according to the invention (FIG. 3).

  In both these diagrams, the gas quantity kg / h / m is plotted over the wind box. The lower line with a black filled square shows the oxygen consumption of the fuel in the sintering mixture. The black line with diamonds shows the oxygen donation over the supplied sintering air, which is the sum of the ingress air drawn in and the fresh air supplied. The third line with a triangle shows the transition of the amount of waste gas.

  By directly comparing both diagrams, the effect of the circulating gas can be fully appreciated. The required oxygen supply is reduced and the second line extends slightly above the first line at least in the region of the first wind box.

  The transverse lines written boldly in FIG. 3 represent the separation of the sintered belt 1 from the circulating gas region and the exhaust gas region according to the present invention, and the double-headed arrows indicate the possibility of the separation part sliding. The sliding of the separation points according to the present invention makes it possible to fully optimize the process.

  Sliding in the left direction at the separation point means that the oxygen supply amount is shifted to a lower value as the ratio of the circulating gas increases. Ideally, oxygen supply amount = oxygen consumption amount. Low oxygen supply means a small amount of waste gas at the same time. This is because both these quantities are linked together by the combustion process.

  When the separation part slides in the right direction, the ratio of the circulating gas decreases with a constant good sintering quality, and therefore the amount of waste gas increases somewhat.

  Depending on the possibility of the separation part sliding, the optimum state can be easily set according to the process conditions.

  FIG. 4 is a schematic view showing a partial region of the arrangement of the suction box 25 and the flue gas collection pipes 5 and 10.

  The suction box 25.1 in the start end region of the sintering belt has a fixed separation part 26 for the circulating gas discharge line 5. In this embodiment, a total of four suction boxes 25.2 following this have variable separation portions 27. The variable separation part 27 means that these suction boxes 25.2 can be selectively switched to the circulating gas exhaust line 5 or the exhaust gas exhaust line 10. The effects achievable by this are detailed at the beginning.

  The remaining suction box 25.3 up to the dropping area 28 is fixedly connected to the circulating gas exhaust line 5.

  In the case of an emergency, the fixed separation unit 29 disposed in the exhaust gas exhaust pipe 10 can be removed so that the entire generated waste gas can be derived.

3 is a schematic flow diagram of a sintering facility operating in accordance with the present invention. 1 is a diagram of a method according to the state of the art. FIG. 2 is a diagram of a method according to the invention. It is the schematic which shows the arrangement | positioning relationship between a suction box and a flue gas collection pipeline.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sintering belt 2 Conveyance direction 3 Exhaust gas exhaust line 4 Circulating gas exhaust line 5 Circulating gas exhaust line 6 Heat exchanger 7 Pipe line 8 Filter 9 Pipe line 10 Exhaust gas exhaust line 11 Pipe line 12 spouted bed reactor 13 conduit 14 filter 15 conduit 16 chimney 17, 18 rotary cooler 19 conduit 20 filter 21 individual fresh air supply 22 exhaust fan 23 exhaust fan 24 mechanical vortex mixer 25 suction box 26 suction box 26 suction box 25.1 fixed separation part 27 variable separation part 28 of suction box 25.2 drop 29 fixed separation part of exhaust gas exhaust pipe

Claims (9)

A method for sintering iron oxide-containing materials in a sintering machine, wherein a sintering mixture containing solid fuel is ignited, an oxygen-containing gas is passed through the sintering mixture, and a high temperature sintered product Is cooled after dropping, part of the waste gas is returned to the sintering machine as a circulating gas with a high concentration of harmful substances, and another waste gas part is exhausted as an exhaust gas with a low concentration of harmful substances. The dust contained therein is heated before being discharged, and the dust generated in the equipment space and during cold sieving is sucked and removed. By changing the process surface (sintering belt), the circulation gas and exhaust gas The entire waste gas volume is divided into two, and the intersection between the circulation gas suction and exhaust gas suction is selected so that the maximum waste gas volume is circulated and guided without compromising the sintering quality and performance. And taken out Thermal energy of the ring gas is utilized to heat the exhaust gas, H ₂ SO ₄ heated to a temperature of to avoid falls below the dew point is performed, provided that from the mixing temperature This temperature is generated during the discharge of the entire waste gas volume A method characterized by low.   The oxygen-containing gas that is passed through the sintering mixture is composed of sucked ingress air and fresh air that is supplied separately, and fresh oxygen that is supplied separately if the amount of oxygen provided by the intrusion air is sufficient 2. A method according to claim 1, characterized in that the quantity is adjusted to a minimum value.   Method according to claim 2, characterized in that the minimum value is equal to zero.   When the suction of the cold sieving area and the suction of the equipment space are performed separately and fresh air is supplied separately, the sucked cold sieving gas is sent to the sintering mixture as an oxygen-containing gas, and the sintering mixture 4. The method according to claim 1, wherein the filter is used as a filter for entrained dust.   2. A method according to claim 1, characterized in that the amount of circulating gas returned is evenly distributed throughout the sintering belt.   2. Method according to claim 1, characterized in that the suction performed in the dropped area of the sintered product is coupled with the suction of the equipment space.   7. A method according to claim 6, characterized in that the thermal energy contained in the suction gas of the sintered product is used energetically.   A sintering machine for sintering iron oxide-containing materials, comprising a sintering belt, a suction box, an ignition furnace, a sintered product cooler, an exhaust fan, a filter and piping. In the sintering machine, the suction box (25.2) is provided with a slider for changing the suction relationship in the crossing region between the circulating gas suction and the exhaust gas suction, and the circulating gas exhaust line ( 5) The discharge side of the heat exchanger (6) is arranged in the inside, and the suction side of the heat exchanger (6) is arranged in the exhaust gas discharge pipe (10). 12) is provided in the latter stage of the heat exchanger. 9. When fresh air is supplied separately (21), an air exhaust for sending an oxygen-containing gas onto the sintering mixture is used as a cold sieving zone suction collector. The sintering machine described in 1.

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