Three-state salt elimination method for saline-alkali land paddy field irrigation salt leaching tail water

Abstract

The invention discloses a three-state salt discharging method for irrigation salt-leaching tail water of a saline-alkali land paddy field, and relates to the technical field of irrigation salt-leaching tail water treatment.The method comprises the steps that the tail water discharged through irrigation salt-leaching is discharged into a primary freezing pond, the tail water is frozen into a solid ice layer, and primary bottom-pumping concentrated salt-soluble water is pumped into a secondary freezing pond; the primary bottom-pumping concentrated salt-soluble water in the secondary freezing pool is secondarily frozen into an ice layer at natural low temperature, and the secondary bottom-pumping concentrated salt-soluble water is pumped into a rainproof heating storage pool; the secondary bottom-pumping concentrated salt solution in the rainproof heating storage pool is heated; and pumping the secondary bottom-pumping concentrated salt-soluble water in the rainproof heating storage pool into a solar evaporation pool for evaporation, crystallizing the secondary bottom-pumping concentrated salt-soluble water into solid salt, and completing the salt discharging process of discharging tail water from irrigation salt leaching of the saline-alkali soil paddy field. Solid salt serves as a chemical raw material, water obtained after ice in the primary freezing pond and the secondary freezing pond is melted serves as irrigation water of the saline-alkali soil in the next year, and the utilization rate of tail water discharged during irrigation and salt leaching is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of irrigation and salt washing tail water treatment, in particular to a three-state salt discharge method for salt and alkali field paddy irrigation and salt washing tail water. BACKGROUND

[0002] The average annual temperature in Songyuan and Baicheng regions in the west of Jilin Province is 4.5 DEG C, the annual precipitation is 400-500 mm, and the number of days in the winter freezing period is 129-168 days, which belongs to a high-latitude cold region. The salt and alkali field in the region belongs to soda salinization soil, and the salt in the soil is mainly Na2HCO3 (sodium carbonate) and NaHCO3 (sodium bicarbonate).

[0003] At present, the most commonly used method for the improvement and treatment of the salt and alkali field paddy is the irrigation water washing salt and alkali compression method, but the salt content in the tail water discharged by the irrigation and salt washing is over standard, and the tail water cannot be used for irrigation again, resulting in waste of water resources. In view of this problem, a three-state salt discharge technical method for the salt and alkali field paddy irrigation and salt washing tail water is proposed in combination with the natural conditions of the long winter freezing period and the 1.5 m deep frozen layer and the principle that water and solute salt do not co-crystallize when freezing. SUMMARY

[0004] The present application solves the technical problem of overcoming the above-mentioned shortcomings of the prior art, and provides a three-state salt discharge method for the salt and alkali field paddy irrigation and salt washing tail water, which improves the utilization rate of the tail water discharged by the irrigation and salt washing.

[0005] The technical scheme adopted to solve the above-mentioned technical problem is as follows: a three-state salt discharge method for the salt and alkali field paddy irrigation and salt washing tail water, comprising the following steps: S1, after the irrigation of the salt and alkali field paddy is completed, the tail water discharged by the irrigation and salt washing is discharged into a primary freezing pool, the tail water is frozen into a solid ice layer, the salt solution in the water body flows back in the freezing process, seeps back below the solid ice layer to form primary bottom pumping concentrated salt solution water, and the primary bottom pumping concentrated salt solution water is pumped into a secondary freezing pool; S2, the primary bottom pumping concentrated salt solution water in the secondary freezing pool is secondary frozen into an ice layer at a natural low temperature, the salt solution in the water body flows back again in the secondary freezing process, seeps back below the ice layer to form secondary bottom pumping concentrated salt solution water, and the secondary bottom pumping concentrated salt solution water is pumped into a rainproof temperature rising storage pool; S3, the secondary bottom pumping concentrated salt solution water in the rainproof temperature rising storage pool is subjected to temperature rising; S4, the secondary bottom pumping concentrated salt solution water in the rainproof temperature rising storage pool is pumped into a solar evaporation pool for evaporation, the secondary bottom pumping concentrated salt solution water is crystallized into solid salt, the solid salt is used as a chemical raw material, the solid ice layer of the primary freezing pool and the ice layer in the secondary freezing pool melt to form water as next year's irrigation water for the salt and alkali field, and the salt discharge process of the tail water discharged by the irrigation and salt washing of the salt and alkali field paddy is completed.

[0006] Further, the solid ice layer thickness of the tail water in S1 is 1.2m-1.5m, the frozen ice layer thickness of the first bottom-extracted concentrated salt-dissolved water in S2 is 1.2m-1.5m, and the volume of the second bottom-extracted concentrated salt-dissolved water in the rain-proof warming storage pool in S3 is 7% of the volume of the tail water discharged from the salt washing.

[0007] Further, the first bottom-extracted concentrated salt-dissolved water in S1 is pumped into the second freezing pool by a first water pump, the second bottom-extracted concentrated salt-dissolved water in S2 is pumped into the rain-proof warming storage pool by a second water pump, and the second bottom-extracted concentrated salt-dissolved water in the rain-proof warming storage pool in S4 is pumped into the solar evaporation pool by a third water pump for evaporation.

[0008] Further, the first freezing pool is a trapezoidal pool, and the slope of the pool bottom is 1:192; the second freezing pool is also a trapezoidal pool, and two slopes are symmetrically arranged on the pool bottom with the central vertical line as the symmetry line, and the slopes on both sides are 1:40.

[0009] Further, the rain-proof warming storage pool is a trapezoidal pool, and a rain-proof shed arch is arranged on the top of the rain-proof warming storage pool, the rain-proof shed arch comprises double-layer arched pipes, first supporting steel bars, first connecting pipes and first light-transmitting shed films, a plurality of double-layer arched pipes are arranged on the top of the rain-proof warming storage pool, the first supporting steel bars are arranged between the double-layer arched pipes, the first connecting pipes are connected between the double-layer arched pipes, and the first light-transmitting shed films are arranged outside the double-layer arched pipes.

[0010] Further, the rain-proof warming storage pool is a trapezoidal pool, and a rain-proof shed arch is arranged on the top of the rain-proof warming storage pool, the rain-proof shed arch comprises double-layer arched pipes, first supporting steel bars, first connecting pipes and first light-transmitting shed films, a plurality of double-layer arched pipes are arranged on the top of the rain-proof warming storage pool, the first supporting steel bars are arranged between the double-layer arched pipes, the first connecting pipes are connected between the double-layer arched pipes, and the first light-transmitting shed films are arranged outside the double-layer arched pipes.

[0011] Further, the rain-proof warming storage pool is a trapezoidal pool, and a rain-proof shed arch is arranged on the top of the rain-proof warming storage pool, the rain-proof shed arch comprises double-layer arched pipes, first supporting steel bars, first connecting pipes and first light-transmitting shed films, a plurality of double-layer arched pipes are arranged on the top of the rain-proof warming storage pool, the first supporting steel bars are arranged between the double-layer arched pipes, the first connecting pipes are connected between the double-layer arched pipes, and the first light-transmitting shed films are arranged outside the double-layer arched pipes.

[0012] Furthermore, the thickness of the impermeable and frost-resistant reinforced concrete layer is 15cm, the thickness of the polyurethane foam insulation layer is 10cm, the thickness of the impermeable reinforced concrete layer is 15cm, the thickness of the ceramic waterproof material layer is 0.5cm, and the thickness of the waterproof mortar layer is 5cm.

[0013] Furthermore, the solar evaporation pool is symmetrically arranged with the vertical line at the bottom of the pool as the line of symmetry. The slopes on both sides are 1:13 respectively. Stainless steel finned tube supports are arranged in an array on both sides of the slope. Each stainless steel finned tube support is equipped with a sloped finned tube evaporator for heating the concentrated salt solution in the secondary bottom pumping in the solar evaporation pool.

[0014] Furthermore, a solar flat plate collector is installed on the top of the solar evaporation pool.

[0015] The beneficial effects of the present invention are as follows: (1) The present invention adopts the method of discharging the tailwater discharged from irrigation and salt washing into a primary freezing pool, freezing the tailwater into a solid ice layer, pumping the concentrated salt solution from the primary bottom pumping to a secondary freezing pool, where the concentrated salt solution from the primary bottom pumping is frozen into an ice layer at a natural low temperature, pumping the concentrated salt solution from the secondary bottom pumping to a rainproof and heated storage pool, heating the concentrated salt solution from the secondary bottom pumping in the rainproof and heated storage pool, and pumping the concentrated salt solution from the secondary bottom pumping in the rainproof and heated storage pool into a solar evaporation pool. Evaporation is carried out to crystallize the concentrated salt solution from the secondary bottom pumping into solid salt, completing the salt removal process of the leaching water from irrigation of saline-alkali paddy fields. The solid salt is used as a chemical raw material. The solid ice layer in the primary freezing pool and the water formed after the ice layer in the secondary freezing pool melts as the temperature rises are used as irrigation water for saline-alkali land in the following year. This invention realizes the salt removal treatment of large-volume leaching water from saline-alkali land, improving the utilization rate of irrigation leaching water. This invention is applicable to high-latitude cold regions with low-temperature natural conditions where the number of freezing days is 129 days to 168 days.

[0016] (2) In this invention, a rainproof arch is installed on the top of the rainproof and heated storage tank. The rainproof arch is used to prevent the intrusion of natural precipitation.

[0017] (3) In this invention, the slope-type finned tube evaporator at the bottom of the solar evaporation pool heats the concentrated salt solution in the solar evaporation pool after secondary extraction, and the solar flat plate collector at the top of the solar evaporation pool heats the concentrated salt solution after secondary extraction to raise the temperature, crystallizes the concentrated salt solution after secondary extraction into solid salt, and uses the solid salt as a chemical raw material. The water formed after the concentrated salt solution after secondary extraction is evaporated is used as irrigation water for saline-alkali land in the following year. The salt content of the water after freezing and melting is 600-1800 mg / L.

[0018] (4) In this invention, the inclined side of the condensation shed at the top of the solar evaporation pool is set at a 73° angle with the horizontal plane, which is conducive to the water generated by the secondary bottom-concentrated salt solution during the evaporation process condensing on the condensation shed, and the water in the second light-transmitting membrane slides down to the guide water trough at the top of the solar evaporation pool and flows out.

[0019] (5) In this invention, the solid ice layer in the primary freezing pool and the water formed after the ice layer in the secondary freezing pool melts as the temperature rises are used as irrigation water for saline-alkali land in the following year. The salt content of the irrigation water is 600-1800 mg / L, which improves the utilization rate of irrigation salt washing tailwater. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an embodiment of the three-state salt removal method for irrigation tailwater in saline-alkali paddy fields according to the present invention.

[0021] Figure 2 This is a structural diagram of the rainproof and heated storage tank and the rainproof canopy arch.

[0022] Figure 3 This is a structural diagram of the solar evaporation tank and the condensate shed.

[0023] Figure 4 This is a structural diagram of a condensate shed.

[0024] Figure 5 yes Figure 1 A magnified schematic diagram of the structure at point A in the middle.

[0025] Attached reference numerals: 1. Primary freezing tank; 2. First water pump; 3. Secondary freezing tank; 4. Second water pump; 5. Rainproof and heated storage tank; 6. Rainproof canopy arch; 601. Double-layer arched round pipe; 602. First supporting steel bar; 603. First connecting pipe; 7. Third water pump; 8. Solar evaporation tank; 9. Condensation canopy; 901. Non-powered fan; 902. Double-layer steel pipe; 903. Second supporting steel bar; 904. Guide water channel; 905. Base plate frame; 906. Second connecting pipe; 10. Circulation pump; 11. Sloping finned tube evaporator; 12. Solar flat plate collector; 13. Composite reinforced concrete insulated structure wall; 14. Stainless steel finned tube support; 15. Thermal oil storage tank; 16. Filter; 17. Stainless steel pipe. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] like Figure 1As shown, the three-state salt removal method for irrigation tailwater in saline-alkali paddy fields according to this embodiment includes the following steps: S1. After the irrigation of saline-alkali paddy fields is completed, the tailwater discharged from the irrigation and salt washing process is discharged into the primary freezing pond 1. The primary freezing pond 1 is a trapezoidal pond with a volume of 9410 m³ and a bottom slope of 1:192. The tailwater freezes into a solid ice layer with a thickness of 1.2 m to 1.5 m. During the freezing process, the salt solution in the tailwater flows back and seeps back below the solid ice layer to form primary bottom concentrated salt solution. The primary bottom concentrated salt solution is pumped into the secondary freezing pond 3 by the first water pump 2. The secondary freezing pond 3 is a trapezoidal pond with a volume of 2211 m³. The secondary freezing pond 3 has slopes symmetrically arranged with the vertical line of the bottom as the line of symmetry, and the slopes on both sides are 1:40.

[0028] The first water pump 2, the second water pump 4, and the third water pump 7 are all sewage pumps with an inlet and outlet diameter of 80mm. Under rated operating conditions, the flow rate is 100m³ / h, the head is 50m, the net positive suction head is 13m, and the matching motor power is 5.5kw.

[0029] S2, the concentrated salt solution from the first bottom pump in the secondary freezing pool 3 is re-frozen into an ice layer at a natural low temperature. The thickness of the ice layer of the concentrated salt solution from the first bottom pump is 1.2m to 1.5m. The salt solution in the water that has been re-frozen flows back and seeps back below the ice layer to form concentrated salt solution from the second bottom pump. The concentrated salt solution from the second bottom pump is pumped into the rainproof and heated storage pool 5 by the second water pump 4.

[0030] S3, the secondary bottom-extraction concentrated salt solution in the rainproof and heated storage tank 5 is heated. The rainproof and heated storage tank 5 is a trapezoidal water tank with a volume of 765m³. The volume of the secondary bottom-extraction concentrated salt solution in the rainproof and heated storage tank 5 is 7% of the volume of the tailwater discharged from the irrigation and salt washing.

[0031] like Figure 2 As shown, a rainproof arch frame 6 is installed on the top of the rainproof and heated storage tank 5. The rainproof arch frame 6 is used to prevent the intrusion of natural precipitation. The rainproof arch frame 6 includes a double-layered arched round tube 601, a first supporting steel bar 602, a first connecting pipe 603, and a light-transmitting membrane. Multiple double-layered arched round tubes 601 are arrayed on the top of the rainproof and heated storage tank 5. The first supporting steel bar 602 is set between the double-layered arched round tubes 601. The multiple double-layered arched round tubes 601 are connected by the first connecting pipe 603. The outside of the multiple double-layered arched round tubes 601 is covered with a light-transmitting membrane with a light transmittance > 80% and a thickness > 0.8 mm.

[0032] S4. The concentrated brine solution from the secondary extraction in the rainproof and heated storage tank 5 is pumped to the solar evaporation tank 8 by the third water pump 7 for evaporation. The solar evaporation tank 8 has slopes symmetrically arranged with the vertical line of the bottom as the axis of symmetry. The slopes on both sides are 1:13. Stainless steel finned tube supports 14 are arrayed on both sides of the slope. Each stainless steel finned tube support 14 is equipped with a slope-type finned tube evaporator 11 for heating the concentrated brine solution from the secondary extraction in the solar evaporation tank 8. A solar flat plate collector 12 is installed on the top of the solar evaporation tank 8. The solar flat plate collector 12 is used to heat the concentrated brine solution from the secondary extraction, crystallizing it into solid salt. The solid salt is used as a chemical raw material. The solid ice layer in the primary freezing tank 1 and the ice layer in the secondary freezing tank 3 melt as the temperature rises, and the resulting water is used as irrigation water for the saline-alkali land the following year. The salt content of the melted water after freezing is 600-1800 mg / L, completing the salt removal process of the irrigation water for saline-alkali land.

[0033] The stainless steel finned tube support 14 is tightened to the embedded parts on the bottom slope of the rainproof and heated storage tank 5. The sloped finned tube evaporator 11 is tightened to the stainless steel finned tube support 14 with bolts. The sloped finned tube evaporator 11 is a 30×2.5 / 0.6×12.5 / 10 threaded evaporator, with each tube being 6.3m long, in two sets of 18 tubes each. The sloped finned tube evaporator 11 has a base tube outer diameter of 30mm, a wall thickness of 2.5mm, a fin thickness of 0.6mm, a height of 12.5mm, and a threaded spiral fin structure with a spacing of 10mm. The total length of a single finned tube is 6.3m. During the heating process, the sloped finned tube evaporator 11 on the bottom slope of the rainproof and heated storage tank 5 is used to accelerate the convection speed of the secondary bottom-extraction concentrated salt solution, facilitating the crystallization of the secondary bottom-extraction concentrated salt solution.

[0034] like Figure 5 As shown, the solar flat-plate collector 12 has individual collector dimensions of 2m × 1m and a rated collection temperature of 80℃. Two groups contain a total of 60 collectors, with a total collection power of 54kW. The circulating pump 10 pumps the thermal oil from the thermal oil storage tank 15 through stainless steel pipes 17 and a filter 16 into the sloped finned tube evaporator 11. The thermal oil storage tank 15, model SG(W)-2L, is a horizontal thermal oil storage tank with a nominal volume of 2L, used to store the heat transfer medium of the thermal oil system. The filter 16, model GL41H-16C-50, is a carbon steel flange-connected straight-through filter with a pressure of 1.6MPa and a diameter of 50mm. The circulating pump 10 is model IHG50-160 / 16.3m. 3This is a stainless steel vertical chemical pipeline pump with inlet and outlet diameters of 50mm, an impeller diameter of 160mm, and a design flow rate of 16.3m³ / h. It is used to drive the circulation of media in a heat transfer oil system. The stainless steel pipe (model 17) is DN50×2.5, with a diameter of 50mm and a wall thickness of 2.5mm. like Figure 3 and Figure 4 As shown, a condensation canopy 9 is installed on top of the solar evaporation tank 8. The height of the condensation canopy 9 is 10m. The condensation canopy 9 includes a non-powered fan 901, double-layer steel pipes 902, second supporting steel bars 903, a water guide trough 904, a base frame 905, a second connecting pipe 906, and a second light-transmitting membrane. The base frame 905 is installed on top of the solar evaporation tank 8. Multiple double-layer steel pipes 902 are arranged in an array on the base frame 905. Second supporting steel bars 903 are arranged between the double-layer steel pipes 902, forming a triangular support. The outer side of the multiple triangular supports is covered with a second light-transmitting membrane. The light transmittance of the second light-transmitting membrane is >80%. The thickness is greater than 0.8mm. The angle α between the hypotenuse of the triangular support and the horizontal plane is 73°. Multiple double-layer steel pipes 902 are connected by a second connecting pipe 906. Multiple non-powered fans 901 are installed on the second connecting pipe 906 at the top. The non-powered fans 901 discharge water vapor from the evaporation of the concentrated salt solution from the secondary bottom extraction. The two side plates of the base frame 905 are processed with guide water channels 904 located at the bottom of the triangular support. The 73° inclination between the hypotenuse of the triangular support and the horizontal plane is conducive to the condensation of water generated by the concentrated salt solution from the secondary bottom extraction during the evaporation process on the condensation frame 9. The water in the second light-transmitting film slides down to the guide water channel 904 at the top of the solar evaporation pool 8 and flows out.

[0035] The bottom and side walls of the solar evaporation tank 8 are respectively made of composite reinforced concrete insulation structure wall 13. The composite reinforced concrete insulation structure wall 13 is composed of a seepage-proof and freeze-resistant reinforced concrete layer, a polyurethane foam insulation layer, a seepage-proof reinforced concrete layer, a ceramic waterproof material layer, a waterproof mortar layer, and a corrosion-resistant ceramic tile layer laid from the inside out. The thickness of the seepage-proof and freeze-resistant reinforced concrete layer is 15cm, the thickness of the polyurethane foam insulation layer is 10cm, the thickness of the seepage-proof reinforced concrete layer is 15cm, the thickness of the ceramic waterproof material layer is 0.5cm, and the thickness of the waterproof mortar layer is 5cm.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A three-state desalination method for irrigation wastewater from saline-alkali paddy fields, characterized in that, Includes the following steps: S1, After the irrigation of the saline-alkali paddy field is completed, the tailwater discharged from the irrigation and salt washing is discharged into the primary freezing pond (1). The tailwater is frozen into a solid ice layer. During the freezing process, the salt solution in the tailwater flows back and seeps back into the solid ice layer to form a primary bottom-pumped concentrated salt solution. The primary bottom-pumped concentrated salt solution is pumped into the secondary freezing pond (3). S2, the concentrated salt solution in the secondary freezing pool (3) is frozen into an ice layer at a natural low temperature. The salt solution in the water that has been frozen twice flows back and seeps back into the ice layer to form the concentrated salt solution in the secondary freezing pool. The concentrated salt solution in the secondary freezing pool is pumped into the rainproof and heated storage pool (5). S3, the concentrated salt solution in the rainproof and heated storage tank (5) is heated by secondary bottom slurry extraction; S4, the concentrated salt solution in the rainproof and heated storage tank (5) is pumped to the solar evaporation tank (8) for evaporation, and the concentrated salt solution is crystallized into solid salt. The solid salt is used as a chemical raw material. The solid ice layer in the primary freezing tank (1) and the ice layer in the secondary freezing tank (3) melt as the temperature rises and form water, which is used as irrigation water for saline-alkali land in the following year. This completes the process of rinsing salt and discharging tailwater from irrigation paddy fields in saline-alkali land.

2. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: The thickness of the solid ice layer in the tailwater in S1 is 1.2m to 1.5m, the thickness of the frozen ice layer in the concentrated salt solution from the first bottom pumping in S2 is 1.2m to 1.5m, and the volume of the concentrated salt solution from the second bottom pumping in the rainproof and heated storage tank (5) in S3 is 7% of the volume of the tailwater discharged from the irrigation and salt washing.

3. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: In S1, the concentrated salt solution from the first bottom pump is pumped to the secondary freezing tank (3) by the first water pump (2). In S2, the concentrated salt solution from the second bottom pump is pumped to the rainproof and warm storage tank (5) by the second water pump (4). In S4, the concentrated salt solution from the second bottom pump in the rainproof and warm storage tank (5) is pumped to the solar evaporation tank (8) by the third water pump (7) for evaporation.

4. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: The primary freezing pool (1) is a trapezoidal pool with a bottom slope of 1:

192. The secondary freezing pool (3) is also a trapezoidal pool with slopes symmetrically arranged with the vertical line of the bottom as the symmetry line. The slopes on both sides are 1:

40.

5. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: The rainproof and heated storage tank (5) is a trapezoidal water tank. A rainproof canopy arch (6) is provided on the top of the rainproof and heated storage tank (5). The rainproof canopy arch (6) includes a double-layer arched round pipe (601), a first supporting steel bar (602), a first connecting pipe (603), and a first light-transmitting canopy film. Multiple double-layer arched round pipes (601) are arrayed on the top of the rainproof and heated storage tank (5). A first supporting steel bar (602) is provided between the double-layer arched round pipes (601). Multiple double-layer arched round pipes (601) are connected by a first connecting pipe (603). The outer side of multiple double-layer arched round pipes (601) is covered with a first light-transmitting canopy film.

6. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: The solar evaporation tank (8) in S4 is equipped with a condensation shed (9) on top. The condensation shed (9) is 10m high and includes a non-powered fan (901), double-layer steel pipes (902), second supporting steel bars (903), a water guide trough (904), a base frame (905), a second connecting pipe (906), and a second light-transmitting membrane. The solar evaporation tank (8) is equipped with a base frame (905) on top. Multiple double-layer steel pipes (902) are arranged in an array on the base frame (905). Second supporting steel bars (903) are arranged between the double-layer steel pipes (902). The double-layer steel pipe (902) and the second supporting steel bar (903) form a triangular support. The outer side of the multiple triangular supports is covered with a second light-transmitting film. The angle α between the hypotenuse of the triangular support and the horizontal plane is 73°. The multiple double-layer steel pipes (902) are connected by a second connecting pipe (906). Multiple non-powered fans (901) are installed on the second connecting pipe (906) at the top. The non-powered fans (901) discharge water vapor from the secondary bottom-extraction concentrated salt dissolved water evaporation. The two side plates of the bottom plate frame (905) are processed with guide water troughs (904) located at the bottom of the triangular support.

7. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, characterized in that: The bottom and side walls of the solar evaporation pool (8) are respectively made of composite reinforced concrete insulation structure wall (13). The composite reinforced concrete insulation structure wall (13) is composed of a seepage-proof and freeze-resistant reinforced concrete layer, a polyurethane foam insulation layer, a seepage-proof reinforced concrete layer, a ceramic waterproof material layer, a waterproof mortar layer, and an anti-corrosion ceramic tile layer laid from the inside out.

8. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 7, characterized in that: The thickness of the impermeable and frost-resistant reinforced concrete layer is 15cm, the thickness of the polyurethane foam insulation layer is 10cm, the thickness of the impermeable reinforced concrete layer is 15cm, the thickness of the ceramic waterproof material layer is 0.5cm, and the thickness of the waterproof mortar layer is 5cm.

9. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 1, 6, or 7, characterized in that: The solar evaporation pool (8) is symmetrically arranged with the vertical line of the bottom of the pool as the symmetry line. The slopes on both sides are 1:13 respectively. Stainless steel finned tube supports (14) are arranged in an array on both sides of the slope. Each stainless steel finned tube support (14) is equipped with a slope-type finned tube evaporator (11) for heating the concentrated salt solution in the solar evaporation pool (8) after secondary bottom extraction.

10. The three-state salt removal method for irrigation wastewater from saline-alkali paddy fields according to claim 9, characterized in that: A solar flat plate collector (12) is installed on the top of the solar evaporation pool (8).

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