System for preparing sodium thiosulfate based on sodium sulfide

Abstract

The utility model discloses a system for preparing sodium thiosulfate based on sodium sulfide, which comprises a conveying unit used for conveying compressed air flow and sodium sulfide waste alkali liquor to a micro-channel reactor according to preset flow respectively; the micro-channel reactor is connected with the conveying unit through a pipeline, and is used for carrying out reaction under a first preset condition after the air flow and the sodium sulfide waste alkali liquid are in full contact, and conveying a reaction product to the gas-liquid separation unit; the gas-liquid separation unit is connected with the micro-channel reactor through a pipeline and is used for carrying out gas-liquid separation on the reaction product output by the micro-channel reactor under a second preset condition and conveying a first part of separated liquid as circulating liquid to the micro-channel reactor again; the second part of separation liquid is to be output; wherein the separation liquid is a mixed liquid containing sodium thiosulfate. According to the system disclosed by the embodiment, the micro-channel reactor is arranged, so that the mass transfer rate of air to a liquid phase can be accelerated, and the conversion efficiency of sodium sulfide is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of preparing sodium thiosulfate based on sodium sulfide, and in particular relates to a system for preparing sodium thiosulfate based on sodium sulfide. Background Art

[0002] Biological denitrification and denitrification are divided into heterotrophic denitrification and autotrophic denitrification. Heterotrophic denitrification refers to the process in which denitrifying bacteria use organic matter as a carbon source and electron donor to provide energy to reduce nitrate and nitrite to nitrogen gas. Autotrophic denitrification uses reducing substances such as hydrogen, elemental sulfur, sulfide, iron or iron ions, ammonia nitrogen, etc. as electron donors. Among them, denitrifying Thiobacillus is an obligate inorganic chemolithoautotrophic bacterium that obtains energy in the process of oxidizing sulfide. Sulfur autotrophic denitrifying bacteria mostly use elemental sulfur and sulfide (S 2- , HS - , H2S), S2O3 2- As an electron donor.

[0003] When elemental sulfur is used as an electron donor, the mass transfer efficiency becomes an important factor limiting the denitrification efficiency due to the correlation between the particle size and surface area of ​​sulfur particles. Therefore, the specific surface area of ​​elemental sulfur limits its own denitrification efficiency. In addition, elemental sulfur is insoluble in water, which also affects its denitrification efficiency.

[0004] When sulfide is used as an electron donor, it can effectively avoid the problem of low denitrification efficiency caused by low mass transfer efficiency because sulfide is usually easily dissolved in water. However, sulfide is often corrosive, toxic and has a strong odor. In addition, high concentrations of sulfide will inhibit the activity of denitrifying bacteria. Therefore, when sulfide is used as an electron donor, it is easy to cause pipeline damage and black and smelly water. Sodium thiosulfate is easily soluble in water and is more easily contacted and absorbed by sulfur autotrophic denitrifying bacteria, so it has a better denitrification effect. Utility Model Content

[0005] The utility model provides a system for preparing sodium thiosulfate based on sodium sulfide. The system can efficiently convert sodium sulfide in sodium sulfide waste alkali liquor into sodium thiosulfate, which not only reduces the content of sodium sulfide in the sodium sulfide waste alkali liquor, but also the generated sodium thiosulfate can further serve as an electron donor for biological denitrification and denitrification, which is beneficial to the treatment of industrial wastewater.

[0006] To achieve the above-mentioned purpose, according to the first aspect of an embodiment of the present application, a system for preparing sodium thiosulfate based on sodium sulfide is provided, the system comprising: a conveying unit, used to convey the compressed air flow and the sodium sulfide waste alkali liquid to a microchannel reactor according to a preset flow rate respectively; the microchannel reactor, the microchannel reactor and the conveying unit are connected by a pipeline, used to make the air flow and the sodium sulfide waste alkali liquid fully contact and react under a first preset condition, and convey the reaction product to a gas-liquid separation unit; the gas-liquid separation unit, the gas-liquid separation unit and the microchannel reactor are connected by a pipeline, used to perform gas-liquid separation on the reaction product output by the microchannel reactor under a second preset condition, and convey the first portion of the separated liquid after separation as a circulating liquid to the microchannel reactor again; the second portion of the separated liquid is to be output; wherein the separated liquid is a mixed liquid containing sodium thiosulfate.

[0007] Optionally, the system further includes: a biological denitrification unit, which contains sulfur autotrophic denitrifying bacteria, a carbon source and industrial wastewater; the biological denitrification unit is connected to the gas-liquid separation unit, for receiving the separation liquid output by the gas-liquid separation unit, and performing autooxic denitrification and heterooxic denitrification under the action of the separation liquid, and outputting effluent whose total nitrogen index meets the third preset condition.

[0008] Optionally, the gas-liquid separation unit includes: a gas-liquid separator; the gas-liquid separator is connected to the microchannel reactor, and is used for performing gas-liquid separation on the reaction products output by the microchannel reactor; the gas-liquid separator is provided with a liquid level meter, and the liquid level meter is used to control the volume of the retained separation liquid in the gas-liquid separator to always remain constant.

[0009] Optionally, the gas-liquid separation unit further includes: a jacket; the jacket is wrapped around the outer surface of the gas-liquid separator; the jacket contains circulating hot water for heating the gas-liquid separator and maintaining the gas-liquid separator at a preset temperature.

[0010] Optionally, the gas-liquid separation unit further includes: a constant temperature water tank; the constant temperature water tank is connected to the jacket through a pipeline; the constant temperature water tank receives the circulating hot water output by the jacket, heats the circulating hot water to a preset temperature, and then transports it to the jacket again through a hot water circulation pump.

[0011] Optionally, a back pressure valve is provided on the gas-liquid separator; the back pressure valve is used to adjust the reaction pressure of the system and discharge the separated gas in the gas-liquid separator.

[0012] Optionally, a drain valve is provided on the gas-liquid separator; the drain valve is connected to the biological denitrification unit through a pipeline; the drain valve is used to transport excess separation liquid in the gas-liquid separator to the biological denitrification unit according to a third preset flow rate.

[0013] Optionally, the system also includes: a circulation pump; the input end of the circulation pump is connected to the output end of the gas-liquid separation unit via a pipeline; the output end of the circulation pump is connected to the input end of the microchannel reactor via a pipeline; the circulation pump is used to transport the first separation liquid of the gas-liquid separation unit to the microchannel reactor according to a fourth preset flow rate.

[0014] Optionally, the conveying unit includes a first conveying unit and a second conveying unit; the first conveying unit includes an air pressure pump and a flow meter, the air pressure pump is connected to the microchannel reactor through a pipeline, the flow meter is arranged on the input end pipeline of the microchannel reactor, the air pressure pump is used to compress the collected air into an air flow and convey it to the microchannel reactor; the flow meter is arranged on the input end pipeline of the microchannel reactor, and is used to control the air flow output by the air pressure pump to be conveyed to the microchannel reactor according to a first preset flow rate; the second conveying unit includes a feed pump, the feed pump is connected to the microchannel reactor through a pipeline, and the feed pump is used to control the sodium sulfide waste alkali liquid to be conveyed to the microchannel reactor according to a second preset flow rate.

[0015] To achieve the above-mentioned purpose, according to the second aspect of an embodiment of the present application, a method for preparing sodium thiosulfate based on sodium sulfide is also provided, the method comprising: controlling the flowmeter to transport the air flow compressed by the air pressure pump to the microchannel reactor at a first preset flow rate; and controlling the feed pump to transport the sodium sulfide waste alkali liquid to the microchannel reactor at a second preset flow rate; controlling the air flow and the sodium sulfide waste alkali liquid in the microchannel reactor to react under a first preset condition, and after the reaction is completed, the microchannel reactor transports the reaction product to a gas-liquid separator; controlling the reaction product in the gas-liquid separator to perform gas-liquid separation under a second preset condition to obtain a separated liquid and a separated gas; the separated gas is discharged through a back pressure valve, and the first portion of the separated liquid is transported to the microchannel reactor as a circulating liquid through a circulating pump at a fourth preset flow rate, and the second portion of the separated liquid is to be discharged; wherein the separated liquid is a mixed liquid containing sodium thiosulfate.

[0016] Optionally, the method further comprises: controlling the volume of the retained separation liquid in the gas-liquid separator by controlling the height of a liquid level meter, and discharging excess separation liquid in the gas-liquid separator through a drain valve.

[0017] Optionally, the volume ratio of the flow rate of the first separation liquid to the retained separation liquid is 10-150.

[0018] Optionally, the method further includes: transporting the excess separation liquid to the biological denitrification unit, and the excess separation liquid serves as an electron donor and combines with sulfur-autotrophic denitrifying bacteria and carbon sources in the biological denitrification unit to biologically denitrify the industrial wastewater to generate effluent whose total nitrogen index meets a third preset condition; wherein the ratio of the total sulfur content in the electron donor in the biological denitrification unit to the total nitrogen content in the industrial wastewater is 0.9-1.2.

[0019] Compared with the prior art, an embodiment of the utility model provides a system for preparing sodium thiosulfate based on sodium sulfide, the system comprising: a conveying unit, used to convey the compressed air flow and the sodium sulfide waste alkali liquid to a microchannel reactor according to preset flow rates respectively; the microchannel reactor, the microchannel reactor is connected to the conveying unit through a pipeline, used to make the air flow and the sodium sulfide waste alkali liquid fully contact and react under a first preset condition, and convey the reaction product to a gas-liquid separation unit; the gas-liquid separation unit, the gas-liquid separation unit is connected to the microchannel reactor through a pipeline, used to perform gas-liquid separation on the reaction product output by the microchannel reactor under a second preset condition, and convey the first portion of the separated liquid after separation to the microchannel reactor as a circulating liquid again; the second portion of the separated liquid is to be output; wherein the separated liquid is a mixed liquid containing sodium thiosulfate. By setting up a microchannel reactor, the system of this embodiment can utilize the high mass transfer efficiency between gas and liquid in the microchannel reactor to accelerate the mass transfer rate of air to the liquid phase, thereby accelerating the oxidation reaction of sodium sulfide, effectively shortening the reaction time, and improving the conversion efficiency of sodium sulfide; thereby, not only the content of sodium sulfide in the wastewater is reduced, but the generated sodium thiosulfate can also be further used as an electron donor for biological denitrification and denitrification, which is beneficial to the treatment of wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0021] Figure 1 A schematic diagram of the structure of a system for preparing sodium thiosulfate based on sodium sulfide provided in one embodiment of the utility model;

[0022] Figure 2 A schematic flow chart of a method for preparing sodium thiosulfate based on sodium sulfide is provided in one embodiment of the utility model. DETAILED DESCRIPTION

[0023] In order to make the purpose, features and advantages of the utility model more obvious and easy to understand, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0024] like Figure 1 As shown, it is a structural schematic diagram of a system for preparing sodium thiosulfate based on sodium sulfide provided by one embodiment of the utility model.

[0025] A system for preparing sodium thiosulfate based on sodium sulfide, the system at least comprising: a conveying unit, used for conveying a compressed air flow and a sodium sulfide waste alkali liquid to a microchannel reactor according to preset flow rates respectively; the microchannel reactor, the microchannel reactor and the conveying unit are connected through a pipeline, used for reacting the air flow and the sodium sulfide waste alkali liquid under a first preset condition after sufficient contact, and conveying the reaction product to a gas-liquid separation unit; the gas-liquid separation unit, the gas-liquid separation unit and the microchannel reactor are connected through a pipeline, used for performing gas-liquid separation on the reaction product output from the microchannel reactor under a second preset condition, and conveying the first portion of the separated liquid after separation to the microchannel reactor again as a circulating liquid; the second portion of the separated liquid is to be output; wherein the separated liquid is a mixed liquid containing sodium thiosulfate.

[0026] Specifically, the output end of the conveying unit is connected to the input end of the microchannel reactor, the output end of the microchannel reactor is connected to the input end of the gas-liquid separator, and the output end of the gas-liquid separator is connected to the input end of the microchannel reactor. Preferably, the input end of the microchannel reactor is located at the bottom of the microchannel reactor; the output end of the microchannel reactor is located at the top of the microchannel reactor; the input end of the gas-liquid separator is located at the top of the gas-liquid separator, and the output end of the gas-liquid separator is located at the bottom of the gas-liquid separator.

[0027] The conveying unit is used to collect external air and convey the compressed air flow to the microchannel reactor according to a first preset flow rate; the conveying unit is also used to collect sodium sulfide waste alkali liquid and convey the sodium sulfide waste alkali liquid to the microchannel reactor according to a second preset flow rate.

[0028] A microchannel reactor is a microreactor with a channel equivalent diameter between 10 and 300 microns (or 1000 microns) manufactured using precision machining technology. The "micro" in the microchannel reactor means that the channel of the process fluid is at the micron level, rather than the small size of the microreaction equipment or the small output of the product. A microchannel reactor can contain millions or tens of millions of microchannels, so it can also achieve a very high output. The microstructure inside the microchannel reactor gives the microreactor equipment a very large specific surface area, which can be hundreds or even thousands of times the specific surface area of ​​a stirred tank. The microreactor has excellent heat and mass transfer capabilities, and can achieve instantaneous uniform mixing of materials and efficient heat transfer.

[0029] The microchannel reactor of this embodiment can fully disperse the air flow in the sodium sulfide waste alkali liquid, so that after the two are fully in contact, a sufficient chemical reaction occurs under the first preset conditions to generate a reaction product; the microchannel reactor can then transport the reaction product to the gas-liquid separation unit.

[0030] The gas-liquid separation unit generates separation gas and separation liquid after separation; the separation gas is discharged through the gas-liquid separation unit, and the separation liquid is divided into two parts; the first part of the separation liquid is transported to the input end of the microchannel reactor as a circulating liquid, and the second part of the separation liquid is to be output.

[0031] By setting up a microchannel reactor, the system of this embodiment can utilize the high mass transfer efficiency between gas and liquid in the microchannel reactor to accelerate the mass transfer rate of air to the liquid phase, thereby accelerating the oxidation reaction of sodium sulfide, effectively shortening the reaction time, and improving the conversion efficiency of sodium sulfide; thereby, not only the content of sodium sulfide in the wastewater is reduced, but the generated sodium thiosulfate can also be further used as an electron donor for biological denitrification and denitrification, which is beneficial to the treatment of wastewater.

[0032] It should be noted that the sodium sulfide waste alkali liquor is also a kind of industrial wastewater.

[0033] In a preferred embodiment, the conveying unit includes a first conveying unit and a second conveying unit; the first conveying unit includes an air pressure pump and a flow meter, the air pressure pump is connected to the microchannel reactor through a pipeline, and the air pressure pump is used to compress the collected air into an air flow and convey it to the microchannel reactor; the flow meter is arranged on the input end pipeline of the microchannel reactor, and is used to control the air flow output by the air pressure pump to be conveyed to the microchannel reactor according to a first preset flow rate; the second conveying unit includes a feed pump, the feed pump is connected to the microchannel reactor through a pipeline, and the feed pump is used to control the sodium sulfide waste alkali liquid to be conveyed to the microchannel reactor according to a second preset flow rate.

[0034] The system also includes: a circulation pump; the input end of the circulation pump is connected to the output end of the gas-liquid separation unit through a pipeline; the output end of the circulation pump is connected to the input end of the microchannel reactor through a pipeline; the circulation pump is used to transport the first portion of the separation liquid of the gas-liquid separation unit to the microchannel reactor according to a fourth preset flow rate.

[0035] Specifically, the air pressure pump compresses the collected air into an air flow and then inputs the air flow into the microchannel reactor from the bottom of the microchannel reactor at a first preset flow rate; the feed pump inputs the collected sodium sulfide waste alkali liquid into the microchannel reactor from the bottom of the microchannel reactor at a second preset flow rate; at the same time, the circulation pump transports the first separation liquid output from the bottom of the gas-liquid separation unit from the bottom of the microchannel reactor to the microchannel reactor at a fourth preset flow rate.

[0036] In this embodiment, the first portion of separated liquid in the gas-liquid separation unit is transported to the microchannel reactor as a circulating liquid, thereby improving the mass transfer efficiency of the air flow in the sodium sulfide waste alkali liquid, achieving sufficient mixing between the gas and liquid in the microchannel reactor, and thus improving the conversion rate of sodium sulfide in the wastewater.

[0037] In a preferred embodiment, the gas-liquid separation unit includes: a gas-liquid separator, a jacket and a constant temperature water tank connected to the jacket by a pipeline; the gas-liquid separator is connected to the microchannel reactor and is used to perform gas-liquid separation on the reaction product output by the microchannel reactor; the gas-liquid separator is provided with a liquid level gauge, a drain valve and a back pressure valve; the liquid level gauge is used to control the volume of the retained separation liquid in the gas-liquid separator to remain constant; the drain valve is used to discharge the excess separation liquid in the gas-liquid separator according to a third preset flow rate so that the liquid level in the liquid level gauge remains constant; the back pressure valve is used to discharge the separation gas in the gas-liquid separator; the jacket contains circulating hot water, which is used to heat the gas-liquid separator and maintain the gas-liquid separator at a preset temperature; the constant temperature water tank receives the circulating hot water output by the jacket, and after heating the circulating hot water to a preset temperature, it is transported to the jacket again through a hot water circulation pump.

[0038] Specifically, the separated gas after separation by the gas-liquid separator is discharged through the back pressure valve at the top of the gas-liquid separator, and the separated liquid is divided into two parts; the first separated liquid is transported to the microchannel reactor as the circulating liquid, and a part of the separated liquid in the second separated liquid is discharged through the drain valve, and the other part of the separated liquid is retained in the gas-liquid separator as the retained separated liquid; the volume of the retained separated liquid can be effectively controlled by controlling the liquid level meter, and the excess separated liquid can be discharged through the drain valve. Thus, the proportional relationship between the flow rate of the circulating liquid and the volume of the retained liquid can be effectively controlled, which not only improves the stability of the system operation, but also improves the mass transfer efficiency of the gas-liquid phase in the microchannel reactor, thereby improving the conversion rate of sodium sulfide.

[0039] Here, an emergency vent valve is also provided on the top of the gas-liquid separator; and a pressure gauge for adjusting the system pressure is also provided in the system for preparing sodium thiosulfate based on sodium sulfide.

[0040] In a preferred embodiment, the system further comprises a biological denitrification unit, wherein the biological denitrification unit contains sulfur autotrophic denitrifying bacteria, a carbon source and / or industrial wastewater; the biological denitrification unit is connected to the gas-liquid separation unit, for receiving the separation liquid output by the gas-liquid separation unit, and performing autooxic denitrification and isooxic denitrification under the action of the separation liquid, and outputting effluent whose total nitrogen index meets the third preset condition.

[0041] Here, the industrial wastewater can be the industrial wastewater obtained after the sodium sulfide is removed in the above steps, or it can be the industrial wastewater added additionally. When the separated liquid is used as both an electron donor and a wastewater containing N pollutants, the industrial wastewater is not needed; when the separated liquid is used only as an electron donor, the industrial wastewater needs to be added to the biological denitrification unit.

[0042] In this embodiment, the oxidation product containing Na2S2O3 obtained by the above oxidation reaction is also used as an electron donor for sulfur autotrophic denitrifying bacteria, thereby reducing the use of organic carbon sources in the denitrification process.

[0043] like Figure 2 As shown, it is a schematic diagram of a process for preparing sodium thiosulfate based on sodium sulfide provided by one embodiment of the utility model.

[0044] A method for preparing sodium thiosulfate based on sodium sulfide, the method comprising at least the following steps:

[0045] S201, controlling the flowmeter to deliver the air flow compressed by the air pressure pump to the microchannel reactor at a first preset flow rate; and controlling the feed pump to deliver the sodium sulfide waste alkali liquid to the microchannel reactor at a second preset flow rate;

[0046] S202, controlling the air flow and the sodium sulfide waste alkali liquid in the microchannel reactor to react under a first preset condition, and after the reaction is completed, the microchannel reactor transports the reaction product to a gas-liquid separator;

[0047] S203, controlling the reaction product in the gas-liquid separator to perform gas-liquid separation under the second preset conditions to obtain separation liquid and separation gas; the separation gas is discharged through the back pressure valve, and the first portion of the separation liquid is transported to the microchannel reactor as a circulating liquid through a circulating pump at a fourth preset flow rate, and the second portion of the separation liquid is to be discharged; wherein the separation liquid is a mixed liquid containing sodium thiosulfate.

[0048] Specifically, the concentration of Na2S in the sodium sulfide waste lye is C I100-30000 mg / l; preferably, the concentration of Na2S in the sodium sulfide waste lye is C I The ratio between the first preset flow rate and the second preset flow rate is 10-150; preferably, the ratio between the first preset flow rate and the second preset flow rate is 20-60.

[0049] The first preset condition is used to indicate that the reaction temperature T is 70-90°C, the reaction pressure P is 0.5-1Mpa, and the reaction time is 0.1-6h. The second preset condition is used to indicate that the reaction temperature is 70-90°C, and the reaction pressure P is 0.5-1Mpa.

[0050] This embodiment determines the optimal conditions for sulfide to be oxidized into sodium thiosulfate by controlling the process conditions (such as reaction time, reaction temperature, reaction pressure gas-liquid ratio, circulation volume, etc.), thereby improving the recovery rate of sodium thiosulfate.

[0051] In a preferred embodiment, the method further includes: transporting the excess separation liquid to the biological denitrification unit, and the excess separation liquid is used as an electron donor to carry out biological denitrification of industrial wastewater with sulfur autotrophic denitrifying bacteria and carbon source in the biological denitrification unit to generate effluent whose total nitrogen index meets the third preset condition; wherein the ratio of total sulfur in the electron donor in the biological denitrification unit to total nitrogen in the industrial wastewater is 0.9-1.2.

[0052] In the biological denitrification unit of this embodiment, autotrophic denitrification and heterotrophic denitrification are carried out simultaneously; Na2S2O3 provided for autotrophic denitrification as an electron donor can effectively reduce the amount of carbon source added in the normally used heterotrophic denitrification.

[0053] In a preferred embodiment, the method further includes: controlling the volume of the retained separation liquid in the gas-liquid separator by controlling the height of the liquid level meter, and discharging excess separation liquid in the gas-liquid separator through a drain valve; wherein the ratio of the flow rate of the first separation liquid to the volume of the retained separation liquid is 10-150; more preferably, the ratio of the flow rate of the first separation liquid to the volume of the retained separation liquid is 20-60.

[0054] In the microchannel reactor, low-valent sodium sulfide undergoes the following oxidation reaction with oxygen in the air:

[0055] Na2S+O2+H2O→Na2S2O3+2NaOH formula (1);

[0056] Na2S2O3+2O2+2NaOH→2Na2SO4+H2O Formula (2).

[0057] The calculation formula of reaction time τ is:

[0058]

[0059] Here, due to V M Much smaller than V R , so the above formula can be approximated as:

[0060]

[0061] Under the above conditions, this technology can be used to efficiently convert Na2S in waste alkali liquid into Na2S2O3 through air oxidation.

[0062] In the following examples, the calculation formula for the conversion rate (X) of Na2S is as follows:

[0063]

[0064] Wherein, C1 is the concentration of Na2S in the sodium sulfide waste alkali solution; C0 is the concentration of Na2S in the separated liquid output by the discharge valve of the gas-liquid separator.

[0065] The selectivity (S) of Na2S2O3 is calculated as follows:

[0066]

[0067] In the formula, C P It is the concentration of Na2S2O3 output by the gas-liquid separator drain valve.

[0068] Example 1

[0069] The waste alkali solution containing 19638 mg / l sodium sulfide (C I =19638mg / l) using a feed pump at a flow rate of 0.4l / h (Q I =0.4 l / h) into the input end of the microchannel reactor, and the volume of the retained separation liquid in the gas-liquid separator was kept at 2 L (V R =1L), then the reaction time τ = 5h. The air flow is 36l / h (Q O ) is injected into the input end of the microchannel reactor, then R o =Q O / Q I =90. Maintain the reaction pressure P of the microchannel reactor at 1 MPa, the reaction temperature T at 90°C, and the circulation flow rate Q of the first separation liquid R is 40l / h, that is, R = Q R / V R =20. When the reaction system reaches stability, the Na2S concentration C0 in the excess separation liquid discharged from the gas-liquid separator discharge valve under this condition is 178 mg / l, and the Na2S2O3 concentration C PIt is 9446 mg / l, the calculated Na2S conversion rate is 99.1%, and the selectivity of Na2S2O3 is 47.9%.

[0070] Comparative Example 1

[0071] The only difference from Example 1 is that no microchannel reactor is used for the reaction.

[0072] The waste alkali solution containing 19638 mg / l sodium sulfide (C I =19638mg / l) using a feed pump at a flow rate of 0.4l / h (Q I =0.4 l / h) into the input end of the channel reactor, and the volume of the retained separation liquid in the gas-liquid separator was kept at 2 L (V R =1L), then the reaction time τ = 5h. The air flow is 36l / h (Q O ) is driven into the input end of the channel reactor, then R o =Q O / Q I =90. Maintain the reaction pressure P of the channel reactor = 1 MPa, the reaction temperature T = 90°C, and the circulation flow rate Q of the first separation liquid R is 40l / h, that is, R = Q R / V R = 20. When the reaction system reaches stability, under this condition, the Na2S concentration in the excess separation liquid discharged from the gas-liquid separator drain valve is 15571 mg / l, the Na2S2O3 concentration is 2007 mg / l, the calculated Na2S conversion rate is 20.7%, and the Na2S2O3 selectivity is 48.7%.

[0073] Comparative Example 2

[0074] The only difference from Example 1 is that the liquid oxidized by the microchannel reactor is not circulated.

[0075] The waste alkali solution containing 19638 mg / l sodium sulfide (C I =19638mg / l) using a feed pump at a flow rate of 0.4l / h (Q I =0.4 l / h) into the input end of the microchannel reactor, and the volume of the retained separation liquid in the gas-liquid separator was kept at 2 L (V R =1L), then the reaction time τ = 5h. The air flow is 36l / h (Q O ) is injected into the input end of the microchannel reactor, then R o =Q O / Q I=90. The reaction pressure of the microchannel reactor was maintained at P = 1 MPa and the reaction temperature was maintained at T = 90°C. When the reaction system reached stability, under this condition, the Na2S concentration in the excess separation liquid discharged from the gas-liquid separator drain valve was measured to be 15553 mg / l, the Na2S2O3 concentration was 2015 mg / l, the calculated Na2S conversion rate was 20.8%, and the Na2S2O3 selectivity was 48.7%.

[0076] Example 2 to Example 8

[0077] The volume of the retained separation liquid in the gas-liquid separator was maintained at 2 L, and the reaction conditions and results of Examples 2 to 8 were obtained by changing the other reaction conditions in Example 1 as shown in Table 1.

[0078] Table 1: Reaction results of Examples 2 to 8

[0079]

[0080]

[0081] It can be seen from the results in Table 1 that, using the method of the utility model, when the oxidation reaction conditions are within the optimal range used in the utility model, the oxidation rate of Na2S oxidation in the sodium sulfide waste alkali solution can be significantly improved.

[0082] Example 9

[0083] The sulfur-containing wastewater is effectively converted into thiosulfate by the method in Example 1. At this time, the concentration of sodium thiosulfate obtained is 9446 mg / L. The separated liquid discharged by the drain valve is used as an electron donor to ensure the smooth denitrification of the biological denitrification unit. In this reaction process section, autotrophic and heterotrophic denitrification can be carried out simultaneously. The principle equation of sulfur-type autotrophic denitrification involved is as follows (7):

[0084] 0.877S2O3 2- +NO3 - +0.456CO2+0.709H2O→0.0915C5H7O2N+0.733H + +0.454N2+1.733S04 2-

[0085] Formula (7);

[0086] The water volume of this wastewater plant is 150m 3 / h, the water quality indicators entering the biological denitrification unit are shown in Table 2.

[0087] Table 2: Water quality indicators of wastewater

[0088]

[0089] Theoretical calculation: According to conventional denitrification, if 1 mg of nitrate nitrogen is removed, 3.7 mg of COD is required, that is, 2.47 mg of methanol. This project requires a carbon source dosage to remove 40 mg / L of nitrate nitrogen, and the COD consumption is 40*37=148 mg / L, and the available COD is 30 mg / L. Then 118 mg / L of COD needs to be supplemented. The amount of methanol converted is 118*2.47 / 3.7=78.8 mg / L. The actual amount of methanol added in operation is 86 mg / L. The total nitrogen index of the effluent is 7.9 mg / L.

[0090] Now, in order to save carbon source, first add sulfur autotrophic denitrifying bacteria to the biological denitrification unit for domestication. After the domestication is completed, add the separation solution containing sodium thiosulfate prepared in Example 1 to the wastewater. At the same time, add alkalinity to control the pH value between 7-8.

[0091] Table 3: Water sample conditions and denitrification results of various wastewaters

[0092]

[0093] When S / N is less than 1, insufficient electron donors will limit denitrification, reduce the denitrification capacity of the denitrification tank, and cause unqualified effluent. When S / N is greater than 1, as S / N increases, the system removal rate will not increase significantly, and it will cause a waste of sodium thiosulfate, so the optimal S / N of the system is 1.

[0094] From the above equation, we can see that Na2S2O3 autotrophic denitrifying bacteria will produce acidity, so additional alkalinity needs to be increased. If the alkalinity is not increased, the H produced by the sulfur autotrophic denitrification reaction cannot be completely neutralized. + , long-term operation will also lead to too low pH value of effluent, which will reduce the denitrification effect of biological denitrification unit. Since alkalinity is generated during heterotrophic denitrification, when autotrophic denitrification and heterotrophic denitrification exist simultaneously in the biological denitrification unit, the acidity and alkalinity generated by the two will be neutralized. Therefore, in order to ensure the stable operation of the biological denitrification unit, the separation liquid containing sodium thiosulfate and carbon source methanol prepared in Example 1 are added at the same time; the pH value is adjusted by adding alkalinity; the specific implementation plan is shown in Table 4 below.

[0095] Table 4: Reaction results of different water samples in the biological denitrification unit

[0096]

[0097] According to the Na2S2O3 autotrophic denitrification system, the most suitable S / N ratio is 1, and no alkalinity is required. The carbon source is methanol, and the system can operate stably when the methanol dosage is 1 / 3 of the theoretical calculated value, and can effectively save 2 / 3 of the carbon source dosage.

[0098] In this embodiment, thiosulfate in the prepared sodium thiosulfate solution is used as an electron donor. In the rear end deep denitrification treatment unit, heterotrophic and autotrophic denitrification can be carried out in a coordinated manner, so that the amount of carbon source added for heterotrophic denitrification is greatly reduced.

[0099] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0100] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0101] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0102] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0103] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

[0104] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0105] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0106] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the utility model, which should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A system for preparing sodium thiosulfate based on sodium sulfide, characterized in that: The system comprises: A conveying unit is used to convey the compressed air flow and the sodium sulfide waste alkali solution to the microchannel reactor according to preset flow rates respectively; The microchannel reactor is connected to the conveying unit through a pipeline, and is used to fully contact the air flow and the sodium sulfide waste alkali liquid to react under a first preset condition, and convey the reaction product to the gas-liquid separation unit; The gas-liquid separation unit is connected to the microchannel reactor through a pipeline, and is used to perform gas-liquid separation on the reaction product output by the microchannel reactor under a second preset condition, and transport the first portion of the separated liquid as a circulating liquid to the microchannel reactor again; the second portion of the separated liquid is to be output; wherein the separated liquid is a mixed liquid containing sodium thiosulfate.

2. The system according to claim 1, characterized in that Also includes: A biological denitrification unit, wherein sulfur autotrophic denitrifying bacteria, a carbon source and industrial wastewater are contained in the biological denitrification unit; the biological denitrification unit is connected to the gas-liquid separation unit, and is used to receive the separation liquid output by the gas-liquid separation unit, and perform autooxic denitrification and isooxic denitrification under the action of the separation liquid, and output effluent whose total nitrogen index meets the third preset condition.

3. The system according to claim 2, characterized in that The gas-liquid separation unit comprises: a gas-liquid separator; The gas-liquid separator is connected to the microchannel reactor and is used for performing gas-liquid separation on the reaction product output by the microchannel reactor; a liquid level meter is provided on the gas-liquid separator, and the liquid level meter is used to control the volume of the retained separation liquid in the gas-liquid separator to remain constant at all times.

4. The system according to claim 3, characterized in that The gas-liquid separation unit further comprises: a jacket; The jacket wraps around the outer surface of the gas-liquid separator; the jacket contains circulating hot water for heating the gas-liquid separator and maintaining the gas-liquid separator at a preset temperature.

5. The system according to claim 4, characterized in that The gas-liquid separation unit further comprises: a constant temperature water tank; The constant temperature water tank is connected to the jacket through a pipeline; the constant temperature water tank receives the circulating hot water output by the jacket, heats the circulating hot water to a preset temperature, and then transports it to the jacket again through a hot water circulation pump.

6. The system according to claim 3, characterized in that The gas-liquid separator is provided with a back-pressure valve; the back-pressure valve is used to adjust the reaction pressure of the system and discharge the separated gas in the gas-liquid separator.

7. The system according to claim 3, characterized in that The gas-liquid separator is provided with a drain valve; the drain valve is connected to the biological denitrification unit through a pipeline; The drain valve is used to transport excess separation liquid in the gas-liquid separator to the biological denitrification unit at a third preset flow rate.

8. The system according to claim 1, characterized in that Also includes: Circulation pump; The input end of the circulation pump is connected to the output end of the gas-liquid separation unit through a pipeline; the output end of the circulation pump is connected to the input end of the microchannel reactor through a pipeline; The circulation pump is used to transport the first portion of the separated liquid of the gas-liquid separation unit to the microchannel reactor according to a fourth preset flow rate.

9. The system according to claim 1, characterized in that The conveying unit includes a first conveying unit and a second conveying unit; The first delivery unit comprises an air pressure pump and a flow meter, wherein the air pressure pump is connected to the microchannel reactor through a pipeline, and the flow meter is arranged on the input end pipeline of the microchannel reactor, and the air pressure pump is used to compress the collected air into an air flow and deliver it to the microchannel reactor; the flow meter is arranged on the input end pipeline of the microchannel reactor, and is used to control the air flow output by the air pressure pump to be delivered to the microchannel reactor according to a first preset flow rate; The second conveying unit includes a feed pump, which is connected to the microchannel reactor through a pipeline. The feed pump is used to control the sodium sulfide waste alkali liquid to be conveyed to the microchannel reactor according to a second preset flow rate.

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