High-sulfur wastewater treatment system and treatment process

Abstract

The invention provides a high-sulfur wastewater treatment system and process, and the process comprises the following steps: mixing high-sulfur wastewater with calcium formate, carrying out a precipitation reaction, and filtering to remove filter residues; adding methanol and primary water into the obtained filtrate to obtain slurry meeting supercritical feeding indexes; and introducing the slurry into a supercritical reaction device, and carrying out supercritical water oxidation treatment. According to the method, calcium formate and sulfate radicals in the high-sulfur wastewater are subjected to precipitation reaction, the sulfur content in the filtrate obtained after desulfurization pretreatment and precipitate filtration are performed on the high-sulfur wastewater is greatly reduced, and meanwhile, the heat value of the filtrate is higher than that of the high-sulfur wastewater, so that the heat value of the filtrate is higher in the subsequent process of performing size mixing on the filtrate to form the slurry meeting the supercritical feeding index; and the consumption of methanol and primary water is greatly reduced. Generally speaking, compared with direct supercritical water oxidation treatment on the high-sulfur wastewater, the high-sulfur wastewater treatment process provided by the invention has great advantages in the aspects of long treatment time and treatment cost.

Description

Technical Field

[0001] The present invention relates to the technical field of high-sulfur liquid hazardous waste treatment, and in particular to a high-sulfur wastewater treatment system and treatment process. Background Art

[0002] Supercritical water oxidation technology uses supercritical water as a medium to decompose organic materials into small molecules such as water and carbon dioxide using oxygen. Because supercritical water has good solubility with organic matter and gases, the oxidation reaction can occur in an oxygen-rich, homogeneous phase, eliminating the limitations of phase transfer. Furthermore, this reaction is thorough, resulting in clean, pollution-free products without the generation of harmful gases such as sulfur oxides, nitrogen oxides, and dioxins, contributing to environmental protection.

[0003] Regarding the supercritical water oxidation treatment of high-sulfur wastewater, high-sulfur liquid hazardous waste generally has the problem of too low calorific value, and in order to meet the supercritical feed sulfur requirements, the high-sulfur wastewater needs to be diluted, which leads to an increase in the volume of wastewater to be treated, and an increase in treatment time and cost; and the calorific value of the diluted wastewater to be treated is reduced, and additional reagents need to be added to increase the calorific value of the wastewater to be treated; therefore, the direct supercritical treatment of such wastewater has a low disposal volume and a high disposal cost. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present invention provides a high-sulfur wastewater treatment system and treatment process, so as to economically and efficiently perform supercritical water oxidation treatment of high-sulfur wastewater.

[0005] The specific content of the invention is as follows: In a first aspect, the present invention provides a process for treating high-sulfur wastewater, the process comprising the following steps: Step 1: mixing high-sulfur wastewater with calcium formate, performing a precipitation reaction, and filtering to remove the filter residue; Step 2: adding methanol and primary water to the obtained filtrate to obtain a slurry meeting supercritical feed specifications; Step 3: passing the slurry into a supercritical reaction device for supercritical water oxidation treatment.

[0006] Optionally, the high-sulfur wastewater has a total sulfur content of 50,000 to 60,000 mg / Kg and a calorific value of 1.5 to 2 MJ / kg.

[0007] Optionally, in step 1, the amount of calcium formate added is 10-17% of the mass of the high-sulfur wastewater.

[0008] Optionally, in step 1, the pH of the precipitation reaction is maintained at 7-8.

[0009] Optionally, in step 2, the amount of methanol added is 0.5 to 1 times the mass of the filtrate.

[0010] Optionally, in step 2, the amount of water added is 1.5 to 2 times the mass of the filtrate.

[0011] Optionally, the total sulfur content in the filtrate is 20,000 to 30,000 mg / Kg.

[0012] Optionally, the total sulfur content of the filtrate is reduced by 50-60% compared with the total sulfur content of the high-sulfur wastewater.

[0013] Optionally, the calorific value of the filtrate is increased by 30 to 50% compared with the calorific value of the high-sulfur wastewater.

[0014] In a second aspect, the present invention provides a high-sulfur wastewater treatment system, which is suitable for performing the high-sulfur wastewater treatment process described in the first aspect, comprising: a pretreatment device, a slurry preparation device, and a supercritical reaction device; wherein, The pretreatment device is used to mix high-sulfur wastewater with calcium formate, perform precipitation reaction, filter and remove filter residue, and obtain a filtrate in the wastewater with reduced sulfur content; The slurry preparation device is used to mix the filtrate, methanol and primary water to obtain a slurry that meets the supercritical feed index; The supercritical reaction device is used to perform supercritical water oxidation treatment on the slurry to obtain recycled water.

[0015] Compared with the prior art, the present invention has the following advantages: The present invention provides a high-sulfur wastewater treatment process, which includes the following steps: mixing high-sulfur wastewater with calcium formate, filtering to remove the filter residue after precipitation reaction; adding methanol and primary water to the obtained filtrate to obtain a slurry that meets the supercritical feed index; passing the slurry into a supercritical reaction device for supercritical water oxidation treatment. The present invention uses calcium formate to react with sulfate in the high-sulfur wastewater to undergo precipitation reaction to pre-desulfurize the high-sulfur wastewater. After filtering to remove the precipitate, the sulfur content in the filtrate is greatly reduced, and the calorific value of the filtrate is also higher than that of the high-sulfur wastewater. This makes it possible to greatly reduce the amount of methanol and primary water consumed in the subsequent slurrying of the filtrate to form a slurry that meets the supercritical feed index. In general, compared with directly subjecting high-sulfur wastewater to supercritical water oxidation treatment, the high-sulfur wastewater treatment process provided by the present invention has great advantages in treatment time and treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A process flow chart of high-sulfur wastewater treatment provided by an embodiment of the present invention is shown; Figure 2 The flowchart of the Jingmei wastewater treatment process in Example 3 of the present invention is shown. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product that is identical or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work fall within the scope of protection of the present invention.

[0019] Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the prior art in the art may be used. Reagents and other instruments used, for which the manufacturer is not specified, are commercially available conventional reagent products. Furthermore, the accompanying drawings are merely schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and their repeated descriptions will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0020] Technologies, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies, methods, and equipment should be considered part of the description of the present invention.

[0021] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0022] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Before describing in detail the high-sulfur wastewater treatment system and treatment process provided by the present invention, it is necessary to describe the relevant technologies as follows: Supercritical water oxidation hazardous waste treatment equipment has requirements for the sulfur, phosphorus, fluorine, and chlorine content of the liquid hazardous waste feed slurry, as well as the calorific value of the feed slurry. For high-sulfur liquid hazardous waste, dilution is required before feeding to reduce the sulfur content in the feed slurry. This dilution increases the volume of hazardous waste to be treated, which increases the treatment time and cost. Furthermore, the reduced calorific value also fails to meet the supercritical water oxidation hazardous waste treatment requirements, and additional fuel reagents are required to increase the calorific value of the hazardous waste, further increasing the disposal cost. For example, Jingmei wastewater, with an original calorific value of 1.84 MGJ / kg and a sulfur content of approximately 50,000 mg / kg, needs to be diluted 7.14 times to meet the supercritical feed sulfur requirements. That is, 1 ton becomes 7.14 tons, and the calorific value drops to 0.26 MJ / kg. An additional 2.28 tons of methanol are required to increase the calorific value.

[0024] Based on this, the present invention provides a high-sulfur wastewater treatment system and treatment process. Taking Jingmei wastewater with an original calorific value of 1.84 MGJ / kg and a sulfur content of 50,000 mg / kg as an example, the high-sulfur wastewater treatment system and treatment process provided by the present invention are applied. The sulfur is first removed to 10,000 mg / kg (the calorific value will increase to 4 MJ / kg). This approach can reduce the dilution amount by 1.43 times, that is, 1 t becomes 1.43 t, and the amount of methanol added is reduced to 0.16 t. This effectively improves the efficiency and economic value of supercritical water oxidation treatment of high-sulfur wastewater. The specific implementation method is as follows: In a first aspect, the present invention provides a high-sulfur wastewater treatment process. Figure 1 A high-sulfur wastewater treatment process flow chart provided by an embodiment of the present invention is shown as follows: Figure 1 As shown, the process includes the following steps: Step 1: mixing high-sulfur wastewater with calcium formate, performing a precipitation reaction, and filtering to remove the filter residue; Step 2: adding methanol and primary water to the obtained filtrate to obtain a slurry meeting supercritical feed specifications; Step 3: passing the slurry into a supercritical reaction device for supercritical water oxidation treatment.

[0025] Calcium formate is an organic compound with the molecular formula C2H2O4Ca. It has a molecular weight of 130 and appears as white crystals or powder. It is slightly hygroscopic and has a slightly bitter taste. It is neutral, non-toxic, and soluble in water. Its aqueous solution is neutral. The solubility of calcium formate changes little with increasing temperature, ranging from 16g / 100g water at 0°C to 18.4g / 100g water at 100°C. Its decomposition temperature is >400°C.

[0026] After dissolution, calcium formate will provide free calcium ions, which can undergo the following precipitation reaction with sulfate ions in high-sulfur wastewater, thereby achieving the removal of sulfate ions.

[0027] Ca 2+ + SO4 2- = CaSO4↓ The present invention utilizes calcium formate to react with sulfate ions in high-sulfur wastewater to produce a precipitation reaction, thereby pre-treating the high-sulfur wastewater for desulfurization. After filtering and removing the precipitate, the sulfur content in the filtrate is greatly reduced, and the calorific value of the filtrate is also higher than that of the high-sulfur wastewater. This allows the subsequent slurrying of the filtrate to form a slurry that meets the supercritical feed index, and the consumption of reagents for increasing the calorific value and the dilution multiple are greatly reduced. Overall, compared to directly subjecting high-sulfur wastewater to supercritical water oxidation treatment, the high-sulfur wastewater treatment process provided by the present invention has significant advantages in terms of treatment time and treatment cost.

[0028] For high-sulfur wastewater with a total sulfur content of 50,000 to 60,000 mg / Kg and a calorific value of 1.5 to 2 MJ / kg, the addition amount of calcium formate accounts for 10 to 17% of the mass of the high-sulfur wastewater. After precipitation reaction and filtration to remove the filter residue, the total sulfur content of the obtained filtrate is 50-60% lower than that of the high-sulfur wastewater, at 20,000 to 30,000 mg / Kg; and the calorific value of the filtrate is increased by 30 to 50% compared with the calorific value of the high-sulfur wastewater.

[0029] In the embodiment of the present invention, the sulfur content in high-sulfur liquid hazardous waste is reduced by using calcium formate, which has the advantages of high reaction efficiency, mild reaction conditions, harmless products, low cost, and wide applicability. This step can first reduce the sulfur content in high-sulfur wastewater to a lower level, while the calorific value of the high-sulfur wastewater is increased due to the introduction of methyl groups by chemical reactions; thereby reducing the consumption of reagents for dilution and calorific value enhancement in subsequent treatments.

[0030] Furthermore, methanol, a reagent to increase the calorific value, and primary water are added to the obtained filtrate for slurry adjustment. The resulting slurry that meets the supercritical feed index has a methanol addition amount of 0.5 to 1 times the mass of the filtrate; the primary water addition amount is 1.5 to 2 times the mass of the filtrate. Due to the effective reduction in the dilution ratio, the volume of wastewater used for treatment in the supercritical reaction device will be greatly reduced, which effectively saves wastewater disposal time. At the same time, since the reaction of calcium formate and sulfate is exothermic, the consumption of methanol is also effectively saved. The two promote each other and jointly optimize the treatment cost of high-sulfur liquid hazardous waste.

[0031] In a second aspect, the present invention provides a high-sulfur wastewater treatment system, comprising: a pretreatment device, a slurry preparation device and a supercritical reaction device; wherein, The pretreatment device is used to mix high-sulfur wastewater with calcium formate, perform precipitation reaction, filter and remove filter residue, and obtain a filtrate in the wastewater with reduced sulfur content; The slurry preparation device is used to mix the filtrate, methanol and primary water to obtain a slurry that meets the supercritical feed index; The supercritical reaction device is used to perform supercritical water oxidation treatment on the slurry to obtain recycled water.

[0032] The high-sulfur wastewater treatment system provided by the present invention implements all the technical solutions of the battery described in the first aspect above, and therefore has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described one by one here.

[0033] In order to enable those skilled in the art to understand the present invention more clearly, the high-sulfur wastewater treatment system and treatment process of the present invention are described in detail through the following examples.

[0034] Example 1 Take high-sulfur wastewater samples and test calorific value, pH, sulfur, chlorine, and fluorine as initial sample data; Separately, 100 mL portions of Jingmei wastewater were placed in multiple beakers and placed on a magnetic stirrer. 0 g, 10 g, 13 g, 15 g, 17 g, and 20 g of calcium formate were added to each beaker, respectively, and stirred continuously for 30 min (at a stirring speed of 180 r / min). The reaction mixture was filtered, and the filtrate was tested for calorific value, pH, and sulfur. The filtrate was dried and weighed. The test results are shown in Table 1 below: Table 1 Desulfurization effect of calcium formate on Jingmei wastewater in small-scale test

[0035] Example 2 Place a clean open ton barrel under the ton barrel agitator, add 500L of high-sulfur wastewater into it, turn on the ton barrel agitator, detect its initial temperature, and take samples to detect calorific value, pH, sulfur, chlorine, and fluorine as the initial sample; Use calcium hydroxide to adjust the pH of the initial sample to 7-8; then add 50kg, 65kg, 75kg and 85kg of calcium formate in batches and continue stirring for 30 minutes to observe whether there is heat release, hardening, etc. The reaction mixture was filtered; the filtrate was tested for calorific value, pH, sulfur, chlorine, and fluorine; the filtrate was dried and weighed; the test results are shown in Table 2 below: Table 2 Desulfurization effect of calcium formate on Jingmei wastewater in pilot test

[0036] As can be seen from Examples 1 and 2 above, a 15-17% addition ratio of calcium formate produces excellent desulfurization results. Pilot tests have shown that no significant heat release or caking occurs during the desulfurization process, and that the diaphragm pump can extract the solid-liquid mixture from the bottom layer. Example 3 See also Figure 2 The Jingmei wastewater treatment process shown in the figure is to treat 10 t of Jingmei wastewater with an original calorific value of 1.84 MGJ / kg and a sulfur content of 57950 mg / kg, and to perform supercritical water oxidation treatment. The process is as follows: (1) Pretreatment process: Jingmei wastewater and 15% calcium formate (purity 98%) were added to the pretreatment tank 1. After sufficient reaction, the wastewater was filtered and separated. The filter residue was outsourced for disposal as hazardous waste. The filtrate entered the slurry mixing tank 2. The pretreatment results are shown in Table 3. As can be seen from Table 3, after pretreatment, the calorific value increased by 47.3% and the total sulfur decreased by 56.4%.

[0037] (2) Slurry preparation process: add methanol and primary water into the slurry preparation tank 2 containing the filtrate, and prepare until the supercritical feed index is met (the feed index is a calorific value not greater than 4 MJ / kg and sulfur not higher than 7000 mg / kg). The material consumption is shown in Table 4; (3) Supercritical water oxidation treatment: The slurry is pumped into the supercritical reactor 3 for treatment.

[0038] Table 3 Changes of various indicators before and after pretreatment

[0039] Table 4 Amount of slurry materials

[0040] Comparative Example 1 Similarly, 10 tons of Jingmei wastewater with an original calorific value of 1.84 MGJ / kg and a sulfur content of 57950 mg / kg was used as the treatment object and supercritical water oxidation treatment was carried out. The process is as follows: (1) Add methanol and primary water into the slurry preparation tank containing Jingmei wastewater and mix until the supercritical feed index is met (the feed index is a calorific value of 3.9-4.1 MJ / kg and sulfur is not higher than 7000 mg / kg). The material consumption is shown in Table 5; (2) Supercritical water oxidation treatment: The slurry is pumped into a supercritical reactor for treatment.

[0041] Table 5 Amount of slurry materials

[0042] By comparing Table 4 and Table 5, it can be concluded that 10 tons of Jingmei wastewater with an original calorific value of 1.84 MGJ / kg and a sulfur content of 57,950 mg / kg needs to be diluted 8.3 times to meet the supercritical feed sulfur requirements without pretreatment, that is, 10 tons becomes 83 tons. At the same time, 20 tons of methanol needs to be added to increase the calorific value.

[0043] If the sulfur is removed to 25,000 mg / kg (the calorific value will increase to 2.71 MJ / kg), with the same feed index, the dilution amount is reduced to 3.65 times, that is, 1 ton becomes 36.5 tons, and the methanol addition amount is reduced to 7.5 tons; therefore, the pretreatment method of using calcium formate not only reduces the dilution multiple, thereby reducing the disposal time; it also reduces the consumption of auxiliary materials (methanol) and reduces the disposal cost.

[0044] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean 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 present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0045] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0046] The above is a detailed introduction to a high-sulfur wastewater treatment system and treatment process provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A high-sulfur wastewater treatment process, characterized in that: The process comprises the following steps: Step 1, mixing high-sulfur wastewater with calcium formate, and filtering to remove filter residue after precipitation reaction; Step 2, adding methanol and primary water to the obtained filtrate to obtain a slurry that meets supercritical feed indicators; Step 3: passing the slurry into a supercritical reaction device for supercritical water oxidation treatment.

2. The high-sulfur wastewater treatment process according to claim 1, characterized in that: The high-sulfur wastewater has a total sulfur content of 50,000 to 60,000 mg / Kg and a calorific value of 1.5 to 2 MJ / kg.

3. The high-sulfur wastewater treatment process according to claim 1, characterized in that: In step 1, the amount of calcium formate added is 10-17% of the mass of the high-sulfur wastewater.

4. The high-sulfur wastewater treatment process according to claim 1, characterized in that: In step 1, the pH of the precipitation reaction is maintained at 7-8.

5. The high-sulfur wastewater treatment process according to claim 1, characterized in that: In step 2, the amount of methanol added is 0.5 to 1 times the mass of the filtrate.

6. The high-sulfur wastewater treatment process according to claim 1, characterized in that: In step 2, the amount of water added once is 1.5 to 2 times the mass of the filtrate.

7. The high-sulfur wastewater treatment process according to claim 1, characterized in that: The total sulfur content in the filtrate is 20000-30000 mg / Kg.

8. The high-sulfur wastewater treatment process according to claim 1, characterized in that: The total sulfur content of the filtrate is 50-60% lower than the total sulfur content of the high-sulfur wastewater.

9. The high-sulfur wastewater treatment process according to claim 1, characterized in that: The calorific value of the filtrate is increased by 30 to 50% compared with the calorific value of the high-sulfur wastewater.

10. A high-sulfur wastewater treatment system, characterized in that: The system is suitable for executing the high-sulfur wastewater treatment process described in any one of claims 1 to 9, comprising: a pretreatment device, a slurry preparation device and a supercritical reaction device; wherein: The pretreatment device is used to mix high-sulfur wastewater with calcium formate, perform precipitation reaction, filter and remove filter residue, and obtain filtrate in wastewater with reduced sulfur content; The slurry preparation device is used to mix the filtrate, methanol and primary water to obtain slurry that meets the supercritical feed index; The supercritical reaction device is used to perform supercritical water oxidation treatment on the slurry to obtain recycled water.

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