LT3886B - Method for agglomerating materials having ferrous oxide - Google Patents

Abstract

An agglomerated mix, that contains ferrous compounds and a solid fuel, is agglomerated in an agglomeration apparatus. The quantity of gas being eliminated is diminished and the agglomerate quality increased in case when a part of the used gas is concentrated by oxygen up to the maximum of 24 percent of the concentration after mixing the oxygen concentrated gas, and is returned as a circulating gas. The only eliminated quantity of the used gas amounts to the gas quantity that has been produced during the agglomeration process also mixed in a oxygen concentrated gas and the total quantity of air being absorbed through non-hermetic butt joints, subtracting the sum of the oxygen amount that has been consumed during this operation.

Description

The invention relates to a method for agglomerating iron oxide materials using an agglomeration machine; in addition, a solid fuel agglomerated mixture is fed to an agglomeration machine, where the surface of the mixture is ignited by exposure to oxygen containing gas; some of the gas from the combustion process is enriched in oxygen-containing gas and sent back to the machine, thereby playing the role of secondary circulating oxygen-containing gas, while the remainder of the spent gas is disposed of as process waste.

Iron oxide materials, such as iron ore or iron ore concentrates, are agglomerated using agglomeration machines. The agglomeration mixture, consisting of iron ore, ballast, solid fuel and additives, is fed to the agglomeration machine. Here he is inflamed with a wound. Air is drawn in through the sintered mixture and the combustion front descends in the sintered mixture. The combustion gas from the tanks above the agglomeration machine is sucked into a gas collector, cleaned and vented to the atmosphere. The agglomeration process is driven by the heat transfer of hot gas to the cold solid phase. The amount of heat transferred depends on the amount of fuel and oxygen. The aforementioned heat transfer is realized by using a large amount of air and gas produced in the same combustion process. Not all of the oxygen in the air is used, and the resulting gas includes water evaporated from the agglomeration blend, CO ₂ blend combustion product, CO partial oxidation product, and other gases.

From IPA 52 116 703, an agglomeration process is known, characterized in that the spent gas is not released into the atmosphere. According to the present invention, the gas flowing into the mixture layer is mixed with oxygen, all or part of the spent gas is directed to a blast furnace, and the remaining gas is directed to a circulating circuit. Where all gas is blown into a blast furnace, the oxygen concentration in the gas must exceed 30% and the gas inlet shall be approximately 650 nm / l of agglomerate. As the oxygen concentration increases, the amount of gas consumed decreases. If only part of the spent gas is directed to the blast furnace and the remainder enters the circulation circuit, the maximum amount of gas aspirated containing 17% oxygen is also 650 nm ³ / t agglomerate, most preferably 500 nm ³ / t. As the oxygen concentration increases, the amount of gas aspirated is reduced. The use of these quantities of gas reduces the quality of agglomeration. In addition, blast furnace connection is difficult and oxygen consumption is high.

The object of the invention is to minimize the amount of gas used and to obtain high quality agglomerates in the most economical way possible.

According to the invention, this object is achieved by a method different from the one described above, which is only the amount of spent gas which corresponds to the sum of the gases enriched during agglomeration, the enriched oxygen gas and the air intake through the leakage minus this amount of combustion oxygen. and the residual gas being diverted back, after the mixture has been charged, the amount of oxygen enriched gas is added to the circulating gas such that the gas mixture has a maximum oxygen concentration of 24%.

Oxygenated gas (LPG) is a gas with a higher oxygen concentration than the used gas. Examples of such gases are oxygenated air or technically pure oxygen. The gases emitted during agglomeration are predominantly CO ₂ and CO - products from the combustion of carbon, water vapor from the evaporation of water and SO _X - products from the combustion of sulfur compounds.

Suction air leakage Mix, for example, at the beginning and end of the agglomeration zone. In addition, air may be mixed at the agglomeration machine pallet sealing gaskets and sealing beams. Part of the oxygen is consumed during the agglomeration and oxidation processes accompanying the agglomeration. Only the amount of spent gas that corresponds to the amount of gas released in the process is removed. The rest of the spent gas is diverted back. This gas plays the role of a circulating gas. The amount of gas injected, consisting of circulating gas mixed with oxygen enriched gas, is 950-1200 nm ³ / t of agglomerate. The corresponding oxygen content is 30130 nm / t agglomerate. As the concentration of O2 in the oxygen-enriched gas decreases, the amount of spent gas removed and the amount of oxygen-enriched gas mixed increases, with minimal use of technically pure oxygen and maximum use of air. When using air, a large amount of nitrogen is added. Nitrogen in the gas circulating must be compensated by an appropriate amount of exhaust gas. The minimum oxygen concentration in the agglomerated enriched gas entering the agglomeration machine is only about 8%. The amount of spent gas discharged depends on the agglomeration conditions and may reach 600 nm ³ / t of agglomerate. Gas consumption is minimized by mixing technically pure oxygen, reducing the air intake through leaks, and condensing and removing water vapor with dissolved CO2. The upper part of the agglomeration machine has a hood for collecting the circulating gas. At the beginning of the work, air is blown for ignition and agglomeration of the burner. According to the criteria mentioned above, part of the used gas is disposed of and the rest is used as circulating gas.

An advantage of the invention is the small amount of exhaust gas. In this way, the purification of the gas is reduced and the agglomerate prepared has good properties.

Embodiment of the invention, characterized in that the circulating gas is enriched with oxygen up to a concentration of 16-22%. In this case, a higher agglomeration efficiency is achieved compared to the non-oxygen enrichment process.

Embodiment of the invention, characterized in that the circulating gas is enriched with oxygen up to a concentration of 18-21% The efficiency of the agglomeration process is significantly increased compared to the Conventional.

Embodiment of the invention, characterized in that the circulating gas is enriched with oxygen up to 10-16%. In this case, the quality of the agglomeration is good enough and the efficiency of the process remains the same. In addition, as oxygen is eliminated, oxygen consumption is reduced.

An embodiment of the invention wherein the pressure of the circulating gas in the enclosure is close to atmospheric pressure and said pressure is maintained by controlling the amount of exhaust gas. We call near atmospheric pressure the pressure whose value is in the range between the minimum and the gauge pressure. In this way, atmospheric air is not leaking or leaking, and the amount of gas discharged meets the above criteria.

An advantageous embodiment of the invention, characterized in that the amount of solid fuel admixed with the agglomerated mixture is reduced by taking into account the amount of heat emitted by the combustible CO gas in the circulating gas, although the circulating gas contains a significant excess of CO concentrations can be up to a dozen percent. Thus, the amount of heat released by the combustion of CO __ allows to reduce the amount of coke burned. This saves up to 20% on coke. In addition, since coke is the main source of sulfur, the amount of SO _X in the waste gas is reduced.

Embodiment of the invention, characterized in that the amount of exhaust gas is reduced by condensation of H ₂ O and / or leaching of CO ₂ and / or sulfur binding. The water is condensed and the CO _{2 is} leached directly from the exhaust gas. The sulfur is bound by the addition of CaO or Ca (OH) ₂ to the agglomerated mixture or charge. This reduces the amount of gas removed.

An embodiment of the present invention wherein the circulating gas is heated to prevent the temperature from falling below the dew point of H ₂ SO ₄ . In this case, the gas temperature does not fall below the dew point of H ₂ SO ₄ and the equipment is protected against corrosion.

Embodiment of the invention, characterized in that by condensing water from the exhaust gas, the dew point is initially reached by injecting water, and then the gas is cooled indirectly by condensation of water vapor.

Embodiment of the invention, characterized in that the circulating gas is purified from the ash and the ash obtained is recycled to the agglomeration mixture. The gas is cleaned by mechanical dust collection devices such as cyclones and multiclones. It is possible to purify all spent gas, only the recirculating gas or the recirculating and recirculating gas separately. This protects the pipelines and facilitates the cleaning of exhaust gas.

Embodiment of the invention, characterized in that the circulating gas at the side walls of the gas hood plays the role of a gas baffle, between the edges of the gas hood, the upper hood is provided with air tanks to provide excess pressure over the charge. for these reasons, a small amount of circulating gas penetrates through the gap between the charge surface and the bottom edge of the gas shield sidewall. This prevents air leakage through the side walls.

Embodiment of the invention, characterized in that the spent gas is purified in a circulating vortex bed with a solid sorbent at a temperature below 150 ° C, preferably 80-60 ° C, in order to remove the harmful gases and solids. The sorbent may be dolomite of CaO, Ca (OH) ₂ , CaCO ₃ . The circulating vortex system consists of a vortex reactor, a separator for the separation of solids from the slurry in the reactor, i.e., a recirculating cyclone with a separation line for solids removal. The temperature of the gas and sorbent in the reactor is controlled by adding water to the reactor. The gas flow rate in the reactor vortex layer is 1-10 m / s, preferably 2-5 m / s. The density of the suspension in the reactor is 0.11100 kg / m ³ , preferably 1-5 kg / m ³ . The average diameter of the sorbent particles is 1-100 µm, preferably

5-20 μπι. The amount of sorbent circulating per hour should be five times the amount of sorbent in the reactor shaft, preferably 30-100 times. The temperature of the cooled mixture should be 5-30 ° C above the dew point of the water. The partial water vapor pressure in the reactor is 15-50% by volume of water vapor, preferably 25-40%. The sorbent can be fed to the reactor in the form of a solid or an aqueous suspension. In the reactor, sorption occurs when the atLT 3886 B is at rest, the layer is composed of solid particles of 100-500 μιη size, and the charged sorbent particles are smaller. The circulating vortex layer is different from the classic vortex layer. In the classic case, there is a clear boundary between the dense phase and the gas phase, i.e., the observed density jump. In the case of a circulating vortex, there is no sudden leap in density in the dispersion layer, and the solids concentration in the reactor decreases steadily as the downstream passes. The gas-solid suspension is discharged from the top of the reactor. The working range of the device is expressed in Froide and Archimedes numbers:

0.1 <3/4 · Fr ² · ——— <10

Pk - pg or

0.01 <Ar <100.

Also, dkg (pk - pg) pg - v ²

Fr = š ^d k where:

u - gas velocity, m / s;

Ar - number of Archimedes;

Fr

Froide number;

pg - density of gas, kg / m ³ ;

p _k - particle density, kg / m ³ ;

d _k - diameter of the spherical particles, m;

v is the kinematic viscosity, m / s;

g is the constant of gravity.

The circulating vortex layer can treat all spent gas, only the recirculating gas, only the recycle gas, or both recirculating and recirculating gas separately. In the circulating gas layer, the gas is decontaminated with a large amount of SO _X and dust. After removal from the vortex layer, the sorbent is returned to the agglomeration mixture. Part of the sorbent is evaporated during agglomeration, but most is bound to the agglomerate and is removed from the cycle. Vortex sorption sorption allows for the avoidance of enrichment of circulating gas with SO _X gas and purification of the gases removed from these sulfur compounds. In cases where very good dust extraction is required, the electrostatic gas cleaning method may be used.

A process for carrying out the invention, characterized in that the gas is removed from the cavities located above the start of the agglomeration strip. It has been found that the concentration of various harmful substances in the off-gas discharged at the beginning of the belt is significantly lower than the concentration of these substances in the remote areas of the belt. This difference can be explained by the presence of moisture at the beginning of the web, especially in the lower layers of the Charge, which effectively traps harmful substances during adsorption, adsorption and filtration processes. In this way, accumulated noxious wood EN 3886 B enters the recirculating gas, which is returned to the charge only at later stages of the agglomeration process. Harmful substances may include gases such as SO ₂ , SO ₃ , HCl and HF, vapors such as non-ferrous metals or their compounds, or dust-like substances such as chlorides and fluorides. The local concentration of gaseous harmful substances at the beginning of the belt is less than the total concentration of harmful gases along the agglomeration belt. In case the resulting gas contains dioxins and furans, their concentration at the beginning of the band is insignificant. This gas decomposes when it enters the circulating gas flowing through the charge combustion front. In this way, the gas collected at the beginning of the agglomeration belt can be discharged directly to the atmosphere after purification from dust, or easily cleaned of noxious substances. The amount of gas collection cavities from which the waste gas is discharged or the area of the agglomeration strip where the gas is collected shall be selected in such a way as to collect the required quantity of waste gas. The area of the agglomeration belt where the waste gas is collected is 10-50% of the total length of the agglomeration belt. The first cavity of the gas accumulates gas with a higher dust content. This dust is removed by cyclones and multiclones. Fine dust is formed during agglomeration, usually during the sublimation of chlorides, such as alkali chlorides, from the agglomeration mixture to the combustion zone. This fine dust is separated in the charge using a filtering effect on the lower wet layers of the charge. Dust from the circulating gas during recirculation settles in the agglomerated mixture or on porous structures. In this way, dust is removed from the cycle and the cleaning of the circulating gas from the dust is greatly facilitated. The enrichment of circulating gases with SO ₂ must be avoided. SO _{2 is} removed by calcium compounds, such as Ca (OH) ₂ or CaO, which are present in the charge. SO ₂ can also be disposed of in other locations.

other than that to which the process of the present invention is returned, a portion of the agglomeration belt, a caulking gas, is sprayed with a solution containing calcium and / or magnesium hydroxides and / or oxides. Ca (OH) ₂ solutions are particularly suitable for this purpose. SO ₂ is bound in a charge. the length of the part of the loading strip that is sprayed with sulfur-binding agents and the amount of material injected are empirically selected depending on the operating conditions of the device. In this way it is possible to remove SO ₂ from the circulating gas easily and economically. Binders may also be secondary products that are disposed of.

A method of carrying out the invention, characterized in that a layer of raster moistened with a solution of calcium and / or magnesium hydroxide and / or oxide is applied to the agglomerated layer. This also effectively removes the SO ₂ from the circulating gas.

Embodiment of the invention, characterized in that the evolved gas is heated. The temperature of the accumulated gas in the front of the agglomeration machine is 50-80 ° C. In the vents, the gas is heated to a temperature where condensation is avoided and, at the same time, corrosion of the unit.

Embodiment of the invention, characterized in that the spent gas from the first gas collection cavity or the first section of this cavity, together with the air sucked in by leaks, is mixed into the circulating gas and the gas is removed from the other gas collection cavities. In this way, the air sucked in by leaks is used to enrich the circulating gas with oxygen.

A method of carrying out the invention, characterized in that the spent gas is removed from the cavities adjacent to the agglomeration belt; these cavities contain many harmful substances that are removed with the gas. Therefore, gases with high concentrations of harmful substances are eliminated and the volume of gas is not high. In this way, non-ferrous metals such as zinc and lead, or their compounds, can be effectively removed from the waste gas. This method is applicable when the agglomerated mixture contains waste from the metallurgical industry which is rich in non-ferrous metals such as converter dust, agglomeration machine dust and the like.

Embodiment of the invention, characterized in that part of the circulating gas is removed from the gas collecting cavities located above the agglomeration strip. These cavities contain high levels of harmful substances. The harmful substances are partially removed from the circulating gas stream and the purified gas is returned to the circulating stream. Thus, hazardous materials can be removed from relatively small volumes of gas used.

The invention is explained in detail by way of examples.

A 400 m agglomeration machine was used. Technical characteristics of the machine:

Agglomeration productivity 578, p hr / hr Oxygen consumption 56, 9 3 nm / t agglomerate Water vapor yield 99, 7 nm ³ / t agglomerate CO ₂ yield 79, 3 nm ³ / t agglomerate CO content in the exhaust gas 1 o o.

In the table below, sample no. 0 is a typical air agglomeration process, and Examples 1-6 are an agglomeration process according to the invention.

Examples 1-3 illustrate the influence of the oxygen content of the agglomerating gas (i.e., the oxygen-enriched circulating gas) on the agglomeration process.

Example 1 illustrates the effect of a reduction in air intake on the sintering process (cf. Example 2).

Example 4 illustrates the effect of water condensation and leaching of CO ₂ from the flue gas on the agglomeration process (cf. Example 4).

Example ₂ illustrates the influence of a negligible amount of O ₂ gas on the enrichment gas during the agglomeration process (cf. Example 2).

Examples 7-9 below illustrate the effect of the intake air (i.e., oxygen-rich gases) on the agglomeration process. Gas quantities are given in nm ³ / t agglomerate units.

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An example 7th 8th 9th Amount of gas aspirated 1165 1165 1165 O ₂ % gas in the intake gas 12th 14th 16th Extra O ₂ - - - Amount of air mixed 385.45 474.48 600 Amount of gas removed 1488.53 1489.4 1488.5 Amount of gas accumulated 610.51 700.12 825.03 % Of total 40.14 46.03 54.24 Composition of exhaust gas: O ₂ 7.55 9, 19 10.86 H ₂ O 16, 38 14.14 12.0 CO ₂ 12.82 11.07 9.4 n ₂ 63.25 64, 60 66.76 CO 1.0 1.0 1.0 Suction gas composition: CO ₂ 8.6 6, 65 4.6 H ₂ O 11.0 8.5 5.8 n ₂ 68, 5 70, 46 73, 1 CO 0.7 0, 6 0.5

The following examples show the following patterns:

1. If the oxygen content of the agglomerating gas does not change, then

(a) The amount of exhaust gas increases with decreasing oxygen content in the saturated oxygen gas

(b) The amount of O ₂ added per tonne of agglomerate increases with the concentration of O ₂ in the enriched oxygen gas.

2. The amount of O ₂ added per tonne of agglomerate shall increase as the concentration of O ₂ increases in the concentration of O ₂ added and O ₂ in the sintered gas, provided that the volume of gas discharged remains constant.

3. If the oxygen concentration in the oxygen enriched gas does not change, the amount of gas discharged and the amount of O ₂ gas per tonne of agglomerate shall decrease as the concentration of oxygen in the sintered gas decreases.

4. The addition of the same amount of oxyhydrogen increases the amount of exhaust gas as the O ₂ content of the agglomerating gas increases and the O ₂ content of the enriched oxygen gas decreases.

The operating modes corresponding to Examples 10 and 11 below are analogous to Examples 3 and 7.

example

The amount of gas discharged is 304.7 nm / t of agglomerate. This gas is discharged at the part of the agglomeration belt which coincides with the edge of the suction zone and which is 12% of the total length of the belt. The waste gas contains 7.1% of total SO ₂ gas and 2.6% of all chlorides.

example v 3 _v

The amount of gas removed is 650.51 nm / t of agglomerate. This gas is discharged at the part of the agglomeration belt which coincides with the edge of the suction zone and which is 36% of the total length of the belt. The waste gas contains 14.2% of all SO ₂ gas and 9.1% of all chlorides.

The figure shows the flow and chloride distribution of S0 ₂ in one of the above-mentioned operating modes. Each point is represented by the percentage of harmful substances in the gas collection cavities of the sintering machine. The total amount of harmful gas in the used gas is 100%.

Claims (19)

DEFINITION OF INVENTION 1. A method of agglomerating iron oxide-containing materials by means of a sintering machine, wherein the solid fuel agglomeration is fed to an agglomeration machine, the agglomeration mixture is ignited and the gas containing oxygen is supplied through the agglomeration mixture, some of the spent gas is enriched in oxygen by the addition of oxygen enriched gas and returned, ie it plays the role of circulating gas, while the other part of the used gas is disposed of as process waste, which differs from the amount of spent gas the amount of agglomeration, the amount of oxygenated gas and the amount of air intake, less the amount of oxygen consumed during combustion, and using the remainder of the used gas as circulating gas, which is then mixed with oxygenated gas prior to loading the agglomeration mixture. two increases the oxygen concentration to a maximum of 24%. 2. The process of claim 1, wherein the circulating gas is oxygenated to a concentration of 16 to 22%. 3. A process according to claim 2, wherein the circulating gas is oxygenated to a concentration of 18 to 21%. 4. The process of claim 1, wherein the circulating gas is oxygenated to a concentration of 10 to 16%. 5. The method of claims 1-4, wherein the gas collection chamber located above the agglomerated mixture for collecting the recirculating gas is a pressure close to atmospheric pressure and maintains a constant pressure value by controlling the amount of waste gas discharged. quantity. 6. A process according to claims 1-5, wherein the solid fuel is reduced in the agglomerated mixture, including the amount of heat of combustion of carbon monoxide gas in the circulating gas. 7. A process according to claims 1-6, characterized in that the amount of gas removed is reduced by condensation of water and / or leaching of carbon dioxide and / or sulfur. 8. A process according to claims 1-8, wherein heating the circulating gas avoids a drop in temperature below the dew point of the sulfuric acid. 9. A process according to claim 7, wherein the temperature of the water vapor condensation is raised above the dew point at the beginning of the water vapor condensation process, after which the temperature automatically decreases during condensation. 10. A process according to claims 1-9, characterized in that, before returning the circulating gas back to the cycle, it is purged of dust and the separated dust is directed to the agglomerated mixture. 11. The method of claims 1-10, wherein the gas circulating on the sides of the gas collection chamber acts as a gas barrier. 12. A process according to claims 1-11, wherein the harmful gases and solids are removed from the used gas in the circulating vortex layer by a solid sorbent at temperatures below 150 ° C, preferably 80-60 ° C. 13. The method of claims 1-12, wherein the spent gas is removed from the gas collection cavities located at the front of the sintering machine. 14. A process according to claim 13, wherein a significant portion of the agglomeration belt, which is flushed by a stream of recirculating gas, is sprayed with a solution of calcium and / or magnesium hydroxide and / or oxides. 15. A process according to claim 13, wherein the agglomerating mixture is coated with a raster layer moistened with a solution of calcium and / or magnesium hydroxide and / or oxides moistened. 16. The method of claims 13-15, wherein the exhaust gas is heated. 17. A process according to claims 13-16, wherein the spent gas at the beginning of the agglomeration strip, which also contains air leaked, is returned from the first gas collection chamber or first compartment as circulating gas and the gas collected in the other cavities is removed. 18. A process as claimed in any of claims 1 to 12, wherein the spent gas is removed from the cavities of the agglomeration belt containing a high concentration of harmful substances, and the gas thus collected is purified from said harmful substances. 19. The method of claims 1-17, wherein a portion of the circulating gas is removed from the agglomeration belt gas collection cavities having a high concentration of the harmful substances, the harmful substances are removed from said portion of the circulating gas, and said purified portion is returned to the total circulating gas stream. .