阅读说明：本技术 一种强化铬铁矿气基固态还原的方法 (Method for strengthening gas-based solid reduction of chromite ) 是由 张峰 朱德庆 潘建 于 2021-07-23 设计创作，主要内容包括：本发明公开了一种强化铬铁矿气基固态还原的方法,按照如下方法制备：1)将经过预处理的铬铁矿、红土镍矿、磁铁矿以及熔剂进行混合,然后造球得到生球,所述熔剂为生石灰；2)将制备得到的生球焙烧,得到含铬镍铁矿氧化球团；3)将制得的含铬镍铁矿氧化球团放入还原炉中,在800℃-10000℃、还原气体条件下进行气基固态还原反应,得到含铬镍铁矿预还原球团。通过优化配矿以及氧化焙烧的手段调控铬铁矿的氧化反应及微观结构,使铬铁矿发生矿相重构和微观结构改变,生成有利于发生还原反应的新物相和新的微观结构,从而改善铬铁矿的还原性能。(The invention discloses a method for strengthening gas-based solid reduction of chromite, which comprises the following steps: 1) mixing the pretreated chromite, laterite-nickel ore, magnetite and flux, and pelletizing to obtain green pellets, wherein the flux is quicklime; 2) roasting the prepared green pellets to obtain chromium-containing nickel iron ore oxidized pellets; 3) and putting the prepared chromium-containing nickel iron ore oxidized pellets into a reduction furnace, and carrying out gas-based solid reduction reaction at the temperature of 800-10000 ℃ under the condition of reducing gas to obtain the chromium-containing nickel iron ore pre-reduced pellets. The oxidation reaction and the microstructure of the chromite are regulated and controlled by optimizing ore blending and oxidizing roasting, so that the ore phase reconstruction and the microstructure change of the chromite are generated, a new phase and a new microstructure which are beneficial to the reduction reaction are generated, and the reduction performance of the chromite is improved.)

1. A method for strengthening gas-based solid reduction of chromite is characterized by comprising the following steps:

1) pelletizing: mixing the pretreated chromite, laterite-nickel ore, magnetite and flux, and pelletizing to obtain green pellets, wherein the flux is quicklime;

2) oxidizing and roasting: roasting the prepared green pellets to obtain chromium-containing nickel iron ore oxidized pellets;

3) pre-reduction: and putting the prepared chromium-containing nickel iron ore oxidized pellets into a reduction furnace, and carrying out gas-based solid reduction reaction at the temperature of 800-1000 ℃ under the condition of reducing gas to obtain the chromium-containing nickel iron ore pre-reduced pellets.

2. The process for enhanced chromite gas-based solid state reduction according to claim 1, wherein: the mass ratio of the chromite to the laterite-nickel ore to the magnetite is 10-35:30: 60-35.

3. A process for enhancing the gas-based solid state reduction of chromite ore according to claim 1 or 2, characterised in that: the particle size of the quicklime is less than 0.074mm, and the alkalinity range of the pellets is controlled to be 0.2-1.4.

4. A process for enhancing the gas-based solid state reduction of chromite ore according to claim 3, characterised in that: the chromite pretreatment method comprises the following steps: wet ball milling chromite until the particle size is more than 90% and less than 0.074mm, and the specific surface area is not less than 1500cm²/g。

5. A process for enhancing the gas-based solid state reduction of chromite ore according to claim 3, characterised in that: the pretreatment method of the laterite-nickel ore comprises the following steps: drying laterite-nickel ore to water content of below 10%, crushing with a double-roll crusher to water content of below 3mm, and grinding with a rod mill until the particle diameter is 75% above and less than 0.074mm, and the specific surface area is not less than 1800cm²/g。

6. A process for enhancing the gas-based solid state reduction of chromite ore according to claim 3, characterised in that: and ball-milling the magnetite until the particle size is more than 75% and less than 0.074 mm.

7. The method for enhancing the gas-based solid state reduction of chromite according to claim 6, wherein: pelletizing by using a disc pelletizer, wherein the pelletizing water content is 13-15 wt%, the pelletizing time is 12-18 min, and the green pellet granularity is controlled to be 8-16 mm.

8. The process for enhanced chromite gas-based solid state reduction according to claim 7, wherein: oxidizing roasting is carried out on a belt type roasting machine, the preheating temperature is 850-1000 ℃, and the preheating time is 6-16 min; the roasting temperature is 1230-1320 ℃, and the roasting time is 10-16 min; the soaking temperature is 800-1050 ℃, and the soaking time is 3-9 min.

9. The process for enhanced chromite gas-based solid state reduction according to claim 8, wherein: the reduction time is 30-150min, the flow rate of the reduction gas is 800Nl/H, and the reduction gas is H₂A mixture of CO.

Technical Field

The invention relates to the technical field of stainless steel mother liquor, in particular to a method for strengthening gas-based solid reduction of chromite.

Background

Chromite is an important strategic resource and is a main raw material for smelting high-carbon ferrochrome. The chromium ore resources in China are scarce, almost all the chromium ore resources depend on import, and the external dependence degree reaches 95 percent, so that the healthy sustainable development of the stainless steel industry in China is greatly restricted. The traditional high-carbon ferrochrome production process in China not only needs to take increasingly scarce and expensive chromite lump ore as a raw material, but also consumes a large amount of precious electric energy, which leads to high production cost of stainless steel. In recent years, with the gradual depletion of chromite lump ore resources, more than 80% of chromite produced in the world is fine ore and concentrate, and the chromite fine ore (or concentrate) becomes a main chromite resource. The method adopts a concentrate prescription, makes chromium ore powder agglomerated, and smelts high-carbon ferrochrome by clinker, hot material and pre-reduction material, which is a future development trend, can effectively reduce energy consumption, improve chromium recovery rate and reduce production cost.

Therefore, if the low-grade chromite concentrate with low price is used as a raw material for agglomeration, the chromium-containing stainless steel mother liquor is produced by a smelting reduction process to replace part of high-carbon ferrochrome, and the purpose of replacing electricity with coal is realized, so that the purposes of reducing the production energy consumption and the production cost of stainless steel can be achieved, and the method has important significance for ensuring the healthy and sustainable development of the stainless steel industry in China. However, it should be noted that since chromite belongs to a refractory mineral with a high melting point, it requires a high reduction temperature, and further, the slag and the chrome-containing molten iron require a high smelting temperature to ensure good fluidity, which results in high energy consumption for smelting and poor fluidity of the slag iron. Therefore, improving the solid reduction performance of chromite and improving the slag iron fluidity in the smelting process are the key points for realizing energy conservation and consumption reduction. At present, strengthening measures for the solid-state reduction of chromite mainly focus on two aspects of the construction and the development of additives and the pre-oxidation treatment. It should be noted that the use of additives has certain limitations, such as increasing the production cost, introducing other impurity elements, and even some additives (such as halide) generate harmful gases in high temperature reaction, resulting in environmental pollution. Therefore, in the chromite solid-state reduction process, the additives other than the carbonaceous additives (mainly coal and coke) are not widely used. The pre-oxidation treatment can improve the reduction performance of chromite, but the defects of high reduction temperature and high energy consumption still exist.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for strengthening gas-based solid reduction of chromite, which regulates and controls the oxidation reaction and microstructure of the chromite by optimizing ore blending and oxidizing roasting, so that the chromite is subjected to ore phase reconstruction and microstructure change to generate a new phase and a new microstructure which are beneficial to the reduction reaction, thereby improving the reduction performance of the chromite.

In order to achieve the aim, the invention provides a method for strengthening gas-based solid-state reduction of chromite, which is characterized by comprising the following steps:

1) pelletizing: mixing the pretreated chromite, laterite-nickel ore, magnetite and flux, and pelletizing to obtain green pellets, wherein the flux is quicklime;

2) oxidizing and roasting: roasting the prepared green pellets to obtain chromium-containing nickel iron ore oxidized pellets;

3) pre-reduction; and putting the prepared chromium-containing nickel iron ore oxidized pellets into a reduction furnace, and carrying out gas-based solid reduction reaction at the temperature of 800-10000 ℃ under the condition of reducing gas to obtain the chromium-containing nickel iron ore pre-reduced pellets.

In the pre-reduction process of the oxidized pellets of the chromium-containing nickel iron ore, the main reaction is that iron oxide and nickel oxide are reduced into metallic iron and nickel, and the main reaction in the melting process of the chromium-containing nickel iron ore is the reduction of chromium oxide; therefore, the method establishes an optimal reduction process according to the reduction characteristics of different oxides in the pellets, realizes the segmental reduction, and the pre-reduced metallic iron and nickel can effectively promote the reduction of chromium oxide, thereby greatly saving the energy consumption.

In the scheme, the method comprises the following steps: the mass ratio of the chromite to the laterite-nickel ore to the magnetite is 10-35:30: 60-35.

The invention provides a new idea for preparing chromium-containing nickel iron ore oxidized pellets by using the chromite, the laterite-nickel ore and the magnetite as raw materials by utilizing the characteristic that the mineral characteristics among the chromite, the laterite-nickel ore and the magnetite have complementarity, fully exerts the synergistic strengthening effect among the three minerals and realizes the advantage complementation. Meanwhile, the quick lime is added into the mixture to regulate the liquid phase amount of the pellets in the oxidizing roasting process, so that the liquid phase adhesion of the pellets is improved, and finally, the chromium-containing nickel iron ore oxidized pellets with high strength and excellent metallurgical performance are prepared.

According to the invention, agglomeration of chromite, laterite-nickel ore and magnetite can be realized in one step, and the chromite has the characteristics of poor agglomeration performance, compact structure, high chromium, high aluminum and high magnesium and is difficult to agglomerate; the laterite-nickel ore has the characteristics of excellent balling performance, high crystal water content, looseness, porosity, low iron, high silicon and high magnesium, and the magnetite has the characteristics of high iron, high FeO, low magnesium and low aluminum. The good balling performance of the laterite-nickel ore can improve the balling performance of the chromite, and the high silicon characteristic of the laterite-nickel ore can promote the chromite to form a low-melting-point phase in the high-temperature roasting process. The holes generated by losing the crystal water after roasting the laterite-nickel ore can be just filled by the chromite with compact structure, the magnetite can strengthen the recrystallization and consolidation of the iron oxide in the roasted pellet, the oxidation and consolidation of the chromite are promoted, and the energy consumption can be reduced by the oxidation and heat release of the magnetite. Through mixing and pelletizing the three ores with complementary performance, the synergistic strengthening effect among the three ores is fully exerted, and the advantage complementation is realized.

In addition, because the laterite-nickel ore has excellent balling performance, the balling performance of the chromite can be effectively improved by adding the laterite-nickel ore, and therefore, qualified green pellets can be obtained without adding binders such as bentonite and the like into the balling raw materials.

Because the laterite-nickel ore has excellent balling performance, the balling performance of the chromite can be effectively improved by adding the laterite-nickel ore, and the strength of the raw ball of the chromium-containing nickel iron ore can be greatly improved, so that the qualified raw ball can be obtained without adding binders such as bentonite and the like into the balling raw materials.

The fluxing agent is added into the pelletizing mixture, so that the liquid phase generation temperature of the chromium-containing nickel iron ore pellets in the roasting process can be effectively reduced, the generation of liquid phase in the pellets is promoted, and the solid phase bonding and the liquid phase bonding of the pellets can be enhanced by regulating and controlling the liquid phase generation amount of the pellets, so that the compressive strength of the chromium-containing nickel iron ore oxidized pellets is improved.

In the scheme, the method comprises the following steps: the particle size of the quicklime is less than 0.074mm, and the alkalinity range of the pellets is controlled to be 0.2-1.4.

In the scheme, the method comprises the following steps: the chromite pretreatment method comprises the following steps: wet ball milling chromite until the particle size is more than 90% and less than 0.074mm, and the specific surface area is not less than 1500cm²/g。

In the scheme, the method comprises the following steps: the pretreatment method of the laterite-nickel ore comprises the following steps: drying laterite-nickel ore to water content of below 10%, crushing with a double-roll crusher to water content of below 3mm, and grinding with a rod mill until the particle diameter is 75% above and less than 0.074mm, and the specific surface area is not less than 1800cm²/g。

In the scheme, the method comprises the following steps: and ball-milling the magnetite until the particle size is more than 75% and less than 0.074 mm.

In the scheme, the method comprises the following steps: pelletizing by using a disc pelletizer, wherein the pelletizing water content is 13-15 wt%, the pelletizing time is 12-18 min, and the green pellet granularity is controlled to be 8-16 mm.

In the scheme, the method comprises the following steps: oxidizing roasting is carried out on a belt type roasting machine, the preheating temperature is 850-1000 ℃, and the preheating time is 6-16 min; the roasting temperature is 1230-1320 ℃, and the roasting time is 10-16 min; the soaking temperature is 800-1050 ℃, and the soaking time is 3-9 min.

In the scheme, the method comprises the following steps: the reduction temperature range is 800-₂A mixture of CO.

In the scheme, the method comprises the following steps: the melting temperature is 1450-1600 ℃, the melting time is 30-120 min, the coke consumption is 5-20 wt%, and the binary alkalinity of the slag is 0.7-1.2.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a method for strengthening gas-based solid reduction of chromite, which aims at the problems of difficult reduction of chromite, high smelting energy consumption and the like, abandons the traditional idea of strengthening the solid reduction of chromite through an additive, develops a new way, starts with changing the mineral composition and microstructure of chromite, utilizes the complementary characteristics of laterite-nickel ore and the mineral compositions of magnetite and chromite, and effectively improves the reduction performance of chromite through optimizing ore blending.

(2) The invention provides a method for strengthening gas-based solid reduction of chromite, which comprises the steps of preparing chromium-containing nickel-iron ore pellets by taking chromite, laterite-nickel ore and magnetite as raw materials, purposefully regulating and controlling phase composition, microstructure, subsequent smelting slag type and stainless steel mother liquor component of the chromite by comprehensive means of optimizing ore blending, optimizing oxidizing and roasting system, adjusting pellet alkalinity and the like, so that the chromite is subjected to ore phase reconstruction, new minerals and microstructures easy to reduce are generated, the problem of difficult reduction of the chromite is solved, the subsequent smelting problem is solved, the purposes of saving energy and reducing consumption are achieved, and a new way is provided for efficient utilization of the chromite. The pre-reduced pellets obtained after reduction can be used as raw materials for smelting chromium-and nickel-containing stainless steel mother liquor in a smelting reduction furnace, a blast furnace or an electric furnace, and the produced stainless steel mother liquor can replace part of ferrochromium and ferronickel alloy, thereby providing high-quality furnace charges for smelting stainless steel.

Drawings

FIG. 1 is a microstructure of chromium spinel in pellets before oxidative roasting treatment.

FIG. 2 is a microstructure diagram of chromium spinel in pellet with natural basicity after oxidizing roasting treatment.

FIG. 3 is a microstructure diagram of chromium spinel in pellet with natural basicity after oxidizing roasting treatment.

Fig. 4 is a microstructure diagram of chromium spinel in pre-reduced natural basicity pellets.

Fig. 5 is a microstructure diagram of chromium spinel in pre-reduced 1.0 basicity pellets.

Detailed Description

The invention will be further explained with reference to specific examples

Example 1

A method for strengthening gas-based solid reduction of chromite comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying laterite-nickel ore to moisture content of 1Less than 0 percent (weight), crushing the laterite-nickel ore to less than 3mm by a double-roll crusher, and then grinding the laterite-nickel ore by a rod mill until the grain diameter is more than 75 percent and less than 0.074mm and the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: the magnetite fraction of less than 0.074mm accounts for over 75 wt%. Mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite-30: 30: 40.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 14%, and the pelletizing time is 14min, so that the natural alkalinity green pellets are obtained. The falling strength of the green pellets is 12.3 times/0.5 m, the compressive strength is 14.6N/green pellets, and the bursting temperature is 405 ℃.

(5) Oxidizing and roasting: and (3) carrying out oxidation roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min. The roasting temperature is 1320 ℃, and the roasting time is 16 min. Soaking temperature is 1000 ℃, soaking time is 5min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 607N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (3) into a reduction furnace, and reducing the pellets for 60min at a reduction gas flow rate of 800Nl/H and a reduction temperature of 950 ℃ and a reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 79.94 percent, and the compressive strength of the pellets is 311N/pellet.

Example 2

A method for strengthening gas-based solid reduction of chromite comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying laterite-nickel ore to moisture content below 10 wt%, and crushing laterite with a double-roll crusherCrushing nickel ore to below 3mm, grinding with rod mill until the particle diameter is more than 75% and less than 0.074mm, and the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: the magnetite fraction of less than 0.074mm accounts for over 75 wt%. Mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite (30: 30: 40) is mixed with 11.6 wt% of quicklime to obtain a mixed material with binary alkalinity of 1.0.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 14%, and the pelletizing time is 14min, so that green pellets are obtained. The falling strength of the green pellets is more than 20 times per 0.5m, the compressive strength is 19.6N per pellet, and the bursting temperature is 405 ℃.

(5) Oxidizing and roasting: and (3) carrying out oxidation roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min. The roasting temperature is 1230 ℃, and the roasting time is 12 min. The soaking temperature is 900 ℃, the soaking time is 5min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 1991N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (5) into a reduction furnace, and reducing the pellets for 60min at a reduction gas flow rate of 800Nl/H and a reduction temperature of 950 ℃ and a reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 80.41%, and the compressive strength of the pellets is 994N/pellet.

(7) Melting and separating: and (3) uniformly mixing the chromium-containing nickel iron ore pre-reduced pellets prepared in the step (6) with coke accounting for 10 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for smelting at 1600 ℃ for 120min, adjusting the binary basicity of slag to 0.8 to obtain a chromium-nickel-containing stainless steel mother liquor, wherein the contents of Fe, Cr and Ni in the stainless steel mother liquor are 74.33%, 15.43% and 1.11%, and the recovery rates are 95.44%, 88.42% and 98.87%, respectively. And melting and separating to be used as stainless steel mother liquor.

Example 3

A method for strengthening gas-based solid reduction of chromite comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying the laterite-nickel ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite (35: 30: 35) is mixed with 18.6% of quicklime to obtain a mixed material with binary alkalinity of 1.4.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 14%, and the pelletizing time is 14min, so that green pellets are obtained. The falling strength of the green pellets is 10.7 times/0.5 m, the compressive strength is 16N/green pellets, and the bursting temperature is 342 ℃.

(5) Roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min; the roasting temperature is 1260 ℃, and the roasting time is 14 min; soaking at 800 deg.c for 5min to obtain oxidized pellet of chromium-containing nickel iron ore with compression strength of 2074N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (5) into a reduction furnace, and reducing the pellets for 30min at the reduction gas flow rate of 800Nl/H and the reduction temperature of 1000 ℃ and the reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 80.52%, and the compressive strength of the pellets is 998N/pellet.

(7) Melting and separating: and (3) uniformly mixing the chrome-containing nickel iron ore pre-reduced pellets prepared in the step (6) with coke accounting for 5 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for melting at 1450 ℃, for 120min, wherein the binary basicity of the slag is 0.7, so as to obtain a chrome-nickel-containing stainless steel mother liquor, wherein the contents of Fe, Cr and Ni in the stainless steel mother liquor are 81.90%, 12.23% and 1.09%, and the recovery rates are 84.72%, 60.12% and 87.93%. And melting and separating to be used as stainless steel mother liquor.

Example 4

A method for strengthening gas-based solid reduction of chromite specifically comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying the laterite-nickel ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite is 10:30:60, 16.8 wt% of quicklime is added, and a mixed material with binary alkalinity of 1.4 is obtained.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 15%, and the pelletizing time is 18min, so that green pellets are obtained. The falling strength of green pellets is more than 20 times per 0.5m, the compressive strength is 17.3N per green pellet, and the bursting temperature is 345 ℃.

(5) Oxidizing and roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 1000 ℃, and the preheating time is 6 min; the roasting temperature is 1230 ℃, and the roasting time is 14 min; the soaking temperature is 1050 ℃, the soaking time is 3min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 2092N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (5) into a reduction furnace, and reducing at the reduction temperature of 1000 ℃ and the reduction gas flow of 800Nl/hTime 30min, volume ratio of reducing gas H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 80.52%, and the compressive strength of the pellets is 1099N/pellet.

(7) Melting and separating: and (3) uniformly mixing the chromium-containing nickel iron ore pre-reduced pellets prepared in the step (6) with coke which accounts for 20 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for smelting at 1600 ℃, wherein the smelting time is 30min, the binary basicity of the slag is 1.2, so as to obtain a chromium-nickel-containing stainless steel mother liquor, wherein the contents of Fe, Cr and Ni in the obtained stainless steel mother liquor are 74.50%, 15.01% and 1.02%, and the recovery rates are 91.84%, 90.18% and 92.72% respectively. And melting and separating to be used as stainless steel mother liquor.

Example 5

A method for strengthening gas-based solid reduction of chromite specifically comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying the laterite-nickel ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite (35: 30: 35) is mixed with 1.6 wt% of quicklime to obtain a mixed material with binary alkalinity of 0.2.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 15%, and the pelletizing time is 18min, so that green pellets are obtained. The falling strength of the green pellets is 7.5 times/0.5 m, the compressive strength is 16.8N/green pellets, and the bursting temperature is 455 ℃.

(5) Oxidizing and roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 1000 ℃, and the preheating time is 6 min; the roasting temperature is 1320 ℃, and the roasting time is 10 min; the soaking temperature is 1050 ℃, the soaking time is 3min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 2699N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (5) into a reduction furnace, and reducing the pellets for 150min at the reduction gas flow rate of 800Nl/H and the reduction temperature of 800 ℃ and the reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 70.21 percent, and the compressive strength of the pellets is 989N/pellet.

7) Melting and separating: and (3) uniformly mixing the chrome-containing nickel iron ore pre-reduced pellets prepared in the step (6) with coke accounting for 5 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for melting at 1450 ℃, for 120min, wherein the binary basicity of the slag is 0.7, so as to obtain a chrome-nickel-containing stainless steel mother liquor, wherein the contents of Fe, Cr and Ni in the stainless steel mother liquor are 81.90%, 12.23% and 1.09%, and the recovery rates are 84.72%, 60.12% and 87.93%. And melting and separating to be used as stainless steel mother liquor.

Example 6

A method for strengthening gas-based solid reduction of chromite specifically comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: drying the laterite-nickel ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite (30: 30: 40) is mixed with 6.9 wt% of quicklime to obtain a mixed material with binary alkalinity of 0.6.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 14%, and the pelletizing time is 14min, so that green pellets are obtained. The falling strength of the green pellets is more than 20 times/0.5 m, the compressive strength is 23N/green pellets, and the bursting temperature is 531 ℃.

(5) Oxidizing and roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min; the roasting temperature is 1230 ℃, and the roasting time is 12 min; the soaking temperature is 900 ℃, the soaking time is 5min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 2257N/pellet.

(6) Pre-reduction: putting the chromium-containing nickel iron ore oxidized pellets prepared in the step (5) into a reduction furnace, and reducing the pellets for 60min at a reduction gas flow rate of 800Nl/H and a reduction temperature of 950 ℃ and a reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromium-containing nickel iron ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 70.21 percent, and the compressive strength of the pellets is 999N/pellet.

7) Melting and separating: and (3) uniformly mixing the chrome-containing nickel iron ore pre-reduced pellets prepared in the step (6) with coke accounting for 5 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for melting at 1450 ℃, for 120min, wherein the binary basicity of the slag is 0.7, so as to obtain a chrome-nickel-containing stainless steel mother liquor, wherein the contents of Fe, Cr and Ni in the stainless steel mother liquor are 81.90%, 12.23% and 1.09%, and the recovery rates are 84.72%, 60.12% and 87.93%. And melting and separating to be used as stainless steel mother liquor.

Example 7

The method for preparing the stainless steel mother liquor by using the chromium-containing nickel iron ore pellets comprises the following steps:

(1) pre-treating chromite: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pretreating the laterite nickel ore: mixing red earth nickelDrying the ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(3) Preparing materials: mixing magnetite with pretreated chromite and laterite-nickel ore, wherein the ore blending proportion is that of chromite: laterite-nickel ore: magnetite (30: 30: 40) is mixed with 11.6 wt% of quicklime to obtain a mixed material with binary alkalinity of 1.0.

(4) Pelletizing: pelletizing the mixed material by using a disc pelletizer, wherein the pelletizing water content is 14%, and the pelletizing time is 14min, so that green pellets are obtained. The falling strength of the green pellets is more than 20 times per 0.5m, the compressive strength is 19.6N per pellet, and the bursting temperature is 405 ℃.

(5) Oxidizing and roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min; the roasting temperature is 1230 ℃, and the roasting time is 12 min; the soaking temperature is 900 ℃, the soaking time is 5min, the chromium-containing nickel iron ore oxidized pellets are obtained, and the compressive strength reaches 1991N/pellet.

(6) Melting and separating: and (3) uniformly mixing the chromium-containing nickel-iron ore oxidized pellets prepared in the step (5) with coke accounting for 10 wt% of the pellets, putting the mixture into a high-temperature smelting furnace for smelting at 1600 ℃, wherein the smelting time is 120min, the binary basicity of the slag is 0.6, so as to obtain a chromium-nickel-containing stainless steel mother liquor, the contents of Fe, Cr and Ni in the obtained stainless steel mother liquor are 85.97%, 6.69% and 0.95%, and the recovery rates are 73.41%, 25.49% and 56.71%, respectively. And melting and separating to be used as stainless steel mother liquor.

Comparative example 1

A preparation method of laterite-nickel ore oxidized pellets comprises the following steps:

(1) pretreating the laterite nickel ore: drying the laterite-nickel ore to the moisture content of below 10%, crushing the laterite-nickel ore to the moisture content of below 3mm by using a double-roll crusher, and then grinding the laterite-nickel ore to the particle size of more than 75% and less than 0.074mm by using a rod mill, wherein the specific surface area is not less than 1800cm²And/g, obtaining the pretreated laterite nickel ore.

(2) Pelletizing: pelletizing the pretreated laterite-nickel ore by using a disc pelletizer, wherein the pelletizing water content is 29%, and the pelletizing time is 14min, so that green pellets are obtained. The falling strength of green pellets is more than 20 times per 0.5m, the compressive strength is 11.5N per green pellet, and the bursting temperature is more than 600 ℃.

(3) Roasting: carrying out oxidizing roasting on the dried pellets on a belt roasting machine, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min; the roasting temperature is 1230 ℃, and the roasting time is 10 min; soaking temperature is 950 ℃, soaking time is 7min, and the laterite-nickel ore oxidized pellets are obtained, wherein the compressive strength is 579N/pellet.

(4) Pre-reduction: putting the chromite oxidized pellets prepared in the step (3) into a reduction furnace, and reducing for 60min at the reduction gas flow rate of 800Nl/H and the reduction temperature of 950 ℃ and the reduction gas volume ratio of H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the chromite pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 9.85 percent, and the compressive strength of the pellets is 269N/pellet.

Comparative example 2

(1) Pretreatment of raw materials: adding 22.61% of iron and Cr₂O₃42.55 percent of chromite concentrate is ball milled in a wet way until the grain diameter of more than 90 percent of particles in the chromite is less than 0.074mm and the specific surface area is not less than 1500cm²And/g, obtaining the pretreated chromite.

(2) Pelletizing: and (3) adding 1.6% of bentonite into the chromite material prepared in the step (1) by using a disc pelletizer for pelletizing, wherein the pelletizing water content is 13%, and the pelletizing time is 14min, so as to obtain the chromite green pellets. The falling strength of the green pellets is 7.1 times/0.5 m, the compressive strength is 15.2N/green pellets, and the bursting temperature is more than 390 ℃.

(3) Oxidizing and roasting: placing the green balls prepared in the step (2) into a belt type roasting machine for roasting, wherein the preheating temperature is 950 ℃, and the preheating time is 10 min; the roasting temperature is 1320 ℃, and the roasting time is 12 min; the soaking temperature is 900 ℃, and the soaking time is 5min, so as to obtain the chromite oxidized pellets. The compressive strength was 1300N/piece.

(4) Pre-reduction: putting the laterite nickel ore oxidized pellets prepared in the step (3) into a reduction furnace, and reducing at the reduction temperature of 950 ℃ for a reduction time at a reduction gas flow rate of 800Nl/h60min, volume ratio of reducing gas H₂/(H₂And (3) carrying out gas-based solid reduction reaction under the condition that the content of CO is 0.25 to obtain the laterite-nickel ore pre-reduced pellets, wherein the iron metallization rate of the obtained pre-reduced pellets is 53.55%, and the compressive strength of the pellets is 451N/pellet.

Analysis of the data obtained in the above examples shows that the iron metallization rate of the chromium-containing ferronickel ore pre-reduced pellet with basicity of 1.0 is 80.41%, and the compressive strength reaches 994N/pellet. Compared with the corresponding data of the comparative example 1 and the comparative example 2, the method of the invention can effectively strengthen the reduction of iron oxide in chromite and laterite-nickel ore and greatly improve the compressive strength of the pre-reduced pellets.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.