A full solid waste filling system and method under alkali-washed phosphogypsum pretreatment

Abstract

The present invention discloses a full solid waste filling system and method under alkali-washed phosphogypsum pretreatment, which realizes the preliminary defluorination of high-fluorine phosphogypsum and the separation of defluorinated phosphogypsum and fluorine-containing alkaline wastewater through a phosphogypsum alkali-washing pretreatment system of a first belt conveyor, a NaOH solution storage barrel, a sand washing and dehydration integrated machine, a clean water pump and a buffer tank; an alkaline wastewater defluorination system with PAC as the main body, which adsorbs fluorine elements in alkaline wastewater through flocculation; a full solid waste cementing filling system with blast furnace slag bin, a screw weighing machine, a screw conveyor, a second belt conveyor, a strong stirring barrel and a filling industrial pump as core equipment, which stimulates blast furnace slag with potential volcanic ash activity as a cementing material through alkaline wastewater, thereby realizing the preparation of phosphogypsum cementing filling body. The present invention reduces the risk of leaching of fluorine elements in the filling body while meeting the requirements of full solid waste filling of underground goafs with phosphogypsum as filling aggregate and blast furnace slag as cementing material.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphogypsum filling, and in particular to a full solid waste filling system and method under alkali-washed phosphogypsum pretreatment. Background Art

[0002] Phosphogypsum is a major by-product emitted during the wet production of phosphoric acid. At present, the methods for recovering phosphogypsum mainly include raw materials for soil improvement, roadbed aggregates and cement production, but the comprehensive utilization rate is only about 15%. Most of the phosphogypsum is mainly handled by stacking and dumping, which poses great safety hazards and environmental pollution. In the field of mine filling, the use of phosphogypsum as a filling aggregate to meet the strength requirements of underground goafs has become a new idea for the harmless treatment of phosphogypsum. However, unlike ordinary tailings filling technology that uses inert tailings (mainly SiO 2 ) As an aggregate, the main component of the aggregate phosphogypsum used in phosphogypsum filling technology is calcium sulfate dihydrate, which is the main source of slow setting and even strength degradation of the phosphogypsum filling body. At the same time, as a by-product of phosphoric acid production, phosphogypsum contains fluorine and other harmful elements, which may pose a major threat to the groundwater environment after filling into the well. Therefore, considering the acidic characteristics of phosphogypsum, alkaline washing and defluorination pretreatment before filling is an important prerequisite for achieving phosphogypsum filling.

[0003] Although there are a large number of patents on pretreatment of phosphogypsum to remove fluorine and improve the strength of filling bodies, such as: Chinese invention patents with publication numbers CN110563364A and CN108516713A disclose a preparation method and application of modified phosphogypsum filling bodies, respectively adding CaCO to the aged phosphogypsum 3 , heavy calcium, thereby reducing the release of harmful substances and improving the resource utilization rate of phosphogypsum. The Chinese invention patent with publication number CN109704712A discloses a method for reducing phosphorus pollution in the phosphogypsum filling process by using modified quartz sand, which uses modified quartz sand as a filling aggregate and is added to the phosphogypsum filling body to reduce the precipitation of phosphorus. However, there is no precedent in the field of phosphogypsum filling that can achieve wastewater recycling and full solid waste filling while removing fluorine by alkaline washing. Summary of the invention

[0004] The object of the present invention is to provide a full solid waste filling system and method under alkaline washing phosphogypsum pretreatment. Firstly, the fluorine content in the phosphogypsum is reduced by alkaline washing pretreatment with a certain concentration of NaOH solution; secondly, the fluorine element in the alkaline wastewater is removed by adding PAC, and it is used to stimulate the potential volcanic ash activity of blast furnace slag powder and prepare filling slurry, so as to reduce the risk of fluorine leaching and efficiently utilize water resources, while realizing full solid waste filling treatment of underground goaf.

[0005] The alkali-washing pretreatment phosphogypsum low-carbon green filling system includes a phosphogypsum alkali-washing pretreatment system, a wastewater defluorination system and a full solid waste cementation filling system, wherein:

[0006] The phosphogypsum alkaline washing pretreatment system comprises a first belt conveyor, a NaOH solution storage barrel, a NaOH magnetic pump, a sand washing and dehydration integrated machine, a clean water pump and a buffer tank; the phosphogypsum from the phosphogypsum yard is respectively conveyed to the sand washing and dehydration integrated machine through the first belt conveyor, and the NaOH solution of a certain concentration in the NaOH solution storage barrel is pumped to the sand washing and dehydration integrated machine through the NaOH magnetic pump for alkaline washing pretreatment; the phosphogypsum after alkaline washing enters the buffer tank for standby use, and the alkaline fluorine-containing wastewater after alkaline washing enters the wastewater defluorination system through the clean water pump;

[0007] The wastewater defluorination system includes a PAC storage bin, a metering pump and a high-level water tank. The alkaline fluoride-containing wastewater is pumped into the high-level water tank through a clean water pump, and the PAC enters the high-level water tank from the PAC storage bin through a metering pump for defluorination treatment. The treated alkaline wastewater flows into the full solid waste cementation filling system by gravity using a high head difference;

[0008] The full solid waste bonding and filling system includes a blast furnace slag bin, a screw weighing machine, a screw conveyor, a second belt conveyor, a high-power mixing barrel and a filling industrial pump; the second belt conveyor is arranged between the buffer tank and the high-power mixing barrel, and is used to convey the phosphogypsum after alkali washing; the high-power mixing barrel is connected to the screw conveyor outlet, the second belt conveyor outlet, the high-level water tank pipeline outlet and the filling industrial pump inlet through pipelines; the blast furnace slag bin is connected to the screw weighing machine inlet, and the screw weighing machine outlet is connected to the screw conveyor inlet.

[0009] The full solid waste filling method under alkali-washed phosphogypsum pretreatment comprises the following steps:

[0010] (1) transporting the high-fluorine phosphogypsum stored in the phosphogypsum storage yard to a sand washing and dehydration integrated machine through a first belt conveyor, and simultaneously introducing a certain concentration of NaOH solution into the sand washing and dehydration integrated machine to perform alkaline washing pretreatment on the high-fluorine phosphogypsum, and drying and dehydrating the phosphogypsum after multiple alkaline washings, and separating the dry phosphogypsum with a certain water content and the alkaline fluorine-containing waste liquid;

[0011] (2) directly discharging the dried phosphogypsum in step (1) into a buffer tank for storage;

[0012] (3) transporting the alkaline fluorine-containing wastewater in step (1) to a high-level water tank through a clean water pump to defluorinate the alkaline fluorine-containing wastewater;

[0013] (4) During the filling operation, according to the filling ratio parameters and the underground filling strength requirements, the dry phosphogypsum stored in the buffer tank is transported to the strong stirring barrel by the second belt conveyor, the alkaline wastewater after the defluorination treatment in step (3) enters the strong stirring barrel by high head difference gravity, and the blast furnace slag powder in the blast furnace slag bin is weighed and measured according to a certain ratio by a screw weighing machine, and then transported to the strong stirring barrel by a screw conveyor;

[0014] (5) The homogenized all-solid waste filling slurry is stirred in a high-powered stirring barrel, and then the homogenized all-solid waste filling slurry is pumped to the underground filling area through a filling industrial pump.

[0015] Preferably, in step (1), the mass ratio of the dry weight of the high-fluorine phosphate gypsum to the NaOH solution is 1:2-3.

[0016] Preferably, in step (1), the mass fraction of the NaOH solution is 1 wt%.

[0017] Preferably, in step (1), the alkali washing time of the high-fluorine phosphate gypsum is not less than 10 minutes.

[0018] Preferably, in step (1), the rotation speed of the sand washing and dehydration machine during alkali washing is not less than 15 r / min.

[0019] Preferably, in step (4), the mass ratio of the blast furnace slag powder to the dry phosphogypsum (dry weight) is 1:6-8.

[0020] Preferably, in step (5), the mass concentration of the homogeneous all-solid waste filling slurry is 64-68%.

[0021] The technical concept of the present invention is as follows:

[0022] The cement consumption in the phosphogypsum filling process is huge, and the carbon emissions caused by cement production account for 5-7% of the world's total carbon dioxide emissions. In addition, the price is relatively expensive, and cement consumption accounts for more than 80% of the filling cost. Therefore, from the perspective of economy and environmental protection, the use of blast furnace water-quenched slag with potential volcanic ash activity as a cementitious material can greatly reduce the filling cost. On the other hand, the wastewater after alkali washing can not only be used to prepare filling slurry after PAC defluorination treatment, but the alkaline system in it is also conducive to stimulating the potential activity of blast furnace water-quenched slag and improving the strength of phosphogypsum filling.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are:

[0024] 1. Through the phosphogypsum alkaline washing pretreatment system consisting of the first belt conveyor, NaOH solution storage barrel, NaOH magnetic pump, sand washing and dehydration integrated machine, clean water pump and buffer tank, the high-fluorine phosphogypsum can be effectively defluorinated, while greatly reducing the risk of groundwater fluoride pollution after underground filling with phosphogypsum as filling aggregate;

[0025] 2. The wastewater defluorination system, which is mainly composed of PAC storage bins, metering pumps and high-level water bins, can fix the free fluoride ions in the wastewater through the flocculation and adsorption of alkaline fluoride-containing wastewater by PAC, and can also pass the treated alkaline wastewater into the full solid waste cementation filling system as alkaline activator and filling slurry preparation water, thus achieving the environmental protection goal of efficient utilization of wastewater;

[0026] 3. The full solid waste cementation filling system with blast furnace slag silo, weighing machine, screw conveyor, second belt conveyor, high-powered mixing barrel and filling industrial pump as the core, based on the alkaline pretreatment system of phosphogypsum and wastewater defluorination system, realizes the full solid waste cementation filling of bulk industrial solid waste phosphogypsum and blast furnace slag and improves the strength of the filling body, while achieving the low-carbon green goal of zero addition of ordinary Portland cement and significantly reducing the fluoride leaching in the filling body.

[0027] The system has a simple process and low equipment investment. With the synergistic effect of multiple subsystems, it can simultaneously achieve strategic goals such as harmless disposal of high-fluorine phosphate gypsum, efficient utilization of wastewater, and full solid waste filling management in goaf areas, thus helping the green transformation of the country's phosphate fertilizer industry, smelting industry and non-coal mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the full solid waste filling system under alkali-washed phosphogypsum pretreatment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] Please refer to Figure 1 The present invention proposes a full solid waste filling system and method under alkali-washed phosphogypsum pretreatment, which includes a phosphogypsum alkaline pretreatment system, a wastewater defluorination system and a full solid waste cementation filling system, wherein:

[0031] The phosphogypsum alkaline washing pretreatment system comprises a first belt conveyor, a NaOH solution storage barrel, a NaOH magnetic pump, a sand washing and dehydration integrated machine, a clean water pump and a buffer tank. The phosphogypsum from the phosphogypsum storage yard is respectively conveyed to the sand washing and dehydration integrated machine through the first belt conveyor, and the NaOH solution of a certain concentration in the NaOH solution storage barrel is pumped to the sand washing and dehydration integrated machine through the NaOH magnetic pump for alkaline washing pretreatment. The phosphogypsum after alkaline washing enters the buffer tank for standby use, and the alkaline fluoride-containing wastewater after alkaline washing enters the wastewater defluorination system through the clean water pump;

[0032] The wastewater defluorination system includes a PAC storage bin, a metering pump and a high-level water tank. The alkaline fluoride-containing wastewater is pumped into the high-level water tank through a clean water pump, and the PAC enters the high-level water tank from the PAC storage bin through a metering pump for defluorination treatment. The treated alkaline wastewater flows into the phosphogypsum low-carbon cementing filling system by gravity using a high head difference;

[0033] The full solid waste bonding and filling system includes a blast furnace slag bin, a weighing machine, a screw conveyor, a second belt conveyor, a high-power mixing barrel and a filling industrial pump; the second belt conveyor is arranged between the buffer tank and the high-power mixing barrel, and is used to convey the phosphogypsum after alkali washing; the high-power mixing barrel is connected to the screw conveyor outlet, the second belt conveyor outlet, the high-level water tank pipeline outlet and the filling industrial pump inlet through pipelines; the blast furnace slag bin is connected to the screw weighing machine inlet, and the screw weighing machine outlet is connected to the screw conveyor inlet.

[0034] Among them, the belt conveyor has a weighing function, and the weight of high-fluorine phosphogypsum and dry phosphogypsum can be weighed by the belt conveyor. The mass of a certain concentration of NaOH solution, fluorine-containing alkaline wastewater, and wastewater after defluorination treatment can be measured by the flow meter and calculated based on normal water density.

[0035] The natural density of phosphogypsum discharged by a phosphate fertilizer production enterprise in Anhui is 1.62g / cm 3 , after drying, the density is 0.86g / cm 3 , moisture content 7.2%, X-ray fluorescence spectrometer measured that the main component of the phosphogypsum is SO 3 and CaO, a small amount of P 2 O 5 and F, of which fluorine accounts for 0.97%. The particle size test shows that the mass of particles below 87.88μm in phosphogypsum accounts for 90%, and the mass of particles below 36.86μm accounts for 10%, which is an ultra-fine grained filling material. Therefore, when the concentration of phosphogypsum filling slurry is 66-68%, the yield stress reaches about 200Pa, presenting a paste / paste-like state, which leads to low strength of phosphogypsum filling body and makes it difficult to meet the underground filling requirements. At the same time, the fluorine element present in the phosphogypsum is very likely to be leached during the cementing filling treatment, posing a greater pollution risk to the underground groundwater environment. The blast furnace slag is taken from the water-quenched slag produced by a nearby smelter and is crushed and ground to a specific surface area of ​​0.20m 2 / g or above, it is sent to the blast furnace slag bin for standby use.

[0036] The following examples will use the phosphogypsum and blast furnace slag as raw materials for processing.

[0037] Example 1

[0038] (1) transporting high-fluorine phosphogypsum stored in the phosphogypsum storage yard to a sand washing and dehydration integrated machine through a first belt conveyor, and simultaneously introducing a 1wt% NaOH solution into the sand washing and dehydration integrated machine to perform an alkali washing pretreatment on the high-fluorine phosphogypsum for more than 10 minutes, wherein the rotation speed during the alkali washing is not less than 15r / min, and drying and dehydration are performed after the alkali washing, and the dry phosphogypsum with a certain water content and the alkaline fluorine-containing wastewater are separated, wherein the mass ratio of the high-fluorine phosphogypsum (dry weight) to the NaOH solution is 1:2;

[0039] (2) directly discharging the dried phosphogypsum in step (1) into a buffer tank for storage;

[0040] (3) pumping the alkaline fluorine-containing solution in step (1) to a high-level water tank by a clean water pump, and simultaneously transporting PAC powder from a PAC storage tank to a high-level water tank by a metering pump, to defluorinate the alkaline fluorine-containing wastewater, wherein the mass ratio of PAC powder to fluorine-containing wastewater is 6:10000;

[0041] (4) During the filling operation, according to the filling ratio parameters and the underground filling strength requirements, the dry phosphogypsum stored in the buffer tank is transported to the strong stirring barrel by using the second belt conveyor, the wastewater supernatant after defluorination in step (3) is transported to the strong stirring barrel by using the height difference, and the blast furnace slag powder in the blast furnace slag bin is weighed and measured by a screw weighing machine, and then mixed and stirred by a screw conveyor and transported to the strong stirring barrel, wherein the mass ratio of blast furnace slag powder to dry phosphogypsum (dry weight) is 1:6;

[0042] (5) Stirring a homogeneous all-solid waste filling slurry with a mass concentration of 66% in a strong stirring barrel, and then pumping the filling slurry to the underground filling area through a filling industrial pump;

[0043] (6) After 28 days of filling and curing, the phosphogypsum filling samples (cylindrical test blocks with a diameter of 50 mm and a height of 100 mm) were subjected to three uniaxial compressive strength tests in the laboratory, and the average value was taken as the compressive strength of the filling body;

[0044] (7) After the compressive strength test, the broken test blocks were selected and the experimental steps specified in the "Solid Waste Toxicity Leaching Method Reversal Method" (GB5086.1-1997) were used to obtain the leachate of the phosphogypsum filling body. Then, the experimental steps specified in GB 7484-87 "Determination of Fluoride in Water Quality by Ion Selective Electrode Method" were used to test the fluoride ion selective electrode method to obtain the fluoride ion concentration in the leachate of the phosphogypsum filling body, which is the fluoride leaching amount of the phosphogypsum filling body.

[0045] Example 2

[0046] According to the method of Example 1, step (1) was modified to prepare a homogeneous all-solid waste filling slurry with a mass ratio of high-fluorine phosphate gypsum (dry weight) to NaOH solution of 1:3, and the other steps remained unchanged.

[0047] Example 3

[0048] According to the method of Example 1, the mass ratio of blast furnace slag powder to phosphogypsum (dry weight) in step (4) is changed to 1:8 to prepare a homogeneous all-solid waste filling slurry, and the other steps remain unchanged.

[0049] Comparative Example 1

[0050] According to the method of Example 1, the alkaline washing pretreatment step in step (1) and the fluorine-containing wastewater adding PAC defluorination step in step (3) are omitted to prepare a homogeneous all-solid waste filling slurry, and the other steps remain unchanged.

[0051] Comparative Example 2

[0052] According to the method of Example 1, the alkaline washing pretreatment step in step (1) and the PAC defluorination step of the fluorine-containing wastewater in step (3) are omitted, and the blast furnace slag powder in step (4) is replaced with ordinary Portland cement (label 42.5) of the same mass to prepare a homogeneous filling slurry, and the other steps remain unchanged.

[0053] Comparative Example 3

[0054] According to the method of Example 1, the step of adding PAC to the fluorine-containing wastewater in step (3) to remove fluorine is omitted, and the fluorine-containing wastewater is directly used to prepare the homogeneous filling slurry, and the other steps remain unchanged.

[0055] Comparative Example 4

[0056] According to the method of Example 1, the blast furnace slag powder in step (4) is replaced with ordinary Portland cement (label 42.5) of the same mass to prepare a homogeneous filling slurry, and the other steps remain unchanged.

[0057] The uniaxial compressive strength (28 days) and fluorine leaching amount of the phosphogypsum filling bodies prepared in the comparative examples and the examples were tested, and the results are shown in the following table.

[0058] Examples Uniaxial compressive strength (MPa) Fluoride leaching amount (mg / L) Example 1 0.93 0.34 Example 2 0.95 0.21 Example 3 0.79 0.43 Comparative Example 1 0.35 7.58 Comparative Example 2 1.05 4.56 Comparative Example 3 0.82 3.12 Comparative Example 4 1.10 0.39

[0059] From the above table, by comparing Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4, it can be found that when the phosphogypsum is not pretreated and blast furnace slag powder is used as the cementing material, the filling body strength is 0.35MPa and the fluorine leaching amount is 7.58mg / L; under the same condition, when 42.5 cement is used as the cementing material, the filling body strength is 1.05MPa and the fluorine leaching amount is 4.56mg / L. When the phosphogypsum is pretreated with alkaline washing and blast furnace slag powder is used as the cementing material, the strength of the whole solid waste filling body reaches 0.93MPa, which is about 85-89% of the filling body strength of Comparative Example 2 and Comparative Example 4, and the fluorine leaching amount is reduced to 0.34mg / L. This shows that the alkaline washing pretreatment of phosphogypsum is not only an important factor in the increase of the strength of the whole solid waste filling body, but also the main source of solidifying the fluorine element and reducing the fluorine leaching amount. Therefore, under the condition of alkaline washing pretreatment, using blast furnace slag powder as cementitious material can not only meet the strength requirements of goaf filling treatment, but also control the fluorine leaching amount within 1.0 mg / L, reaching the Class I to III water standards specified in the groundwater quality standard (GB / T 14848-2017), with significant economic and environmental benefits.

[0060] By comparing Example 1 with Comparative Example 3, it can be seen that if the fluorine-containing alkali washing wastewater is not subjected to PAC defluorination treatment after alkali washing, and the wastewater is still used as water for adjusting the concentration of the filling slurry, although the strength of the all-solid waste filling body decreases slightly (0.82MPa), the fluorine leaching amount increases to 3.12mg / L (>2mg / L), which is difficult to reach the Class IV water standard specified in the groundwater quality standard (GB / T 14848-2017), and cannot meet the environmental protection requirements of phosphogypsum filling.

[0061] The uniaxial compressive strength of the all-solid waste filling bodies of Examples 1-3 is between 0.79 and 0.93 MPa, and the fluorine leaching amount is distributed between 0.21 and 0.43 mg / L, indicating that the all-solid waste filling bodies of the implementation cases of the present invention all meet the strength requirements for underground goaf filling treatment, and also meet the Class I to III water standards specified in the groundwater quality standard (GB / T 14848-2017).

[0062] The above description is only for illustrating the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A full solid waste filling system under alkali-washed phosphogypsum pretreatment, characterized in that: It includes phosphogypsum alkaline washing pretreatment system, wastewater defluorination system and full solid waste cementation filling system, among which: The phosphogypsum alkaline washing pretreatment system comprises a first belt conveyor, a NaOH solution storage barrel, a NaOH magnetic pump, a sand washing and dehydration integrated machine, a clean water pump and a buffer tank; the phosphogypsum from the phosphogypsum yard is respectively conveyed to the sand washing and dehydration integrated machine through the first belt conveyor, and the NaOH solution of a certain concentration in the NaOH solution storage barrel is pumped to the sand washing and dehydration integrated machine through the NaOH magnetic pump for alkaline washing pretreatment; the phosphogypsum after alkaline washing enters the buffer tank for standby use, and the alkaline fluorine-containing wastewater after alkaline washing enters the wastewater defluorination system through the clean water pump; The wastewater defluorination system includes a PAC storage bin, a metering pump and a high-level water tank. The alkaline fluoride-containing wastewater is pumped into the high-level water tank through a clean water pump, and the PAC enters the high-level water tank from the PAC storage bin through a metering pump for defluorination treatment. The treated alkaline wastewater flows into the full solid waste cementation filling system by gravity using a high head difference; The full solid waste bonding and filling system includes a blast furnace slag bin, a screw weighing machine, a screw conveyor, a second belt conveyor, a high-power mixing barrel and a filling industrial pump; the second belt conveyor is arranged between the buffer tank and the high-power mixing barrel, and is used to convey the phosphogypsum after alkali washing; the high-power mixing barrel is connected to the screw conveyor outlet, the second belt conveyor outlet, the high-level water tank pipeline outlet and the filling industrial pump inlet through pipelines; the blast furnace slag bin is connected to the screw weighing machine inlet, and the screw weighing machine outlet is connected to the screw conveyor inlet.

2. A method for filling solid waste with alkali-washed phosphogypsum pretreatment, characterized in that: The method uses the system as claimed in claim 1, and the method comprises the following steps: (1) transporting the high-fluorine phosphogypsum stored in the phosphogypsum storage yard to a sand washing and dehydration integrated machine through a first belt conveyor, and simultaneously introducing a certain concentration of NaOH solution into the sand washing and dehydration integrated machine to perform alkaline washing pretreatment on the high-fluorine phosphogypsum, and drying and dehydrating the phosphogypsum after multiple alkaline washings, and separating the dry phosphogypsum with a certain water content and the alkaline fluorine-containing waste liquid; (2) directly discharging the dried phosphogypsum in step (1) into a buffer tank for storage; (3) transporting the alkaline fluorine-containing wastewater in step (1) to a high-level water tank through a clean water pump to defluorinate the alkaline fluorine-containing wastewater; (4) During the filling operation, according to the filling ratio parameters and the underground filling strength requirements, the dry phosphogypsum stored in the buffer tank is transported to the strong stirring barrel by the second belt conveyor, the alkaline wastewater after the defluorination treatment in step (3) enters the strong stirring barrel by high head difference gravity, and the blast furnace slag powder in the blast furnace slag bin is weighed and measured according to a certain ratio by a screw weighing machine, and then transported to the strong stirring barrel by a screw conveyor; (5) The homogenized all-solid waste filling slurry is stirred in a high-powered stirring barrel, and then the homogenized all-solid waste filling slurry is pumped to the underground filling area through a filling industrial pump.

3. A method for filling solid waste with alkali-washed phosphogypsum pretreatment as claimed in claim 2, characterized in that: In step (1), the mass ratio of the dry weight of the high-fluorine phosphate gypsum to the NaOH solution is 1:2-3.

4. A method for filling solid waste with alkali-washed phosphogypsum pretreatment as claimed in claim 2, characterized in that: In step (1), the mass fraction of the NaOH solution is 1 wt%.

5. A method for filling solid waste with alkali-washed phosphogypsum pretreatment as claimed in claim 2, characterized in that: In step (1), the high-fluorine phosphate gypsum alkali washing time is not less than 10 minutes.

6. A method for filling solid waste with alkali-washed phosphogypsum pretreatment as claimed in claim 2, characterized in that: In step (1), the rotation speed of the sand washing and dehydration integrated machine during alkali washing is not less than 15 r / min.

7. A method for filling solid waste with alkali-washed phosphogypsum pretreatment as claimed in claim 2, characterized in that: In step (4), the mass ratio of the blast furnace slag powder to the dry phosphogypsum (dry weight) is 1:6-8.

8. The method for filling solid waste with alkali-washed phosphogypsum pretreatment according to claim 2, characterized in that: In step (5), the mass concentration of the homogeneous all-solid waste filling slurry is 64-68%.

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