Energy-saving and environment-friendly low-grade iron ore and tailing one-step pig iron forming process

Abstract

The invention provides an energy-saving and environment-friendly low-grade iron ore and tailing one-step pig iron forming process. The process comprises the following steps: (1) crushing raw materials until the particle size is 1-3cm; (2) drying the crushed raw materials, and crushing the dried raw materials to 200 meshes; (3) adding a certain proportion of calcium carbonate and sodium carbonate into the crushed raw materials, and mixing; and (4) a 35-kilowatt high-frequency machine is used for providing a heat source to roast the mixed material obtained in the step (3), and pig iron and slag are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to an energy-saving and environment-friendly process for producing pig iron from low-grade iron ore and tailings in one step. Background Art

[0002] Iron ore is an important raw material for steel production enterprises. Natural ore (iron ore) is gradually selected from iron through crushing, grinding, magnetic separation, flotation, gravity separation and other procedures. Iron ore is a mineral aggregate containing iron or iron compounds that can be economically utilized. The world's iron ore resources are concentrated in Australia, Brazil, Russia, Ukraine, Kazakhstan, India, the United States, Canada, South Africa and other countries. As the world's largest iron ore demander, China has a considerable amount of iron ore reserves. They are distributed south of the Yellow River and south of the Yangtze River. There are more than 10 million tons of low-grade iron ore around Dianchi Lake in Yunnan. Among them, ferric oxide and ferric oxide contain 20%-35% iron, but generally contain high phosphorus and sulfur. However, because of the low grade, most of them are imported from Australia, Brazil and other countries rich in iron ore. Large domestic factories use graphite as electrodes, which requires ore with good conductivity to smelt, but most of the low-grade ores (iron content 20%-35%) in China are not conductive, so they need to import high-grade iron ore into the furnace. At the same time, using a large furnace will cool the core and the graphite electrode will not work. Therefore, it is urgent to develop a new process to recycle these low-grade iron ore and tailings. Summary of the invention

[0003] The purpose of the present invention is to provide a one-step process for producing pig iron with short process, low energy consumption, energy saving and environmental protection for low-grade and difficult-to-process iron ore and tailings.

[0004] The object of the present invention is achieved by providing an energy-saving and environmentally friendly oxygen-sulfur mixed lead-zinc ore slurry electrolysis process, comprising the following steps: (1) Crushing the raw materials into particles with a size of 1-3 cm; (2) Dry the crushed raw materials and then crush them into 200 mesh; (3) Add a certain proportion of calcium carbonate and sodium carbonate to the crushed raw materials and mix them; (4) A 35 kW high frequency machine is used as a heat source to roast the mixture obtained in step (3) to obtain pig iron and slag.

[0005] Compared with the prior art, the present invention has the following beneficial effects: 1. This process has short flow, low energy consumption, energy saving and environmental protection.

[0006] 2. This process does not use petrochemical raw materials, but only uses electricity as a heat source, and uses small-diameter and high-purity graphite tubes for heating, so there will be no cold core phenomenon. The material falls from the top and the iron and slag are discharged from the bottom, which greatly reduces the energy consumption and cost of the enterprise. DETAILED DESCRIPTION

[0007] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0008] An energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings, comprising the following steps: (1) Crushing the raw materials into particles with a size of 1-3 cm; (2) Dry the crushed raw materials and then crush them into 200 mesh; (3) Add a certain proportion of calcium carbonate and sodium carbonate to the crushed raw materials and mix them; (4) A 35 kW high frequency machine is used as a heat source to roast the mixture obtained in step (3) to obtain pig iron and slag.

[0009] The crushing in step (1) is specifically as follows: the first crushing is coarse crushing until the raw material particle size reaches 5-10 cm, the second crushing is medium crushing until the raw material particle size reaches 2-6 cm, and the third crushing is fine crushing until the raw material particle size reaches 1-3 cm.

[0010] The moisture content of the raw material after drying in step (2) is reduced from 10-15% to less than 7%.

[0011] The amount of calcium carbonate and sodium carbonate added in step (3) is calcium carbonate: sodium carbonate: raw material in a mass ratio of 5-6:1:25.

[0012] The heating element of the high-frequency machine in step (4) is a high-purity graphite tube, which is covered with heat-resistant material. The high-purity graphite tube is divided into two sections, the upper section is a conical tube with a height of 600mm, an outer diameter of 80mm and an inner diameter of 40mm at the receiving port, and an outer diameter of 220mm and an inner diameter of 180mm at the unloading port; the lower section is a circular straight tube with a height of 900mm, an outer diameter of 80mm and an inner diameter of 40mm; there is a pig iron and slag outlet at the bottom of the circular straight tube, which is made of silicon carbon sheets, and the pig iron and slag outlets have an outer diameter of 60mm, a thickness of 10mm and an inner diameter of 12mm.

[0013] The smoke generated in step (4) is sent to the acid-alkali resistant cylinder of the water-cooling jacket to recover sulfur and phosphorus respectively.

[0014] The pig iron and slag obtained in step (4) are cooled, crushed by a collider, and then separated by magnetic separation; the pig iron is microwave dried and then cast into pig iron ingots in a medium frequency furnace.

[0015] Example 1 50 kg of limonite is ground to 200 mesh (accounting for 80%) by Raymond mill after coarse, medium and fine crushing, and then 12.5 kg of calcium carbonate and 2.5 kg of sodium carbonate are added and mixed by a mixer, and then roasted by a 35 kW high frequency machine to obtain pig iron and slag. The smoke generated during the roasting process is sent to the acid and alkali resistant cylinder of the water cooling jacket to recover sulfur and phosphorus according to the huge difference in the melting points of sulfur and phosphorus, and other impurities are removed after being turned into slag. After the pig iron and slag are cooled, they are crushed by a collider and magnetic separation is performed to separate the pig iron and slag; the pig iron is microwave dried and then the pig iron ingot is cast in a medium frequency furnace.

[0016] In this Example 1, the TFe content in the limonite is 30%, the S content is 2.48%, and the P content is 0.104%.

[0017] This process can extract 1 ton of pig iron from about 3.5 tons of ore, with a recovery rate of about 90%. The total cost of domestic ore is about 1,500 yuan per ton of pig iron. The total cost of purchasing high-grade iron ore from abroad is about 2,500 yuan per ton of pig iron. This process solves the problem of a large number of poor ore in China and brings considerable profits to enterprises.

[0018] Example 2 50 kg of tailings are ground to 160 mesh (accounting for 80%) by Raymond mill, and then 15 kg of calcium carbonate and 2.5 kg of sodium carbonate are added and mixed by a mixer, and then roasted by a 35 kW high-frequency machine to provide heat source to obtain pig iron and slag. The smoke generated during the roasting process is sent to the acid-alkali resistant cylinder of the water-cooling jacket to recover sulfur and phosphorus respectively, and other impurities are removed after becoming slag. After the pig iron and slag are cooled, they are crushed by a collider and magnetic separation is performed to separate the pig iron and slag; the pig iron is dried by microwave and then cast in a medium-frequency furnace.

[0019] The iron content of the tailings in this embodiment is 28%. After being treated by this process, 13 kg of pig iron is extracted, and the extraction rate is 92%.

Claims

1. An energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings, characterized in that The following steps are involved: (1) Crushing the raw materials into particles with a size of 1-3 cm; (2) Dry the crushed raw materials and then crush them into 200 mesh; (3) Add a certain proportion of calcium carbonate and sodium carbonate to the crushed raw materials and mix them; (4) A 35 kW high frequency machine is used as a heat source to roast the mixture obtained in step (3) to obtain pig iron and slag.

2. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1 is characterized in that The crushing in step (1) is specifically as follows: the first crushing is coarse crushing until the raw material particle size reaches 5-10 cm, the second crushing is medium crushing until the raw material particle size reaches 2-6 cm, and the third crushing is fine crushing until the raw material particle size reaches 1-3 cm.

3. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1 is characterized in that The moisture content of the raw material after drying in step (2) is reduced from 10-15% to less than 7%.

4. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1 is characterized in that The amount of calcium carbonate and sodium carbonate added in step (3) is calcium carbonate: sodium carbonate: raw material in a mass ratio of 5-6:1:

25.

5. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1 is characterized in that The heating element of the high-frequency machine in step (4) is a high-purity graphite tube, which is covered with heat-resistant material. The high-purity graphite tube is divided into two sections, the upper section is a conical tube with a height of 600mm, an outer diameter of 80mm and an inner diameter of 40mm at the receiving port, and an outer diameter of 220mm and an inner diameter of 180mm at the unloading port; the lower section is a circular straight tube with a height of 900mm, an outer diameter of 80mm and an inner diameter of 40mm; there is a pig iron and slag outlet at the bottom of the circular straight tube, which is made of silicon carbon sheets, and the pig iron and slag outlets have an outer diameter of 60mm, a thickness of 10mm and an inner diameter of 12mm.

6. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1, characterized in that The smoke generated in step (4) is sent to the acid-alkali resistant cylinder of the water-cooling jacket to recover sulfur and phosphorus respectively.

7. The energy-saving and environmentally friendly one-step process for producing pig iron from low-grade iron ore and tailings according to claim 1 is characterized in that The pig iron and slag obtained in step (4) are cooled, crushed by a collider, and then separated by magnetic separation; the pig iron is microwave dried and then cast into pig iron ingots in a medium frequency furnace.