JP2007222713A - Removal and recovery of magnesium and calcium, and a type zeolite manufacturing method from steel industry by-product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of A type zeolite which adjusts the components of the raw material in order to synthesize A type zeolite using only the industrial by-product such as blast furnace slag and the like, and heats and agitates the same in an alkaline aqueous sloution using a jar mill type reactor to manufacture A type zeolite, and to provide a removal and recovery method of magnesium and calcium from the steel industry by-product which recovers the material generated at the time of adjustment and effects the perfect recycling of the industrial by-product. <P>SOLUTION: Calcium and magnesium are selectively removed by performing the agitation treatment of the industrial by-product such as the blast furnace slag and the like in a formic acid or citric acid aqueous solution using the jar mill type reactor. The industrial by-product is adjusted to form the composition so that the A type zeolite can be manufactured and synthesized. Calcium is recovered as a useful form such as calcium formate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention carries out magnesium and calcium elution treatment of steel slag with various acids at room temperature, examines a method for removing and recovering magnesium and calcium from slag, and clarifies suitable acid species, pH, and elution time. is there. Further, the present invention relates to the study of conditions for shifting to a composition suitable for A-type zeolite synthesis and to provide a method for producing A-type zeolite using slag after composition adjustment.

A heat storage system using heat generated by water vapor adsorption on zeolite is considered to be applicable to smoothing the difference in peak power consumption during daytime and nighttime, and effective use of low-temperature exhaust heat. Above all, the A-type zeolite is a cubic synthetic zeolite, and the Na-A type unit cell having Na + as an exchange cation is expressed as (Na ₁₂ [AlSiO ₄ ] ₁₂ · 27H ₂ O) _8, and sodium is potassium or It is known to be replaced with alkaline earth metals. Zeolite is synthesized by placing a silicon source, an aluminum source, a curing agent and water under high temperature and high pressure for a certain time (hydrothermal synthesis method). Generally, sodium silicate, colloidal silica, smoked silica, silicon alkoxide and the like are used as the silicon source, and aluminum hydroxide, sodium aluminate, aluminum alkoxide and the like are used as the aluminum source (for example, Non-Patent Document 1). . However, there is a problem that the cost of the synthetic zeolite is very high for use as a heat storage material.

  In 2004, pig iron production in Japan was 82.89 million tons, and the amount of blast furnace slag produced (with no moisture) was 23.82 million tons. Of this, granulated slag was 18.6 million tons, and slow-cooled slag was 522. 10,000 tons. The water granulation rate (granulated slag production / blast furnace slag production) is 78.1 mass% (for example, Non-Patent Document 2). Many of these resources have been recycled into cement raw materials, roadbed materials, concrete aggregates, etc. However, the expansion of domestic demand for cement is not expected in the future, and the development of new applications is an issue. Granulated blast furnace slag is mainly composed of silicon oxide, aluminum oxide, magnesium oxide, and calcium oxide. Considering that sodium in A-type zeolite can be replaced with magnesium or calcium, it is listed as a potential raw material candidate for zeolite synthesis. . If zeolite can be synthesized from steel slag having a composition relatively close to that of zeolite, not only cost reduction is possible, but also from the viewpoint of effective use of slag. Furthermore, zeolite can be used not only for heat storage materials but also for various purposes such as humidity control for buildings, purification of industrial wastewater, deodorizers, soil modifiers, etc. Development is expected.

  To synthesize A-type zeolite with high efficiency using blast furnace slag as a raw material from previous studies (for example, Non-Patent Document 3 and Patent Document 1), adjust the raw material composition to 15 mass% or less of magnesium oxide + calcium oxide. I found it necessary. For this purpose, a method of adding a silicon source and an aluminum source and a method of removing magnesium and calcium in the slag can be considered, and the former has been adopted in the previous studies, and the silicon source is an amorphous silicon oxide and an aluminum source. Has used sodium aluminate. However, since large amounts of these reagents are used at a high cost, they are not suitable for synthesis using steel slag with a large amount of generation. On the other hand, if magnesium and calcium can be selectively removed from blast furnace slag as the latter method, it becomes possible to synthesize A-type zeolite only from blast furnace slag.

  Until now, the elution behavior of metal ions from slag has been reported for elution of silicon and iron in a solution simulating the sea (for example, Non-Patent Document 4). Further, elution of silicon, aluminum, iron, and magnesium from minerals using organic acids such as oxalic acid, citric acid, and tannic acid has been studied (for example, Non-Patent Document 5). There is no report of removing and collecting calcium and calcium, and the method needs to be studied.

  As a report of pretreatment of blast furnace slag to synthesize A-type zeolite, after complete dissolution with hydrochloric acid or nitric acid, only silica gel is produced, and an aluminum source is added thereto to perform hydrothermal synthesis (for example, , Patent Document 2) and a method of hydrothermal synthesis by adding sodium carbonate to slag and firing at 1023-1173K, then acid-treating and washing with water at pH 4 or lower (for example, Patent Document 3). There is a disadvantage that a high-temperature heat source is required at the time of preliminary treatment, not slag alone. Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5 describe that the calcium compound in the raw material can be removed by treating the raw material powder with an aqueous acid solution, but the calcium selectivity is remarkably high. Low.

JP 2005-239459 A JP-A-8-259221 Japanese Laid-Open Patent Publication No.7-196315 Japanese Unexamined Patent Publication No. 7-232913 Japanese Patent No. 3660311 Yoshio Ono, Takeaki Yashima: Science and Engineering of Zeolite, Kodansha (2000) Annual report on steel slag statistics (2004 results), Steel Slag Association Y. Sugano, R. Sahara, T. Murakami, T. Narushima, Y. Iguchi and C. Ouchi: ISIJ International, 45 (2005), 937. T. Miki, T. Futatsuka, K. Shitogiden, T. Nagasaka and M. Hino: ISIJ International, 44 (2004), 762. H.Zhang and P.R.Bloom: Soil Sci. Soc. Am. J., 63 (1999), 815. Ken Tashiro, Kimihisa Ito: Steel slag generation reduction and resource recycling, Japan Iron and Steel Institute, (1997), 183.

  In order to realize a heat storage system that uses heat generated by water vapor adsorption on zeolite, it is indispensable to supply a low-cost, high-quality A-type zeolite having excellent water vapor adsorption characteristics, for example. For this purpose, it is possible to employ industrial by-products as the A-type zeolite synthesis raw material. In addition, effective utilization of industrial by-products such as blast furnace slag generated in large quantities has become an important issue, and it is used for cement raw materials and roadbed materials, but its usage tends to decrease in the future, New application development is required. The present invention provides a method for synthesizing A-type zeolite that can be mass-produced inexpensively using industrial by-products as raw materials. Furthermore, the present invention proposes a method for realizing the complete use of industrial by-products by removing and collecting substances unnecessary for synthesis from industrial by-products.

  According to the present invention, there is provided a magnesium and calcium removal and recovery method from steel industry by-products such as steel slag, wherein the magnesium and calcium removal and recovery method is characterized by dissolving and treating with formic acid or citric acid at room temperature. can get.

  Further, according to the present invention, there is obtained a magnesium and calcium removal and recovery method characterized by using a ball mill type reaction vessel in the dissolution reaction of the steel industry by-products such as the steel slag and the formic acid or the citric acid. .

  Moreover, according to this invention, the magnesium and calcium melt | dissolution solution is dried, sulfuric acid addition, or the carbon dioxide gas blowing, The magnesium and calcium removal collection method characterized by the above-mentioned is obtained.

  Moreover, according to this invention, the residue after the said magnesium and said calcium removal collection process is heated in an alkaline solution, The manufacturing method of the A-type zeolite characterized by the above-mentioned is obtained. As the alkali source, in addition to sodium hydroxide shown in this embodiment, the same effect can be obtained by using alkali metal hydroxides such as potassium hydroxide and lithium hydroxide.

  Moreover, according to this invention, the A-type zeolite manufacturing method characterized by heat-processing the said residue and the said alkaline solution in a ball mill type reaction container.

  The synthesis of A-type zeolite takes a long time and is expensive. A-type zeolite synthesized by various methods from industrial by-products also has a complicated process and is relatively expensive. In the present invention, blast furnace slag discharged in large quantities is used as a raw material, a ball mill type reaction vessel is used, the blast furnace slag is controlled to a composition capable of synthesizing A type zeolite, and further, A type zeolite by alkaline hydrothermal synthesis using the same vessel Made it possible to synthesize.

  In the present invention, by selecting an appropriate acid solution and adopting a ball mill type reaction vessel, not only soluble magnesium and calcium components, but also only magnesium and calcium components from glassy substances including blast furnace granulated slag can be selectively used. It can be removed and recovered. In this case, the acid species clarifies that organic acids, particularly formic acid and citric acid are effective. Furthermore, it is possible to recover the magnesium and calcium components from the solution after removal by drying, adding sulfuric acid, and blowing carbon dioxide. In particular, when the calcium content is dried, it is recovered as calcium formate, so that it can be used as a flowering effect agent or a concrete admixture.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The invention according to claim 1 of the present invention is that industrial by-products such as blast furnace slag represented by the composition shown in Table 1 are mixed at room temperature in a formic acid or citric acid aqueous solution having an initial pH of 2 as shown in FIG. By elution treatment, magnesium and calcium are selectively removed and recovered. As shown in FIG. 2, even when hydrochloric acid is used as the acid aqueous solution, selective removal and recovery cannot be performed, and acetic acid and lactic acid, which are organic acids, do not exhibit the same effect as the above acid.

  In addition, the invention according to claim 2 enables selective removal and recovery of magnesium and calcium more effectively as shown in FIG. 3 by using a ball mill type reaction vessel for the elution treatment as shown in FIG. Suitable acid aqueous solutions are formic acid and citric acid.

  Furthermore, the invention described in claim 3 is a method for recovering the magnesium and calcium sources and making them reusable by drying the solution generated by the above treatment, adding sulfuric acid, and blowing carbon dioxide. As shown in FIG. 7, calcium formate can be obtained by drying the solution treated with the formic acid aqueous solution.

  In the invention described in claim 4, by applying the invention described in claims 1 and 2, the elution residue composition is changed to a region where the production of A-type zeolite, which is clarified in Non-Patent Document 3, is possible. The residue can be heated in an alkaline solution to make it possible to produce A-type zeolite.

  Finally, the invention according to claim 5 uses the ball mill type reaction vessel shown in FIG. 1 for the synthesis of the A-type zeolite and heats and stirs it in a short time and as shown in FIG. This makes it possible to synthesize finer A-type zeolite than commercially available A-type zeolite having a particle size of 4 to 5 μm.

Blast furnace granulated slag containing 42.5 mass% CaO obtained in actual operation was used as a raw material. The slag composition is shown in Table 1. For elution treatment, hydrochloric acid (special grade, Wako Pure Chemical Industries, Ltd.), formic acid (special grade, Wako Pure Chemical Industries, Ltd.), acetic acid (special grade, Kanto Chemical Co., Ltd.), lactic acid (special grade, sum, Japanese) Kojun Pharmaceutical Co., Ltd.), citric acid (prepared from citric acid monohydrate (special grade, Wako Pure Chemical Industries, Ltd.)), and tartaric acid (special grade, Wako Pure Chemical Industries, Ltd.) were used. For comparison, elution treatment with ion-exchanged water was also performed. Using a constant temperature dryer (DO-300, Inei Seieido Co., Ltd.) and a ball mill type reaction vessel shown in FIG. 1, it was carried out by elution treatment at room temperature in various solutions. The reaction container is a double container in which a Teflon (registered trademark) container (inner diameter 40 mm, volume 60 ml) is placed in a stainless steel container, and the Teflon (registered trademark) container is sealed with an O-ring. The The constant temperature dryer is designed so that it can be heated by the lower heater and at the same time the reaction vessel can be rotated. Blast furnace granulated slag 1.0 g, 30 ml of various acid solutions adjusted to a predetermined pH, and 30 SiC balls (SiC11, Nikkato) having a diameter of 10 mm were put into a container and subjected to elution for a certain time while rotating at 75 rpm at room temperature. After the treatment, the precipitate was collected by suction filtration using a membrane filter (ADVANTEC) made of polycarbonate and having a pore size of 0.2 μm, and repeatedly eluted. For comparison, elution treatment was also performed by standing. In order to understand the elution behavior of metal ions, the concentration of Ca, Mg, Si, and Al ions in the filtrate generated at each elution stage was measured using an ICP emission spectrometer (ICP-8100, Shimadzu Corporation). It was measured. In order to recover the eluted magnesium and calcium, the filtrate was dried by adding sulfuric acid, blowing CO ₂ gas, and maintaining 343K. The residue was subjected to X-ray diffraction (XRD) by the 2θ-θ method using an X-ray diffractometer (X'Pert, Philips).

Fig. 2 shows the Ca ion concentration in the acid aqueous solution after 7.2ks elution treatment with various acid aqueous solutions with a pH value of 2. When tartaric acid was removed, the amount of elution increased when a SiC ball was placed and rotated, rather than with the treatment left standing. In addition, hydrochloric acid, which is an inorganic acid, hardly eluted Ca, but organic acid eluted more Ca. Especially formic acid and citric acid, the Ca concentration in the solution reached about 1100 ppm, and much Ca was dissolved. Was found to elute. Therefore, when citric acid and formic acid with the highest Ca elution amount were used and with the lowest hydrochloric acid, the composition of the residue obtained after the treatment together with the initial composition of the blast furnace slag was combined with SiO ₂ -Al ₂ O ₃ -CaO Plotted on the + MgO pseudo ternary phase diagram and shown in FIG. The hatched area is the composition in which the synthesis of A-type zeolite has been confirmed in previous studies. Elution with hydrochloric acid showed almost no change in composition from blast furnace slag. On the other hand, elution with citric acid or formic acid changed CaO + MgO from 49 mass% to 41-46 mass%. Furthermore, in the elution treatment with aqueous formic acid solution, the Si / Al ratio hardly changed, and there was a tendency to change to a composition suitable for A-type zeolite synthesis.

  FIG. 4 shows the Ca elution amount when the initial pH value of the formic acid aqueous solution is changed. The elution amounts of Ca and Si differed greatly depending on the initial pH value. Only when the initial value was 2, the elution amount was very large at 1150 ppm for Ca and 80 ppm for Si. The pH values after 7.2ks are 6, 10, and 11 when the initial pH is 2, 3, and 5, respectively. When the initial pH is high, the aqueous solution tends to shift to the alkali side, and Ca is eluted. It is thought that it was because it was suppressed. Therefore, it can be said that the initial pH of the elution treatment is most suitable around 2.

In the elution treatment of 7.2ks, the amount of magnesium oxide + calcium oxide did not reach the A-type zeolite synthesis range. Furthermore, the amount of magnesium oxide + calcium oxide did not change significantly even when the elution treatment was over 7.2ks. Fig. 5 shows the relationship between the number of cycles and the initial weight of the elution weight of each element (W / W _initial ) when filtration was performed after elution treatment of 1.8 or 7.2ks, and the elution treatment was performed again after changing the solution. Show. Although there was no significant change in the elution amounts of magnesium and calcium with the difference in elution time of one cycle, the elution amounts of silicon and aluminum tended to increase when the treatment was performed every 1.8ks. In the case of 1.8ks, the membrane filter was clogged during filtration, and it took a long time for filtration. Tashiro et al. Investigated the time variation of the elution amount of each metal element in 317K water of calcium oxide-silicon oxide-calcium fluoride system slag, and calcium, silicon, and sodium took maximum values at 36 to 54ks, and then decreased This shows a model in which a calcium oxide-silicon oxide-water gel is formed on the slag surface as the elution time elapses and then precipitates (Non-Patent Document 6). In this experiment, formic acid is used instead of water, but the slag composition is similar and the same phenomenon is considered to occur. Furthermore, it is considered that elution is accelerated by the ball mill, and therefore the maximum time is expected to be between 1.8 and 7.2ks, which is shorter than Tashiro et al. For these reasons, it was found that the solution exchange is more suitable for elution of magnesium and calcium every 7.2ks. Furthermore, at every 7.2ks exchange, elution of magnesium and calcium progressed rapidly by 3 cycles and remained almost unchanged thereafter. On the other hand, silicon behaved in the same way as magnesium and calcium up to 3 cycles, but it eluted slightly after that. In addition, aluminum hardly eluted until 2 cycles, and the dissolution proceeded slowly thereafter. Silicon and aluminum are elements that form the structural skeleton of A-type zeolite, and it is desirable to avoid loss due to elution as much as possible considering that it is used as a raw material for zeolite synthesis. The residual composition at each cycle is shown on the phase diagram together with the blast furnace slag composition in FIG. It was found that three cycles of treatment entered the region where A-type zeolite could be synthesized, and then deviated from the region capable of synthesis by further elution treatment. For this reason, it is optimal to perform the elution process for 3 cycles of 7.2ks.

Here, the filtrate at the end of one cycle was kept at 172.8ks at 343K and the water was evaporated to obtain a white powder precipitate. This powder was able to recover 0.38g from 1g of blast furnace slag. From the XRD pattern of the precipitate shown in FIG. 7, it was found to be calcium formate ((HCOO) ₂ Ca). Calcium formate is used as a flowering effect agent and a concrete admixture, and has the potential to supply inexpensive calcium formate as a concrete admixture that is consumed in large quantities. In addition, it was possible to recover as a sulfated oxide and a carbonated carbonate by adding sulfuric acid and blowing CO ₂ .

The residue after the elution treatment was used as a raw material for synthesis, and zeolite synthesis was performed by hydrothermal treatment in a NaOH solution using the above ball mill type reaction vessel. 240 pieces of 5mm diameter SiC balls and 15ml of 1M NaOH (purity 96.0% or more, Wako Pure Chemical Industries, Ltd.) solution are put in a container together with synthetic raw materials, and hydrothermal treatment is carried out by 86.4ks direct synthesis method at 343K. It was. During the hydrothermal treatment, the reaction vessel was rotated at 75 rpm. After hydrothermal treatment, the precipitate was filtered, washed with ion-exchanged water, and dried at 343K in a constant temperature dryer. The compound was identified by XRD. Furthermore, the calibration curve method by XRD was used for the quantification of type A zeolite in the composite. MgO powder (purity 99.9%, Wako Pure Chemical Industries, Ltd.) was used as the standard substance, and the amount added was 50 mass%. The calibration curve is a ratio of commercially available A-type zeolite powder (268-01522, Wako Pure Chemical Industries, Ltd.) and MgAl ₂ O ₄ powder (purity 99%, Alfa Aesar) in a ratio of 3: 7, 5: 5, 7: 3. It was made using the powder mixed in Furthermore, a scanning electron microscope (SEM, XL30FEG, Philips) was used to observe the surface of the composite after hydrothermal treatment. The observation sample is agglomerated after filtration and drying. To disperse, the suspension obtained after ultrasonic cleaning in ethanol is dropped onto the observation holder, and the ethanol is evaporated in the atmosphere for SEM observation. Provided.

A direct synthesis of A-type zeolite was attempted using only the residue after three cycles. The composition of the residue at that time was a value calculated in consideration of the elution amount from the composition of the blast furnace slag, and was 22.5 mass% SiO ₂ -11.2 mass% Al ₂ O ₃ -3.8 mass% CaO-0.3 mass% MgO . Fig. 8- (a) shows the XRD pattern of the compound obtained after 86.4ks hydrothermal treatment in 1M NaOH solution at 343K. For comparison, Fig. 8- (b) shows the XRD pattern of a composite obtained by synthesizing everything including the raw material composition using the raw material with amorphous SiO ₂ and NaAlO ₂ added to blast furnace slag. . Even when only the residue after elution treatment was used, A-type zeolite was synthesized in the same manner as the raw materials reported so far. However, unlike the conventional material of (b), the peaks of tobermorite and hydrogarnet were not confirmed, and the formation of Na-P1 (Na ₆ Al ₆ Si ₆ O ₃₂ · 12H ₂ O) was confirmed. This is because the ratio of CaO + MgO in the raw material is 10%, which is lower than before, and the production of tobermorite and hydrogarnet with high CaO composition is suppressed, and the Si / Al ratio is higher than before, so it is Si rich. It is thought that Na-P1 was generated. The production rate of A-type zeolite was about 45% for the product from the raw material to which amorphous SiO ₂ and NaAlO ₂ were added, whereas it was 51% for the product only from the residue after the elution treatment. FIG. 9 shows SEM photographs of the blast furnace slag (a), the residue (b) after the formic acid treatment, and the composite composed solely of the residue. The blast furnace slag before formic acid treatment has a smooth surface shape, but by performing the formic acid treatment, the irregularities on the surface increased and the number of small grains increased as a whole. The synthesized product has almost the same shape as that containing the conventional A-type zeolite, but tends to have many small particles.

As a report of pretreatment of blast furnace slag to synthesize A-type zeolite, after completely dissolving with hydrochloric acid or nitric acid, only silica gel is generated, and Al source is added to the hydrothermal synthesis (patented) Document 2) and, after firing at 1023~1173K added Na ₂ CO ₃ to slag, acid treatment and washing with pH4 or less, there is a method (Patent Document 3) to perform hydrothermal synthesis, these blast furnace slag alone There is a disadvantage that a high-temperature heat source is required instead of raw materials. Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5 describe that the calcium compound in the raw material can be removed by treating the raw material powder with an aqueous acid solution, but the calcium selectivity is remarkably high. Low.

  On the other hand, this study is superior to conventional methods in that the elution process is performed at room temperature and the residue is used as it is for hydrothermal synthesis. In addition, calcium compounds can be selectively removed by using formic acid or citric acid.

Schematic of a ball mill type reaction vessel for elution treatment and hydrothermal synthesis. Ca concentration after elution treatment of granulated blast furnace slag for 2 hours at room temperature when using a ball mill type reaction vessel with various acids and standing. SiO ₂ —Al ₂ O ₃ —CaO + MgO phase diagram plotting the composition after elution treatment from granulated blast furnace slag at room temperature for 2 hours using formic acid, citric acid, and hydrochloric acid. Elution amount of Ca, Si and Al from blast furnace granulated slag due to differences in initial pH of formic acid. The number of elution treatments for 2 hours with a formic acid solution with an initial pH of 2 from granulated blast furnace slag and the weight reduction rate of Ca, Mg, Al, and Si. SiO ₂ -Al ₂ O ₃ -CaO + MgO phase diagram plotting the composition of the residue from the granulated blast furnace slag with a formic acid solution with an initial pH of 2 at room temperature for 2 hours, elution times 1, 3, 6 . X-ray diffraction pattern of the powder obtained by drying the solution after the elution treatment. Silica and sodium aluminate were added to the product and hydroblastic slag from the residue obtained after 3 times of elution treatment at room temperature for 2 hours with a formic acid solution with an initial pH of 2 from granulated blast furnace slag and blast furnace slag. X-ray diffraction pattern of the product hydrotreated by using raw materials with added Si / Al = 1 and CaO + MgO = 15 mass%. Electron micrographs of blast furnace slag as raw material, residue after elution treatment with formic acid, and product after hydrothermal treatment using the residue.

Claims (5)

  A method for removing and recovering magnesium and calcium from steel industry by-products such as steel slag, wherein the magnesium and calcium are recovered by treatment with formic acid or citric acid at room temperature.   The magnesium and calcium removal and recovery method according to claim 1, wherein a ball mill type reaction vessel is used in the dissolution reaction of the steel industry by-products such as steel slag and the formic acid or the citric acid.   A method for removing and recovering magnesium and calcium, comprising drying the magnesium and calcium solution according to claim 1 and adding sulfuric acid or blowing carbon dioxide.   A process for producing A-type zeolite, wherein the residue after the magnesium and calcium removal and recovery treatment is heated in an alkaline solution.   The A-type zeolite production method according to claim 4, wherein the residue and the alkaline solution are subjected to a heat treatment in a ball mill type reaction vessel.