JPS591602A - Production of iron powder for industrial purpose using converter off-gas dust - Google Patents

Abstract

PURPOSE:To separate and recover easily the iron powder for industrial puposes that can be used for various applications by recovering the iron dust contained in the combustible waste gas generated during the operation of a converter by a wet tratment in the stage of recovering said gas. CONSTITUTION:Water is sprayed 2 to the CO-contg. waste gas 1 obtd. in the stage of operating a converter, and the dust 4 in the waste gas is recovered with a scrubber 3. Clean gas 5 is sent for a device intended for using said gas. The recovered dust 4 is separated to dust 8 and overflow water 9 with a dust pit 6 and a classifier 7. Since the dust 8 consists cessentially of Fe and contains FeO, SiO2, CaO, MgO and others, the dust is first ground by impact compression with a ball mill or the like, so that 25-40% thereof passes through 200 mesh. The ground poweder is separated of Fe with a wet magnetic separator and further the dust is again ground by impact compression in an aq. mineral acid soln. of 0.3-0.9N HCl added with a suitable inhibitor, whereafter the dust is rinsed and deslimed, and the iron powder having high purity is recovered.

Description

[Detailed Description of the Invention] Regarding the method for producing ferrous iron powder, iron dust obtained along with gas in an OG gas recovery device (wet type dust recovery device) for recovering carbon monoxide generated during oxygen steelmaking using a converter is used. It is an object of the present invention to provide a method for producing industrially useful metallic iron powder.

Various uses of metallic iron powder have been developed over the years, and among these, representative industrial raw materials include powder metallurgy, welding rods, and chemical body warmers (using the heat of reaction with oxygen).
These products are used as deoxidizers for food preservation, food preservation, etc., and each of these needs to meet the required ingredients, grade, and particle size conditions as shown in the first report below.

Table 1 Specifications for Metallic Iron Powders by Application By the way, 99% of the metal iron powders currently used industrially as described above are produced by the spraying method and the reduction method, but each method has disadvantages and drawbacks.

In other words, the atomized iron powder is produced by spraying high-pressure water or inert gas onto molten steel, but the atomized iron powder that is produced is spherical in shape, and when it is sprayed, it is rapidly cooled, resulting in a hardened state. Since an annealing process is required in a reducing atmosphere containing carbon, the manufacturing process is complicated and costs inevitably increase. In addition, the reduction method is produced by reducing high-grade iron ore or mill scale in a tunnel kiln, but this method requires particularly high-quality raw materials and eliminates coke and coal ash and coke that are mixed in during reduction. In order to remove limestone, etc., it is necessary to repeatedly perform crushing and magnetic separation, and in order to freshly decarbonize, a final reduction process in a hydrogen atmosphere is required, similar to the case with atomized iron powder. Crude metal iron powder obtained by this reduction method (without finishing reduction with hydrogen gas) is also used as metal iron powder for deoxidizing agents for chemical body warmers or food preservation, and as part of flux for welding rods. However, in any case, the manufacturing process is more complicated than the sprayability, and the reduction method in particular has problems such as the need for high-quality raw materials.

The present invention was devised after repeated studies and speculations in view of the above-mentioned circumstances, and is intended to produce high-quality products through a simple manufacturing process using easily and readily available raw materials. Successful. That is, as a result of careful study of various raw materials for the above-mentioned purpose, the present inventors found that
The dust obtained during the wet dust collection process during converter steel production in a steel mill (referred to as OG dust in the present invention) has a composition with T and Fa of 78 to 88 as shown in the second column below.
%, M, and Fa are high at 60 to 70%, and the content of metallic iron is particularly high, and the content of ferric oxide is very low, indicating the possibility of upgrading through refining.

26th Component analysis of OG dust Moreover, the amount of generated OG dust is, for example, 250 T/
It is a very large amount, about 600 T per day on a single furnace scale, and its effective use or preferred refining method has great industrial merits. This OG dust is obtained by collecting molten steel, which evaporates or scatters during the blowing process in the oxygen steelmaking process, after cooling and solidifying in a reducing atmosphere gas, as shown in the fud-sheet in Figure 1. , the solid content is separated and recovered as recovered dust 4 by a scrubber 3 that collects dust by spraying water 2 on the converter exhaust gas 1, and OG gas 5 is separated from the scrubber 3. , the collected dust 4 is appropriately replaced with a dust bit 6, a filter 2, a shifter 7,
It is separated into OG dust 8 and overflow fraction 9 through this process, but it has been known for a long time that such OG dust has a high metal iron content. However, as seen in Section 26 above, since slag components such as CaO and 5L02 are present in large quantities, there is currently no way to effectively utilize them, and at most they are used as sintering raw materials. It is used and used only. However, the origin of this OG dust is that iron vapor is generated from molten iron in the extremely boiling state of molten steel during oxygen steelmaking in a converter, and at the same time it condenses with the presence of slag that was volatilized during the 7 lashing process. Alternatively, it has been thought that molten metal iron entrains and condenses as droplets together with slag powder, but as a result of the inventors' detailed study of the properties of OG dust, it was found that OG dust As shown in the micrograph shown in Figure 5, the calcium silicate-based slag, which has a core of high-purity metallic iron particles and has been rolled up with free lime, is hard and adheres to the secondary surface, and almost no iron compounds are present. It was confirmed that it did not exist. In addition, the diameter of this metallic iron particles is 40 to 250 pm (
It is estimated that the fine powder part in the OG dust is the part where molten iron vapor condensed.
Similarly, the fine powder part in the OG dust is presumed to be a part where molten iron steam is condensed, and is also in a mixed state with fine slag.

Based on the above-mentioned new discoveries and confirmations, the present inventors deduced that it is possible to refine highly pure metallic iron particles (40 μm or more) if they can be extracted by physical abrasion means. In other words, the method for producing this OG dust is to wet-pulverize the surface of granulated iron using a crusher such as an impact-compression type ball mill, rod mill, or vibration mill, and then
A method was adopted in which the slag was separated using a wet method using a low magnetic force magnetic separator smaller than Gau Z. Figure 2 shows the experimental results using the lid grinding method. Looking at the relationship between the pulverized particle size and the iron grade (h%) and magnetization yield (yield %) of magnetically beneficent concentrate, the iron grade Regarding 25 to 40 cIb passing through 200 meshes, the abbreviation is as high as 95 inches, while the magnetization yield, that is, the yield rate, decreases as the proportion of passing through 200 meshes increases; I learned that it drops dramatically from around 20%. That is, if the pulverized ore is insufficient and the particle size is coarse, the separation of the slag component is insufficient, so the magnetization yield of the pulverized material is high, but the purity of iron is low. On the other hand, as the pulverization progresses and the amount passing through 200 meshes exceeds 40%, the magnetization yield and the purity of iron begin to decrease. This is thought to be due to part of the slag being over-pulverized and not sufficiently separated during the magnetization process, and part of the surface of the metal particles being crushed and mixed with the slag and entering the non-magnetized portion. It was done.

From the above study results, it is recommended that the degree of abrasion in OG dust by the wet method using an impact compression type pulverizer be so that the degree of abrasion is within the range of 25 to 4 degrees when passing through 200 meshes. The conclusion was reached that it is advantageous for industrialization in terms of the purity and yield of iron powder (granular iron).

In other words, specific processing under such processing conditions will be described in Example 1 below, but as seen in the analytical values and degree of purification of the obtained metallic iron powder, the impurity concentration is T, Fa, etc.
Based on the impurity degree (100) of the raw ore, CaO is 18%, A40 is 20%, 5stone is 2
6, Mr+Q was 46q6, S was reduced to 80%, and the purification rate was extremely good. Further, the iron powder obtained by such magnetic separation treatment is dried in a reducing or inert atmosphere, and the chemical composition of this iron powder is T and FJ of 95.
~96%-, 88-90% in M-Fa, 5t02',
Q2~(13% 5CaO: Q56~065%, 0:025~035%, and can be appropriately used as a welding rod, deoxidizer, and metallic iron powder for chemical body warmers, and can be used using known technology. It was confirmed that when the briquette is shaped into an appropriate shape, it can also be used as a high-grade coolant for steelmaking (commonly known as punch scrap).Also, comparing Table 1 above, it is clear that it is not suitable for use in powder metallurgy. Since the content of impurities is quite large and unsuitable, the inventors of the present invention have conducted repeated studies on increasing the degree of H production with the aim of obtaining metallic iron powder for powder metallurgy.

In other words, as a result of various studies, we have come to the conclusion that it is not possible to exceed the degree of refinement shown in Section 3, which will be described later, only by the physical means of grinding. In other words, this means that it is difficult to remove the slag containing calcium (free lime) or calcium silicate that adheres to the minute depressions of iron particles by physical means such as grinding (polishing) alone. This is due to Therefore, the present inventors have further investigated the possibility of improving the product quality by using a treatment with a dilute mineral acid in combination. In other words, the iron powder obtained by magnetic separation using the grinding ridge wet method as described above is dehydrated. 25
When the iron powder was further ground in a dihydrochloric acid aqueous solution using a II shock compression type crusher and then subjected to a squim removal treatment, the above-mentioned impurities could be largely removed, and the purity of the iron powder was significantly improved. was completed. In other words, it was confirmed that by using such an acid treatment in combination, the slag components adhering to the recessed portions of the particles could be appropriately removed.

Therefore, in order to establish conditions for using this acid treatment in combination, we changed the acid concentration of the hydrochloric acid aqueous solution, and changed the acid concentration and content of CaO and StO, which are indicators of the degree of a-product, and the chemical conversion rate of metallic iron particles. Figure 3 shows the result of finding the relationship between (M, FJT, Fa). That is, as is clear from FIG. 3, CaO and 5tO2, which are the main impurities in the iron powder, steadily decrease with increasing acidity, and the effect is significant at 1% or more. On the other hand, the metallization rate decreases rapidly when the acid concentration exceeds 3%, and this is because as the acid concentration increases, not only the slag containing free lime is dissolved, but also the metal iron itself is dissolved and lost. This is thought to be because the activated metal surface becomes more easily oxidized. Note that when this mineral acid treatment is used in combination, free calcium (free lime) is dissolved first, and then calcium silicate is dissolved. Also, in this type of mineral acid,
When targeting calcium content, hydrochloric acid is preferable because sulfuric acid originally forms calcium sulfate, but in reality, the absolute amount of calcium content is reduced by pretreatment, and the solubility of calcium sulfate (02 %), and even if calcium sulfate precipitates, it can be removed in the subsequent desliming process, so sulfuric acid can be used without problems.

Regarding the concentration of the mineral acid mentioned above, as shown in FIG. 3 above, the concentration of other mineral acids also corresponds to the normality (g) which corresponds to the concentration (%) of hydrochloric acid. In other words, the standard is 0844 N C (186N) for 3T hydrochloric acid solution, and 4T (186N) for sulfuric acid solution.
Q84N) becomes a solution.

Based on the above results, the mineral acid concentration used for this treatment is Q3.
It is recognized that N to Q9N is appropriate. When Hibiton A-5, manufactured by Matsuzai Kagaku Co., Ltd., which is commercially available as a pick-cling inhibitor, was added to the hydrochloric acid solution, the metallization rate (M, Fa/T , Fa
) curve suddenly dropped at 7% Hc/(2N). That is, in normal work, the concentration of mineral acid is 03~(19
However, by adding such an inhibitor, it is possible to stabilize the concentration up to about 2N and use it for a long life.

When combined with dilute acid treatment as described above,
The process is as shown in Example 2, which will be described later, and the results are as shown in the fourth layer and FIG. In other words, in Figure 4, "Yuan"
is the original ore, rGJ is the rhinoceros ore magnetic separator, and "G+P" is the case where this grinding ore magnetic separation and pickling ore concentrate are used together. Concentration (100
), 3% for CaO, 5% for MJO, 1 for StO,
0% for MnO, 22% for MnO, and 60% for S, the refining rate is extremely good, and the combined treatment of grinding magnetic separation and pickling grinding desliming is extremely effective, and it is suitable for powder metallurgy. It is confirmed that iron powder of appropriate grade can be obtained.

Specific examples of the method according to the present invention will be described below.

Example t Put OG dust/ioo Kf (dry paste) and 55 tons of water into a patch type rod mill (pulp concentration: about 65%),
After crushing and grinding for about 30 minutes, wet magnetic separation was performed using an 800 Gauss drum type magnetic separator, and dehydration was performed using a filter to recover 1' (79 Kf (yield: 79%) of iron powder in terms of dry amount. The particle size of the iron powder was 32mm, which passed through 200 meshes.The grade of this iron powder was as shown in the column of @3N magnetically separated concentrate below, and it was used for welding rods, chemical warmers, food preservation, etc. The quality was suitable for use as a raw material for acid agents.

Example 2 74 kg of iron powder containing about 55% moisture obtained by treating the same OG dust source ore as in Example 1 and 401 3% hydrochloric acid solution were placed in the patch type rod mill described above. (Bulb concentration: about 65%) The product was ground for about 15 minutes, removed from slime using a wet cyclone, washed with about 200 tons of water, dehydrated with a filter, and dried in an inert atmosphere to obtain purified iron powder. The grade of the obtained iron powder is shown in No. 46 below, and it was suitable as a raw material for powder metallurgy.

4th Figure 4 summarizes the results of the 4th experiment and the results of Table 3 above, and as mentioned above, the results are favorable.

According to the present invention as described above, OG dust generated during oxygen steelmaking using a converter can be used to appropriately produce metal iron powder for various industrial purposes, and the manufacturing process is relatively simple. This invention is simple and, in combination with using dust as a raw material as mentioned above, has the effect of producing the desired metallic iron powder at a relatively low cost, and has a large industrial effect. It is.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and Fig. 1 is an explanatory diagram of OG dust 1!170-sheet from converter exhaust gas, and Fig. 2 is an illustration of the relationship between the crushed particle size and the castella grade. Figure 3 is a diagram showing the relationship between hydrochloric acid concentration, impurity concentration and metallization rate, Figure 4 is a diagram summarizing the results obtained in the example for OG dust, Figure 5 is a micrograph with a magnification of 200 times showing a cross section of OG dust. In these drawings, 1 indicates converter exhaust gas, 2 indicates water spray, 3 indicates scrubber, and 8 indicates OG dust. Patent applicant Nippon Kokan Co., Ltd. Steel Tube Mining Co., Ltd. Inventor Yukio Yamaguchi
Kiyodo Watanabe
Tatsu Kumai
Yamashita Middle
Saito Yohemi J No. / L / No., 2 Kan No. J Ensaki fill No. 5 Ensaki amendment form (＠手p Showa Tough. 8. Ki5 tl Patent Office Skills Kazuo Sugi 1, Indication of the case Showa r?i7w No. tOFE36 et al. No. 3, Person making the amendment Name of the patent applicant related to the case (Mr. Genu Book #I Suga Co., Ltd. Iiro 164, Agent Showa Month/Day Issued λX66 Subject of amendment #Nff1 7. Contents of the amendment As shown in the attached sheet, the amendment is in
Correct the text "V and" to "approximately 600 I' per month." [Acknowledgement, same 7 Tei 1] From which line to 12th line C? :, a. Also, delete the description ``Fine powder part in OG dust d Bath iron is the part where steam is vertically drawn n, J''. "J stop with i2.5 noble hydrochloric acid water M," FiT corrected. [Please do] 5 Liao ``Third group'' is corrected in the lower angle. 16 廁 [Table 4 J is corrected as follows.・
O, I corrected the same I7 7 What a r4q effect 5 Ministry of Iron Powder as J and Φ as 1 "儒゛Youl Firefly - Iron Powder."

Claims (1)

[Scope of Claims] 1. Industrial iron using converter OG dust, characterized in that the converter OG dust is impact compressed and crushed, passed through 200 meshes, crushed to 25 to 40 pieces, and then magnetically sorted by a wet method. How to make powder. 2 Converter OG dust is subjected to impact compression pulverization, passed through 200 meshes, crushed to 25-40%, and then magnetically sorted using a wet method to obtain metallic iron powder. A method for producing industrial iron powder using converter OG dust, which is then washed and then subjected to a desliming treatment. 3. Converter OG dust according to claim 2, in which an inhibitor is added to the mineral acid. A method for producing industrial iron powder using