CN115448521A - Method for treating gas desulfurization waste liquid - Google Patents
Method for treating gas desulfurization waste liquid Download PDFInfo
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- CN115448521A CN115448521A CN202211229441.XA CN202211229441A CN115448521A CN 115448521 A CN115448521 A CN 115448521A CN 202211229441 A CN202211229441 A CN 202211229441A CN 115448521 A CN115448521 A CN 115448521A
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- oxidation
- desulfurization
- waste liquid
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/727—Treatment of water, waste water, or sewage by oxidation using pure oxygen or oxygen rich gas
Abstract
The invention discloses a method for treating gas desulfurization waste liquid, in particular to a method for extracting salt from desulfurization waste liquid, which comprises the following steps: (1) Carrying out oxidation treatment on the desulfurization waste liquid under the oxygen condition, and then carrying out filtering operation to obtain an oxidation desulfurization liquid; (2) Carrying out decoloring treatment on the oxidized desulfurization solution and then filtering to obtain a decolored desulfurization solution; (3) And (3) carrying out negative pressure evaporation concentration on the decolorized and desulfurized liquid, cooling and crystallizing step by step to obtain solid ammonium sulfate and ammonium thiocyanate. According to the embodiment of the invention, oxygen is used as the oxidant for oxidation treatment, compared with air or other oxidants, the method can save the operation cost, reduce the operation cost in the oxidation process, and avoid resource waste and solid waste generation; in addition, the oxidation conversion rate of ammonium thiosulfate in the oxidation reaction of the desulfurization solution can reach more than 90 percent.
Description
Technical Field
The invention relates to the field of treatment of desulfurization waste liquid generated by gas desulfurization, in particular to a desulfurization waste liquid treatment method.
Background
The desulfurization waste liquid is a part of waste liquid which must be discharged in the production process of the coke-oven gas desulfurization and decyanation process, and the desulfurization process generates ammonium thiocyanate, ammonium thiosulfate, ammonium sulfate and other secondary salts and is continuously accumulated because of side reactions in the desulfurization process. When the total content of the secondary salts in the desulfurization solution exceeds 300g/L, the desulfurization effect is influenced, the energy consumption is increased, the desulfurization efficiency is reduced, and the higher the content of the secondary salts in the desulfurization solution is, the lower the desulfurization efficiency is.
By integrating the treatment methods of the desulfurization waste liquid in the current market, three types are summarized: (1) the salts in the waste liquid are crystallized and recovered step by utilizing different solubilities, and the condensed water is recovered to supplement the desulfurization liquid, such as an evaporative crystallization method, a fractional crystallization method and the like. (2) Directly blending the desulfurization solution into the coking coal. (3) The desulfurized liquid and the sulfur paste are mixed and burned to prepare acid. The desulfurization waste liquid is discharged without being treated, which wastes materials and seriously pollutes the environment. Therefore, the resource treatment and the environment-friendly recovery of the desulfurization waste liquid become the key for the survival of enterprises. The treatment cost is high due to the problems of immature flow, high cost, low yield and the like of the treatment of the coking desulfurization waste liquid.
At present, the salt is extracted by fractional crystallization in China, and the salt is purified and separated by utilizing the solubility difference of several inorganic salts. However, the problems of low purity of the extracted inorganic salt and low economic benefit exist at present.
Disclosure of Invention
Aiming at the technical problems, the inventor obtains a set of technical scheme for treating the desulfurization waste liquid by solving the treatment problem of the desulfurization waste liquid generated by the desulfurization of coke oven gas and researching the mechanism of mutual conversion between ammonium thiosulfate and ammonium sulfate in the desulfurization waste liquid. According to the scheme, firstly, the desulfurization waste liquid is oxidized by using oxygen, ammonium thiosulfate in the desulfurization liquid is converted into ammonium sulfate, a tri-salt system in the desulfurization waste liquid is converted into a di-salt system, the salt extraction purity can reach more than 97% through concentration and crystallization, the separation process flow is simple, the economic benefit is improved, and industrialization can be applied.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for extracting salt from a desulfurized waste stream, the method comprising:
(1) Carrying out oxidation treatment on the desulfurization waste liquid under the oxygen condition, and then carrying out filtering operation to obtain an oxidation desulfurization liquid;
(2) Carrying out decoloration treatment on the oxidized desulfurized liquid and then filtering to obtain a decolored desulfurized liquid;
(3) And (3) carrying out negative pressure evaporation concentration on the decolorized and desulfurized liquid, cooling and crystallizing step by step to obtain solid ammonium sulfate and ammonium thiocyanate.
Advantageous effects
The invention has the advantages that:
1. the oxygen oxidation is utilized, so that the waste of resources and the generation of solid waste caused by the use of a catalyst are avoided, the running cost can be reduced, and the separation method is simple.
2. Under the oxidation of oxygen, the conversion rate of the ammonium thiosulfate in the desulfurization solution generated by coke oven gas desulfurization is over 90 percent when the tri-salt system is converted into the di-salt system, the ammonium thiocyanate and the ammonium sulfate can be extracted through evaporation, concentration and crystallization, and the purity can be over 97 percent.
According to the embodiment of the invention, oxygen is used as the oxidant for oxidation treatment, compared with air or other oxidants, the method can save the operation cost, reduce the operation cost in the oxidation process, and avoid resource waste and solid waste generation; in addition, the oxidation conversion rate of ammonium thiosulfate in the oxidation reaction of the desulfurization solution can reach more than 90 percent.
Detailed Description
According to one embodiment of the present invention, there is disclosed a method for extracting salt from a desulfurization waste liquid, the method comprising:
(1) Carrying out oxidation treatment on the desulfurization waste liquid under the oxygen condition, and then carrying out filtering operation to obtain an oxidation desulfurization liquid;
(2) Carrying out decoloring treatment on the oxidized desulfurization solution and then filtering to obtain a decolored desulfurization solution;
(3) And (3) carrying out negative pressure evaporation concentration on the decolorized and desulfurized liquid, cooling and crystallizing step by step to obtain solid ammonium sulfate and ammonium thiocyanate.
According to the embodiment of the invention, oxygen is used as the oxidant for oxidation treatment, compared with air or other oxidants, the method can save the operation cost, reduce the operation cost in the oxidation process, and avoid resource waste and solid waste generation; in addition, the oxidation conversion rate of ammonium thiosulfate in the oxidation reaction of the desulfurization solution can reach more than 90 percent.
According to another embodiment of the present invention, wherein,
the content of ammonium thiosulfate in the desulfurization waste liquid to be treated is 120-180mg/L.
According to the method, the desulfurization waste liquid with the ammonium thiosulfate content as high as 180mg/L can be treated, and the conversion rate of the ammonium thiosulfate in the oxidation reaction of the concentrated desulfurization liquid can reach 90 percent, preferably more than 97 percent.
According to another embodiment of the present invention, wherein,
in the step (1), the pressure of the oxygen is 1.7MPa to 2.3MPa.
According to another embodiment of the present invention, wherein,
in the step (1), the pressure of oxygen is 2.0MPa.
Under the oxygen pressure, the conversion rate of ammonium thiosulfate can be greatly improved, the corrosion of reaction equipment is prevented, and the cost of the reaction equipment is reduced. Specifically, when the oxygen pressure is lower than 1.7MPa, the conversion rate decreases; and when the oxygen pressure is higher than 2.3MPa, the reaction equipment is corroded, and the cost of the reaction equipment is increased.
According to another embodiment of the present invention, wherein
In the step (1), the temperature of the oxidation is 90 ℃ to 130 ℃, and the time of the oxidation is 6 hours to 12 hours.
According to another embodiment of the present invention, wherein
In the step (1), the temperature of the oxidation is 120 ℃ to 130 ℃, and the time of the oxidation is 9 hours to 12 hours.
According to another embodiment of the present invention, wherein
In the step (1), the temperature of the oxidation is 130 ℃ and the time of the oxidation is 9 hours.
At the above oxidation temperature and oxidation time, the conversion rate of ammonium thiosulfate can be greatly improved.
Examples
Example 1
Three-salt indexes of the coke oven gas desulfurization waste liquid in a certain coke-oven plant are 135.15g/L ammonium thiosulfate, 248.78g/L ammonium thiocyanate and 37.05g/L ammonium sulfate.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: oxygen is introduced into 500ml of desulfurization waste liquid, and the mixture is heated for 9 hours under the conditions that the pressure is 2.0MPa and the temperature is 120 ℃ to obtain the oxidative desulfurization liquid. And (5) sampling and detecting. The conversion rate of ammonium thiosulfate is 92.63%, and the content of ammonium thiocyanate is basically not changed.
After oxidation, carrying out decolorization treatment on the oxidation desulfurization solution, and then filtering to obtain decolorized desulfurization solution;
and after the decolorization treatment, carrying out negative pressure evaporation concentration on the decolorized and desulfurized liquid, cooling and crystallizing step by step to obtain solids, wherein the obtained solids are ammonium sulfate and ammonium thiocyanate.
Example 2
Taking three salt indexes of the coke oven gas desulfurization waste liquid of a certain coke-oven plant as 129.35g/L of ammonium thiosulfate, 254g/L of ammonium thiocyanate and 19.85g/L of ammonium sulfate.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: oxygen is introduced into 500ml of desulfurization waste liquid, the mixture is heated for 9 hours under the conditions that the pressure is 2.0MPa and the temperature is 130 ℃ to obtain the oxidative desulfurization liquid. Sampling and detecting, wherein the conversion rate of the ammonium thiosulfate is 97.83 percent, and the content of the ammonium thiocyanate is basically unchanged.
Thereafter, the same decoloring treatment step and cooling crystallization step as in example 1 were performed.
Example 3
Three salt indexes of the desulfurization waste liquid of coke oven gas of a certain coke-oven plant are 127.55g/L, 251.78g/L and 28.45g/L respectively.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: oxygen is introduced into 4L of desulfurization waste liquid, the mixture is heated for 9 hours under the conditions that the pressure is 2.0MPa and the temperature is 130 ℃, and the oxidative desulfurization liquid is obtained. Sampling and detecting, wherein the conversion rate of the ammonium thiosulfate is 98.19%, and the content of the ammonium thiocyanate is basically not changed.
Thereafter, the same decoloring treatment step and cooling crystallization step as in example 1 were performed.
Example 4
Three salt indexes of the desulfurization waste liquid of coke oven gas of a certain coke-oven plant are 177.82g/L, 267.68g/L and 28.79g/L respectively.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: oxygen is introduced into 4L of desulfurization waste liquid, the mixture is heated for 9 hours under the conditions that the pressure is 2.0MPa and the temperature is 130 ℃, and the oxidative desulfurization liquid is obtained. Sampling and detecting, wherein the conversion rate of the ammonium thiosulfate is 97.82%, and the content of the ammonium thiocyanate is basically not changed.
Thereafter, the same decoloring treatment step and cooling crystallization step as in example 1 were performed.
Comparative example 1
Three-salt indexes of the coke oven gas desulfurization waste liquid in a certain coke-oven plant are 135.15g/L ammonium thiosulfate, 248.78g/L ammonium thiocyanate and 37.05g/L ammonium sulfate.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: and (3) introducing oxygen into 500ml of desulfurization waste liquid, heating for 6h under the conditions that the pressure is 1.5MPa and the temperature is 120 ℃, and sampling and detecting. The conversion rate of ammonium thiosulfate is 65.49%, and the content of ammonium thiocyanate is basically unchanged.
Thereafter, the same decoloring treatment step and cooling crystallization step as in example 1 were performed.
Comparative example 2
Taking three salt indexes of the coke oven gas desulfurization waste liquid of a certain coke-oven plant as 129.35g/L of ammonium thiosulfate, 254g/L of ammonium thiocyanate and 19.85g/L of ammonium sulfate.
The desulfurization waste liquid high-temperature high-pressure oxidation test process comprises the following steps: and (3) introducing oxygen into 500ml of desulfurization waste liquid, heating for 9 hours at the temperature of 130 ℃ under the pressure of 1.0MPa, and sampling and detecting. The conversion rate of ammonium thiosulfate is 47.94%, and the content of ammonium thiocyanate is basically unchanged.
Thereafter, the same decoloring treatment step and cooling crystallization step as in example 1 were performed.
For comparison, the parameters of the above examples 1 to 4 and comparative examples 1 to 2 are shown in Table 1 below.
TABLE 1
From the results in table 1 it can be seen that:
in the case of examples 1 to 4, the examples of the present invention using oxygen as the oxidizing agent all achieved more than 90% of ammonium thiosulfate to be converted into ammonium sulfate, and smoothly converted the tri-salt system into the di-salt system;
more particularly, as can be seen from the comparison between example 1 and examples 2-4, when the reaction temperature is increased from 120 ℃ to 130 ℃, the conversion rate is further increased from about 92% to more than 97%, and a better technical effect is achieved;
in contrast, referring to comparative example 1, the conversion of ammonium thiosulfate was significantly reduced to 65.49% at an oxygen pressure of 1.5MPa, a reaction temperature of 120 ℃, and a reaction time of 6 hours, indicating that the conversion was very low when the oxygen pressure and the temperature and time of the reaction could not reach the specified conditions.
With further reference to comparative example 2, it can be seen that at an oxygen pressure drop of 1.0MPa, the reaction conversion is only 47.94% even when the reaction temperature is increased to 130 ℃ and the reaction time is increased to 9 hours.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (7)
1. A method for extracting salt from a desulfurized waste stream, comprising:
(1) Carrying out oxidation treatment on the desulfurization waste liquid under the oxygen condition, and then carrying out filtering operation to obtain an oxidation desulfurization liquid;
(2) Carrying out decoloring treatment on the oxidized desulfurization solution and then filtering to obtain a decolored desulfurization solution;
(3) And (3) carrying out negative pressure evaporation concentration on the decolorized and desulfurized liquid, cooling and crystallizing step by step to obtain solid ammonium sulfate and ammonium thiocyanate.
2. The method of claim 1, wherein,
the content of ammonium thiosulfate in the desulfurization waste liquid to be treated is 120-180mg/L.
3. The method of claim 1, wherein,
in the step (1), the pressure of the oxygen is 1.7MPa to 2.3MPa.
4. The method of claim 1, wherein,
in the step (1), the pressure of oxygen is 2.0MPa.
5. The method of claim 1, wherein
In the step (1), the temperature of the oxidation is 90 ℃ to 130 ℃, and the time of the oxidation is 6 hours to 12 hours.
6. The method of claim 1, wherein
In the step (1), the temperature of the oxidation is 120 ℃ to 130 ℃, and the time of the oxidation is 9 hours to 12 hours.
7. The method of claim 1, wherein
In the step (1), the temperature of the oxidation is 130 ℃ and the time of the oxidation is 9 hours.
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