Rock ore precious metal test pretreatment method and microwave soot blowing device

Abstract

The invention belongs to the technical field of rock and ore analysis and testing in geological investigation, and discloses a pretreatment method for rock and ore precious metal testing and a microwave soot blowing device.The treatment method comprises the steps that a lead buckle sample containing precious metal is placed in a ceramic cupel of the microwave soot blowing device; the lead buckle is subjected to directional heating treatment through a double-frequency microwave source, the frequency of the double-frequency microwave source comprises 2450 MHz and 915 MHz, and the lead buckle is subjected to oxidation soot blowing at the preset temperature by adjusting the power and frequency combination of the double-frequency microwave source. The microwave soot blowing device comprises a microwave heating unit, a waste gas treatment system and an intelligent temperature control unit. Compared with a traditional resistance heating soot blowing method, the thermal efficiency reaches 90% or above, the soot blowing time is shortened to be smaller than or equal to 25 min, the recovery rate and purity of the precious metal are improved, efficient and accurate rock mine precious metal test pretreatment is achieved, precious metal loss caused by uneven temperature is reduced, energy consumption is reduced, and remarkable technical advantages and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rock and ore analysis and testing in geological exploration, and particularly relates to a rock and ore noble metal pre-treatment method and a microwave cupellation device, aiming to solve the technical problems of low efficiency and heavy pollution in the cupellation link of the traditional fire assaying method, and being suitable for the pre-treatment process of noble metal ores such as gold, silver, platinum and palladium. The rock and ore samples containing lead button samples are efficiently cupelled and waste gas is treated, so as to improve the recovery rate of noble metals and realize environmental protection emission. BACKGROUND

[0002] As a traditional noble metal analysis method, the fire assaying method is widely used in the field of geological exploration, but the cupellation link has obvious efficiency and environmental protection bottlenecks.

[0003] The traditional fire assaying method usually adopts resistance heating, and the thermal efficiency is only about 50%. During the heating process, heat needs to be conducted to the lead button sample through the furnace body, resulting in a cupellation time of 40-60 min, and the temperature difference in the furnace is more than 20℃, which causes insufficient oxidation of the lead button sample (the recovery rate of noble metals is only 98.5%) or over-melting (the loss rate is greater than 1%), seriously affecting the recovery efficiency and quality of noble metals.

[0004] In terms of waste gas treatment, the field laboratory of geological exploration often does not have the conditions to install a centralized waste gas treatment system. In the waste gas generated during the melting process, the lead vapor concentration exceeds 50mg / m³, and the SO2 concentration exceeds 400mg / m³, which is far beyond the limit value of GB16297-1996 emission standard of lead≤0.7mg / m³ and SO2≤550mg / m³, posing a serious threat to the health of the operating personnel and the surrounding environment.

[0005] Although the traditional microwave heating has the characteristics of selective heating and can directly act on the lead button sample, the thermal efficiency is more than 90%, but it has not been applied in the field of fire assaying cupellation. And the waste gas treatment of the existing cupellation device is only simple filtration. Therefore, a fire assaying cupellation device combining microwave directional heating and efficient waste gas treatment is developed. SUMMARY

[0006] In view of this, one of the purposes of the present application is to provide a rock and ore noble metal pre-treatment method, which significantly improves the recovery rate and purity of noble metals, greatly shortens the cupellation time, and realizes efficient and environmentally friendly rock and ore noble metal pre-treatment.

[0007] Another purpose of the present application is to provide a microwave cupellation device, which integrates a dual-frequency microwave directional heating system and a waste gas treatment system in one microwave cupellation device, ensures stable and efficient heating and up-to-standard emission, and meets the efficient, accurate and environmentally friendly requirements of the pre-treatment of noble metals in the field of geological exploration.

[0008] To solve the above technical problems, the technical scheme provided by the present application is to provide a rock and mineral noble metal pretreatment method, comprising the following steps: Put the lead button sample containing noble metal into the ceramic boat of the microwave cupellation device; The lead button sample is subjected to directional heating treatment by using a double-frequency microwave source, the frequency of the double-frequency microwave source includes 2450MHz and 915MHz, and by adjusting the power and frequency combination of the double-frequency microwave source, the lead button sample is oxidized and cupellated at a preset temperature, and the cupellation time is ≤25min.

[0009] Compared with the prior art, the present application has the following advantages: Compared with the traditional resistance heating cupellation method, the present application uses a double-frequency microwave source (2450MHz and 915MHz) to heat the lead button sample containing noble metal, which significantly improves the heating efficiency, the thermal efficiency is as high as 90% or more, the cupellation time is greatly shortened to ≤25min, and the production efficiency is effectively improved; at the same time, by adjusting the power and frequency combination of the double-frequency microwave source, the heating process can be more accurately controlled, so that the lead button sample is uniformly oxidized and cupellated at a preset temperature, thereby improving the recovery rate and purity of noble metal, realizing efficient and accurate rock and mineral noble metal pretreatment, reducing the loss of noble metal caused by uneven temperature, reducing energy consumption, and having significant technical advantages and environmental benefits.

[0010] On the basis of the above technical scheme, the present application can also be improved as follows: Further, it further includes a waste gas treatment step, and the waste gas generated in the cupellation process is treated by the following steps in sequence: (a) condensation and dust removal: the high-temperature waste gas is rapidly cooled to below 50℃ by a condenser, so that the gaseous lead oxide is condensed into particles and captured; (b) alkali liquid spraying absorption: using an alkaline solution to neutralize and absorb the acidic gas in the waste gas; (c) activated carbon adsorption: using honeycomb activated carbon to deeply adsorb residual lead vapor and volatile organic compounds.

[0011] Compared with the prior art, the beneficial effects of using the above further technical scheme are: By adding the waste gas treatment step, the waste gas generated in the cupellation process is sequentially subjected to condensation and dust removal, alkali liquid spraying absorption and activated carbon adsorption, which significantly improves the environmental performance. Compared with the prior art, condensation and dust removal can effectively remove gaseous lead oxide, alkali liquid spraying absorption can neutralize the acidic gas in the waste gas, and activated carbon adsorption can deeply purify the residual harmful substances, so that the waste gas emission concentration is far below the national standard, effectively protecting the health of the operating personnel and the environmental safety, and realizing the win-win of efficient recovery of noble metal and environmentally friendly production.

[0012] Based on the technical scheme, the application can be further improved as follows: Further, between step (a) and step (b), further comprising: Electrostatic adsorption step: using an electrostatic field to adsorb and remove the micron-sized particles remaining in the condensed waste gas.

[0013] Compared with the prior art, the beneficial effects of the above further technical scheme are: The micron-sized particles remaining in the condensed waste gas are adsorbed and removed by using an electrostatic field, further improving the waste gas treatment efficiency, making the waste gas emission more stable and up to standard, and effectively reducing the pollution to the environment.

[0014] Based on the technical scheme, the application can be further improved as follows: Further, when processing any of the following ore lead samples, the specific parameter settings are as follows: (a) Gold ore lead sample: set the microwave power to 1500W, the target temperature to 950℃, the main heating mode to high frequency 2450MHz, the processing time to 20min, and the lead sample to be oxidized to mass <0.1g; (b) Silver ore lead sample: set the microwave power to 1200W, the target temperature to 900℃, the main heating mode to low frequency 915MHz, the processing time to 18min, and the lead sample to be oxidized to mass <0.15g; (c) Platinum ore lead sample: set the microwave power to 1800W, the target temperature to 980℃, and use a dual-frequency mixed mode, wherein 2450MHz accounts for 60% and 915MHz accounts for 40%, the processing time is 25min, and the lead sample is oxidized to completely separate platinum; (d) Palladium ore lead sample: set the microwave power to 1000W, the target temperature to 920℃, and use a low-frequency 915MHz heating mode with an 80% proportion, adjust the power in stages, the power is 1000W for the first 10min and gradually reduces to 800W for the last 12min, the processing time is 22min, and the lead sample is oxidized to completely precipitate palladium.

[0015] Compared with the prior art, the beneficial effects of the above further technical scheme are: The application provides specific parameter settings for different ore lead samples, making the cupellation treatment of gold, silver, platinum, palladium and other precious metals more precise and efficient, respectively increasing their recovery rates to 99.6%, 99.3%, 99.5% and 99.4%, while effectively shortening the processing time and reducing energy consumption, ensuring that the waste gas meets the emission standards, and improving the overall process efficiency and environmental protection.

[0016] Based on the technical scheme, the application can be further improved as follows: Further, when processing the lead button sample of polymetallic intergrowth ore, the following steps are specifically included: The lead button sample containing Au, Ag, Pt and Pd is uniformly spread in a boat, the microwave power is set to 1400W, the target temperature is 950℃, the frequency mode is switched in stages, the high frequency 2450MHz is used for heating in the first 10 minutes, and the low frequency 915MHz is switched for constant temperature in the last 15 minutes, and the processing time is 25 minutes, and the lead button sample is oxidized to completely separate out each noble metal.

[0017] Compared with the prior art, the beneficial effects of the above further technical solutions are: The present application aims at the processing steps of the lead button sample of polymetallic intergrowth ore, which can effectively balance the melting point and oxidation rate of different noble metals, improve the comprehensive recovery rate to 99.3% (the recovery rate of each metal is ≥99%), and at the same time, make the waste gas emission fully meet the standards, and the single batch processing capacity is increased by 150% compared with the traditional one, thereby greatly improving the processing efficiency and resource utilization.

[0018] The present application also provides a microwave cupellation device for realizing the rock ore noble metal test pretreatment method, which comprises: a. A microwave heating unit comprising a double-frequency microwave source and a cordierite ceramic boat tray; the magnetron of the double-frequency microwave source adopts a three-dimensional orthogonal layout to form a uniform electromagnetic field with an electric field intensity deviation of ≤±5%; the bottom of the ceramic boat tray is provided with a microwave transparent hole, and the temperature resistance is ≥1300℃, and the thermal expansion coefficient is ≤1.5×10⁻ 6 / ℃; b. A waste gas treatment system connected in sequence, a condensation unit, a wet scrubbing unit and an activated carbon adsorption unit, c. An intelligent temperature control unit comprising a K-type thermocouple and a PLC controller, which adjusts the microwave power in real time to maintain temperature stability.

[0019] Compared with the prior art, the beneficial effects of the present application are: The microwave cupellation device provided by the present application integrates microwave heating, waste gas treatment and intelligent temperature control unit. The double-frequency microwave source of the microwave heating unit combines the three-dimensional orthogonal magnetron layout and the cordierite ceramic boat tray to realize uniform and efficient heating, improve the recovery rate of noble metals and reduce energy consumption. The waste gas treatment system ensures that the emission meets the standards through condensation, spraying and activated carbon adsorption, protects the environment and the health of the operators. The intelligent temperature control unit adjusts the power in real time to ensure temperature stability. Compared with the traditional device, the present application greatly shortens the cupellation time, improves the processing efficiency, and is suitable for various types of ores, has strong universality, and meets the needs of high efficiency, precision and environmental protection for noble metal test pretreatment in geological exploration field.

[0020] On the basis of the above technical solutions, the present application can also be improved as follows: Further, the waste gas treatment system further comprises an electrostatic adsorption unit, which is arranged between the condensation unit and the wet scrubbing unit.

[0021] Compared with the prior art, the beneficial effects of the above further technical solutions are: The electrostatic adsorption unit is added in the waste gas treatment system, which further improves the waste gas treatment efficiency, can more effectively remove micrometer-sized particulate matters, and ensures stable and standard emission of waste gas.

[0022] On the basis of the above technical solutions, the present application can also be improved as follows: Further, the condensation unit is a spiral pipe condenser, and the cooling medium is circulating water with a temperature of ≤25 DEG C.

[0023] Compared with the prior art, the beneficial effects of the above further technical solutions are: The spiral pipe condenser is used as the condensation unit, and the circulating water is used as the cooling medium with a temperature controlled at ≤25 DEG C, which can effectively improve the condensation efficiency, make the gaseous lead oxides in the high-temperature waste gas more fully condensed into particles and captured, improve the waste gas treatment effect, and further optimize the waste gas treatment system, so that the system runs more stably and reliably, and the energy consumption and operation cost are effectively reduced.

[0024] On the basis of the above technical solutions, the present application can also be improved as follows: Further, the wet scrubbing unit is an alkali liquid spraying tower, and the spraying liquid is 20% NaOH solution with a pH value of 12±0.5.

[0025] Compared with the prior art, the beneficial effects of the above further technical solutions are: The 20% NaOH solution is used as the spraying liquid, and the pH value is accurately controlled at 12±0.5, which can efficiently neutralize the acidic gas in the waste gas, so that the purification efficiency of SO2 and other pollutants is ≥98%, the waste gas treatment effect is effectively improved, and the emission is ensured to meet the standard.

[0026] On the basis of the above technical solutions, the present application can also be improved as follows: Further, the activated carbon adsorption unit is filled with honeycomb-shaped activated carbon, and the iodine value of the activated carbon is ≥1200 mg / g, and the specific surface area is >1500 m² / g.

[0027] Compared with the prior art, the beneficial effects of the above further technical solutions are: The application selects honeycomb active carbon to fill the adsorption unit, the iodine value of which is greater than or equal to 1200 mg / g, the specific surface area is greater than 1500 m² / g, the adsorption capacity is strong, the residual lead vapor and volatile organic compounds can be deeply adsorbed, the lead vapor concentration in the waste gas is ensured to be less than or equal to 0.1 mg / m³, which is superior to the national standard, and the environmental protection performance is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiments will be briefly introduced below, and it should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of the drawings.

[0029] Figure 1 is a front view structural schematic diagram of a preferred embodiment of the microwave cupellation device.

[0030] Figure 2 is a top view structural schematic diagram of Figure 1 .

[0031] Figure 3 is a front perspective structural schematic diagram of Figure 1 .

[0032] Figure 4 is a rear perspective structural schematic diagram of Figure 1 .

[0033] The marks in the figure are respectively: 100 microwave heating unit, 101 ceramic cupel tray, 102 cupel, 200 condensing unit, 210 condensing box, 211 first condensing chamber, 212 partition plate, 213 second condensing chamber, 214 drain pipe, 220 condensing pipe, 221 first condensing section, 222 second condensing section, 300 electrostatic adsorption unit, 400 wet scrubbing unit, 410 spray liquid pipe, 500 active carbon adsorption unit, 501 chimney, 610 first pipeline, 620 second pipeline, 630 third pipeline, 640 fourth conduit. DETAILED DESCRIPTION

[0034] The following will be described in conjunction with specific embodiments.

[0035] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application. Therefore, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0036] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are all conventional methods in the art, unless otherwise specified.

[0037] In this embodiment, microwave directional heating is adopted, and the core heating module is a double-frequency microwave source: integrated 2450MHz (high frequency, rapid heating) and 915MHz (low frequency, penetration heating) magnetrons, with total power of 0-2000W adjustable. The microwave energy is focused on the area of the ash pan through a waveguide coupler (energy utilization rate is increased by 40%). The magnetrons are arranged in three dimensions and orthogonally, with 2 arranged horizontally along the top of the furnace chamber and 2 arranged vertically along the side, forming a uniform electromagnetic field (electric field intensity deviation ≤±5%).

[0038] In this embodiment, the ash pan tray is selected as a ceramic ash pan tray, which is made of cordierite ceramic material (low dielectric loss, temperature resistance of 1300℃), and the bottom of the tray is provided with microwave transparent holes to realize non-contact directional heating of the lead buckle sample. The temperature difference between the surface and the center of the lead buckle sample is ≤3℃ (the temperature difference of traditional equipment is >20℃).

[0039] According to the characteristics of ceramic materials and the principle of microwave heating, the combination of microwave heating and ceramic ash pan tray has significant advantages in reducing ash pan wear and prolonging equipment life.

[0040] (1) The ceramic ash pan tray is used in the method, which solves the core defects of the graphite tray.

[0041] Oxidation resistance: graphite trays are easily oxidized to generate CO / CO2 under high temperature (especially in an oxygen environment), which causes the tray to become thin, loose in structure, and even peel off and contaminate the ash pan. The ceramic ash pan tray has strong chemical stability and is resistant to oxidation above 1000℃, which fundamentally avoids the indirect pollution and mechanical damage of the ash pan caused by the wear of the tray material.

[0042] Non-conductivity and thermal stability: Graphite is a good conductor, and microwave heating may cause arc discharge due to local eddy current effect (especially when there are impurities on the surface), and the instantaneous high temperature can burn the ash pan; while ceramics are insulators, which only heat uniformly through dielectric loss, and the temperature distribution is more controllable (temperature difference ≤ ± 5℃ vs graphite tray ± 15℃ or more), reducing the cracks caused by thermal stress impact on the ash pan.

[0043] Low thermal expansion coefficient: The thermal expansion coefficient of most ceramics (such as cordierite ceramics) is much lower than that of graphite (~ 1.5 × 10⁻ 6 / ℃), which is ~ 5 × 10⁻ 6 / ℃, and the deformation is smaller when repeatedly heated and cooled, and the interface with the ash pan is more stable, reducing friction loss and mechanical stress damage.

[0044] (2) Protection of equipment The dust generated by the oxidation of graphite tray is easy to adhere to the inner wall of the microwave cavity or the magnetron, which reduces the efficiency of microwave reflection and even causes equipment failure. The ceramic ash pan tray has no dust falling off, and the surface is smooth and easy to clean, which can reduce the frequency of equipment maintenance.

[0045] The high-temperature life of ceramic ash pan tray ≥500 times of heating cycle, far exceeding that of graphite tray (≤100 times), reducing the damage to the mechanical structure of the equipment (such as guide rail wear and positioning deviation) caused by frequent replacement of the tray.

[0046] To further illustrate that the combination of microwave heating and ceramic ash pan tray can significantly reduce the ash pan wear and tear through the advantages of material properties (oxidation resistance, thermal stability, low loss), and prolong the service life of the equipment, the following part of the experiment is disclosed.

[0047] The design of the comparative experiment (standardized test conditions) is as follows: Control group: traditional graphite tray + 20 standard ash pans (uniform material / size); Experimental group: ceramic ash pan tray (same size, material such as cordierite ceramics) + 20 ash pans of the same batch.

[0048] The operation procedures of the two groups are as follows: microwave power 1500W (high frequency 2450MHz mainly); Heating program: heating rate 10℃ / min to 1000℃, constant temperature 30min.

[0049] The situation after every 50 times of heating is recorded as shown in Tables 1 and 2: Table 1 Comparison of ash pan wear rate Note: 1. Ash pan breakage rate: the proportion of ash pans with cracks / nicks, with a conclusion that the graphite group had a breakage rate of 30%, and the ceramic group had a breakage rate of 8%; 2. Mass loss: the mass of ash pans peeled off due to high temperature was measured by a precision balance, with a conclusion that the graphite group had an average loss of 0.12 mg each time, and the ceramic group had an average loss of 0.03 mg each time; Table 2. Tray life and equipment maintenance frequency table Note: The failure standard of the tray is that the graphite group tray has a through crack, and the thickness reduction is greater than or equal to 20%.

[0050] In this embodiment, a temperature control unit is used for intelligent temperature control.

[0051] The temperature is monitored in real time by embedding a K-type thermocouple (precision ±1°C) at the edge of the ash pan, and fed back to the PLC controller. The microwave power is dynamically adjusted (adjustment accuracy ±10W) to maintain the temperature difference between the surface and the center of the ash pan to be less than or equal to 3°C, and to ensure stable ash blowing temperature.

[0052] In this embodiment, the waste gas generated by ash blowing is treated by the following process: 1. Condensation and dust removal The waste gas outlet is connected to a spiral tube condenser (the cooling medium is circulating water, and the temperature is less than or equal to 25°C), which cools the high-temperature waste gas (greater than 900°C) to below 50°C, so that the gaseous PbO is condensed into particles (particle size greater than 1μm), and the capture efficiency is greater than or equal to 95%.

[0053] 2. Electrostatic adsorption (optional): After condensation, the waste gas enters the electrostatic adsorption unit, and a high-voltage electrostatic field of 15kV is applied to remove residual micron-sized particles (capture efficiency greater than or equal to 98%).

[0054] 3. Alkaline solution spray absorption A packed tower structure is used to spray 20% NaOH solution (pH=12±0.5), to absorb SO2, HCl and other acidic gases through gas-liquid countercurrent contact, and the purification efficiency is greater than or equal to 98%, and the outlet SO2 concentration is less than or equal to 50mg / m³.

[0055] 4. Activated carbon adsorption Honeycomb-shaped activated carbon (iodine value greater than or equal to 1200mg / g, specific surface area greater than 1500m² / g) is filled to deeply adsorb residual lead vapor and volatile organic compounds, and the final lead vapor concentration is less than or equal to 0.1mg / m³, which is 7 times better than the national standard.

[0056] Waste gas treatment is linked with microwave heating, and condensation and spraying are started simultaneously when the microwave is started, and after the microwave is stopped, condensation and spraying continue to run for 10~20min to ensure that the residual waste gas is completely treated.

[0057] Example 1 This example describes a method for pre-treatment of rock gold testing to treat a gold ore sample containing lead, thereby achieving efficient recovery of precious metals and compliance with waste gas emission standards. The detailed steps are as follows: 1. Place the gold-containing lead button sample (gold addition 5%) into a cordierite ceramic ash dish and place it in the center of the tray.

[0058] 2. Parameter settings: Microwave power: 1500W (mainly high frequency 2450MHz, rapid heating); Target temperature: 950°C; Processing time: 20 min (PLC dynamically adjusts power based on thermocouple feedback to ensure complete oxidation of the lead button sample to a mass of <0.1 g).

[0059] Parameter selection based on: In order to optimize the microwave ash blowing parameters of gold mine, L9(3 4 ) Orthogonal table was used to conduct a three-level test on the four factors of microwave power (A), temperature (B), heating time (C), and microwave frequency combination (D), with gold recovery rate and waste gas purification efficiency as evaluation indicators.

[0060] Table 3 Orthogonal test of gold concentrate (factor level table) Table 4 Experimental results: Range analysis: The primary and secondary factors affecting recovery rate are: temperature (B) > power (A) > frequency combination (D) > time (C). The optimal combination: A2B2C2D2 (1500W, 950°C, 20 minutes, dual-frequency mixing), with a gold recovery rate of 99.6% and a lead vapor concentration of 0.08 mg / m³.

[0061] 3. Waste gas treatment: Simultaneously start the condensation pump (flow rate 5L / min) and NaOH spray pump (flow rate 10L / min); After the exhaust gas undergoes three-stage treatment of condensation, spraying and carbon adsorption, the lead vapor concentration in the exhaust gas is 0.08 mg / m³ and the SO2 concentration is 42 mg / m³, meeting the emission standards.

[0062] The traditional gold ore processing method uses resistance heating, which causes the outer layer of the lead buckle sample to over-melt, with a loss rate of 1.2%. In addition, the inner layer of the lead buckle sample is not fully oxidized, resulting in a recovery rate of only 98.5%.

[0063] The embodiment directly heats the lead button sample with a microwave, completes oxidation within 20 minutes, increases the recovery rate to 99.6%, reduces energy consumption by 59%, automatically controls the temperature throughout the process, and increases the single batch processing capacity by 100% compared to the prior art.

[0064] Example 2 This embodiment describes a rock silver test pretreatment method for processing silver ore samples containing lead buttons, which avoids silver over-melting loss and efficiently purifies waste gas: 1. Put the silver-containing lead button sample (silver addition amount 5%) into a cordierite ceramic boat, and lightly press it onto the upper part of the tray transparencies.

[0065] 2. Parameter settings: Microwave power: 1200W (low frequency 915MHz mainly, uniform heating); Target temperature: 900℃ (50℃ lower than gold concentrate, close to silver melting point but avoid over-melting); Treatment time: 18 min (real-time monitoring of lead button sample oxidation speed to ensure residual mass <0.15g).

[0066] Parameter selection basis: To optimize the microwave cupellation parameters of silver ore, L9(3 4 ) orthogonal table is used to conduct three-level test on four factors: microwave power (A), temperature (B), heating time (C), and microwave frequency combination (D), with silver recovery rate and waste gas purification efficiency as evaluation indexes.

[0067] Table 5: Silver ore orthogonal test (factor level table) Table 6: Experimental results: Range analysis: Primary and secondary factors affecting recovery rate: temperature (B) > power (A) > time (C) > frequency combination (D); Optimal combination: A2B2C2D2 (1200W, 900℃, 18min, low frequency mainly), the corresponding recovery rate is 99.5%, and SO2 concentration is 38mg / m³.

[0068] 3. Waste gas treatment: Start the condensation pump (flow rate 4L / min) and NaOH spraying pump (flow rate 10L / min) simultaneously; After three-stage treatment of condensation, spraying and carbon adsorption, the lead vapor concentration in the exhaust gas is 0.05mg / m³, and the SO2 concentration is 38mg / m³, which is better than the national standard.

[0069] Traditional silver ore processing method, using resistance heating, uneven temperature leads to silver and lead alloying (loss rate 1.5%), and lead vapor concentration in waste gas reaches 58mg / m³ (exceeds 83 times).

[0070] This embodiment uses microwave to directly heat lead button samples, low-frequency microwave uniform heating (temperature difference ≤3℃), recovery rate is improved to 99.3%, lead vapor purification to 0.05mg / m³, in line with the most stringent emission standards.

[0071] Example 3 This embodiment describes the rock platinum test pretreatment method, which processes platinum group metal (Pt, Pd, etc.) ore samples containing lead button samples, adapts to the high melting point characteristics of platinum group metals, ensures complete cupellation and recovery, and the detailed steps are as follows: 1. Put the platinum-containing lead button sample (platinum addition amount 5%) into a cordierite ceramic boat, ensure the thickness of the lead button sample is uniform (≤1.5cm), and place it in the center of the tray.

[0072] 2. Parameter settings: Microwave power: 1800W (dual-frequency mixed mode, 2450MHz high-frequency ratio 60% fast heating, 915MHz low-frequency ratio 40% deep penetration); Target temperature: 980℃ (55% higher than the melting point of platinum 1768℃, to ensure that lead is fully oxidized and separated); Treatment time: 25 min (extended by 5 min to ensure complete separation of high-melting-point platinum group metals and lead).

[0073] Parameter selection basis: To optimize the microwave cupellation parameters of platinum ore, L9(3 4 ) orthogonal table is used to conduct three-level test on four factors of microwave power (A), temperature (B), heating time (C) and microwave frequency combination (D), with platinum recovery rate and waste gas purification efficiency as evaluation indexes.

[0074] Table 7 Orthogonal test of platinum ore (factor level table) Table 8 Experimental results: Range analysis: Primary and secondary factors affecting recovery rate: temperature (B) > power (A) > time (C) > frequency combination (D); Optimal combination: A2B2C2D2 (1800W, 980℃, 25min, high frequency as main), the corresponding recovery rate is 99.6%, lead vapor capture efficiency is 99.9%.

[0075] 3. Waste gas treatment: Condensing pump (flow 6L / min), NaOH spray pump (flow 10L / min) are started simultaneously. After three-stage treatment of condensation, spraying and carbon adsorption, the lead vapor concentration in the exhaust gas is 0.07mg / m³, and the SO2 concentration is 45mg / m³, which meets the emission standard.

[0076] The traditional resistance heating method cannot effectively process platinum ore. The resistance heating temperature is less than 1000℃, platinum cannot be completely separated, and secondary cupellation is required, which takes more than 90 minutes.

[0077] In this embodiment, the platinum ore lead sample is heated by double-frequency microwave at 980℃ for 25 minutes, and the platinum recovery rate is 99.5%. It is the first time to realize efficient cupellation of platinum ore, which is 1.2% higher than traditional resistance heating, and the energy consumption of single treatment is 1.2kWh (45% lower than traditional resistance heating method).

[0078] Example 4 This embodiment describes a rock ore palladium pretreatment method for processing lead sample containing palladium (Pd). In view of the characteristics that palladium is easy to form alloy with lead, the heating uniformity is optimized, and the detailed steps are as follows: 1. Put the palladium ore lead sample (palladium addition amount 5%) into a cordierite ceramic boat, and gently knock the boat to make the surface of the lead sample flat.

[0079] 2. Parameter settings: Microwave power: 1000W. Low frequency 915MHz is the main one, accounting for 80%, reducing the direct impact of high frequency on palladium.

[0080] Target temperature: 920℃. Slightly higher than 59% of the palladium melting point 1554℃, to avoid alloy over-melting.

[0081] Treatment time: 22 min. Gradually adjust the power: 1000W for the first 10 min, and gradually reduce to 800W for the last 12 min, to ensure that the lead oxidation proceeds layer by layer.

[0082] 3. Exhaust gas treatment: Condensing pump (flow 6L / min), NaOH spray pump (flow 10L / min) are started simultaneously. There are more sulfides in the palladium ore exhaust gas, so the exhaust gas treatment time needs to be extended to 20 minutes after the microwave heating stops to ensure complete purification.

[0083] The palladium recovery rate is 99.4%.

[0084] Example 5 This embodiment describes a comprehensive noble metal ore pretreatment method for processing multi-metal associated ore lead samples, balancing different metal melting points and oxidation rates. The detailed steps are as follows: 1. Spread the mixed precious metal lead button sample (particle size ≤2 mm) evenly on the cupel, with a thickness of less than 1 cm.

[0085] 2. Parameter settings: Microwave power: 1400W. Dual-frequency dynamic switching: 950℃ for the first 10 min, then switch to 915MHz for the last 15 min.

[0086] Target temperature: 950℃. Balanced temperature, taking into account the high temperature requirements of gold and platinum and the anti-overfusion requirements of silver and palladium.

[0087] Treatment time: 25 min. Stage control: rapid oxidation of lead for 0-10 min, constant temperature for 10-25 min to ensure complete precipitation of precious metals.

[0088] 3. Waste gas treatment: Start the condensation pump (flow rate 5L / min) and NaOH spraying pump (flow rate 10L / min) simultaneously; continue condensation / spraying for 15 min after microwave heating is completed.

[0089] The overall recovery rate of this example is 99.3%, and the recovery rate of each metal is ≥99%. The waste gas emission meets the standards, and the single batch processing capacity reaches 50 samples, which is 150% higher than the traditional method.

[0090] As valuable experience in completing the invention: The recovery rate of precious metals is strongly positively correlated with temperature. For every 50℃ increase in temperature, the recovery rate increases by 0.5%-1.0%, but it needs to match the ore melting point. If the temperature of silver ore exceeds 930℃, the loss rate increases by 0.8%.

[0091] Microwave power affects heating rate. For every 300W increase in power, the cupellation time is shortened by 3-5 min, but excessive power can cause local overfusion. If the power of platinum ore is >2200W, the energy consumption increases by 20% without significant improvement in recovery rate.

[0092] The frequency combination of the embodiment has significant advantages compared to traditional resistance heating. First, the thermal efficiency of traditional resistance heating is only about 50%, the heating speed is slow, and the temperature uniformity is poor, with an internal temperature difference of more than 20℃, which not only leads to insufficient oxidation or over-melting of lead samples, but also makes the recovery rate of precious metals low and the loss rate high. However, the combination of high-frequency microwave (2450MHz) and low-frequency microwave (915MHz) used in the embodiment can fully utilize the advantages of different frequency microwaves. In the initial heating stage of gold concentrate and platinum ore, high-frequency microwave (2450MHz) can achieve rapid heating, effectively shorten the heating time and improve production efficiency; in the constant temperature stage of silver ore and palladium ore, low-frequency microwave (915MHz) can achieve uniform heating, with a temperature difference between the surface and center of the cupel controlled within 3℃, significantly reducing the loss of precious metals due to uneven temperature and improving the recovery rate of precious metals. In addition, the dual-frequency mixed mode can be flexibly adjusted according to different types of ore and processing requirements, taking into account the heating efficiency and temperature uniformity, achieving a balance between efficiency and accuracy. Compared with resistance heating, the thermal efficiency of microwave heating in the invention is more than 90%, which greatly reduces energy consumption and significantly reduces waste gas emissions, making it more environmentally friendly. In summary, the frequency combination of the invention is superior to traditional resistance heating in terms of heating efficiency, temperature uniformity, precious metal recovery rate, energy consumption and environmental friendliness.

[0093] The embodiment reflects the excellent environmental synergy of the invention. When the recovery rate of precious metals is ≥99%, the lead vapor capture efficiency is >99.5%. This indicates that there is a significant positive correlation between efficient cupellation and waste gas purification. Specifically, when the cupellation process is more efficient and the lead sample is more fully oxidized, the amount of lead vapor produced is less, thereby reducing the burden of waste gas treatment. This enables the waste gas treatment system to more effectively capture and purify lead vapor, ensuring that its emission concentration is far below the national standard limit. This synergistic effect not only improves the recovery efficiency of precious metals, but also significantly reduces environmental pollution, achieving a win-win situation of efficient production and environmental protection.

[0094] The orthogonal test data show that the optimal parameter combination can be quickly matched for different ore types to realize multi-objective optimization of "efficiency-precision-environmental protection". Through the orthogonal test, the primary and secondary order of each influencing factor and the optimal level combination of different ore types in the microwave heating process can be determined. For example, in the gold concentrate test, it is determined that temperature is the primary factor affecting recovery rate, followed by power, frequency combination, and finally time, and the optimal combination is 1500W power, 950°C temperature, 20 minutes time and double frequency mixed mode, at which time the gold recovery rate reaches 99.6%, and the lead vapor concentration is only 0.08mg / m³. This shows that by accurately controlling the parameters, the recovery efficiency of precious metals can be improved, the recovery accuracy can be ensured, and the emission of waste gas pollutants can be reduced to realize environmental protection production. This multi-objective optimization enables the microwave cupellation technology to quickly find the best process parameters that balance efficiency, accuracy and environmental protection requirements according to the characteristics of different ores, providing an efficient, accurate and environmentally friendly pretreatment method for rock and ore precious metal testing in geological exploration.

[0095] As can be seen from the multi-dimensional comparison in Table 9, the present application comprehensively surpasses the traditional resistance heating method in efficiency, accuracy, environmental protection and application range, especially solving the cupellation problem of difficult-to-treat precious metals such as platinum and palladium, and meeting the demand for efficient and green analysis in geological exploration.

[0096] Table 9: Comparison data table of traditional method and typical precious metal test of the present application Example 6 Referring to Figures 1-4 The microwave cupellation device described in this embodiment is a specific structure of the equipment for completing the rock and ore precious metal test pretreatment steps in Examples 1-5. It includes a microwave heating unit 100, a condensation unit 200, an electrostatic adsorption unit 300 (optional), a wet washing unit 400, an activated carbon adsorption unit 500, and an intelligent temperature control unit.

[0097] The microwave heating unit 100 (without showing the door structure) adopts a double-frequency microwave source, integrating 2450MHz (high frequency, fast heating) and 915MHz (low frequency, penetration heating) magnetrons, with a total power of 0-2000W adjustable. The microwave energy is focused on the cupel area through a waveguide coupler, and the energy utilization rate is improved by 40%. The magnetrons are arranged in a three-dimensional orthogonal layout, with 2 arranged horizontally along the top of the furnace cavity and 2 arranged vertically along the side, forming a uniform electromagnetic field with an electric field intensity deviation of ≤±5%. The unit is provided with a waste gas outlet for discharging waste gas generated during cupellation.

[0098] The ceramic cupel tray 101 is made of cordierite ceramic material with low dielectric loss and temperature resistance of 1300°C. The tray bottom is provided with microwave transparent holes to realize non-contact directional heating of the lead button sample, with a temperature difference between the surface and the center of the lead button sample of ≤3°C, which is significantly better than the traditional equipment with a temperature difference of >20°C.

[0099] The cupel 102 is a container for placing a lead-containing button sample on the ceramic cupel tray for carrying the rock and mineral sample to be treated.

[0100] The condensing unit 200 uses a spiral tube condenser with a cooling medium of circulating water at a temperature of ≤25°C. The condensing unit 200 is connected to the exhaust gas outlet of the microwave heating unit 100 through the first pipeline 610 to rapidly cool the high-temperature exhaust gas (>900°C) to below 50°C, so that the gaseous PbO is condensed into particles (particle size >1 μm) with a capture efficiency of ≥95%.

[0101] In one embodiment, the condensing unit 200 includes a condensing box 210 and a condensing pipe 220. The condensing box 210 is divided into a first condensing chamber 211 and a second condensing chamber 213 by a partition 212. The condensing pipe 220 is a spiral pipe including a first condensing section 221 located in the first condensing chamber 211 and a second condensing section 222 located in the second condensing chamber 213. A drain pipe 214 is used to drain the condensate water generated during the condensation process. The exhaust gas flows from the first condensing section 221 to the second condensing section 222, and the condensate water flows from the second condensing chamber 213 over the partition 212 to the first condensing chamber 211.

[0102] The intelligent temperature control unit includes a K-type thermocouple and a PLC controller for real-time adjustment of microwave power to maintain temperature stability. The temperature is monitored in real time by embedding a K-type thermocouple (accuracy ±1°C) on the edge of the cupel, which is fed back to the PLC controller. The microwave power is dynamically adjusted (adjustment accuracy ±10W) to maintain a temperature difference between the surface and the center of the cupel of ≤3°C, ensuring stable cupellation temperature.

[0103] Alternatively, the condensed exhaust gas enters the electrostatic adsorption unit 300 through the second pipeline 620, a 15kV high-voltage electrostatic field is applied, and residual micron-sized particles are removed with a capture efficiency of ≥98%.

[0104] The wet scrubbing unit 400 is an alkaline liquid spray tower with a 20% NaOH solution as the spray liquid with a pH value of 12±0.5. The spray liquid is sprayed through the spray liquid pipe 410 to absorb acidic gases such as SO2 and HCl in the exhaust gas, with a purification efficiency of ≥98%. The wet scrubbing unit 400 is connected to the electrostatic adsorption unit 300 through the third pipeline 630. In the case where the device does not use the electrostatic adsorption unit 300, the third pipeline 630 is directly connected to the second pipeline 620.

[0105] The activated carbon adsorption unit 500 is filled with honeycomb activated carbon with iodine value ≥1200mg / g and specific surface area >1500m² / g, which deeply adsorbs residual lead vapor and volatile organic compounds, ensuring that the lead vapor concentration in the exhaust gas finally discharged from the chimney 501 is ≤0.1mg / m³, realizing environmental protection emission.

[0106] In the description of the present application, it should be understood that "-" and "~" represent the range between two values, and the range includes the endpoints. For example: "A-B" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0107] In the description of the present application, the term "and / or" herein is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent three cases: A exists alone, A and B exist together, and B exists alone.

[0108] In the description of the invention, the values related to time, temperature, ratio and mass, etc. can be based on actual measurement, equipment standard parameters, simplified rounding results, or within an acceptable error range, ensuring the practicability and repeatability of the invention.

[0109] In the description of the present application, the term "about" or "approximately" is used to express the approximate value of the numerical value or interval, allowing a certain error to exist, so as to ensure the flexibility and practicability of the description, while keeping within an acceptable error range, the maximum error range does not exceed 10% of the corresponding numerical value or numerical range.

[0110] The above is only the preferred embodiment of the present application, it should be pointed out that the above preferred embodiment should not be regarded as a limitation of the present application, the protection scope of the present application should be limited by the scope defined by the claims. For ordinary skilled in the art, without departing from the spirit and scope of the present application, a number of improvements and refinements can also be made, which should be regarded as the protection scope of the present application.

Claims

1. A method for pre-treatment of precious metals in rock and minerals, characterized in that: The following steps are involved: The lead button sample containing precious metals is placed in a ceramic ash dish of a microwave ash blowing device; The lead buckle sample is subjected to a directional heating treatment using a dual-frequency microwave source, wherein the frequencies of the dual-frequency microwave source include 2450 MHz and 915 MHz. By adjusting the power and frequency combination of the dual-frequency microwave source, the lead buckle sample is oxidized and ash-blown at a preset temperature, and the ash-blowing time is ≤25 minutes.

2. The method according to claim 1, characterized in that The waste gas treatment step is also included. The waste gas generated during the soot blowing process is treated in the following steps: Condensation dust removal: The high-temperature exhaust gas is quenched to below 50°C through a condenser, so that the gaseous lead oxides are condensed into particles and captured; Alkali solution spray absorption: using alkaline solution to neutralize and absorb the acidic gas in the exhaust gas; Activated carbon adsorption: Residual lead vapor and volatile organic compounds are deeply adsorbed by honeycomb activated carbon.

3. The method according to claim 2, characterized in that Between step (a) and step (b), the following steps are also included: Electrostatic adsorption step: Use the electrostatic field to adsorb and remove the micron-sized particles remaining in the condensed exhaust gas.

4. The method according to claim 1, wherein When processing any of the following ore lead buckle samples, the specific parameter settings are as follows: (a) Gold ore lead button sample: microwave power was set to 1500W, target temperature to 950°C, high frequency to 2450MHz as the main heating mode, and treatment time was 20 minutes. The lead button sample was oxidized to a mass of <0.1g. (b) Silver ore lead button sample: microwave power was set to 1200 W, target temperature to 900°C, low frequency 915 MHz was used as the primary heating mode, and the treatment time was 18 minutes. The lead button sample was oxidized to a mass of <0.15 g. (c) Platinum ore lead button sample: The microwave power was set to 1800 W, the target temperature was set to 980°C, and a dual-frequency mixing mode was used, with 2450 MHz accounting for 60% and 915 MHz accounting for 40%. The treatment time was 25 minutes, and the lead button sample was oxidized until the platinum was completely separated. (d) Palladium ore lead button sample: The microwave power was set to 1000 W, the target temperature was set to 920°C, and a heating mode with a low frequency of 915 MHz accounting for 80% was adopted. The power was adjusted in stages: 1000 W for the first 10 minutes and then gradually decreased to 800 W for the next 12 minutes. The treatment time was 22 minutes. The lead button sample was oxidized until the palladium was completely precipitated.

5. The method according to claim 1, wherein When processing polymetallic paragenetic lead buckle samples, the following steps are specifically included: The lead button samples containing Au, Ag, Pt, and Pd were evenly spread in an ash dish, the microwave power was set to 1400 W, the target temperature was set to 950°C, and the frequency mode was switched in stages. The high frequency of 2450 MHz was used for heating in the first 10 minutes, and then the low frequency of 915 MHz was switched to constant temperature in the next 15 minutes. The treatment time was 25 minutes, until the lead button samples were oxidized until all the precious metals were completely precipitated.

6. A microwave ash blowing device, characterized in that: The method for implementing any one of claims 1 to 5 comprises: a. A microwave heating unit comprising a dual-frequency microwave source and a cordierite ceramic ash tray. The dual-frequency microwave source's magnetrons utilize a three-dimensional orthogonal layout to create a uniform electromagnetic field with an electric field intensity deviation of ≤±5%. The ceramic ash tray has microwave perforations at its bottom, a temperature resistance of ≥1300°C, and a thermal expansion coefficient of ≤1.5×10⁻. 6 / ℃; b. Exhaust gas treatment system, which is connected in sequence to the condensation unit, wet scrubber unit and activated carbon adsorption unit, c. Intelligent temperature control unit, including K-type thermocouple and PLC controller, adjusts microwave power in real time to maintain temperature stability.

7. The device according to claim 6, characterized in that The exhaust gas treatment system further includes an electrostatic adsorption unit, which is disposed between the condensing unit and the wet scrubbing unit.

8. The device according to claim 6, characterized in that The condensing unit is a spiral tube condenser, the cooling medium is circulating water, and the temperature is ≤25°C.

9. The device according to claim 6, characterized in that The wet scrubbing unit is an alkali solution spray tower, the spray liquid is a 20% NaOH solution, and the pH value is 12±0.

5.

10. The device according to claim 6, characterized in that The activated carbon adsorption unit is filled with honeycomb activated carbon, the iodine value of the activated carbon is ≥1200 mg / g, and the specific surface area is greater than 1500 m² / g.

Images