KR19980703606A - Waste metal-containing waste treatment method, fine powder manufacturing method for metallurgical process, and feedable air - Google Patents

Abstract

Wastes containing heavy metals are mixed with oily mill scales or reduced iron ore fines until a brittle product is produced, and mixed with a carrier of fine grains with low density, so that fine grains between 0 mm and 6 mm are transferred to the metallurgical furnace. It can be sieved for injection. Water may be added to the mixed product using a wet carbon containing slurry. Lime-containing dust may also be added.

Description

Waste metal-containing waste treatment method, fine powder manufacturing method for metallurgical process and air injectable feed

1 schematically illustrates one process of the invention.

2 is a graph illustrating an exothermic reaction.

Explanation of symbols for main parts of the drawings

1: rolling mill stand 2: high-grade steel slab 3: thin plate

4: nozzle 5: water 6: rolling mill scale

7: rolling mill stand 8: gutter 9: power plant boiler

10: coal 11: hot flue gas 12: heat exchanger surface

13: boiler feed water 14: steam 15: fly ash

16: chimney 17: rolling mill scale slurry 18: first mixture

19: sieve 20: fine fragment 21: filamentous product

22: second mixer 23: Atan coke dust 24: spherical

25 filter 26 capacitor 28 quartz crystal grain

29: pipe 32: blower 33: furnace

34: steam turbine

As shown in FIG. 1, the high quality steel slab 2 is stretched into a thin plate 3 in a rolling mill. Water 5 is added to the rolling process through the nozzle 4 under pressure. The mill scale 6 is collected into a mill scale slurry 7 in a trough 8 under the mill stand 1.

Coal 10 is burned individually in power plant boiler 9. The generated hot flue gas 11 is converted to steam 14 on the heat exchanger 12 past the heat exchanger surface 12 through which the boiler feed water 13 circulates. The flue gas 11 leaves the boiler via the electric filter 33. And before being discharged to the atmosphere through the chimney 16, the finely divided fly ash 15 is transferred and separated from the flue gas.

The mill scale slurry 7 and the separated fly ash 15 are fed to the primary mixer 17 and mixed intimately. The rolling mill scale slurry 7 moistened during mixing with the fly ash 5 forms a mass product having a hardness for drying and breaking. Exothermic reactions cause water to evaporate. The first mixture 18 leaving the mixer 17 has a temperature higher than the atmosphere and passes through the sieve 19 to collect the fine debris 20. The filamentous product 21 in the sieve 19 contains foreign matter and impurities previously present in the mill scale slurry 7 which are discarded. The fine debris 20 having a grain size range of 1 mm or less flows into the secondary mixer 22 and is mixed with lime-containing spherical masses and attan coke dust 23 having an average grain size between 0.5 and 2 mm.

The sphere 24 exits the filter 25 and the boiler feed water 13 of the power plant boiler 9 is ready for turbine passage. The steam 14 flows through the condenser 26 after the pressure is reduced in the steam turbine 34 and condenses again to form the boiler feed water 13. The condensed boiler feedwater 13 goes through a filter 25 to a feedwater pump. Quartz crystals 28 are added to the filter 25 and the lime and iron contained in the boiler feed water 13 accumulate to form a sphere 24. The loss of boiler feed water 13 is compensated for by fresh water introduced via pipe 29.

The agglomerated product 30 is composed of finely divided metal, lime and carbon and remains in the second mixer 22 to have a dry powder-like hardness composed of grain size between 1 and 6 mm and an average specific gravity of 2 g / cm ³ . And it may be injected into the furnace by the blower (32).

In the assessment that direct reduced iron will be used, different amounts of water are sequentially added and stirred to 1 kg of granular sponge iron. The reaction of iron oxide with water is measured by the temperature increase observed in the process. The measured values are recorded in Tables 1 to 3 and shown in the corresponding graphs of FIG.

Initial material: 1 kg of ultra fine sponge iron in crusher at 20 ° C

50 grams and the equivalent of 5 percent by weight Minutes Temperature (℃) 0 20 2 23 4 23 6 24 8 24 10 24

This result is shown in FIG. 2 and it can be seen that the temperature rises by 4 ° C. for 6 minutes and remains constant thereafter.

Another 50 grams of water was added to the mixture in Table 1 and stirred by hand for 4 minutes. Minutes Temperature (℃) 0 25 2 26 4 27 6 27.5 8 28 10 29 12 30 14 31 16 32 18 32 20 32 22 32

This result is also shown in the graph. The temperature rises by 7 ° C. for 16 minutes and remains constant thereafter.

Again 50 grams of water was added to the mixture in Table 2 and stirred by hand for 3 minutes to determine the temperature. Minutes Temperature (℃) 0 32 2 32.5 4 33 6 33.5 8 34 10 34 12 34.5 14 35 16 35 18 35.5 20 35.5 22 35.5 24 35.5

This result is shown in the graph. The temperature rises slowly for another 18 minutes by 3.5 ° C. and remains constant thereafter.

As can be seen from the table, the most fierce reaction begins in mixing step 2 and gradually declines in mixing step 3.

The present invention relates to a method of using a wide range of metal-containing materials that are difficult to dispose of or just thrown away as trash.

One suitable metal is iron ore fine dust, which is difficult to process. Fine ores having a grain diameter of about 0.2 mm or less are soaked during coarsening and mixed with a binder, for example bentonite, to form agglomerates. Ingots are either flame hardened or sintered because these powders are the only methods that can be used in later metallurgical processes, similar to the direct reduction of powders known as COREX ^® , MIDREX ^® , or HYL ^® . . For example, in the case of the ^MIDREX® process, the fine ores are operated by reducing gases in bed reactors fluidized at temperatures between 500 ° C and 800 ° C. The reducing gas contains H ₂ and CO and also contains CO ₂ , H ₂ O, CH ₄ , N ₂ . Processing takes place in a series of fluidized bed reactors connected in series and the reduction is increased from reactor to reactor to reach metallization values between 92 and 94% at the exit of the last fluidized bed reactor. The fine powder reduced in this way is thermally briquettes to obtain the mass form required for the later metallurgical process. During the above sintering and processing of fine powder, iron dust is collected, which are very fine and the reaction is extremely reactive. The fine dust also contains some of the unconverted carbon. Such powders are too high to be blown by the wind or injected into metallurgical furnaces.

Other heavy metal-containing fines or slurries are generated as by-products during the manufacture and processing of high-grade steel. High-grade steel generally refers to the quality of steel made of heat treatment such as quenching and soaking. Higher grade steels are of higher quality or higher purity than base steels (cf. Brockhaus, Naturwissenschaften und Technik (Natural Science and Technology), special edition 1989, volume 1, key word). Such steel is produced in electric arc furnaces from steel scrap and alloy compositions. The smoke contained in the smelting gas is very finely divided and has a high specific gravity of more than 4 grams per cubic centimeter. The dust is separated from the electric filter installed on the other side of the furnace. In addition, it is common to generate a heavy metal-containing slurry by washing off the dust from the smelting gas using water. Scrap charging usually contains zinc which is evaporated to a high temperature in the metallurgical vessel and is put in the flue gas. In the case of fumes from dry fume extraction (containing heavy metal zinc) or wet fume extraction, the slurry has to be disposed of in a particular waste stream or has to be subjected to expensive segregation.

For such zinc-containing dusts or slurries, this is a great economic benefit if the zinc content is reused to rise to 25% or more, such as 40% or more.

High quality steel can be processed in rolling mills. In this case, very heavy mill scale slurry contains not only metal components but also impurities in the form of lumps in metal parts, organic materials or plastics. Large pieces of metal such as screws, cleaning rags, cigarette butts, work gloves, yogurt boxes, and plastic bags can be thrown away by sloppy workers in rolling mill scale slurries.

All metal dusts and slurries that occur during the production of basic, fine, high quality steel are finely divided (fine granules in the range of grains from a few microns to 1 mm) and contain alloy metals. These alloying metals mainly contain chromium, cobalt, nickel, lead, manganese, tungsten, titanium, vanadium, zinc, and molybdenum and are added together with iron in each grade of steel in varying amounts according to a preset treatment method. This affects the dust and slurry weight. Although these dusts and slurries contain valuable materials, it is not possible to recycle and reuse these materials satisfactorily because of their inherent purity and weight. In many cases dust containing valuable substances is discarded, but this is bad for the protection of the environment and uneconomical.

It is an object of the present invention to provide a method for recovering valuable components from a wide variety of wastes and introducing them into a metallurgical vessel for recycling in a particularly convenient way.

According to one aspect of the present invention, there is provided a waste disposal method containing heavy metals. The method involves mixing waste with a relatively small density of particulate matter containing metal oxide material and water to exothermic to form relatively dry agglomerates; Sifting out masses having a size ranging from about 0 mm to about 6 mm; And injecting the separated mass into the metallurgical vessel containing the molten metal with air under reduced pressure.

The oxide material may be quicklime or directly reduced iron. Most preferably the mass is injected with carbon (this is necessary for other purposes in metallurgical vessels, such as reduction reactions). Carbon can come from a variety of sources and may already be in the waste.

Carbon bearing carriers can be used where little or no carbon fines are used. Suitable materials are coke, or petroleum coke, consisting of coal or peat or lignite. This is because these cokes are particularly suitable for transferring fines to the surface due to their surface structure and porosity. Nevertheless, finely divided or dusty fragments of coal or peat are suitable as carrier materials, as are finely divided into lightweight fragments in the crushing of plastics. The latter tend to form masses that resemble flakes, and injection in this form is not possible.

One criterion for the selection of a suitable carrier is the foam of the slack. Therefore, for the injection into an electric arc furnace or a molten iron furnace, a carbon-containing carrier material exhibiting a low volatile content is preferable. These include attan coke, anthracite, petroleum coke, and coke pulverized coal. For injection into the furnace, a carbon-containing carrier having volatile content is best. The amount of volatiles in the total carbon content of the carrier must be greater than 8%. Atan, as well as other low coal fired materials such as coal, wood chips and vinyl chips can be used.

In order to promote foaming of the slag, the product should have a carbon content between 20 and 40% by weight. The carrier may be selected and determined by preanalysis.

To be complete, the mixture, the reaction solution, and the bound product should be defined to represent the amounts of Fe, FeO, Fe ₂ O ₃ , CaO, CaCO ₃ and the residual humidity to be between 5 and 15% by weight.

The present invention also utilizes the reactivity of the fine powder. Depending on the degree of metallization, the fine powder reacts with water to release heat and form iron oxides. Iron oxides are formed when the slurry and fine powder are reacted. The heat released during the exothermic reaction evaporates some of the moisture, making the mass easier to break.

For injection, the mass should have a density of about 1,2 to 4 g per cubic centimeter. The delivery cross section of a standard injection device between ½ inch (about 12 mm) and 2 inch (about 50 mm) is required to sift the product for grain sizes of about 6 mm or less in diameter. Standard injection pressures are about 4-5 bar for electric arc furnaces and about 5-6 bar for furnaces.

Mixing of the dry vehicle and the fines can be done directly, indirectly, in any order of steps. For example, the fines and the carrier may be mixed first, followed by water or a moist carbonaceous slurry if appropriate. Or the carbonaceous slurry and the carrier are first mixed together and then mixed with the fines. It is possible to simultaneously mix the fines, the carrier and the slurry containing carbon.

The evaluation of injecting fines, oil-containing rolling mill scale slurries, fine coal, petroleum coke, or furnace filter dust and a mass composed of quicklime or calcium oxide into an electric arc furnace was as follows. The finer fragments of the binding product, which were sieved with a grain size of 4 mm or less, resulted in a better change of the injected product in the molten metal than the grain fragments of diameter 6 mm or less.

Fragile blocks can be easily stored. It is inactive as soon as it reacts and is suitable for air transport. It is possible to inject products into furnaces, electric arc furnaces, converters, or molten iron furnaces, even in rotary cement kilns (although not strictly metallurgical in this respect). In principle, any type of slurry can be used and metal-containing and mineral-containing slurries can be used, but in this respect, when the metal-containing slurry is used, the alloys in the metallurgical process comply with the required treatment, and when the mineral-containing slurry is used. Consideration should be given to whether the resulting amount of slack does not adversely affect the profitability of the steelmaking process. In the simplest case it is therefore possible to treat the fines in coal slurry, ie in the form of washing. However, these coal slurries only have low calorie values (because they show a high percentage of styryl mineral waste that only increases the amount of slag in the metallurgical process but do not contribute to the foaming of the slag).

As a result, an energy rich slurry is preferably used in an oil-containing rolling mill scale slurry, a clay slurry containing coal or coal dust, or a clay slurry containing coke dust, or a waste slurry in petrochemical. The slurry as described above provides the necessary carbon, thereby simultaneously reducing the energy required in the subsequent pig farming process. In particular, as is well known in mill scale slurry, foreign matter is scattered, but such impurities do not play any role in the present invention. This is because the foreign matter is separated from the slurry during the grinding process and after the thoroughly mixed components have been sifted away. This also applies to lumps or masses that can sometimes occur during mixing.

It is appropriate to use slurries resulting from wet extraction of ore reducing stations. In the case of dry extraction, it is appropriate to mix these powders unless they have already formed. Also suitable are slurries from smelters from blast furnaces, blast furnaces, electric arc furnaces, converters, sinter plants, and surface treatment facilities for grinding and polishing metals. The corresponding dust in the dry dust extract can be mixed into the powder as long as it does not form a powder.

In other words, the additive may include enough lime for the lime requirement of the furnace by adding free lime, a material exhibiting CaO. The amount of slurry required to form the reaction product according to the invention is thus increased beyond the actual requirements and additional fly ash is added. Free quicklime from fly ash reacts with the residual water in the slurry to form calcium hydroxide Ca (OH) ₂ , whereby heat is released. Limestone facilitates the subsequent metallurgical process and the free heat makes the combined product brittle.

Fly ash from the flue gas in the electric filter behind the power plant boilers is preferred when burning low sulfur fossil fuels. And this mainly includes Atan from the Rhine. However, fly ash that accumulates during fuel processing according to the dry addition process is suitable if limestone was added to the fuel to solidify sulfur prior to combustion. Materials called DAP circuits are available.

It is also possible to use dust or sand in the furnace top gas. They accumulate when the gas is cleaned in the furnace flue. All of these additionally contain residues of unconverted carbon and limestone as well as iron and iron oxides.

In the first step of the process, the flow of the slag is mixed in the later metallurgical process by mixing with finely divided quicklime or dolomite during the processing of heavy metal-containing dusts (including those produced during steel polishing in addition to those already mentioned). Is increased. Heavy metal-containing slurry processing also includes the polishing slurry used in the first step of the process in addition to those already mentioned. By preferably using finely divided fly ash, the non-additive slurry is usually dried in one step, thereby facilitating handling. The amount of quicklime in fly ash or slag in the ladle furnace helps the dry quicklime react with the slurry's moisture to help dry it, and much of the intrinsic moisture in the slurry is evaporated. Therefore, the lime addition which is advantageous for the later metallurgical process is not affected.

Another waste useful in the present invention consists of other forms of aluminum. The addition of aluminum is known to be useful for deoxidation and fluxing of slack. Some forms of aluminium can invade the inner wall of metallurgical vessels and others are expensive. Aluminum oxide or metal aluminum, for example oily wet abrasives, which are discarded according to the invention may be included. Such aluminum may also be present in the fly ash. If aluminum is present and the mass has other suitable components, such as high iron content, the mass is useful in the cement industry.

In the second step, a sieve is obtained to obtain a uniform particle composition band having a diameter of 6 mm or less. At the same time the foreign matter exposed in the first stage is obtained by so-called rolling, in more detail mill rolling slurry. These debris and large lumps can be polished if applicable and reinserted into the process cycle at appropriate points.

In the third step method, the finely divided finely divided sieves containing carbon-containing dust and limestone-containing masses are mixed thoroughly with them. This last step contributes substantially to low density until it can be flushed or injected under air or other gas pressure.

In the case of added carbonaceous dust, it is preferable to use attan coke dust or petroleum coke or anthracite or lead, or mixtures thereof, which come from slightly or low volatile coal, each of which has a grain size less than 1 mm in diameter. The addition of carbon is known to promote foaming of the slag in subsequent metallurgical processes. For example, in the case of metal-containing slurries in surface finishes, such as abrasive slurries, or in the case of mill scale slurries, with waste containing organic debris, for example oil, less carbon dust is originally of this kind. It will be needed rather than for slurries in wet cleaning of gases in molten metal, for example, which do not result in organic mixtures.

The addition of carbonaceous dust alone may not be sufficient to lower the density in that the product can be injected into the air. Instead, a carrier may be present to further reduce the density to which a mixture consisting of metal containing dust, calcium, carbon may be added. Spherical limestone-containing masses from the operation of boiler feed water in steam power plants operating steam turbines have been found to be suitable for this purpose. These masses are small, light and stable spheres with an average diameter of 1-2 mm, are extremely resistant to compression and abrasion and have a grain size in the range of 0.5 to 6 mm. These spheres result from the removal of calcium and iron from boiler feed water suitable for steam driven turbines. In the center of the sphere is a small quartz grain that accumulates lime and monocrystalline iron from boiler feedwater. These spheres are beige in color, have a smooth surface and exhibit high pressure strength. Usually they are processed into chunks.

In the case of the present invention, the sphere is preferably suitable as a carrier for mixing which constitutes heavy metal particles, lime and carbon. Coupling with the carrier is ensured by electrostatic forces as well as moisture from water processing. The content of silicon, lime and iron is helpful for subsequent metallurgical processes.

In another form, the present invention provides an air injectable feedstock that is used as an additive to molten metal in an electric arc furnace. This material includes reaction products of waste particulate material containing heavy metal elements and oily mill scales. The material is also in the form of a block having a particle size from about 0 mm to about 6 mm.

Air-injectable feedstocks used as additives to molten metals in electric arc furnaces include reaction products of waste particulate material containing heavy metal elements and directly reduced iron fines. This feed is in the form of agglomerates having a particle size from about 0 mm to about 6 mm.

One of these feedstocks comprises a carbon source in particulate form;

One of these feedstocks is quicklime present and participates in the reaction.

Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings so that the present invention may be well understood.

Claims (22)

In the waste disposal method containing heavy metals: The method comprises mixing a waste, a relatively low density particulate material containing an oxidizing material, and water to cause an exothermic reaction to form a relatively dry mass; Sifting the mass into sieves having a size ranging from about 0 mm to about 6 mm; And injecting the separated mass into air into a metallurgical vessel containing molten metal under a decrease in air pressure. The method of claim 1, wherein the oxidizing material is quicklime. The method of claim 1, wherein the oxidizing material is iron directly reduced. The waste treatment method according to claim 1, 2 or 3, wherein the waste is dust obtained from an electric arc furnace. The method for treating wastes containing heavy metals according to claim 1, 2 or 3, wherein an aluminum source is present. In the later method for producing fine powder for metallurgy process: The fines come from the iron ore at least partially reduced in a dusty form, Mixing the fine powder and the fine grain carrier having a low density to produce a brittle product, and sifting the product to provide a grain size material between 0 mm and 6 mm suitable for injection in a metallurgical process. Fine powder manufacturing method for metallurgy process. The method of claim 6, wherein the used carrier is a carbon-containing material. 8. The method for producing metal powder for metallurgical process according to claim 6 or 7, wherein sufficient water is added to improve adhesion between the fine powder and the carrier. The method for preparing fine powder for metallurgical process according to claim 6, 7, or 8, wherein a slurry of water and carbon is added to the mixed product and mixed thoroughly. 10. The method of claim 9, wherein the excess slurry containing free lime is used in finely divided form together with the dusty material. The method of claim 9 or 10, wherein the slurry is an oil-containing rolling mill scale slurry, or a process for preparing metal powder for metallurgical process, characterized in that it comes from the processing of steel or metal suitable for alloying steel by oil-containing cutting fluid. 10. The method of claim 9, wherein the slurry is produced by treating the furnace gas with water. 12. The method of claim 10, wherein the slurry contains fly ash resulting from the combustion of fossil fuel containing calcium. 15. The method of claim 13, wherein the slurry contains fly ash from the cleaning of flue gas by limestone or calcium hydroxide in a power plant boiler. 15. The method of claim 14, wherein the slurry contains furnace flue flue. 16. The method according to any one of claims 9 to 15, wherein the injectable microfragments are sifted out from the reaction or binding product and the finely divided filaments for reprocessing. For air injectable feedstocks used as additives to molten metal in electric arc furnaces: Wherein said material comprises a reaction product of waste particulate material containing a heavy metal element and an oily mill scale and is in a bulk form having a particulate size from about 0 mm to about 6 mm. For air injectable feedstocks used as additives to molten metal in electric arc furnaces: The material comprises a reaction product of waste particulate material containing heavy metal elements and directly reduced iron fines, and the feed material is an air injectable feed material characterized in that it is in the form of a mass having a particle size of about 0 mm to about 6 mm. . 19. The injectable feedstock of claim 17 or 18 comprising a carbon source in particulate form. 20. The injectable feedstock of claim 19 wherein the content of carbon source is sufficient to reduce the content of iron oxide in the feedstock. 21. The air injectable feed according to any one of claims 17 to 20, wherein quicklime is present and participated in the reaction. 22. An injectable feed material according to any one of claims 17 to 21 containing aluminum.