Use method of additive for strengthening chromite pellet consolidation
By adding an appropriate amount of borax or borax mud to chromite pellets and then drying, preheating, and roasting them, the problem of low strength in chromite pellets was solved, improving chromite smelting efficiency and mechanical strength, and achieving high-efficiency and low-cost production of high-carbon chromite.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-28
- Publication Date
- 2026-03-10
AI Technical Summary
Poor particle bonding during chromite pellet preparation results in high processing temperatures and low pellet strength, which affects the efficiency of high-carbon ferrochrome smelting and the development of the stainless steel industry.
Boron-containing substances such as borax or borax mud are used as additives to control their proportion and particle size in chromite pellets. Drying, preheating and roasting processes are used to enhance the bonding between particles and generate a low-melting-point liquid phase to enhance the consolidation strength.
This improved the mechanical strength of ferrochrome pellets, lowered the preparation temperature, and enabled efficient and low-cost high-carbon ferrochrome smelting, thus promoting the healthy development of the stainless steel industry.
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of ferrochrome smelting, and particularly relates to a ferrochrome pellet consolidation strengthening additive and a use method thereof. BACKGROUND
[0002] High-carbon ferrochrome is a main alloy additive for producing stainless steel and is mainly produced by an electric furnace method. The high-carbon ferrochrome production process has high requirements for the permeability, melting speed and reducibility of the furnace charge, and the performance of the furnace charge is one of the key factors affecting the smelting effect.
[0003] At present, the electric furnace smelting furnace charge is mainly artificial ferrochrome lump ore after briquetting. Using low-cost ferrochrome ore powder to prepare high-quality high-carbon ferrochrome smelting furnace charge by sintering and pelletizing is one of the important development directions of the electric furnace method for efficiently and energy-saving producing high-carbon ferrochrome. At present, the main preparation technology of ferrochrome smelting furnace charge for industrialized large-scale application is the pelletizing method, but due to the high melting point of chromium compounds, it is difficult to produce low-melting-point liquid phase during the preparation of the furnace charge, the consolidation between particles is weak, which leads to problems such as high processing temperature and low mechanical strength of the furnace charge during the preparation of the ferrochrome furnace charge.
[0004] In general, the preparation process of the furnace charge in the current ferrochrome smelting has problems such as high processing temperature and low mechanical strength of the furnace charge caused by poor particle bonding ability during the preparation process. If the difficult boron mud is treated and used as an additive to enhance the consolidation of the ferrochrome smelting furnace charge, it will help to solve the above problems.
[0005] The purpose of the present application is to provide an additive for strengthening the consolidation of ferrochrome pellets, which solves the problems of high processing temperature and low pellet strength caused by poor particle bonding ability during the preparation of ferrochrome pellets, and has important significance for realizing low-carbon efficient smelting of high-carbon ferrochrome and ensuring the healthy development of the stainless steel industry. SUMMARY
[0006] In view of the problems of high processing temperature and low pellet strength caused by poor particle bonding ability during the preparation of ferrochrome pellets, the purpose of the present application is to provide an additive for strengthening the consolidation of ferrochrome pellets.
[0007] To achieve the above purpose, the present application provides a use method of an additive for strengthening the consolidation of ferrochrome pellets, comprising the following steps:
[0008] S1: adding a boron-containing substance to the ferrochrome pellet mixture according to the required proportion, fully mixing, and pelletizing the mixed ore to obtain ferrochrome pellets; the boron-containing substance is selected from at least one of borax, boron mud and the like; the proportion of the boron-containing substance in the ferrochrome pellets is 0.1-5wt%;
[0009] S2: drying, preheating and roasting the green pellets to obtain ferrochrome pellets.
[0010] Furthermore, in S1, the proportion of boron-containing substances in the chromite pellets is 1-3 wt%, more preferably 1.5-3 wt%.
[0011] Furthermore, in S1, the particle size of additives such as borax and borax mud is controlled to be ≥90% of -0.074mm.
[0012] Furthermore, the boron-containing material used in S1 is in the mass ratio of borax:borax mud = 1:(1-10).
[0013] Furthermore, in S1, the chromite pellets include at least one of the following: chromite oxide pellets, chromite pre-reduced pellets, chromite flux oxide pellets, and chromite flux pre-reduced pellets.
[0014] Furthermore, in S1, the diameter of the green pellet is 8-20 mm.
[0015] Furthermore, in S2, the drying process is as follows: for oxidized pellets, the drying temperature is 200-300℃ and the time is 2-15 min; for pre-reduced pellets, the drying temperature is 200-350℃ and the time is 2-10 min.
[0016] Furthermore, in S2, the preheating process is as follows: for oxidized pellets, the preheating temperature is 700–1000℃ and the time is 2–20 min; for pre-reduced pellets, the preheating temperature is 800–1100℃ and the time is 4–15 min.
[0017] Furthermore, in S2, the roasting process is as follows: the roasting temperature for oxidized pellets is 700–1200℃, and the time is 2–20 min; the roasting temperature for pre-reduced pellets is 900–1300℃, and the time is 30–95 min.
[0018] Furthermore, in S2, the compressive strength of oxidized pellets in the preheated chromite pellets is ≥500 N / P, and the compressive strength of pre-reduced pellets is ≥400 N; the compressive strength of oxidized pellets in the roasted pellets is ≥2200 N / P, and the compressive strength of pre-reduced pellets is ≥2000 N / P.
[0019] As a preferred embodiment, the present invention provides a method for using an additive to enhance the consolidation of chromite pellets.
[0020] The chromite particle size used in S1 is controlled to be ≥80% of -0.074mm; the chromite pellets contain 1.4-1.6wt% bentonite and / or 4-6wt% silica; the obtained chromite pellets contain 2.8-3.2wt% additives; the additives are composed of borax and borax mud in a mass ratio of borax:borax mud = 1:(1-4).
[0021] The resulting green pellets of chromite have a particle size of 14-16 mm;
[0022] The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 280-320℃, and the time is 10-15 min; the preheating temperature is 700-900℃, and the preheating time is 6-10 min to obtain preheated oxidized pellets; the roasting temperature is 1180-1220℃, and the roasting time is 7-9 min.
[0023] As a preferred embodiment, the present invention provides a method for using an additive to enhance the consolidation of chromite pellets.
[0024] The chromite particle size used in S1 is controlled to be ≥80% of -0.074mm; the chromite pellets contain 1.4-1.6wt% bentonite and / or 8-12wt% carbonaceous reducing agent; the obtained chromite pellets contain 2.8-3.2wt% additives; the additives are composed of borax and borax mud in a mass ratio of borax:borax mud = 1:(1-4).
[0025] The resulting green pellets of chromite have a particle size of 14-16 mm;
[0026] The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 240-260℃, and the time is 8-15 min; the preheating temperature is 1050-1150℃, and the preheating time is 8-12 min to obtain preheated oxidized pellets; the roasting temperature is 1280-1320℃, and the roasting time is 85-95 min.
[0027] The advantages of this invention are:
[0028] An additive for enhancing the consolidation of ferrochrome pellets was developed from boron industrial waste slag, which was difficult to utilize. By selecting appropriate proportions of borax and boron mud and controlling their total amount, the additive reacts with chromium-containing components during the high-temperature heat treatment of the furnace charge preparation process to generate an appropriate amount of low-melting-point liquid phase. This enhances the interparticle bonding and improves the consolidation strength of the pellets. This additive has a wide range of sources and simultaneously achieves efficient recycling of boron smelting slag. The resulting ferrochrome smelting furnace charge meets smelting requirements while improving mechanical strength, contributing to the efficient, low-carbon, and low-cost smelting of high-carbon ferrochrome from chromite ore. Detailed Implementation
[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0030] This invention relates to an additive for strengthening the consolidation of chromite pellets, and the effect of the binder is illustrated in the following specific embodiments.
[0031] Example 1
[0032] Chromite with a particle size controlled at -0.074mm ≥ 80%, and bentonite with a ratio of 1.5wt%, is mixed with 1.5wt% additives (borax:boron mud = 1:4, with borax and boron mud particle sizes controlled at -0.074mm ≥ 90%). The chromite, bentonite, additives, and water are thoroughly mixed (water content is 7%). The mixed ore is then pelletized to obtain green chromite pellets (particle size 14-16mm). The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 300℃ for 12 minutes; the preheating temperature is 700℃ for 8 minutes, resulting in a preheated oxide pellet compressive strength of 541 N / P; the roasting temperature is 1200℃ for 8 minutes, resulting in a finished pellet compressive strength of 2237 N / P.
[0033] Example 2
[0034] Chromite with a particle size controlled at -0.074mm ≥ 80% and bentonite with a ratio of 1.5wt%, is mixed with 3wt% additives (borax:boron mud = 1:4, with borax and boron mud particle sizes controlled at -0.074mm ≥ 90%). The chromite, bentonite, additives, and water are thoroughly mixed (water content is 7%). The mixed ore is then pelletized to obtain green chromite pellets (particle size 14-16mm). The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 300℃ for 12 minutes; the preheating temperature is 700℃ for 8 minutes, resulting in a preheated oxide pellet compressive strength of 624 N / P; the roasting temperature is 1200℃ for 8 minutes, resulting in a finished pellet compressive strength of 2460 N / P.
[0035] Example 3
[0036] Chromite particle size is controlled at -0.074mm ≥ 80%, and flux particle size is controlled at -0.074mm ≥ 80% after crushing and grinding pretreatment. Under the conditions of bentonite ratio of 1.5wt% and silica ratio of 5wt%, 3wt% of additives are added (borax:borax mud = 1:4 in the additives, and the particle size of borax and borax mud is controlled at -0.074mm ≥ 90%). The chromite, additives, flux, bentonite and water are thoroughly mixed (the amount of water is 7%). The mixed ore is pelletized to obtain chromite flux-based green pellets (green pellet particle size 14-16mm). After the prepared green pellets are dried, they are preheated and roasted to obtain finished pellets. The drying temperature is 300℃ and the time is 15 min; the preheating temperature is 900℃ and the preheating time is 8 min, and the compressive strength of the preheated oxidized pellets is 563 N / P; the calcination temperature is 1200℃ and the calcination time is 12 min, and the compressive strength of the finished pellets is 2331 N / P.
[0037] Example 4
[0038] Chromite particle size is controlled at -0.074mm ≥ 80%, flux particle size is controlled at -0.074mm ≥ 80%; under the conditions of bentonite ratio 1.5wt%, silica ratio 5wt%, and 3wt% additive (borax:boron mud = 1:6 in the additive), the chromite, additive, flux, bentonite, and water are thoroughly mixed (water content is 7%), and the mixed ore is pelletized to obtain chromite flux-based green pellets (green pellet particle size 14-16mm); the prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 300℃, and the time is 15min; the preheating temperature is 900℃, and the preheating time is 8min, resulting in a preheated oxide pellet compressive strength of 513N / P; the roasting temperature is 1200℃, and the roasting time is 12min, resulting in a finished pellet compressive strength of 2219N / P.
[0039] Example 5
[0040] Chromite particle size is controlled at -0.074mm ≥ 80%, and coke particle size is controlled at -0.074mm ≥ 80%. Under the conditions of 10% coke and 1.5wt% bentonite, 3wt% additives are added (borax:borax mud = 1:4 in the additives, and the particle size of borax and borax mud is controlled at -0.074mm ≥ 90%). The chromite, coke, additives, bentonite, and water are thoroughly mixed (the amount of water is 7%). The mixed ore is pelletized to obtain chromite pre-reduced green pellets (green pellet particle size 14-16mm). After the prepared green pellets are dried, they are preheated and roasted to obtain the finished pellet ore. The drying temperature is 250℃ and the time is 10 min; the preheating temperature is 1100℃ and the preheating time is 10 min, and the compressive strength of the preheated reduced pellets is 429 N / P; the reduction calcination temperature is 1300℃ and the calcination time is 90 min, and the compressive strength of the finished pellets is 2153 N / P.
[0041] Example 6
[0042] Other conditions were the same as in Example 2, except that: the ratio of borax to borax mud in the additives was 1:1; the compressive strength of the preheated oxidized pellets was 677 N / P; and the compressive strength of the finished pellets was 2743 N / P.
[0043] Example 7
[0044] Other conditions were the same as in Example 2, except that: the ratio of borax to borax mud in the additive was 1:10; the compressive strength of the preheated oxidized pellets was 581 N / P; and the compressive strength of the finished pellets was 2254 N / P.
[0045] Example 8
[0046] The other conditions were the same as in Example 2, except that 5 wt% of additives were added; the compressive strength of the preheated oxidized pellets was 713 N / P; and the compressive strength of the finished pellets was 2694 N / P.
[0047] Comparative Example 1
[0048] Chromite with a particle size of -0.074mm ≥ 80% and bentonite content of 1.5wt%, is thoroughly mixed with water (7% water). The mixed ore is then pelletized to obtain green chromite pellets (14-16mm particle size). The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 300℃ for 12 minutes; the preheating temperature is 700℃ for 8 minutes, and the compressive strength of the preheated oxide pellets is 407 N / P; the roasting temperature is 1200℃ for 8 minutes, and the compressive strength of the finished pellets is 1880 N / P.
[0049] Comparative Example 2
[0050] Chromite particle size is controlled at ≥80% (-0.074mm), flux (silica) particle size is controlled at ≥80% (-0.074mm), and bentonite ratio is 1.5wt% and silica ratio is 5wt%. The chromite, flux, bentonite, and water are thoroughly mixed (7% water). The mixed ore is then pelletized to obtain chromite flux-based green pellets (14-16mm particle size). The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 300℃ for 15 minutes; the preheating temperature is 900℃ for 8 minutes, resulting in preheated oxide pellets with a compressive strength of 328 N / P; the roasting temperature is 1200℃ for 12 minutes, resulting in finished pellets with a compressive strength of 1925 N / P.
[0051] Comparative Example 3
[0052] Chromite particle size is controlled at ≥80% (-0.074mm), and coke particle size is controlled at ≥80% (-0.074mm). Under conditions of 10% coke and 1.5wt% bentonite, the chromite, coke, bentonite, and water are thoroughly mixed (7% water). The mixed ore is then pelletized to obtain pre-reduced chromite green pellets (14-16mm particle size). The prepared green pellets are dried, preheated, and roasted to obtain finished pellets. The drying temperature is 250℃ for 10 minutes; the preheating temperature is 1100℃ for 10 minutes, and the resulting preheated reduced pellets have a compressive strength of 280 N / P. The reduction roasting temperature is 1300℃ for 90 minutes, and the resulting finished pellets have a compressive strength of 1813 N / P.
[0053] Comparative Example 4
[0054] The other conditions are the same as in Example 2, except that: with the addition of 10wt% additives, the resulting chromite pellets have too much impurity content, which affects the subsequent electric furnace smelting and reduces the quality of high-carbon ferrochrome products obtained from smelting.
[0055] Comparative Example 5
[0056] The other conditions were the same as in Example 2, except that: only borax was added as an additive; the compressive strength of the preheated oxidized pellets was 466 N / P; and the compressive strength of the finished pellets was 1911 N / P.
[0057] Experimental results show that the binder proposed in this invention is suitable for existing methods of preparing chromite pellets, significantly improving the strength of chromite pellets and reducing the pellet preparation process temperature. Furthermore, this binder uses widely available and low-cost raw materials.
[0058] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.
Claims
1. A method of using a strengthening chromite pellet consolidation additive, characterized by, The method comprises the following steps: (1) adding a boron-containing substance into a chromite pellet mixture according to a required proportion, mixing well, balling the mixed material, and obtaining chromite pellets; the boron-containing substance is selected from at least one of borax, boron mud, etc.; the proportion of the boron-containing substance in the chromite pellets is 0.1-5wt%; (2) drying, preheating, and roasting the green pellets to obtain chromite pellet ore.
2. A method of using a strengthening chromite pellet consolidation additive according to claim 1, characterized by: In step (1), the proportion of the boron-containing substance in the chromite pellets is 1-3wt%.
3. The method of using a fortified chromite pellet consolidation additive according to claim 1, wherein, In step (1), the particle size of the boron-containing substance is controlled to be greater than or equal to 90% of -0.074mm before use.
4. The method of using a fortified chromite pellet consolidation additive according to claim 1, wherein: In the boron-containing substance, the mass ratio of borax to boron mud is borax: boron mud = 1: (1-10).
5. The method of using a fortified chromite pellet consolidation additive according to claim 1, wherein: In step (1), the chromite pellets include at least one of chromite oxidized pellets, chromite pre-reduced pellets, chromite fluxed oxidized pellets, and chromite fluxed pre-reduced pellets.
6. A method of using a strengthening chromite pellet consolidation additive according to claim 1, characterized by: In step (1), the diameter of the green pellets is 8-20mm.
7. A method of using the enhanced chromite pellet consolidation additive according to claim 1, characterized in that: In step (2), the drying process system is as follows: the drying temperature of the oxidized pellets is 200-300℃, and the time is 2-15min; the drying temperature of the pre-reduced pellets is 200-350℃, and the time is 2-10min.
8. A method of using a strengthening chromite pellet consolidation additive according to claim 1, characterized by: In step (2), the preheating process system is as follows: the preheating temperature of the oxidized pellets is 700-1000℃, and the time is 2-20min; the preheating temperature of the pre-reduced pellets is 800-1100℃, and the time is 4-15min. In step (2), the roasting process system is as follows: the roasting temperature of the oxidized pellets is 800-1200℃, and the time is 2-20min; the roasting temperature of the pre-reduced pellets is 900-1300℃, and the time is 30-90min.
9. A method of using a strengthening chromite pellet consolidation additive according to claim 1, characterized by: In step (2), the obtained chromite preheated pellets have an oxidized pellet compressive strength greater than or equal to 500N / P and a pre-reduced pellet compressive strength greater than or equal to 400N; the roasting pellets have an oxidized pellet compressive strength greater than or equal to 2200N / P and a pre-reduced pellet compressive strength greater than or equal to 2000N / P. 10. A method of using the enhanced chromite pellet consolidation additive of claim 1, characterized by: