REDUCING AND NON-BLAST FURNACE SMELTING METHOD OF ALKALINE VANADIUM-TITANIUM PELLETS AND HOT-PRESSED CARBON-CONTAINING VANADIUM-TITANIUM PELLETS

Abstract

A reducing and non-blast furnace smelting method of alkaline vanadium-titanium pellets and hot-pressed carbon-containing vanadium-titanium pellets. By upgrading the vanadium-titanium concentrates, improving quality of the reducing gas, increasing the proportion of the reduction section of the shaft furnace, removing the cooling section to achieve hot charging, and improving the electric furnace, the method accelerates the reduction rate of the vanadium-titanium pellets reduced by the gas-based shaft furnace, improves the final reduction degree of the vanadium-titanium pellets, achieves the rapid non-blast furnace smelting of the vanadium-titanium pellets. Addition of the hot-pressed carbon-containing pellets can alleviate the problems caused by reduction swelling of pellets, overcome the problem that the alkaline vanadium titanium pellets do not meet the requirement of a reduction swelling rate of less than 10% of fed pellet ore for gas-based shaft furnace since its high reduction swelling rate, and broaden the variety of fed pellets for the shaft furnace.

Claims

1. A reducing and non-blast furnace smelting method of alkaline vanadium-titanium pellets and hot-pressed carbon-containing vanadium-titanium pellets, comprising the following steps of: {circle around (1)} upgrading a vanadium-titanium iron concentrate, and preparing alkaline pellets having an alkalinity of 0.6-0.7 from the upgraded vanadium-titanium iron concentrate and fine-grained limestone by using a belt roaster with a preheating temperature of 900-950 C., a preheating time of 13-17 minutes, a roasting temperature of 1250-1280 C., and a roasting time of 15-20 minutes; {circle around (2)} preparing hot-pressed carbon-containing pellets with the upgraded vanadium-titanium iron concentrate and a pulverized coal, wherein a proportion of the pulverized coal is 17-28%, and a proportion of the upgraded vanadium-titanium iron concentrate is 72-83%, hot-pressing a uniform mixture of the upgraded vanadium-titanium iron concentrate and the pulverized coal to mold at 250-350 C., and then introducing nitrogen at 900-950 C. to remove volatile components in the pulverized coal; {circle around (3)} by means of a pressure swing adsorption process, preparing H.sub.2 with coke oven gas as a raw material, and preparing CO with converter gas as a raw material, and mixing the prepared H.sub.2 and CO to obtain a reducing gas, featuring H.sub.2/CO of greater than or equal to 8, and H.sub.2+CO of greater than or equal to 90%; {circle around (4)} preparing a fuel gas by mixing a remained gas after capturing CO.sub.2 from blast furnace gas with the prepared CO; {circle around (5)} feeding the reducing gas and the fuel gas into a shaft furnace through a double-layer conveying pipeline, wherein the fuel gas and air are fed through an inner layer, the reducing gas is fed through an outer layer, and the inner layer and the outer layer are isolated by a high thermal conductivity refractory, wherein a volume ratio of the fuel gas to the air is greater than or equal to 2.3:1, a temperature of the reducing gas is 1050-1080 C., and a pressure of the reducing gas is 0.7-0.8 MPa; {circle around (6)} using a burden structure, containing the alkaline pellets and the hot-pressed carbon-containing pellets with a mass ratio of 1-5:1, as a shaft furnace burden, arranging the conveying pipeline of the reducing gas at a bottom of a reducing section and at half of the reducing section of the shaft furnace, removing a cooling section of the shaft furnace, increasing a length ratio of the reducing section to account for 60-80% of a height of the shaft furnace, and providing an unloading section with a metallized pellet storage bin having valves at both upper and lower ends, wherein the storage bin is provided with an inlet and an outlet, a tail gas after combustion of the fuel gas is introduced to the storage bin, and a content of O.sub.2 in the tail gas is less than or equal to 3%; and {circle around (7)} an electric furnace having a structure with four feed ports, two iron notches and two slag notches, achieving a continuous loading.

2. The reducing and non-blast furnace smelting method of alkaline vanadium-titanium pellets and hot-pressed carbon-containing vanadium-titanium pellets according to claim 1, wherein the upgraded vanadium-titanium iron concentrate in step {circle around (1)} features in a TFe content of 60-64%, a TiO.sub.2 content of 8-11%, and a passing rate of 800-mesh sieve greater than 90%; and a proportion of the fine-grained limestone with a particle size of 0.1 mm is greater than or equal to 95%.

3. The method according to claim 1, wherein the alkaline pellets prepared in step {circle around (1)} features a TFe content of greater than or equal to 60%, a reduction swelling rate of less than or equal to 12%, and an average crushing strength of pellet of greater than or equal to 3000 N.

4. The method according to claim 1, wherein the pulverized coal for preparing the hot-pressed carbon-containing pellets in step {circle around (2)} is one-third coking coal or fat coal, and the pulverized coal features a volatile component content of 20-32%, a fixed carbon content of 60-70%, and an ash content of 6-12%.

5. The method according to claim 1, wherein the hot-pressed carbon-containing pellets prepared in step {circle around (2)} features a TFe content of 45-56%, a C content of 10-22%, and an average crushing strength of greater than or equal to 5500 N.

6. The method according to claim 1, wherein a metallization ratio of the metallized pellets prepared by the shaft furnace is greater than or equal to 92%.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] The present invention is further described below with reference to specific embodiments, but is not limited in any way. To avoid repetition, the raw materials in the following embodiments are commercially available unless otherwise specified, and the methods used are conventional methods unless otherwise specified. Crushing strength of green pellets is determined by pressure method with a detection equipment of pellet crushing strength tester according to the standard GB/T 14201-2018 of Iron Ore Pellets for Blast Furnace and Direct Reduction FeedstocksDetermination of The Crushing Strength. Reduction swelling index is determined according to the standard GB/T 13240-2018 of Iron Ore Pellets for Blast Furnace FeedstocksDetermination of the Free-Swelling Index. Reduction rate index and the final reduction degree are determined and calculated according to standard GB/T 13241-2017 of Iron Ores-Determination of Reducibility.

[0021] A reducing and non-blast furnace smelting method of alkaline vanadium-titanium pellets and hot-pressed carbon-containing vanadium-titanium pellet as shown in Embodiments 1-3 includes the following steps, and the difference between each the embodiment and the comparative example is illustrated in the following implementation content.

[0022] {circle around (1)} Upgrade a vanadium-titanium iron concentrate, and prepare alkaline pellets having an alkalinity of 0.6-0.7 from the upgraded vanadium-titanium iron concentrate and fine-grained limestone.

[0023] The vanadium-titanium iron concentrate before upgrading features a TFe content of 55%, a TiO.sub.2 content of 12%, and a passing rate of 200-meshe sieve of 88%. After grinding until the proportion of the vanadium-titanium iron concentrate with a particle size of 0.038 mm accounts for greater than or equal to 90%, the grinded concentrate is roughly selected with a 0.2 mT magnetic field to obtain a roughing iron ore powder and a tailings, then the roughing iron ore powder is finely selected with a 0.15 mT magnetic field, the tailings after roughly selecting is subject to scavenging with a 0.2 mT magnetic field, and the ore powders after finely selecting and scavenging are the upgraded vanadium-titanium iron concentrate. The upgraded vanadium-titanium iron concentrate features a TFe content of 64%, a TiO.sub.2 content of 10%, a passing rate of 800-mesh sieve of 90%. A proportion of the fine-grained limestone with a particle size ratio of 0.1 mm is 96%.

[0024] The alkaline pellets are prepared by using a belt roaster with a preheating temperature of 900-950 C., a preheating time of 17 minutes, a roasting temperature of 1250-1280 C., and a roasting time of 20 minutes.

[0025] The alkaline pellets prepared in step {circle around (1)} features a TFe content of 64%, a reduction swelling rate of 9%, and an average crushing strength of pellet of 3100 N.

[0026] {circle around (2)} Prepare hot-pressed carbon-containing pellets with the upgraded vanadium-titanium iron concentrate and a pulverized coal, wherein a proportion of the pulverized coal is 24%, and a proportion of the upgraded vanadium-titanium iron concentrate is 76%. A uniform mixture of the upgraded vanadium-titanium iron concentrate and the pulverized coal is hot-pressed and molded at 250-350 C., and then nitrogen is introduced at 900-950 C. to remove volatile components in the pulverized coal.

[0027] In step {circle around (2)}, the pulverized coal for preparing the hot-pressed carbon-containing pellets is one-third coking coal. The pulverized coal features a volatile component content of 26%, a fixed carbon content of 65%, and an ash content of 8%. The hot-pressed carbon-containing pellets prepared in step {circle around (2)} features a TFe content of 50%, a C content of 16%, and an average crushing strength of greater than or equal to 5500 N. Shrinkage occurs during the reduction process with a shrinkage rate of 8-15%, which can supplement heat inside the shaft furnace, compensating some of the heat absorbed during H.sub.2 reduction process.

[0028] {circle around (3)} By means of a pressure swing adsorption process, prepare H.sub.2 with coke oven gas as a raw material and prepare CO with converter gas as a raw material, where a purity of each the prepared H.sub.2 and CO is greater than or equal to 99%. Mix the prepared H.sub.2 and CO to obtain a reducing gas, featuring H.sub.2/CO of greater than or equal to 8, H.sub.2+CO of greater than or equal to 90%.

[0029] {circle around (4)} By mixing a remained gas after capturing CO.sub.2 from blast furnace gas with the prepared CO, prepare a fuel gas for heating the reducing gas.

[0030] Collect blast furnace gas and capture CO.sub.2 from the blast furnace gas, enabling CO.sub.2 content in the remained gas after capturing CO.sub.2 from blast furnace gas to be 3% and a CO content to be greater than or equal to 30%. Mix the CO.sub.2-removed blast furnace gas and the prepared CO to prepare the fuel gas, of which an amount of the CO.sub.2-removed blast furnace gas is 10-30%. The fuel gas features a CO volume content of greater than or equal to 80% and a N2 volume content of less than or equal to 20%.

[0031] {circle around (5)} Feed the reducing gas and the fuel gas into a shaft furnace through a double-layer conveying pipeline, where the fuel gas and air are fed through an inner layer, the reducing gas is fed through an outer layer, and the inner layer and the outer layer are isolated with each other by a high thermal conductivity refractory. In addition, a volume ratio of the fuel gas to the air is greater than or equal to 2.3:1 to ensure excessive fuel gas, enabling a O.sub.2 content in the tail gas after combustion to be less than 3%. A temperature of the reducing gas is 1050 C., a pressure of the reducing gas is 0.7-0.8 MPa.

[0032] {circle around (6)} A mass ratio of the alkaline pellets and the hot-pressed carbon-containing pellets of the burden structure is shown in Table 1. In addition, the conveying pipeline of the reducing gas is arranged at a bottom of a reducing section and at half of the reducing section of the shaft furnace. The reducing gas pipeline arranged at half of the reduction section is configured for heat replenishment to the middle-upper part of the reduction section of the shaft furnace, accounting for 30-50% of a total length of the conveying pipeline of the reducing gas, which is adjusted according to the H.sub.2 content in the reducing gas. The cooling section of the shaft furnace is removed, a length ratio of the reducing section is increased to account for 60-80% of a height of the shaft furnace, and a hot charging process from the shaft furnace to the electric furnace is adopted. An unloading section is provided with a metallized pellet storage bin having valves at both upper and lower ends, the storage bin is provided with an inlet and an outlet. The tail gas (with a O.sub.2 content of less than or equal to 3%) after combustion of the fuel gas is introduced into the unloading section. The tail gas contains a lot of CO and a very low O.sub.2 content, having a reductive overall atmosphere, which can be used for carburizing and improving the metallization rate, while providing heat for the metallized pellets, keeping the temperature of the pellets in the storage bin higher than or equal to 800 C., so as to ensure that the metallization ratio of the metallized pellets entering the electric furnace can be greater than or equal to 92%.

[0033] {circle around (7)} The electric furnace has a structure with four feed ports, two iron notches, and two slag notches, which can achieve a continuous loading technology.

[0034] The electric furnace is provided with four feed ports, of which opposite two are pellet feed inlets, and the other two are respectively a solvent inlet and a fuel inlet. Each the pellet feed inlet is connected to the shaft furnace storage bin through a chute, so as to realize the hot charging of the metallized pellets, and a hot charging temperature is greater than or equal to 700 C. The electric furnace is provided with upper and lower iron notches and upper and lower slag notches. The upper and lower iron notches are configured to discharge iron. The upper slag notch is configured to control the liquidus and the pressure in the furnace, the lower slag notch is flush with the upper iron notch for slagging after discharging iron. A remaining iron process is adopted for smelting, and an addition amount of carbon is 8-13%.

[0035] The vanadium-bearing melted iron features a C content of 2.8%-3.8%.

[0036] The molten slag features a FeO content of 2%-5%, R.sub.2 of 0.5-0.6, and a TiO.sub.2 content of 30%-40%.

Embodiment 1

[0037] In Embodiment 1, a reducing gas, with a H.sub.2 content of 80%, a CO content of 10%, a N2 content of 7%, and a CO.sub.2 content of 3%, was used. The reducing temperature was 1050 C., and the flow rate of the reducing gas was 15 L/min. The material structure was, as shown in Table 1, 83% of alkaline pellets and 17% of hot-pressed carbon-containing pellets. The reduction rate index and the final reduction degree determined by the laboratory are shown in Table 1.

Embodiment 2

[0038] In Embodiment 2, a reducing gas, with a H.sub.2 content of 80%, a CO content of 10%, a N2 content of 7%, and a CO.sub.2 content of 3%, was used. The reducing temperature was 1050 C., and the flow rate of the reducing gas was 15 L/min. The material structure was, as shown in Table 1, 77.5% of alkaline pellets and 22.5% of hot-pressed carbon-containing pellets. The reduction rate index and the final reduction degree determined by the laboratory are shown in Table 1.

Embodiment 3

[0039] In Embodiment 3, a reducing gas, with a H.sub.2 content of 80%, a CO content of 10%, a N2 content of 7%, and a CO.sub.2 content of 3%, was used. The reducing temperature was 1050 C., and the flow rate of the reducing gas was 15 L/min. The material structure was, as shown in Table 1, 72% of alkaline pellets and 28% of hot-pressed carbon-containing pellets. The reduction rate index and the final reduction degree determined by the laboratory are shown in Table 1.

Comparative Example 1

[0040] In comparative example 1, a reducing gas, with a H.sub.2 content of 66%, a CO content of 11%, a N2 content of 20%, and a CO.sub.2 content of 3%, was used. The reducing temperature was 1050 C., and the flow rate of the reducing gas was 15 L/min. The material structure was, as shown in Table 1, 100% of alkaline pellets. The reduction rate index and the final reduction degree determined by the laboratory are shown in Table 1.

TABLE-US-00001 TABLE 1 Comparison of reduction index of pellet ore Final Reduction reduction rate index degree Name Material structure (wt %/min) (%) Comparative 100% of alkaline pellets 2.4 91.72 example 1 Embodiment 1 83% of alkaline pellets + 17% 2.6 93.23 of hot-pressed carbon-containing pellets Embodiment 2 77.5% of alkaline pellets + 2.9 94.95 22.5% of hot-pressed carbon-containing pellets Embodiment 3 72% of alkaline pellets + 28% 3.1 96.48 of hot-pressed carbon-containing pellets

[0041] From the above table, it can be seen that the reduction rate index and the final reduction degree of the embodiments were higher than those of the comparative example, which is due to the increase of the H.sub.2 content, resulting in increase of the reduction capability, so that the reduction speed is accelerated. In the embodiments, the reduction rate and the final reduction degree were increased as increase of the proportion of the hot-pressed carbon-containing pellets, which is mainly due to the fact that C in the pellets participates in the reduction reaction, accelerating the reduction speed. Further, C directly reduces V and Ti which cannot be reduced by H.sub.2 and CO to enter the molten iron, so that the final degree and the reduction rate are both enhanced.

[0042] For those skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical contents disclosed above, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present disclosure without departing from the technical solution of the present invention shall still belong to the protection scope of the technical solution of the present invention.