Harmless treatment system for phosphogypsum

Abstract

The invention discloses a harmless treatment system for phosphogypsum, belonging to the technical field of phosphogypsum treatment. The system comprises: a thickener, used for concentrating phosphogypsum, the clear liquid is used as phosphogypsum return water, and the sludge is sent to a primary belt filter; the primary belt filter is used for filtering the sludge in sequence and washing it three times in total, collecting the three-wash drainage and sending it to the second washing area, collecting the second-wash drainage and sending it to the first washing area, collecting the first-wash drainage and sending it to the washing water treatment device, and collecting the filtrate as phosphogypsum return water; using the filter press filtrate and the secondary filter washing drainage as the third washing water; a re-slurry neutralization tank, used for mixing lime milk, dry gypsum, the secondary filter washing drainage and the filter press filtrate to obtain gypsum slurry; a secondary belt filter is used for filtering the gypsum slurry in sequence and washing it three times in total, and the output filtrate and washing water drainage are combined as the secondary filter washing drainage; the washing water treatment device is used for neutralizing and filtering the first-wash drainage output by the primary belt filter to obtain the filter press filtrate.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphogypsum treatment, and in particular relates to a harmless treatment system for phosphogypsum, which is mainly used for reducing acidity and phosphorus content. Background Art

[0002] Phosphogypsum is an industrial byproduct gypsum produced when producing high-concentration phosphate compound fertilizers. Its main component is calcium sulfate dihydrate (CaSO4·2H2O). The production of 1 ton of phosphoric acid (based on 100% P2O5) produces 4.8-5.0 tons of phosphogypsum. The solid waste pressure is very huge, so phosphogypsum needs to be treated in time. At present, domestic manufacturers generally use two methods for stacking phosphogypsum: wet-drain wet stacking and dry-drain dry stacking.

[0003] Wet discharge and wet pile: The phosphoric acid unit filter station adopts wet discharge. First, the phosphogypsum is slurried with water to make a phosphogypsum slurry with a water content of 70-80%. Then, according to the distance of transportation, one or more stages of pumps are used to send it to the phosphogypsum tailings pond. After natural sedimentation, the clean water is pumped to the phosphoric acid unit for reuse. This method is generally used in large-scale wet phosphoric acid units in China. This method has the advantages of high wastewater and phosphoric acid recovery rate, environmental protection and energy saving, convenient operation, and low operating costs.

[0004] Dry drainage and dry stacking: Dry drainage and dry stacking technology is the earliest storage method of phosphogypsum used in wet phosphoric acid production. The filtration station of the phosphoric acid unit adopts dry slag discharge, and the phosphogypsum with a water content of less than 20% is transported to the phosphogypsum warehouse by a belt conveyor, and then transported to the slag yard outside the factory by car or belt conveyor.

[0005] In the prior art, filter presses are used to process phosphogypsum, but the processing capacity is very limited. For the company's production of one million tons of phosphoric acid, a large number of filter presses and a large number of operators are required, which is basically impossible to achieve. In addition, filter press treatment alone can basically not reduce the total phosphorus content of phosphogypsum, resulting in a waste of phosphorus elements and not making good use of phosphogypsum. Phosphogypsum that is only dry-drained has a high phosphorus content, a very low pH value, and contains a large number of other impurities. Cement plants and building materials manufacturers do not accept it, which limits the utilization of phosphogypsum. Summary of the invention

[0006] In order to solve the above problems, the embodiment of the present invention provides a harmless treatment system for phosphogypsum, which uses a two-stage belt filter for treatment, so that the moisture content is ≤20%, the total phosphorus is ≤1%, and the pH value is 6-8; the wastewater generated in the process is utilized in different ways to improve the phosphorus yield, reduce wastewater discharge, and reduce water use. The technical solution is as follows:

[0007] The embodiment of the present invention provides a harmless treatment system for phosphogypsum, which includes: a thickener 1, which is used to concentrate the phosphogypsum from the phosphoric acid production system, and the clear liquid is sent to the phosphoric acid production system as phosphogypsum return water for reuse, and the sludge is sent to the filtration area 5 of the primary belt filter 2; the primary belt filter 2 is used to filter the sludge in sequence, wash it once, wash it twice and wash it three times, collect the three-wash drainage and send it to the second wash area 7 as the second wash water, collect the second wash drainage and send it to the first wash area 6 as the first wash water, collect the first wash drainage and send it to the wash water treatment device, collect the filtrate as the phosphogypsum return water and send it to the phosphoric acid production system for reuse; use the filter press filtrate output by the wash water treatment device and the secondary filter washing drainage output by the secondary belt filter 4 as the third wash water; a repulp neutralization tank 3 is used to separate the lime milk, the primary belt filter and the secondary filter washing drainage. The dry gypsum output by the filter 2, the secondary filtration and washing drainage output by the secondary belt filter 4 and the filter press filtrate output by the washing water treatment device are mixed to obtain gypsum slurry; the secondary belt filter 4 is used to filter, wash once, wash twice and wash three times the gypsum slurry in sequence, using clean water as the first washing water, the second washing water and the third washing water, and the output filtrate, the first washing drainage, the second washing drainage and the third washing drainage are combined as the secondary filtration and washing drainage and sent to the third washing area 8 of the primary belt filter 2 and the re-pulping neutralization tank 3; the washing water treatment device is used to neutralize the first washing drainage output by the primary belt filter 2 with lime milk and filter press to obtain the filter press filtrate, and the filter press filtrate is sent to the third washing area 8 of the primary belt filter 2 and the re-pulping neutralization tank 3; the hot water supply device is used to provide hot water and mix it with the washing water of the primary belt filter 2 and the secondary belt filter 4.

[0008] Specifically, the primary belt filter 2 and the secondary belt filter 4 in the embodiment of the present invention are divided into a filtration zone 5, a first washing zone 6, a second washing zone 7 and a third washing zone 8 in sequence along the conveying direction, and they all include a filtrate drain tank 9, a first washing drain tank 10, a second washing drain tank 11, a third washing drain tank 12 and a condensation vacuum structure; the liquid outlet of the filtration zone 5 is connected to the filtrate drain tank 9, the liquid outlet of the first washing zone 6 is connected to the first washing drain tank 10, and the drain of the second washing zone 7 is connected to the first washing drain tank 10. The outlet of the third washing zone 8 is connected to the second washing drain tank 11, the drain outlet of the third washing zone 8 is connected to the third washing drain tank 12, and the filtrate drain tank 9, the first washing drain tank 10, the second washing drain tank 11 and the third washing drain tank 12 are all connected to the condensation vacuum structure; for the first-stage belt filter 2, the first-stage belt filter 2 also includes a filtrate buffer tank 13, a first washing buffer tank 14, a second washing buffer tank 15 and a third washing buffer tank 16, the feed port of the filtration zone 5 is connected to the mud outlet of the thickener 1 The filtrate drain tank 9, the filtrate buffer tank 13 and the phosphoric acid production system are connected in sequence, the first wash drain tank 10, the first wash buffer tank 14 and the wash water treatment device are connected in sequence, the second wash drain tank 11, the second wash buffer tank 15 and the liquid inlet of the first wash zone 6 are connected in sequence, the third wash drain tank 12, the third wash buffer tank 16 and the liquid inlet of the second wash zone 7 are connected in sequence, the liquid inlet of the third wash zone 8 is connected to the secondary filtrate collecting tank 17 and the secondary belt filter 4 The washing water treatment device is connected; for the secondary belt filter 4, the secondary belt filter 4 also includes a secondary filtrate collecting tank 17, the feed port of the filtration zone 5 is connected to the repulping and neutralization tank 3, the discharge ports of the filtrate drain tank 9, the first wash drain tank 10, the second wash drain tank 11 and the third wash drain tank 12 are all connected to the secondary filtrate collecting tank 17, and the secondary filtrate collecting tank 17 is connected to the repulping and neutralization tank 3 and the liquid inlet of the third wash zone 8 of the primary belt filter 2.

[0009] Among them, the wash water treatment device in the embodiment of the present invention includes a neutralization reaction tank 18, a plate and frame filter press 19, a filtrate storage tank 20 and a re-slurry tank 21. The first wash buffer tank 14, the neutralization reaction tank 18, the plate and frame filter press 19 and the filtrate storage tank 20 are connected in sequence, and the filtrate storage tank 20 is connected to the liquid inlet of the third wash zone 8 of the primary belt filter 2 and the re-slurry neutralization tank 3. The re-slurry tank 21 is located directly below the plate and frame filter press 19 and is provided with an agitator therein.

[0010] Among them, the condensation vacuum structure in the embodiment of the present invention includes a condenser 22, a condensation separator 23, a vacuum pump 24, a vacuum pump exhaust separator 25, a condensation circulation tank, a cooling tower and a vacuum pump circulation tank, the exhaust ports of the filtrate drain tank 9, the first wash drain tank 10, the second wash drain tank 11 and the third wash drain tank 12 are all connected to the air inlet of the condenser 22, and the air outlet of the condenser 22, the condensation separator 23, the vacuum pump 24 and the vacuum pump exhaust separator 25 are connected in sequence; the drain port of the condenser 22 and the drain port of the condensation separator 23 are both connected to the condensation circulation tank, the condensation circulation tank is connected to the water inlet of the cooling tower and the filtrate storage tank 20, and the water outlet of the cooling tower is connected to the liquid inlet of the condensation separator 23; the circulating water inlet of the vacuum pump 24 is connected to the vacuum pump circulation tank, and the vacuum pump circulation tank is connected to the circulating water outlet of the vacuum pump 24 and the drain port of the vacuum pump exhaust separator 25.

[0011] Furthermore, the harmless treatment system provided in the embodiment of the present invention also includes a lime milk supply device, which includes a lime silo 26, a mixing tank 27, a dust collector 28 at the top of the lime silo 26, a vibrating hopper 29 at the bottom of the lime silo 26 and a metering screw conveyor 30 connected to the vibrating hopper 29; an agitator is provided in the mixing tank 27, whose feed port is connected to the discharge end of the metering screw conveyor 30, its liquid inlet is connected to the filtrate storage tank 20, and its liquid outlet is connected to the repulping neutralization tank 3 and the neutralization reaction tank 18.

[0012] Furthermore, the lower sides of the discharge ends of the primary belt filter 2 and the secondary belt filter 4 in the embodiment of the present invention are both provided with a filter cloth cleaning area 31 and are both also provided with a flushing water treatment device, a flushing water collecting tank 32 is provided directly below the filter cloth cleaning area 31, and the flushing water treatment device includes a flushing water sedimentation tank 33 and a filter cloth flushing tank 34; the liquid inlet of the flushing water sedimentation tank 33 is connected to the flushing water collecting tank 32, its clear liquid outlet is connected to the filter cloth flushing tank 34, and its sludge outlet is connected to the feed port of the filtration area 5; the filter cloth flushing tank 34 is connected to the liquid inlet of the filter cloth cleaning area 31.

[0013] Among them, the hot water supply device in the embodiment of the present invention includes a hot water tank 35 with a steam heating structure; the water inlet of the hot water tank 35 is connected to the condensate collection tank of the phosphate ammonium production system, and its water outlet is connected to the liquid inlet of the first washing zone 6 of the first belt filter 2, the liquid inlet of the second washing zone 7, the liquid inlet of the third washing zone 8 and the filter cloth washing tank 34, and its water outlet is also connected to the liquid inlet of the first washing zone 6 of the second washing zone 7, the liquid inlet of the third washing zone 8 and the filter cloth washing tank 34 of the second belt filter 4.

[0014] Specifically, the number of primary belt filters 2, repulp neutralization tanks 3 and secondary belt filters 4 in the embodiment of the present invention is equal and corresponds one to one, the wash water treatment device includes a plurality of plate and frame filter presses 19 arranged side by side, a plurality of primary belt filters 2 share one flushing water treatment device, and a plurality of secondary belt filters 4 share another flushing water treatment device.

[0015] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0016] (1) The parameters of the treated phosphogypsum are: moisture content ≤ 20%, total phosphorus ≤ 1%, and pH value 6-8;

[0017] (2) Large processing capacity: four first-stage belt filters (model HDJD-120) are used in conjunction with four second-stage belt filters (model HDJD-120), with a processing capacity of 5 million tons / year, requiring very few operators;

[0018] (3) The wastewater generated by the process is utilized in different ways to improve phosphorus recovery, reduce wastewater discharge, and reduce water use;

[0019] (4) Different treatment methods are used for the first, second and third wash drainage of the two-stage belt filter, which can reduce the use of water resources while ensuring the washing effect;

[0020] (5) Three water washes were performed during the primary filtration and three water washes were performed during the secondary filtration. The washing water was neutral or alkaline, which could wash out some phosphorus and other impurities, making it easier to process the phosphogypsum. Cement plants would accept it, expanding the utilization of phosphogypsum, which could be used as a building material and cement coagulant.

[0021] (6) Compared with conventional filter presses, belt filters have the advantages of high degree of automation (such as automatic slag discharge, automatic flushing, etc.).

[0022] (7) Lime can be used to settle phosphorus and other impurities in the washing water, and the washing liquid can be made alkaline to improve the washing effect;

[0023] (8) The filter press filtrate can be consumed in a variety of ways, including as third-wash water, as water for cooling towers, and for dissolving lime milk, etc., by adding hot water for water replenishment and heating. The washing effect of hot water using the condensed water (cleaner, weakly alkaline, and high temperature) during the concentration of ammonium phosphate is better;

[0024] (9) Both the third wash water and the repulp water are made of filter press filtrate and secondary filter wash drainage, which can be balanced as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1It is a principle block diagram of a harmless treatment system for phosphogypsum provided in an embodiment of the present invention;

[0026] Figure 2 is a principle block diagram of a vacuum condensation system provided by an embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the structure of the thickener;

[0028] Figure 4 It is a structural diagram of a first-stage belt filter;

[0029] Figure 5 It is a structural schematic diagram of a combination of a two-stage belt filter and a reslurry neutralization tank;

[0030] Figure 6 It is a structural schematic diagram of a combination of a neutralization reaction tank, a plate and frame filter press, a filtrate storage tank and a reslurry tank;

[0031] Figure 7 It is a schematic diagram of the structure of the vacuum condensation system;

[0032] Figure 8 It is a schematic diagram of the structure of the combination of the flushing water settling tank and the filter cloth flushing tank;

[0033] Fig. 9 It is a schematic diagram of the structure of a lime milk supply device;

[0034] Fig.10 It is a structural diagram of a hot water supply device.

[0035] In the figure: 1 thickener, 2 primary belt filter, 3 repulping and neutralization tank, 4 secondary belt filter, 5 filtering area, 6 primary washing area, 7 secondary washing area, 8 tertiary washing area, 9 filtrate drainage tank, 10 primary washing drainage tank, 11 secondary washing drainage tank, 12 tertiary washing drainage tank, 13 filtrate buffer tank, 14 primary washing buffer tank, 15 secondary washing buffer tank, 16 tertiary washing buffer tank, 17 secondary filtrate collecting tank, 18 neutralization reaction tank, 19 plate and frame filter press, 20 filtrate storage tank, 21 repulping tank, 22 condenser, 23 condensation separator, 24 vacuum pump, 25 vacuum pump exhaust separator, 26 lime silo, 27 mixing tank, 28 dust collector, 29 vibrating hopper, 30 metering screw conveyor, 31 filter cloth washing area, 32 flushing water collecting tank, 33 flushing water sedimentation tank, 34 filter cloth flushing tank, 35 hot water tank, 36 overflow tank. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Embodiment 1

[0038] See also Figure 1-10The embodiment of the present invention provides a harmless treatment system for phosphogypsum, the system comprising:

[0039] The thickener 1 is used to concentrate the phosphogypsum from the phosphoric acid production system. The clear liquid is sent to the phosphoric acid production system as phosphogypsum return water for reuse, and the sludge is sent to the filtration area 5 of the primary belt filter 2.

[0040] The primary belt filter 2 is used to filter, wash once, wash twice and wash three times the sludge output from the thickener 1 in sequence, collect the tertiary wash drainage and send it to the secondary wash area 7 as the secondary wash water, collect the secondary wash drainage and send it to the primary wash area 6 as the primary wash water, collect the primary wash drainage and send it to the wash water treatment device (specifically the neutralization reaction tank 18), collect the filtrate as phosphogypsum return water and send it to the phosphoric acid production system for reuse; the filter press filtrate output from the wash water treatment device (specifically the filter press storage tank 20) ​​and the secondary filter wash drainage output from the secondary belt filter 4 are used as the tertiary wash water.

[0041] The re-slurry neutralization tank 3 is used to mix the lime milk, the dry gypsum output from the primary belt filter 2 (through the conveyor belt), the secondary filtration and washing drainage output from the secondary belt filter 4 and the filter press filtrate output from the washing water treatment device to obtain gypsum slurry.

[0042] The secondary belt filter 4 is used to filter, wash once, wash twice and wash tertiary the gypsum slurry in sequence, using clean water as the first wash water, the second wash water and the third wash water. The output filtrate, the first wash drainage, the second wash drainage and the third wash drainage are combined as the secondary filtration drainage and sent to the third wash area 8 of the primary belt filter 2 and the re-slurry neutralization tank 3.

[0043] The washing water treatment device is used to neutralize the first washing wastewater output by the first-stage belt filter 2 with lime milk and filter press to obtain the filter press filtrate, and the filter press filtrate is sent to the third washing area 8 of the first-stage belt filter 2 and the re-slurry neutralization tank 3.

[0044] The hot water supply device is used to provide hot water and mix it with the wash water (first wash water, second wash water and third wash water) of the primary belt filter 2 and the secondary belt filter 4 and the flushing drainage to heat it (to above 50°C).

[0045] The lime milk supply device is used to mix the raw gypsum with the filter press filtrate to obtain lime milk and send it to the repulping neutralization tank 3 and the wash water treatment device (specifically the neutralization reaction tank 18).

[0046] The flushing water treatment device is used to collect and settle the flushing drainage output by the filter cloth cleaning area 31. The clear liquid is sent to the filter cloth cleaning area 31 as flushing water, and the mud is sent to the feed port of the filter area 5 of the corresponding belt filter (the primary belt filter 2 or the secondary belt filter 4).

[0047] Embodiment 2

[0048] See also Figure 1-10 The embodiment of the present invention provides a harmless treatment system for phosphogypsum, which includes a thickener 1, a primary belt filter 2, a repulping and neutralization tank 3, a secondary belt filter 4, a wash water treatment device, a hot water supply device, etc.

[0049] Among them, see Figure 3 The clear liquid of the thickener 1 in the embodiment of the present invention overflows to the overflow tank 36 and is then sent to the phosphoric acid production system.

[0050] Specifically, see Figure 4-5 The primary belt filter 2 and the secondary belt filter 4 in the embodiment of the present invention are divided into a filter area 5, a first wash area 6, a second wash area 7 and a third wash area 8 in the conveying direction, and they all include a filtrate drain tank 9, a first wash drain tank 10, a second wash drain tank 11, a third wash drain tank 12 and a condensation vacuum structure. The settings of the filter area 5, the first wash area 6, the second wash area 7 and the third wash area 8 can refer to the description of the application number CN201821856319.4. The first wash area 6, the second wash area 7 and the third wash area 8 can realize the water washing of the material on the filter belt, and the detailed description is omitted in this embodiment. The liquid outlet of the filter area 5 is connected to the filtrate drain tank 9 through a pipeline, the liquid outlet of the first wash area 6 is connected to the first wash drain tank 10 through a pipeline, the drain port of the second wash area 7 is connected to the second wash drain tank 11 through a pipeline, and the drain port of the third wash area 8 is connected to the third wash drain tank 12 through a pipeline. The filtrate drain tank 9, the first wash drain tank 10, the second wash drain tank 11 and the third wash drain tank 12 are used to achieve gas-liquid separation. The filtrate drain tank 9, the first wash drain tank 10, the second wash drain tank 11 and the third wash drain tank 12 are all connected to the condensation vacuum structure through pipelines for vacuuming.

[0051] See also Figure 4 For the primary belt filter 2, the primary belt filter 2 also includes a filtrate buffer tank 13, a first wash buffer tank 14, a second wash buffer tank 15 and a third wash buffer tank 16. The filtrate buffer tank 13, the first wash buffer tank 14, the second wash buffer tank 15 and the third wash buffer tank 16 are used to store filtrate, first wash drainage, second wash drainage and third wash drainage respectively. The feed port of the filtration zone 5 is connected to the mud outlet of the thickener 1 through a pipeline, the filtrate drainage tank 9, the filtrate buffer tank 13 and the phosphoric acid production system are connected in sequence through pipelines to output phosphogypsum return water, the first wash drainage tank 10, the first wash buffer tank 14 and the wash water treatment device are connected in sequence through pipelines to output the first wash drainage, the second wash drainage tank 11, the second wash buffer tank 15 and the liquid inlet of the first wash zone 6 are connected in sequence through pipelines to use the second wash drainage as the first wash water, the third wash drainage tank 12, the third wash buffer tank 16 and the liquid inlet of the second wash zone 7 are connected in sequence through pipelines to use the third wash drainage as the second wash water, and the liquid inlet of the third wash zone 8 is connected to the secondary filtrate collecting tank 17 of the secondary belt filter 4 and the wash water treatment device through a pipeline to use the filter press filtrate and the secondary filtration and washing drainage as the third wash water.

[0052] See also Figure 5 For the secondary belt filter 4, the secondary belt filter 4 further includes a secondary filtrate collecting tank 17, which is used to mix and store filtrate, first wash drainage, second wash drainage and third wash drainage. The feed port of the filtration zone 5 is connected to the re-slurry neutralization tank 3 through a pipeline, and the drainage ports of the filtrate drainage tank 9, the first wash drainage tank 10, the second wash drainage tank 11 and the third wash drainage tank 12 are all connected to the secondary filtrate collecting tank 17 through a pipeline. The secondary filtrate collecting tank 17 is connected to the re-slurry neutralization tank 3 and the inlet of the third wash zone 8 of the primary belt filter 2 through a pipeline with a valve to output the secondary filtration and washing drainage as the third wash water and for the re-slurry of lime milk.

[0053] Among them, see Figure 6 The washing water treatment device in the embodiment of the present invention includes a neutralization reaction tank 18, a plate-frame filter press 19, a filter press storage tank 20, and a re-pulping tank 21, etc. The first washing buffer tank 14, the neutralization reaction tank 18, the plate-frame filter press 19, and the filter press storage tank 20 are connected in sequence through pipelines. Lime milk is added to the neutralization reaction tank 18. The filter press storage tank 20 is connected to the liquid inlet of the third washing zone 8 of the primary belt filter 2 and the re-pulping neutralization tank 3 through a pipeline with a valve. The re-pulping tank 21 is located directly below the plate-frame filter press 19 and is provided with an agitator. The liquid inlet of the re-pulping tank 21 is connected to the process water storage tank (used to collect process water, including rainwater, clean wastewater, etc.) through a pipeline. The density of the mud in the re-pulping tank 7 is controlled within 1.5g / mL and sent out (as unprocessable phosphogypsum for landfill or damming, etc.).

[0054] Among them, see Figure 7 The condensation vacuum structure in the embodiment of the present invention includes a condenser 22, a condensation separator 23, a vacuum pump 24, a vacuum pump exhaust separator 25, a condensation circulation tank, a cooling tower and a vacuum pump circulation tank, etc. The exhaust ports of the filtrate drain tank 9, the first wash drain tank 10, the second wash drain tank 11 and the third wash drain tank 12 are all connected to the air inlet of the condenser 22 through pipelines, and the air outlet of the condenser 22, the condensation separator 23, the vacuum pump 24 and the vacuum pump exhaust separator 25 are sequentially connected through pipelines to evacuate. The drain port of the condenser 22 and the drain port of the condensation separator 23 are both connected to the condensation circulation tank through pipelines, and the condensation circulation tank is connected to the water inlet of the cooling tower and the filtrate storage tank 20 (for replenishing cooling water) through pipelines. The water outlet of the cooling tower is connected to the liquid inlet of the condensation separator 23. The above structure forms a cooling water cycle, and the filtrate of the filtrate is used as replenishing water. The circulating water inlet of the vacuum pump 24 is connected to the vacuum pump circulation tank through a pipeline, and the vacuum pump circulation tank is connected to the circulating water outlet of the vacuum pump 24 and the discharge port of the vacuum pump exhaust separator 25 through a pipeline. The above structure forms a vacuum pump water circulation, and the water separated by the vacuum pump exhaust separator 25 is used as makeup water.

[0055] Further, see Fig. 9 The harmless treatment system provided in the embodiment of the present invention further includes a lime milk supply device, which includes a lime silo 26, a mixing tank 27, a dust collector 28 (for dust removal, specifically a bag dust collector) at the top of the lime silo 26, a vibrating hopper 29 at the bottom of the lime silo 26, and a metering screw conveyor 30 connected to the vibrating hopper 29. A stirrer is provided in the mixing tank 27, the feed port of which is connected to the discharge end of the metering screw conveyor 30, the liquid inlet of which is connected to the filtrate storage tank 20 through a pipeline, and the liquid outlet of which is connected to the repulping neutralization tank 3 and the neutralization reaction tank 18 through a pipeline to output the lime milk.

[0056] Further, see Figure 4-5 8, the lower side of the discharge end of the primary belt filter 2 and the secondary belt filter 4 in the embodiment of the present invention is provided with a filter cloth cleaning area 31 (spraying upward to clean the filter belt) and a flushing water treatment device is also provided. A flushing water collecting tank 32 is provided directly below the filter cloth cleaning area 31 for collecting flushing drainage. The flushing water treatment device includes a flushing water settling tank 33 and a filter cloth flushing tank 34, etc.; the liquid inlet of the flushing water settling tank 33 is connected to the flushing water collecting tank 32 through a pipeline, the clear liquid outlet thereof is connected to the filter cloth flushing tank 34 through a pipeline, and the sludge outlet thereof is connected to the feed port of the filter area 5 through a pipeline. The filter cloth flushing tank 34 is connected to the liquid inlet of the filter cloth cleaning area 31 through a pipeline.

[0057] Among them, see Fig.10 The hot water supply device in the embodiment of the present invention includes a hot water tank 35 with a steam heating structure. The water inlet of the hot water tank 35 is connected to the condensate collection tank (collecting the condensate of the multi-effect concentrator, the temperature is greater than 70°C, weakly alkaline) of the phosphate ammonium production system through a pipeline, and its water outlet is connected to the liquid inlet of the first washing zone 6 of the first belt filter 2, the liquid inlet of the second washing zone 7, the liquid inlet of the third washing zone 8 and the filter cloth washing tank 34 through a pipeline with a valve, and its water outlet is also connected to the liquid inlet of the first washing zone 6 of the second washing zone 7, the liquid inlet of the third washing zone 8 and the filter cloth washing tank 34 of the second belt filter 4 through a pipeline with a valve.

[0058] Specifically, the number of primary belt filters 2, repulp neutralization tanks 3 and secondary belt filters 4 in the embodiment of the present invention is equal (specifically four) and corresponds one to one, the wash water treatment device includes a plurality (specifically four) of plate and frame filter presses 19 arranged side by side, a plurality of primary belt filters 2 share one flushing water treatment device, and a plurality of secondary belt filters 4 share another flushing water treatment device.

[0059] Among them, pumps, flow meters, valves, etc. are arranged on the pipelines between the structures in this embodiment as needed.

[0060] Example 3

[0061] Example 3 discloses a method for harmless treatment of phosphogypsum, the method comprising:

[0062] See also Figure 1 Embodiment 1 provides a comprehensive treatment method for phosphogypsum, the method comprising:

[0063] (1) The thickener 1 collects the phosphogypsum and thickens it through the thickener. The clear liquid obtained by the thickening is used as the phosphogypsum return water, and the thickened slurry is sent to the primary belt filter 2 for treatment.

[0064] (2) The primary belt filter 2 filters the slurry obtained in step (1), and the filtrate is used as phosphogypsum return water, and the filter residue is sent to step (3) for treatment.

[0065] (3) In the re-pulping and neutralization tank 3, the filter residue obtained in step (2), the re-pulping water and quicklime or lime milk are re-pulped to obtain phosphogypsum slurry, and the re-pulping water includes the filter press filtrate and the secondary filter washing drainage.

[0066] (4) The secondary belt filter 4 filters the phosphogypsum slurry obtained in step (3), and the filtrate, the first wash drainage, the second wash drainage and the third wash drainage of the secondary belt filter 4 are combined as the secondary filter drainage, and the filter residue is dry gypsum.

[0067] In steps (2) and (4), after filtration, the first wash, second wash and third wash are performed in sequence through the first wash water, the second wash water and the third wash water respectively; in step (2), the first wash drainage of the primary belt filter 2 is collected, and the filter press filtrate is obtained after gas-liquid separation, lime milk neutralization and filter pressing; the second wash drainage is collected and used as the first wash water after gas-liquid separation; the third wash drainage is collected and used as the second wash water after gas-liquid separation; the third wash water includes the filter press filtrate and the secondary filter wash drainage. In step (4), in order to ensure the cleaning effect, clean water is used as the first wash water, the second wash water and the third wash water.

[0068] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A harmless treatment system for phosphogypsum, characterized in that: include: A thickener (1) is used to concentrate the phosphogypsum from the phosphoric acid production system, the clear liquid is sent to the phosphoric acid production system as phosphogypsum return water for reuse, and the sludge is sent to the filtration area (5) of the primary belt filter (2); The primary belt filter (2) is used to filter, wash once, wash twice and wash three times the sludge in sequence, collect the drainage from the three washes and send it to the second wash area (7) as the second wash water, collect the drainage from the second wash and send it to the first wash area (6) as the first wash water, collect the drainage from the first wash and send it to the wash water treatment device, collect the filtrate as phosphogypsum return water and send it to the phosphoric acid production system for reuse; use the filter press filtrate output from the wash water treatment device and the secondary filter washing drainage output from the secondary belt filter (4) as the tertiary wash water; The re-slurry neutralization tank (3) is used to mix the lime milk, the dry gypsum output from the primary belt filter (2), the secondary filtration and washing drainage output from the secondary belt filter (4) and the filter press filtrate output from the washing water treatment device to obtain gypsum slurry; The secondary belt filter (4) is used to filter, wash once, wash twice and wash three times the gypsum slurry in sequence, using clean water as the first wash water, the second wash water and the third wash water, and the output filtrate, the first wash drainage, the second wash drainage and the third wash drainage are combined as the secondary filtration drainage and sent to the third wash area (8) of the primary belt filter (2) and the re-slurry neutralization tank (3); A washing water treatment device is used for neutralizing the first washing wastewater outputted from the first-stage belt filter (2) with lime milk and filtering to obtain a filter press filtrate, and the filter press filtrate is sent to the third washing area (8) of the first-stage belt filter (2) and the reslurry neutralization tank (3); A hot water supply device, used for providing hot water and mixing it with the wash water of the primary belt filter (2) and the secondary belt filter (4); The primary belt filter (2) and the secondary belt filter (4) are both sequentially divided into a filtration zone (5), a first wash zone (6), a second wash zone (7) and a third wash zone (8) along the conveying direction, and both comprise a filtrate drainage tank (9), a first wash drainage tank (10), a second wash drainage tank (11), a third wash drainage tank (12) and a condensation vacuum structure; the liquid outlet of the filtration zone (5) is connected to the filtrate drainage tank (9), the liquid outlet of the first wash zone (6) is connected to the first wash drainage tank (10), the drainage port of the second wash zone (7) is connected to the second wash drainage tank (11), the drainage port of the third wash zone (8) is connected to the third wash drainage tank (12), and the filtrate drainage tank (9), the first wash drainage tank (10), the second wash drainage tank (11) and the third wash drainage tank (12) are all connected to the condensation vacuum structure; For a primary belt filter (2), the primary belt filter (2) further comprises a filtrate buffer tank (13), a first wash buffer tank (14), a second wash buffer tank (15) and a third wash buffer tank (16); the feed port of the filtration zone (5) is connected to the slurry outlet of the thickener (1); the filtrate drainage tank (9), the filtrate buffer tank (13) and the phosphoric acid production system are connected in sequence; the first wash drainage tank (10), the first wash buffer tank (14) and the wash water treatment device are connected in sequence; the second wash drainage tank (11), the second wash buffer tank (15) and the liquid inlet of the primary wash zone (6) are connected in sequence; the third wash drainage tank (12), the third wash buffer tank (16) and the liquid inlet of the second wash zone (7) are connected in sequence; and the liquid inlet of the third wash zone (8) is connected to the secondary filtrate collecting tank (17) of the secondary belt filter (4) and the wash water treatment device; For the two-stage belt filter (4), the two-stage belt filter (4) further comprises a two-stage filtrate collecting tank (17), the feed port of the filtration zone (5) is connected to the repulping and neutralization tank (3), the discharge ports of the filtrate drainage tank (9), the first wash drainage tank (10), the second wash drainage tank (11) and the third wash drainage tank (12) are all connected to the two-stage filtrate collecting tank (17), and the two-stage filtrate collecting tank (17) is connected to the repulping and neutralization tank (3) and the liquid inlet of the third wash zone (8) of the one-stage belt filter (2); The wash water treatment device comprises a neutralization reaction tank (18), a plate-frame filter press (19), a filter press storage tank (20) and a re-slurry tank (21); the first wash buffer tank (14), the neutralization reaction tank (18), the plate-frame filter press (19) and the filter press storage tank (20) are connected in sequence; the filter press storage tank (20) is connected to the liquid inlet of the third wash zone (8) of the primary belt filter (2) and the re-slurry neutralization tank (3); the re-slurry tank (21) is located directly below the plate-frame filter press (19) and is provided with a stirrer; The condensation vacuum structure comprises a condenser (22), a condensation separator (23), a vacuum pump (24), a vacuum pump exhaust separator (25), a condensation circulation tank, a cooling tower and a vacuum pump circulation tank. The exhaust ports of the filtrate drainage tank (9), the first wash drainage tank (10), the second wash drainage tank (11) and the third wash drainage tank (12) are all connected to the air inlet of the condenser (22). The air outlet of the condenser (22), the condensation separator (23), the vacuum pump (24) and the vacuum pump exhaust separator are connected to the air inlet of the condenser (22). (25) are connected in sequence; the discharge port of the condenser (22) and the discharge port of the condensation separator (23) are both connected to the condensation circulation tank, the condensation circulation tank is connected to the water inlet of the cooling tower and the filtrate storage tank (20), and the water outlet of the cooling tower is connected to the liquid inlet of the condensation separator (23); the circulating water inlet of the vacuum pump (24) is connected to the vacuum pump circulation tank, and the vacuum pump circulation tank is connected to the circulating water outlet of the vacuum pump (24) and the discharge port of the vacuum pump exhaust separator (25); The lower sides of the discharge ends of the primary belt filter (2) and the secondary belt filter (4) are both provided with a filter cloth cleaning area (31) and a flushing water treatment device. A flushing water collecting tank (32) is provided directly below the filter cloth cleaning area (31). The flushing water treatment device comprises a flushing water settling tank (33) and a filter cloth flushing tank (34). The liquid inlet of the flushing water settling tank (33) is connected to the flushing water collecting tank (32), the clear liquid outlet thereof is connected to the filter cloth flushing tank (34), and the sludge outlet thereof is connected to the feed inlet of the filter area (5). The filter cloth flushing tank (34) is connected to the liquid inlet of the filter cloth cleaning area (31). The hot water supply device comprises a hot water tank (35) with a steam heating structure; the water inlet of the hot water tank (35) is connected to the condensate collection tank of the phosphate ammonium production system, and the water outlet is connected to the liquid inlet of the first washing zone (6), the liquid inlet of the second washing zone (7), the liquid inlet of the third washing zone (8) and the filter cloth washing tank (34) of the first belt filter (2); the water outlet is also connected to the liquid inlet of the first washing zone (6), the liquid inlet of the second washing zone (7), the liquid inlet of the third washing zone (8) and the filter cloth washing tank (34) of the second belt filter (4).

2. The harmless treatment system for phosphogypsum according to claim 1, characterized in that: The harmless treatment system also includes a lime milk supply device, which includes a lime silo (26), a mixing tank (27), a dust collector (28) at the top of the lime silo (26), a vibrating hopper (29) at the bottom of the lime silo (26), and a metering screw conveyor (30) connected to the vibrating hopper (29); a stirrer is provided in the mixing tank (27), a feed port of which is connected to the discharge end of the metering screw conveyor (30), a liquid inlet of which is connected to the filtrate storage tank (20), and a liquid outlet of which is connected to the repulping neutralization tank (3) and the neutralization reaction tank (18).

3. The harmless treatment system for phosphogypsum according to claim 1, characterized in that: The number of the primary belt filter (2), the repulping and neutralization tank (3) and the secondary belt filter (4) is equal and one-to-one corresponding, the wash water treatment device comprises a plurality of plate and frame filter presses (19) arranged side by side, the plurality of primary belt filters (2) share one wash water treatment device, and the plurality of secondary belt filters (4) share another wash water treatment device.

Images