A process system and method for treating waste acid containing aldehyde using manganese dioxide

Abstract

The present invention is a process system and a treatment method for treating waste acid containing formaldehyde by using manganese dioxide. The process system includes a heat exchange unit, a primary spray absorption unit, a feed-liquid mixing reaction unit, a solid-liquid separation unit, an aeration unit, a secondary spray absorption unit, and an acid storage unit connected in sequence. The primary spray absorption unit and the secondary spray absorption unit are both connected to a tail gas treatment unit, and the aeration unit is connected to an air purification unit and a salt solution storage unit. During treatment, the mixed gas is cooled by a heat exchange process, then sprayed and absorbed, and then absorbed by manganese dioxide. After solid-liquid separation, aeration is performed, and finally sprayed and absorbed twice. The waste gas generated in the process is treated and discharged, and the obtained liquid is classified and collected. The present invention uses manganese dioxide to treat waste acid containing formaldehyde, and finally obtains a hydrochloric acid solution of a certain concentration and a manganese chloride solution close to or reaching saturation, thereby improving the utilization value and economic benefits of waste acid containing formaldehyde.

Description

Technical Field

[0001] The invention relates to the technical field of industrial formaldehyde-containing waste acid treatment, and in particular to a process system for treating formaldehyde-containing waste acid using manganese dioxide and a treatment method thereof. Background Art

[0002] With the rapid economic development in China, the demand for organophosphorus scale inhibitors is increasing. In the production process of organophosphorus scale inhibitors, a large amount of waste gas containing formaldehyde and hydrogen chloride is generated. These waste gases are absorbed by water and become waste acid containing formaldehyde. The presence of formaldehyde in the solution affects the use and treatment of waste acid. Waste acid containing formaldehyde has become a "hot potato", and manufacturers of organophosphorus scale inhibitors find it very difficult to treat waste acid. Summary of the invention

[0003] The present invention aims to solve the deficiencies of the prior art and to provide a process system and a treatment method for treating waste acid containing formaldehyde by using manganese dioxide in order to improve the economic value and utilization value of waste acid containing formaldehyde.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A process system for treating waste acid containing formaldehyde by using manganese dioxide comprises a heat exchange unit, a primary spray absorption unit, a feed-liquid mixing reaction unit, a solid-liquid separation unit, an aeration unit, a secondary spray absorption unit and an acid storage unit which are connected in sequence. The primary spray absorption unit and the secondary spray absorption unit are both connected to a tail gas treatment unit, and the aeration unit is connected to an air purification unit and a salt solution storage unit.

[0006] The heat exchange unit comprises a heat exchanger, the heat exchanger is provided with a cooling medium inlet, a cooling medium outlet, a gas inlet and a gas outlet, and the gas inlet of the heat exchanger is connected to an inlet pipe for a mixed gas of hydrogen chloride and formaldehyde;

[0007] The primary spray absorption unit comprises a primary spray absorption tower, wherein a gas inlet is provided at the lower end of the side wall of the primary spray absorption tower, a liquid outlet is provided at the bottom, a liquid inlet is provided at the top, and an exhaust port is provided at the upper end of the side wall, the gas inlet of the primary spray absorption tower is connected to the gas outlet of the heat exchanger, and the liquid inlet of the primary spray absorption tower is connected to a primary spray absorption tower water inlet pump;

[0008] The liquid-feed mixing reaction unit comprises a liquid-feed mixing reactor, a manganese dioxide feed port is arranged on the top of the side wall of the liquid-feed mixing reactor, an inlet of the liquid-feed mixing reactor is connected to a liquid outlet of a primary spray absorption tower via a first acid-resistant pump, the liquid-feed mixing reactor is connected to an exhaust port of the primary spray absorption tower via a pipeline, and a pressure reducing valve is arranged on the pipeline;

[0009] The solid-liquid separation unit comprises a solid-liquid separator, which is provided with a mixture inlet, a solid outlet and a liquid outlet. The mixture inlet of the solid-liquid separator is connected to the outlet of the liquid-feed mixing reactor via a second acid-resistant pump, and the solid outlet of the solid-liquid separator is connected to the liquid-feed mixing reactor via a solid reagent return pump.

[0010] The aeration unit comprises an aeration tank, the inlet of the aeration tank is connected to the liquid outlet of the solid-liquid separator through a third acid-resistant pump, and an aeration head is arranged in the aeration tank;

[0011] The air purification unit includes an air purifier, and the air purifier is connected to the aeration head in the aeration tank through an aeration pump;

[0012] The salt solution storage unit comprises a salt solution storage tank, and the outlet at the bottom of the aeration tank is connected to the salt solution storage tank;

[0013] The secondary spray absorption unit comprises a secondary spray absorption tower, the lower end of the side wall of the secondary spray absorption tower is provided with a gas inlet, the bottom is provided with a liquid outlet, the top is provided with a liquid inlet, and the upper end of the side wall is provided with an exhaust port, the gas inlet of the secondary spray absorption tower is connected to the gas outlet at the top of the aeration tank through a fourth acid-resistant pump, and the liquid inlet of the secondary spray absorption tower is connected to the secondary spray absorption tower water inlet pump;

[0014] The acid storage unit comprises a hydrochloric acid storage tank, which is connected to the liquid outlet of the secondary spray absorption tower through a fifth acid-resistant pump;

[0015] The tail gas treatment unit includes a first tail gas processor and a second tail gas processor. The first tail gas processor is connected to the pipeline where the pressure reducing valve between the first-level spray absorption tower and the liquid mixing reactor is located, and the second tail gas processor is connected to the exhaust port of the second-level spray absorption tower.

[0016] A liquid foam filtering plate layer is arranged in the upper part of the aeration tank.

[0017] A circulating liquid port is provided on the aeration tank below the liquid foam filter plate layer, and the circulating liquid port is connected to the top liquid inlet of the primary spray absorption tower through a sixth acid-resistant pump.

[0018] The liquid-feed mixing reactor is provided with a stirring device, and the stirring device is connected with a stirring motor.

[0019] The heat exchanger is provided with a serpentine heat exchange tube, and the serpentine heat exchange tube is connected with a cooling medium inlet and a cooling medium outlet.

[0020] The above-mentioned treatment method of the process system for treating waste acid containing aldehyde using manganese dioxide comprises the following specific steps:

[0021] S1. The mixed gas of hydrogen chloride and formaldehyde enters the heat exchanger through the hydrogen chloride and formaldehyde mixed gas inlet pipe, and exchanges heat with the cooling medium flowing inside the heat exchanger to reduce its own temperature;

[0022] S2, the mixed gas after cooling enters the primary spray absorption tower, the liquid inlet at the top of the primary spray absorption tower continuously sprays the absorption liquid downward to absorb the mixed gas of hydrogen chloride and formaldehyde to form the formaldehyde-containing waste acid liquid L1, and the tail gas is treated by the first tail gas processor and then discharged;

[0023] S3, the formaldehyde-containing waste acid feed liquid L1 is pumped into the feed liquid mixing reactor, and manganese dioxide is added into the feed liquid mixing reactor, the amount of manganese dioxide added and the amount of formaldehyde in the formaldehyde-containing waste acid feed liquid L1 The ratio is 1.5-5.0, and the residence time of the formaldehyde-containing waste acid feed liquid L1 in the feed liquid mixing reactor is 10min-300min, ensuring that the formaldehyde can be completely consumed, and finally obtaining the formaldehyde-free feed liquid L2;

[0024] S4, the liquid L2 from which formaldehyde has been removed is pumped into a solid-liquid separator to achieve solid-liquid separation, thereby obtaining a solution L3 and unreacted manganese dioxide, and the unreacted manganese dioxide is returned to the liquid mixing reactor through a solid reagent return pump for reuse;

[0025] S5, after the solution L3 enters the aeration tank, it is aerated with clean air. A liquid foam filter layer plate is provided on the top of the aeration tank to separate the gas from the liquid foam. The residence time of the solution L3 in the aeration tank is 10min-300min, and the volume flow rate of aeration is 0.1-200L / min. The solution L4 from which the hydrogen chloride is removed is pumped to the primary spray absorption tower for recycling. When the solution L4 is recycled and approaches or reaches the saturation of manganese chloride, the solution L4 is pumped to the salt solution storage tank for storage;

[0026] S6. The gas flowing out of the aeration tank enters the secondary spray absorption tower, and the concentration of hydrochloric acid is controlled by controlling the amount of spray water. The final hydrochloric acid solution is stored in the hydrochloric acid storage tank. The exhaust gas generated by the secondary spray absorption tower is treated by the second exhaust gas processor and then meets the emission standards.

[0027] In step S2, when operating in the primary spray absorption tower, the concentration of hydrogen chloride in the formaldehyde-containing waste acid liquid L1 is controlled to be between 1 mol / L and 5 mol / L.

[0028] In step S3, the required manganese dioxide is replenished in time at the manganese dioxide feed port according to the consumption of manganese dioxide.

[0029] The beneficial effect of the present invention is that the present invention uses manganese dioxide to treat the waste acid containing formaldehyde, and finally obtains a hydrochloric acid solution of a certain concentration and a manganese chloride solution close to or reaching saturation, thereby improving the utilization value and economic benefits of the waste acid containing formaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a processing system of the present invention;

[0031] In the figure: 1-intake pipe for hydrogen chloride and formaldehyde mixed gas; 2-heat exchanger; 3-primary spray absorption tower; 4-first acid-resistant pump; 5-liquid mixing reactor; 6-second acid-resistant pump; 7-solid-liquid separator; 8-third acid-resistant pump; 9-aeration tank; 10-fourth acid-resistant pump; 11-secondary spray absorption tower; 12-fifth acid-resistant pump; 13-hydrochloric acid storage tank; 14-secondary spray absorption tower water inlet pump; 15-air purifier; 16-aeration pump; 17-salt liquid storage tank; 18-pressure reducing valve; 19-first tail gas processor; 20-primary spray absorption tower water inlet pump; 21-solid reagent return pump; 22-second tail gas processor; 23-manganese dioxide feed port; 24-sixth acid-resistant pump;

[0032] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0034] like Figure 1 As shown, a process system for treating waste acid containing formaldehyde using manganese dioxide includes a heat exchange unit, a primary spray absorption unit, a feed-liquid mixing reaction unit, a solid-liquid separation unit, an aeration unit, a secondary spray absorption unit, and an acid storage unit connected in sequence, wherein the primary spray absorption unit and the secondary spray absorption unit are both connected to an exhaust gas treatment unit, and the aeration unit is connected to an air purification unit and a salt solution storage unit.

[0035] The heat exchange unit comprises a heat exchanger 2, on which a cooling medium inlet, a cooling medium outlet, a gas inlet and a gas outlet are provided, and the gas inlet of the heat exchanger 2 is connected to a hydrogen chloride and formaldehyde mixed gas inlet pipe 1;

[0036] The primary spray absorption unit comprises a primary spray absorption tower 3, wherein the lower end of the side wall of the primary spray absorption tower 3 is provided with a gas inlet, the bottom is provided with a liquid outlet, the top is provided with a liquid inlet, and the upper end of the side wall is provided with an exhaust port, the gas inlet of the primary spray absorption tower 3 is connected to the gas outlet of the heat exchanger 2, and the liquid inlet of the primary spray absorption tower 3 is connected to the primary spray absorption tower water inlet pump 20;

[0037] The liquid-feed mixing reaction unit comprises a liquid-feed mixing reactor 5, a manganese dioxide feed port 23 is provided on the top of the side wall of the liquid-feed mixing reactor 5, an inlet of the liquid-feed mixing reactor 5 is connected to a liquid outlet of a primary spray absorption tower 3 via a first acid-resistant pump 4, the liquid-feed mixing reactor 5 is connected to an exhaust port of the primary spray absorption tower 3 via a pipeline, and a pressure reducing valve 18 is provided on the pipeline;

[0038] The solid-liquid separation unit includes a solid-liquid separator 7, which is provided with a mixture inlet, a solid outlet and a liquid outlet. The mixture inlet of the solid-liquid separator 7 is connected to the outlet of the liquid-feed mixing reactor 5 via a second acid-resistant pump 6, and the solid outlet of the solid-liquid separator 7 is connected to the liquid-feed mixing reactor 5 via a solid medicine return pump 21.

[0039] The aeration unit comprises an aeration tank 9, the inlet of the aeration tank 9 is connected to the liquid outlet of the solid-liquid separator 7 through a third acid-resistant pump 8, and an aeration head is provided in the aeration tank 9;

[0040] The air purification unit includes an air purifier 15, and the air purifier 15 is connected to the aeration head in the aeration tank 9 through an aeration pump 16;

[0041] The salt solution storage unit comprises a salt solution storage tank 17, and the outlet at the bottom of the aeration tank 9 is connected to the salt solution storage tank 17;

[0042] The secondary spray absorption unit comprises a secondary spray absorption tower 11, wherein the lower end of the side wall of the secondary spray absorption tower 11 is provided with a gas inlet, a liquid outlet at the bottom, a liquid inlet at the top, and an exhaust port at the upper end of the side wall. The gas inlet of the secondary spray absorption tower 11 is connected to the gas outlet at the top of the aeration tank 9 through a fourth acid-resistant pump 10, and the liquid inlet of the secondary spray absorption tower 11 is connected to a secondary spray absorption tower water inlet pump 14;

[0043] The acid storage unit includes a hydrochloric acid storage tank 13, and the hydrochloric acid storage tank 13 is connected to the liquid outlet of the secondary spray absorption tower 11 through a fifth acid-resistant pump 12;

[0044] The exhaust gas treatment unit includes a first exhaust gas processor 19 and a second exhaust gas processor 22. The first exhaust gas processor 19 is connected to the pipeline where the pressure reducing valve 18 is located between the first-level spray absorption tower 3 and the liquid mixing reactor 5, and the second exhaust gas processor 22 is connected to the exhaust port of the second-level spray absorption tower 11.

[0045] A liquid foam filtering plate layer is provided in the upper part of the aeration tank 9.

[0046] The aeration tank 9 is provided with a circulating liquid port below the liquid foam filter plate layer, and the circulating liquid port is connected to the top liquid inlet of the primary spray absorption tower 3 through the sixth acid-resistant pump 24 .

[0047] The liquid-feed mixing reactor 5 is provided with a stirring device, and the stirring device is connected with a stirring motor.

[0048] The heat exchanger 2 is provided with a serpentine heat exchange tube, and the serpentine heat exchange tube is connected to a cooling medium inlet and a cooling medium outlet.

[0049] The above-mentioned treatment method of the process system for treating waste acid containing aldehyde using manganese dioxide comprises the following specific steps:

[0050] S1, the mixed gas of hydrogen chloride and formaldehyde enters the heat exchanger 2 through the hydrogen chloride and formaldehyde mixed gas inlet pipe 1, and exchanges heat with the cooling medium flowing inside the heat exchanger 2 to reduce its own temperature;

[0051] S2, the mixed gas after cooling enters the primary spray absorption tower 3, the liquid inlet at the top of the primary spray absorption tower 3 continuously sprays the absorption liquid downward to absorb the mixed gas of hydrogen chloride and formaldehyde to form the formaldehyde-containing waste acid liquid L1, and the tail gas is treated by the first tail gas processor 19 and then discharged;

[0052] S3, the waste acid liquid L1 containing formaldehyde is pumped into the liquid mixing reactor 5, and manganese dioxide is added into the liquid mixing reactor 5, the amount of manganese dioxide added to the amount of formaldehyde in the waste acid liquid L1 containing formaldehyde is 1.5-5.0, the residence time of the waste acid liquid L1 containing formaldehyde in the liquid mixing reactor 5 is 10min-300min, ensuring that the formaldehyde can be completely consumed, and finally obtaining the formaldehyde-free liquid L2;

[0053] S4, the liquid L2 from which formaldehyde has been removed is pumped into the solid-liquid separator 7 to achieve solid-liquid separation, and a solution L3 and unreacted manganese dioxide are obtained. The unreacted manganese dioxide is returned to the liquid mixing reactor 5 through the solid agent return pump 21 for reuse;

[0054] S5, after the solution L3 enters the aeration tank 9, it is aerated with clean air. A liquid foam filter layer plate is provided on the upper part of the aeration tank 9 to separate the gas from the liquid foam. The residence time of the solution L3 in the aeration tank 9 is 10min-300min, and the volume flow rate of aeration is 0.1-200L / min. The solution L4 from which the hydrogen chloride is removed is pumped to the primary spray absorption tower 3 for recycling. When the solution L4 is recycled and approaches or reaches the saturation of manganese chloride, the solution L4 is pumped to the salt solution storage tank 17 for storage;

[0055] S6. The gas flowing out of the aeration tank 9 enters the secondary spray absorption tower 11, and the concentration of hydrochloric acid is controlled by controlling the amount of spray water, and the finally obtained hydrochloric acid solution is stored in the hydrochloric acid storage tank 13. The tail gas generated by the secondary spray absorption tower 11 is treated by the second tail gas processor 22 and then meets the emission standards.

[0056] In step S2, when operating in the primary spray absorption tower 3, the concentration of hydrogen chloride in the formaldehyde-containing waste acid liquid L1 is controlled to be between 1 mol / L and 5 mol / L.

[0057] In step S3, the required manganese dioxide is replenished in time at the manganese dioxide feed port 23 according to the consumption of manganese dioxide. Specific embodiment:

[0059] A mixed gas containing hydrogen chloride and formaldehyde, in which the concentration of formaldehyde is 0.1-0.2 mol / m 3 , the concentration of hydrogen chloride is 20-30 mol / m 3 , the volume of the mixed gas is 100-150m 3 , the temperature is 70-90℃, the temperature of the mixed gas changes to 20-40℃ after passing through the heat exchanger 2, and is pumped into the primary spray absorption tower 3 and then 1-2m 3 The waste acid L1 containing aldehyde is absorbed by water to obtain the waste acid L1 containing aldehyde. The waste acid L1 containing aldehyde is pumped to the feed liquid mixing reactor 5, and 50-200 mol of manganese dioxide is added. After mixing and stirring for 40-300 minutes, the feed liquid L2 is pumped to the solid-liquid separator 7 for solid-liquid separation to obtain a solution L3 with a concentration of 0.8-0.98 m 3 and a certain mass of unreacted manganese dioxide, wherein solution L3 is pumped to aeration tank 9 for aeration, and the aeration flow rate is 0.2-1.5m 3 / min, solution L3 stays in the aeration tank for 10-200min. After aeration is completed, the remaining solution L4 is pumped into the first-level spray absorption tower 3 for the next round of absorption of the hydrogen chloride formaldehyde mixed gas, and the gas enters the second-level spray absorption tower 11. The final hydrochloric acid concentration is regulated by adjusting the volume of clean water used in the second-level spray absorption tower 11. After the absorption is completed, it is pumped into the hydrochloric acid storage tank 13. The tail gas is treated by the second tail gas processor 22 and meets the discharge standards. After the solution L4 circulates 10-20 times, it is pumped into the salt solution storage tank 17. Depending on the situation, evaporation and crystallization can be carried out to obtain manganese chloride solid, or a certain concentration of manganese chloride solution can be obtained, thereby realizing the treatment of aldehyde-containing waste acid, and finally obtaining a certain concentration of hydrochloric acid solution and a manganese chloride solution close to or reaching saturation, thereby improving the utilization value and economic benefits of the aldehyde-containing waste acid.

[0060] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for treating a process system for treating waste acid containing aldehydes using manganese dioxide, characterized in that: The process system for treating waste acid containing formaldehyde by using manganese dioxide comprises a heat exchange unit, a primary spray absorption unit, a feed-liquid mixing reaction unit, a solid-liquid separation unit, an aeration unit, a secondary spray absorption unit, and an acid liquid storage unit which are connected in sequence, wherein the primary spray absorption unit and the secondary spray absorption unit are both connected to an exhaust gas treatment unit, and the aeration unit is connected to an air purification unit and a salt liquid storage unit; the heat exchange unit comprises a heat exchanger (2), wherein the heat exchanger (2) is provided with a cooling medium inlet, a cooling medium outlet, a gas inlet, and a gas outlet, and the gas inlet of the heat exchanger (2) is connected to an inlet pipe (1) for a mixed gas of hydrogen chloride and formaldehyde; the primary spray absorption unit comprises a primary spray absorption tower (3), and the primary spray absorption tower (4) is connected to a secondary spray absorption tower (5). The spray absorption tower (3) is provided with a gas inlet at the lower end of the side wall, a liquid outlet at the bottom, a liquid inlet at the top, and an exhaust port at the upper end of the side wall; the gas inlet of the first-stage spray absorption tower (3) is connected to the gas outlet of the heat exchanger (2); the liquid inlet of the first-stage spray absorption tower (3) is connected to a first-stage spray absorption tower water inlet pump (20); the liquid mixing reaction unit comprises a liquid mixing reaction kettle (5); a manganese dioxide feed port (23) is provided at the top of the side wall of the liquid mixing reaction kettle (5); the inlet of the liquid mixing reaction kettle (5) is connected to the liquid outlet of the first-stage spray absorption tower (3) via a first acid-resistant pump (4); the liquid mixing reaction kettle (5) is connected to the exhaust port of the first-stage spray absorption tower (3) via a pipeline. The solid-liquid separation unit comprises a solid-liquid separator (7), the solid-liquid separator (7) is provided with a mixture inlet, a solid outlet and a liquid outlet, the mixture inlet of the solid-liquid separator (7) is connected to the outlet of the liquid-mixing reactor (5) through a second acid-resistant pump (6), and the solid outlet of the solid-liquid separator (7) is connected to the liquid-mixing reactor (5) through a solid agent return pump (21); the aeration unit comprises an aeration tank (9), the inlet of the aeration tank (9) is connected to the liquid outlet of the solid-liquid separator (7) through a third acid-resistant pump (8), and an aeration head is provided in the aeration tank (9); the air purification unit comprises an air purifier (1 5), the air purifier (15) is connected to the aeration head in the aeration tank (9) through an aeration pump (16); the salt solution storage unit comprises a salt solution storage tank (17), and the outlet at the bottom of the aeration tank (9) is connected to the salt solution storage tank (17); the secondary spray absorption unit comprises a secondary spray absorption tower (11), the secondary spray absorption tower (11) is provided with a gas inlet at the lower end of the side wall, a liquid outlet at the bottom, a liquid inlet at the top, and an exhaust port at the upper end of the side wall, the gas inlet of the secondary spray absorption tower (11) is connected to the gas outlet at the top of the aeration tank (9) through a fourth acid-resistant pump (10), and the liquid inlet of the secondary spray absorption tower (11) is connected to a secondary spray absorption tower water inlet pump (14);The acid liquid storage unit comprises a hydrochloric acid storage tank (13), and the hydrochloric acid storage tank (13) is connected to the liquid outlet of the secondary spray absorption tower (11) through a fifth acid-resistant pump (12); the tail gas treatment unit comprises a first tail gas processor (19) and a second tail gas processor (22), the first tail gas processor (19) is connected to the pipeline where the pressure reducing valve (18) between the primary spray absorption tower (3) and the liquid mixing reactor (5) is located, and the second tail gas processor (22) is connected to the exhaust port of the secondary spray absorption tower (11); The specific steps of processing are: S1, the mixed gas of hydrogen chloride and formaldehyde enters the heat exchanger (2) through the hydrogen chloride and formaldehyde mixed gas inlet pipe (1), and exchanges heat with the cooling medium flowing inside the heat exchanger (2), thereby reducing its own temperature; S2, the mixed gas after cooling enters the primary spray absorption tower (3), the liquid inlet at the top of the primary spray absorption tower (3) continuously sprays the absorption liquid downward to absorb the mixed gas of hydrogen chloride and formaldehyde to form the formaldehyde-containing waste acid liquid L1, and the tail gas is treated by the first tail gas processor (19) and then discharged; S3, the waste acid liquid L1 containing formaldehyde is pumped into the liquid mixing reactor (5), and manganese dioxide is added into the liquid mixing reactor (5), the mass ratio of the amount of manganese dioxide added to the amount of formaldehyde in the waste acid liquid L1 containing formaldehyde is 1.5-5.0, and the residence time of the waste acid liquid L1 containing formaldehyde in the liquid mixing reactor (5) is 10 min-300 min, so as to ensure that the formaldehyde can be completely consumed, and finally the liquid L2 free of formaldehyde is obtained; S4, the liquid L2 from which formaldehyde has been removed is pumped into a solid-liquid separator (7) to achieve solid-liquid separation, thereby obtaining a solution L3 and unreacted manganese dioxide. The unreacted manganese dioxide is returned to the liquid mixing reactor (5) through a solid reagent return pump (21) for reuse; S5, after the solution L3 enters the aeration tank (9), it is aerated with clean air. A liquid foam filter layer plate is provided on the upper part of the aeration tank (9) to separate gas from liquid foam. The residence time of the solution L3 in the aeration tank (9) is 10 min-300 min, and the volume flow rate of aeration is 0.1-200 L / min. The solution L4 from which hydrogen chloride has been removed is pumped to the primary spray absorption tower (3) for recycling. When the solution L4 is close to or reaches saturation of manganese chloride during recycling, the solution L4 is pumped to the salt solution storage tank (17) for storage; S6. The gas flowing out of the aeration tank (9) enters the secondary spray absorption tower (11), and the concentration of hydrochloric acid is controlled by controlling the amount of spray water. The hydrochloric acid solution finally obtained is stored in the hydrochloric acid storage tank (13). The tail gas generated by the secondary spray absorption tower (11) is treated by the second tail gas processor (22) and then discharged in compliance with the emission standards.

2. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 1, characterized in that: A liquid foam filtering plate layer is provided at the upper inner portion of the aeration tank (9).

3. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 2, characterized in that: The aeration tank (9) is provided with a circulating liquid port below the liquid foam filter plate layer, and the circulating liquid port is connected to the top liquid inlet of the first-stage spray absorption tower (3) through a sixth acid-resistant pump (24).

4. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 3, characterized in that: The liquid-feed mixing reactor (5) is provided with a stirring device, and the stirring device is connected to a stirring motor.

5. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 4, characterized in that: The heat exchanger (2) is provided with a serpentine heat exchange tube, and the serpentine heat exchange tube is connected to a cooling medium inlet and a cooling medium outlet.

6. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 5, characterized in that: In step S2, when operating in the first-stage spray absorption tower (3), the concentration of hydrogen chloride in the formaldehyde-containing waste acid liquid L1 is controlled to be between 1 mol / L and 5 mol / L.

7. The method for treating a process system for treating waste acid containing aldehyde by using manganese dioxide according to claim 6, characterized in that: In step S3, the required manganese dioxide is replenished in time at the manganese dioxide feed port (23) according to the consumption of manganese dioxide.

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