JP2010096491A - Raw material drying device and method of drying raw material by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raw material drying device and a method of drying raw materials by using the same, capable of being used for drying a large amount of raw materials charged into a blast furnace and the like, and continuously drying the raw materials. <P>SOLUTION: This raw material drying device includes a raw material receiving tank 2 and a drying tank 3 positioned at a lower part of the receiving tank 2 and connected with the receiving tank 2 through a chute 4, and further includes an air supply port 5 for supplying a drying gas into the drying tank, and a discharge port 8 for discharging the raw materials, formed at a lower part of the drying tank 3, and an exhaust port 7 formed at an upper part of the drying tank 3 for sucking the drying gas in the drying tank 3. A state that the raw materials are charged into the chute 4 at all times, is kept when the raw materials are charged into the drying tank from the receiving tank 3 through the chute 4, and the raw materials in the drying tank 3 is dried by the drying gas supplied from the air supply port 5, and discharged from the discharge port 8 by using the raw material drying device, thus the raw materials are dried while preventing inflow of the drying gas in the drying tank 3 from the chute 4 into the receiving tank 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a raw material drying apparatus suitable for drying raw materials charged in a blast furnace such as iron ore and coke, and a raw material drying method using the same.

  In a blast furnace, iron ore, coke, and a coagulant are charged into the furnace from the top of the furnace, and high temperature air or high temperature air enriched with oxygen is blown into the furnace from the bottom of the furnace to burn the coke. Hot metal is produced by reducing and melting iron ore using heat and CO gas generated by combustion. The raw material charged from the top of the furnace is adjusted to a granularity of several mm to several tens of mm and charged into the furnace, so the combustion gas generated by the combustion of coke at the lower part of the furnace is granular filled in the furnace. The gap between the raw materials will rise toward the furnace top.

  Since the heat supply to the raw material is mainly performed by heat transfer from this combustion gas, if the flow of the combustion gas in the furnace is not in an appropriate state, the temperature rise of the raw material becomes unstable, and iron ore is reduced and melted. Will be disturbed.

  Therefore, in order to make the gas flow in the furnace in an appropriate state, the furnace top charging device for charging the raw material of the right particle size to the appropriate position in the furnace when the raw material in the furnace top enters the furnace. And the development of furnace top charging methods are underway.

  However, even if such a raw material charging apparatus and method are elaborated, if the powder is mixed into the raw material itself or the amount of powder discharged outside the furnace accompanying the blast furnace gas is reduced As a result, the amount of powder entering the raw material packed bed in the furnace increases, and a portion having high ventilation resistance is generated in the entire packed bed or locally, making it difficult to optimize the gas flow described above.

  The raw materials used in the blast furnace are stored in an open-air storage area called a yard once manufactured and directly sent to the blast furnace raw material tank after grain size adjustment after being manufactured in a sintering machine or coke oven. After that, this material is collected again and sent to the blast furnace raw material tank, and some iron ore is stored in the yard in granular form after it arrives at the factory. Some raw materials are sent to the raw material tank. Among these raw materials, those that are sent to the blast furnace raw material tank after being stored in the yard are inevitably wet with rainwater when stored in the yard, and the moisture content becomes several mass%. Some raw materials have a water content exceeding 10 mass%.

  In such a raw material with a large amount of water, the powder raw material adheres to the raw material particles due to water, and thus the powder raw material may not be removed even if the particle size is adjusted by a sieve or the like. Moreover, since the powder raw material containing such moisture easily adheres to the sieve net itself, it causes clogging of the sieve, and as a result, there is a problem that sieving of the raw material becomes more difficult.

  When the powder raw material that could not be removed from the granular raw material by the sieve is transported to the top of the furnace while being attached to the granular raw material and charged into the furnace, it is dried by the heat in the furnace and detached from the surface of the granular raw material, As a result, the amount of powder brought in increases.

  In addition, when raw material with a high water content enters the furnace, the sensible heat of the furnace top gas is absorbed and the temperature of the furnace top gas decreases, resulting in the amount of powder entrained by the furnace top gas and discharged outside the furnace. In this case, the amount of powder entering the raw material packed bed in the furnace also increases. The invaded powder flows through the gap between the raw material packed beds in the furnace, and in some cases, a granular raw material accumulates in the gap between the raw materials and causes a phenomenon in which the gas flow in the furnace is inhibited.

  Therefore, by removing the powder raw material and moisture adhering to the blast furnace raw material as described above, the operation of the blast furnace can be stabilized, the output capacity can be increased, and the reducing material ratio can be reduced.

  Therefore, it can be said that the technology for removing the powder raw material and moisture adhering to the blast furnace raw material is as important as the raw material charging technology into the blast furnace furnace.

  In order to remove the powder raw material and moisture adhering to the blast furnace raw material, after supplying the heated gas into the hopper for storing the blast furnace raw material and drying the raw material, the powdery portion is removed by sieving and charged into the blast furnace. A drying preheating apparatus for blast furnace raw materials is known.

JP 2007-254837 A JP 2007-247914 A

Edited by Saburo Kamei “Theory and Calculation of Chemical Machines (2nd edition)” Sangyo Tosho 1980, p. 370-379

  If the drying preheating apparatus described in Patent Document 1 is used, it is easy to remove moisture from the blast furnace raw material, and the amount of powder raw material brought into the blast furnace is reduced by removing the powder raw material by sieving. By optimizing the gas flow inside, it can greatly contribute to the stable operation of the blast furnace. This drying preheating device has a heated gas supply device and an exhaust device, and forcibly circulates the heated gas into the raw material. In order to suck the heated gas effectively, a hopper Except at the time of raw material charging into the inside, it is preferable to close the charging port, which is an opening for charging the raw material, using a lid or the like, not corresponding to the operation mode of drying while charging the raw material, There is a problem that it is difficult to continuously dry the raw material.

  Therefore, the object of the present invention is to solve such problems of the prior art and can be used to dry a large amount of raw material charged in a blast furnace or the like, and can continuously dry the raw material. An object of the present invention is to provide a raw material drying apparatus and a raw material drying method using the same.

The features of the present invention for solving such problems are as follows.
(1) A raw material receiving tank and a drying tank located below the receiving tank and connected to the receiving tank via a chute, and a drying gas on the bottom and / or lower side of the drying tank And an exhaust port for sucking the drying gas in the drying tank at the upper surface and / or the upper side of the drying tank. A raw material drying device.
(2) The raw material drying apparatus according to (1), wherein a lower end portion of the chute protrudes into the drying tank.
(3) The raw material drying apparatus according to (1) or (2), further including a heating device that heats a lower portion of the drying tank.
(4) The raw material drying apparatus according to any one of (1) to (3) is used, the raw material is charged into a receiving tank, the raw material is filled into the drying tank through a chute, and the drying tank When the raw material in the inside is dried with the drying gas supplied from the air supply port and discharged from the discharge port, the chute of the drying gas in the drying tank is always maintained while the chute is filled with the raw material. A method for drying a raw material, characterized in that it prevents inflow into a receiving tank.

  In addition, the bottom face and / or the lower part of the side face of the drying tank corresponds to a portion where the raw material is filled in the drying tank. On the other hand, the upper surface and / or the upper part of the side surface of the drying tank corresponds to a portion where the raw material is not filled in the drying tank.

  According to the present invention, it is possible to continuously remove moisture from the raw material, and the operation efficiency is improved. Thereby, a large amount of raw materials can be dried at a low cost.

  By drying the raw material, moisture can be reduced and the powder raw material can be removed reliably, and the gas flow in the furnace can be optimized to greatly contribute to stable operation of the furnace.

Schematic which shows one Embodiment of the drying apparatus of the raw material of this invention. Schematic which shows the state which inserted the raw material in the drying apparatus of the raw material of this invention. Explanatory drawing of the layer thickness setting method in a drying tank. Mass reference humidity chart showing the relationship between absolute humidity and temperature. Explanatory drawing which shows the upper part of a drying tank. Schematic which shows one Embodiment of this invention. Schematic which shows other one Embodiment of the drying apparatus of the raw material of this invention. Schematic which shows other one Embodiment of the drying apparatus of the raw material of this invention. Schematic of the horizontal cross section of FIG. The graph which shows the relationship between the moisture content of a raw ore, and the mixing rate of the fine ore with a particle size of 3 mm or less. The graph which shows the output capacity increase by a furnace top gas temperature rise. The graph which shows the relationship between raw material water | moisture content, the amount of powder mixing, and a reducing material ratio. Schematic which shows an example of the conventional drying apparatus of a raw material.

  When the raw material is dried using a conventional hopper for storing the raw material in order to dry the raw material, for example, as shown in FIG. A material having an air supply port 22 to be supplied and a discharge port 23 for discharging the raw material, and having a raw material charging port 24 and an exhaust port 25 for sucking the drying gas in the hopper above the hopper 21, The raw material is charged into the hopper 21 from the charging port 24, the lid 26 is placed on the raw material charging port 24, the drying gas is supplied from the air supply port 22, and exhausted from the exhaust port 25 to dry the raw material. The dried raw material is discharged from the discharge port 23. When a large amount of raw material is dried, in order to subsequently dry the raw material, the lid 26 is opened and a new raw material is charged into the hopper 21, which basically becomes a batch type operation mode. .

  On the other hand, if the raw material drying apparatus of the present invention is used, the drying gas can be circulated in the raw material without using a lid, so that the raw material can be continuously dried. One embodiment of the raw material drying apparatus of the present invention is shown in FIG.

  FIG. 1 is a side view of a raw material drying apparatus. The raw material drying apparatus 1 includes a raw material receiving tank 2, a drying tank 3 positioned below the receiving tank 2, and a chute 4. And the drying tank 3 are connected via a chute 4. The drying tank 3 has an air supply port 5 for supplying a drying gas into the drying tank 3 and a discharge port 8 for discharging the raw material. In the present embodiment, a hot air annular tube 9 is connected to the air supply port 5, and a feeder 6 is installed at the discharge port 8. An exhaust port 7 for sucking the drying gas in the drying tank 3 is formed in the upper part of the drying tank 3. The exhaust port 7 can be formed not on the side surface of the drying tank 3 but on the upper surface.

  The number of drying tanks 3 can be arbitrarily set for one receiving tank 2. There may be one drying tank or a plurality of drying tanks for one receiving tank. In actual operation, 1 to 4 drying tanks are appropriate for one receiving tank.

  Next, the raw material drying method when the drying apparatus of FIG. 1 is used will be described with reference to FIG.

  For example, when drying a raw material used in a blast furnace such as iron ore or coke, the raw material is supplied at a constant speed from the upper opening of the receiving tank 2 of the drying apparatus 1, and the raw material 10 a is charged into the receiving tank 2. Then, the raw material 10 c is filled into the drying tank 3 through the chute 4. The raw material 10c in the drying tank 3 is discharged from the discharge port 8 by the feeder 6 at a constant speed. In this way, the raw material is continuously supplied to the drying tank 3, and at that time, a sufficient amount of the raw material 10 is received so that the raw materials 10 b and c are continuously stacked from the drying tank 3 into the chute 4. The tank 2 is charged. Here, the receiving tank 2 needs to have a sufficient size so as to absorb a variation in the raw material charging speed and always supply a sufficient amount of the raw material to the chute 4.

  The raw material 10 c in the drying tank 3 is dried with a drying gas supplied (indented) from the hot air annular tube 9 through the air supply port 5. The drying gas is sucked and discharged from the exhaust port 7. During drying with the drying gas, the state where the chute 4 is always filled with the raw material 10b is maintained to prevent the drying gas in the drying tank 3 from flowing from the chute 4 to the receiving tank 2. To do. In FIG. 2, the raw material flow is indicated by a thick solid arrow, and the drying gas flow is indicated by a dotted arrow.

  At the same time, a cavity is formed in the upper part of the drying tank 3 in accordance with the angle of repose of the raw material 10c. By disposing an exhaust port in this portion, the raw material is sucked into the flow path of the exhaust port so Can be prevented.

  As described above, the raw material charging section of the drying tank is sealed with the raw material charged from above, and the drying gas in the drying tank is exhausted by a draft effect by a forced exhaust device or an exhaust tower. By sucking from the mouth 7, the pressure at the upper end of the chute 4 is made negative, and blowing of the drying gas from the raw material charging portion can be completely prevented. Moreover, about the discharge port part in a drying tank, the amount of blowing from the discharge port of a raw material can be suppressed by lengthening the distance of the air supply port 5 and the discharge port 8 of a raw material. In the case where a blowout occurs, it is preferable to forcibly suck the entire amount of the blowout with a suction device in the feeder 6 installed below the discharge port 8. Since the drying gas sucked here is accompanied by dried powder, it is desirable to prevent the generation of dust by being diffused into the atmosphere through a dust collector.

  Moreover, it is preferable that the lower end part of the chute 4 protrudes into the drying tank 3. As shown in FIG. 2, when the exhaust port 7 is on the upper side surface of the drying tank 3, if the lower end of the chute 4 is at a high position in the drying tank 3, the exhaust port 7 is blocked by the charged raw material. Since there is a case, it is preferable that the lower end of the chute 4 is protruded into the drying tank 3 with a length sufficient to prevent this. Further, since the charging height (layer thickness) h of the raw material 10c charged into the drying tank 3 is determined at the lower end position of the chute 4, the layer thickness can be arbitrarily set according to the protruding length.

  The layer thickness h which is the charging height of the raw material in the drying tank 3 can be appropriately set in consideration of the drying efficiency of the raw material.

  Below, an example of the method of setting the layer thickness h (= required length) in a drying tank is demonstrated.

FIG. 3 shows general specifications in the case where the raw material entering and leaving the drying tank 3 and the hot air are countercurrent. As shown in FIG. 3, the raw material is anhydrous feeding rate _{W 0,} the water content _{w 1,} enters the drying vessel 3 at a temperature tm _1, the drying chamber over anhydrous feeding rate _{W 0,} the water content _{w 2,} temperature tm ₂ The hot air enters the drying tank at a flow rate G ₀ , humidity H ₂ and temperature t ₂ , and exits the drying tank at a flow rate G ₀ , humidity H ₁ and temperature t ₁ .

  Here, the upper part (I) of the drying tank 3 is a portion corresponding to the raw material preheating period. The raw material preheating period is a period until the raw material temperature becomes steady with respect to the drying conditions, and the raw material temperature is increased by heating. However, it loses sensible heat and drops in temperature, and the water is hardly evaporated.

  Further, the central part (II) of the drying tank 3 is a part corresponding to the surface evaporation period. In the surface evaporation period, the raw material temperature is always constant as long as liquid water is present on the raw material surface, and the inflow heat is all evaporated. It is a period during which the water evaporation rate (= drying rate) is constant, and the water content decreases in proportion to the drying time.

  Further, the lower part (III) of the drying tank 3 is a portion corresponding to a reduced rate drying period, and the reduced rate drying period is a period in which moisture evaporation and raw material heating are performed, and liquid water does not exist on the raw material surface. As the raw material temperature rises, the inflow heat quantity decreases and the drying speed gradually decreases. Finally, the moisture content and raw material temperature that are in equilibrium with the drying conditions are reached and the drying is terminated.

  Based on the moisture and heat balance between the raw material and hot air and the heat transfer capacity coefficient calculated using the empirical formula, obtain the volume of the drying tank in each of the above (I), (II) and (III) parts. Then, the total volume of each volume is obtained.

Further, the cross-sectional area of the drying chamber, for example according to the description of Patent Document 2, based on the following constraints can be determined by dividing the hot air flow rate G ₀ at a predetermined intracisternal hot air mass velocity.
L> W / 2
Where, L: horizontal distance between the position where the moving direction of the jet of the hot gas for drying (hot air) changes from the horizontal direction to the vertical direction and the outlet (air inlet), W: between the outlet (air inlet) Horizontal distance.

The required length of the drying tank can be determined by dividing the total volume determined above by the cross-sectional area of the drying tank determined above. The moisture mass balance between the raw material and the hot air is expressed by the following equation.
_{W 0 (w 1 -w 2)} = G 0 (H 1 -H 2)
The layer thickness h, which is the raw material charging height, can be set from the required length of the drying tank thus obtained.

  In addition, although the volume of the drying tank 3 can be calculated | required theoretically by a well-known method (for example, refer nonpatent literature 1), it shows below about the view of layer thickness at the time of using a mass reference | standard humidity chart.

  FIG. 4 is a mass reference humidity chart based on 1 kg of dry air and a total pressure of 760 mmHg, and shows the relationship between absolute humidity and temperature. When considering a process similar to that of the present invention in which hot air is generated by heating the air, and this is passed through a packed bed to be dried and dried, the air at the point indicated as “atmosphere” in FIG. When heated by a heating device or the like, the state point moves to the point indicated by “hot air”. Thereafter, when heat is exchanged with the object to be dried in the drying tank and the evaporated water is accompanied, the state point moves on the adiabatic cooling line in the direction of decreasing temperature. Assuming that the packed bed thickness is sufficient, the relative humidity of the air continues to rise and reaches saturation with the passing distance in the packed bed, reaching the “exhaust (saturated)” point in FIG. The dry water content is maximized with a packed bed thickness such that the drying tank outlet side (exhaust port position) is in this state. If the thickness of the packed bed is increased further, the temperature of the hot air is further lowered by heat exchange with the object to be dried, so that the point moves to the point of “(overlayer thickness)” in FIG. The amount of water decreases. When the packed bed thickness is further increased, the temperature finally reaches the atmospheric temperature, and under this condition, the effect of raising the temperature by the heating device is lost.

  Therefore, it is desirable to set the layer thickness so that the exhaust gas is in the moisture saturation range, and the exhaust temperature at the exhaust port of the heated gas is calculated from the supply temperature at the heated gas supply port and the humidity of the heated gas. It is desirable to keep the layer thickness so that the adiabatic saturation temperature is high. When the layer thickness is such that the exhaust temperature of the heated gas becomes the adiabatic saturation temperature, a wet zone is formed on the upper part of the raw material in the drying tank. The wet zone is an area where the raw material is wet due to condensation of the heated gas, and when powder generated by drying of the raw material rises in the drying tank accompanying the heated gas, it is again converted to the raw material by moisture. It is made to adhere and it prevents that powder with a heated gas is discharged | emitted from an exhaust port. The powder trapped by adhering to the raw material is dried again in the lower part in the drying tank and discharged from the feeder together with the bulk material.

  In the region where the layer thickness is insufficient to reach the moisture saturation of the heated gas (“exhaust air (saturation)” point in FIG. 4) (layer thickness <the moisture saturation range of the exhaust gas), a wet zone that traps dry powder Is not sufficiently formed, and dry powder is accompanied by the heated gas to be exhausted, so that it is essential to install a dust collector. In addition, since the heating gas has not reached saturation, the amount of moisture removed per heating gas mass, that is, the dry moisture amount is small.

  When the layer thickness increases, the heat gas temperature decreases due to heat exchange with the ore, and eventually reaches the dew point. As the layer thickness further increases, the heating gas temperature becomes lower than the dew point, and the heating gas temperature decrease due to heat exchange with the ore is offset and offset by the heating gas temperature increase due to condensation, so the gradient becomes gentler.

  When the layer thickness is equal to or greater than the moisture saturation range of the exhaust gas, a “wet zone” is formed and the dried powder is trapped, so that the installation of a dust collector can be omitted.

  However, if the layer thickness is set so that the layer thickness is equal to or greater than the moisture saturation range of the exhaust gas, the higher the layer thickness, the lower the temperature of the exhaust gas, and the total amount of water that the heated gas can take away. In addition, the moisture content of the raw material after drying tends to increase. Instead, since the sensible heat of the excess drying gas is consumed for the temperature rise of the raw material, the temperature of the raw material after drying rises as the latent heat of water evaporation decreases. After leaving the drying tank, in the process of transportation to the blast furnace, if drying in the atmosphere can be expected, or if the raw material can be used in a blast furnace with a short transportation time, the top Part of the effect of lowering the amount of powder brought in due to temperature rise and moisture reduction can be enjoyed, but the most efficient is to reduce moisture to the maximum in the drying tank. It is not preferable to set the moisture saturation range.

  Therefore, the condition where the layer thickness is approximately equal to the moisture saturation range of the exhaust gas is most efficient for drying, and it is not necessary to install a dust collector. However, in the case of an actual process, since the preconditions such as moisture and temperature of the raw material are not constant but greatly fluctuate, it is necessary to have a structure in which the flow rate and temperature of the heating gas can be controlled with high accuracy. For example, when exhaust gas in another process is used as a heating gas for drying, as described in Japanese Patent Application No. 2008-245541 proposed by the present inventors, a nozzle communicating with an annular pipe in the exhaust gas recovery device There is a method of controlling the heating gas flow rate without affecting other processes by making the structure in a well-balanced manner and taking into account the cross-sectional area ratio between the nozzle and the exhaust pipe so as not to change the exhaust gas speed. .

The installation positions of the air supply port and the exhaust port will be described with reference to FIG. The raw material drying apparatus of the present invention has an air supply port at the bottom and / or lower side of the drying tank and an exhaust port at the upper and / or upper side of the drying tank. The exhaust port is arranged at a portion where the raw material is not filled in the drying tank in the portion where the raw material is filled. FIG. 5 shows the upper part of the drying tank 3 in FIGS. 1 and 2, but the radius of the chute 4 is r _0, the radius of _the drying tank 3 is r ₁ , and the protrusion length of the chute 4 into the drying tank 3 is x _a. If the angle of repose of the raw material is θ, x _b in FIG.
x _b = tan θ · (r ₁ −r ₀ )
And
x _c = x _a + x _b = x _a + tan θ · (r ₁ −r ₀ )
Since the upper surface of the drying vessel, and / or the exhaust port side to the height position of the x _c from the top, the bottom surface of the drying vessel, and / or a position lower than the length down position from the top surface x _c It is only necessary to install an air supply port on the side of the. The angle of repose θ is 25 to 30 ° for pellets, 30 to 35 ° for sintered ore ore (raw ore), and about 35 to 40 ° for coke. For example, about 25 to 40 ° may be used.

  In FIG. 2, the raw material 10 c tends to adhere to the inside of the inclined portion 11 of the side wall at the bottom of the drying tank 3 and the feeder 6. About the former, it is preferable to have a heating apparatus which heats this part. The lower part of the drying tank 3 can be heated by arranging a pipe in a spiral shape at the lower part of the drying tank 3 and flowing a gas for drying used for drying the raw material or other high-temperature gas such as water vapor into the pipe. For the latter, the adhesion part vibrates, and if it is difficult to install a heating device, other measures such as attaching a low-roughness polymer liner to the part in contact with the raw material are implemented. It is preferable.

  The dried raw material discharged from the feeder 6 is used by separating and removing the powdery portion with a sieving facility or the like and charging the raw material of the coarse grain portion into a blast furnace or the like.

  In order to supply the drying gas into the drying tank 3, it is preferable to increase the pressure of the drying gas using an air supply device such as a booster fan. The drying gas generated by the hot air generation source is pressurized by an air supply device and is supplied into each drying tank 3. If a flow control valve is installed for each air supply port 5 of each drying tank 3, when supplying the drying gas to a plurality of drying tanks 3 simultaneously with one air supply device, the amount of each air supply is adjusted. It is possible and suitable. One or a plurality of air supply ports 5 of each drying tank 3 may be used.

  In order to suck the drying gas in the drying tank 3 through the exhaust port, it is preferable to use an exhaust device having a suction fan or the like, and it is preferable to exhaust the exhaust gas from the exhaust port 7 through a dust collector. In addition, by forming a raw material layer wet zone in the raw material layer, there is an effect of trapping the generated dust, so the draft is replaced by the draft effect by the exhaust tower, and the exhaust is diffused to the atmosphere without going through the dust collector In this case, in the design stage of the drying tank 3, the layer thickness for keeping the wet zone is kept sufficiently, and the raw material moisture is reduced by measuring the exhaust gas temperature, moisture, etc. during operation. It is necessary to control the retention of the wet zone by detecting the tendency of the disappearance of the wet zone due to, etc., and by adding moisture to the drying tank 3 or during feeding, lowering the feed rate, or lowering the feed amount of raw materials. To do.

  By sucking the drying gas in the drying tank 3 to the exhaust port, the drying gas sent from the air supply port 5 of the drying tank 3 rises in the drying tank 3 and is discharged from the exhaust port 7. A flow is formed, and the raw material 10c is easily dried with the drying gas. Therefore, from the viewpoint of drying, the position of the air supply port 5 for supplying the drying gas into the drying tank 3 is preferably provided as low as possible on the side wall of the drying tank 3.

  As a drying gas used for drying the raw material, various heating gases (exhaust gas) generated in a factory can be used. In particular, exhaust gas that is discharged at a relatively low temperature of about 300 ° C. or less and difficult to recover heat can be used effectively. When drying blast furnace raw materials, a sintering machine is often installed in the vicinity, so using the cooler exhaust gas from the sintering machine is optimal because it has a short air supply path and less heat dissipation, and is particularly preferable. . In addition, a drying gas can be appropriately selected according to the location conditions of each factory such as blast furnace hot stove exhaust gas and rolling heating furnace exhaust gas. Of course, a combustion furnace, an electric furnace, or the like may be installed to generate a drying gas, and a dedicated hot air generation source may be used.

  When drying the blast furnace raw material, the temperature of the drying gas is preferably 60 ° C. or higher at the air supply port 5, and more preferably 80 ° C. or higher. However, if the temperature exceeds 300 ° C., it is necessary to install a booster fan that can handle high-temperature gas, and heat resistance of the equipment around the raw material drying device also becomes a problem, which may increase the equipment cost. Therefore, it is preferable to set it as 300 degrees C or less. Considering the purpose of drying, 200 ° C. or lower is sufficient.

  One or more air supply ports 5 are installed on the bottom and side surfaces of the drying tank 3. In order to dry and preheat the raw material in the drying tank 3 uniformly, it is preferable to arrange a plurality of air supply ports 5 in the circumferential direction of the drying tank 3. Moreover, it is preferable to arrange the plurality of air supply ports 5 at equal positions in the circumferential direction. In order to arrange a plurality of air supply ports 5 in the circumferential direction of the drying tank 3, as described above, a hot air annular pipe is provided around the drying tank 3, and drying air is supplied to the air supply port 5 through the hot air supply pipe. It is preferable to supply gas. The hot-air annular tube serves as a reservoir, and the drying gas can be supplied from each air supply port 5 evenly.

  In order to increase the processing amount of the raw material to be dried, the drying tank 3 can be increased in size. However, as the equipment height increases, the cost increases significantly, so it is desirable to increase the cross-sectional area of the drying tank 3. However, as the cross-sectional area increases, it becomes more difficult to uniformly dry the raw material 10c in the drying tank 3 to the center, so that the cross-sectional area is increased by arranging a plurality of raw material drying apparatuses 1 as shown in FIG. Can be made. It is desirable that raw materials are charged into each drying device 1 using a tripper conveyor 19 or the like.

  When it is difficult to arrange a plurality of drying apparatuses due to location conditions or the like, for example, the raw material drying apparatus 1 shown in FIGS. 7 and 8 can be used. By arranging the air supply port 5 at the center of the drying tank 3 and blowing the drying gas from the outer periphery and the center, the cross-sectional area per drying tank can be expanded. FIG. 9 is a schematic diagram in a horizontal section of the air supply port position of FIGS. As shown in FIGS. 7 and 8, the receiving tank 2 and the drying tank 3 can be connected by a plurality of chutes.

The total amount of raw ore 5600 t / d used in a blast furnace with an internal volume of 5153 m ³ was dried using the same raw material drying apparatus as shown in FIG. 1, and then sieved.

(Hot air condition)
As the hot air for drying, a part of the cooler exhaust gas 200 ° C. of an adjacent sintering machine was used, and this was pressurized by an introduction fan and supplied to each drying tank as a drying gas. FIG. 10 shows the relationship between the water content of raw ore and the mixing rate of fine ore having a particle size of 3 mm or less (−3 mm). Since the average moisture content of raw ore was 4 mass%, the calorific value for reducing the moisture content to 2 mass%, which reduces the powder mixing rate and maximizes the sieving efficiency, was calculated to be 160000 m ³ (standard condition) It was set as the equipment which can blow in hot air of / H.

(Drying tank conditions)
There were 4 drying tanks according to the site conditions. The diameter of the drying gas at each air inlet is 20 m / s, and the superficial gas velocity in the tank is 0.4 m / s. A 400 mmφ air inlet was installed. In order to make the quality after drying uniform, each air supply port has a jet of drying gas ejected from the air supply port overlapping at least part of the discharge port in plan view. Arranged in a position that does not overlap. The drying tank was provided with a reduced diameter portion connected to the discharge port, and the air supply port was disposed within the reduced diameter portion. A blowing nozzle was attached to the tip of the air supply port. The eight air supply ports were horizontally arranged at equal intervals with two each facing each other. For each of the two air supply ports facing each other, the horizontal distance of the front end of the air supply port is 3000 mm, and the position and air supply port where the moving direction of the jet of the drying gas changes from the horizontal direction to the vertical direction in the drying tank The horizontal distance from the tip was 1700 mm.

(Drying, heating effect)
The raw ore not dried had a moisture content of 4 mass% and 25 ° C, but the dried raw ore had a moisture content of 1.9 mass% and a temperature of 60 ° C, and obtained the desired moisture content and temperature after drying. I was able to.

(Powder contamination reduction effect)
Furthermore, the mixing rate of the powder of 3 mm or less after sieving with a 5 mm sieve was 3.2 mass% for the raw ore that was not dried, whereas the raw material drying preheating of the present invention The raw ore dried by installing the apparatus was 1.5 mass%, and the amount of powder mixed into the blast furnace raw material was almost halved.

(Blast furnace production increase effect)
While continuing operation at a maximum production capacity of 2.35 t / d / m ³ in the blast furnace, drying of the entire raw ore used was started. As a result, the furnace top gas temperature that restricted the production capacity of the blast furnace increased from 120 ° C. to 135 ° C. as shown in FIG. Therefore, as a result of increasing the oxygen enrichment rate during blowing to the blast furnace and increasing the production amount until the furnace top gas temperature becomes 120 ° C. again, the amount of powder discharged from the furnace top does not decrease and the output ratio is 2 .43 t / d / m ³ . That is, the production capacity could be increased by 0.08 t / d / m ³ .

(Blast furnace reducing material ratio reduction effect)
Furthermore, the reduction in the amount of mixed powder reduces the airflow resistance in the blast furnace and makes the gas flow velocity distribution in the blast furnace uniform, increasing the gas utilization rate from 49.8% to 50.2% as shown in FIG. However, the hot metal temperature also increased considerably and the furnace heat became excessive, so that the reducing material ratio could be reduced from 491 kg / t to 489 kg / t.

DESCRIPTION OF SYMBOLS 1 Raw material drying apparatus 2 Receiving tank 3 Drying tank 4 Chute 5 Air supply port 6 Feeder 7 Exhaust port 8 Discharge port 9 Hot air annular pipe 10 (10a, 10b, 10c) Raw material 11 Inclined part of side wall 19 Tripper conveyor 20 Sieving equipment 21 Hopper 22 Air inlet 23 Outlet 24 Raw material inlet 25 Exhaust outlet 26 Lid h Charge height (layer thickness)
r ₀ chute radius r ₁ drying tank radius x _a , x _b , x _c length θ angle of repose of raw material

Claims (4)

  A raw material receiving tank, and a drying tank located below the receiving tank and connected to the receiving tank via a chute, and a drying gas is provided on the bottom surface and / or the lower side of the drying tank. It has an air supply port for supplying it into the inside and a discharge port for discharging the raw material, and has an exhaust port for sucking the drying gas in the drying tank at the upper surface and / or the upper side of the drying tank. Raw material drying equipment.   2. The raw material drying apparatus according to claim 1, wherein a lower end portion of the chute protrudes into the drying tank.   The raw material drying apparatus according to claim 1, further comprising a heating device that heats a lower portion of the drying tank.   Using the raw material drying apparatus according to any one of claims 1 to 3, the raw material is charged into a receiving tank, the raw material is filled into the drying tank through a chute, and the raw material in the drying tank is When drying with the drying gas supplied from the air supply port and discharging from the discharge port, the state where the raw material is always filled in the chute is always maintained and the receiving gas chute in the drying vessel is received. A method for drying a raw material, characterized in that the inflow of the raw material is prevented.

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