Method for selectively recovering germanium from germanium-containing smoke through flash boiling chlorination

Abstract

The invention relates to a method for selectively recovering germanium from germanium-containing smoke through flash boiling chlorination, belongs to the field of comprehensive recovery of scattered metals, and solves the problems of high acid consumption, high reaction temperature, high energy consumption, low germanium recovery rate and the like of a process for recovering germanium from germanium-containing smoke in the prior art. The invention relates to a method for selectively recovering germanium from germanium-containing smoke through flash boiling chlorination, which comprises the following steps: (1) chlorination: adding the germanium-containing smoke into a reactor, introducing chlorine into the reactor, and carrying out boiling chlorination reaction at a certain temperature; (2) dust collection: mixed flue gas obtained in the step (1) enters a cyclone separator along with airflow; (3) condensation: introducing the mixed flue gas subjected to dust collection treatment in the step (2) into a multi-stage condensation device to obtain a GeCl4 and SiCl4 liquid phase mixture and tail gas; and (4) refining: introducing the GeCl4 and SiCl4 liquid-phase mixture obtained in the step (3) into rectification equipment, and separating to obtain high-purity liquid-phase GeCl4. And the germanium in the germanium-containing smoke dust is efficiently recycled.

Description

Technical Field

[0001] The invention relates to the field of comprehensive recovery of rare metals, and in particular to a method for selectively recovering germanium from germanium-containing smoke by flash boiling chlorination. Background Art

[0002] As a semiconductor material with high electron mobility, high heat resistance and excellent optical properties, germanium is widely used in solar cells, infrared optics, fiber optic communications, national defense, aerospace, biomedicine and other fields. In recent years, with the rapid development of the electronics industry, the structural adjustment and upgrading of high-end industries has accelerated, and the demand for germanium in various fields has increased significantly.

[0003] Germanium has an extremely low abundance in the earth's crust (about 1.5ppm) and is very dispersed, making it difficult to form an independent mineralization. It mostly exists in the form of co-existence / association in lead-zinc deposits and coal deposits. Germanium-containing coal dust formed by coal combustion is one of the main raw materials for industrial germanium extraction, in which germanium mainly exists in the form of GeO2, which is difficult to volatilize. The main process method for extracting germanium is chlorination distillation. At present, the industrial chlorination distillation method mostly uses liquids and solids as chlorinating agents, among which the liquid chlorinating agent is mainly high-concentration hydrochloric acid. Although the germanium recovery rate is high, the process consumes a lot of acid, discharges a lot of waste residues, and has high subsequent processing costs; solid chlorinating agents mostly use solids such as NH4Cl and CaCl2. This process avoids the use of concentrated acid, but due to the loss of germanium in each process link, the germanium recovery rate is relatively low.

[0004] In summary, the existing process technology does not solve the problems of high acid consumption, large discharge of waste residues and waste liquids, and low germanium recovery rate. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a method for selectively recovering germanium from germanium-containing flue dust by flash boiling chlorination, so as to solve at least one of the problems of the existing process for recovering germanium from germanium-containing flue dust, such as large acid consumption, large amount of waste residue and waste liquid, high reaction temperature, high energy consumption, low germanium recovery rate, poor selectivity of the germanium recovery reaction system, and limited germanium recovery from low-grade germanium-containing flue dust.

[0006] The embodiment of the present invention provides a method for selectively recovering germanium from germanium-containing smoke by flash boiling chlorination, comprising the following steps:

[0007] (1) Chlorination: Add germanium-containing smoke to a reactor, introduce chlorine gas into the reactor, and perform boiling chlorination reaction at a certain temperature to obtain a mixed flue gas containing gaseous germanium tetrachloride, gaseous silicon tetrachloride, and chlorine gas, and the chloride slag containing unreacted oxides is discharged from the bottom of the reactor;

[0008] (2) Dust collection: The mixed flue gas obtained in step (1) enters a cyclone separator along with the air flow to remove fine smoke particles in the mixed flue gas;

[0009] (3) Condensation: passing the mixed flue gas treated by dust collection in step (2) into a multi-stage condensation device to obtain a liquid mixture of AlCl3 and FeCl3, a liquid mixture of GeCl4 and SiCl4, and tail gas;

[0010] (4) Refining: The liquid mixture of GeCl4 and SiCl4 obtained in step (3) is passed into a distillation device for separation to obtain gaseous SiCl4 and liquid GeCl4, respectively.

[0011] Furthermore, the recovery method also includes recycling of chlorine gas, and the specific steps are as follows:

[0012] S1. Detect the CO2 concentration of the tail gas in step (3). When the CO2 concentration reaches 30%, perform a CO2 adsorption separation operation to obtain chlorine gas with a concentration of >95%;

[0013] S2, returning the chlorine gas purified in step S1 to step (1) to participate in the chlorination reaction.

[0014] Specifically, the germanium-containing smoke contains, by mass fraction, Ge: 0-5%, Al2O3: 10-20%, SiO2: 30-40%, CaO: 10-13%, Fe2O3: 10-20%, and the rest are impurities.

[0015] Preferably, the reactor in step (1) is a fluidized bed reactor.

[0016] Exemplarily, the boiling chlorination reaction in step (1) is carried out at a temperature of 600 to 1100° C., a reaction time of 1 to 10 min, and is carried out under normal pressure.

[0017] Specifically, the flow rate of chlorine gas introduced into the reactor in step (1) is 0.5 to 2.5 m / s.

[0018] Furthermore, the multi-stage condensation device in step (3) is a three-stage condenser.

[0019] Specifically, the mixed flue gas is first subjected to the first stage of condensation to reduce the temperature to 100-150°C to obtain a liquid mixture of AlCl3 and FeCl3; then the second stage of condensation is performed to reduce the temperature to 50-70°C, and finally the third stage of condensation is performed to reduce the temperature to below 10°C. After the second and third stages of condensation, a liquid mixture of GeCl4 and SiCl4 and tail gas are obtained.

[0020] Furthermore, the distillation equipment in step (4) is a plate distillation tower.

[0021] Exemplarily, the distillation process in step (4) is carried out under normal pressure, and the top temperature of the tower is 60-75°C and the bottom temperature of the tower is 85-125°C during distillation.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1. The present invention uses low-grade germanium-containing smoke (germanium content <5%) as raw material for germanium recovery, and adopts a process route of boiling chlorination reaction-dust collection-multi-stage condensation-distillation under normal pressure; accurately controls the reaction temperature and chlorine partial pressure of the chlorination reaction system to ensure that the chlorination efficiency of germanium oxide in the germanium-containing smoke is higher than the chlorination efficiency of other oxides in the smoke, thereby achieving preliminary separation. For the mixed flue gas that has been initially separated, the present invention realizes effective separation of germanium tetrachloride and other chlorides through multi-stage condensation-distillation, and the raw chlorine gas after separation can be returned to the chlorination system for recycling, thereby achieving continuous production operation, short process, simple operation, and low cost.

[0024] 2. The present invention realizes efficient separation of germanium tetrachloride from other chlorides by optimizing the multi-stage condensation temperature gradient setting, and finally obtains germanium tetrachloride with a purity of >90% by distillation and purification, thereby efficiently completing the recovery of germanium from low-grade germanium-containing smoke.

[0025] 3. The present invention uses germanium-containing smoke as raw material for germanium recovery, adopts chlorine as chlorinating agent, and utilizes the carbonaceous component of the smoke itself. The synergistic effect of the strong corrosiveness and oxidizing property of chlorine and the reducibility and strong oxygen binding ability of the carbonaceous component effectively improves the situation that GeO2 is wrapped by SiO2 and cannot be recovered by chlorination, resulting in a low recovery rate, thereby ensuring a high germanium recovery rate of more than 85%.

[0026] 4. The present invention adopts a gas-solid reaction system of chlorine and solid metal oxide to carry out boiling chlorination reaction under normal pressure, the reaction temperature is 600-1100°C, and the reaction time is only 1-10 minutes, which greatly improves production efficiency and reduces reaction energy consumption.

[0027] 5. The present invention uses germanium-containing smoke as raw material for germanium recovery, adopts chlorine chlorination technology, and the reaction system is a gas-solid reaction system. No acid or alkali solution is involved in the process, which solves the problem of high acid consumption and large amount of waste residue and waste liquid discharge in traditional germanium recovery methods.

[0028] 6. The present invention adopts a gas-solid reaction system of chlorine and solid metal oxide to carry out boiling chlorination reaction under normal pressure. By accurately controlling reaction conditions such as reaction temperature and chlorine partial pressure, the chlorination reaction of solid germanium oxide is effectively promoted, so that it is converted into gaseous chloride and volatilizes from the system, while most of other impurity elements remain in the system in solid state, thereby achieving the purpose of preliminary enrichment and purification of germanium; accurate control of the reaction temperature is conducive to improving the selectivity of the chlorination reaction of germanium oxide, and the recovery of germanium in low-grade germanium-containing smoke also maintains a high recovery rate, and the comprehensive recovery rate of germanium is 85-92%.

[0029] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0031] Figure 1 The process flow chart of recovering germanium from germanium-containing smoke of the present invention is as follows;

[0032] Figure 2 The figure is a relationship diagram between Gibbs free energy and temperature for the chlorination reaction of the main phase of germanium-containing soot in the present invention. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0034] Germanium-containing coal dust formed by coal combustion is the main raw material for industrial germanium extraction. Germanium mainly exists in the form of GeO2, which is difficult to volatilize. The process method for extracting germanium is mainly chlorination distillation. The presence of germanium-silicon eutectic hinders chlorination distillation, making it difficult to efficiently separate and recover germanium. Especially for dust with low germanium grade (germanium content <5%), the use of liquid chlorinating agent requires a large amount of hydrochloric acid, produces a large amount of waste acid, waste liquid and residue, which puts pressure on the environment. The use of solid chlorinating agent causes germanium loss in each link, resulting in a relatively low germanium recovery rate. Other technologies such as vacuum reduction-chlorination distillation technology and heating reduction-chlorination distillation technology have the problems of high reaction temperature and high energy consumption, while high temperature and high pressure carbon tetrachloride reaction-chlorination distillation technology is only suitable for the treatment of high-quality germanium dust with a germanium content of 9.5% to 44.1%. The existing process technology does not solve the problems of high acid consumption, large discharge of waste residues and waste liquids, and low germanium recovery rate.

[0035] The existing boiling chlorination reaction is mainly used to recover metal or non-metallic elements in ores. The ore materials need to be crushed and then sent to the fluidized bed reactor. The flow characteristics and reaction efficiency of the materials in the boiling chlorination bed are affected by many complex factors. For example, the particle size, shape and size distribution of the materials have a significant impact on the fluid mechanics behavior. The key process parameters to be controlled are bed establishment, bed height control, gas distribution / distribution methods in the reaction section, transition section, and expansion section, etc.

[0036] There are significant differences in the fluid dynamics behavior between germanium-containing coal dust and crushed ore materials. Therefore, targeted research is needed to achieve the selective recovery of germanium from germanium-containing dust by boiling chlorination, especially the recovery of germanium from low-grade germanium-containing dust (germanium content <5%), which is more challenging.

[0037] A specific embodiment of the present invention discloses a method for selectively recovering germanium from germanium-containing smoke by flash boiling chlorination, such as Figure 1 As shown, the following steps are included:

[0038] (1) Chlorination: Add germanium-containing smoke to a reactor, introduce chlorine gas into the reactor, and perform boiling chlorination reaction at a certain temperature to obtain a mixed flue gas containing gaseous germanium tetrachloride, gaseous silicon tetrachloride, and chlorine gas, and the chloride slag containing unreacted oxides is discharged from the bottom of the reactor;

[0039] (2) Dust collection: The mixed flue gas obtained in step (1) enters a cyclone separator along with the air flow to remove fine smoke particles in the mixed flue gas;

[0040] (3) Condensation: passing the mixed flue gas treated by dust collection in step (2) into a multi-stage condensation device to obtain a liquid mixture of AlCl3 and FeCl3, a liquid mixture of GeCl4 and SiCl4, and tail gas;

[0041] (4) Refining: The liquid mixture of GeCl4 and SiCl4 obtained in step (3) is passed into a distillation device for separation to obtain gaseous SiCl4 and liquid GeCl4, respectively.

[0042] Furthermore, the method for selectively recovering germanium also includes recycling chlorine gas, and the specific steps are as follows:

[0043] S1. Collect the tail gas in step (3) to detect the CO2 concentration. If the cumulative concentration reaches 30%, perform a CO2 adsorption separation operation to obtain chlorine gas with a concentration of >95%;

[0044] S2, returning the chlorine gas purified in step S1 to step (1) to participate in the chlorination reaction.

[0045] It should be noted that the germanium-containing smoke has a germanium content of 0-5% by mass, of which Al2O3 is 10-20%, SiO2 is 30-40%, CaO is 10-13%, Fe2O3 is 10-20%, and the rest is impurities such as MgO.

[0046] Preferably, the reactor in step (1) is a fluidized bed reactor.

[0047] Specifically, the boiling chlorination reaction in step (1) is carried out at a temperature of 600 to 1100° C., a reaction time of 1 to 10 min, and is carried out under normal pressure;

[0048] Preferably, the temperature of the boiling chlorination reaction in step (1) is 600-1100° C. and the reaction time is 120 min to improve the reaction efficiency.

[0049] Specifically, the flow rate of chlorine gas introduced into the reactor in step (1) is 0.5 to 2.5 m / s.

[0050] Furthermore, the main chemical reaction involved in the boiling chlorination reaction is mainly the chlorination reaction between gas phase chlorine and solid phase metal oxide, including:

[0051] GeO2+2Cl2+C=GeCl4+CO2;

[0052] Al2O3+3Cl2+1.5C=2AlCl3+1.5CO2;

[0053] SiO2+2Cl2+C=SiCl4+CO2;

[0054] CaO+Cl2+0.5C=CaCl2+0.5CO2;

[0055] Fe2O3+3Cl2+1.5C=2FeCl3+1.5CO2;

[0056] For the above-mentioned gas-solid reaction system, by precisely controlling the reaction conditions, the chlorination reaction of solid germanium oxide can be promoted, so that it is converted into gaseous chloride and volatilizes from the system, while most of the other impurity elements remain in the system in solid state, thereby achieving the purpose of preliminary enrichment and purification of germanium; Figure 2 As shown, as the reaction temperature increases, germanium oxide undergoes chlorination reaction preferentially over iron oxide and aluminum oxide, and the corresponding equilibrium chlorine partial pressure is also lower. If the temperature continues to rise, aluminum oxide will chlorinate preferentially over germanium oxide, and the equilibrium chlorine partial pressure is lower than that of germanium oxide. Therefore, the reaction temperature is precisely controlled within the temperature range where germanium oxide preferentially chlorinates, and the chlorine partial pressure is controlled within the range of higher than germanium oxide but lower than the equilibrium chlorine partial pressure of iron oxide and aluminum oxide, which can effectively improve the selectivity of the chlorination reaction of germanium oxide. Specifically, the chlorine partial pressure is controlled at 0.5 to 1 atmosphere by introducing oxygen into the reaction system.

[0057] Under the reaction conditions of step (1), during the flash boiling chlorination process of germanium-containing smoke, the chlorination efficiency of germanium oxide in the germanium-containing smoke is greater than 85%, the chlorination efficiency of aluminum oxide is less than 10%, and the chlorination efficiency of silicon oxide is less than 5%.

[0058] It should be noted that before the flue gas enters the multi-stage condensation device for condensation and separation, cyclone dust removal is performed to remove the smoke particles. On the one hand, it effectively reduces the load and wear of the condensation device, extends its service life, prevents the pipes and heat exchange surfaces inside the condensation device from being blocked, and reduces the cleaning and maintenance frequency of the condensation device, thereby reducing maintenance costs; on the other hand, it prevents dust from forming an insulating layer on the heat exchange surface, thereby improving the heat exchange efficiency of the condensation device.

[0059] Furthermore, in step (3), the balance between condensation efficiency and energy consumption is comprehensively considered, and the multi-stage condensation device is determined to be a three-stage condenser. The mixed flue gas is first subjected to the first-stage condensation to reduce the temperature to 100-150°C to obtain a liquid mixture of AlCl3 and FeCl3; the second-stage condensation is then performed to reduce the temperature to 50-70°C, and finally the third-stage condensation is performed to reduce the temperature to below 10°C. After the second and third stages of condensation, a liquid mixture of GeCl4 and SiCl4 and tail gas are obtained; wherein the liquid mixture of GeCl4 and SiCl4 enters the distillation equipment for refining, and the tail gas is subjected to chlorine purification and recycling.

[0060] Furthermore, the distillation equipment in step (4) is a plate distillation tower;

[0061] Specifically, the distillation process in step (4) is carried out under normal pressure, the tower top temperature is 60-75° C., and the tower bottom temperature is 85-125° C. During the distillation, the volatility of silicon tetrachloride is higher than that of germanium tetrachloride. The gas phase product obtained at the top is silicon tetrachloride, and the liquid phase product at the bottom is germanium tetrachloride, wherein the purity of germanium tetrachloride is 90-95%;

[0062] The high-purity germanium tetrachloride product can be hydrolyzed or metal thermally reduced to obtain metallic germanium.

[0063] In one possible design, germanium tetrachloride is passed into deionized water and stirred continuously to hydrolyze and produce germanium dioxide precipitate. After filtering, washing and drying, H2 thermal reduction is used to obtain metallic germanium with a purity of >90%. The comprehensive recovery rate of germanium is 85-92%.

[0064] Furthermore, the chlorine gas is recycled and reused. During the circulation process, the chlorine gas will be mixed with CO2 impurity gas produced by the chlorination reaction. After multiple cycles, CO2 accumulates in the gas phase. When the concentration reaches 30%, the CO2 adsorption separation operation is performed, and the purified chlorine gas is returned to the chlorination reaction section again;

[0065] In one possible design, molecular sieve is used as adsorbent to achieve the adsorption separation of CO2.

[0066] In summary, the chlorination reaction of the germanium recovery method of the present invention is short in time and has high selectivity. It can achieve a higher germanium recovery rate while maintaining a lower chlorination efficiency for other components in the smoke. The comprehensive germanium recovery rate is 85-92%. No waste acid or waste liquid is generated in the process, and the used chlorine is recycled after separation.

[0067] The method for selectively recovering germanium from germanium-containing smoke by flash boiling chlorination of the present invention is described below with reference to specific embodiments.

[0068] Example 1

[0069] This embodiment provides a method for efficiently recovering germanium from germanium-containing smoke.

[0070] The main components of smoke are: GeO2: 1.1%, Al2O3: 16%, SiO2: 38%, CaO: 13%, Fe2O3: 17%;

[0071] The particle size distribution of smoke dust is as follows: 1-3μm accounts for 20%, 3-50μm accounts for 70%, and 50-1000μm accounts for 10%.

[0072] The recycling process mainly includes the following steps:

[0073] (1) Chlorination: The above-mentioned germanium-containing smoke is added to a fluidized bed reactor, and chlorine gas is introduced into the fluidized bed reactor. The gas flow rate is maintained at 0.5 m / s, the chlorine partial pressure is controlled at 0.9 atmospheres, the chlorination temperature is 700° C., the flash boiling chlorination time is 10 min, the chlorination efficiency of germanium oxide in the germanium-containing smoke is 85%, the chlorination efficiency of aluminum oxide is 6%, and the chlorination efficiency of silicon oxide is 3%. The above-mentioned chlorides leave the reaction area with the smoke, and the remaining substances remain in the chlorinated slag in the form of oxides and are discharged from the bottom;

[0074] (2) Dust collection: the mixed gas phase obtained in step (1) and the finer smoke particles carried away by the chlorine gas are passed into a cyclone separator for cyclone dust collection;

[0075] (3) Condensation: The metal chloride and chlorine gas mixture obtained in step (2) is passed into a three-stage condenser for condensation, wherein the temperature of the mixed gas is reduced to 100-120° C. by the first stage condensation, the temperature is reduced to 50-70° C. by the second stage condensation, and the temperature is reduced to below 10° C. by the third stage condensation; after the first stage condensation, chlorination products with higher liquefaction temperatures such as AlCl3 and FeCl3 are first liquefied and separated, and after the second and third stage condensations, GeCl4 and SiCl4 are liquefied to form a mixed liquid phase of GeCl4, SiCl4, etc.;

[0076] The chlorine gas is returned to the chlorination reaction section for recycling. During the recycling process, the chlorine gas will be mixed with CO2 impurity gas produced by the chlorination reaction. After multiple cycles, CO2 accumulates in the gas phase. When the concentration reaches 30%, CO2 adsorption separation operation is performed, and the purified chlorine gas is returned to the chlorination reaction section again.

[0077] (4) Purification: The mixed liquid phase obtained in step (3) is passed into a plate distillation tower under normal pressure. The tower top temperature is 60-75° C. and the tower bottom temperature is 85-125° C. During the distillation, the volatility of silicon tetrachloride is higher than that of germanium tetrachloride. The gas phase product obtained at the top is silicon tetrachloride, and the liquid phase product at the bottom is germanium tetrachloride, thereby obtaining high-purity germanium tetrachloride.

[0078] The purity of germanium tetrachloride is 95%. Germanium tetrachloride is reduced to single germanium by H2 reduction method. Based on the content of germanium oxide in the smoke, the germanium recovery rate is 85%.

[0079] Embodiments 2 to 4

[0080] This embodiment provides a method for efficiently recovering germanium from germanium-containing smoke.

[0081] The main components of the smoke and the distribution of the smoke particle size are the same as those in Example 1.

[0082] The main steps of the recovery process are the same as those in Example 1, except that the chlorination reaction conditions in step (1) are controlled differently. The specific parameters are shown in Table 1.

[0083] The purity of germanium tetrachloride and the germanium recovery rate are shown in Table 1.

[0084] Example 5

[0085] This embodiment provides a method for efficiently recovering germanium from germanium-containing smoke.

[0086] The main components of the smoke and the distribution of the smoke particle size are the same as those in Example 1.

[0087] The main steps of the recovery process are the same as those of Example 1, except that in step (3), the temperature is reduced to 130-150°C after the first stage condensation, and the temperature is reduced to below 10°C after the second and third stages condensation, forming a mixed liquid phase of GeCl4, SiCl4, etc.

[0088] The purity of germanium tetrachloride and the germanium recovery rate are shown in Table 1.

[0089] Comparative Examples 1 to 3

[0090] This embodiment provides a method for efficiently recovering germanium from germanium-containing smoke.

[0091] The main components of the smoke and the distribution of the smoke particle size are the same as those in Example 1.

[0092] The main steps of the recovery process are the same as those in Example 1, except that the chlorination reaction conditions in step (1) are controlled differently. The specific parameters are shown in Table 1.

[0093] The purity of germanium tetrachloride and the germanium recovery rate are shown in Table 1.

[0094] Comparative Example 4

[0095] This embodiment provides a method for efficiently recovering germanium from germanium-containing smoke.

[0096] The main components of the smoke and the distribution of the smoke particle size are the same as those in Example 1.

[0097] The main steps of the recovery process are the same as those of Example 1, except that step (3) uses a first-stage condensation, and the temperature is directly reduced to below 10°C to form a mixed liquid phase of GeCl4, SiCl4, etc.

[0098] The purity of germanium tetrachloride and the germanium recovery rate are shown in Table 1.

[0099] Table 1 Chlorination reaction conditions and germanium recovery in examples and comparative examples

[0100]

[0101]

[0102] As can be seen from Table 1, in Example 1 to Example 4, within the chlorination temperature range designed by the present invention, as the chlorination temperature increases, the chlorination efficiency of germanium chloride increases, the germanium recovery rate increases, and the required chlorination time is shortened. In practical application, the chlorination temperature should be selected by comprehensively considering the reaction energy consumption, reaction time and the demand for recovery rate;

[0103] From Comparative Example 1 and Examples 1 to 4, it can be seen that after exceeding the chlorination temperature range designed by the present invention, although the chlorination efficiency of germanium chloride increases, the chlorination efficiency of aluminum chloride and silicon chloride increases more, resulting in a decrease in the final recovery efficiency of germanium and a large energy consumption;

[0104] Comparing Comparative Examples 2 to 3 with Example 1, under the same reaction time, when the chlorination temperature is lower than the range designed by the present invention, the chlorination efficiency of germanium chloride and the final recovery efficiency of germanium are extremely low;

[0105] It can be seen from Examples 1 and 5 that the first-stage condensation temperature increases and the purity of germanium chloride decreases;

[0106] It can be seen from Example 1 and Comparative Example 4 that if only one-stage condensation is used, the temperature is directly reduced to below 10° C., the condensation separation effect is poor, and the purity of germanium chloride is extremely low.

[0107] In summary, the chlorination reaction of the germanium recovery method of the present invention is short in time and has high selectivity. It can achieve a higher germanium recovery rate while maintaining a lower chlorination efficiency for other components in the smoke. The comprehensive germanium recovery rate is 85-92%. No waste acid or waste liquid is generated in the process, and the used chlorine is recycled after separation.

[0108] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for selectively recovering germanium from germanium-containing smoke by flash boiling chlorination, characterized in that: The following steps are involved: (1) Chlorination: Add germanium-containing smoke to a reactor, introduce chlorine gas into the reactor, and perform boiling chlorination reaction at a certain temperature to obtain a mixed flue gas containing gaseous germanium tetrachloride, gaseous silicon tetrachloride, and chlorine gas, and the chloride slag containing unreacted oxides is discharged from the bottom of the reactor; (2) Dust collection: The mixed flue gas obtained in step (1) enters a cyclone separator along with the air flow to remove fine smoke particles in the mixed flue gas; (3) Condensation: passing the mixed flue gas treated by dust collection in step (2) into a multi-stage condensation device to obtain a liquid mixture of AlCl3, FeCl3, a liquid mixture of GeCl4, SiCl4 and tail gas respectively; (4) Refining: The liquid mixture of GeCl4 and SiCl4 obtained in step (3) is passed into a distillation device for separation to obtain gaseous SiCl4 and liquid GeCl4, respectively.

2. The method according to claim 1, characterized in that It also includes the recycling of chlorine gas, and the specific steps are as follows: S1. Detect the CO2 concentration of the tail gas in step (3). When the CO2 concentration reaches 30%, perform a CO2 adsorption separation operation to obtain chlorine gas with a concentration of >95%; S2, returning the chlorine gas purified in step S1 to step (1) to participate in the chlorination reaction.

3. The method according to claim 1, characterized in that The germanium-containing smoke comprises, by mass fraction, Ge: 0-5%, Al2O3: 10-20%, SiO2: 30-40%, CaO: 10-13%, Fe2O3: 10-20%, and the rest are impurities.

4. The method according to claim 1, characterized in that: The reactor in step (1) is a fluidized bed reactor.

5. The method according to claim 4, characterized in that The boiling chlorination reaction in step (1) is carried out at a temperature of 600 to 1100° C., a reaction time of 1 to 10 minutes, and is carried out under normal pressure.

6. The method according to claim 4, characterized in that The flow rate of chlorine gas introduced into the reactor in step (1) is 0.5 to 2.5 m / s, and the partial pressure of chlorine gas is 0.5 to 1 atmosphere.

7. The method according to claim 1, characterized in that The multi-stage condensation device in step (3) is a three-stage condenser.

8. The method according to claim 7, characterized in that The mixed flue gas is first subjected to the first stage of condensation to reduce the temperature to 100-150°C to obtain a liquid mixture of AlCl3 and FeCl3; the temperature is then reduced to 50-70°C by the second stage of condensation, and finally the temperature is reduced to below 10°C by the third stage of condensation. After the second and third stages of condensation, a liquid mixture of GeCl4 and SiCl4 and tail gas are obtained.

9. The method according to claim 1, characterized in that: The distillation equipment in step (4) is a plate distillation tower.

10. The method according to claim 9, characterized in that The distillation process in step (4) is carried out under normal pressure, the tower top temperature is 60-75°C, and the tower bottom temperature is 85-125°C during distillation.

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