Method for treating waste lead plaster through biomass roasting

Abstract

The invention provides a method for roasting waste lead plaster by utilizing biomass. The method comprises the following steps: respectively drying, crushing and screening the waste lead plaster and the biomass to obtain waste lead plaster powder and biomass powder; carrying out ball milling and mixing on the waste lead plaster powder and the biomass powder to obtain mixed powder; roasting the mixed powder to obtain liquid metal lead and residual solids; and carrying out secondary ball-milling on the residual solid to obtain ball-milled powder, and feeding the ball-milled powder to a lead factory as a lead-producing raw material. The method for treating the waste lead plaster through biomass roasting is low in energy consumption, small in pollution, short in process and relatively low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of secondary resource recycling and reuse, and in particular to a method for treating waste lead paste by roasting biomass. Background Art

[0002] Lead is a precious metal raw material. With the development of the national economy, more than 90% of metal lead is used to produce lead-acid batteries. During the use of lead-acid batteries, the battery's ability to store energy will gradually decrease due to corrosion and passivation. Depending on the quality of the battery, the life span ranges from 2 to 4 years. The number of lead-acid batteries replaced is increasing at a rate of 7% per year. Therefore, the reasonable disposal and recycling of waste lead-acid batteries can ensure environmental safety and promote global sustainable development.

[0003] Waste lead-acid batteries mainly include the following parts: waste electrolyte (11%-30%), lead alloy grid (24%-30%), organic matter (22%-30%), lead paste (30%-40%). The lead paste is a slurry formed by the active material on the plate after multiple charging and discharging, dissolution and crystallization. Since lead sulfate, which accounts for the largest proportion of the lead paste, is difficult to recycle, it has become the focus of research and treatment.

[0004] At present, the technology of recovering lead from lead paste at home and abroad has gradually matured, which can be roughly divided into two types: pyrometallurgy and wet electrolysis. The pyrometallurgy process mainly uses different reducing agents to reduce the lead-containing substances in the lead paste under high temperature conditions, and then further refines to obtain high-purity lead. However, the pyrometallurgy process of lead paste needs to be carried out at a high temperature of 1300℃, and the consumption of reducing agents such as coke is also large, and a large amount of sulfur dioxide will be produced, which will pollute the air. The wet electrolysis process of lead paste mainly uses strong acids such as HCl, H2SiF6 or HBF4 to leach the lead in it, and then recover the lead by electrodeposition. However, in the wet electrolysis process, the lead paste often needs to be desulfurized and pre-reduced in advance, which consumes a large amount of chemical reagents, resulting in excessively high recycling costs, and also produces a large amount of wastewater discharge, causing serious environmental problems.

[0005] Waste biomass has broad application prospects in the reduction roasting strategy due to its advantages such as low price, easy access and carbon balance. Based on the melting point and decomposition temperature of lead sulfate of more than one thousand degrees and its relatively stable chemical properties, if waste biomass can be used as a reducing agent, lead sulfate and lead oxide in waste lead paste can be reduced and treated to recover valuable metallic lead through gas-solid reaction at a lower temperature. This can not only reduce the recycling cost of waste lead paste, but also reduce the impact on the environment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for treating waste lead paste by roasting biomass with low energy consumption, low pollution, short process and low cost.

[0007] In order to solve the above technical problems, the present invention provides a method for treating waste lead paste by roasting biomass, comprising the following steps:

[0008] The waste lead paste and biomass are dried, crushed and sieved to obtain waste lead paste powder and biomass powder respectively;

[0009] The waste lead paste powder and the biomass powder are ball-milled to obtain a mixed powder;

[0010] The mixed powder is roasted to obtain liquid metal lead and residual solid matter;

[0011] The remaining solids are ball-milled for a second time to obtain ball-milled powder which is sent to the lead plant as raw material for lead production.

[0012] Furthermore, the waste lead paste includes waste lead paste obtained by disassembling waste lead-acid batteries, and the biomass includes wheat straw, rice straw, corn straw, reed, bamboo, eucalyptus sawdust, poplar sawdust, willow sawdust and pine sawdust.

[0013] Furthermore, the waste lead paste and biomass are dried in an oven at a drying temperature of 100 to 120° C. for a drying time of 20 to 30 hours.

[0014] Furthermore, the waste lead paste and biomass are dried, crushed and sieved to obtain waste lead paste powder and biomass powder below 200 meshes respectively.

[0015] Furthermore, the mass ratio of the biomass powder and the waste lead paste powder when ball-milled is X:1, wherein 0<X≤5.

[0016] Furthermore, when the mixed powder is roasted, the mixed powder is first placed in a high temperature resistant crucible with a liquid outlet at the bottom and a sealing cover at the top, and then the high temperature resistant crucible is placed in a short kiln, a crucible furnace or a muffle furnace for roasting.

[0017] Furthermore, the mixed powder is calcined at a temperature of 500° C.-1000° C. and for a time of 0.1 h-6 h.

[0018] Furthermore, a container for collecting liquid metal lead is provided at the liquid outlet at the bottom of the high temperature resistant crucible.

[0019] Furthermore, the waste lead paste comprises lead sulfate, lead dioxide, lead oxide and metallic lead.

[0020] Furthermore, the biomass needs to be washed before drying.

[0021] The present invention provides a method for treating waste lead paste by roasting biomass, wherein biomass powder is mixed with waste lead paste powder and roasted at a temperature of 500-1000°C, and reducing gases such as H2, CO, and CH4 generated by pyrolysis of biomass are used to pre-reduce difficult-to-treat lead sulfate and lead dioxide in the waste lead paste into lead sulfide and metallic lead, thereby obtaining liquid metallic lead and residual solids containing lead sulfide at a temperature of 500-1000°C, and finally the residual solids are ball-milled for a second time to obtain ball-milled powder, which is then sent to a lead factory as a raw material for producing metallic lead. The present invention reduces waste lead paste by using widely available and inexpensive waste biomass, so that not only relatively precious metallic lead can be recovered from waste lead paste, but also the residual solids containing lead sulfide obtained by roasting can be returned to the lead factory for repeated reuse, so that not only precious metallic lead can be recovered from waste lead paste, but also the waste lead paste can be reused in the most resource-efficient way. Not only can waste biomass and waste lead paste be fully reused, saving resources and improving economic benefits, but the process also requires lower temperature conditions and energy consumption, and can also reduce SO2 and NO x The emission of pollutants such as carbon dioxide is small, and the pollution is environmentally friendly. It has a good market prospect and is worthy of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for treating waste lead paste by roasting biomass provided in an embodiment of the present invention;

[0023] Figure 2 An X-ray diffraction diagram of waste lead paste used in the method for treating waste lead paste by roasting biomass provided in an embodiment of the present invention;

[0024] Figure 3 An X-ray diffraction diagram of the remaining solids obtained after roasting in the method for treating waste lead paste by roasting biomass provided in an embodiment of the present invention;

[0025] Figure 4 A composition change diagram of a reduction product obtained by roasting in the method for treating waste lead paste by roasting biomass provided in Examples 1-5 of the present invention;

[0026] Figure 5 A composition change diagram of a reduction product obtained by roasting in the method for treating waste lead paste by roasting biomass provided in Examples 6-10 of the present invention;

[0027] Figure 6 This is a physical picture of the residual solid material obtained by roasting in the method for treating waste lead paste by roasting biomass provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] See also Figure 1The present invention provides a method for treating waste lead paste by roasting biomass, comprising the following steps:

[0029] Step 1) The waste lead paste and biomass are dried, crushed and sieved to obtain waste lead paste powder and biomass powder respectively.

[0030] Among them, see Figure 2 It can be seen from the X-ray diffraction (XRD) diagram of the waste lead paste that the waste lead paste includes the waste lead paste obtained by disassembling waste lead-acid batteries, and its components include lead sulfate, lead dioxide, lead oxide and metallic lead.

[0031] Among them, biomass includes carbon-rich waste biomass such as wheat straw, rice straw, corn straw, reeds, bamboo, eucalyptus chips, poplar chips, willow chips and pine chips.

[0032] Among them, the waste biomass needs to be washed with clean water before drying to remove dust and other impurities carried by the waste biomass.

[0033] The waste lead paste and biomass are dried in an oven at a temperature of 100 to 120° C. for 20 to 30 hours, so as to remove moisture from the waste lead paste and biomass and facilitate crushing of the waste lead paste and biomass in the next step.

[0034] The dried waste lead paste and biomass are crushed into powder in a crusher, respectively, and then the crushed waste lead paste and biomass are sieved to obtain waste lead paste powder and biomass powder below 200 meshes, respectively.

[0035] Step 2) ball-milling the waste lead paste powder and the biomass powder to obtain a mixed powder.

[0036] Specifically, the waste lead paste powder and biomass powder sieved to a size below 200 mesh are added to a ball mill, and the waste lead paste powder and biomass powder are further refined and evenly mixed by ball milling to obtain a mixed powder of the waste lead paste powder and the biomass powder.

[0037] In order to allow the biomass powder and the waste lead paste powder to fully and completely react with each other in the subsequent roasting reduction, the mass ratio of the biomass powder and the waste lead paste powder during ball milling is controlled to be X:1, wherein 0<X≤5.

[0038] Step 3) roasting the mixed powder to obtain liquid metal lead and residual solid matter.

[0039] Among them, short kiln, crucible furnace or muffle furnace and other roasting equipment are used for roasting the mixed powder.

[0040] Specifically, the mixed powder is first placed in a high-temperature resistant crucible with a liquid outlet at the bottom and a sealing cover at the top, and then the high-temperature resistant crucible is placed in a roasting equipment such as a short kiln, a crucible furnace or a muffle furnace, and a container for collecting liquid metal lead produced by roasting is set at the liquid outlet at the bottom of the high-temperature resistant crucible.

[0041] The mixed powder calcination temperature is controlled to be 500°C-1000°C, and the calcination time is controlled to be 0.1h-6h.

[0042] During the roasting process, the biomass powder is pyrolyzed to produce reducing gases such as H2, CO, and CH4, which roast and reduce the difficult-to-treat lead compounds such as lead sulfate and lead dioxide in the waste lead paste powder into lead sulfide and metallic lead. Among them, the metallic lead becomes liquid metal lead at a temperature of 500℃-1000℃ and flows from the liquid outlet at the bottom of the high-temperature crucible into a container for collecting liquid metal lead, while the lead sulfide and other residual solids remain in the high-temperature crucible in the form of residual solids.

[0043] After the roasting is completed, the roasting equipment is cooled to room temperature, and then the high temperature resistant crucible is taken out and the remaining solid matter therein is poured out for standby use.

[0044] Step 4) The remaining solid is ball-milled for a second time to obtain ball-milled powder which is sent to a lead plant as a raw material for lead production.

[0045] See also Figure 3 From the X-ray diffraction (XRD) diagram of the remaining solids, it can be seen that the remaining solids mainly contain lead sulfide and a small amount of lead sulfate. Since the remaining solids contain abundant lead sulfide and a small amount of lead sulfate and other recyclable substances, in order to maximize the recycling of resources, the remaining solids are ball-milled for a second time in a ball mill, and the ball-milled powder obtained is sent to the lead plant to be directly reused as raw material for producing metallic lead.

[0046] The present invention uses waste biomass, which is widely available and cheap, to perform reduction treatment on waste lead paste, which can not only recover relatively precious metallic lead from the waste lead paste, but also return the remaining solid matter containing lead sulfide obtained by roasting to the lead factory for repeated reuse. Not only can precious metallic lead be recovered from the waste lead paste, but also the waste lead paste can be reused in the most resourceful way. Not only can waste biomass and waste lead paste and other waste resources be fully reused, thus saving resources and improving economic benefits, but the process also has lower requirements on temperature conditions, lower energy consumption, and can also reduce SO2 and NO x The emission of pollutants such as carbon dioxide is small, and the pollution is environmentally friendly. It has good market application prospects and is worthy of promotion and application.

[0047] The following is a specific description of a method for treating waste lead paste by roasting biomass provided by the present invention through examples.

[0048] Example 1

[0049] A method for recovering lead from waste lead paste by reducing and roasting biomass, comprising the following steps:

[0050] (1) Dismantle the waste lead-acid batteries to obtain waste lead paste, and dry, grind and screen the waste lead paste and biomass to 200 meshes to obtain waste lead paste powder and biomass powder.

[0051] (2) The waste lead paste powder obtained in step (1) and the biomass powder are ball-milled and mixed in a ratio of 1:0.05 to obtain a mixed powder.

[0052] (3) The mixed powder obtained in step (2) is subjected to reduction roasting in a muffle furnace at 800° C. for 60 minutes, and liquid metal lead is collected from the bottom of a high temperature resistant crucible during the roasting process.

[0053] (4) The solids remaining in the high temperature crucible after reduction roasting in step (3) are subjected to secondary ball milling to obtain ball milled powder. The obtained ball milled powder is sent to a lead plant and directly reused as a raw material for producing metallic lead.

[0054] The composition and content of the residual solid obtained in the high temperature resistant crucible after the waste lead paste powder and the biomass powder in the embodiment of the present invention are as follows: Figure 4 shown.

[0055] The remaining solid material obtained in the high temperature resistant crucible after the roasting reduction reaction in the embodiment of the present invention has an appearance as follows: Figure 6 As shown. Figure 6 It can be seen that the remaining solids obtained in the high temperature resistant crucible after the roasting reduction reaction in the embodiment of the present invention are relatively uniform black material particles.

[0056] Example 2

[0057] The difference between the embodiment of the present invention and embodiment 1 is that in step (2), the mass ratio of waste lead paste powder to biomass powder is 1:0.1, and the other steps and parameters are the same as those in embodiment 1 of the present invention.

[0058] The composition and content of the residual solid obtained in the high temperature resistant crucible after the waste lead paste powder and the biomass powder in the embodiment of the present invention are as follows: Figure 4 shown.

[0059] Example 3

[0060] The difference between the embodiment of the present invention and embodiment 1 is that in step (2), the mass ratio of waste lead paste powder to biomass powder is 1:0.15, and the other steps and parameters are the same as those in embodiment 1 of the present invention.

[0061] The composition and content of the residual solid obtained in the high temperature resistant crucible after the waste lead paste powder and the biomass powder in the embodiment of the present invention are as follows: Figure 4 shown.

[0062] Example 4

[0063] The difference between the embodiment of the present invention and embodiment 1 is that in step (2), the mass ratio of waste lead paste powder to biomass powder is 1:0.2, and the other steps and parameters are the same as those in embodiment 1 of the present invention.

[0064] The composition and content of the residual solid obtained in the high temperature resistant crucible after the waste lead paste powder and the biomass powder in the embodiment of the present invention are as follows: Figure 4 shown.

[0065] Example 5

[0066] The difference between the embodiment of the present invention and embodiment 1 is that in step (2), the mass ratio of waste lead paste powder to biomass powder is 1:0.25, and the other steps and parameters are the same as those in embodiment 1 of the present invention.

[0067] The composition and content of the residual solid obtained in the high temperature resistant crucible after the waste lead paste powder and the biomass powder in the embodiment of the present invention are as follows: Figure 4 shown.

[0068] from Figure 4 It can be seen that in Examples 1-5 of the present invention, as the amount of biomass added gradually increases, the content of metallic lead and lead sulfide in the remaining solid obtained in the high-temperature crucible gradually increases, while the content of lead sulfate, lead oxide and lead dioxide gradually decreases. This shows that as the amount of biomass added in the waste lead paste increases, the effect of roasting and reducing the waste lead paste and biomass gradually increases.

[0069] Example 6

[0070] (1) Dismantle the waste lead-acid batteries to obtain waste lead paste, and dry, grind and screen the waste lead paste and biomass to 200 meshes to obtain waste lead paste powder and biomass powder.

[0071] (2) The waste lead paste powder obtained in step (1) and the biomass powder are ball-milled and mixed in a ratio of 1:5 to obtain a mixed powder.

[0072] (3) reducing and roasting the mixed powder obtained in step (2) in a muffle furnace at 500° C. for 360 minutes, and collecting liquid metal lead from the bottom of the tank during the roasting process;

[0073] (4) The solid product remaining in the tank after the reduction roasting in step (3) is subjected to secondary ball milling to obtain ball milled powder. The obtained ball milled powder is sent to a lead plant and directly reused as a raw material for producing metallic lead.

[0074] The composition and content of the residual solids obtained in a high temperature resistant crucible after the waste lead paste powder and biomass powder of the embodiment of the present invention are reduced and roasted at 500°C are as follows: Figure 5 shown.

[0075] Example 7

[0076] The difference between the embodiment of the present invention and embodiment 6 is that the calcination temperature in step (3) is controlled to be 600° C., and the other steps and parameters are the same as those in embodiment 6 of the present invention.

[0077] The composition and content of the residual solids obtained in the high temperature resistant crucible after the waste lead paste powder and biomass powder of the embodiment of the present invention are as follows: Figure 5 shown.

[0078] Example 8

[0079] The difference between the embodiment of the present invention and embodiment 6 is that the roasting temperature in step (3) is controlled to be 700° C., and the other steps and parameters are the same as those of embodiment 6 of the present invention.

[0080] The composition and content of the residual solids obtained in the high temperature resistant crucible after the waste lead paste powder and biomass powder of the embodiment of the present invention are as follows: Figure 5 shown.

[0081] Example 9

[0082] The difference between the embodiment of the present invention and embodiment 6 is that the calcination temperature in step (3) is controlled to be 800° C., and the other steps and parameters are the same as those in embodiment 6 of the present invention.

[0083] The composition and content of the residual solids obtained in the high temperature resistant crucible after the waste lead paste powder and biomass powder of the embodiment of the present invention are as follows: Figure 5 shown.

[0084] Example 10

[0085] The difference between the embodiment of the present invention and embodiment 6 is that the calcination temperature in step (3) is controlled to be 900° C., and the other steps and parameters are the same as those in embodiment 6 of the present invention.

[0086] The composition and content of the residual solids obtained in the high temperature resistant crucible after the waste lead paste powder and biomass powder of the embodiment of the present invention are as follows: Figure 5 shown.

[0087] from Figure 5It can be seen that in Examples 6-10 of the present invention, as the reduction temperature gradually increases, the content of metallic lead and lead sulfide in the remaining solid obtained in the high-temperature crucible gradually increases, while the content of lead sulfate, lead oxide and lead dioxide gradually decreases. This shows that as the reduction temperature increases, the effect of roasting and reducing waste lead paste and biomass gradually increases.

[0088] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for treating waste lead paste by roasting biomass, characterized in that: The steps include: The waste lead paste and biomass are dried, crushed and sieved to obtain waste lead paste powder and biomass powder respectively; The waste lead paste powder and the biomass powder are ball-milled to obtain a mixed powder; The mixed powder is roasted to obtain liquid metal lead and residual solid matter; The remaining solids are ball-milled for a second time to obtain ball-milled powder which is sent to the lead plant as raw material for lead production.

2. The method for treating waste lead paste by roasting biomass according to claim 1, characterized in that: The waste lead paste includes waste lead paste obtained by disassembling waste lead-acid batteries, and the biomass includes wheat straw, rice straw, corn straw, reed, bamboo, eucalyptus sawdust, poplar sawdust, willow sawdust and pine sawdust.

3. The method for treating waste lead paste by roasting biomass according to claim 2, characterized in that: The waste lead paste and biomass are dried in an oven at a drying temperature of 100 to 120° C. for 20 to 30 hours.

4. The method for treating waste lead paste by roasting biomass according to claim 3, characterized in that: The waste lead paste and biomass are dried, crushed and sieved to obtain waste lead paste powder and biomass powder below 200 meshes respectively.

5. The method for treating waste lead paste by roasting biomass according to claim 1, characterized in that: The mass ratio of the biomass powder and the waste lead paste powder when ball-milled is X:1, wherein 0<X≤5.

6. The method for treating waste lead paste by roasting biomass according to claim 1, characterized in that: When the mixed powder is roasted, the mixed powder is first placed in a high temperature resistant crucible with a liquid outlet at the bottom and a sealing cover at the top, and then the high temperature resistant crucible is placed in a short kiln, a crucible furnace or a muffle furnace for roasting.

7. The method for treating waste lead paste by roasting biomass according to claim 6, characterized in that: The mixed powder is calcined at a temperature of 500° C. to 1000° C. and for a time of 0.1 h to 6 h.

8. The method for treating waste lead paste by roasting biomass according to claim 7, characterized in that: A container for collecting liquid metal lead is arranged at the liquid outlet at the bottom of the high temperature resistant crucible.

9. The method for treating waste lead paste by roasting biomass according to claim 2, characterized in that: The waste lead paste comprises lead sulfate, lead dioxide, lead oxide and metallic lead.

10. The method for treating waste lead paste by roasting biomass according to claim 3, characterized in that: The biomass needs to be washed before drying.

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