A process for treating ilmenite ore with solid waste pyrolysis products

Abstract

This invention relates to the field of comprehensive utilization of solid waste, specifically providing a process for treating ilmenite ore using solid waste pyrolysis products. The process involves preheating the ilmenite ore to above 1000°C with low-oxygen flue gas, then feeding it along with waste plastics, waste coke, and other raw materials into a pyrolysis reduction reactor for pyrolysis reduction. The pyrolysis of waste plastics and waste coke generates reducing gases, ensuring the device is completely in a reducing gas atmosphere. These gases react with the ilmenite ore at high temperatures to generate magnetically separable elemental iron and Fe3O4, thereby increasing the actual FeTiO3 content. Compared to existing ilmenite ore processing technologies, this method significantly increases the processing temperature, improves processing efficiency, and achieves comprehensive energy utilization.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of solid waste, and relates to a process for treating ilmenite ore using solid waste pyrolysis products. Background Technology

[0002] Ilmenite is an oxide mineral of iron and titanium, also known as titanomagnetite, and is the main ore for titanium extraction. Ilmenite is heavy, gray to black, and has a slightly metallic luster. Crystals are generally tabular, and aggregates form massive or granular forms. Its composition is FeTiO3, with a TiO2 content of 52.66%. It is the main mineral for extracting titanium and titanium dioxide. How to reduce the influence of Fe on TiO2 during the smelting process has always been a challenge in this field.

[0003] To address the aforementioned issues, the applicant filed an invention patent application in 2021 entitled "A Device for Processing Ilmenite Ore Using Solid Waste Pyrolysis Products," application number CN2021111740743, which was granted on September 13, 2022. Further research revealed that the processing of ilmenite ore from certain sources requires very high temperatures. While the aforementioned patent specifies that the pyrolysis reduction reactor can provide temperatures above 600°C, practical applications have shown difficulty in achieving temperatures above 800°C. Relying directly on existing processes and equipment for prolonged high-temperature operation would significantly reduce equipment lifespan and production safety. While replacing materials with high-temperature resistant materials could meet these requirements to some extent, it would greatly increase costs. Simply installing a high-temperature resistant inner liner within the device only ensures insulation and cannot meet heat transfer requirements. Existing heaters are insufficient to meet the heating demands of a pyrolysis reduction reactor with an inner liner. Therefore, the applicant's goal in further research and development, building upon the aforementioned technical solutions, is to further increase the reaction temperature to adapt to the processing needs of ores from different sources. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a process for treating ilmenite ore using solid waste pyrolysis products. The process involves preheating the ilmenite ore to above 1000°C with low-oxygen flue gas, then feeding it along with waste plastics, waste coke, and other raw materials into a pyrolysis reduction reactor for pyrolysis reduction. The pyrolysis of waste plastics and waste coke generates reducing gases, ensuring the reactor is completely in a reducing atmosphere. These gases react with the ilmenite ore at high temperatures to generate magnetically separable elemental iron and Fe3O4, thereby increasing the actual FeTiO3 content. Compared to existing ilmenite ore processing technologies, this method significantly increases the processing temperature, improves processing efficiency, and achieves comprehensive energy utilization.

[0005] The main concept of this invention is to replace the direct heating method in the heating reduction reactor as described in the previous application with a method that moves the heating process forward. Instead, a separate raw material heater is used to directly heat the preheated raw materials. In this step, the raw materials are heated to a high temperature of over 1000°C before being fed into the reduction reactor. Simultaneously, the flue gas from the raw material heater is purified by a separation device and then fed into the reduction reactor as a heat source to maintain a higher reaction temperature. The flue gas discharged from the reduction reactor can be used for the preheating process of the raw materials after being conditioned by a regenerative fan. This achieves higher heating temperatures while simultaneously considering comprehensive energy utilization. Furthermore, the reduction reactor does not require secondary heating; it only needs to meet the insulation requirements. Therefore, it can be replaced with a structure featuring a high-temperature resistant inner liner, reducing equipment costs and extending equipment lifespan.

[0006] The specific technical solution of this application is:

[0007] A process for treating ilmenite ore using solid waste pyrolysis products, comprising the following steps:

[0008] First, the ilmenite ore is crushed and then sent to the raw material preheater for preheating. After being preheated to about 300°C, it is sent to the raw material heater.

[0009] The above steps are similar to those in the prior application, and the inventor will not repeat them here.

[0010] The ilmenite is pulverized to a particle size of 1-3 mm. Within this particle size range, the particles can be heated better and will not be carried out of the device by the flue gas, thus improving the utilization rate of raw materials.

[0011] In the raw material heater, the preheated ilmenite ore is in continuous countercurrent contact with high-temperature flue gas with low oxygen content. The temperature of the high-temperature flue gas is not lower than 1200℃. When the temperature of the ilmenite ore at the outlet of the raw material heater is higher than 1000℃, it can be sent to the reduction reactor. After the high-temperature flue gas passes through the separation device to separate solid impurities, it is sent to the insulation cavity of the reduction reactor as a heat source for heating and insulation.

[0012] Preferably, a hopper with a material seal can be installed between the raw material heater and the reduction reactor. The hopper can temporarily store the high-temperature ilmenite ore, seal the reduction reactor to prevent the leakage of reducing gases generated inside the reactor, and adjust the amount of ilmenite ore entering the reduction reactor to facilitate the adjustment of its reduction degree.

[0013] Preferably, the raw material heater, hopper, and reduction reactor are all equipped with high-temperature resistant inner liner, such as high-temperature resistant ceramic material, to ensure that the above devices can withstand temperatures above 1200°C.

[0014] In the reduction reactor, high-temperature ilmenite ore comes into contact with waste that can generate reducing gases. The reducing gases generated by the pyrolysis of the waste reduce Fe2O3 to elemental iron and Fe3O4 that can be magnetically separated under high temperature. The solid products after pyrolysis and reduction enter the subsequent solid cooling step.

[0015] The solid cooling step described herein is the same as that in the prior application, and the multi-stage cooling device in the prior application is also used. The inventor will not repeat the details here. After cooling, the elemental iron and Fe3O4 in the ilmenite are separated by magnetic separation.

[0016] As described above, compared with the prior art of this application, this application removes the heating device in the reduction reaction apparatus and establishes a separate heating device for the ilmenite raw material. High-temperature flue gas is used to directly exchange heat with the ilmenite raw material, greatly increasing its temperature. This raw material then acts as a heat carrier in the reduction reaction step, maintaining its temperature above 900°C within the reduction reactor. Upon contact with waste plastics and waste coke, the waste plastics and waste coke generate a large amount of reducing gas within a very short time, which then comes into contact with the heated ilmenite. Since the temperature at this point is much higher than the 600°C in the prior application, this results in a greater amount of FeTiO3-Fe2O3 solid solution dissolving from the ilmenite. Quickly, hematite lamellae precipitate in ilmenite and are oriented in (0001). High temperature enables more Fe2O3 to precipitate. At temperatures above 900°C, in an atmosphere filled with reducing gas, the precipitated Fe2O3 can be reduced to ferrous oxide. Ferrous oxide is further reduced to elemental iron. The ferrous oxide that is not reduced to elemental iron combines with Fe2O3 to form Fe3O4. The elemental iron and Fe3O4 formed can be magnetically separated, thus separating them from FeTiO3. Compared with the prior application, more magnetically separable elemental iron and Fe3O4 are reduced and separated from ilmenite, increasing the actual content of FeTiO3 and facilitating subsequent processing to obtain metallic titanium. Similar to the prior application, in order to ensure the continuity of this reaction process, the residence time of a unit volume of ilmenite in the reduction reactor is generally controlled to be more than 2 hours, which is lower than that in the prior application. This is because the pyrolysis and reduction reactions proceed more rapidly after the reaction temperature is increased. The amount of waste plastics and waste coke fed in is excessive, thereby ensuring that there are enough reducing substances produced. The specific principle in this step is basically the same as that in the prior application, including the reducing substances produced after the pyrolysis of waste materials. The inventor will not elaborate further.

[0017] In the above process, the low-oxygen, high-temperature flue gas serves as the primary heat source, directly heating the ilmenite ore in the raw material heater. The temperature can reach over 1200℃. At this temperature, in conjunction with the crushing of the ilmenite ore, many impurities on the ilmenite ore are directly vaporized, while the solid particles adhering to the ore surface are also removed by the high-temperature flue gas. This improves the actual purity of the ilmenite ore. Furthermore, due to its low oxygen content, it effectively replaces the gas in the raw material heater, placing it in an oxygen-free state and preventing the raw material from being oxidized.

[0018] The high-temperature flue gas obtained after this heat exchange step contains certain solid particles. To mitigate their impact on subsequent steps, these particles need to be separated using a high-temperature resistant dust removal and separation device, as is currently available. The resulting waste heat flue gas can be reused. Since this portion of the flue gas still reaches a temperature of 1000-1200℃ and possesses extremely high heat, the applicant prefers a design where the high-temperature resistant inner liner of the reduction reactor is further encased in a high-temperature resistant outer shell with an insulated cavity. This waste heat flue gas is then introduced into the insulated cavity, creating a secondary heating effect on the inner liner of the reduction reactor. Because its temperature is higher than that of the material inside the inner liner, this provides better heating of the inner liner. The heat preservation effect is excellent, and when the inner tank temperature drops, the flow rate of the waste heat flue gas can be adjusted to continuously radiate heat to the inner tank, thus maintaining the inner tank temperature. This differs from the direct heating method in the prior application, allowing for better utilization of this heat. Furthermore, since the reduction reactor uses a high-temperature resistant inner tank, it can be directly added to the existing device, with a high-temperature resistant coating on the outside, reducing equipment costs. This is also one of the differences between this application and the prior application. By adding a high-temperature resistant inner tank, the existing device can be directly improved, reducing the cost of technology upgrades for enterprises and adapting to the processing temperature requirements of different grades of ilmenite ore.

[0019] Similar to the prior art, the ilmenite ore treated by the aforementioned reduction reactor still contains a large amount of residual heat. The comprehensive utilization of this residual heat is another important objective of this invention. In specific application, the inventors have adopted the same multi-stage cooling device as in the prior art, with the same operating principle and control, which will not be elaborated upon here. Similarly, the hot flue gas discharged from the reduction reactor remains at a very high temperature and has high usability. In this application, by sending it into a regenerating fan and a mixing device, its temperature can be adjusted and used for regulating the temperature of the insulation cavity in the reduction reactor, as well as for preheating the raw materials. After the flue gas has undergone the above multiple uses, it enters the flue gas dust removal and purification system, and is discharged after meeting the standards.

[0020] The above design can maximize the use of the heat contained in the low oxygen content high temperature flue gas in this application, and the flue gas utilization rate is significantly improved compared with the prior application.

[0021] In addition, the flue gas dust removal and purification system connected to the raw material preheater and the gas purification system connected to the reduction reactor adopt the same design as in the prior application, and the inventor will not elaborate further.

[0022] In summary, this processing technology utilizes waste materials that generate reducing gases to pyrolyze at high temperatures to obtain reducing gases. These reducing gases react with ilmenite ore to generate elemental iron and Fe3O4 that can be magnetically separated, thereby increasing the actual FeTiO3 content. Compared with existing ilmenite ore processing technologies, this technology significantly increases the processing temperature, improves processing efficiency, and achieves comprehensive energy utilization. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process flow for treating ilmenite ore using solid waste pyrolysis products as described in this invention. Detailed Implementation

[0024] The following detailed embodiments further illustrate the above-mentioned content of the present invention. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0025] Example 1

[0026] like Figure 1 As shown, a process for treating ilmenite ore using solid waste pyrolysis products includes the following specific steps:

[0027] First, the ilmenite ore is crushed and then sent to the raw material preheater for preheating. After being preheated to about 300°C, it is sent to the raw material heater.

[0028] The degree of crushing of ilmenite ore is controlled so that the particle size is about 2 mm.

[0029] In the raw material heater, the preheated ilmenite ore is in continuous countercurrent contact with high-temperature flue gas with low oxygen content. The temperature of the high-temperature flue gas is not lower than 1200℃. When the temperature of the ilmenite ore at the outlet of the raw material heater is higher than 1000℃, it can be sent to the reduction reactor. After the high-temperature flue gas passes through the separation device to separate solid impurities, it is sent to the insulation cavity of the reduction reactor as a heat source for heating and insulation.

[0030] The raw material heater and reduction reactor are equipped with high-temperature resistant inner liner, such as high-temperature resistant ceramic material, to ensure that the above devices can withstand temperatures above 1200℃.

[0031] In the reduction reactor, high-temperature ilmenite ore comes into contact with waste materials that can generate reducing gases. The reducing gases generated by the pyrolysis of the waste materials reduce Fe2O3 in the ilmenite ore to elemental iron and Fe3O4 that can be separated by magnetic separation under high temperature. The residence time of a unit volume of ilmenite in the reduction reactor is controlled to be more than 2 hours, and the amount of waste plastic and waste coke fed is excessive. The solid product after pyrolysis and reduction enters the subsequent solid cooling step. The cooled ilmenite ore is separated from the elemental iron and Fe3O4 by magnetic separation.

[0032] The solid cooling step described herein is the same as that in the prior application, and it also uses the multi-stage cooling device described in the prior application.

[0033] This embodiment features a separate heating device for ilmenite raw materials. High-temperature flue gas directly exchanges heat with the ilmenite raw materials, significantly raising their temperature. This ilmenite then acts as a heat carrier in the reduction reaction step. The temperature within the reduction reactor remains above 900°C. Upon contact with waste plastics and waste coke, the waste plastics and waste coke generate a large amount of reducing gas within a very short time, which then comes into contact with the heated ilmenite. Because the temperature at this point is much higher than the 600°C in the previous application, the FeTiO3-Fe2O3 solid solution in the ilmenite dissolves more readily and rapidly, resulting in the precipitation of hematite lamellae within the ilmenite. (0001) The directional arrangement and high temperature enable the precipitation of more Fe2O3. At temperatures above 900°C, in an atmosphere filled with reducing gas, the precipitated Fe2O3 can be reduced to ferrous oxide, which is further reduced to elemental iron. The ferrous oxide that is not reduced to elemental iron combines with Fe2O3 to form Fe3O4. The elemental iron and Fe3O4 formed can be separated by magnetic separation, thus separating them from FeTiO3. Compared with the prior application, more elemental iron and Fe3O4 that can be separated by magnetic separation are reduced and separated from ilmenite, increasing the actual content of FeTiO3 and facilitating subsequent processing to obtain metallic titanium.

[0034] Low-oxygen, high-temperature flue gas serves as the primary heat source, directly heating ilmenite ore in the raw material heater to temperatures exceeding 1200℃. At this temperature, combined with the crushing of the ilmenite ore, many impurities on the ore are directly vaporized, while solid particles adhering to the ore surface are also removed by the high-temperature flue gas. This improves the actual purity of the ilmenite ore. Furthermore, due to its low oxygen content, it effectively replaces the gas in the raw material heater, creating an oxygen-free environment and preventing the raw material from being oxidized.

[0035] The high-temperature flue gas obtained after this heat exchange step contains certain solid particles. To mitigate their impact on subsequent steps, they need to be separated using a high-temperature resistant dust removal and separation device. The resulting waste heat flue gas can be reused. Since the temperature of this part of the flue gas can still reach 1000-1200℃, it has extremely high heat. To better utilize it, in this embodiment, the applicant uses a design where the high-temperature resistant inner liner of the reduction reactor is wrapped with a high-temperature resistant outer shell with an insulated cavity. This waste heat flue gas is introduced into the insulated cavity to form a secondary heating of the inner liner of the reduction reactor. Because its temperature is higher than that of the material inside the inner liner, it can achieve a better heat preservation effect on the inner liner. Furthermore, when the temperature of the inner liner decreases, the flow rate of the waste heat flue gas can be adjusted to allow it to continuously radiate heat to the inner liner, thereby maintaining the temperature of the inner liner.

[0036] The ilmenite ore treated in the aforementioned reduction reactor still contains a large amount of residual heat. In specific applications, the inventors have adopted the same multi-stage cooling device as in the prior application, with the same operating principle and control, which will not be elaborated upon here. Similarly, the hot flue gas discharged from the reduction reactor is still at a very high temperature and has a high utilization rate. In this application, by sending it into a regenerating fan and a mixing device, its temperature can be adjusted and used for regulating the temperature of the insulation cavity of the reduction reactor, as well as for preheating the raw materials. After the flue gas has been used multiple times, it enters the flue gas dust removal and purification system, and is discharged after meeting the standards.

[0037] The above design can maximize the utilization of the heat contained in the low-oxygen-content high-temperature flue gas in this application, and the flue gas utilization rate is significantly improved compared with the prior application.

[0038] In addition, the flue gas dust removal and purification system connected to the raw material preheater and the gas purification system connected to the reduction reactor adopt the same design as in the prior application, and the inventor will not elaborate further.

[0039] Example 2

[0040] A process for treating ilmenite ore using solid waste pyrolysis products, comprising the following steps:

[0041] First, the ilmenite ore is crushed and then sent to the raw material preheater for preheating. After being preheated to about 300°C, it is sent to the raw material heater.

[0042] The degree of crushing of ilmenite ore is controlled so that the particle size is 1-2 mm.

[0043] In the raw material heater, the preheated ilmenite ore is in continuous countercurrent contact with high-temperature flue gas with low oxygen content. The temperature of the high-temperature flue gas is not lower than 1200℃. When the temperature of the ilmenite ore at the outlet of the raw material heater is higher than 1000℃, it is sent to the reduction reactor. After the high-temperature flue gas passes through the separation device to separate solid impurities, it is sent to the insulation cavity of the reduction reactor as a heat source for heating and insulation.

[0044] A hopper with a material seal is installed between the raw material heater and the reduction reactor. The hopper is used to temporarily store the high-temperature ilmenite ore and seal the reduction reactor to prevent the leakage of reducing gas generated inside the reactor. The amount of ilmenite ore entering the reduction reactor can also be adjusted by the hopper, which facilitates the regulation of the degree of reduction.

[0045] Preferably, the above-mentioned raw material heater, hopper and reduction reactor are all equipped with high-temperature resistant inner liner, such as high-temperature resistant ceramic material, so as to ensure that the above devices can withstand high temperatures of 1200°C or higher.

[0046] In the reduction reactor, high-temperature ilmenite ore comes into contact with waste materials that can generate reducing gases. The reducing gases generated by the pyrolysis of the waste materials reduce Fe2O3 to elemental iron and Fe3O4 that can be separated by magnetic separation under high temperature. The residence time of ilmenite per unit volume in the reduction reactor is controlled to be more than 2 hours, and the amount of waste plastics and waste coke fed is excessive. The solid products after pyrolysis and reduction enter the subsequent solid cooling step.

[0047] Apart from the above, the process settings in this embodiment are the same as those in Embodiment 1, and the inventors will not repeat them here.

[0048] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A process for treating ilmenite ore with solid waste pyrolysis products, characterized by, The specific steps are as follows: First, the ilmenite ore is crushed and then fed into the raw material preheater for preheating. After being preheated to 300°C, it is fed into the raw material heater. The degree of crushing of the ilmenite ore is to control the particle size to be 1-3mm. In the raw material heater, the preheated ilmenite ore is in continuous countercurrent contact with high-temperature flue gas with low oxygen content. The temperature of the high-temperature flue gas is not lower than 1200℃. When the temperature of the ilmenite ore at the outlet of the raw material heater is higher than 1000℃, it is sent to the reduction reactor. Inside the reduction reactor, high-temperature ilmenite ore comes into contact with waste materials that can generate reducing gases. The reducing gases generated by the pyrolysis of the waste materials reduce Fe2O3 to elemental iron and Fe3O4 that can be magnetically separated under high-temperature conditions. The solid products after pyrolysis and reduction enter the subsequent solid cooling step. Both the raw material heater and the reduction reactor are equipped with high-temperature resistant inner liner that can withstand temperatures above 1200℃.

2. The process of claim 1 wherein, After the high-temperature flue gas passes through a separation device to separate solid impurities, it is sent as a heat source into the insulated cavity of the reduction reactor to serve as a heat source for heating and insulation.

3. The process of claim 1 wherein, A hopper with a material seal is set between the raw material heater and the reduction reactor. The hopper is used to temporarily store the high-temperature ilmenite ore, seal the reduction reactor, and adjust the amount of ilmenite ore entering the reduction reactor.

4. The process of claim 1 wherein, The solid cooling step is achieved using a multi-stage cooling device.

5. The process of claim 1 wherein, The raw material preheater is connected to a flue gas dust removal and purification system, and the reduction reactor is connected to a gas purification system.

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