WO2017076080A1 - Reduction roasting method for iron ore - Google Patents

Abstract

A reduction roasting method for iron ore, which provides an approach in which twice reduction roasting is carried out on low-grade difficultly-selected iron ore such as red soil josephinite and iron-aluminum-silicon associated ore by means of a shaft kiln and a rotary kiln, and reduced iron with low cost is directly produced, and the low-grade difficultly-selected iron ore is comprehensively utilized. In the method, coal carbon is directly used as a fuel and a reducing agent, and coke and coal gas are not needed; aluminum oxide is easily and economically extracted; a main component of tailings is calcium silicate, and the tailings can be directly used; no solid waste is produced. By means of the method, low-grade difficultly-selected iron ore is comprehensively utilized, and economic value is high.

Description

 Iron ore reduction roasting method

 Technical field

 The invention relates to an iron ore reduction roasting method, in particular to a method for two-step reduction roasting of iron ore.

 Background technique

Iron ore is mainly ferrite. In the process of iron roasting, the main reaction is the process of Fe ₂ O ₃ +3CO passing through high temperature -2Fe + 3CO ₂ . The basic principle of this process has long been common knowledge in the industry.

China's iron ore reserves are large, but they are basically low-grade lean ore, showing the characteristics of poverty, fineness and miscellaneous, and the proportion of complex and difficult mineral resources is large. Under normal circumstances, these poor ore can not directly enter the production process as the raw material of iron; coupled with the low level of domestically developed and comprehensive utilization technology, the production process and equipment are relatively backward, resulting in lower concentrate grade and recovery rate. It is difficult to meet the production requirements of low-cost smelting. To use these lean mines, it is usually necessary to enrich and upgrade the lean ore. Methods for upgrading low grade ore are generally: magnetic separation, flotation, reverse flotation, magnetic separation after magnetic roasting, and direct reduction.

For the magnetic separation method, since the magnetic properties of hematite and limonite are very weak, even high-strength magnetism can only make 3 to 4 grades of low-grade iron ore. Flotation, reverse flotation, this method has a small scope of application and can only be used for the sorting of a small portion of hematite and limonite. At present, the application of magnetization roasting-magnetic separation is more widely used. This method can improve the grade of iron ore with lower grade than other kinds of iron ore. ~ 12 Taste. It is now basically a rotary kiln for magnetizing roasting. However, the existing rotary kiln roasting low-grade ore has problems such as uneven reduction, high roasting cost, and abnormal production of the rotary kiln ring.

 Summary of the invention

 The problem solved by the present invention is to provide a low-grade refractory iron ore such as laterite ilmenite, iron-aluminum-silicon associated ore, etc. through vertical kiln and rotary kiln. The method of reducing roasting by two methods, directly producing reduced iron (nickel iron) at a low cost, and realizing comprehensive utilization of low-grade refractory iron ore (iron-aluminum-silicon associated ore).

 The present invention solves this problem by providing an iron ore reduction roasting method.

 The present invention shows an iron ore reduction roasting process based on a conventional shaft kiln and rotary kiln or ZL2014 2 which has been authorized by the present inventors. Published in 0044504.9 The mixing kiln comprises a rotary kiln and a vertical kiln. The upper part of the vertical kiln is provided with a flue. The lower part of the vertical kiln is connected with a material transfer passage. One end of the material transfer passage is connected with the lower part of the vertical kiln, and the other end is connected with the rotary kiln. The tail end is connected, the top of the vertical kiln is provided with a feeding port, and the head end of the rotary kiln is provided with a discharging port;

 The iron ore reduction roasting method is a two-step roasting method,

 Step 1, ingredients,

 The iron ore and auxiliary materials are balanced by ternary ratio SiO 2 , CaO, MgO and mixed with the broken coal to obtain a mixture;

 Step 2, roast,

 The mixture completed in step 1 enters the vertical kiln and is preheated, calcined and cooled after the conventional process, and is discharged after being calcined, and then discharged into the rotary kiln;

 Step 3, after the crushed iron ore mixture in the vertical kiln is crushed and directly sent to the rotary kiln or the rotary kiln end connected with the vertical kiln;

 Step 4, the rotary kiln is a conventional reducing atmosphere, and the furnace material after the completion of the reduction process can be discharged;

 In step 5, high-grade reduced iron and tailings can be obtained after crushing, ball milling and magnetic separation of the iron ore mixture after two calcination.

Wherein, the iron ore and the auxiliary material limestone or dolomite are balanced according to SiO ₂ , CaO and MgO. The iron ore is broken into 3 to 50 mm of iron ore, and the auxiliary limestone or dolomite is broken into 3 to 50 mm of auxiliary materials (allowing a small amount of iron ore and auxiliary materials of less than 3 mm).

In detail, in step 1, the surface water of the iron ore and the crystal water are evaporated in the preheating zone, and then calcined in a high temperature zone of 900-1000 ° C for 0.5 to 1.5 hours to decompose the limestone into calcium oxide CaO + CO ₂ . And some SiO ₂ +CaO=CaSiO ₃ , after the molten fly ash and calcium oxide are solidified, enter the cooling zone and cool down at 900 to 300 ° C for about 2 to 4 hours, and then crushed and sent to the rotary kiln. In step 4, the temperature in the reduction zone of the rotary kiln is 1150～1250°C, and the reduction time is 1-2 hours; when the furnace is discharged, the water discharge structure is adopted at the discharge port of the rotary kiln head end, and the furnace material is directly discharged into the water to avoid reoxidation. . These process parameters are either prior art or conventional techniques.

 Further, the iron ore is an iron-aluminum-silicon associated ore, a laterite-bearing ilmenite or a general iron ore. Also includes step 6, tail The ore (iron-aluminum-silicon associated ore) is reused by caustic soda leaching to select alumina in the iron-aluminum associated ore.

In the roasting process, the high coal can be calculated according to the amount of blast air, and the burning speed of the different constituent components of the coal is different, and the volatile matter is burned as much as possible to retain the carbon. The carbon particles and the iron ore mixture are fused together.

 Compared with the prior art, the biggest difference between the present invention is that it is poor. The iron ore reduction roasting method employs a so-called two-step roasting method. The advantages of this method are:

 1. Direct use of coal as fuel and reducing agent, without coke and coal gas;

 2, easy and economical extraction of alumina (iron-aluminum-silicon associated ore);

 3, the main component of tailings is calcium silicate can be directly used;

 4, no solid waste;

 5. The economic value is extremely high due to the comprehensive utilization of low-grade refractory iron ore.

 In summary, the present invention solves the problem that the low-grade refractory iron ore, such as iron-aluminum-silicon associated ore, cannot be applied for decades.

 Detailed ways

 The invention is based on the realization that a large amount of iron ore in China is difficult to use and has low utilization rate. Based on the existing mineral processing technology, a method is proposed. Iron ore reduction roasting method. The method is based on a conventional vertical kiln and a rotary kiln, or is disclosed in the patent of ZL2014 2 0044504.9, which is hereby incorporated by reference. The mixing kiln comprises a rotary kiln and a vertical kiln. The upper part of the vertical kiln is provided with a flue. The lower part of the vertical kiln is connected with a material transfer passage. One end of the material transfer passage is connected with the lower part of the vertical kiln, and the other end is connected with the rotary kiln. The tail end is connected, the top of the vertical kiln is provided with a feeding port, and the head end of the rotary kiln is provided with a discharging port;

 The iron ore reduction roasting method is a two-step roasting method:

Step 1, ingredients, iron ore (broken into 3 ~ 50mm) and auxiliary materials (limestone or dolomite) (broken into 3 ~ 30mm) according to the ternary ratio (SiO2, CaO, MgO Balance and mix with the broken coal (allow to mix a small amount of iron ore and accessories below 3mm).

Step 2, roasting, the mixture enters the vertical kiln roasting, through the preheating zone: the surface water of the iron ore and the crystal water evaporate; the temperature of the high temperature zone is 900-1000 ° C, 0.5-1.5 hours, and the limestone is decomposed into CaO+CO 2 , And some SiO2+CaO=CaSiO3, the molten fly ash and calcium oxide are solidified, and the cooling zone is 900~300°C for about 2~4 hours, which is broken and discharged.

In the roasting process, the coal can be calculated according to the amount of blast air, and the burning speed of different components of the coal is different, and the volatile matter is burned as much as possible to retain the carbon. Melting the carbonaceous granules with the iron ore mixture;

 Step 3, the roasting iron ore mixture in the vertical kiln is directly sent to the rotary kiln or sent to the end of the rotary kiln connected with the vertical kiln;

In step 4, the rotary kiln is in a reducing atmosphere, the temperature in the reduction zone of the rotary kiln is 1150 to 1250 ° C, and the reduction time is 1-2 hours, and the charge after the completion of the reduction process can be discharged; the release process must be ensured not to be reoxidized. The reducing atmosphere is conventionally a CO atmosphere.

Step 5, after crushing, ball milling, magnetic separation and conventional beneficiation of the twice calcined iron ore mixture, high grade reduced iron (nickel iron, roasting ilmenite) and tailings are obtained;

 Step 6 For the tailings to be reused by caustic soda leaching, alumina (for iron-aluminum-silicon associated ore) may be selected.

In the practice of the present invention, low-grade iron ore and fuel (reducing agent, single coal or mixed coal) are mixed with low-grade iron ore and dolomite or limestone added as needed, and are fed into the shaft kiln through the feed port. . The material is first heated in the combustion chamber of the shaft kiln, the iron ore is heated by high temperature, the surface water and the crystal water are evaporated, and primary reduction is started, and the original phase structure of the iron ore is destroyed in the high temperature region, which helps the subsequent reduction. And mineral processing. When the iron ore in the shaft kiln passes through the tuyere of the inlet duct, the temperature drops sharply. The iron ore then falls into the material transfer channel and enters the rotary kiln. Since the iron ore entering the rotary kiln still has a higher temperature heat, and the mineral (the mixture of ore and fuel) also contains a considerable amount of reducing agent (determined by the heat balance equation), it is beneficial to the rotary kiln. Deep restore. In the rotary kiln, it is heated more evenly, maintaining 1150~1250 degrees and high reducing atmosphere for more than 50 minutes, so that the mineral can be fully reduced. (The heating process of the rotary kiln is a common knowledge and will not be described in detail here). The exhaust gas generated in the rotary kiln contains higher temperature heat and reducing gas and dust, and then enters the vertical kiln, which has a recycling effect on the part and saves resources. In addition, due to the lower temperature selected, the alumina in the tailings is not damaged by high temperature, and the tailings can be further comprehensively utilized.

The above-described embodiments are merely illustrative of one embodiment of the present invention. Since the composition of iron ore varies widely, it is not possible to make an extensive review. Therefore, the above embodiments are not to be construed as limiting the scope of the invention. It will be apparent to those skilled in the art that many variations and modifications can be made without departing from the spirit of the two-step roasting method of the present invention, which are within the scope of the present invention, that is, the scope of protection of the present invention should be The request is subject to change.

Claims (7)

 Iron ore reduction roasting method based on traditional vertical kiln and rotary kiln or The mixing kiln includes a vertical kiln and a rotary kiln. The upper part of the vertical kiln is provided with a flue. The lower part of the vertical kiln is connected with a material transfer passage. One end of the material transfer passage is connected with the lower part of the vertical kiln, and the other end is connected with the rotary kiln. The tail end is connected, the top of the vertical kiln is provided with a feeding port, and the head end of the rotary kiln is provided with a discharging port; The iron ore reduction roasting method is a two-step roasting method, Step 1, ingredients, The iron ore and auxiliary materials are balanced by ternary ratio SiO 2 , CaO, MgO and mixed with the broken coal to obtain a mixture; Step 2, roast, The mixture completed in step 1 enters the vertical kiln and is preheated, calcined and cooled after the conventional process, and is discharged after being calcined, and then discharged into the rotary kiln; Step 3, after the crushed iron ore mixture in the vertical kiln is crushed and directly sent to the rotary kiln or the rotary kiln end connected with the vertical kiln; Step 4, the rotary kiln is a conventional reducing atmosphere, and the charge obtained after the completion of the reduction process can be discharged; In step 5, high-grade reduced iron and tailings can be obtained after conventionally beneficiating the crushed, ball-milled and magnetically selected calcined materials. The iron ore reduction roasting method according to claim 1, characterized in that the iron ore and the auxiliary material limestone or dolomite are equilibrated with SiO ₂ , CaO and MgO. An iron ore reduction roasting method according to claim 2, characterized in that said The iron ore is broken into 3~50mm iron ore, and the auxiliary material limestone or dolomite is broken into 3~30mm auxiliary materials. The iron ore reduction roasting method according to claim 1 or 2 or 3, wherein in the step 1, the surface water of the iron ore and the crystal water are evaporated by the preheating zone, and the temperature is at a temperature of 900 to 1000 ° C. The zone is calcined for 0.5 to 1.5 hours to decompose the limestone into calcium oxide CaO+CO ₂ and partially SiO ₂ +CaO=CaSiO ₃ , so that the molten fly ash and calcium oxide are solidified and then enter the cooling zone for 900 to 300 ° C. The temperature is lowered, and the length is about 2 to 4 hours, and then it is crushed and sent to the rotary kiln. The iron ore reduction roasting method according to claim 4, wherein in step 4, The temperature in the reduction zone of the rotary kiln is 1150~1250 °C, and the reduction time is 1-2 hours; when it is discharged, it is located The water discharge structure is adopted at the discharge port of the rotary kiln head end, and the furnace material is directly discharged into the water after the furnace is discharged to avoid reoxidation. The iron ore reduction roasting method according to claim 1 or 2 or 3, wherein the iron ore is an iron-aluminum-silicon associated ore or red earth Reduction roasting of ilmenite or general iron ore. The iron ore reduction roasting method according to claim 6, characterized in that it further comprises the step 6 of the iron-aluminum associated tail The ore is further subjected to a caustic soda leaching method to select alumina in the iron-aluminum associated ore.