Method for measuring and managing the level of mixed raw materials in the mixing section of a mixing and molding machine, and mixing and molding machine

Abstract

To provide a measurement device of a raw material level and a method for managing the raw material level in a kneading part in order to stably performing continuously operation about a continuous type kneading part for kneading a kneading raw material while conveying it in a horizontal direction by using kneading blades and a screw attached to a one-axial or multiaxial shaft installed horizontally, like a kneading part used in a nonfired agglomerated ore kneading and molding machine.SOLUTION: A method for measuring and managing a kneading raw material level in a kneading part in a kneading and molding machine and a kneading and molding machine measure a kneading raw material level at an inlet side of a kneading raw material consolidation part in front of a dam, and / or a water addition nozzle installation position, wherein a kneading raw material input port, a connection pipe for guiding the kneading raw material to a kneading part, a kneading machine with a shaft with an impeller arranged, and a dam with the kneading raw material extruded thereto are sequentially arranged.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for measuring and managing the level of mixed raw materials in a mixing section of a mixing and molding machine used for producing unbaked carbon-containing agglomerated ore in steelmaking, and to a technique relating to the mixing and molding machine. [Background technology]

[0002] In a blast furnace, raw ore and lump coke are charged from the top of the furnace while air is blown from the bottom of the furnace. The reducing gas generated from the lump coke and the blown air is blown from the bottom to the top of the furnace, reducing and dissolving the iron oxide in the raw ore. In order to ensure the ventilation of the reducing gas in the furnace, the raw ore is required to have a strength that does not powder in the furnace. For this reason, raw materials that have been fired at high temperatures in advance, such as sintered ore and fired pellets, are usually used in blast furnaces.

[0003] In response to this, non-calcined carbon-bearing agglomerates have been developed that use hydraulic binders such as cement to reduce the energy consumption required for calcination and thus the amount of carbon dioxide gas, a greenhouse gas, generated. As the raw material for non-calcined carbon-bearing agglomerates, it may be possible to use inferior fine ores that have been considered to have low sinterability and are difficult to mold into agglomerates.

[0004] Furthermore, as described in Patent Document 1, coke fines, which has a small particle size and is difficult to directly charge into a blast furnace, and anthracite, which is inexpensive but has low caking properties and is difficult to convert into coke, can be blended as reducing agents into unsintered carbon-containing agglomerates, and it is expected that the reducing agent ratio of the blast furnace can be reduced.The latest findings reveal that the effect of reducing the reducing agent ratio in a blast furnace can be maximized by setting the carbon content (TC) incorporated in unsintered carbon-containing agglomerates to 120-200 mass% (equivalent to 15-25 mass% in TC) of the theoretical carbon amount required to reduce iron oxide to metallic iron.

[0005] The hydrates in the unsintered carbon-bearing agglomerates formed by the hardening reaction of the hydraulic binder are decomposed by an endothermic reaction when heated to about 400°C or higher in a blast furnace. For this reason, the strength of the unsintered carbon-bearing agglomerates is significantly reduced in the furnace, and there is a concern that they may be pulverized. If the unsintered carbon-bearing agglomerates are pulverized in the blast furnace, the air permeability in the furnace is deteriorated, so a certain level of hot strength is required for unsintered carbon-bearing agglomerates for blast furnaces. On the other hand, if a large amount of hydraulic binder is used to ensure hot strength, the amount of reducing material input to the blast furnace is increased to compensate for the heat lost by the endothermic reaction, and the cost of molten pig iron increases. Therefore, in the manufacturing method of unsintered carbon-bearing agglomerates, a manufacturing method that can achieve the hot strength required for blast furnace use with as little hydraulic binder as possible is required.

[0006] Recently, a manufacturing method that can achieve the hot strength required for blast furnace use has been developed, which uses a vacuum extrusion method to manufacture unbaked carbon-containing agglomerates for blast furnace use.

[0007] The vacuum extrusion molding machine for non-calcined carbonaceous agglomerates consists of a first extrusion section (mixing section) and a second extrusion section (extrusion molding section) as shown in the example of Figure 1. In addition, the area from the outlet of the first extrusion section (mixing section) to the second extrusion section (extrusion molding section) is vacuum degassed to below -40kPaG in order to ensure the necessary strength of the molded body, and in order to continue vacuum extrusion molding stably, the filling rate of the mixed raw materials inside the mixing section and the extrusion molding section must be maintained within an appropriate range. R The appropriate value for the filling rate of the kneading material in the kneading section is 50% by volume or more and 90% by volume or less, and optimally 50% by volume or more and 65% by volume or less. The appropriate value for the filling rate of the kneading material in the extrusion section is 50% by volume or more and 95% by volume or less, and optimally 50% by volume or more and 60% by volume or less.

[0008] In an apparatus for kneading and molding wet powder as in this process, the raw material level in the container rarely fluctuates uniformly, and local fluctuations in the raw material level often lead to fluctuations in the raw material level of the entire apparatus. Therefore, in order to effectively suppress fluctuations in the raw material filling rate in the apparatus and manage it within an optimal range, it is important to quickly detect the raw material level fluctuation at the location where the fluctuations in the raw material level start and take operational action.

[0009] However, in the prior art, as described in Patent Documents 2 and 3, there are many techniques for detecting the internal liquid level in a vertical mixer or kneader, but there are few techniques for detecting the raw material level in a kneading section that continuously mixes and kneads the raw materials while transporting them in a horizontal direction, as used in non-sintered carbon-containing agglomerate manufacturing equipment. Also, as described in Patent Document 4, there is a prior invention for detecting and managing the raw material level inside a device (screw pump) that transports the raw material in a horizontal direction, similar to this process, but the raw material level inside the device is considered to be uniform, and it is not a technology that assumes a local rise in the raw material level inside the device, as in this process.

[0010] Further, the kneading and molding of non-calcined carbon-containing agglomerates will be specifically described. In the kneading and molding of powder, the raw material to be kneaded and, if necessary, water are put into a kneader, and the powder raw material is kneaded by the kneading blades and screws in the device. After that, the raw material is extruded and molded by an extruder in a subsequent process. There are various types of kneading and molding devices, but when kneading and molding the raw material continuously and in large quantities (for example, several tons / h or more), generally, as shown in the example of Figure 1, a kneading section 4 of a type that kneads the raw material while continuously conveying it horizontally using kneading blades 4c (sometimes screws) attached to a horizontally installed single-shaft or multi-shaft shaft 4b, and an extrusion molding section 7 of a type that extrudes the raw material to be kneaded from an extrusion molding dam 7d by extrusion molding blades 7c (sometimes screws) and molds it is often used. In the example shown in FIG. 1, the extrusion molding unit 7 conveys the raw material to be mixed by an extrusion molding blade 7c inside a casing 7a, and this extrusion molding blade 7c is provided on a rotatable extrusion molding shaft 7b.

[0011] In the kneading section 4 as shown in the example of FIG. 1, water is added to the raw material by using one or more water-adding nozzles 5 of any shape installed at any position in the upper part of the kneading section 4 (including the inside of the connecting pipe 3). In addition, a weir 4d of various shapes (any shape is acceptable as long as it provides discharge resistance, such as a porous plate) is installed on the outlet side of the kneading section 4 to consolidate the raw material. In front of the weir 4d, a raw material consolidation section 4e having an inner diameter narrower than that of the kneading section 4 is arranged so that the raw material is tightly packed in close contact with the weir 4d. The raw material is consolidated in the weir 4d and the raw material consolidation section 4e, and is subjected to a particularly large shear force by the kneading blades 4c, which promotes kneading.

[0012] In addition, as in the example of FIG. 1, when the extrusion molding section 7 is configured with the vacuum degassing from the outlet side of the kneading section 4, the kneaded raw material compressed by narrowing the inner diameter in the kneaded raw material compacting section 4e also plays the role of a material seal to maintain the vacuum degassing conditions. The weir 4d and the kneaded raw material compacting section 4e can have various shapes (for example, the kneaded raw material compacting section 4e is tapered so as to narrow from the inlet side to the outlet side). butThe weir 4a may have a sluice gate, and the weir 4b may be a perforated plate, but their basic functions are the same.

[0013] In a kneading and molding apparatus consisting of a kneading section 4 and an extrusion molding section 7 as shown in Fig. 1, it is necessary to manage the level of the mixed raw material inside the apparatus in both the kneading section 4 and the extrusion molding section 7. In both the kneading section 4 and the extrusion molding section 7, if the level of the mixed raw material is too high, the filling rate of the mixed raw material inside the apparatus will be too high, causing the mixed raw material to overflow from the apparatus or overload the apparatus, making it impossible to continue operation. On the other hand, in both the kneading section 4 and the extrusion molding section 7, if the level of the mixed raw material is too low, the filling rate of the mixed raw material inside the apparatus will be too low, making it impossible to maintain the material seal and maintaining the necessary vacuum degassing conditions.

[0014] Next, the difference in structure between the kneading section 4 and the extrusion molding section 7, which is important for managing the level of the mixed raw material, will be described. The kneading section 4, except for the mixed raw material compaction section 4e that compacts the mixed raw material, has a structure in which the top can be opened and the inside can be observed from the top (open, grating, observation window, easily openable lid, etc.). Therefore, the level of the mixed raw material inside the kneading section 4 can be easily observed from the top of the device. On the other hand, the extrusion molding section 7 is surrounded by strong liners on all sides except the vacuum chamber 6 in order to maintain the mixed raw material compaction and vacuum degassing conditions, and the inside of the device cannot be observed from the top of the device.

[0015] Furthermore, even if an observation window is installed at the top of the vacuum chamber 6 to measure the raw material level inside the extrusion molding section 7, the raw material falling from the outlet side of the kneading section 4 to the extrusion molding section 7 inside the vacuum chamber interferes with the measurement. For example, if an attempt is made to measure the raw material level in the extrusion molding section 7 using a level meter through a sight window installed at the top of the vacuum chamber, the level meter frequently picks up the distance from the sight window to the falling raw material, making it impossible to quantitatively measure the raw material level. For this reason, a method different from that used in the kneading section 4 is required to stably measure the raw material level inside the extrusion molding section 7.

[0016] <Key points for stable operation of kneader> 1) Management of mixed raw materials In general, in order to continue the kneading stably, it is important to maintain and manage the level of the raw material in the kneading section 4 within an appropriate range. For example, if the raw material level is too high, the raw material will overflow from the top of the kneading section 4, making it impossible to continue the operation, or the kneading section 4 will be overloaded and the operation will be stopped. On the other hand, if the raw material level is too low, the water spray from the water adding nozzle will not splash onto the shaft or the kneading blades 4c. of If the blades hit the raw material first, water may not be added evenly to the raw material, or the raw material may not be kneaded stably because the blades 4c do not apply force to the raw material. In such cases, the raw material may be supplied to the subsequent process with insufficient mixing, resulting in a decrease in product yield. of There are concerns that this could lead to declines in production or even shutdowns.

[0017] In a kneading and molding machine as shown in the example of Fig. 1, a large amount of powdered raw material is continuously supplied and discharged, so if the balance between the supply amount and discharge amount of the raw material is lost, the raw material level of the entire kneading and molding machine or a specific part fluctuates in a relatively short time (several tens of seconds to several minutes), making it difficult to control the raw material level. In addition, when mixing raw material whose properties are such that the flowability fluctuates greatly with a small change in the operating conditions (particle size of the raw material, moisture content of the raw material, change in the number of revolutions of the shaft 4b, etc.), fluctuations in the raw material level are particularly likely to occur.

[0018] The reason is that the discharge resistance applied to the raw material by the gate 4d and the conveying force of the raw material by the kneading blade 4c are greatly affected by the change in the fluidity of the raw material. Furthermore, in the case of raw material with a relatively low fluidity (raw material with a high angle of repose), local fluctuations in the raw material level are likely to occur, and this may cause fluctuations in the overall raw material level.

[0019] Therefore, in order to continuously maintain a stable mixing process using a non-calcined carbon-containing agglomerate mixer as shown in the example of Fig. 1, it is necessary to monitor the fluctuation of the raw material level in the mixing section 4 and maintain the raw material level within an appropriate range. In particular, when using raw materials whose level is likely to fluctuate as described above, it is necessary to manage the raw material level with even more care.

[0020] 2) How to adjust the mixed raw material level As described above, the level of the raw material to be mixed in the mixer can be adjusted by changing conditions such as the amount of raw material to be mixed into the mixer section 4, the rotation speed of the shaft 4b, and the amount of water added from the water-adding nozzle 5, as shown in the example of Fig. 1. For example, if the amount of raw material to be mixed into the mixer section 4 is increased, the raw material level will rise, and if the amount of raw material to be mixed into the mixer section 4 is decreased, the raw material level will fall.

[0021] Also, when the rotation speed of the shaft 4b is increased, the raw material conveying capacity of the kneading blade 4c increases, and the raw material level decreases. On the other hand, when the rotation speed is decreased, the raw material level increases. Also, when the amount of water added is increased, the raw material fluidity increases, and the raw material is more likely to slip when it comes into contact with the kneading blade 4c, making it difficult to convey, so the raw material level tends to increase. On the other hand, when the amount of water added is decreased, the raw material is less likely to slip between the kneading blade 4c, making it easier to convey, so the raw material level tends to decrease. However, if the raw material moisture is too low, the raw material loses its fluidity, making it difficult to convey, and the raw material level increases.

[0022] As for the hardware conditions, the thinning caused by wear of the kneading blades 4c and the weir 4d reduces the material conveying capacity and discharge resistance, respectively, which causes fluctuations in the material level. The wear effect of these hardware components can be compensated for to a certain extent by adjusting the rotation of the shaft 4b, but if the wear progresses beyond a certain level, the hardware must be replaced. Also, the adhesion of the material to the casing 4a, shaft 4b, and kneading blades 4c of the kneading section 4 reduces the material conveying force, which causes the material level to rise, but this can be prevented and eliminated by regular cleaning.

[0023] <Current method for monitoring raw material levels and issues> In a kneading and molding machine for non-calcined carbon-containing agglomerates as shown in the example of FIG. 1, workers often periodically visually monitor the raw material level through gratings, windows, openings, etc. 4f installed on the top surface of the kneading section 4. However, periodic visual monitoring by workers is prone to overlooking short-term fluctuations in the raw material level and to variations in judgment between workers, and is not necessarily a means for quickly detecting fluctuations in the raw material level. Furthermore, visual monitoring by workers requires that workers who are engaged in monitoring the raw material level must always be located near the kneading and molding machine, which is also a factor in increasing production costs. The difficulty of visual management by workers is particularly problematic when multiple systems of kneading and molding machines are operated in parallel.

[0024] Up until now, technologies for monitoring the level of the raw materials using level gauges, level switches, etc. have been developed, but in the conventional technologies, the targets for automatic monitoring of the raw material level are limited to vertical mixers and molding machines, mixing sections, or screw feeders attached to hoppers, and there are no technologies for mixers and molding machines that transport the raw materials horizontally, such as the example shown in Figure 1. Furthermore, since these technologies consider the raw material level to be constant within the device, they are not necessarily capable of quickly detecting local fluctuations in the raw material level within the container.

[0025] In light of the above circumstances, there is a strong demand for the development of technology that can automatically and quantitatively monitor the internal raw material level in a mixer for non-calcined carbon-containing agglomerate ore, as shown in the example of Figure 1, and detect fluctuations in the raw material level at an early stage. [Prior art documents] [Patent documents]

[0026] [Patent Document 1] Patent No. 5000402 [Patent Document 2] Japanese Patent Application Publication No. 61-216749 [Patent Document 3] JP 2003-200414 A [Patent Document 4] Japanese Patent Application Publication No. 10-319694 Summary of the Invention [Problem to be solved by the invention]

[0027] The present invention provides a device for measuring the raw material level in a continuous kneading section and a method for managing the raw material level in the kneading section, for stably and continuously operating the continuous kneading section, which uses kneading blades or screws attached to a single or multiple horizontally installed shafts to transport and knead the raw materials in the horizontal direction, such as the kneading section used in a non-calcined carbon-containing agglomerate kneading and molding machine. [Means for solving the problem]

[0028] In order to solve the above problems, (1) A method for measuring and managing the level of a mixed raw material in a kneading section of a kneading and molding machine, characterized in that a mixed raw material inlet, a connecting pipe which leads the mixed raw material to the kneading section, a kneader having a shaft equipped with an impeller, and a weir from which the mixed raw material is pushed out are arranged in that order, and the level of the mixed raw material is measured at the entrance side of the mixed raw material compaction section just before the weir and / or at the position where the water adding nozzle is installed.

[0029] Also, (2) It is also preferable that the method for measuring and managing the level of the mixed raw material in the kneading section of the kneading and molding machine described in (1) is characterized in that the level of the mixed raw material is maintained at 50% to 90% of the height of the kneading section.

[0030] Also, (3) When the hydration nozzle is disposed in a connecting pipe that leads the raw material to the kneading section, it is also preferable to provide a method for measuring and managing the level of the raw material in the kneading section of the kneading molding machine described in claim 1 or 2, characterized in that the level of the raw material at the position where the hydration nozzle is installed is measured at the inlet side of the kneading section.

[0031] moreover, (4) A kneading and molding machine characterized in that it comprises an inlet for the raw material to be kneaded, a connecting pipe which leads the raw material to the kneading section, a kneader having a shaft equipped with an impeller, and a weir through which the raw material is pushed out, arranged in that order, and is equipped with a device for measuring the level of the raw material to be kneaded at the entrance side of the raw material consolidation section just before the weir and / or at the position where the water adding nozzle is installed.

[0032] moreover, (5) It is also preferable that the kneading molding machine described in (4) is characterized in that the hydration nozzle is disposed in a connecting pipe that leads the raw material to the kneading section, and the raw material level measurement position at the installation position of the hydration nozzle is the inlet side of the kneading section. Effect of the Invention

[0033] INDUSTRIAL APPLICABILITY The present invention provides a method for stably controlling the level of mixed raw materials in the kneading section of a kneading and molding machine, and a kneading and molding machine capable of doing so, and thus has great technical significance. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a diagram showing a kneading and molding machine consisting of a first extrusion section (kneading section) and a second extrusion section (extrusion molding section). [Diagram 2] FIG. 13 is a diagram showing a state in which the raw material gradually accumulates in the kneading machine from just before the raw material compacting section 4e toward the inlet side of the kneading section 4, and the raw material level in the entire kneading section 4 gradually rises. [Diagram 3] FIG. 1 shows a system in which a water-adding nozzle 5 is installed above the horizontal part of a kneading section 4 in a kneading molding machine, and water is added from above to the raw material being kneaded and transported horizontally. [Figure 4] FIG. 1 is a diagram showing an example of an application of the present invention. [Diagram 5] FIG. 13 is a diagram showing actual measurement data of the level of the mixed raw material measured by a microwave level meter installed at a position 150 mm before the mixed raw material compacting section 4e. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The following describes an embodiment of the invention. In order to continuously maintain a stable kneading process using a kneading molding machine as shown in the example of Fig. 1, it is necessary to monitor the fluctuation of the raw material level in the kneading section 4 and maintain the raw material level within an appropriate range. In particular, when using a raw material whose level is prone to fluctuate as described above, it is necessary to manage the raw material level with even more care.

[0036] The reason is that in the kneading section 4, water is added to the raw material, so the raw material level is likely to fluctuate depending on the mixed state of the raw material and the added water, and the upper limit of the allowable raw material filling rate in the kneading section 4 is smaller than that in the extrusion molding section 7 (upper limit in the extrusion molding section 7: 95%, upper limit in the kneading section 4: 90%), so more precise raw material level management is required than in the extrusion molding section 7. Generally, even in actual operation, the frequency of problems (overload, material seal collapse, etc.) caused by fluctuations in the raw material level in the kneading section 4 is higher than that caused by fluctuations in the raw material level in the extrusion molding section 7. For the above reasons, the present invention targets the kneading section 4.

[0037] <Key points and mechanisms of the present invention> As a result of the investigation, it was found that the fluctuation in the raw material level in the kneading section 4 as shown in the example of Figure 1 often originates from local raw material level fluctuations that occur in two locations: just before the raw material consolidation section 4e and at the installation position of the water addition nozzle 5. It was also found that the raw material level of the entire kneading section 4 can be stably controlled by installing instruments to measure the raw material level in these two locations. Below, the detailed results of the investigation will be explained regarding the mechanism that is the origin of the raw material level fluctuation in each of the above two locations and the raw material level control range for stable operation of the kneading section 4.

[0038] Here, the range of the raw material compacting section 4e may be 0 to 100% of the range from the weir 4d to the inlet end of the kneading section 4, or only a part of the range from the weir 4d to the inlet end of the kneading section 4, assuming that the length from the weir 4d to the inlet end of the kneading section 4 is 100%. In the present invention, the latter is used, and it is preferable that the range is from 0% to 25% or less from the weir 4d to the inlet end of the kneading section 4, starting from the weir 4d. As described above, the raw material compacting section 4e has a narrower inner diameter than the kneader 4, so the raw material is densely packed toward the weir 4d, but if the range is 0% from the weir 4d to the inlet end of the kneading section 4, a material seal is often not formed, and if the range exceeds 25%, the densely packed portion of the raw material becomes too large, which puts too much load on the driving sources such as the kneading blade roots 4c and shafts 4b and the electric motors that drive them, which leads to damage to the equipment and increases in size, which is not preferable. In the present invention, a raw material level is disposed upstream of the inlet of the raw material compacting section 4e, so that the raw material is densely packed in the raw material compacting section 4e and a material seal is formed at the weir 4d.

[0039] In the vacuum extrusion molding method, the raw material is compressed in the raw material compression section 4e to form a material seal, and the vacuum degassing conditions between the subsequent vacuum chamber 6 and the extrusion molding gate 7d are kept at -40 kPaG or less, which is necessary to ensure the strength of the molded product. In order to compress the raw material, the raw material compression section 4e has a narrower diameter than the previous section (25 to 100% from the gate 4d toward the inlet end of the kneading section 4), as described above, and is covered on all sides by a strong casing 4a, and is structured so that the raw material receives resistance from the gate 4d installed on the outlet side.

[0040] This structure allows the raw material level to be 100% in the raw material compaction section 4e. R(The weir 4d requires a mixed raw material level of 100%). On the other hand, the portion from the inlet end of the mixed raw material consolidation section 4e to the inlet end of the kneading section 4 is not expected to have a mixed raw material level of 100% (appropriate range: 50-90%), and the upper surface of the portion is provided with a grating, a steel plate with a sight glass, or a steel plate that can be easily opened and closed as an internal observation section 4f on the upper surface of the kneading section 4 to monitor the internal mixed raw material level. For this reason, as described above, it is preferable that the range of the mixed raw material consolidation section 4e is specified to be approximately 0% to 25% from the weir 4d toward the inlet end of the kneading section 4.

[0041] In this study, raw steel pellets (average moisture content during normal operation is about 9% to 14% by mass) were used as the raw material to be mixed. Raw steel pellets are generally stored in outdoor raw material yards, and the moisture content is easily affected by temperature and precipitation. This means that the moisture content of the raw material to be mixed and fed into the mixing section 4 can change unintentionally, and the fluidity is easily affected by slight changes in moisture conditions.

[0042] Furthermore, since the particle size conditions are prone to variation, the mixed raw material level is prone to fluctuate. In this study, the granulation is performed from the outlet side of the kneading section 4 onwards under vacuum degassing conditions of ≦-40 kPa, and in order to maintain this condition, it is necessary to perform vacuum degassing using the vacuum pump 8 in Figure 1, and to material seal the gate 4d and the extrusion molding gate 7d with the mixed raw material. In the example shown in Figure 1, the vacuum pump 8 is connected to the vacuum chamber 6 via the vacuum pump connection pipe 9.

[0043] <Material mixing level control before the material mixing consolidation section 4e> In the raw material compacting section 4e, the raw material conveyed from the inlet side of the kneading section 4 is resisted by the weir 4d, so that the raw material is compacted in the casing 4a. During normal operation, the discharge resistance of the raw material by the weir 4d and the conveying force of the raw material by the kneading blade 4c are balanced, and the raw material level is high only in the raw material compacting section 4e. However, if the extrusion force of the raw material decreases for some reason or the fluidity of the raw material decreases, the discharge resistance by the weir 4d temporarily exceeds the extrusion force of the kneading blade 4c, and the discharge speed of the raw material from the weir 4d to the subsequent process decreases. At this time, as shown in FIG. 2, the raw material gradually accumulates from just before the raw material compacting section 4e back to the inlet side of the kneading section 4, and the raw material level of the entire kneading section 4 gradually rises.

[0044] In addition, if the amount of raw material supplied from the inlet of the kneading section 4 increases for some reason, the raw material level also rises, and if the discharge resistance of the raw material decreases or the fluidity of the raw material increases, the raw material level will decrease starting from the point just before the raw material compacting section 4e. In addition, if the amount of raw material supplied from the inlet of the kneading section 4 decreases for some reason, the raw material level will also decrease. For these phenomena, if a measuring means for the raw material level is installed near the point just before the raw material compacting section 4e, fluctuations in the raw material level can be detected early and stable kneading can be continued.

[0045] Here, the conditions of the raw material level at the start of the raw material compaction section 4e that enable stable mixing to be continued were investigated. The results of this investigation are shown in Table 1. From the investigation results, it was found that when the height of the kneading section 4 (height from the bottom to the top of the casing 4a) is taken as 100%, if the raw material level at a position just before the start of the raw material compaction section 4e (for example, a position about 100 mm to 300 mm from the start of the raw material compaction section 4e toward the inlet side of the kneading section 4) is controlled within a range of 50% to 90%, the raw material is compacted in the raw material compaction section 4e, the raw material level is 100% at least at the weir 4d, a material seal is formed, and stable mixing can be continued. If the level of the raw material kneaded at a position approximately 100 mm to 300 mm from the start of the raw material compaction section 4e toward the entry side of the kneading section 4 exceeds 90%, the raw material level will exceed 100% in approximately 5 to 30 minutes, making operation impossible. On the other hand, if the level of the raw material kneaded at a position approximately 100 mm to 300 mm from the start of the raw material compaction section 4e toward the entry side of the kneading section 4 falls below 50%, the raw material kneaded at the raw material compaction section 4e is not compacted, so the raw material cannot be sufficiently kneaded, and the insufficiently kneaded raw material is sent to the subsequent process, resulting in unstable granulation in the subsequent process.

[0046] [Table 1]

[0047] In the above investigation, a microwave level meter was used as a means for measuring the raw material level, which was installed at the top of the kneading section 4 at a position about 150 mm from the start point of the raw material compaction section 4e toward the inlet side of the kneading section 4. The raw material level can be measured visually by an operator if a standard is set in advance. The measuring means of the level meter is not limited to a microwave level meter, and any type (laser distance meter, millimeter wave level meter, proximity sensor, various level switches, etc.) is acceptable as long as it can measure the raw material level in the kneading section. However, in order to prevent damage to the sensor and the kneading section 4 due to contact with the raw material or the kneading blades 4c, etc., and to prevent a decrease in measurement accuracy due to the adhesion of raw material to the sensor, a non-contact level meter such as a laser distance meter or a microwave level meter is preferable. Furthermore, since dust and water vapor derived from the raw material may be generated from inside the kneading section 4, a microwave level meter or a millimeter wave level meter that can perform relatively stable measurement even in the presence of dust and water vapor is more preferable.

[0048] The kneading state was judged based on the operating state of the extruder using the kneading section 4 as the first extrusion section. Problems with the operating state are, specifically, when the raw material cannot be consolidated in the raw material consolidation section 4e in the kneading section 4, or when water cannot be added evenly, resulting in an inability to maintain material seal or insufficient kneading of the raw material, which leads to a decrease in pellet yield or strength. A kneading state in which pellet production can continue for 1 hour or more while satisfying the vacuum deaeration condition of ≦-40 kPa is evaluated as ◯, and a state in which stable production of products is not possible due to a decrease in yield or strength is evaluated as ×.

[0049] In this way, the control range of the raw material level before the raw material compaction section 4e is 50% to 90% for continuous and stable operation, 50% to 70% is better, and 50% to 60% is optimal. The reason for this is that by controlling the raw material level (the filling rate of the raw material) to a constant level, the force with which the raw material is pressed by the raw material blades 4c against the gate 4d is stabilized, so that the variation in the properties of the raw material discharged is reduced.

[0050] As described above, the level of the raw material to be mixed before the raw material compacting section 4e can be adjusted by adjusting the amount of raw material to be mixed, the rotation speed of the shaft 4b, and the amount of water added from the water adding nozzle 5. If the above methods do not allow adjustment, there is a high possibility that the hardware is worn out or the raw material is adhering to the hardware, so the fluctuation in the raw material to be mixed can be suppressed by replacing or cleaning the parts.

[0051] <Management of the mixing material level at the water addition position in the mixing section 4> The kneading section 4 may be provided with a water-adding nozzle 5 for adding moisture necessary for kneading. At the position of the water-adding nozzle 5 (water-adding position), the moisture content of the raw material to be kneaded is relatively high compared to the raw material before and after the water-adding position, so the fluidity is likely to be high. For this reason, at the water-adding position, the moisture content of the raw material to be kneaded may become excessive (excessive fluidity) for some reason, and the raw material to be kneaded may easily slip when it comes into contact with the kneading blade 4c. At this time, the conveying speed of the raw material to be kneaded decreases, and the level of the raw material to be kneaded increases from the water-adding position to the inlet side of the kneading section 4. On the other hand, at this time, the raw material to be kneaded decreases in conveying speed after the water-adding section, so the raw material to be kneaded is insufficient in supply, and the level of the raw material to be kneaded decreases.

[0052] Here, the conditions of the raw material level at the water-adding position that allows stable mixing to continue were investigated. The investigation method was the same as that of the raw material consolidation section 4e described above, but the raw material level was measured visually by an operator according to a preset standard. The results of this investigation are shown in Table 2. From the investigation results, it was found that when the raw material level at the water-adding position exceeds 90%, the raw material level at the same position exceeds 100% in about 5 to 30 minutes, overflows from the internal observation section 4f on the top surface of the kneader, and operation becomes impossible. On the other hand, when the raw material level at the same position becomes less than 50%, the water sprayed from the water-adding nozzle hits the shaft 4b or the kneading blade 4c before hitting the powder raw material. In this case, it was found that the raw material cannot be sprayed evenly, the moisture of the raw material is dispersed, the material seal collapses, and granulation cannot be stably continued in the subsequent process.

[0053] [Table 2]

[0054] As described above, the control range of the raw material level at the water addition position allows for continuous and stable operation if it is between 50% and 90%, but between 50% and 70% is even better, and between 50% and 60% is optimal. The reason for this is that by controlling the raw material level (filling rate of the raw material) to a constant level, the amount of water sprayed from the water addition nozzle onto the raw material becomes constant, so that the variation in the properties of the raw material discharged from the kneading section 4 becomes smaller.

[0055] As described above, the level of the raw material to be mixed can be adjusted by adjusting the amount of raw material to be mixed, the rotation speed of the shaft 4b, and the amount of water added from the water-adding nozzle 5. If the above methods do not allow adjustment, there is a high possibility that the hardware is worn out or the raw material is adhering to the raw material, so the fluctuation in the raw material to be mixed can be suppressed by replacing or cleaning the parts. In particular, since the rise in the raw material level starting from the water-adding position mostly occurs when the raw material at the water-adding position has an excessive moisture content, reducing the amount of water added is often effective. The possibility of reducing the amount of water added can be determined by comparing the actual moisture value of the discharged raw material to a preset moisture value (for example, in the case of pellet raw material in this study, if the moisture value exceeds the usual upper limit of 14 mass%, it is determined that there is an excess of moisture, and the amount of water added is reduced).

[0056] Next, the installation position of the water-adding nozzle 5 will be described. There are two types of installation methods for the water-adding nozzle 5: one is to install the water-adding nozzle 5 inside the connecting pipe 3 and spray water onto the raw material falling inside the connecting pipe 3, and the other is to install the water-adding nozzle 5 on the top of the horizontal part of the kneading section 4 (the part corresponding to the internal observation part 4f on the top surface of the kneader in FIG. 3) and add water from above to the raw material being conveyed horizontally (in this case, it does not matter whether the tip of the water-adding nozzle 5 is above or below the surface of the internal observation part 4f on the top surface of the kneader). In the case of the latter installation method, the water-adding nozzle 5 is preferably installed within a range of about 50% of the machine length of the kneading section 4, starting from the outlet end of the connecting pipe 3 (i.e., the starting point of the internal observation part 4f on the top surface of the kneading section 4), in order to ensure a sufficient kneading time for the raw material after water addition.

[0057] The present invention is applicable to either the former or the latter case, as described later. The installation positions of the level gauges will be explained. The raw material level is measured at the inlet and outlet of the kneading section 4. The level gauges are an inlet level gauge 10 that measures the raw material level in the range where the water-adding nozzle 5 is installed on the inlet side of the kneading section 4, and an outlet level gauge 11 that measures the raw material level just before the raw material compaction section 4e on the outlet side of the kneading section 4. In particular, the inlet level gauge 10 is positioned so that the raw material level can be measured at the location where the local raw material moisture is estimated to be the highest. do. The reason is that at such a position, the raw material to be kneaded is likely to slip when it comes into contact with the kneading blade 4c, and the raw material to be kneaded is likely to accumulate and cause the level to rise.

[0058] Specifically, when the hydration nozzle is installed inside the connecting pipe 3, it is preferably installed at the start point of the horizontal part (grating 4f) of the kneading section 4. On the other hand, when the hydration nozzle is installed in the horizontal part (grating 4f) of the kneading section 4, it is preferably installed immediately after the hydration nozzle (on the kneader outlet side). In the latter case, particularly when there are multiple hydration nozzles, it is preferable to install them immediately after the position of the hydration nozzle closest to the outlet side of the kneading section 4, because it can be estimated that the moisture content of the mixed raw material is highest at such a position.

[0059] In the kneading section 4 as shown in the example of Figure 1, a method for managing the raw material level in the kneading section 4 has been invented, which measures the raw material level just before the raw material compaction section 4e (preferably a position 100 to 300 mm from the start of the raw material compaction section 4e toward the inlet side of the kneading section 4) and at the installation position of the water addition nozzle 5 (preferably within about 50% of the length of the kneader 4, starting from the outlet end of the connecting pipe 3 (i.e. the start point of the internal observation section 4f on the top surface of the kneader)), and maintains the raw material level at 50% to 90% of the height of the kneading section 4, thereby enabling stable kneading to be continued.

[0060] The following describes how to adjust the level of the raw material to be mixed when it is out of the specified range. Since the kneading section 4 is generally operated at a constant production volume, the raw material level to be mixed is adjusted by two means: the number of revolutions of the shaft 4b and the amount of water added from the water adding nozzle 5. An example of the adjustment method is shown below.

[0061] For example, when the raw material level before the raw material compaction section 4e is on the rise, the rotation speed of the shaft 4b is increased to promote the discharge of the raw material from the gate 4d, thereby lowering the raw material level. On the other hand, when the raw material level in the raw material compaction section 4e is on the fall, the rotation speed of the shaft 4b is decreased to raise the raw material level.

[0062] When the level of the raw material to be kneaded at the water adding position is rising, this is almost always due to an excess of moisture in the raw material to be kneaded. Therefore, the moisture content of the raw material to be kneaded discharged from the kneading section 4 is measured, and if the moisture content of the raw material to be kneaded is excessive, the amount of water added from the water adding nozzle 5 is reduced to an appropriate range, thereby lowering the raw material level to be kneaded.

[0063] In addition, when the raw material moisture content is within the appropriate range but the raw material level is on the rise, the rotation speed of the shaft 4b is increased to lower the raw material level, and when the raw material level is low, the rotation speed of the shaft 4b is decreased to raise the raw material level. When the amount of added water is not excessive, the raw material level fluctuates up and down in many cases in conjunction with the raw material level before the raw material compacting section 4e and the raw material level at the water addition position. In other words, when one raw material level is rising, the other also rises, and when one raw material level is low, the other also tends to fall.

[0064] Therefore, if it is confirmed by measuring the moisture content on the outlet side of the kneading section 4 that the moisture content of the raw material is not excessive, in most cases it is acceptable to uniformly adjust the raw material level in the kneading section 4 by adjusting the rotation speed of the shaft 4b. If the raw material level cannot be adjusted by the rotation speed of the shaft 4b or the amount of water added from the water adding nozzle 5, the raw material level is adjusted by the amount of raw material supplied to the kneading section 4. Reducing the amount of raw material supplied will decrease the raw material level, and increasing the amount of raw material supplied will increase the raw material level. EXAMPLES

[0065] An application example of this technology is as shown in FIG. 4, where the raw material sent from the mixer 1 is fed into the raw material inlet 2. The raw material fed into the raw material inlet 2 is guided to the kneading section 4 through the connecting pipe 3, and is kneaded using the kneading blades 4c provided on the shaft 4b. A raw material compaction section 4e is provided in front of the gate 4d from which the raw material is pushed out, and a level meter is installed in front of the raw material compaction section 4e to ensure that the material to be kneaded can be appropriately transported to the raw material compaction section 4e. In this embodiment, the level meter in front of the raw material compaction section 4e is installed at a position about 150 mm from the start point of the raw material compaction section 4e toward the entry side of the kneading section. In addition, the water adding nozzle 5 is installed at a position between 0 and 25% when the length from the start of the grating 4f (the boundary between the connecting pipe 3 and the grating 4f) to the weir 4d is taken as 100%, and the mixed raw material level is determined at around the 25% position.

[0066] Figure 5 shows the actual data of the raw material level measured by a microwave level meter installed at a position 150 mm before the raw material compaction section 4e. It can be seen that the raw material level can be controlled within a range of approximately 50 to 80% by adjusting the number of revolutions of the shaft 4b and the amount of water added from the water adding nozzle 5 through monitoring by the inlet level meter 10 and the outlet level meter 11. Note that the raw material level in Figure 5 is measured by the periodic fluctuations that occur with the rotation of the shaft 4b, as is commonly done. Strange In order to ignore fluctuations, a moving average value (a moving average value over 5 seconds in this embodiment) is used.

[0067] Table 3 shows examples of the present invention and comparative examples. In Examples 1 to 5 in Table 3, the raw material levels before the raw material consolidation section 4e and at the position of the water-adding nozzle 5 are in the range of 50 to 90%, respectively, and are examples in which stable operation is possible. In Comparative Example 1, the raw material level before the raw material consolidation section 4e exceeds 90%, and in Comparative Example 2, the raw material level at the raw material consolidation section 4e is less than 50%, so neither is an example in which stable operation is possible. In Comparative Example 3, the raw material level at the position of the water-adding nozzle 5 exceeds 90%, and in Comparative Example 4, the raw material level at the position of the water-adding nozzle 5 is less than 50%, so neither is an example in which stable operation is possible.

[0068] [Table 3]

[0069] The present invention can be applied to any type of kneading section 4, for example as shown in the examples of Figures 1 to 4, regardless of the number, installation position and shape of the water-adding nozzles 5, the size and shape of the weir 4d and the raw material compaction section 4e, or the size, shape and number of the kneading blades 4c. [Explanation of symbols]

[0070] 1 Mixer 2 Inlet 3 Connecting Pipe 4. Mixing section 4a Casing 4b Shaft 4c Mixing blade 4d weir 4e. Raw material consolidation section (where the raw material is consolidated before the weir and where mixing is particularly prominent) 4f Internal observation area on top of the mixer (grating, glass window, opening, etc.) 5 Water nozzle 6 Vacuum chamber 7 Extrusion Molding Section 7a Casing 7b Extrusion molding shaft 7c Extrusion molded blade 7d Extrusion weir 8. Vacuum Pump 9 Vacuum pump connection pipe

Claims

1. A raw material inlet, a connecting pipe for introducing the raw material to the kneading section, a kneader having a shaft equipped with an impeller, and a weir through which the raw material is pushed out are arranged in this order. A method for measuring and managing a level of a mixed raw material in a kneading section of a kneading and molding machine, in which an outlet side of the kneading section is vacuum degassed to -40 kPaG or less, comprising: A method for measuring and managing the level of mixed raw material in the kneading section of a kneading and molding machine, characterized in that the level of the mixed raw material is measured using a microwave level meter or a millimeter wave level meter at the inlet side of the mixed raw material consolidation section before the dam and / or at the location where the water adding nozzle is installed, and the level of the mixed raw material is maintained at 50% to 90% of the height of the kneading section.

2. 2. A method for measuring and managing the level of a raw material mixed in a kneading section of a kneading molding machine as described in claim 1, characterized in that, when the hydration nozzle is arranged in a connecting pipe that leads the raw material to the kneading section, the level of the raw material mixed at the position where the hydration nozzle is installed is measured on the inlet side of the kneading section.

3. A kneading and molding machine comprising a raw material inlet, a connecting pipe for introducing the raw material into a kneading section, a kneader having a shaft equipped with an impeller, and a weir through which the raw material is pushed out, which are arranged in this order, and which is equipped with a device for measuring the raw material level at the inlet side of the raw material consolidation section just before the weir and / or at a position where a water adding nozzle is installed, and which is vacuum degassed to -40 kPaG or less at the outlet side of the kneading section, A microwave level meter or a millimeter wave level meter is arranged on the inlet side of the mixed raw material consolidation section before the weir and / or at the installation position of the water adding nozzle, A compounder operated so that the continuous mixed feed level is maintained at 50% to 90% of the mixing section height.

4. 4. The kneading and molding machine according to claim 3, wherein the water-adding nozzle is disposed in a connecting pipe that leads the raw material to the kneading section, and the raw material level measurement position at the water-adding nozzle installation position is on the inlet side of the kneading section.

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