A method for comprehensive recycling of acid production electroslag

Abstract

This invention belongs to the field of metallurgical technology and discloses a method for the comprehensive recycling and utilization of electro-fogging slag from acid production. The method includes the following steps: S1. Slurrying: Electro-fogging slag, mercury-containing crude selenium, and concentrated sulfuric acid are mixed and slurried to obtain a slurry material; S2. Primary acid roasting: The slurry material is fed into a roasting furnace for roasting at a temperature of 220-320℃ for 20-60 h, with a negative pressure of 0--50 Pa inside the furnace during the roasting process; primary roasting slag is obtained; selenium dioxide is recovered through sedimentation of the roasting flue gas; S3. Secondary roasting: The primary roasting slag is roasted again at a temperature of 340-440℃ for 3-10 h, with a negative pressure of -50--200 Pa inside the furnace during the roasting process; secondary roasting slag is obtained; mercury-containing crude selenium is recovered from the roasting flue gas. This invention achieves effective separation and efficient recovery of selenium and mercury, and also recovers valuable metals such as selenium, mercury, lead, gold, and silver in stages.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for the comprehensive recycling and utilization of acid production electro-fogging slag. Background Technology

[0002] In the pyrometallurgical processes of copper, lead, zinc, and nickel, and in the pre-treatment process of gold production roasting, there is generally a flue gas acid production system. The sulfur dioxide-containing flue gas from pyrometallurgical processes is fed into the acid production system after passing through a waste heat boiler and electrostatic precipitator. In this system, the flue gas undergoes reverse-jet scrubbing, purification scrubbing, two-stage electrostatic precipitator treatment, drying, conversion, and absorption to produce concentrated sulfuric acid. During the purification scrubbing process, acid sludge is produced in relatively large quantities, with relatively low selenium and mercury grades and high lead content. Meanwhile, a small amount of electrostatic precipitator residue is produced, with low lead content and high selenium and mercury grades. The sulfuric acid electrostatic precipitator residue contains large amounts of selenium, mercury, and lead, with some mercury existing in elemental form. If this material is accumulated on-site for a long time, the mercury will volatilize into the atmosphere, causing air pollution. Furthermore, prolonged storage not only occupies storage space in the material yard but also causes continuous pollution to the surrounding soil, groundwater, and other surface environments.

[0003] The yield of sulfuric acid electroslag is typically small, but it is high in selenium and mercury, giving it significant recycling value. Currently, due to its low yield, most companies mix the electroslag with acid sludge and employ a combined wet and pyrometallurgical process. The main problems with this mixed treatment method are as follows:

[0004] (1) Although this method can produce mercury and crude selenium, the grade of crude selenium can only reach about 90%, and some mercury will enter the crude selenium product. Therefore, although this method can achieve the initial recovery of selenium and mercury, it has the problems of low resource recovery rate, incomplete separation of selenium and mercury, and low product quality.

[0005] (2) This method requires a large amount of acid and alkali chemical raw materials to be consumed during the production process and produces a large amount of wastewater. It is difficult to treat the wastewater to meet the standards. At the same time, the large amount of acid and alkali media has high requirements for the corrosion prevention of production plants, equipment, etc., which increases the production and operation costs of enterprises.

[0006] In summary, there is currently no mature standalone treatment technology for sulfuric acid electroslag. Existing conventional processes that mix it with acid sludge are insufficient to meet the current industry demands for green metallurgy and efficient resource utilization.

[0007] Therefore, developing a high-efficiency recycling technology for the separate treatment of sulfuric acid electroslag to achieve deep separation and high-value recovery of selenium and mercury elements, while reducing wastewater discharge and treatment costs, is of great significance for improving the utilization efficiency of non-ferrous metal by-product resources and alleviating environmental governance pressure, and has significant economic benefits and environmental value. Summary of the Invention

[0008] To address the shortcomings of the existing technologies, this invention provides a method for the comprehensive recycling and utilization of electroslag from acid production. This method enables the efficient separation of mercury and selenium from electroslag produced by acid production.

[0009] The specific technical solution is as follows:

[0010] A method for comprehensive recycling and utilization of electroslag residue from acid production includes the following steps:

[0011] S1. Pulping: Electro-fog slag, mercury-containing crude selenium, and concentrated sulfuric acid are mixed and pulverized to obtain pulverized material;

[0012] S2. Primary acid roasting: The slurry material obtained in step S1 is fed into a roasting furnace for roasting at a temperature of 220~320℃ for 20~60 h. The negative pressure inside the furnace during the roasting process is 0~-50 Pa. Primary roasting slag is obtained. Selenium dioxide is recovered by settling the roasting flue gas.

[0013] S3. Secondary roasting: The primary roasting residue obtained in step S2 is roasted again at a roasting temperature of 340~440℃ for 3~10 h, and the negative pressure inside the furnace during the roasting process is -50~-200 Pa; secondary roasting residue is obtained; mercury-containing crude selenium is recovered from the roasting flue gas.

[0014] The acid production mentioned above refers to the preparation of sulfuric acid, specifically the preparation of sulfuric acid from smelting flue gas, especially from smelting flue gas generated during the pyrometallurgical processes of copper, lead, zinc, and nickel, or during the roasting pretreatment process of gold production.

[0015] The electro-fogging slag mentioned above refers to the slag produced by solid-solid separation after the acid mist in the electrostatic precipitator is condensed during the acid production process.

[0016] Specifically, the main components of the electro-fogging slag include: selenium content of 60wt%~80wt% and mercury content of 5wt%~20wt%. The electro-fogging slag also includes: lead content of 8wt%~13wt% and sulfur content of 1wt%~3wt%.

[0017] Specifically, the electro-fogging slag contains: gold content ≤3 g / t and silver content 20~40 g / t.

[0018] The mercury-containing crude selenium can be derived from the pre-processed acid sludge produced by a non-ferrous smelter, or it can be the mercury-containing crude selenium obtained in step S3 of this invention. In the mercury-containing crude selenium, selenium mainly exists in the form of elemental mercury selenide.

[0019] Specifically, the main components of the mercury-containing crude selenium include: mercury content of 3wt%~20wt% and selenium content of 55wt%~85wt%.

[0020] The mechanism of the above method is as follows:

[0021] The electrostatic precipitator residue produced during sulfuric acid production mainly contains elements such as selenium, mercury, and lead. Selenium primarily exists in its elemental form as mercuric selenide. During the slurrying and primary low-temperature acid roasting processes, due to the low roasting temperature (below 320℃), concentrated sulfuric acid does not decompose significantly. The low-temperature acid roasting process mainly involves the reaction of elemental selenium with concentrated sulfuric acid and the decomposition of selenite. The SeO2 and SO2 produced during the reaction enter the flue gas. The SeO2-containing flue gas gradually condenses, settles, and is collected in the settling chamber, while the tail gas is sent to the absorption tower for absorption. During the low-temperature acid roasting process, undecomposed concentrated sulfuric acid forms a liquid seal layer on the material surface. Due to the presence of this liquid seal layer, oxygen in the air has difficulty passing through it to participate in the conversion reaction of mercuric selenide. At the same time, trace amounts of elemental mercury in the material also have difficulty volatilizing through the liquid seal layer into the flue gas, thus achieving effective separation of selenium and mercury.

[0022] After the first acid roasting, the main component of the roasting residue is some unreacted mercuric selenide. During the second roasting process, the roasting temperature is relatively high (340~440℃), and the main reactions are the decomposition of concentrated sulfuric acid, the conversion of mercuric selenide, and the decomposition of selenite. Mercuric selenide is converted into HgSO4 and SeO2. Since the second roasting temperature (below 440℃) is lower than the decomposition temperature of mercuric sulfate, most of the mercuric sulfate does not decompose and is enriched in the roasting residue. SeO2 and a small amount of Hg volatilize into the flue gas and are reduced to mercury-containing crude selenium in the selenium absorption tower. The mercury-containing crude selenium can be returned to the pulping step for further processing, thereby achieving complete selenium recovery.

[0023] The roasting residue after secondary roasting mainly consists of lead sulfate, mercuric sulfate, etc. This residue is sent to a mercury distillation system to recover mercury and produce distillation residue. The distillation residue is then returned to the lead smelting system to recover metals such as lead, gold, and silver.

[0024] Specifically, the equations for the main reactions in steps S1 and S2 are as follows:

[0025] Se+2H2SO4→H2SeO3+2SO2+H2O;

[0026] H2SeO3→SeO2+H2O.

[0027] Specifically, the main reaction equation for step S3 is as follows:

[0028] 2HgSe+2H2SO4+3O2→2HgSO4+2H2SeO3;

[0029] H2SeO3→SeO2+H2O;

[0030] 2H₂SO₄→2SO₂+O₂+2H₂O.

[0031] Furthermore, in step S1, the pulping time is preferably 1 to 2 hours.

[0032] Furthermore, in step S1, the ratio of electro-fogging residue to concentrated sulfuric acid is 1 g: (1.1~2.5) mL.

[0033] The concentrated sulfuric acid mentioned refers to sulfuric acid with a concentration of 70 wt% or higher, preferably 98 wt%.

[0034] Furthermore, in step S1, the preferred mass ratio of electro-fog slag to mercury-containing crude selenium is 1:(0.1~1.0).

[0035] Furthermore, in step S2: the roasting flue gas is sent into a settling chamber to recover selenium dioxide. The inlet temperature of the settling chamber is preferably 220~320℃, and the outlet temperature is preferably 120~150℃.

[0036] Further, in step S3: the roasting flue gas is sent into a selenium absorption tower to recover mercury-containing crude selenium. Specifically, SeO2 and a small amount of Hg volatilize into the flue gas. In the selenium absorption tower, the SeO2 and a small amount of Hg in the roasting flue gas dissolve in water and are simultaneously reduced by SO2 to obtain mercury-containing crude selenium.

[0037] Furthermore, the secondary roasting residue obtained in step S3 is fed into a mercury distillation system to obtain crude mercury and distillation residue. The main components of the secondary roasting residue are lead sulfate, mercuric sulfate, etc.

[0038] Furthermore, the distillation residue is returned to the lead smelting system to recover valuable metals, thereby achieving the recovery of metals such as lead, gold, and silver.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] This invention achieves effective separation and efficient recovery of selenium and mercury by subjecting the electro-fogging slag from concentrated sulfuric acid slurry to mercury-containing crude selenium through a secondary roasting process at different temperatures. The resulting selenium dioxide product has high purity, and valuable metals such as selenium, mercury, lead, gold, and silver are recovered in stages. Furthermore, the method of this invention produces low wastewater discharge, reducing environmental pressure and treatment costs. Detailed Implementation

[0041] The embodiments of the present invention will be described in further detail below with reference to the examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0042] Example 1

[0043] The electroslag from acid production is comprehensively recycled and utilized. The electroslag used contains: 73.04 wt% selenium, 5.96 wt% mercury, 8.92 wt% lead, 2.90 wt% sulfur, 0.6 g / t gold, and 35.63 g / t silver. The mercury-containing crude selenium used contains: 61.28 wt% selenium, 15.09 wt% mercury, and 0.74 wt% lead.

[0044] The steps are as follows:

[0045] S1. Pulping: Electro-fogging slag, mercury-containing crude selenium and concentrated sulfuric acid (98wt%) are mixed and pulverized for 1.5 h to obtain pulverized material; the ratio of electro-fogging slag to concentrated sulfuric acid is 1 g: 1.1 mL; the mass ratio of electro-fogging slag to mercury-containing crude selenium is 1:0.1.

[0046] S2. Primary acid roasting: The slurry material obtained in step S1 is fed into a roasting furnace for roasting. The roasting furnace is a muffle furnace with a roasting temperature of 280°C and a roasting time of 45 h. The furnace pressure is 0 Pa during the roasting process. Primary roasting slag is obtained. The roasting flue gas is sent into a settling chamber to recover selenium dioxide. The inlet temperature of the settling chamber is 280°C and the outlet temperature is 135°C.

[0047] S3. Secondary roasting: The primary roasting residue obtained in step S2 is roasted again at a temperature of 400℃ for 6 hours, with a negative pressure of -150 Pa inside the furnace during the roasting process; secondary roasting residue is obtained; the roasting flue gas is sent to a selenium absorption tower to recover mercury-containing crude selenium. The mercury-containing crude selenium is returned to step S1 for recovery again.

[0048] S4. Valuable metal recovery: The secondary roasting residue obtained in step S3 is sent to the mercury distillation system to obtain crude mercury and distillation residue; the distillation residue is returned to the lead smelting system to recover valuable metals such as lead, gold, and silver.

[0049] Example 2

[0050] The electroslag from acid production is comprehensively recycled and utilized. The electroslag used contains: 66.22 wt% selenium, 9.08 wt% mercury, 12.94 wt% lead, 1.54 wt% sulfur, 0.42 g / t gold, and 28.56 g / t silver. The mercury-containing crude selenium used contains: 74.28 wt% selenium, 7.99 wt% mercury, and 0.11 wt% lead.

[0051] The steps are as follows:

[0052] S1. Pulping: Electro-fogging slag, mercury-containing crude selenium and concentrated sulfuric acid (98wt%) are mixed and pulverized for 1 h to obtain pulverized material; the ratio of electro-fogging slag to concentrated sulfuric acid is 1 g: 2.5 mL; the mass ratio of electro-fogging slag to mercury-containing crude selenium is 1:1.

[0053] S2. Primary acid roasting: The slurry material obtained in step S1 is fed into a roasting furnace for roasting. The roasting furnace is a muffle furnace with a roasting temperature of 220°C and a roasting time of 60 h. The negative pressure inside the furnace during the roasting process is -50 Pa. Primary roasting slag is obtained. The roasting flue gas is sent into a settling chamber to recover selenium dioxide. The inlet temperature of the settling chamber is 220°C and the outlet temperature is 120°C.

[0054] S3. Secondary roasting: The primary roasting residue obtained in step S2 is roasted again at a temperature of 340℃ for 10 hours, with a negative pressure of -200 Pa inside the furnace during the roasting process; secondary roasting residue is obtained; the roasting flue gas is sent to a selenium absorption tower to recover mercury-containing crude selenium. The mercury-containing crude selenium is returned to step S1 for recovery again.

[0055] S4. Valuable metal recovery: The secondary roasting residue obtained in step S3 is sent to the mercury distillation system to obtain crude mercury and distillation residue; the distillation residue is returned to the lead smelting system to recover valuable metals such as lead, gold, and silver.

[0056] Example 3

[0057] The electroslag from acid production is comprehensively recycled and utilized. The electroslag used contains: 68.32 wt% selenium, 10.13 wt% mercury, 8.32 wt% lead, 2.05 wt% sulfur, 0.48 g / t gold, and 30.96 g / t silver. The mercury-containing crude selenium used contains: 65.84 wt% selenium, 12.74 wt% mercury, and 0.08 wt% lead.

[0058] The steps are as follows:

[0059] S1. Pulping: Electro-fogging slag, mercury-containing crude selenium and concentrated sulfuric acid (98wt%) are mixed and pulverized for 2 h to obtain pulverized material; the ratio of electro-fogging slag to concentrated sulfuric acid is 1 g: 1.5 mL; the mass ratio of electro-fogging slag to mercury-containing crude selenium is 1:0.3.

[0060] S2. Primary acid roasting: The slurry material obtained in step S1 is fed into a roasting furnace for roasting. The roasting furnace is a muffle furnace with a roasting temperature of 320℃ and a roasting time of 20 h. The negative pressure inside the furnace during the roasting process is -40 Pa. Primary roasting slag is obtained. The roasting flue gas is sent into a settling chamber to recover selenium dioxide. The inlet temperature of the settling chamber is 320℃ and the outlet temperature is 150℃.

[0061] S3. Secondary roasting: The primary roasting residue obtained in step S2 is roasted again at a temperature of 440℃ for 3 hours, with a negative pressure of -50 Pa inside the furnace during the roasting process; secondary roasting residue is obtained; the roasting flue gas is sent to a selenium absorption tower to recover mercury-containing crude selenium. The mercury-containing crude selenium is returned to step S1 for recovery again.

[0062] S4. Valuable metal recovery: The secondary roasting residue obtained in step S3 is sent to the mercury distillation system to obtain crude mercury and distillation residue; the distillation residue is returned to the lead smelting system to recover valuable metals such as lead, gold, and silver.

[0063] Comparative Example 1

[0064] Referring to Example 1, the difference from Example 1 is that the low-temperature roasting in step S2 is omitted, and the slurry material is directly roasted according to the conditions of step S3. Other technical features are the same as in Example 1.

[0065] test

[0066] The purity of selenium dioxide and its Hg content in each example and comparative example were tested. The selenium and mercury contents in the mercury-containing crude selenium obtained in each example were tested. The contents of each valuable element in the distillation residue of each example and comparative example were tested. The selenium recovery rate of each example was calculated. The selenium dioxide content was tested according to YS / T 715.1-2009 "Chemical Analysis Method for Selenium Dioxide". The contents of selenium, mercury, lead, gold, and silver were tested according to GB / T8152-2006 "Chemical Analysis Method for Lead Concentrate". The results of the purity of selenium dioxide and its Hg content are shown in Table 1. The selenium and mercury contents in the mercury-containing crude selenium are shown in Table 2. The selenium recovery rate is shown in Table 3. The contents of each valuable element in the distillation residue are shown in Table 4.

[0067] Table 1. Purity of selenium dioxide and its Hg content obtained from each example and comparative example.

[0068]

[0069] Table 2. Selenium and mercury content in the mercury-containing crude selenium obtained from each example.

[0070]

[0071] Table 3 Se recovery rates for each embodiment

[0072]

[0073] Table 4. Content of valuable elements in the distillation residues of each example and comparative example.

[0074]

[0075] Test data shows that the method of this invention can obtain high-purity selenium dioxide, with a purity exceeding 98%, and can almost completely remove mercury from selenium dioxide. In contrast, Comparative Example 1 failed to completely separate mercury and selenium, resulting in a purity far lower than the examples, and the selenium dioxide product contained a higher mercury content. The low selenium and mercury content in the distillation residue demonstrates the efficient removal and recovery of selenium and mercury.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for comprehensive recycling and utilization of electroslag residue from acid production, characterized in that, Includes the following steps: S1. Slurrying: Electro-fogging slag, mercury-containing crude selenium, and concentrated sulfuric acid are mixed and slurried to obtain slurry material; in the mercury-containing crude selenium, selenium mainly exists in the form of elemental mercury selenide; the ratio of electro-fogging slag to concentrated sulfuric acid is 1 g : (1.1~2.5) mL; the mass ratio of electro-fogging slag to mercury-containing crude selenium is 1 : (0.1~1.0); the concentration of concentrated sulfuric acid is 98 wt%. S2. Primary acid roasting: The slurry material obtained in step S1 is fed into a roasting furnace for roasting at a temperature of 220~320℃ for 20~60 h. The negative pressure inside the furnace during the roasting process is 0~-50 Pa. Primary roasting slag is obtained. Selenium dioxide is recovered by settling the roasting flue gas. S3. Secondary roasting: The primary roasting residue obtained in step S2 is roasted again at a temperature of 340~440℃ for 3~10 h. The negative pressure inside the furnace is controlled at -50~-200 Pa during the roasting process to obtain secondary roasting residue. Mercury-containing crude selenium is recovered from the roasting flue gas.

2. The method according to claim 1, characterized in that, In step S1: the pulping time is 1~2 h.

3. The method according to claim 1, characterized in that, In step S2: the roasting flue gas is sent into the settling chamber to recover selenium dioxide; the inlet temperature of the settling chamber is 220~320℃ and the outlet temperature is 120~150℃.

4. The method according to claim 1, characterized in that, Return the mercury-containing crude selenium obtained in step S3 to step S1.

5. The method according to claim 1, characterized in that, In step S3: the roasting flue gas is sent into a selenium absorption tower to recover mercury-containing crude selenium.

6. The method according to claim 1, characterized in that, The secondary roasting residue obtained in step S3 is fed into a mercury distillation system to obtain crude mercury and distillation residue.

7. The method according to claim 6, characterized in that, The distillation residue is returned to the lead smelting system to recover valuable metals.

8. The method according to any one of claims 1 to 7, characterized in that, The electro-fogging slag contains 60wt%~80wt% selenium and 5wt%~20wt% mercury.

9. The method according to claim 8, characterized in that, The electro-fogging slag contains 8wt%~13wt% lead and 1wt%~3wt% sulfur.

10. The method according to claim 8, characterized in that, The electro-fogging slag contains: gold content ≤3 g / t and silver content 20~40 g / t.

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