JP4401818B2 - Briquette manufacturing method - Google Patents

Description

  The present invention relates to molding and reduction treatment of dust collection dust generated from a melting furnace and a refining furnace, and relates to a method for producing briquettes having excellent moldability and high reducing ability.

  Dust collection dust generated from melting furnaces and smelting furnaces contains valuable metal oxides, but they are fine powders and contain heavy metals. Yes. In other words, most of the dust collection dust is discarded by an industrial waste disposal contractor. In this case, landfill disposal is usually performed, but there is a risk of environmental pollution due to the burden of disposal costs, scattering of the fine dust to the surrounding environment during handling, and mixing of heavy metals into the wastewater after landfill.

  In recent years, in order to solve these problems, attempts have been made to collect dust-collected dust into pellets or briquettes, dissolve it in a melting furnace, and recover valuable metals in the dust. For example, Patent Literature 1 and Patent Literature 2 are disclosed as methods for molding fine powder.

  These methods are manufacturing methods in which plastic is added to powder and molded into a briquette shape. Patent Document 1 adds thermoplastic waste plastic, kneads and melts and compresses the plastic with frictional heat of metal powder, Patent Document 2 is a method of mixing and heating a metal-based powder and a plastic raw material, melting a part of the plastic raw material into a binder, and briquetting.

  Although these methods are excellent methods for molding powder, there are problems in reducing and recovering valuable metal oxides in the powder. In other words, a part of the plastic can be a reducing agent, but it is easy to burn and scatter, disappears immediately after heating, and loses its role as a binder. , There is a drawback of returning to powder. Further, even when used in a melting furnace, it must be kept at a low temperature before being charged into the furnace, and a large amount of reducing agent is required for the melting process, which has the disadvantage of increasing the processing cost.

  Next, Patent Literature 3 and Patent Literature 4 are disclosed as methods for recovering metal from powder containing metal oxide. In the method according to Patent Document 3, powder dust is mixed with waste toner powder, and then compression-molded and granulated into pellets. The granulated pellets are supplied as raw materials to a metal melting furnace such as a cupola, and the metal is recovered. This method is also used as fuel.

  This method does not solve the problems described above. In other words, in order to supply pellets formed by mixing and molding powder dust and waste toner powder as raw materials to the metal melting furnace, it is necessary to keep them at a low temperature until they are supplied to the melting furnace. In addition, since combustion occurs and the amount of waste toner disappears, a sufficient reducing action cannot be obtained, and a large amount of a reducing agent supplied separately is required to recover the metal, resulting in an increase in processing cost.

  The method according to Patent Document 4 is a method in which pellets or briquettes formed by adding a reducing agent containing carbon to dust are fired at 1000 ° C. to 1100 ° C. for 5 minutes or more. In this method, powdery dust is molded. Therefore, the molding state is unstable because no binder is added. Further, firing at 1000 ° C. to 1100 ° C. melts the gangue portion and strengthens the bonded state, but it is insufficient for proceeding the reduction reaction, and a sufficient reduced state cannot be obtained.

  In addition to the patent documents mentioned here, various methods for producing powder dust or methods for reducing powder dust have been disclosed, but none of them satisfy both moldability and reducibility.

JP 2001-294947 A JP-A-9-241766 JP 2000-70900 A JP 2001-40429 A

  The object of the present invention is to solve the conventional moldability and reducibility problems as described above, with respect to the molding and reduction treatment of dust collection dust generated from melting furnaces and refining furnaces that are industrial waste. It is to obtain a method for producing briquettes that is excellent in high reducibility.

  The present invention is a briquette manufacturing method characterized by mixing and molding 1 to 10 mass% of plastic, 5 to 30 mass% of a lime component, and 5 to 20 mass% of a carbonaceous material in dust collection dust. The dust collecting dust is melting furnace dust collecting dust or smelting furnace dust collecting dust, the plastic is toner, the lime component is quick lime or slaked lime, A briquette manufacturing method characterized in that dust is mixed with one or two kinds of scales generated in a rolling process or neutralized sludge generated in a pickling process. Further, following the above briquette production method, the briquette production method is characterized by holding at 1200 ° C. to 1350 ° C. for 15 minutes or more and 60 minutes or less.

  The briquettes manufactured by the method of the present invention are excellent in moldability and can secure a stable molded state even at high temperatures. When the reduction process is performed in the previous step of melting in the melting furnace, the briquette itself has a reducing agent, a reducing auxiliary agent, and a binder for high temperature, so a high reduction rate can be obtained stably, and molding is performed even after reduction. It is possible to obtain a briquette in which the state is maintained. In addition, when processing directly in the melting furnace, it is not necessary to perform special management in the process until charging, and it is not necessary to newly add a reducing agent in the melting furnace. As described above, the briquette manufactured by the method of the present invention is easy to process and can be reduced at a low cost.

  The inventors of the present invention have studied various methods for producing briquettes having excellent moldability and high reducibility with respect to the molding and reduction treatment of powdered dust collection dust. As a result, the following points are considered in the production of briquettes. Investigated that there is a need.

(1) It is effective to add lime as a substance having a binder effect at both low and high temperatures. (2) It is necessary to add a carbonaceous material in order to impart the reducibility of the briquette itself. (3) Conventionally, a plastic used as a binder for low temperature is more effective as a reducing auxiliary agent that suppresses combustion of the carbonaceous material by high-temperature treatment and promotes reduction by C in the carbonaceous material than when used as a binder.

  Based on these results, the appropriate blending ratio was then examined. FIG. 1 shows the relationship between the lime mixing ratio and the yield ratio of a block of 5 mm or more after briquette molding when plastic and carbon material are added to the dust collected in the melting furnace and the refining furnace and mixed and molded. In the figure, ◯ indicates the case where quick lime is used as the lime, and □ indicates the case where slaked lime is used. Further, in this case, 5 mass% is added to the plastic using waste toner powder collected from a copying machine, an image processing apparatus, etc., carbon material is added 15 mass% of fine coke, and the briquette is 40 mm wide × 60 mm long × It was molded into an egg shape having a thickness of 20 mm, and after molding, the yield of masses of 5 mm or more was evaluated using a 5 mm sieve.

  From FIG. 1, there is no difference between quick lime and slaked lime as lime components, and a yield of 70% or more can be secured by adding 5 mass% or more. The addition of 5 mass% or more tends to gradually improve the yield, but the addition of 30 mass% or more has no margin to improve the yield, and the addition of 30 mass% or more reduces the amount of dust collection dust. In order to connect, it is necessary to add 5 to 30 mass% of lime.

  The 5 mm or more lump briquettes to which 5-30 mass% of the lime content obtained here was added were subjected to reduction treatment in a rotary hearth type heating furnace. After maintaining at 1300 ° C. for 30 minutes, after reducing and cooling, the yield of the briquette of 5 mm or more was evaluated, and as a result, the yield was 70% or more. From this, it was confirmed that lime content has a role as a binder even at a low temperature during molding and a high temperature during reduction treatment.

  Figure 2 shows the dust collected in the melting furnace and smelting furnace. Add plastic and carbon material to the lime, mix and mold, and then form a briquette of 5 mm or more at 1300 ° C for 30 minutes in a rotary hearth-type heating furnace. The relationship between the mixing ratio of the carbonaceous material and the reduction ratio of Fe content in the briquette in the case of reduction treatment is shown. In addition, 5 mass% was added to the plastic using waste toner powder collected from a copying machine, an image processing apparatus, etc., 20 mass% of quicklime was added to the lime content, and coke powder was used as the carbon material.

  As shown in FIG. 2, when the coal content is 5 mass% or more, the Fe reduction rate is 70% or more, and a high reduction rate is obtained. When the addition is 5 mass% or more, the Fe reduction rate tends to increase gradually up to 20 mass%. However, when the addition is 20 mass% or more, there is almost no increase in the Fe reduction rate. Since it causes an increase, the blending ratio of the carbon material needs to be 5 to 20 mass%.

  In FIG. 3, lime content is added to the dust collected in the melting furnace and smelting furnace, plastic is added to the carbonaceous material, and the mixture is mixed and molded. The molded briquette of 5 mm or more is formed at 1300 ° C. in a rotary hearth-type heating furnace. The relation between the blending ratio of the plastic and the reduction ratio of Fe in the briquette in the case of partial reduction treatment is shown. In addition, 20 mass% of quick lime was added to the lime content, 10 mass% of powder coke was added to the carbon material, and waste toner powder collected from a copying machine, an image processing apparatus, or the like was used as the plastic.

  From FIG. 3, if the compounding ratio of the plastic is 1 mass% or more, the Fe reduction ratio of 70% or more is stably achieved. Although the Fe reduction rate gradually increases and the variation of the Fe reduction rate tends to be reduced until the plastic content rate is 10 mass%, there is almost no improvement margin with addition of 10 mass% or more. Addition of 10% by mass or more increases the combustion by the plastic, easily ignites even at low temperatures, and requires careful handling. Therefore, the blending ratio of the plastic needs to be 1 to 10% by mass.

  Here, the effect of plastic in the reduction reaction is easier to burn than charcoal such as powdered coke, so the plastic content burns in the early stage of reduction, so the oxygen concentration around and inside the briquette is lowered, and the briquette It is thought to play the role of a reducing aid that suppresses the ingress of oxygen into the interior and promotes the progress of the reduction reaction by the carbonaceous material. As plastics having such an action, those having a melting point of around 100 ° C. and containing highly flammable styrene acrylic resin and polyester resin are effective. Among them, they are used for copying machines, image processing apparatuses, etc. The toner (or waste toner powder collected from them) contains 50 mass% or more of these resins, and the waste toner powder is industrial waste, which is also effective in terms of resource recycling.

  Next, briquette reduction treatment conditions were examined. Fig. 4 shows the dust collected in the melting furnace and smelting furnace, added with plastic, lime, and charcoal, mixed and molded, and then held the various briquettes of 5 mm or more at various temperatures in a small-scale atmospheric heating experimental furnace. The distribution of the reduction rate of Fe content in the briquette in the relationship between the temperature and the holding time when the reduction treatment is performed by time is shown. In the figure, ◯ indicates that the Fe reduction rate is 70% or more, Δ indicates 50 to 70%, and X indicates 50% or less. Further, 5 mass% of waste toner powder was added to plastic, 20 mass% of quicklime was added to the lime, and 10 mass% of powder coke was added to the carbon material.

  As shown in FIG. 4, if the temperature is maintained at 1200 ° C. or higher for 15 minutes or longer, an Fe reduction rate of 70% or higher can be obtained. In the experiment, the briquette melted at a temperature exceeding 1350 ° C. and adhered to the refractory, resulting in a phenomenon that could not be separated. Further, it was confirmed that when the holding time was 60 minutes or more, the increase in Fe reduction rate was small and the heat treatment cost was higher. From the above, it is preferable that the reduction treatment condition is 1200 to 1350 ° C. and 15 minutes or more and 60 minutes or less.

  The present inventors investigated the possibility of treatment of the neutral sludge generated in the pickling process and the scale generated in the rolling process which contains valuable metal components and exists in a powder form, as in the dust collection dust. As a result, it was confirmed that even if one kind or two kinds of scale or neutralized sludge were mixed with the dust collection dust, the moldability and the reducibility were not deteriorated under the above-mentioned blending conditions.

  Hereinafter, the present invention will be described in more detail based on examples of the present invention and comparative examples. Table 1 shows the raw material composition of the present invention and comparative examples, the yield of lumps of 5 mm or more after briquette molding, the heating temperature when holding the reduction treatment, the holding time, the Fe reduction rate after the reduction treatment, the post-reduction treatment The yield of a mass of 5 mm or more and the metal recovery cost index are shown. In addition, as raw materials, dust collection dust of melting furnace and refining furnace, scale generated in rolling process, neutralized sludge generated in pickling process, waste toner as plastic, quick lime and slaked lime as lime component, as carbon material Used coke powder, and in the reduction treatment, only a lump of 5 mm or more was used after briquette molding. Further, the metal recovery cost index is based on the raw material cost, the reduction processing cost, and the cost for recovering the metal by supplying the briquette after the reduction processing to the melting furnace. It was determined by proportionally converting 1 as 100.

  From Table 1, No. of the present invention example. 1 to 10 satisfy the condition range of the present invention for both the raw material composition and the reduction treatment condition. As a result, the yield of the block of 5 mm or more after briquette molding and the yield of the block of 5 mm or more after the reduction treatment are 70%. The above high yield has been achieved. In addition, since the Fe reduction rate after the reduction treatment is highly stable at 70% or more, the metal recovery cost is also stable at a low level.

  On the other hand, no. In 11 to 16, the raw material composition or the reduction treatment condition is outside the conditions of the present invention, and the yield of the mass of 5 mm or more after briquette molding, the yield of the mass of 5 mm or more after the reduction treatment, or the Fe reduction rate after the reduction treatment is As a result, the reduction treatment cost is high. Moreover, No. of the comparative example. In No. 17, the reduction treatment temperature was outside the conditions of the present invention, and the briquette adhered to the refractory during the reduction treatment, making it impossible to recover. Furthermore, No. of the comparative example. 18-20, the yield of the lump of 5 mm or more after briquette molding, the yield of the lump of 5 mm or more after the reduction treatment, and the Fe reduction rate after the reduction treatment are the same as those of the present invention example, but the raw material cost or the reduction treatment Since the cost is high, the metal recovery cost is higher than that of the example of the present invention.

It is a figure which shows the relationship between the compounding rate of a lime, and the yield rate of a product 5 mm or more after briquette molding. It is a figure which shows the relationship between the compounding rate of a carbon material, and the reduction rate of Fe content in briquette. It is a figure which shows the relationship between the compounding rate of a plastic, and the reduction rate of Fe content in a briquette. It is a figure which shows distribution of the reduction | restoration rate of Fe part in briquette in the relationship between the temperature at the time of a reduction | restoration process, and holding time.

Claims (5)

1-10 mass% of plastic, 5-30 mass% of lime component, and 5-20 mass% of carbonaceous material are mixed and molded into the dust collection dust, and then at 1200 ° C-1350 ° C for 15 minutes to 60 minutes A method of manufacturing briquettes, characterized by holding .   The method for producing briquettes according to claim 1, wherein the dust collection dust is melting furnace dust collection dust or a refining furnace dust collection dust.   The briquette manufacturing method according to claim 1 or 2, wherein the plastic is a toner.   The briquette manufacturing method according to any one of claims 1 to 3, wherein the lime component is quick lime or slaked lime.   The briquette manufacturing method according to any one of claims 1 to 4, wherein the dust collection dust is mixed with one or two kinds of scale generated in the rolling process or neutralized sludge generated in the pickling process.

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