Method for harmless filling and treatment of goaf by using phosphorus tailings

Abstract

The application is a method for treating goaf by harmless filling of phosphor tailings, which first treats the phosphor tailings into general industrial solid waste I, and the treatment method uses tailings slurry generated by a phosphor flotation plant as raw material, adjusts the pH value to neutral by adding quicklime or lime milk after thickening, and then performs 2 times of filtration treatment, adds the filtrate of secondary filtration into the obtained filter cake, adjusts to paste state, obtains phosphor tailings paste, and fills the open pit to realize open pit treatment and ecological restoration. The method can treat the tailings slurry generated by the phosphor flotation plant into I-class solid waste, can store the tailings without building a new tailings pond, and under the condition that the state does not approve the new tailings pond, the tailings treated to reach the I-class solid waste discharge standard can fill and treat the open pit, and under the premise of harmless treatment of the phosphor tailings, the safety hazard of the open pit is eliminated.

Description

Technical Field

[0001] This invention relates to a method for treating phosphorus tailings, and more particularly to a method for harmlessly backfilling phosphorus tailings to treat mined-out areas. Background Technology

[0002] The disposal of phosphate tailings after flotation has always been a difficult problem. Currently, relevant domestic enterprises mainly use tailings dams for wet or dry tailings disposal. Regardless of whether wet or dry tailings are used, with the expansion of phosphate mining scale and the extension of mine service life, the capacity of tailings dams is decreasing year by year, the construction and operation management costs of tailings dams are constantly increasing, and tailings dams pose serious safety hazards, with the possibility of dam failure, which seriously threatens the lives and property of people around the dam area.

[0003] In Yunnan and Guizhou provinces of China, some open-pit phosphate mines require timely backfilling after mining operations cease. Prolonged water accumulation in these pits can easily cause damage, and exposed slopes may lead to landslides and other geological disasters. Furthermore, the large amounts of soluble phosphorus and fluorine in phosphate tailings are primarily found in the aqueous phase. If these are not properly treated and directly stored in open pits, the phosphorus and fluorine levels in the tailings leachate will exceed standards, polluting the environment.

[0004] Phosphate tailings that are not subjected to harmless treatment belong to Class II general industrial solid waste. If they are stored in open pits, a geomembrane must be laid at the bottom of the pit, and a complete tailings leachate collection system and a corresponding leachate treatment system must be established. However, laying a geomembrane at the bottom of the open pit is too costly, and it is difficult to guarantee that there will be no leakage in the future.

[0005] Chinese patent publications CN201110164227.6, entitled "A Method for Dry Disposal of Phosphorus Tailings" and CN201510962902.8, entitled "A Method for Dry Disposal of Phosphorus Tailings in Mineral Processing," respectively describe methods for dry disposal of phosphorus tailings.

[0006] A method for dry disposal of phosphate tailings includes the following steps: phosphate ore used in production is ground into a slurry using a grinding mill; impurities, i.e., phosphate tailings, are removed from the ore through reverse flotation; the dilute-concentration fine-particle tailings from the flotation are pumped to a tailings thickening tank for concentration; the concentrated tailings slurry is pumped to a vertical filter press for compression using a tailings underflow pump; the compressed tailings residue is transported to a slag yard for stockpiling; the water from the filter press and the clarified overflow from the thickening tank are directly recycled after settling in a sedimentation tank. The above-mentioned method for dry disposal of phosphate tailings has the following disadvantages:

[0007] (1) Only the phosphorus tailings are dehydrated. After dehydration, the phosphorus tailings belong to Class II general industrial solid waste, and the tailings leachate still pollutes the environment.

[0008] (2) This method of storing tailings still requires the construction of tailings dams, but it is changed to dry tailings discharge.

[0009] (3) The tailings after dewatering cannot be directly piled in the open pit, so the open pit is filled and treated.

[0010] A method for dry discharge of phosphorus tailings in mineral processing includes the following process: the phosphorus tailings slurry after flotation is first concentrated by a thickener, and 0-0.1% flocculant is added to accelerate particle settling. The overflow water from the thickener is returned to the mineral processing production process for recycling. After the slurry is concentrated to a concentration of more than 25%, it is discharged into a slurry storage tank and then pumped into a fully open high-efficiency automatic filter press for dewatering and filtration by a slurry pump. The filtrate is returned to the thickener. The filtered filter cake is unloaded by a designed automatic slag discharge device onto a belt conveyor at the lower end of the filter press and sent to the tailings dump or mining area for backfilling, thereby realizing the dry discharge of flotation phosphorus tailings.

[0011] The above-mentioned dry disposal method for phosphorus tailings has the following disadvantages:

[0012] (1) Only the phosphorus tailings are dehydrated. After dehydration, the phosphorus tailings belong to Class II general industrial solid waste, and the tailings leachate still pollutes the environment.

[0013] (2) This method of storing tailings still requires the construction of tailings dams, but it is changed to dry tailings discharge.

[0014] (3) The tailings after dewatering cannot be directly piled in the open pit, so the open pit is filled and treated.

[0015] (4) After the slurry is thickened, the concentration only increases to about 25%, and the subsequent dewatering effect of the high-efficiency automatic filter press is poor. Summary of the Invention

[0016] The technical problem to be solved by the present invention is to provide a new method for harmlessly filling and treating mining voids with phosphorus tailings, which addresses the shortcomings of the existing technology. This method treats phosphorus tailings after flotation to make them meet the Class I standard of general industrial solid waste, and uses a paste filling method to fill and treat mining voids. Under the premise of low treatment cost, it not only treats a large amount of tailings, but also eliminates the safety hazards of open pits.

[0017] The technical problem to be solved by this invention is achieved through the following technical solution. This invention is a method for harmlessly filling and treating mined-out areas with phosphate tailings. The method is characterized by first treating the phosphate tailings as Class I general industrial solid waste. The treatment method uses tailings slurry produced by a phosphate flotation plant as raw material. After thickening, quicklime or lime milk is added to adjust the pH value to neutral. The slurry is then transported to a filter for primary filtration, washing, and secondary filtration. The resulting filter cake is mixed with the filtrate from the secondary filtration to form phosphate tailings paste. The phosphate tailings paste is then used to fill the mined-out areas (open pits).

[0018] The method for harmlessly backfilling and treating mined-out areas using phosphorus tailings, as described above, has the following further preferred technical steps:

[0019] (1) The following method is used to treat phosphate tailings as Class I general industrial solid waste: The tailings slurry generated by the phosphate flotation plant is thickened to a mass concentration of 55%-58% by a thickener. Quicklime or lime milk is added to the tailings slurry to adjust its pH value to neutral. After thickening to a mass concentration of 50%-55%, it is transported through pipeline to the tailings filtration system slurry storage tank. Then it is transported to the filter for primary filtration to obtain a primary filter cake with a moisture content of 13%-17%. The primary filter cake is transported to the slurry conditioning tank for slurry conditioning. 5-7 times the amount of water in the primary filter cake is added and stirred for 20-30 minutes. After the slurry is conditioned to a concentration of 40%-47%, it is transported to the filter for secondary filtration to obtain a secondary filter cake with a moisture content of 13%-17%.

[0020] (2) Paste preparation and filling: Add the filtrate from the second filtration to the secondary filter cake obtained in step (1) and adjust it to a paste state with a mass concentration of 75%-78% to obtain phosphorus tailings paste. Use a filling industrial pump to transport the phosphorus tailings paste to the goaf (open pit) for filling, so as to realize the treatment and ecological restoration of the goaf (open pit).

[0021] A further preferred technical solution of the above-described method for harmless filling and treatment of mining voids is to treat the slopes and platforms formed after the completion of filling and treatment of mining voids (open pits) by planting grass, shrubs, and vegetation to stabilize the soil and seal the slopes.

[0022] A further preferred technical solution of the above-described method for harmless backfilling and treatment of mining goaf areas using phosphorus tailings is as follows: the filtrate obtained after primary and secondary filtration flows by gravity to the return water tank; part of the clarified water in the return water tank is returned to the filtration system for recycling, part is used as water for preparing paste, and the remaining return water is then returned to the flotation plant for recycling via a pipeline.

[0023] A further preferred technical solution of the above-described method for harmless filling and treatment of mining goaf with phosphorus tailings is that the moisture content of the primary and secondary filter cakes after filtration is 15%.

[0024] A further preferred technical solution of the above-described method for harmless filling and treatment of mining goaf with phosphorus tailings is that both primary and secondary filtration adopt a new type of belt vacuum filter.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The tailings of the present invention can meet the Class I solid waste discharge standard after one filtration + water washing + two filtrations. Tailings can be stored without building a new tailings dam. In the case that the state does not approve the construction of new tailings dams, the tailings that meet the Class I solid waste discharge standard after treatment can be used to fill and treat the goaf (open pit). A raw material that can treat the goaf (open pit) has been found, eliminating the safety hazards of the open pit.

[0027] (2) Tailings that meet the Class I solid waste discharge standard after treatment do not require the installation of an impermeable membrane in any location, which greatly reduces the cost of tailings storage. The stored tailings and their leachate will not pollute the surrounding environment. The filtrate after secondary filtration and the tailings that meet the Class I solid waste discharge standard are mixed into a paste and pumped to fill and treat the goaf (open pit), which reduces the leachate from the stored tailings. No new leachate treatment facilities need to be built subsequently.

[0028] (3) Using the method of preparing paste to transport tailings greatly reduces the cost of tailings transportation compared to using belt conveyors, and is easy to operate.

[0029] (4) The use of a new type of belt vacuum filter for tailings dewatering significantly reduces costs compared to high-efficiency filter presses and vertical filter presses. For a phosphate mine tailings in Guizhou, the cost of using the new type of belt vacuum filter is only about 11 yuan per ton. Moreover, the output of the new type of belt vacuum filter is continuous and stable. The filter cloth of the new type of belt vacuum filter can be cleaned directly with the filtrate after filtration, which is safe, environmentally friendly, simple and feasible. Detailed Implementation

[0030] The specific technical solutions of the present invention are further described below to enable those skilled in the art to further understand the present invention, without constituting a limitation on its rights.

[0031] Example 1: A method for harmlessly backfilling and treating mined-out areas with phosphorus tailings, the steps of which are as follows:

[0032] (1) The following method is used to treat phosphate tailings as Class I general industrial solid waste: The tailings slurry generated by the phosphate flotation plant is thickened to a mass concentration of 58% by a thickener. Quicklime or lime milk is added to the tailings slurry to adjust its pH value to neutral. After thickening to a mass concentration of 55%, it is transported through a pipeline to the tailings filtration system slurry storage tank. Then it is transported to the filter for primary filtration to obtain a primary filter cake with a moisture content of 13%. The primary filter cake is transported to the slurry conditioning tank for slurry conditioning. Five times the amount of water in the primary filter cake is added and stirred for 20 minutes. After the slurry is conditioned to a concentration of 40%, it is transported to the filter for secondary filtration to obtain a secondary filter cake with a moisture content of 13%.

[0033] (2) Paste preparation and filling: Add the filtrate from the secondary filtration to the secondary filter cake obtained in step (1) and adjust it to a paste state with a mass concentration of 75% to obtain phosphorus tailings paste. Use a filling industrial pump to transport the phosphorus tailings paste to the open pit for filling, so as to realize the treatment and ecological restoration of the open pit.

[0034] The slopes and platforms formed after the open-pit filling and treatment were treated using revegetation methods such as planting grass, shrubs, and vegetation to stabilize the soil and seal the slopes. The filtrates from both primary and secondary filtration flowed by gravity to the return water tank; part of the clarified water in the return water tank was returned to the filtration system for recycling, part was used as water for preparing pastes, and the remaining return water was then transported back to the flotation plant for recycling. Both primary and secondary filtration employed a new type of belt vacuum filter.

[0035] The tailings slurry from a phosphate rock flotation plant is thickened to a mass concentration of 55% using a thickener. At a pH of 4.83-5.21, its total phosphorus content is 1727-1813 mg / L, fluorine content is 21.6-22.7 mg / L, and arsenic content is 0.6357-0.6675 mg / L. The phosphate tailings filter cake treated by the method of this invention has a total phosphorus content of 0.04-0.14 mg / L, a fluorine content of 4-4.2 mg / L, and no arsenic detected. All indicators meet the Class I general industrial solid waste standards in the "Standards for Pollution Control of Hazardous Waste Storage and Disposal".

[0036] Example 2: A method for harmlessly backfilling and treating mined-out areas with phosphorus tailings, the steps of which are as follows:

[0037] (1) The following method is used to treat phosphate tailings as Class I general industrial solid waste: The tailings slurry generated by the phosphate flotation plant is thickened to a mass concentration of 55% by a thickener. Quicklime or lime milk is added to the tailings slurry to adjust its pH value to neutral. After thickening to a mass concentration of 55%, it is transported through a pipeline to the tailings filtration system slurry storage tank, and then transported to the filter for primary filtration to obtain a primary filter cake with a moisture content of 13%. The primary filter cake is transported to the slurry conditioning tank for slurry conditioning. Five times the amount of water in the primary filter cake is added and stirred for 30 minutes. After the slurry is conditioned to a concentration of 47%, it is transported to the filter for secondary filtration to obtain a secondary filter cake with a moisture content of 17%.

[0038] (2) Paste preparation and filling: Add the filtrate from the second filtration to the secondary filter cake obtained in step (1) and adjust it to a paste state with a mass concentration of 78% to obtain phosphorus tailings paste. Use a filling industrial pump to transport the phosphorus tailings paste to the open pit for filling, so as to realize the treatment and ecological restoration of the open pit.

[0039] The slopes and platforms formed after the open-pit filling and treatment were treated using revegetation methods such as planting grass, shrubs, and vegetation to stabilize the soil and seal the slopes. The filtrates from both primary and secondary filtration flowed by gravity to the return water tank; part of the clarified water in the return water tank was returned to the filtration system for recycling, part was used as water for preparing pastes, and the remaining return water was then transported back to the flotation plant for recycling. Both primary and secondary filtration employed a new type of belt vacuum filter.

[0040] Untreated tailings slurry with a concentration of 55% and a pH of 4.83 had a total phosphorus content of 1727 mg / L, a fluorine content of 21.6 mg / L, and an arsenic content of 0.6357 mg / L. The phosphorus tailings filter cake treated using this patented method had a total phosphorus content of 0.04 mg / L, a fluorine content of 4 mg / L, and no detectable arsenic. All indicators met the Class I general industrial solid waste standards in the "Standards for Pollution Control of Hazardous Waste Storage and Disposal".

[0041] Example 3: A method for harmlessly backfilling and treating mined-out areas with phosphorus tailings, the steps of which are as follows:

[0042] (1) The following method is used to treat phosphate tailings as Class I general industrial solid waste: The tailings slurry generated by the phosphate flotation plant is thickened to a mass concentration of 56% by a thickener. Quicklime or lime milk is added to the tailings slurry to adjust its pH value to neutral. After thickening to a mass concentration of 53%, it is transported through a pipeline to the tailings filtration system slurry storage tank. Then it is transported to the filter for primary filtration to obtain a primary filter cake with a moisture content of 15%. The primary filter cake is transported to the slurry conditioning tank for slurry conditioning. Five times the amount of water in the primary filter cake is added and stirred for 25 minutes. After the slurry is conditioned to a concentration of 40%, it is transported to the filter for secondary filtration to obtain a secondary filter cake with a moisture content of 15%.

[0043] (2) Paste preparation and filling: Add the filtrate from the second filtration to the secondary filter cake obtained in step (1) and adjust it to a paste state with a mass concentration of 76% to obtain phosphorus tailings paste. Use a filling industrial pump to transport the phosphorus tailings paste to the open pit for filling, so as to realize the treatment and ecological restoration of the open pit.

[0044] After the open pit filling and treatment is completed, the resulting slopes and platforms are treated with revegetation methods such as planting grass, shrubs, and vegetation to stabilize the soil and seal the slopes.

[0045] The filtrates obtained from the first and second filtrations flow by gravity to the return water tank. Part of the clarified water in the return water tank is returned to the filtration system for recycling, part is used as water for preparing pastes, and the remaining return water is then returned to the flotation plant for recycling via a pipeline.

[0046] Both primary and secondary filtration utilize a new type of belt vacuum filter.

[0047] The tailings slurry with a concentration of 56%, without treatment in this experiment, had a total phosphorus content of 1813 mg / L, a fluorine content of 22.7 mg / L, and an arsenic content of 0.6675 mg / L at a pH of 5.21. The phosphorus tailings filter cake treated using this patented method had a total phosphorus content of 0.14 mg / L, a fluorine content of 4.2 mg / L, and no detectable arsenic. All indicators met the Class I general industrial solid waste standards in the "Standards for Pollution Control of Hazardous Waste Storage and Disposal".

[0048] Example 4: An experimental method for harmlessly filling and treating goaf areas with phosphorus tailings. The following two sets of experiments were conducted using the method of Example 3, and the relevant parameters are shown in the table below:

[0049]

[0050] The two sets of experiments above demonstrate that the treatment method involved in the harmless backfilling and treatment of mining voids using phosphorus tailings in this invention has excellent results.

Claims

1. A method for treating goaf by harmless filling of phosphorous tailings, characterized in that, The method first treats the phosphate tailings as Class I general industrial solid waste. The treatment method uses the tailings slurry produced by the phosphate flotation plant as raw material. After thickening, quicklime or lime milk is added to adjust the pH value to neutral. The slurry is then transported to a filter for primary filtration, washing, and secondary filtration. The resulting filter cake is mixed with the filtrate from the secondary filtration to form phosphate tailings paste. The phosphate tailings paste is then used to fill the goaf. The specific steps are as follows: (1) The following method is used to treat phosphate tailings as Class I general industrial solid waste: The tailings slurry generated by the phosphate flotation plant is thickened to a mass concentration of 55%-58% by a thickener. Quicklime or lime milk is added to the tailings slurry to adjust its pH value to neutral. After thickening to a mass concentration of 50%-55%, it is transported through pipeline to the tailings filtration system slurry storage tank. Then it is transported to the filter for primary filtration to obtain a primary filter cake with a moisture content of 13%-17%. The primary filter cake is transported to the slurry conditioning tank for slurry conditioning. 5-7 times the amount of water in the primary filter cake is added and stirred for 20-30 minutes. After the slurry is conditioned to a concentration of 40%-47%, it is transported to the filter for secondary filtration to obtain a secondary filter cake with a moisture content of 13%-17%. (2) Paste preparation and filling: Add the filtrate from the second filtration to the secondary filter cake obtained in step (1) and adjust it to a paste state with a mass concentration of 75%-78% to obtain phosphorus tailings paste. Use a filling industrial pump to transport the phosphorus tailings paste to the goaf for filling.

2. The method for treating and filling goaf with phosphorous tailings according to claim 1, characterized in that: After the completion of the filling and treatment of the mining subsidence area, the slopes and platforms formed are treated by planting grass, shrubs and vegetation to stabilize the soil and seal the slopes.

3. The method for treating and filling goaf with phosphorous tailings according to claim 1, characterized in that: The filtrates obtained from the first and second filtrations flow by gravity to the return water tank. Part of the clarified water in the return water tank is returned to the filtration system for recycling, part is used as water for preparing pastes, and the remaining return water is then returned to the flotation plant for recycling via a pipeline.

4. The method for treating and filling goaf with phosphorous tailings according to claim 1, characterized in that: The moisture content of the primary and secondary filter cakes after filtration is 15%.

5. The method for harmlessly backfilling and treating mined-out areas using phosphorus tailings according to claim 1, characterized in that: Both primary and secondary filtration utilize a new type of belt vacuum filter.

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