Application of a cement kiln to pyrometallurgical lithium extraction from ores and method for pyrometallurgical lithium extraction from ores

Abstract

This invention relates to the field of limestone lithium extraction technology, specifically to the application of cement kilns in pyrometallurgical lithium extraction and methods for pyrometallurgical lithium extraction. The advantages of this invention are that it eliminates the need for granulation, saves water, and avoids the endothermic phase change of water during subsequent roasting; segmented roasting is more energy-efficient than single-stage roasting.

Description

Technical Field

[0001] This invention relates to the field of limestone lithium extraction technology, specifically to the application of a cement kiln for lithium extraction from pyrometallurgical ores and a method for lithium extraction from pyrometallurgical ores. Background Technology

[0002] Lithium, as a crucial rare element for promoting modernization and the development of related industries such as science and technology, is one of the most promising new energy sources and strategic resources. It is widely used in high-energy lithium batteries, the rubber industry, aerospace, ceramics, lasers, medicine, welding, explosives, cement, metallurgy, and new energy, earning it the title of "the energy metal of the 21st century." Many countries, considering both economic development needs and national security, have designated lithium products as strategic reserves and are conducting extensive research into their application technologies.

[0003] In existing technologies, lithium extraction is mainly divided into lithium extraction from ore and lithium extraction from salt lakes, depending on the raw materials. Among them, lithium extraction from ore technology mainly utilizes lithium-containing natural minerals such as spodumene and lepidolite to produce lithium carbonate through smelting.

[0004] Currently, the main technologies for lithium extraction from ore include the sulfuric acid process and the limestone process. Among them, the ore process is the mainstream technology. However, this process consumes large amounts of sulfuric acid and alkali, and produces a large amount of sodium sulfate as a byproduct. First, in regions with weak industrial bases, such as Africa, sulfuric acid is difficult to obtain conveniently; second, in some areas with high environmental protection requirements, the use of sulfuric acid is prohibited.

[0005] The limestone process, which uses readily available limestone as the main raw material, perfectly solves the application problems of the sulfuric acid process.

[0006] The traditional limestone method for lithium extraction involves mixing limestone and spodumene, roasting the mixture, grinding it to 200 mesh, and then performing a two-stage leaching process to finally obtain a lithium-containing solution.

[0007] However, when limestone and spodumene are directly mixed and calcined in a rotary kiln, ring formation occurs in the calcining device, ultimately preventing the equipment from operating continuously and stably.

[0008] In response, the inventors discovered in previous research that mixing spodumene with calcium agents (limestone, calcium oxide, carbide slag, etc.) before adding water to granulate and then calcining can effectively prevent ring formation and ensure that the calcination equipment can operate continuously and stably.

[0009] However, water needs to be added during the granulation process, and the water will consume a lot of energy during the subsequent roasting (1100℃) process.

[0010] Therefore, finding a method that avoids ring formation without granulation is an urgent need for those skilled in the art.

[0011] In order to further reduce costs and achieve maximum economic value, the applicant further explored and obtained the technical solution of this application. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide an application of cement kiln for lithium extraction from pyrometallurgical ore and a method for lithium extraction from pyrometallurgical ore, thereby solving the problems existing in the prior art.

[0013] One of the objectives of this invention is to provide a cement kiln for lithium extraction from pyrometallurgical ores, in order to solve the problem of ring formation during the roasting process of lithium extraction from traditional limestone. The second objective of this invention is to provide a method for lithium extraction from pyrometallurgical ores that eliminates the need for granulation and prevents ring formation during direct roasting, thereby reducing energy consumption.

[0014] This invention discloses the application of cement kilns in lithium extraction from pyrometallurgical ores, specifically in the limestone roasting step of lithium extraction.

[0015] Furthermore, the lithium ore is spodumene.

[0016] Furthermore, the cement kiln includes a preheating section and a transformation section; the temperature of the preheating section is 850~950℃, and the temperature of the transformation section is 1100~1200℃.

[0017] Preferably, the temperature of the preheating section is 900°C and the temperature of the transition section is 1150°C.

[0018] Furthermore, the material resides in the transition section for 50-60 minutes.

[0019] This invention also discloses a method for lithium extraction from pyrometallurgical ore, comprising the following steps: No granulation is required; the calcium agent is mixed with spodumene and then directly calcined using the cement kiln.

[0020] The beneficial effects of this invention are as follows: No granulation is required, saving water and eliminating the need for water to absorb heat during the subsequent roasting phase change; Segmented roasting is more energy-efficient than single-stage roasting. Attached Figure Description

[0021] Figure 1 The calcination state of raw material 1 at different temperatures; Figure 2 Comparative Examples 1-2: XRD diffraction patterns; Figure 3 Comparative examples 3-4: XRD diffraction patterns; Figure 4 Comparative examples 5-6: XRD diffraction patterns; Figure 5Comparative Example 7: XRD diffraction pattern; Figure 6 Raw material 2 calcination state at different temperatures; Figure 7 Comparative examples 8-9: XRD diffraction patterns; Figure 8 Comparative examples 10-11: XRD diffraction patterns; Figure 9 Comparative examples 12-13: XRD diffraction patterns; Figure 10 Comparative Example 14: XRD diffraction pattern. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are only used to illustrate the technical embodiments of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0023] Preparation of raw material composition: Lithium concentrate and limestone were mixed in a certain proportion to form lithium-calcium raw material. The specific parameters are shown in Table 1 below. Table 1. Parameters of Lithium-Calcium Raw Material

[0024] The chemical composition of the prepared lithium-calcium raw material was analyzed, and the results are shown in Table 2 below: Table 2 Chemical composition analysis of lithium-calcium raw materials (by mass fraction)

[0025] The aforementioned lithium-calcium raw materials were selected as the raw materials for roasting.

[0026] To further illustrate the creativity in selecting the preheating section temperature, the following embodiment is provided:

[0027] Raw material 1 is fed into a cement kiln for segmented calcination. The temperature of the preheating section is controlled at 900℃, the calcination temperature of the material in the transition section is controlled at 1050℃~1150℃, the rotation speed of the transition section is controlled within the range of 0.8rpm~1.3rpm, and the residence time of the material in the kiln is 40min~65min. Example

[0028] Raw material 2 is fed into the cement kiln for segmented calcination. The temperature of the preheating section is controlled at 920℃, the calcination temperature of the material in the transition section is controlled at 1050℃~1250℃, the rotation speed of the transition section is controlled within the range of 0.5rpm~1.0rpm, and the residence time of the material in the kiln is 52min~104min. Example

[0029] Raw material 2 is fed into the cement kiln for segmented calcination. The temperature of the preheating section is controlled at 910℃, the calcination temperature of the material in the transition section is controlled at 1050℃~1300℃, the rotation speed of the transition section is controlled within the range of 1.0 rpm, and the residence time of the material in the kiln is 52 min.

[0030] Observation revealed that none of the products in the above embodiments exhibited any wall-sticking phenomenon. Further analysis of the products from each of the above embodiments yielded results shown in Tables 3-6 below: Table 3. Analysis of Product Composition in the Preheating Section - 1

[0031] Table 4. Composition Analysis of Preheating Section Products - 2

[0032] Table 5. Composition Analysis of Transition Stage Products - 1

[0033] Table 6. Composition Analysis of Transition Stage Products - 2

[0034] To further illustrate the beneficial effects of this application, the following comparative examples are provided.

[0035] The prepared lithium-calcium raw material was heated to different temperatures under static calcination conditions, and its state and composition were then analyzed. Specific parameters and test results are shown in Tables 7-9 below: Table 7. Calcination Status

[0036] Table 8 Composition of Roasted Products - 1

[0037] Table 9 Composition of Roasted Products - 2

[0038] like Figure 1 As shown, for raw material 1, as the calcination temperature increases, the material color gradually changes from grayish-white in the uncalcined sample to light yellow, yellow, yellowish-green, and green. With increasing calcination temperature, the material volume shrinks significantly, and the degree of agglomeration becomes obvious and gradually hardens, indicating that as the temperature rises, the material undergoes liquid-phase formation to form sintered agglomerates.

[0039] Specifically as follows: At 850℃, the volume shrinkage is not obvious, and it presents as a slightly loose clump; At 950℃, the volume shrinkage is not obvious, and it shows slight caking; 1000℃; significant volume shrinkage, forming solid lumps; At temperatures above 1100℃, volume shrinkage becomes more pronounced, and lumps become harder. At temperatures of 1150℃ and below, the material does not significantly stick to the crucible wall; at temperatures of 1250℃ and above, the material significantly sticks to the crucible wall.

[0040] like Figures 2-5 As shown: XRD diffraction pattern analysis revealed the following results after calcination of raw material 1: At 850℃, the main mineral phases are calcium carbonate, CaO, and spodumene; At 950℃, the main mineral phases are CaO and spodumene, and the calcium carbonate diffraction peaks disappear. At 1000℃, the main mineral phases are dicalcium silicate (C2S) and CaO, the diffraction peaks of spodumene disappear, and a new C2S mineral phase appears; At 1100℃, the main mineral phases are C2S, CaO, and LiAlO2; At 1150℃, the main mineral phases are C2S, CaO, and LiAlO2; At 1250℃, the main mineral phases are C2S, calcium aluminoferrite, and CaO; At 1300℃, the main mineral phases are C2S, CaO, and LiAlO2.

[0041] like Figure 6 As shown, for raw material 2, as the calcination temperature increases, the material color gradually changes from grayish-white in the uncalcined sample to light yellow, yellow, yellowish-green, and green. With increasing calcination temperature, the material volume shrinks significantly, and the degree of agglomeration becomes obvious and gradually hardens, indicating that as the temperature rises, the material undergoes liquid-phase formation to form sintered agglomerates.

[0042] Specifically as follows: At 850℃, the volume shrinkage is not obvious, and it presents as a slightly loose clump; At 950℃, the volume shrinkage is not obvious, and it shows slight caking; 1000℃; significant volume shrinkage, forming solid lumps; At temperatures above 1100℃, volume shrinkage becomes more pronounced, and lumps become harder. At temperatures of 1150℃ and below, the material does not significantly stick to the crucible wall; at temperatures of 1250℃ and above, the material significantly sticks to the crucible wall.

[0043] like Figures 6-10 As shown: XRD diffraction pattern analysis revealed the following results after calcination of raw material 2: At 850℃, the main mineral phases are calcium carbonate, CaO, and spodumene; At 950℃, the main mineral phases are CaO and spodumene, and the calcium carbonate diffraction peaks disappear. At 1000℃, the main mineral phases are CaO and spodumene, and a new β-type spodumene mineral phase appears. At 1100℃, the main mineral phase is CaO, with newly appearing C2S and γ-LiAlO2 mineral phases; At 1150℃, the main mineral phases are C2S, CaO, and γ-LiAlO2; At 1250℃, the main mineral phases are C2S, CaO, and γ-LiAlO2; At 1300℃, the main mineral phases are C2S, CaO, γ-LiAlO2, and a newly appearing calcium aluminum mineral phase.

[0044] Therefore, 850~900℃ as the preheating temperature can ensure the decomposition of calcium carbonate while maintaining the looseness of the product; From the above results, we can conclude that: When direct single-stage roasting reaches the transformation temperature to form LiAlO2, wall adhesion occurs in all cases (Comparative Examples 4-7, Comparative Examples 11-14); while in two-stage roasting at this temperature, wall adhesion occurs uniformly.

[0045] The selection of the preheating decomposition temperature in the two-stage roasting process is the optimal method obtained through experimental testing. When the temperature is between 850 and 950°C, it will only cause the calcium agent to decompose and form calcium oxide, without producing LiAlO2.

[0046] The selection of the two-stage transformation temperature during the two-stage roasting process is the optimal method obtained through experimental testing. When the temperature is between 1100 and 1250℃, transformation occurs. However, when the temperature is higher than 1250℃, the transformation rate remains basically unchanged, and only the energy consumption increases.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Cement kilns are used for lithium extraction from pyrometallurgical ores, specifically in the limestone roasting step of lithium extraction.

2. Use of a cement kiln for pyrometallurgical ore-based lithium extraction according to claim 1, characterized in that, The lithium ore is spodumene.

3. Use of a cement kiln for pyrometallurgical ore-based lithium extraction according to claim 1, characterized in that, The cement kiln includes a preheating section and a transformation section; the temperature of the preheating section is 850~950℃, and the temperature of the transformation section is 1100~1200℃.

4. Use of a cement kiln for pyrometallurgical ore-based lithium extraction according to claim 1, characterized in that, The temperature of the preheating section is 900℃, and the temperature of the transition section is 1150℃.

5. Use of a cement kiln for pyrometallurgical ore-based lithium extraction according to claim 1, characterized in that, The material stays in the transition section for 50-60 minutes.

6. A method for extracting lithium from pyrometallurgical ore, characterized in that, No granulation is required; the calcium agent is mixed with spodumene and then directly calcined, with the calcination process utilizing the cement kiln described in any one of claims 1 to 5.

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