Desulfurization waste liquid and sulfur foam resource utilization method and application

Abstract

The invention provides a method for resource utilization of desulfurization waste liquid and sulfur foam and application, and relates to the technical field of chemical waste liquid treatment. Specifically, the method comprises the following steps: carrying out two-stage separation treatment on the desulfurization waste liquid and sulfur foam to obtain solid or molten elemental sulfur and separated clear liquid; separating the separated clear liquid into a first clear liquid and a second clear liquid; adding copper salt into the first clear liquid, and then carrying out solid-liquid separation to obtain cuprous thiocyanate and a first mother solution; sequentially carrying out concentration, cooling crystallization and solid-liquid separation on the second clear liquid to obtain ammonium thiocyanate and a second mother solution; concentrating the first mother solution and the second mother solution to obtain a concentrated salt solution; and the concentrated salt liquid and elemental sulfur are mixed and cured, and crude sulfur is obtained. The process method is simple and controllable, elemental sulfur and ammonium salt in the desulfurization waste liquid and sulfur foam are treated at the same time, the recycled crude sulfur can be subjected to resource utilization to prepare concentrated sulfuric acid, high-value by-products can be obtained at the same time, and good economic benefits and application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical waste liquid treatment, and in particular, to a method and application for the resource utilization of desulfurization waste liquid and sulfur foam. Background Art

[0002] Coke oven gas, blast furnace gas, water gas, natural gas, etc. usually require wet oxidation methods such as HPF or PDS to achieve desulfurization and purification; for example, HPF uses an alkali source ammonia and an HPF composite catalyst, and for another example, PDS uses sodium carbonate or ammonia as an alkali source and a PDS catalyst. Both achieve the absorption of inorganic sulfur such as hydrogen sulfide, or organic sulfur such as thiocyanogen and carbon disulfide by counter-current contact of the mixture of the alkali source and the catalyst with the gas phase, and obtain desulfurized liquid while obtaining the purified gas phase. In addition, the above-mentioned coal gas or natural gas can also be desulfurized and purified through a complex iron desulfurization process; using a slightly alkaline liquid-phase complex iron catalyst, when the gas and liquid are in contact, the sulfur components in the sulfur-containing raw gas are absorbed into the aqueous solution through an acid-base reaction, and the sulfur components are oxidized to elemental sulfur and separated based on the oxidation reaction of the complex iron catalyst. At the same time, the reduced complex iron catalyst can also be oxidized, transformed and recycled.

[0003] For the above desulfurization processes, desulfurization waste liquid and sulfur foam will be generated, and their main components include but are not limited to elemental sulfur, ammonium thiocyanate, ammonium thiosulfate, ammonium sulfate, etc. The desulfurization waste is produced in the form of sulfur foam liquid, desulfurization waste liquid, sulfur paste, sulfur mud or mixed salt. Taking a 1-million-ton coking plant as an example, the daily discharge of desulfurization waste liquid can be as high as 50 tons; and because the desulfurization waste liquid has irritation or pollution to water bodies, soil, human bodies, etc., it cannot be directly discharged into the natural environment and must be subjected to cleaning or resource treatment. Conventional treatment methods include but are not limited to: elemental sulfur recovery, deep treatment of waste liquid, separation and purification of mixed salts, microbial action, resource preparation of building materials, etc. However, the above methods all have their own limitations. Taking the most commonly used separation and purification of mixed salts as an example, the variety of by-products in the desulfurization waste liquid is complex, and the purity of the extracted salt products is low, resulting in low value of by-products in each line; for another example, methods such as extraction, microfiltration, evaporation and concentration are difficult to be applied in batches; for another example, the oxidation combustion method deeply oxidizes the desulfurization waste liquid to prepare sulfuric acid, which has high process raw material costs, is dangerous and explosive in the process itself, and is extremely difficult to promote.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a method for the resource utilization of desulfurization waste liquid and sulfur foam, the process method is simple and controllable, and at the same time, the elemental sulfur and ammonium salts in the desulfurization waste liquid and sulfur foam are treated. The recovered crude sulfur can be further resourcefully utilized to produce concentrated sulfuric acid, and high-value by-products can be obtained at the same time, having good economic benefits.

[0006] The second object of the present invention is to provide a method for treating desulfurized waste liquid and sulfur foam.

[0007] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0008] A method for resource utilization of desulfurized waste liquid and sulfur foam, comprising the following steps:

[0009] (1) Perform two-stage separation treatment on the desulfurized waste liquid and sulfur foam to obtain elemental sulfur (solid or molten state) and separated clear liquid; divide the separated clear liquid into a first clear liquid and a second clear liquid;

[0010] (2) Add copper salt to the first clear liquid, then perform solid-liquid separation to obtain cuprous thiocyanate and a first mother liquor;

[0011] (3) Concentrate, cool and crystallize, and perform solid-liquid separation on the second clear liquid in sequence to obtain ammonium thiocyanate and a second mother liquor;

[0012] (4) Concentrate the first mother liquor and the second mother liquor to obtain a concentrated salt solution; mix and solidify the concentrated salt solution with the elemental sulfur to obtain crude sulfur for the production of concentrated sulfuric acid.

[0013] A method for treating desulfurized waste liquid and sulfur foam, comprising the method for resource utilization of the desulfurized waste liquid and sulfur foam described above.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] The present invention first adopts two-stage separation treatment to obtain solid elemental sulfur or molten elemental sulfur collectibles with different particle sizes, and then further separates the soluble thiocyanate in the waste liquid through two treatment paths of chemical reaction and evaporation crystallization to by-product cuprous thiocyanate or ammonium thiocyanate. Finally, the mother liquor is concentrated and solidified to realize the mixed extraction of crude sulfur, so as to obtain a crude sulfur product with high yield. The crude sulfur obtained by the method for resource utilization of desulfurized waste liquid and sulfur foam of the present invention can be used for direct incineration to produce sulfuric acid, doping pyrite to produce sulfuric acid, or purifying crude sulfur to produce chemical products and other application channels, and has good economy. Description of the Drawings

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1The operation flow schematic diagram of the resource utilization method of the present invention is provided. Detailed implementation manners

[0018] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific implementation manners. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer can all be obtained as conventional products through commercial purchase. In addition, terms such as "first", "second", "1", "2", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0019] The first aspect of the present invention is to provide a method for the resource utilization of desulfurization waste liquid and sulfur foam, which mainly includes the following steps (1) to (4). As Figure 1 A feasible overall flow chart of the present invention is provided as shown.

[0020] (1) Perform two-stage separation treatment on the desulfurization waste liquid and sulfur foam to obtain elemental sulfur (solid or molten state) and separated clear liquid; divide the separated clear liquid into a first clear liquid and a second clear liquid.

[0021] In the present invention, through two-stage separation treatment, an attempt is made to separate elemental sulfur and clear liquid in the original treatment components; however, due to the low content of elemental sulfur in the desulfurization waste liquid and sulfur foam, and the tiny elemental sulfur fines may only be in the order of several micrometers, it is difficult to collect them by conventional one-stage solid-liquid separation methods.

[0022] As a preferred implementation manner, the effective components of the desulfurization waste liquid and sulfur foam include elemental sulfur, ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate; among them, in terms of mass percentage, the reference contents of the above components are respectively: elemental sulfur: ≥1%, ammonium thiocyanate: ≤25%, ammonium thiosulfate: ≤30%, ammonium sulfate: ≤20%, and the specific content ranges of each component are related to the operation of the desulfurization system.

[0023] It should be understood that the desulfurization waste liquid and sulfur foam described in the present invention may also have names such as "desulfurization foam liquid", "desulfurization waste liquid", "dilute sulfur foam" or other naming references in some specific application scenarios (such as Figure 1The dilute sulfur foam provided therein is equivalent to the desulfurized waste liquid and sulfur foam), which can be understood as an aqueous solution of elemental sulfur and ammonium salts by-produced in the desulfurization process. This is mainly because the elemental sulfur particles and ammonium salts by-produced in the desulfurization process are generated during the regeneration of the desulfurization liquid and discharged from the top of the regeneration tower in a foam-containing liquid phase state. In the present invention, the desulfurized waste liquid and sulfur foam are aqueous solutions containing micron-sized elemental sulfur particles and various types of ammonium salts (ammonium thiocyanate, ammonium thiosulfate, ammonium sulfate, etc.), that is, they exist in a suspension state containing elemental sulfur particles.

[0024] As a preferred embodiment, the pH of the desulfurized waste liquid and sulfur foam is 8 to 11.

[0025] As a preferred embodiment, the two-stage separation treatment includes a first separation treatment and a second separation treatment (and the first separation treatment is carried out prior to the second separation treatment); specifically, the first separation treatment adopts one of pressure filtration or centrifugation; the second separation treatment adopts one of phase separation treatment or centrifugation treatment.

[0026] As a more preferred embodiment, in the first separation treatment, the pressure of the pressure filtration is 0.05 MPa to 0.8 MPa, the pore size of the filter element for the pressure filtration is 1 μm to 100 μm, and the frequency of the centrifugation is 2000 rpm to 3000 rpm.

[0027] As a preferred embodiment, after the first separation treatment, the obtained filtrate is returned to the desulfurization process for recycling.

[0028] Through the physical separation effect in the first separation treatment, the liquid phase in the desulfurized waste liquid and sulfur foam is preliminarily separated. Specifically, through the first separation treatment, a filtered clear liquid and a concentrated slurry containing elemental sulfur are obtained, and this slurry is usually also produced in the form of foam.

[0029] As a preferred embodiment, in the second separation treatment, the phase separation treatment is generally carried out by one of a two-phase separator, a multi-phase separator or a sulfur melting kettle; the temperature of the phase separation treatment is 120 °C to 150 °C, and the pressure of the phase separation treatment is 0.1 MPa to 0.6 MPa.

[0030] As a preferred embodiment, in the second separation treatment, the centrifugation treatment is commonly carried out using a vertical centrifuge, and the centrifugation frequency is 2000 rpm to 3000 rpm.

[0031] Through the two action paths in the second separation treatment, the former separates through the melting point of elemental sulfur, while the latter utilizes a stronger physical separation effect to obtain molten and solid elemental sulfur respectively. Specifically, the particle size of the solid elemental sulfur obtained through the second separation treatment is not greater than 10 mm. Through the two-stage separation treatment, the separation of elemental sulfur particles and clear liquid in the desulfurized waste liquid and sulfur foam can be effectively and efficiently achieved.

[0032] As a preferred embodiment, the volume ratio of the first clear liquid to the second clear liquid is (0.1 - 99.9):(0.1 - 99.9); those skilled in the art can select and direct the distribution of the clear liquid discharged in step (1) according to the requirements for different by-products obtained in steps (2) and (3).

[0033] (2) Add a copper salt to the first clear liquid and carry out a chemical reaction, then perform solid-liquid separation to obtain cuprous thiocyanate and a first mother liquor.

[0034] As a preferred embodiment, the addition amount of the copper salt is measured based on the content of thiocyanate in the first clear liquid; the molar ratio of thiocyanate to copper ions in the copper salt > 1, and the specific dosing ratio is (1.05 - 1.2):1, more preferably 1.1:1.

[0035] As a preferred embodiment, the copper salt includes any one or more of soluble copper salts such as copper sulfate, copper chloride, and copper nitrate.

[0036] As a preferred embodiment, the solid-liquid separation in this step includes one of centrifugation or filtration; among them, the pressure of the filtration is 0.05 MPa - 0.8 MPa, the pore size of the filter element for the filtration is 1 μm - 100 μm, and the frequency of the centrifugation is 2000 rpm - 3000 rpm.

[0037] In this step, through the chemical reaction precipitation method, the thiocyanate (mainly ammonium thiocyanate) in the clear liquid reacts with the added copper salt to form insoluble cuprous thiocyanate; the cuprous thiocyanate generating solution is obtained as a cuprous thiocyanate product through a separation device, and the separated mother liquor enters a secondary concentration device to obtain a secondary concentrated salt solution.

[0038] (3) Concentrate, cool and crystallize, and perform solid-liquid separation on the second clear liquid in sequence to obtain ammonium thiocyanate and a second mother liquor.

[0039] As a preferred embodiment, the concentration includes the following steps: placing the liquid phase under negative pressure conditions and heating the material with steam to separate water. Among them, the parameter settings for the concentration include: the relative pressure of the negative pressure conditions is 0 kPa to -100 kPa, the pressure of the steam introduced for the concentration is 0.1 MPa to 0.8 MPa, and the temperature of the steam is 60 °C to 180 °C.

[0040] As a preferred embodiment, a salt solution with a total concentration of 40% to 60% is obtained through the concentration.

[0041] As a preferred embodiment, the low temperature for the cooling crystallization is 15 °C to 40 °C.

[0042] As a preferred embodiment, the solid-liquid separation in this step includes one of centrifugation or filtration; among them, the pressure for the filtration is 0.05 MPa to 0.8 MPa, the pore size of the filter element for the filtration is 1 μm to 100 μm, and the frequency for the centrifugation is 2000 rpm to 3000 rpm.

[0043] In this step, through the processes of evaporation, concentration, cooling, and crystallization, the thiocyanate ions (mainly ammonium thiocyanate) in the clear liquid are separated in solid form by solubility, and the separated mother liquor enters the secondary concentration equipment to obtain a secondary concentrated salt solution.

[0044] (4) Concentrate the first mother liquor and the second mother liquor to obtain a concentrated salt solution; mix and solidify the concentrated salt solution with the elemental sulfur to obtain crude sulfur.

[0045] As a preferred embodiment, the concentration of the first mother liquor and the second mother liquor can be carried out independently or jointly after combining the two, and those skilled in the art can make a choice according to the actual situation.

[0046] As a preferred embodiment, the concentration in this step uses the same operation method as the concentration in step (3), but the parameter characteristics involved can be independently selected according to the parameter range provided by the concentration in step (3).

[0047] As a preferred embodiment, a salt solution with a total concentration of 50% to 80% is obtained through the concentration.

[0048] As a preferred embodiment, the temperature for the solidification treatment is 40 °C to 110 °C; through the solidification treatment until the liquid phase completely volatilizes, flaky, granular or molten crude sulfur is obtained.

[0049] As a preferred embodiment, the solid or molten elemental sulfur obtained in step (1) (i.e., the particles and / or molten slurry of elemental sulfur) is combined with the concentrated brine, and the solidification treatment is carried out jointly.

[0050] The second aspect of the present invention lies in providing a method for treating desulfurized waste liquid and sulfur foam, including the method for resource utilization of desulfurized waste liquid and sulfur foam as described in the first aspect. It can be understood that when the treatment method includes the method for resource utilization of desulfurized waste liquid and sulfur foam, regardless of whether other treatment steps are introduced or the types of raw materials to be treated, it can be used as an embodiment of the present invention.

[0051] Example 1

[0052] The desulfurized waste liquid and sulfur foam used in this example are derived from the dilute sulfur foam of desulfurization waste in a certain factory, and its components are shown in Table 1 below:

[0053] Component Elemental sulfur Ammonium thiocyanate Ammonium thiosulfate Ammonium sulfate Water Content 4wt.% 11wt.% 8wt.% 4wt.% 73wt.%

[0054] (1) The dilute sulfur foam is transported to a microporous filter and filtered at a pressure of 0.2 MPa. The pore size of the pressure filter membrane is 1 μm, and clear liquid and concentrated sulfur foam are separated.

[0055] (2) The concentrated sulfur foam is first transported to a two-phase separator. The temperature in the kettle is set at 140 °C and the pressure in the kettle is set at 0.5 MPa to produce molten elemental sulfur, and at the same time, separated clear liquid is collected.

[0056] (3) 50 wt.% of the separated clear liquid is transported to a reactor. Based on the amount of ammonium thiocyanate in the clear liquid, an equal proportion of copper sulfate solution is added and stirred to generate cuprous thiocyanate precipitate. After separation by a filter press, cuprous thiocyanate by-product and separated liquid are obtained.

[0057] (4) The other 50 wt.% of the separated clear liquid is transported to an evaporator. The pressure of the evaporator is set at -50 kPa, and the material in the evaporator is indirectly heated with steam at 0.5 MPa and 158 °C for evaporation to obtain a solution with a salt concentration of 50%. The solution is transferred to a crystallizer and quenched to 30 °C, and then separated by a filter press to obtain ammonium thiocyanate by-product and separated mother liquor.

[0058] (5) The separated liquid obtained in step (3) is combined with the separated mother liquor obtained in step (4) and sent to an evaporator together. The pressure of the evaporator is set at -50 kPa, and the material in the evaporator is indirectly heated with steam at 0.5 MPa and 158 °C for evaporation to obtain a high-salt solution with a salt concentration of 75%. Further, the high-salt solution and the molten elemental sulfur obtained in step (2) are sent to a dryer for solidification treatment at 90 °C to obtain the crude sulfur product of this example.

[0059] The crude sulfur product obtained in this embodiment was tested, and the components are shown in Table 2 below.

[0060] Table 2

[0061] Component Elemental sulfur Ammonium thiocyanate Ammonium thiosulfate Ammonium sulfate Water Content 65wt.% 0.5wt.% 21wt.% 10.5wt.% 3wt.%

[0062] Example 2

[0063] It is basically the same as Example 1, with the only difference being that:

[0064] Step (1) was replaced with: The dilute sulfur foam was transported to a vertical centrifuge and centrifuged at a frequency of 2000 rpm to obtain a clear liquid and a concentrated sulfur foam.

[0065] Example 3

[0066] It is basically the same as Example 1, with the only difference being that:

[0067] Step (2) was replaced with: The concentrated sulfur foam was first transported to a vertical centrifuge and centrifuged at a frequency of 3000 rpm to produce solid elemental sulfur, and at the same time, a separated clear liquid was collected.

[0068] Example 4

[0069] It is basically the same as Example 1, with the only difference being that:

[0070] Step (2) was replaced with: The concentrated sulfur foam was first transported to a sulfur melting kettle, the temperature in the kettle was set at 125 °C, and the pressure in the kettle was 0.4 MPa to produce molten elemental sulfur, and at the same time, a separated clear liquid was collected.

[0071] Example 5

[0072] It is basically the same as Example 1, with the only difference being that:

[0073] Step (1) was replaced with: The dilute sulfur foam was transported to a vertical centrifuge and centrifuged at a frequency of 2000 rpm to obtain a clear liquid and a concentrated sulfur foam; and step (2) was replaced with: The concentrated sulfur foam was first transported to a vertical centrifuge and centrifuged at a frequency of 3000 rpm to produce solid elemental sulfur, and at the same time, a separated clear liquid was collected.

[0074] The product yields and by-product purities of each example were statistically recorded as shown in Table 3 below. Among them, the yield of thiocyanate was calculated based on the combination of cuprous thiocyanate by-products and ammonium thiocyanate by-products obtained in each example.

[0075] Table 3

[0076]

[0077] Although the present invention has been illustrated and described with reference to specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; those of ordinary skill in the art should understand that without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for the resource utilization of desulfurization waste liquid and sulfur foam, characterized in that It includes the following steps: (1) Perform two-stage separation treatment on the desulfurized waste liquid and sulfur foam to obtain elemental sulfur and separated clear liquid; divide the separated clear liquid into a first clear liquid and a second clear liquid; (2) Add a copper salt to the first clear liquid, then perform solid-liquid separation to obtain cuprous thiocyanate and a first mother liquor; (3) Perform concentration, cooling crystallization, and solid-liquid separation on the second clear liquid in sequence to obtain ammonium thiocyanate and a second mother liquor; (4) Concentrate the first mother liquor and the second mother liquor to obtain a concentrated salt solution; mix and solidify the concentrated salt solution with the elemental sulfur to obtain crude sulfur for producing concentrated sulfuric acid.

2. The method for resource utilization of desulfurized waste liquid and sulfur foam according to claim 1, characterized in that The effective components of the desulfurized waste liquid and sulfur foam include elemental sulfur, ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate; Preferably, the desulfurized waste liquid and sulfur foam include the following components by mass fraction: elemental sulfur ≥ 1%, ammonium thiocyanate ≤ 25%, ammonium thiosulfate ≤ 30%, ammonium sulfate ≤ 20%.

3. The method for resource utilization of desulfurization waste liquid and sulfur foam according to claim 1, wherein The two-stage separation treatment includes a first separation treatment and a second separation treatment; The first separation treatment adopts one of pressure filtration or centrifugation; The second separation treatment adopts one of phase separation treatment or centrifugation.

4. The method for resource utilization of desulfurized waste liquid and sulfur foam according to claim 3, characterized in that, In the first separation treatment, the pressure of the pressure filtration is 0.05 MPa to 0.8 MPa, and the pore size of the filter element for the pressure filtration is 1 μm to 100 μm; And / or, the frequency of the centrifugation is 2000 rpm to 3000 rpm.

5. The method for resource utilization of desulfurized waste liquid and sulfur foam according to claim 3, characterized in that, In the second separation treatment, the separation treatment is carried out by one of a two-phase separator, a multiphase separator, a sulfur melting kettle, or a centrifuge; Preferably, the temperature of the phase separation treatment is 120 °C to 150 °C, and the pressure of the phase separation treatment is 0.1 MPa to 0.6 MPa.

6. The method for resource utilization of desulfurized waste liquid and sulfur foam according to claim 3, characterized in that, In the second separation treatment, the frequency of the centrifugation is 2000 rpm to 3000 rpm.

7. The method for resource utilization of desulfurization waste liquid and sulfur foam according to claim 1, characterized in that The molar ratio of thiocyanate in the first clear liquid to copper ions in the copper salt is > 1; preferably, the molar ratio is (1.05 to 1.2):

1.

8. The method for resource utilization of desulfurization waste liquid and sulfur foam according to claim 1, wherein In step (3) and / or step (4), the concentration includes: heating the material with steam under negative pressure conditions and separating water; Preferably, the relative pressure of the negative pressure condition is 0 kPa to -100 kPa, the pressure of the steam is 0.1 MPa to 0.8 MPa, and the temperature of the steam is 60 °C to 180 °C.

9. The method for resource utilization of desulfurized waste liquid and sulfur foam according to claim 8, wherein In step (3), a salt solution with a total concentration of 40% to 60% is obtained through the concentration; And / or, in step (4), a salt solution with a total concentration of 50% to 80% is obtained through the concentration.

10. A method for treating desulfurization waste liquid and sulfur foam, characterized in that, It includes the method for resource utilization of the desulfurized waste liquid and sulfur foam as described in any one of claims 1 to 9.

Images