CN106811597A - Method for producing cold-bonded carbon-containing pellets for blast furnace by using lime kiln waste gas - Google Patents

Abstract

The invention provides a method for producing cold-consolidated carbon-containing pellets for blast furnaces by using waste gas from a lime kiln. Carbon-containing materials, iron-containing materials, quicklime, and binders are uniformly mixed, and the mixture is added to the mixture according to the total weight of the mixture. 10% to 20% water, fully digested after stacking for 1 to 3 hours; pelletize the digested mixture with discs or roll balls to obtain carbon-containing pellets; Transport it to the curing reaction chamber, and pass the lime kiln exhaust gas into the bottom of the raw pellet curing reaction chamber. The temperature of the lime kiln exhaust gas is 100-150 °C, and the curing time is more than 24 hours, and the cold-consolidated carbon-containing pellets for blast furnaces are obtained. The method for producing cold-consolidated carbon-containing pellets by using lime kiln exhaust gas in the present invention can not only produce cold-consolidated carbon-containing pellets with high high-temperature strength, but also can significantly reduce the _CO2 emission in lime kiln exhaust gas, and the pellets High temperature strength, good thermal stability.

Description

A method for producing cold-consolidated carbon-containing pellets for blast furnaces using lime kiln waste gas

technical field

The invention belongs to the fields of metallurgy environmental protection and iron making and agglomeration, and in particular relates to a production method of cold-solidified carbon-containing pellets.

Background technique

Lime plants supporting iron and steel plants discharge a large amount of waste gas into the atmosphere every year. Lime kiln waste gas is the waste gas with high CO ₂ content produced during the process of calcining limestone in the lime kiln industry to produce quicklime. The waste gas generated in the above process is generally not used. The _CO2 content in the kiln exhaust gas is generally between 25% and 35%, up to 40%, which is higher than that of other industrial furnace exhaust gases and contains a certain amount of waste heat. If _CO2 is directly discharged into the atmosphere, it will cause energy waste And air pollution, the dust in the flue gas will also cause great pollution to the surrounding environment. The emission of CO ₂ and dust in the process of iron and steel metallurgy has attracted worldwide attention, and low-carbon and environmentally friendly ironmaking is the primary goal of ironworkers.

Cold consolidation of carbon-containing pellets is made by mixing iron-containing raw materials (mainly iron ore powder and iron-containing dust), carbon-containing raw materials (mainly coal powder and C-containing dust) and binders in proportion and then adopting double-roller briquetting A kind of iron-making raw material produced by making pellets with disks and then curing. The production process of cold-solidified carbon-containing pellets avoids the traditional high-temperature sintering process, greatly shortens the process flow, and has strong reducibility, It has the advantages of low production cost, environmental protection and energy saving. Cold-consolidated carbon-containing pellets are the main iron-making raw materials for direct reduction and smelting reduction processes, but due to their low high-temperature strength and poor thermal stability, it is difficult to meet the needs of blast furnace iron-making.

The literature "Preliminary Practice of Producing Carbonated Pellets" Author: Tang Guangwu "Sichuan Metallurgy" in 1979, introduced the process of using hot blast stove exhaust gas to maintain CaO-containing pellets and produce carbonated pellets for blast furnaces, but due to hot blast stove exhaust gas The content of CO ₂ in carbon dioxide is generally low, and the strength of green pellets increases slowly, resulting in long curing period of carbonated pellets and low cold strength of pellets.

"Method for Cold Consolidation Pellets of Mineral Powder Using Water Glass as a Binder" (Application No.: 201210141420.2) discloses a method for producing carbon-containing pellets for blast furnaces using water glass as a binder. Water glass is added to the mineral powder modified by strong alkali, and the finished pellets are obtained after mixing, grinding, briquetting and drying.

"Cement mixture is used as binder to consolidate fine mineral powder to make carbon-containing pellets" (application number: 200710146728.5) has announced a method for producing carbon-containing pellets for blast furnaces using cement as a binder. The method combines mineral powder, carbon Powder and 10% cement are uniformly mixed, pelletized and cured for 3 days, and can be made into carbon-containing pellets for blast furnaces.

The disadvantage of the above-mentioned patents is that although the strength of the carbon-containing pellets produced by the above two methods is relatively high, the bonding properties of the cement and the water-wave glass will quickly fail when the water glass and cement are heated above 200°C, and the pellets The strength drops rapidly, and the high temperature strength is low.

"Preparation Method of Iron Concentrate Coal Powder Hot-pressed Agglomerates" (application number 200710010097.4) announced the preparation method of hot-pressed carbon-containing pellets, although the cold strength and high-temperature strength of the pellets produced by this method are in line with blast furnace ironmaking production requirements, but the production process of hot-pressed pellets needs to preheat the mixture in advance, and it needs to be completed at a high temperature of 350-500°C for 20-30 minutes during the process of rolling the balls. The production efficiency is low, and the hot-pressing process It is easy to ignite the coal powder in the mixture, which has poor safety, and the coal powder used must be coking coal with strong cohesiveness and scarce resources.

In order to overcome the deficiencies in the above patents and documents, the present invention passes the lime kiln waste gas into the carbon-containing pellet green pellet curing chamber, and utilizes the high-concentration _CO2 gas in the lime kiln waste gas to chemically react with the CaO in the pellets to make the pellets CaCO ₃ bridges are formed between the CaO particles in the pellets, so that the pellets are consolidated, and the excess water in the pellets is quickly taken away by using the waste heat in the exhaust gas, so that the curing time of the pellets is shortened.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned problems and disadvantages and provide a method for producing cold-consolidated carbon-containing pellets using lime kiln exhaust gas, which can produce cold-consolidated carbon-containing pellets with high high-temperature strength and can significantly reduce the cost of lime kiln. Method for _CO2 emissions in exhaust gas.

The purpose of the invention is achieved in this way:

The present invention aims to provide a cold-consolidated carbon-containing pellet production method capable of producing cold strength and high-temperature strength that meet the requirements of blast furnace ironmaking, while avoiding the traditional sintering process and reducing _CO2 emissions from lime kilns in iron and steel plants. The present invention The high content of CO ₂ in the lime kiln waste gas reacts with the CaO in the pellets to form a CaCO ₃ skeleton, and the residual heat in the waste gas is used to remove excess water in the pellets to achieve the purpose of rapid consolidation of the pellets. Since the decomposition temperature of CaCO ₃ is close to 900°C, the cold-consolidated carbon-containing pellets produced by this method have high high-temperature strength. When the temperature exceeds 900°C, due to the C powder inside the pellets and the The iron substance undergoes a reduction reaction, and a metal iron skeleton is formed inside the pellets, so that the pellets still maintain their strength after 900°C until the pellets soften and melt, completely overcoming the carbon-containing pellets caused by the cold-solidification of the blast furnace smelting carbon-containing pellets. The high-temperature strength is low, and the pellets burst before the metal iron skeleton is formed, resulting in the disadvantages of blast furnace suspension and hearth freezing.

A method for producing cold-consolidated carbon-containing pellets for blast furnaces using lime kiln exhaust gas,

(1) The carbon-containing materials, iron-containing materials, quicklime, and binders finer than 200 mesh are respectively 5-15% by weight, 50%-70%: 15%-25%: 5%-10% mix evenly;

(2) Add water accounting for 10% to 20% of the total weight of the mixture to the mixture in (1), and fully digest it after stacking for 1 to 3 hours;

(3) Carrying out the disc pelletizing of the digested mixture or agglomerating the method of rolling balls to obtain carbon-containing pellets;

(4) Transport the raw balls to the curing reaction chamber, and pass the lime kiln waste gas into the bottom of the green ball curing reaction chamber. The temperature of the lime kiln waste gas is 100-150 ° C, and the curing time is more than 24 hours. The cold consolidation of the finished blast furnace is obtained. Carbon pellets.

The iron-containing material is one or more of iron ore powder, converter dust, electric furnace dust, sintering head ash and sintering return ore; the carbon-containing material is coal powder, blast furnace bag ash, blast furnace gravity ash and coking One or several kinds of dedusting ash; the binder is any one of bentonite and sodium carboxymethyl cellulose and the above two.

The beneficial effects of the present invention are:

(1) The cold consolidation agglomeration process is adopted, which avoids the traditional sintering process and can reduce _CO2 emissions;

(2) This process uses the high concentration of CO ₂ in the lime kiln waste gas to react with CaO in the pellets to form a CaCO ₃ skeleton to increase the strength of the pellets, which not only reduces the CO ₂ emissions in the waste gas in the lime kiln, but also shortens the curing time , with high social value and economic value;

(3) Rely on the residual heat of lime kiln exhaust gas to preheat the green pellets, so that the excess water in the pellets is taken away by the hot exhaust gas, so that the strength of the green pellets can be increased rapidly, and the green pellets cannot reach the strength due to the extrusion between the pellets. Broken, has a better effect of energy saving and emission reduction;

(4) Lime kiln exhaust gas contains a certain amount of lime dust, which has a light specific gravity and strong hygroscopicity, and can be adsorbed on the surface of carbon-containing green pellets to avoid sticking to each other during the maintenance of carbon-containing pellets;

(5) There is a certain proportion of C powder inside the pellets, which acts as a reducing agent and a heating agent inside the pellets, which can improve the reduction of the pellets and reduce the coke ratio;

(6) The cold-solidified carbon-containing pellets of the present invention rely _on the CaCO3 skeleton generated inside the pellets for consolidation. Because the CaCO3 decomposition temperature is high (the decomposition temperature is 898 ° C), the high _- temperature strength of the pellets is high, and the thermal stability is good. It overcomes the shortcomings of traditional cold-consolidated carbon-containing pellets, such as high cold strength and low high-temperature strength, which are easy to burst;

(7) The production of carbon-containing pellets by this method can recycle steel plant converter dust, dust such as blast furnace gas ash and sintering machine head dust, and reduce the cost of pelletizing;

(8) The dust contains a certain amount of alkali metal, and the alkali metal in the carbon-containing pellets can catalyze the coal powder in the pellets to improve the reducibility of the pellets.

detailed description

Below by embodiment the present invention will be further described.

Example 1

The cold-consolidated carbon-containing pellets for blast furnaces in the invention use iron ore powder, coal powder and quicklime in iron and steel plants as raw materials. Table 1 shows the raw material composition of cold-solidified carbon-containing pellets in Example 1 of the present invention.

Table 1 Raw material composition of cold-solidified carbon-containing pellets in Example 1 of the present invention (%)

Grind the mixed materials until the proportion of finer than 200 mesh accounts for more than 90%, and then mix them in proportion. See Table 2 for the batching scheme of cold-solidified carbon-containing pellets in Example 1 of the present invention.

Table 2 Batching scheme of cold-consolidated carbon-containing pellets in Example 1 of the present invention

Add water accounting for 15% of the total weight of the mixture to the mixture, mix the water and the mixture evenly, and fully digest after stacking for 2 hours. The mixture is put into a disc pelletizer for pelletizing to obtain carbon-containing pellets.

Transport the raw balls to the curing reaction chamber, feed the lime kiln waste gas to the bottom of the green ball curing reaction chamber, control the temperature of the lime kiln waste gas fed into the green ball curing chamber at 120°C, and keep the curing time for more than 24 hours to obtain the finished product blast furnace. Consolidated carbonaceous pellets.

The comparison between the strength after preheating of Example 1 of the present invention and the strength of other cold-consolidated carbon-containing pellets under a reducing atmosphere is shown in Table 3. It can be seen from Table 3 that the high-temperature strength of the carbon-containing pellets of the present invention is higher than that of traditional techniques such as water glass and cement. The pellets produced by the binder have been greatly improved. The reducibility comparison between the cold-solidified carbon-containing pellets and the pellets in Example 1 of the present invention is shown in Table 4. The reducibility has increased by about 4%, which can meet the needs of blast furnace ironmaking .

Table 3 Comparison of the strength of Example 1 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere (N/ball)

Table 4 Comparison of reducibility between cold-consolidated carbonaceous pellets and pellets in Example 1 of the present invention

Example 2

The cold-solidified carbon-containing pellets for blast furnaces in the invention use iron and steel plant dust and quicklime as raw materials. See Table 5 for the raw material composition of cold-solidified carbon-containing pellets in Example 2 of the present invention.

Table 5 Raw material composition of cold-solidified carbon-containing pellets in Example 2 of the present invention (%)

Grind the mixed materials until the proportion of finer than 200 mesh accounts for more than 90%, and then mix them in proportion. See Table 6 for the batching scheme of cold-solidified carbon-containing pellets in Example 2 of the present invention.

Table 6 Batching scheme of cold-consolidated carbon-containing pellets in Example 2 of the present invention

Add water accounting for 20% of the total weight of the mixture into the mixture, mix the water and the mixture evenly, and fully digest after stacking for 2 hours. Put the mixture into the double roller briquetting machine for agglomeration, and press it into pillow-shaped carbon-containing pellets.

Transport the green balls to the curing reaction chamber, feed the lime kiln waste gas to the bottom of the green ball curing reaction chamber, control the temperature of the lime kiln waste gas fed into the green ball curing chamber at 120°C, and keep the curing time for more than 32 hours to obtain the finished product blast furnace. Consolidated carbonaceous pellets. See Table 7 for the comparison between the strength after preheating in Example 2 of the present invention and other cold-consolidated carbon-containing pellets under a reducing atmosphere, and see Table 8 for the reducibility comparison between cold-consolidated carbon-containing pellets and pellets in Example 2 of the present invention. .

Table 7 Comparison of the strength of Example 2 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere (N/ball)

Table 8 Comparison of reducibility between cold-consolidated carbon-containing pellets and pellets in Example 2 of the present invention

Example 3

The cold-solidified carbon-containing pellets for blast furnaces in the invention use iron and steel plant dust and quicklime as raw materials. Table 9 shows the raw material composition of the cold-solidified carbon-containing pellets in Example 3 of the present invention.

Table 9 Raw material composition (%) of cold-solidified carbon-containing pellets in Example 1 of the present invention

Grind the mixed materials until the proportion of finer than 200 mesh accounts for more than 90%, and then mix them in proportion. See Table 10 for the batching scheme of cold-solidified carbon-containing pellets in Example 3 of the present invention.

Table 10 Example 3 of the present invention, cold-consolidated carbon-containing pellet batching scheme

Add water accounting for 20% of the total weight of the mixture into the mixture, mix the water and the mixture evenly, and fully digest after stacking for 2 hours. The mixture is put into a disc pelletizer for pelletizing to obtain carbon-containing pellets.

Transport the green balls to the curing reaction chamber, feed the lime kiln waste gas to the bottom of the green ball curing reaction chamber, control the temperature of the lime kiln waste gas fed into the green ball curing chamber at 120°C, and keep the curing time for more than 32 hours to obtain the finished product blast furnace. Consolidated carbonaceous pellets. See Table 11 for the comparison between the preheated strength of Example 3 of the present invention and other cold-consolidated carbon-containing pellets under a reducing atmosphere, and Table 12 for the comparison of the reducibility of cold-consolidated carbon-containing pellets and pellets in Example 3 of the present invention. .

Table 11 Comparison of the strength of Example 3 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere (N/ball)

Table 12 Comparison of reducibility between cold consolidated carbonaceous pellets and pellets in Example 1 of the present invention

Example 4

The cold-solidified carbon-containing pellets for blast furnaces in the invention use iron and steel plant dust and quicklime as raw materials. See Table 13 for the raw material composition of the cold-solidified carbon-containing pellets in Example 4 of the present invention.

Table 13 Raw material composition (%) of cold-solidified carbon-containing pellets in Example 4 of the present invention

Grind the mixed materials until the ratio of finer than 200 mesh accounts for more than 90%, and then mix them in proportion. See Table 14 for the batching scheme of cold-solidified carbon-containing pellets in Example 4 of the present invention.

Table 14 Batching scheme of cold-consolidated carbon-containing pellets in Example 1 of the present invention

Add water accounting for 20% of the total weight of the mixture into the mixture, mix the water and the mixture evenly, and fully digest after stacking for 2 hours. Put the mixture into the double roller briquetting machine for agglomeration, and press it into pillow-shaped carbon-containing pellets.

Transport the green balls to the curing reaction chamber, feed the lime kiln waste gas to the bottom of the green ball curing reaction chamber, control the temperature of the lime kiln waste gas fed into the green ball curing chamber at 120°C, and keep the curing time for more than 32 hours to obtain the finished product blast furnace. Consolidated carbonaceous pellets. See Table 15 for the strength comparison between Example 4 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere, and Table 16 for the reducibility comparison between cold-consolidated carbon-containing pellets and pellets in Example 4 of the present invention. .

Table 15 Comparison of the strength of Example 4 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere (N/ball)

Table 16: Comparison of reducibility of cold-consolidated carbon-containing pellets and pellets in Example 4 of the present invention

Example 5

The cold-solidified carbon-containing pellets for blast furnaces in the invention use iron and steel plant dust and quicklime as raw materials. See Table 17 for the raw material composition of cold-solidified carbon-containing pellets in Example 6 of the present invention.

Table 17 Raw material composition (%) of cold-solidified carbon-containing pellets in Example 6 of the present invention

Grind the mixed materials until the proportion of finer than 200 mesh accounts for more than 90%, and then mix them in proportion. See Table 18 for the formula of cold-solidified carbon-containing pellets in Example 6 of the present invention.

Table 18 Batching scheme of cold-consolidated carbon-containing pellets in Example 6 of the present invention

Add water accounting for 20% of the total weight of the mixture into the mixture, mix the water and the mixture evenly, and fully digest after stacking for 2 hours. Put the mixture into the double roller briquetting machine for agglomeration, and press it into pillow-shaped carbon-containing pellets.

Transport the green balls to the curing reaction chamber, feed the lime kiln waste gas to the bottom of the green ball curing reaction chamber, control the temperature of the lime kiln waste gas fed into the green ball curing chamber at 120°C, and keep the curing time for more than 32 hours to obtain the finished product blast furnace. Consolidated carbonaceous pellets. See Table 19 for the strength comparison between Example 6 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere, and Table 20 for the reducibility comparison between cold-consolidated carbon-containing pellets and pellets in Example 6 of the present invention. .

Table 19 Comparison of the strength of Example 6 of the present invention after preheating and other cold-consolidated carbon-containing pellets under a reducing atmosphere (N/ball)

Table 20 Comparison of reducibility between cold-consolidated carbon-containing pellets and pellets in Example 6 of the present invention

Claims (4)

1. A method of utilizing lime kiln waste gas to produce blast furnace cold-solidified carbon-containing pellets, characterized in that, (1) Mix carbon-containing materials, iron-containing materials, quicklime, and binders according to the weight percentage of 5-15%, 50%-70%: 15%-25%: 5%-10%; the mixture is finely The proportion of 200 mesh accounts for more than 90%; (2) Add water accounting for 10% to 20% of the total weight of the mixture to the mixture in (1), and fully digest it after stacking for 1 to 3 hours; (3) Carrying out the disc pelletizing of the digested mixture or agglomerating the method of rolling balls to obtain carbon-containing pellets; (4) Transport the green balls to the curing reaction chamber, and pass the lime kiln waste gas into the bottom of the green ball curing reaction chamber. The temperature of the lime kiln waste gas is 100-150 ° C, and the curing time is more than 24 hours. carbon pellets. 2. according to claim 1, utilize lime kiln exhaust gas to produce the method for blast furnace cold consolidation carbonaceous pellets, it is characterized in that, described iron-containing material is iron ore powder, converter dust, electric furnace dust, sintering head dust and One or several kinds of sintered ore. 3. according to claim 1, utilize lime kiln exhaust gas to produce the method for blast furnace cold consolidation carbonaceous pellets, it is characterized in that, described carbonaceous material is coal powder, blast furnace bag ash, blast furnace gravity ash and coking dedusting ash one or several. 4. according to claim 1, utilize lime kiln waste gas to produce the method for blast furnace cold consolidation carbonaceous pellets, it is characterized in that, described binding agent is any one in bentonite, sodium carboxymethyl cellulose and above.