CN117025969A - Vacuum furnace and method for extracting lead from waste CRT cone glass - Google Patents

Abstract

The application discloses a vacuum furnace and a method for extracting lead from waste CRT cone glass, belonging to the fields of high pollution control and treatment of waste lead-containing glass and comprehensive recovery of secondary resources. Firstly, placing a granular carbonaceous reducing agent in an upper layer distributing device of a vacuum furnace for carbothermic reduction reaction, placing conical glass in a lower layer distributing device, and sealing the vacuum furnace; and (3) under the conditions of 5-10 Pa and 1300 ℃ of vacuum chamber pressure, preserving heat for 120min, volatilizing lead oxide in the conical glass, and performing carbothermic reaction on the volatilized lead oxide and a carbonaceous reducing agent in the process of passing through a carbon layer at the upper part of the graphite crucible to generate gaseous metallic lead, and condensing the gaseous metallic lead in a condensing disc. After the heat preservation is finished, naturally cooling, obtaining metallic lead in a condensation area, wherein the purity of the metallic lead is more than 99%, and lead oxide in residual glass is effectively removed, so that the metallic lead can be used for preparing novel lead-free glass, building materials and ceramic materials, and harmless treatment and comprehensive utilization of resources of the conical glass are realized.

Description

A vacuum furnace and method for extracting lead from waste CRT cone glass

This application is a divisional application with the filing date being August 20, 2018, the application number being 201810946758.2, and the invention title being "A method for extracting lead from waste CRT cone glass".

Technical field

The invention relates to a vacuum furnace and a method for extracting lead from waste CRT cone glass, and belongs to the field of high pollution control and treatment of waste lead-containing glass and comprehensive recovery of secondary resources.

Background technique

Especially since the 21st century, with the rapid development of electronic technology and the rapid rise of the flat-panel display industry, a large number of cathode ray tube (CRT) cone glass used in display screens for TVs and computers have been eliminated, and my country has entered the scrapping phase of lead-containing CRT cone glass. peak period. One forecast study estimates that the amount of discarded CRT cone glass across Asia will increase to approximately 1,500 tons by 2020. Moreover, cone glass mainly contains a large amount of silica, lead oxide, etc., of which the silica content is about 50%, and the lead oxide content is about 20%, so the lead oxide in cone glass is an important source of lead. One of the sources. At the same time, because CRT cone glass contains heavy metal lead, it is considered to be hazardous electronic waste. The key to safe treatment and disposal of waste CRT cone glass is to treat and dispose of the lead oxide in it. If it is not treated properly, it will affect the ecological environment such as water sources and soil. It will cause incalculable harm and endanger human health. Therefore, the removal and comprehensive utilization of lead-containing resources from discarded CRT cone glass is a difficult problem that must be solved in the current processing and disposal of electronic waste in my country. At present, the detoxification process and comprehensive recycling technology of secondary resources in cone glass are not mature enough. Therefore, reasonable resource recycling methods and approaches for waste CRT glass have become an urgent problem in our country and even the world.

In recent years, many researchers in our country have proposed a method based on pyrometallurgy of cone glass to extract metallic lead based on the principles of green environmental protection, economy, and process feasibility, which has greatly promoted the secondary recovery and utilization of lead resources in waste CRT cone glass. However, there are still many problems, such as low lead extraction rate, complicated process, environmental pollution problems, etc. Ma Zhilai et al. invented a method and device for recycling metallic lead from waste CRT cone glass (Application No. 201310361538.0, 201320505904.0). This method is to mix waste CRT cone glass, lead concentrate, lead oxide ore and coke in a certain proportion, and mix them in a blast furnace Through smelting, crude lead, slag and soot can be obtained. The crude lead yield can reach 20%, the lead content in the crude lead can reach 98.52%, and the lead content in the slag is more than 1%. This process combines cone glass with lead-containing waste. Co-processing is beneficial to the comprehensive treatment of waste, but its lead recovery rate is low and a large amount of waste lead-containing slag and smoke will be produced (accounting for about 80%). Application No. 201210345035. The mixture is then purified by flotation or chemical methods. The extraction rate of lead in cone glass through this method is about 60%.

Contents of the invention

The object of the present invention is to provide a vacuum furnace and a method for extracting lead from waste CRT cone glass, efficiently remove lead oxide in the cone glass, and simultaneously recover the metallic lead, thereby achieving harmless treatment of waste lead-containing CRT cone glass. and comprehensive utilization.

The invention provides a vacuum furnace. The vacuum furnace includes a lower distribution device, an upper distribution device, and a graphite condensation device. A lead oxide volatilization chamber is provided between the lower distribution device and the upper distribution device. The upper distribution device and There is a gaseous lead volatilization chamber and a condensation chamber between the graphite condensation devices;

The upper distribution device is a porous stainless steel mesh, which is fixed on the side wall of the reactor through slots; the gaseous lead volatilization chamber and the condensation chamber are separated by a partition, and the partition is provided with air holes.

The present invention also provides a method for extracting lead from waste CRT cone glass, which is carried out using the vacuum furnace described in the above solution, and specifically includes the following steps:

(1) Place the cone glass in the lower distribution device of the vacuum furnace, place the carbonaceous reducing agent in the upper distribution device, and seal the vacuum furnace;

(2) Evacuate the vacuum furnace in a cold state. When the cold pressure is less than 30Pa, start other operations. Raise the temperature to 1300℃ at a heating rate of 10℃/min, heat it, and keep it warm for 120min. During the hot state of the vacuum furnace, Thermal pressure is 5~10Pa;

(3) After the heat preservation is completed, the high-temperature furnace body is naturally cooled to room temperature. After the furnace body is naturally cooled to room temperature, the condensate lead is collected in the condensation chamber, and the deleaded glass is obtained in the volatilization chamber.

Preferably, the ratio of the carbon content in the carbonaceous reducing agent to the lead oxide content in the cone glass is greater than 0.1%.

Preferably, the lead oxide content in the cone glass is 28.54%.

Preferably, the composition of the deleaved glass is: SiO ₂ 64.87%, PbO 0.03%, K ₂ O 11.12%, Na ₂ O 5.89%, CaO 4.96%, SrO 3.36%, Al ₂ O ₃ 3.47% , MgO 2.88%, BaO 2.75%, others 0.67%.

The present invention also provides the lead condensate obtained by the method described in the above solution, and the particle size of the lead condensate is less than 50 μm.

The principle of the invention: when the system pressure reaches 5~15Pa and the temperature is greater than 1150°C, the -O-P-O-Si-O- network structure in the cone glass is destroyed, causing the lead oxide to release and interact with the carbon placed on the upper part of the crucible. The metal lead is obtained through the layer reaction. Since the system reaches the saturated vapor pressure of the metal lead, the metal lead volatilizes and condenses on the condensation tray, thus realizing the fundamental purpose of recycling the metal lead of the present invention; the reaction formulas are:

PbSiO ₃ →PbO(s)+SiO ₂ (s)(1)

PbO(s)→PbO(l)→PbO(g)(2)

PbO(g)+C(s)→Pb(s)+CO(g)(3)

Pb(s)→Pb(l)→Pb(g)(4)

Beneficial effects of the present invention:

(1) The present invention designs a new type of vacuum volatilization and carbothermal reduction device, which causes the lead oxide volatilized in the cone glass to undergo a carbothermal reduction reaction with the carbon layer in the upper part of the device, and is mixed with the traditional carbonaceous reducing agent and the cone glass. Compared with the reduction process, it can effectively avoid lead contamination of the product by other substances in the cone glass.

(2) The present invention realizes the carbothermal reduction reaction of gaseous lead oxide through this new device structure.

(3) The present invention realizes the one-step method of recovering metallic lead from cone glass. Compared with the existing treatment process, the process flow is shorter and the operation is simple; there are no additives in the process of processing lead-containing cone glass, which reduces secondary pollution. And the whole process is carried out in a completely sealed vacuum furnace, which is beneficial to environmental protection and labor health.

(4) The present invention achieves efficient removal of lead from lead-containing cone glass. When the heat treatment temperature is 1300°C and the heat preservation is performed for 120 minutes, the lead removal rate can reach 99.85%, and the purity of the recovered metallic lead can reach more than 99.45%. At the same time, residual glass containing 0.03% lead oxide is obtained, which can be used to prepare new lead-free glass, building materials, ceramic materials, etc.

Description of the drawings

Figure 1 is a process flow diagram of the present invention;

Figure 2 shows scanning electron microscope images of metallic lead recovered at different temperatures;

Figure 3 is a schematic diagram of the vacuum furnace material layer device.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the present invention is not limited to the content described.

The device used in Embodiments 1 to 5 of the present invention is shown in Figure 3, including a lower distribution device, an upper distribution device, and a graphite condensation device. A lead oxide volatilization chamber in a cone glass is arranged between the lower distribution device and the upper distribution device. The upper distribution device There is a gaseous lead volatilization chamber and a condensation chamber between the graphite condensation device; the upper distribution device is a porous stainless steel mesh, which is fixed on the side wall of the reactor through a slot; the gaseous lead volatilization chamber and the condensation chamber are separated by a partition , there are air holes on the partition.

Example 1

First, clean the surface of the cone glass, and use a jaw crusher to break the large cone glass into block cone glass (50g, in which the lead oxide content is 28.54%) suitable for the vacuum furnace; the granular carbonaceous reducing agent is placed on the upper layer of the vacuum furnace. The device is used for carbothermal reduction reaction, and the carbon content in the carbonaceous reducing agent is 5g. The cone glass is placed in the lower distribution device; vacuum carbothermal reduction treatment is performed, the temperature is raised to 1150°C, the heating rate is 5°C/min, and the system heat The state pressure is in the range of 5 to 8 Pa, and the temperature is maintained for 30 minutes. After the furnace body is naturally cooled to room temperature, metallic lead is obtained in the condensation tray, and the residual glass after removing lead oxide is obtained in the volatilization chamber.

The element content of the residual glass was analyzed by X-ray fluorescence spectrometer and the recovery rate of metallic lead was 43.34%. The purity of volatile metallic lead was found to be 99.23% through chemical analysis.

Example 2

First, clean the surface of the cone glass, and use a jaw crusher to break the large cone glass into block cone glass (50g, in which the lead oxide content is 28.54%) suitable for the vacuum furnace; the granular carbonaceous reducing agent is placed on the upper layer of the vacuum furnace. The device is used for carbothermal reduction reaction and the carbon content of the carbonaceous reducing agent is 15g. The cone glass is placed in the lower distribution device; vacuum carbothermal reduction treatment is performed, the temperature is raised to 1300°C, the heating rate is 10°C/min, and the system thermal state Within the pressure range of less than 10 Pa, keep the temperature for 30 minutes. After the furnace body is naturally cooled to room temperature, metallic lead is obtained in the condensation tray, and the residual glass after removing lead oxide is obtained in the volatilization chamber.

The element content of the residue was analyzed by X-ray fluorescence spectrometer and the removal rate of metallic lead was 92.71%. The purity of volatile metallic lead was found to be 99.12% through chemical analysis.

Example 3

First, clean the surface of the cone glass, and use a jaw crusher to break the large cone glass into block cone glass (50g, in which the lead oxide content is 28.54%) suitable for the vacuum furnace; the granular carbonaceous reducing agent is placed on the upper layer of the vacuum furnace. The device is used for carbothermal reduction reaction and the carbon content of the carbonaceous reducing agent is 20g. The cone glass is placed in the lower distribution device; vacuum carbothermal reduction treatment is performed, the temperature is raised to 1400°C, the heating rate is 20°C/min, and the system thermal state The pressure is in the range of 10 to 15 Pa, and the temperature is maintained for 30 minutes. After the furnace body is naturally cooled to room temperature, metallic lead is obtained in the condensation tray, and the residual glass after removing lead oxide is obtained in the volatilization chamber.

The element content of the residue was analyzed by X-ray fluorescence spectrometer and the removal rate of metallic lead was 99.80%. The purity of volatile metallic lead was found to be 99.40% through chemical analysis.

Example 4

First, clean the surface of the cone glass, and use a jaw crusher to break the large cone glass into block cone glass (50g, in which the lead oxide content is 28.54%) suitable for the vacuum furnace; the granular carbonaceous reducing agent is placed on the upper layer of the vacuum furnace. The device is used for carbothermal reduction reaction and the carbon content of the carbonaceous reducing agent is 15g. The cone glass is placed in the lower distribution device; vacuum carbothermal reduction treatment is performed, and the temperature is raised to 1300°C at a heating rate of 10°C/min. The system heat The state pressure is less than 10 Pa, and the temperature is maintained for 60 minutes. After the furnace body is naturally cooled to room temperature, metallic lead is obtained in the condensation tray, and the residual glass after removing lead oxide is obtained in the volatilization chamber.

The element content of the residue was analyzed by X-ray fluorescence spectrometer and it was found that the removal of lead oxide in the cone glass was 99.45%. The purity of the volatile metallic lead was found to be 99.36% through chemical analysis.

Example 5

First, clean the surface of the cone glass, and use a jaw crusher to break the large cone glass into block cone glass (50g, in which the lead oxide content is 28.54%) suitable for the vacuum furnace; the granular carbonaceous reducing agent is placed on the upper layer of the vacuum furnace. The device is used for carbothermal reduction reaction, and the cone glass is placed in the lower distribution device; vacuum carbothermal reduction treatment is performed, the temperature is raised to 1300°C, the heating rate is 10°C/min, the system thermal pressure is within the range of less than 10Pa, and the temperature is maintained for 120min , after the furnace body is naturally cooled to room temperature, metallic lead is obtained in the condensation pan, and the residual glass after removing lead oxide is obtained in the volatilization chamber;

The element content of the residue was analyzed by X-ray fluorescence spectrometer and it was found that the removal of lead oxide in the cone glass was 99.85%. The purity of the volatile metallic lead was found to be 99.45% through chemical analysis.

In order to verify the influence of different heat treatment temperatures, holding times, etc. on the present invention, element detection was performed on the residual glass in Examples 1 to 5. The results are as shown in Table 1:

Table 1 examines the effects of different heat treatment temperatures on the content of each element in the residual glass

project Example 1 Example 2 Example 3 Example 4 Example 5 SiO ₂ (%) 51.43 62.68 64.35 66.13 64.87 PbO(%) 18.42 3.08 0.08 0.68 0.03 K ₂ O (%) 9.65 10.61 11.02 10.23 11.12 Na ₂ O(%) 5.25 5.74 5.31 5.54 5.89 CaO(%) 4.01 5.55 4.98 5.06 4.96 SrO(%) 3.02 3.11 3.12 3.22 3.36 Al ₂ O ₃ (%) 2.60 3.08 3.92 2.78 3.47 MgO(%) 1.94 2.27 2.45 3.03 2.88 BaO(%) 2.37 2.95 3.13 2.15 2.75 Others(%) 1.04 0.93 1.64 1.18 0.67

It can be seen from Table 1 that with the increase of heat treatment temperature and holding time, the content of lead oxide in the residual glass significantly decreases, that is, the removal effect of lead oxide is significantly improved, and under the optimal conditions (temperature is 1300min, holding time is 120min) The removal of lead oxide is 99.83%.

Figure 2 is a scanning electron microscope picture of metallic lead recovered under different conditions. It can be seen from the picture that the morphology of the lead products obtained under different conditions is basically similar, and the particle size is less than 50 μm.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (6)

1. A vacuum furnace, characterized in that the vacuum furnace includes a lower distribution device, an upper distribution device, and a graphite condensing device. A lead oxide volatilization chamber is provided between the lower distribution device and the upper distribution device. The upper distribution device There is a gaseous lead volatilization chamber and a condensation chamber between the device and the graphite condensation device; The upper distribution device is a porous stainless steel mesh, which is fixed on the side wall of the reactor through slots; the gaseous lead volatilization chamber and the condensation chamber are separated by a partition, and the partition is provided with air holes. 2. A method for extracting lead from waste CRT cone glass, characterized in that it is carried out using a vacuum furnace according to claim 1, specifically including the following steps: (1) Place the cone glass in the lower distribution device of the vacuum furnace, place the carbonaceous reducing agent in the upper distribution device, and seal the vacuum furnace; (2) Evacuate the vacuum furnace in a cold state. When the cold pressure is less than 30Pa, start other operations. Raise the temperature to 1300℃ at a heating rate of 10℃/min, heat it, and keep it warm for 120min. During the hot state of the vacuum furnace, Thermal pressure is 5~10Pa; (3) After the heat preservation is completed, the high-temperature furnace body is naturally cooled to room temperature. After the furnace body is naturally cooled to room temperature, the condensate lead is collected in the condensation chamber, and the deleaded glass is obtained in the volatilization chamber. 3. The method for extracting lead from waste CRT cone glass according to claim 2, characterized in that: the ratio of the carbon content in the carbonaceous reducing agent to the lead oxide content in the cone glass is greater than 0.1%. 4. The method for extracting lead from waste CRT cone glass according to claim 2, characterized in that: the lead oxide content in the cone glass is 28.54%. 5. The method for extracting lead from waste CRT cone glass according to claim 2, characterized in that: the composition of the deleaved glass is: SiO ₂ 64.87%, PbO 0.03%, K ₂ O 11.12%, Na ₂ O 5.89%, CaO 4.96%, SrO 3.36%, Al ₂ O ₃ 3.47%, MgO 2.88%, BaO 2.75%, others 0.67%. 6. The lead condensate obtained by the method according to any one of claims 2 to 5, characterized in that the particle size of the lead condensate is less than 50 μm.