A method and device for purifying sodium thiosulfate waste liquid

Abstract

The present invention provides a waste liquid purification method and device for thiopropionic acid ester series products, the method comprising: (a) sending the waste liquid into a preheater for preheating, sending it into a third-effect evaporator, evaporating and recovering ammonia, hydrogen sulfide and part of water to obtain residual liquid a; (b) sending the residual liquid a obtained in step (a) into a second-effect evaporator, evaporating and recovering part of the water, obtaining residual liquid b, and obtaining residual liquid c after four steps of desulfurization, extraction, filtration and liquid-liquid separation; (c) sending the residual liquid c obtained in step (b) into a first-effect evaporator, evaporating and recovering part of the water, filtering, and obtaining residual liquid d; (d) sending the residual liquid d obtained in step (c) into a crystallization tower to obtain high-purity sodium thiosulfate pentahydrate crystals. The present invention has the advantages of simple principle, high degree of automation, low labor intensity, high purity of recovered products, no waste discharge, and easy industrialization.

Description

Technical Field

[0001] The invention relates to a sodium thiosulfate waste liquid purification method and a device thereof, belonging to the field of production process design. Background Art

[0002] Sodium thiosulfate waste liquid contains many kinds of impurities such as organic matter, inorganic matter and dust, which makes it difficult to purify. The common purification method is to directly send the waste liquid into a distillation device to evaporate and recover part of the water and evaporable inorganic matter, and the remaining liquid is crystallized into sodium thiosulfate solid. Although this method is simple, the sodium thiosulfate obtained has too many impurities, a strong odor, few sales channels, and low economic benefits. Summary of the invention

[0003] The object of the present invention is to provide a method and device for purifying sodium thiosulfate waste liquid to overcome the above-mentioned problems in the prior art, which has the advantages of simple principle, high degree of automation, low labor intensity, high purity of recovered products, no waste discharge, and easy industrialization.

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

[0005] The present invention provides a method for purifying waste liquid of thiopropionate series products, comprising the following steps:

[0006] (a) sending the waste liquid into a preheater for preheating, and then sending it into a third-effect evaporator to evaporate and recover ammonia, hydrogen sulfide and part of water to obtain residual liquid a;

[0007] (b) feeding the residual liquid a obtained in step (a) into a second-effect evaporator to evaporate and recover part of the water to obtain residual liquid b, and then subjecting the residual liquid to four steps of desulfurization, extraction, filtration, and liquid-liquid separation to obtain residual liquid c;

[0008] (c) sending the residual liquid c obtained in step (b) into a first-effect evaporator, evaporating and recovering part of the water, and filtering to obtain a residual liquid d;

[0009] (d) feeding the residual liquid d obtained in step (c) into a crystallization tower to obtain high-purity sodium thiosulfate pentahydrate crystals.

[0010] Furthermore, in step (a), the waste liquid includes sodium thiosulfate, sodium sulfite, ammonia, hydrogen sulfide and colored particulate matter as well as residual organic matter, and the organic matter includes alkyl thioacrylate compounds, and / or alkyl thiopropionate compounds, and / or alkyl acrylate compounds, and / or alkyl propionate compounds.

[0011] Furthermore, in steps (a), (b) and (c), the temperature of each evaporator is 50-80°C, preferably 55-60°C.

[0012] Furthermore, in steps (a), (b) and (c), the pressure of each evaporator is less than -0.095 MPa.

[0013] Furthermore, in step (a), the waste liquid is filtered to remove dust and impurities before preheating, and the filter mesh has an aperture of 20 μm-30 μm.

[0014] Furthermore, in step (a), the waste liquid is preheated to 50° C. by a preheater.

[0015] Furthermore, in step (a), the mass concentration of sodium thiosulfate in the residual liquid a is 30-60%.

[0016] Furthermore, in step (b), the mass concentration of sodium thiosulfate in the residual liquid b is 60-63%.

[0017] Furthermore, in step (b), the desulfurizing agent in the desulfurization operation is a sodium sulfite solution, and the concentration of the sodium sulfite solution itself is not limited, because the sodium sulfite contained in the waste liquid itself also acts as a desulfurizing agent, and the sodium sulfite will be converted into sodium thiosulfate.

[0018] Furthermore, in step (b), the mass ratio of the sodium sulfite in the sodium sulfite solution to the residual liquid b is 0:50-1:50, which is adjusted according to the composition of the residual liquid b.

[0019] Furthermore, in step (b), after the desulfurization operation, the color of the residual liquid b changes from yellow to light green.

[0020] Furthermore, in step (b), the extraction operation is used to extract organic matter in the residual liquid b.

[0021] Furthermore, in step (b), the extractant in the extraction operation is ethyl propionate, but it is obviously not limited to ethyl propionate, and any solvent that is a good solvent and has a boiling point significantly different from that of the organic matter in the residual liquid b can be selected.

[0022] Furthermore, in step (b), the volume ratio of the extractant in the extraction operation to the residual liquid b is 1:0.1-1:10, preferably 1:1.

[0023] Furthermore, in step (b), the extractant in the extraction operation can be recycled. When the extraction effect of the recycled extractant is not good, a distillation tower is used to separate the extractant and the organic matter, and the separated extractant is recycled again, and the separated organic matter is recycled.

[0024] Furthermore, in step (b), the filtering operation is used to filter and recover the sodium sulfite crystals.

[0025] Furthermore, in step (b), the pore size of the filter mesh in the filtering operation is 20 μm-30 μm.

[0026] Furthermore, in step (b), during the filtering operation, the filter screen is cleaned with water.

[0027] Furthermore, in step (b), the liquid-liquid separation operation is used to separate the extractant extracted with organic matter from the inorganic phase to obtain a residual liquid c.

[0028] Furthermore, in step (c), the filtering operation is used to filter out color particles.

[0029] Furthermore, in step (c), the pore size of the filter in the filtering operation is 10 μm-15 μm.

[0030] Furthermore, in step (c), during the filtering operation, the filter screen is cleaned with 5% hydrogen peroxide.

[0031] Furthermore, in step (c), the mass concentration of sodium thiosulfate in the residual liquid d is 63-64%.

[0032] To implement the above method, the present invention also provides a waste liquid purification device for thiopropionate series products, comprising:

[0033] A preheater, a third effect evaporator, a second effect evaporator, a desulfurization kettle, a washing kettle, a filter, a separator, a first effect evaporator, a filter, a buffer kettle and a crystal tower connected in sequence through pipelines;

[0034] The top gas outlet of the third effect evaporator is also connected to a condenser for recovering ammonia, hydrogen sulfide and water;

[0035] The top gas outlet of the second-effect evaporator is also connected to a condenser for recovering water;

[0036] The top gas outlet of the first-effect evaporator is also connected to a condenser for recovering water.

[0037] Furthermore, the top of the crystal tower is provided with a spray device, and the bottom is provided with an air cooling device, and the liquid is sprayed from the top of the crystal tower to the bottom of the crystal tower to obtain crystals.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] ① The principle of the present invention is simple and can be easily industrialized.

[0040] ② The present invention has a high degree of automation, low labor intensity and high purity of the recovered product.

[0041] ③ The present invention has no waste discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention is a process flow chart of a sodium thiosulfate waste liquid purification method and device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0044] Example 1 Sodium thiosulfate waste liquid purification device of the present invention

[0045] The process flow chart of the sodium thiosulfate waste liquid purification method and device of this embodiment is as follows Figure 1 shown.

[0046] The device of this embodiment includes:

[0047] A preheater, a third effect evaporator, a second effect evaporator, a desulfurization kettle, a washing kettle, a filter, a separator, a first effect evaporator, a filter, a buffer kettle and a crystal tower connected in sequence through pipelines;

[0048] The top gas outlet of the third effect evaporator is also connected to a condenser for recovering ammonia, hydrogen sulfide and water;

[0049] The top gas outlet of the second-effect evaporator is also connected to a condenser for recovering water;

[0050] The top gas outlet of the first-effect evaporator is also connected to a condenser for recovering water.

[0051] Among them, the top of the crystal tower is provided with a spray device, and the bottom is provided with an air cooling device. Liquid is sprayed from the top of the crystal tower to the bottom of the crystal tower to obtain crystals.

[0052] Example 2

[0053] The process flow chart of the sodium thiosulfate waste liquid purification method and device of this embodiment is as follows Figure 1 shown.

[0054] The waste liquid of this embodiment includes sodium thiosulfate (about 40%), sodium sulfite (about 1%), ammonia, hydrogen sulfide and colored particulate matter as well as a small amount of residual organic matter, wherein the organic matter includes alkyl thioacrylate compounds, and / or alkyl thiopropionate compounds, and / or alkyl acrylate compounds, and / or alkyl propionate compounds.

[0055] This embodiment uses the device of embodiment 1 to purify sodium thiosulfate waste liquid, comprising the following steps:

[0056] (a) opening a triple-effect evaporator, making its internal pressure less than -0.095 MPa, and maintaining the internal temperature at about 60° C.; removing dust and impurities from the waste liquid through a filter (the filter mesh has an aperture of 20 μm), and then sending the waste liquid to a preheater to be preheated to 50° C., and then sending the waste liquid to a third-effect evaporator for evaporation and recovering ammonia, hydrogen sulfide and part of water with a condenser to obtain a residual liquid a with a mass concentration of 50% of sodium thiosulfate;

[0057] (b) feeding the raffinate a obtained in step (a) into a second-effect evaporator, evaporating and recovering part of the water by a condenser to obtain a raffinate b having a mass concentration of 62% of sodium thiosulfate;

[0058] The residual liquid b is sent to a desulfurization kettle for desulfurization operation, and a 10% sodium sulfite solution is introduced, the mass ratio of sodium sulfite in the sodium sulfite solution to the residual liquid b is 1:54, after fully mixing for 2 minutes, it is sent to a washing kettle for extraction operation, ethyl propionate is introduced, the volume ratio of ethyl propionate to the residual liquid b is 1:1, after fully mixing for 10 minutes, it is sent to a filter (the filter mesh has a pore size of 20 μm) for filtration operation, sodium sulfite crystals are recovered, and the liquid is sent to a separator to separate the extractant extracted with organic matter from the inorganic phase to obtain a residual liquid c;

[0059] (c) sending the residual liquid c obtained in step (b) into a first-effect evaporator, evaporating and recovering part of the water by a condenser, and then sending it into a filter (the filter mesh has a pore size of 10 μm) for filtration to remove color particles, thereby obtaining a residual liquid d with a mass concentration of sodium thiosulfate of 63-64%;

[0060] (d) feeding the residual liquid d obtained in step (c) into a crystal tower, and spraying the residual liquid d from the top of the crystal tower to the bottom of the crystal tower to obtain high-purity (≥99) sodium thiosulfate pentahydrate crystals.

[0061] Among them, ethyl propionate can be recycled. After multiple extractions, the extraction effect is not good, so it is passed into a distillation tower for purification. The purified ethyl propionate is continued to be used, and the purified organic matter is recycled.

[0062] When the filtering effect of the filter in step (a) is poor, it is soaked in water and cleaned; when the filtering effect of the filter in step (b) is poor, it is soaked in water and cleaned; when the filtering effect of the filter in step (c) is poor, it is soaked in 5% hydrogen peroxide and cleaned.

[0063] Example 3

[0064] The process flow chart of the sodium thiosulfate waste liquid purification method and device of this embodiment is as follows Figure 1 shown.

[0065] The waste liquid of this embodiment includes sodium thiosulfate (about 30%), sodium sulfite (about 1%), ammonia, hydrogen sulfide and colored particulate matter as well as a small amount of residual organic matter, wherein the organic matter includes alkyl thioacrylate compounds, and / or alkyl thiopropionate compounds, and / or alkyl acrylate compounds, and / or alkyl propionate compounds.

[0066] This embodiment uses the device of embodiment 1 to purify sodium thiosulfate waste liquid, comprising the following steps:

[0067] (a) opening a triple-effect evaporator, making its internal pressure less than -0.095 MPa, and maintaining the internal temperature at about 60° C.; removing dust and impurities from the waste liquid through a filter (the filter mesh has an aperture of 20 μm), and then sending the waste liquid to a preheater to be preheated to 50° C., and then sending the waste liquid to a third-effect evaporator for evaporation and recovering ammonia, hydrogen sulfide and part of water with a condenser to obtain a residual liquid a with a mass concentration of 46% of sodium thiosulfate;

[0068] (b) feeding the raffinate a obtained in step (a) into a second-effect evaporator, evaporating and recovering part of the water by a condenser to obtain a raffinate b having a mass concentration of 61% of sodium thiosulfate;

[0069] The residual liquid b is sent to a desulfurization kettle for desulfurization operation, and a 10% sodium sulfite solution is introduced, the mass ratio of sodium sulfite in the sodium sulfite solution to the residual liquid b is 1:54, after fully mixing for 2 minutes, it is sent to a washing kettle for extraction operation, ethyl propionate is introduced, the volume ratio of ethyl propionate to the residual liquid b is 1:1, after fully mixing for 10 minutes, it is sent to a filter (the filter mesh has a pore size of 20 μm) for filtration operation, sodium sulfite crystals are recovered, and the liquid is sent to a separator to separate the extractant extracted with organic matter from the inorganic phase to obtain a residual liquid c;

[0070] (c) sending the residual liquid c obtained in step (b) into a first-effect evaporator, evaporating and recovering part of the water by a condenser, and then sending it into a filter (the filter mesh has a pore size of 10 μm) for filtration to remove color particles, thereby obtaining a residual liquid d with a mass concentration of sodium thiosulfate of 63-64%;

[0071] (d) feeding the residual liquid d obtained in step (c) into a crystal tower, and spraying the residual liquid d from the top of the crystal tower to the bottom of the crystal tower to obtain high-purity (≥99) sodium thiosulfate pentahydrate crystals.

[0072] Among them, ethyl propionate can be recycled. After multiple extractions, the extraction effect is not good, so it is passed into a distillation tower for purification. The purified ethyl propionate is continued to be used, and the purified organic matter is recycled.

[0073] When the filtering effect of the filter in step (a) is poor, it is soaked in water and cleaned; when the filtering effect of the filter in step (b) is poor, it is soaked in water and cleaned; when the filtering effect of the filter in step (c) is poor, it is soaked in 5% hydrogen peroxide and cleaned.

Claims

1. A method for purifying sodium thiosulfate waste liquid, characterized in that: The following steps are involved: (a) sending the waste liquid into a preheater for preheating, and then sending it into a third-effect evaporator for evaporation and recovery of ammonia, hydrogen sulfide and part of water to obtain residual liquid a; (b) feeding the residual liquid a obtained in step (a) into a second-effect evaporator to evaporate and recover part of the water to obtain residual liquid b, and then subjecting the residual liquid to four steps of desulfurization, extraction, filtration, and liquid-liquid separation to obtain residual liquid c; (c) sending the residual liquid c obtained in step (b) into a first-effect evaporator, evaporating and recovering part of the water, and filtering to obtain a residual liquid d; (d) feeding the residual liquid d obtained in step (c) into a crystallization tower to obtain high-purity sodium thiosulfate pentahydrate crystals; Wherein, in step (a), the waste liquid includes sodium thiosulfate, sodium sulfite, ammonia, hydrogen sulfide and colored particulate matter and residual organic matter, and the organic matter includes alkyl thioacrylate compounds, and / or alkyl thiopropionate compounds, and / or alkyl acrylate compounds, and / or alkyl propionate compounds; Wherein, in steps (a), (b) and (c), the temperature of each evaporator is 50-80°C; the pressure of each evaporator is less than -0.095Mpa; Wherein, in step (b), the residual liquid b is sent to a desulfurization kettle for desulfurization operation, and a 10% sodium sulfite solution is introduced, and the mass ratio of sodium sulfite in the sodium sulfite solution to the residual liquid b is 1:54; The mass concentration of sodium thiosulfate in the residual liquid a is 30-60%; the mass concentration of sodium thiosulfate in the residual liquid b is 60-63%; and the mass concentration of sodium thiosulfate in the residual liquid d is 63-64%.

2. The method according to claim 1, characterized in that In steps (a), (b) and (c), the temperature of each evaporator is 55-60°C.

3. The method according to claim 1, characterized in that In step (a), before preheating, the waste liquid is first filtered to remove dust and impurities, the filter mesh has an aperture of 20 μm-30 μm, and the filter mesh is washed with water.

4. The method according to claim 1, characterized in that: In step (a), the waste liquid is preheated to 50° C. in a preheater.

5. The method according to claim 1, characterized in that In step (b), the extractant in the extraction operation is ethyl propionate; the volume ratio of the extractant to the residual liquid b is 1:0.1-1:

10.

6. The method according to claim 5, characterized in that The volume ratio of the extractant to the residual liquid b is 1:

1.

7. The method according to claim 1, characterized in that In step (b), the extractant in the extraction operation can be recycled. When the recycled extractant has a poor extraction effect, a distillation tower is used to separate the extractant and the organic matter, and the separated extractant is recycled again, and the separated organic matter is recovered.

8. The method according to claim 1, characterized in that In step (b), the pore size of the filter in the filtering operation is 20 μm-30 μm, and the filter is washed with water.

9. The method according to claim 1, characterized in that: In step (c), the pore size of the filter in the filtering operation is 10 μm-15 μm, and the filter is cleaned with 5% hydrogen peroxide.

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