Method for extracting germanium and preparing tar and coke under assistance of germanium-containing lignite pyrolysis gas

Abstract

The invention relates to a method for extracting germanium and preparing tar and coke under the assistance of pyrolysis gas of germanium-containing lignite, which comprises the following steps: (1) drying, crushing and screening the germanium-containing lignite, pyrolyzing in an oxygen-free atmosphere at a first pyrolysis temperature of 600-800 DEG C, and condensing and collecting the pyrolysis gas to obtain tar; and (2) heating to 900-1100 DEG C at a second pyrolysis temperature for pyrolysis, condensing and collecting pyrolysis gas to obtain a germanium enrichment, returning uncondensed pyrolysis gas to the pyrolysis environment to serve as a pyrolysis atmosphere, and collecting coke after the pyrolysis is completed. According to the method, pyrolysis gas circulation is used for assisting pyrolysis, the atmosphere is adjusted by refluxing the pyrolysis gas, and the reducing environment is kept, so that germanium is effectively prevented from being oxidized or combined with coke, the volatilization efficiency of germanium is improved, the gas phase conversion rate of germanium is remarkably improved, and the volatilization rate of germanium can reach 98% or above.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal chemical industry and rare metal extraction, and particularly relates to a method for efficiently extracting germanium from germanium-containing lignite and simultaneously preparing metallurgical coke and tar by coal gas circulation assisted pyrolysis, which is suitable for efficient resource utilization of germanium-containing lignite and development and utilization of germanium. BACKGROUND

[0002] Germanium is an important mineral resource and can be widely used in infrared optical systems, optical fibers, polymer catalysis, photovoltaic power generation, electronic equipment and 5G communication fields. At present, the methods for extracting germanium from lignite mainly include fire method and wet method. The fire method, i.e. combustion method, controls the enrichment of germanium in coal ash or flue dust through oxidation / reduction atmosphere. However, due to the low calorific value (12-16 MJ / kg) and poor combustion efficiency of lignite, the resource utilization rate is less than 40%. In addition, the germanium grade of germanium-rich flue dust is low, and the content of silicon-germanium solid solution is high, so a large amount of acid is needed in the subsequent purification process, and a large amount of residue is generated. The wet method, i.e. acid leaching method, can directly process raw coal, but it needs to consume high-concentration acid (such as 6 mol / L HCl), and the leaching period is as long as 8-12 hours, which leads to serious equipment corrosion and high operating cost. At the same time, germanium in lignite is mostly complexed with organic matter, and the extraction efficiency of conventional acid leaching for low-grade ore (germanium content <200 ppm) is low, which limits its industrial application. Therefore, both the fire method and the wet method for extracting germanium have the problems of low germanium recovery efficiency, poor resource utilization rate, environmental pollution and high equipment maintenance cost.

[0003] Pyrolysis method is considered as an effective way to utilize lignite resources and extract germanium, but there are still key bottlenecks in the existing technology. For example: CN1814701A discloses a method for extracting germanium-containing substances from lignite dry distillation and preparing semi-coke, which dry distills at 1100℃ for 10 hours, successfully realizes 87.15% of germanium volatilization, and to some extent realizes the enrichment of germanium resources and the preparation of semi-coke. However, the germanium volatilization rate obtained by this method is still relatively low, the dry distillation time required for extracting germanium is still long, and the phase composition of germanium in the enriched material is not clear, and the grade is not clear. In addition, this method only focuses on germanium and semi-coke, and does not recover lignite pyrolysis gas, tar and other components, and the lignite full component utilization is insufficient.

[0004] In addition, the paper titled "Study on Partitioning Behavior of Germanium in the Dry Distillation Process of Germanium-rich Lignite" was published in Mineral Protection and Utilization, 2022, 42(3):8-14. The study showed that at a pyrolysis final temperature of 650℃ and a holding time of 30 minutes, the germanium volatilization rate was 98.29%. However, this result is quite different from the volatilization temperature of germanium monoxide (800-1000℃) and germanium sulfide (700-900℃), and the research data needs to be discussed. CN205821424U discloses a device for extracting germanium by dry distillation of germanium-containing lignite. The device uses nitrogen as a carrier gas to better maintain the reducing atmosphere during pyrolysis. However, due to the high cost of nitrogen and the difficulty in implementing large-scale industrial applications, the equipment cost and maintenance difficulty are increased, which limits the widespread application of this technology. SUMMARY

[0005] In view of the above-mentioned prior art, the present invention finds that using a two-stage pyrolysis process and recycling pyrolysis gas as the pyrolysis atmosphere can not only improve the germanium volatilization rate, but also reduce the pyrolysis temperature and time while recovering higher germanium grade, and can realize the full component utilization of lignite resources. The present invention is based on the above findings.

[0006] Therefore, the purpose of the present invention is to provide a method for extracting germanium by dry distillation of germanium-containing lignite with the aid of pyrolysis gas and producing tar and coke. By using pyrolysis gas to assist in pyrolysis and realizing the full component utilization of lignite resources, a method combining two-stage pyrolysis process and refluxing pyrolysis gas to adjust the atmosphere is used to achieve efficient volatilization of germanium and full component recovery of lignite resources.

[0007] The technical solution to achieve the above-mentioned purpose of the invention can be summarized as follows:

[0008] A method for extracting germanium by dry distillation of germanium-containing lignite with the aid of pyrolysis gas and producing tar and coke, comprising the following steps:

[0009] (1) Dry, crush and sieve the germanium-containing lignite, and pyrolyze it at a first pyrolysis temperature of 600℃-800℃ in an oxygen-free atmosphere to obtain tar by condensing and collecting the pyrolysis gas;

[0010] (2) Pyrolyze it at a second pyrolysis temperature of 900℃-1100℃ to obtain germanium-rich material by condensing and collecting the pyrolysis gas, and return the uncondensed pyrolysis gas to the pyrolysis environment to serve as the pyrolysis atmosphere. After pyrolysis is completed, coke is collected.

[0011] According to the present invention, preferably, the moisture content of the germanium-containing lignite used in step (1) is ≤10.0%, and the particle size for pyrolysis is ≤0.5mm.

[0012] According to the present invention, preferably, the first pyrolysis temperature in step (1) is 650℃-750℃, and the first pyrolysis time is 0.5h-2h.

[0013] According to the present application, preferably, the second pyrolysis temperature in step (2) is 950-1100℃, and the second pyrolysis time is 1-6h.

[0014] Preferably, the gas flow rate of the pyrolysis gas returned to the pyrolysis environment to serve as the pyrolysis atmosphere is 0.01-1L / min, further preferably 0.1L / min.

[0015] According to the present application, preferably, the collected coke in step (2) is further washed and deslimed to obtain high-value high-carbon clean coal and low-value high-ash tail coal.

[0016] According to the present application, preferably, the condensation temperature in steps (1) and (2) is 5-20℃, and further preferably, condensation water is used for condensation.

[0017] According to the present application, preferably, the method for preparing germanium-containing lignite pyrolysis gas to assist germanium extraction and produce tar and coke adopts a germanium-rich lignite pyrolysis and full-component utilization device, which comprises an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit, and a tail gas treatment unit.

[0018] The inert gas supply unit comprises an inert gas storage device and a first gas exchange device connected thereto, the lignite pyrolysis unit comprises a pyrolysis chamber, a pyrolysis control device arranged on the pyrolysis chamber, and a quartz filler device arranged in the pyrolysis chamber, the pyrolysis product collection unit comprises a germanium-rich product collection device, a tar condensation device, a primary tar collection device, a secondary tar collection device, and a pyrolysis gas drying device connected in sequence, the pyrolysis gas circulation unit comprises a second gas exchange device, a pyrolysis gas buffer device, and a pyrolysis gas circulation pump connected in sequence, and the tail gas treatment unit comprises a tail gas dust removal device, a tail gas neutralization device, and a tail gas adsorption device connected in sequence.

[0019] The gas outlet of the first gas exchange device is connected to the gas inlet of the pyrolysis chamber, the gas outlet of the pyrolysis chamber is connected to the gas inlet of the tar condensation device, the gas outlet of the pyrolysis gas drying device is connected to the gas inlet of the second gas exchange device, the gas outlet of the second gas exchange device is connected to the pyrolysis gas buffer device and the tail gas dust removal device, and the pyrolysis gas circulation pump is connected to the first gas exchange device.

[0020] The germanium-containing lignite is dried, crushed, and sieved, and then placed in a quartz packing device, inert gas storage device and first gas exchange device are opened, and the inert gas is used to replace the residual air in the whole device; the first pyrolysis temperature T1 and the first pyrolysis time t1 of the pyrolysis control device are set, the second pyrolysis temperature T2 and the second pyrolysis time t2 are set, and the pyrolysis program is started; the temperature is raised to the first pyrolysis temperature T1, and the tar is condensed by the tar condensing device and collected by the first tar collecting device and the second tar collecting device; then, the temperature is raised to the second pyrolysis temperature T2 for germanium extraction by pyrolysis gas assisted pyrolysis; during the pyrolysis process, the germanium-rich volatile matter is collected by the germanium-rich product collecting device, and the pyrolysis gas is dried by the pyrolysis gas drying device, stored by the pyrolysis gas buffer device, and pumped into the pyrolysis chamber by the pyrolysis gas circulating pump through the first gas exchange device for assisted pyrolysis; the tail gas after pyrolysis passes through the second gas exchange device and is treated in turn by the tail gas dust removal device, the tail gas neutralization device and the tail gas adsorption device.

[0021] The beneficial effects of the present application are as follows:

[0022] 1. The present application uses pyrolysis gas circulation assisted pyrolysis, adjusts the atmosphere by refluxing the pyrolysis gas, and maintains a reducing environment, thereby effectively preventing the oxidation or combination of germanium with coke. The volatilization efficiency of germanium is improved, the gas phase conversion rate of germanium is significantly improved, and the volatilization rate of germanium can be as high as 98% or more.

[0023] 2. The present application adopts a two-stage pyrolysis process, tar separation and collection are realized in the first stage of pyrolysis, and high-temperature pyrolysis gas is recycled and used to promote the volatilization of germanium in the second stage of pyrolysis. The two-stage pyrolysis process can significantly improve the volatilization efficiency of germanium, reduce the solid loss of germanium, and improve the overall recovery rate of germanium. Through the collection of germanium-rich volatile matter, germanium can be effectively recovered, and the germanium grade in the final germanium-rich product can reach more than 10%. While recovering high-grade germanium products, the pyrolysis temperature and time are reduced.

[0024] 3. The present application realizes the cascade collection of tar, coke and germanium-rich volatile matter by this segmented pyrolysis method, which not only can efficiently extract germanium from lignite, but also can synchronously obtain valuable products such as coke and tar. The recycling and recycling of pyrolysis gas realizes the full-component resource utilization of germanium-containing lignite, and optimizes the comprehensive utilization effect of resources.

[0025] 4. The present application avoids the large use of inert gas by recycling the pyrolysis gas, significantly reduces the consumption of external gas, reduces energy consumption and cost, and avoids the problem that germanium is difficult to volatilize under air atmosphere.

[0026] 5. The present application simultaneously reduces the emission of harmful gas, meets the environmental protection requirements, has good ecological benefits, higher universality and stronger industrial expandability. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Process flow chart of the method for pyrolysis of germanium-containing lignite by using pyrolysis gas to assist germanium extraction and preparation of tar and coke.

[0028] Figure 2 Main structure schematic diagram of the device for pyrolysis of germanium-rich lignite and full component utilization.

[0029] Figure 3 Influence law graph of the two-stage pyrolysis temperature on product yield and germanium volatilization rate in embodiment 1 of the present application.

[0030] Figure 4 Influence law graph of the pyrolysis gas circulation rate on product yield and germanium volatilization rate in embodiment 2 of the present application.

[0031] Figure 5 Influence law graph of the two-stage pyrolysis time on product yield and germanium volatilization rate in embodiment 3 of the present application.

[0032] Figure 6 Scanning electron microscope graph of the germanium-rich volatilization matter in embodiment 4 of the present application.

[0033] Figure 7 XRD spectrum graph of the germanium-rich volatilization matter in embodiment 4 of the present application.

[0034] Figure 8 XPS spectrum graph of the germanium-rich volatilization matter in embodiment 4 of the present application.

[0035] 1-inert gas storage device; 2-first gas exchange device; 3-pyrolysis control device; 4-pyrolysis chamber; 5-quartz packing device; 6-germanium-rich product collection device; 7-tar condensation device; 8-primary tar collection device; 9-secondary tar collection device; 10-pyrolysis gas drying device; 11-second gas exchange device; 12-pyrolysis gas buffer device; 13-pyrolysis gas circulation pump; 14-tail gas dust removal device; 15-tail gas neutralization device; 16-tail gas adsorption device. DETAILED DESCRIPTION

[0036] The present application adopts a two-stage pyrolysis process and uses the pyrolysis gas as a pyrolysis gas atmosphere, which can not only improve the germanium volatilization rate, but also reduce the pyrolysis temperature and time while recovering high-grade germanium products, and can realize full component utilization of lignite resources.

[0037] As shown in the flow chart, Figure 1 A method for pyrolysis of germanium-containing lignite by using pyrolysis gas to assist germanium extraction and preparation of tar and coke, comprising the following steps:

[0038] (1) drying, crushing and screening the germanium-containing lignite, pyrolyzing under an oxygen-free atmosphere and at a first pyrolysis temperature of 600-800 DEG C, and condensing and collecting the pyrolysis gas to obtain tar;

[0039] (2) pyrolysis at a second pyrolysis temperature of 900-1100°C, condensing and collecting the pyrolysis gas to obtain germanium-enriched material, and returning the uncondensed pyrolysis gas to the pyrolysis environment to serve as the pyrolysis atmosphere, and collecting the coke after the pyrolysis is completed.

[0040] According to the present application, the moisture content of the germanium-containing lignite used in step (1) is ≤10.0%, and the particle size of the screened particles is ≤0.5 mm.

[0041] According to the present application, the residual air in the pyrolysis system is replaced with an inert gas before pyrolysis, which plays a protective role in the initial stage of pyrolysis and prevents oxidation reactions during the pyrolysis process. In one or more preferred embodiments, the inert gas is nitrogen or argon.

[0042] According to the present application, the first-stage pyrolysis in step (1) is mainly used to decompose the volatile organic compounds in the lignite and condense and recover tar, etc. In one or more preferred embodiments, the first pyrolysis temperature is 650-750°C, and the first pyrolysis time is 0.5-2 h.

[0043] According to the present application, the second-stage pyrolysis in step (2) is mainly used to promote the efficient volatilization of germanium and condense and recover germanium-enriched material, and the collected germanium-enriched volatilization material is attached to the collection device in solid form. At the second pyrolysis temperature, germanium is dissociated from the lignite and mainly volatilized in the form of GeO2. In one or more preferred embodiments, the second pyrolysis temperature is 950-1100°C, and the second pyrolysis time is 1-6 h.

[0044] In one or more preferred embodiments, the heating rate of the two-stage pyrolysis process is 2-10°C / min.

[0045] According to the present application, the main components of the pyrolysis gas in the second-stage pyrolysis in step (2) are CO, H2, CH4, H2S, etc., and the pyrolysis gas is circulated to the pyrolysis system to adjust the pyrolysis atmosphere by refluxing the pyrolysis gas, thereby ensuring that a reducing atmosphere is maintained during the second-stage pyrolysis, and GeO2 is reduced to GeO, GeS, or metallic Ge under the reducing action of the pyrolysis gas. The reducing atmosphere can prevent the oxidation or combination of germanium with coke, effectively promoting the efficient volatilization and extraction of germanium until the end of the pyrolysis process.

[0046] In one or more preferred embodiments, the gas flow rate of the pyrolysis gas returned to the pyrolysis environment to serve as the pyrolysis atmosphere is 0.01 L / min-1 L / min, and is further preferably 0.1 L / min.

[0047] In one or more preferred embodiments, a multi-stage condensation system is used to condense and collect the germanium-enriched material, thereby improving the recovery efficiency of germanium and avoiding the loss of germanium. In addition, other valuable gas components can also be recovered by stages.

[0048] In one or more preferred embodiments, the condensation temperature in steps (1) and (2) is 5-20°C, and further preferably condensation is performed using chilled water.

[0049] According to the present application, coke is collected in the pyrolysis system after pyrolysis, and the coke exists in the form of powder. The collected coke can be further washed, separated and deslimed to obtain high-value high-carbon clean coal and low-value high-ash tail coal. In one or more preferred embodiments, the washing, separation and desliming method used is froth flotation, and in addition, methods such as density-based separation and desliming can also be used; the high-carbon clean coal after washing, separation and desliming can be further used as energy or for other industrial purposes, and the low-ash tail coal is disposed of as a byproduct.

[0050] According to the present application, in order to effectively operate the method for pyrolyzing germanium-containing lignite to assist germanium extraction and produce tar and coke, and to achieve high-grade germanium enrichment extraction and coke and tar collection, a device for pyrolyzing germanium-containing lignite to enrich germanium and utilize all components is designed. As shown in the figure, the device comprises: an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit. Figure 2

[0051] The inert gas supply unit comprises an inert gas storage device 1 and a first gas exchange device 2 connected thereto. The inert gas supply unit is used to provide inert gas to replace air in the system before starting.

[0052] The lignite pyrolysis unit comprises a pyrolysis chamber 4, a pyrolysis control device 3 arranged on the pyrolysis chamber 4, and a quartz filler device 5 arranged in the pyrolysis chamber 4. The pyrolysis control device 3 controls the time and temperature of pyrolysis, and the quartz filler device 5 is placed in the pyrolysis chamber 4 for holding the pyrolysis raw material.

[0053] The pyrolysis product collection unit comprises, in sequence, a germanium-rich product collection device 6, a tar condensation device 7, a primary tar collection device 8, a secondary tar collection device 9 and a pyrolysis gas drying device 10. The germanium-rich product collection device 6 is placed at the gas outlet of the pyrolysis chamber 4 for collecting the germanium-rich volatiles condensed after volatilization during pyrolysis; the tar condensation device 7 is used to condense the first-stage pyrolysis products, the primary tar collection device 8 and the secondary tar collection device 9 are used to collect the condensed tar, and the pyrolysis gas drying device 10 is used to dry the remaining pyrolysis gas.

[0054] The pyrolysis gas circulation unit comprises, in sequence, a second gas exchange device 11, a pyrolysis gas buffer device 12 and a pyrolysis gas circulation pump 13. After the germanium-rich products and tar are collected, the remaining pyrolysis gas is dried and stored in the pyrolysis gas buffer device 12 and pumped into the pyrolysis chamber 4 by the pyrolysis gas circulation pump 13 through the first gas exchange device 2 to assist pyrolysis.

[0055] ​The tail gas treatment unit comprises a tail gas dedusting device 14, a tail gas neutralizing device 15 and a tail gas adsorbing device 16 connected in sequence. The tail gas dedusting device 14 is used to remove particulate matters such as coke dust in the pyrolysis gas to prevent the subsequent equipment from being blocked; the tail gas neutralizing device 15 is used to neutralize sulfur-containing gases such as H2S, SO2 and halides; and the tail gas adsorbing device 16 is used to adsorb residual tar and volatile organic compounds.

[0056] The gas outlet of the first gas exchange device 2 is connected to the gas inlet of the pyrolysis chamber 4, the gas outlet of the pyrolysis chamber 4 is connected to the gas inlet of the tar condensing device 7, the gas outlet of the pyrolysis gas drying device 10 is connected to the gas inlet of the second gas exchange device 11, the gas outlet of the second gas exchange device 11 is connected to the pyrolysis gas buffer device 12 and the tail gas dedusting device 14, and the pyrolysis gas circulating pump 13 is connected to the first gas exchange device 2.

[0057] In one or more preferred embodiments, the method for preparing tar and coke by pyrolysis of germanium-containing lignite and auxiliary germanium extraction adopts a germanium-rich pyrolysis and full-component utilization device, which comprises an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit.

[0058] The inert gas supply unit comprises an inert gas storage device 1 and a first gas exchange device 2 connected thereto, the lignite pyrolysis unit comprises a pyrolysis chamber 4, a pyrolysis control device 3 arranged on the pyrolysis chamber 4 and a quartz filler device 5 arranged in the pyrolysis chamber 4, the pyrolysis product collection unit comprises a germanium-rich product collection device 6, a tar condensing device 7, a primary tar collection device 8, a secondary tar collection device 9 and a pyrolysis gas drying device 10 connected in sequence, the pyrolysis gas circulation unit comprises a second gas exchange device 11, a pyrolysis gas buffer device 12 and a pyrolysis gas circulating pump 13 connected in sequence, and the tail gas treatment unit comprises a tail gas dedusting device 14, a tail gas neutralizing device 15 and a tail gas adsorbing device 16 connected in sequence.

[0059] The gas outlet of the first gas exchange device 2 is connected to the gas inlet of the pyrolysis chamber 4, the gas outlet of the pyrolysis chamber 4 is connected to the gas inlet of the tar condensing device 7, the gas outlet of the pyrolysis gas drying device 10 is connected to the gas inlet of the second gas exchange device 11, the gas outlet of the second gas exchange device 11 is connected to the pyrolysis gas buffer device 12 and the tail gas dedusting device 14, and the pyrolysis gas circulating pump 13 is connected to the first gas exchange device 2.

[0060] The germanium-containing lignite is dried, crushed, and sieved, and then placed in the quartz packing device 5, the inert gas storage device 1 and the first gas exchange device 2 are opened, and the inert gas is used to replace the residual air in the entire device; the first-stage pyrolysis temperature T1 and the first-stage pyrolysis time t1 of the pyrolysis control device 3 are set, the second-stage pyrolysis temperature T2 and the second-stage pyrolysis time t2 are set, and the pyrolysis program is started; the temperature is raised to the first-stage pyrolysis temperature T1, the tar is condensed by the tar condensing device 7 and then collected by the primary tar collecting device 8 and the secondary tar collecting device 9; then, the temperature is raised to the second-stage pyrolysis temperature T2 for germanium extraction by the pyrolysis gas assisted pyrolysis; during the pyrolysis process, the germanium-rich volatile matter is collected by the germanium-rich product collecting device 6, the pyrolysis gas is dried by the pyrolysis gas drying device 10, and then stored in the pyrolysis gas buffer device 12 and pumped into the pyrolysis chamber 4 by the pyrolysis gas circulating pump 13 through the first gas exchange device 2 for assisted pyrolysis; the tail gas after the pyrolysis is sequentially introduced into the tail gas dust removal device 14, the tail gas neutralization device 15 and the tail gas adsorption device 16 through the second gas exchange device 11.

[0061] The working principle of the present application is as follows:

[0062] Germanium mainly exists in the form of organic matter in lignite, and is usually combined with macromolecular organic matter such as humic acid and fulvic acid in the form of a complex, and is adsorbed or bonded in the organic structure of coal through functional groups such as carboxyl and phenolic hydroxyl groups;

[0063] During the first-stage pyrolysis of the germanium-containing lignite, water, organic matter and the like in the coal are deconstructed to produce pyrolysis products such as tar and coal gas, and the tar is obtained by condensation. During the second-stage pyrolysis, germanium existing in the coal is dissociated and volatilized in the form of GeO2.

[0064] The reducing solid matter such as carbon powder and the like in the pyrolysis system, and the pyrolysis gas such as CO, H2, CH4, H2S and the like, reduce the GeO2 to GeO, GeS or metallic Ge, which is then migrated with the pyrolysis gas to the condensing area for condensation, and the oxide or sulfide of germanium is obtained in the condensing area.

[0065] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0066] Exemplarily, 200 g of lignite sample is taken and added to a lignite pyrolysis unit, and an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit are sequentially installed and connected, and air in the system is replaced. The first-stage pyrolysis temperature is set to 600-800℃, the heating rate is 2-10℃ / min, the pyrolysis time is 0.5-2h, the second-stage pyrolysis temperature is 900-1100℃, the heating rate is 2-10℃ / min, and the pyrolysis time is 1-4.0h. The pyrolysis gas circulation unit is turned on, and the products are collected. After the pyrolysis is completed, the germanium-rich volatiles, coke and tar are collected respectively, the germanium content of each product is determined after microwave digestion, the germanium volatilization rate is calculated, and the pyrolysis gas is discharged after tail gas treatment. The obtained coke is subjected to flotation and ash removal to obtain high-quality coke. The results show that the germanium volatilization rate is 72.0%-96.0%, the ash content of the washed and selected coke is 10.26%-15.77%, and the calorific value is 25.0-30.0 MJ / kg.

[0067] Example 1

[0068] 200 g of dried and crushed germanium-containing lignite sample is taken and placed in a lignite pyrolysis unit, and an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit are sequentially installed and connected, and air in the system is replaced. The first-stage pyrolysis temperature is set to 700℃, the pyrolysis gas circulation rate is 100 ml / min, and the second-stage pyrolysis temperature is set to 900℃, 1000℃ and 1100℃ respectively, and the volatilization experiment is performed for 6.0h.

[0069] The pyrolysis gas circulation unit is turned on, and the products are collected. After the pyrolysis is completed, the germanium-rich volatiles, coke and tar are collected respectively, the germanium content of each product is determined after microwave digestion, the germanium volatilization rate is calculated, and the pyrolysis gas is discharged after tail gas treatment. The obtained coke is subjected to flotation and ash removal to obtain high-quality coke. The results are shown in Figure 3

[0070] Figure 3 The results show that, under the same gas flow rate and pyrolysis time, the germanium volatilization rate increases continuously with the increase of the pyrolysis temperature, and the germanium volatilization rate is the highest at 1100℃. Therefore, the second-stage pyrolysis temperature is preferably 1100℃.

[0071] Example 2

[0072] ​Take 200 g of dried and broken germanium-containing lignite sample and place it into a lignite pyrolysis unit. Install and connect inert gas supply unit, lignite pyrolysis unit, pyrolysis product collection unit, pyrolysis gas circulation unit and tail gas treatment unit in sequence, and replace the air in the system. Set the first-stage pyrolysis temperature to 700 DEG C, and the pyrolysis gas circulation rate to 0, 10, 100, 200 ml / min. Perform the volatilization experiment at the second-stage pyrolysis temperature of 1100 DEG C for 6.0 h respectively.

[0073] Start the pyrolysis gas circulation unit and collect the products. After the pyrolysis, collect the germanium-rich volatiles, coke and tar respectively, and determine the germanium content of each product after microwave digestion. Calculate the germanium volatilization rate, and empty the pyrolysis gas after tail gas treatment. The obtained coke is used to obtain high-quality coke after flotation and descaling. The results are shown in Table 1. Figure 4

[0074] Figure 4 The results show that when the pyrolysis temperature is the same, the germanium volatilization rate increases with the increase of the circulation gas flow rate, and the coke yield does not change significantly with the increase of the gas flow rate. It shows that the circulation flow rate of the pyrolysis gas also has a great influence on the volatilization of germanium. When the gas flow rate is 100 mL / min and the pyrolysis temperature is 1100 DEG C, the volatilization rate of germanium can reach 99.62%. Therefore, the preferred circulation rate of the pyrolysis gas is 100 mL / min.

[0075] Example 3

[0076] Take 200 g of dried and broken germanium-containing lignite sample and place it into a lignite pyrolysis unit. Install and connect inert gas supply unit, lignite pyrolysis unit, pyrolysis product collection unit, pyrolysis gas circulation unit and tail gas treatment unit in sequence, and replace the air in the system. Set the first-stage pyrolysis temperature to 700 DEG C, and the pyrolysis gas circulation rate to 100 ml / min. Perform the volatilization experiment at the second-stage pyrolysis temperature of 1100 DEG C for 1.0 h, 2.0 h, 4.0 h and 6.0 h respectively.

[0077] Start the pyrolysis gas circulation unit and collect the products. After the pyrolysis, collect the germanium-rich volatiles, coke and tar respectively, and determine the germanium content of each product after microwave digestion. Calculate the germanium volatilization rate, and empty the pyrolysis gas after tail gas treatment. The obtained coke is used to obtain high-quality coke after flotation and descaling. The results are shown in Table 1. Figure 5

[0078] Figure 5 The results show that at 1100 DEG C, the pyrolysis volatilization rate of germanium in lignite gradually increases with the extension of the second-stage pyrolysis time. When the holding time is 6.0 h, the volatilization rate of germanium can reach 98.87%. Therefore, the preferred second-stage pyrolysis time is 6.0 h.

[0079] Example 4 ​​

[0080] A 200 g sample of dried and crushed germanium-containing lignite was placed in a lignite pyrolysis unit, and an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit were sequentially installed and connected, and the air in the system was replaced. The first-stage pyrolysis temperature was set to 700 DEG C, the pyrolysis gas circulation rate was 100 ml / min, the second-stage pyrolysis temperature was set to 1100 DEG C, and the pyrolysis was performed for 6.0 h to perform the volatilization experiment.

[0081] The pyrolysis gas circulation unit was turned on, and the products were collected. After the pyrolysis was completed, the germanium-rich volatiles, coke and tar were collected, and the germanium content of each product was determined after microwave digestion, the germanium volatilization rate was calculated, and the pyrolysis gas was discharged after tail gas treatment. The obtained coke was subjected to flotation and deashing to obtain high-quality coke.

[0082] The germanium-rich volatiles were collected, and the germanium content was calculated to be 17.19% after microwave digestion. The main components of the sample were analyzed. The scanning electron microscope image of the sample is shown in Figure 6 , Figure 6 The EDS element distribution spectrum of the sample is shown in Figure 7 and Table 1. The XRD spectrum of the sample is shown in Figure 8 .

[0083] Table 1

[0084]

[0085] As shown in Figure 7 , Figure 8 and Table 1, the main elements of the germanium-rich volatiles are Ge, S, Zn, O, etc., and the main compounds are germanium sulfide, zinc sulfide, lead sulfide and metallic germanium.

[0086] Comparative Example 1

[0087] As described in Example 4, except that:

[0088] The pyrolysis gas circulation unit was turned off, and the pyrolysis gas was not circulated. The germanium-rich volatiles were collected, and the average grade of germanium therein was calculated to be 7.23% after microwave digestion.

[0089] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for extracting germanium from germanium-containing lignite pyrolysis gas and producing tar and coke, comprising the following steps: (1) drying, crushing, and screening the germanium-containing lignite, pyrolyzing it in an oxygen-free atmosphere at a first pyrolysis temperature of 600°C to 800°C, and condensing and collecting the pyrolysis gas to obtain tar; (2) The temperature is raised to the second pyrolysis temperature of 900℃-1100℃ for pyrolysis. The pyrolysis gas is condensed and collected to obtain a germanium-enriched product. The uncondensed pyrolysis gas is returned to the pyrolysis environment to serve as a pyrolysis atmosphere. After the pyrolysis is completed, coke is collected.

2. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: The germanium-containing lignite used in step (1) has a moisture content of ≤10.0% by mass, and particles with a sieve particle size of ≤0.5 mm are used for pyrolysis.

3. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: In step (1), the first pyrolysis temperature is 650° C.-750° C., and the first pyrolysis time is 0.5 h-2 h.

4. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from germanium-containing lignite pyrolysis gas according to claim 1, characterized in that: In step (2), the second pyrolysis temperature is 950°C-1100°C, and the second pyrolysis time is 1h-6h.

5. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: In step (2), the gas flow rate of the pyrolysis gas returning to the pyrolysis environment to serve as the pyrolysis atmosphere is 0.01 L / min to 1 L / min.

6. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: The coke collected in step (2) is further washed and deashed to obtain high-value high-carbon clean coal and low-value high-ash tailings.

7. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: The condensation temperature in steps (1) and (2) is 5°C-20°C.

8. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 7, characterized in that: Condensation water is used for condensation in steps (1) and (2).

9. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: The heating rate of the pyrolysis process in steps (1) and (2) is 2-10°C / min.

10. The method for extracting germanium and producing tar and coke by assisted extraction of germanium from pyrolysis gas of germanium-containing lignite according to claim 1, characterized in that: The method for extracting germanium from germanium-containing lignite pyrolysis gas and producing tar and coke is carried out by using a device for pyrolysis of germanium-containing lignite to enrich germanium and utilize all components. The device comprises: an inert gas supply unit, a lignite pyrolysis unit, a pyrolysis product collection unit, a pyrolysis gas circulation unit and a tail gas treatment unit. The inert gas supply unit comprises an inert gas storage device (1) and a first ventilation device (2) connected thereto; the lignite pyrolysis unit comprises a pyrolysis chamber (4), a pyrolysis control device (3) arranged on the pyrolysis chamber (4) and a quartz filler device (5) arranged in the pyrolysis chamber (4); the pyrolysis product collection unit comprises a germanium-rich product collection device (6), a tar condensation device (7), a primary tar collection device (8), a secondary tar collection device (9) and a pyrolysis gas drying device (10) connected in sequence; the pyrolysis gas circulation unit comprises a second ventilation device (11), a pyrolysis gas buffer device (12) and a pyrolysis gas circulation pump (13) connected in sequence; and the tail gas treatment unit comprises a tail gas dust removal device (14), a tail gas neutralization device (15) and a tail gas adsorption device (16) connected in sequence; The air outlet of the first ventilation device (2) is connected to the air inlet of the pyrolysis chamber (4), the air outlet of the pyrolysis chamber (4) is connected to the air inlet of the tar condensation device (7), the air outlet of the pyrolysis gas drying device (10) is connected to the air inlet of the second ventilation device (11), the air outlet of the second ventilation device (11) is connected to the pyrolysis gas buffer device (12) and the tail gas dust removal device (14), and the pyrolysis gas circulation pump (13) is connected to the first ventilation device (2); The germanium-containing lignite is dried, crushed, and screened, and then placed in a quartz packing device (5). The inert gas storage device (1) and the first ventilation device (2) are turned on, and the residual air in the entire device is replaced with inert gas. The first stage pyrolysis temperature T1 and the first pyrolysis time t1 of the pyrolysis control device (3) are set, and the second stage pyrolysis temperature T2 and the second pyrolysis time t2 are set, and the pyrolysis program is started. The temperature is raised to the first stage pyrolysis temperature T1, and the tar is condensed by the tar condensation device (7) and then collected by the first stage tar collection device (8) and the second stage tar collection device (9). Then After that, the temperature is raised to the second pyrolysis temperature T2 for pyrolysis gas-assisted pyrolysis to extract germanium; during the pyrolysis process, germanium-rich volatiles are collected by the germanium-rich product collection device (6), and the pyrolysis gas is dried by the pyrolysis gas drying device (10), stored by the pyrolysis gas buffer device (12) and pumped into the pyrolysis chamber (4) by the pyrolysis gas circulation pump (13) through the first ventilation device (2) for assisted pyrolysis; after the pyrolysis is completed, the tail gas passes through the second ventilation device (11) and enters the tail gas dust removal device (14), the tail gas neutralization device (15) and the tail gas adsorption device (16) for treatment.

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