Oily sludge treatment and oil phase recovery method

Abstract

The invention discloses an oily sludge treatment and oil phase recovery method which comprises the following steps: mixing oily sludge, an oxidant solution and an acid solution to obtain mixed slurry; and carrying out phase separation on the mixed slurry to respectively obtain a solid phase, a water phase and an oil phase. A small amount of oxidizing agent is added at normal temperature or in the heating acid dissolution process, a long-chain organic flocculant in the oily sludge is selectively degraded into short chains and even oxidized into carbon dioxide and water under the relatively mild condition, the adsorption bridging effect of the organic flocculant on solid phases such as colloids and suspended particles is destroyed, the wrapped solid phases efficiently react with acid, and the solid phases are separated out. Meanwhile, the surface Zeta potential of the oil phase and the solid phase can be changed, the electrostatic adsorption force of the oil phase and the solid phase is reduced, the oil phase is separated from the surface of the solid phase, and then efficient separation of the oil phase, the water phase and the solid phase is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource recovery, and in particular to a method for treating oily sludge and recovering the oil phase. Background Art

[0002] Oily wastewater is widely produced in the petroleum, chemical, steel, metallurgy and other industries. At present, the coagulation-flocculation method is usually used to treat oily wastewater in industry, that is, adding coagulants to the oily wastewater, using the generated colloidal particles to adsorb and destabilize the dissolved oil in the oily wastewater, and further adding organic flocculants. Under the adsorption and bridging effect of long molecular chains, the colloidal particles after adsorbing tiny oil droplets are flocculated into agglomerates to form larger floccules (oily sludge), thereby achieving efficient removal of the oil phase in the oily wastewater.

[0003] The oily sludge formed by the aggregation of flocs after the adsorption of oil droplets is mainly composed of oil phase, aqueous solution, organic flocculant, acid-soluble hydroxide colloid, and suspended particles such as aluminum silicate, calcium sulfate, fluoride, etc. that are insoluble or difficult to dissolve in acid. If not properly disposed of, it will cause serious pollution to the surrounding soil, water, vegetation and atmosphere. In addition, the oil phase contained in the oily sludge usually has a certain recovery value. Therefore, it is of great significance to reasonably dispose of the oily sludge and recover the oil phase therein.

[0004] The coagulation-flocculation method is used to treat oily wastewater. The active groups of the organic flocculant will adsorb and tightly combine with the active groups in the oil phase, colloids and suspended particles. The colloids and suspended particles are tightly wrapped by the organic flocculant and the oil phase to form larger flocs (oily sludge). For this type of oily sludge, the existing treatment processes mainly include the following:

[0005] (1) Solvent extraction method: It mainly uses the principle of "like dissolves like" and uses a suitable solvent as an extractant to extract and recover the oil phase from the oily sludge. It is suitable for treating oily sludge with an oil phase content of 10% to 20%. For example, liquefied dimethyl ether is used to dissolve the oil phase in the oily sludge. After liquid-solid separation, the oily dimethyl ether is evaporated at room temperature and the oil phase is recovered. Since the oil phase after the flocculation-coagulation method is adsorbed on the solid phase under the action of electrostatics, it is difficult for the extractant to separate the oil phase from the solid phase, the oil phase recovery rate is low, and the amount of residue (hazardous waste) after treatment is large. At the same time, it may also cause the extractant to be adsorbed on the solid phase, resulting in the loss of the extractant. In summary, the solvent extraction method is not suitable for the oily sludge produced by the coagulation-flocculation method.

[0006] (2) Chemical hot washing method: by adding a certain proportion of water and chemical agents (such as surfactants, alkali, etc.) to the oily sludge, under heating and stirring, the chemical agents and the oil phase are rolled up, emulsified, dissolved, and solubilized, changing the properties of the oil-water phase interface and the solid-oil phase interface in the oily sludge, and then the oil phase is eluted and peeled off from the surface of the mud and sand under the action of the fluid, and then the solid, water, and oil three-phase separation is carried out through sedimentation, centrifugation, cyclone and other processes to achieve the removal and recovery of the oil phase in the oily sludge. For example, by adding soluble carbonates or bicarbonates to heat and demulsify, the oil phase can be recovered. In addition, by adding co-solvents such as carbonates, bicarbonates or alkali solutions to the three-phase material, the water phase therein is dissolved and filtered, and then acid or extraction agent is added to the three-phase material to continue to recover the water phase and oil phase therein. However, for the oily sludge produced by the coagulation-flocculation method, since the organic flocculants and the oil phase tightly wrap the colloids and suspended particles, the oil phase and the organic flocculants, the oil phase and the colloids / suspended particles cannot be effectively separated by simply adding carbonates or bicarbonates, acids or extractants, etc., resulting in a low oil phase recovery rate.

[0007] (3) Thermal decomposition method: Based on the thermal instability of organic matter in oily sludge, the oil phase in the oily sludge is demulsified by high temperature under anaerobic conditions, and the heavy components are thermally decomposed into light components, which are then evaporated from the oily sludge in gaseous form, thereby achieving the separation of the oil phase, water phase and solid phase. For example, a heating device is used to evaporate the treated oily sludge to dry the oil phase and thermally decompose it to generate gaseous substances. However, for the oily sludge produced by the coagulation-flocculation method, since its oil phase and water phase content are both high, the valuable oil phase cannot be recycled when the thermal decomposition method is used for treatment, and the energy consumption is high. In addition, if the gaseous substances produced by the decomposition are not effectively treated, they may cause serious air pollution. Summary of the invention

[0008] The purpose of the embodiment of the present invention is to provide a method for treating oily sludge and recovering the oil phase. By adding a small amount of oxidant at room temperature or during heated acid dissolution, the long-chain organic flocculant in the oily sludge is selectively degraded into short chains under relatively mild conditions, or even oxidized into carbon dioxide and water, thereby destroying the adsorption and bridging effect of the organic flocculant on solid phases such as colloids and suspended particles, thereby achieving efficient separation and recovery of the three phases of oil, water and solid, and reducing pollution to the environment.

[0009] In order to solve the above technical problems, an embodiment of the present invention provides a method for treating oily sludge and recovering oil phase, comprising the following steps:

[0010] mixing the oily sludge, the oxidant solution and the acid solution to obtain a mixed slurry;

[0011] The mixed slurry is subjected to phase separation to obtain a solid phase, an aqueous phase and an oil phase respectively.

[0012] Furthermore, the acidic solution includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and acetic acid.

[0013] Furthermore, the hydrogen ion concentration of the acidic solution is 0.1 mol / L to 10 mol / L, preferably 0.5 mol / L to 8 mol / L.

[0014] Furthermore, the volume mass ratio of the acidic solution to the oily sludge is 1:50 to 1:5, preferably 1:20 to 1:8.

[0015] Further, the oxidant solution includes at least one of hydrogen peroxide, potassium permanganate, potassium persulfate, sodium persulfate, ammonium persulfate, hypochlorous acid, sodium hypochlorite, sodium chlorate, potassium hypochlorite, potassium chlorate, sodium perchlorate and potassium perchlorate.

[0016] Furthermore, the molar concentration of the oxidant in the mixed slurry is 0.01 mol / L to 0.2 mol / L, preferably 0.02 mol / L to 0.1 mol / L.

[0017] Furthermore, the temperature of the mixing process of the oily sludge, the oxidant solution and the acidic solution is 20°C to 90°C, preferably 50°C to 80°C.

[0018] Furthermore, the mixing time of the oily sludge, the oxidant solution and the acid solution is 0.5 h to 5 h, preferably 1 h to 3 h.

[0019] Furthermore, the method for phase separation of the mixed slurry includes at least one of static separation, filtration and centrifugal separation.

[0020] The above technical solution of the embodiment of the present invention has the following beneficial technical effects:

[0021] By adding a small amount of oxidant at room temperature or during heated acid dissolution, the long-chain organic flocculant in the oily sludge can be selectively degraded into short chains, or even oxidized into carbon dioxide and water under relatively mild conditions, thereby destroying the adsorption and bridging effect of the organic flocculant on solid phases such as colloids and suspended particles, so that the encapsulated solid phase reacts efficiently with the acid. At the same time, the surface Zeta potential of the oil phase and the solid phase can be changed, the electrostatic adsorption force between the oil phase and the solid phase can be reduced, and the oil phase can be separated from the solid phase surface, thereby achieving efficient separation of the three phases of oil, water and solid; the oil phase recovery rate is greater than 85%, and it can be recycled; the amount of oily sludge is reduced by more than 50%, achieving a significant reduction in solid waste and reducing environmental impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of specific steps of the method for treating oily sludge and recovering oil phase provided by an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the process flow of the method for treating oily sludge and recovering oil phase provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0025] Please refer to Figure 1 The embodiment of the present invention provides a method for treating oily sludge and recovering oil phase, comprising the following steps:

[0026] Step S100, mixing the oily sludge, the oxidant solution and the acid solution to obtain a mixed slurry;

[0027] Step S200, performing phase separation on the mixed slurry to obtain a solid phase, an aqueous phase and an oil phase respectively.

[0028] Among them, oily sludge is the product obtained by treating oily wastewater with the coagulation-flocculation method.

[0029] In a specific implementation of the embodiment of the present invention, optionally, the acidic solution includes: at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and acetic acid.

[0030] In the process of treating oily wastewater by coagulation-flocculation method, the colloid formed by the coagulant (such as aluminum hydroxide or iron hydroxide, etc.) adsorbs the oil phase, and then the organic flocculant adsorbs and bridges the solid phases such as colloids and suspended particles to form oily sludge, thereby achieving efficient removal of the oil phase in the wastewater. By adding an acidic solution to the oily sludge, the hydroxide colloid can be dissolved and the adsorbed oil phase can be released.

[0031] Furthermore, the hydrogen ion concentration of the acidic solution is 0.1 mol / L to 10 mol / L, preferably 0.5 mol / L to 8 mol / L.

[0032] Furthermore, the volume mass ratio of the acidic solution to the oily sludge is 1:50 to 1:5, preferably 1:20 to 1:5.

[0033] Increasing the hydrogen ion concentration and the volume mass ratio of the acidic solution to the oily sludge can promote the acid dissolution reaction of the colloid within a certain range. However, when the hydrogen ion concentration exceeds 8 mol / L and the volume mass ratio of the acidic solution to the oily sludge is higher than 1:20, increasing the hydrogen ion concentration and the amount of acid does not significantly increase the oil phase recovery rate. Therefore, based on considerations such as reducing acid consumption, the hydrogen ion concentration of the acidic solution is preferably 0.5 mol / L to 8 mol / L, and the volume mass ratio of the acidic solution to the oily sludge is preferably 1:20 to 1:8.

[0034] Further, the oxidant in the oxidant solution includes at least one of hydrogen peroxide, potassium permanganate, potassium persulfate, sodium persulfate, ammonium persulfate, hypochlorous acid, sodium hypochlorite, sodium chlorate, potassium hypochlorite, potassium chlorate, sodium perchlorate and potassium perchlorate.

[0035] In the process of treating oily wastewater by coagulation-flocculation method, the added organic flocculant will not only promote the aggregation of solid phases such as colloids and suspended particles, but also wrap the solid phases such as colloids and suspended particles, resulting in the inability of the added acid to effectively contact the colloids and other solid phases and undergo acid dissolution reaction. The addition of oxidants can selectively degrade the long-chain organic flocculants that wrap the solid phases such as colloids and suspended particles into short chains, or even oxidize them into carbon dioxide and water, destroying the adsorption and bridging effect of the organic flocculants on the solid phases such as colloids and suspended particles, so that the colloids wrapped by them react efficiently with the acid. At the same time, it can also change the surface Zeta potential of the oil phase and the solid phase, reduce the electrostatic adsorption force between the oil phase and the solid phase, and separate the oil phase from the solid phase surface, thereby achieving efficient separation of the three phases of oil, water and solid.

[0036] Furthermore, the molar concentration of the oxidant in the mixed slurry is 0.01 mol / L to 0.2 mol / L, preferably 0.02 mol / L to 0.1 mol / L. In the process of treating oily wastewater by coagulation-flocculation method, the concentration of the added organic flocculant is generally 1 mg / L to 10 mg / L, and its content in the oily sludge is only about 1%, so adding a small amount of oxidant can effectively degrade the organic flocculant.

[0037] Specifically, the temperature of the mixing process of the oily sludge, the oxidant solution and the acidic solution is 20° C. to 90° C., preferably 50° C. to 80° C. The time of the mixing process of the oily sludge, the oxidant solution and the acidic solution is 0.5 h to 5 h, preferably 1 h to 3 h.

[0038] Heating can promote the acid-dissolving reaction between acid and colloid and accelerate the oxidative degradation of organic flocculants. Increasing the temperature and extending the reaction time can accelerate the acid-dissolving and oxidative degradation reactions within a certain range. Based on actual energy consumption and processing efficiency, the preferred mixing process temperature is 50°C to 80°C and the time is 1h to 3h.

[0039] Furthermore, the method for phase separation of the mixed slurry includes at least one of static separation, filtration and centrifugal separation.

[0040] Compared with the existing oily sludge disposal technology, the technical solution of the present invention has the following advantages:

[0041] (1) Compared with the solvent extraction method, the present invention does not require the addition of an organic extractant, has a good separation effect between the oil phase and the solid phase and the water phase, has a high oil phase recovery rate, and minimizes the amount of residue, thereby avoiding the generation of a large amount of hazardous waste;

[0042] (2) Compared with the chemical hot washing method, the present invention does not need to add a demulsifier to perform the demulsification step. Under the action of the oxidant, the added acid can directly react with the oily sludge to effectively separate the oil phase from the organic flocculant, the oil phase from the colloid / suspended particles, etc., and the oil phase recovery rate is high;

[0043] (3) Compared with the thermal decomposition method, the present invention does not require the use of special thermal decomposition equipment, has mild reaction conditions, low energy consumption, and all the recovered oil phase can be reused. At the same time, the oily sludge will not decompose to produce gaseous pollutants during the treatment process, which is more environmentally friendly;

[0044] (4) Compared with other oily sludge treatment methods (biological method, mechanical centrifugal method, ultrasonic demulsification, etc.), the present invention can effectively improve the reaction efficiency between acid and solid phase by selectively oxidizing and degrading organic flocculants, and also change the surface properties and Zeta potential of both oil phase and solid phase, reduce the electrostatic adsorption force between oil phase and solid phase, and make the oil phase efficiently desorbed from the solid phase surface. The reaction conditions of the whole recovery process are relatively mild, easy to industrialize, and the amount of oxidant added is small, and the recovered oil phase can be recycled.

[0045] Below, the above technical solution is further described with three comparative examples (see Table 1 for details) and several embodiments (see Table 2, Table 3 and Table 4 for details):

[0046] Table 1

[0047]

[0048]

[0049] Below, the initial conditions of each embodiment of the technical solution of the present invention are explained: 100g of oily sludge in Table 2, wherein the organic phase content (wt.%) is 66.5, the water phase content (wt.%) is 28.7, and the solid phase content (wt.%) is 4.8; the mixed slurry is phase separated by the static phase separation method.

[0050] Table 2

[0051]

[0052]

[0053]

[0054]

[0055] Table 3 shows the results of 100 g of oily sludge with different solid and organic phase contents at different acid concentrations (H + ) is 6 mol / L, the acid dosage is 1:10, the oxidant concentration is 0.05 mol / L, the heating temperature is 80°C, the insulation time is 1.5 h, and after phase separation by static method, the organic phase recovery rate, the aqueous phase recovery rate and the solid phase reduction rate change.

[0056] Table 3

[0057]

[0058]

[0059] Table 4 shows that 100 g of oily sludge, in which the organic phase content (wt.%) is 66.5, the water phase content (wt.%) is 28.7, the solid phase content (wt.%) is 4.8, and the acid solution is H + The concentration of sulfuric acid is 6 mol / L, the acid dosage is 1:10, the concentration of hydrogen peroxide is 0.05 mol / L, and the temperature is kept at 80°C for 1.5 hours. After using different phase separation methods, the organic phase recovery rate, the aqueous phase recovery rate and the solid phase reduction rate change.

[0060] Table 4

[0061]

[0062] The embodiment of the present invention aims to protect a method for treating oily sludge and recovering oil phase, comprising the following steps: mixing oily sludge, oxidant solution and acid solution to obtain mixed slurry; performing phase separation on the mixed slurry to obtain solid phase, water phase and oil phase respectively. The above technical solution has the following effects:

[0063] By adding a small amount of oxidant at room temperature or during heated acid dissolution, the long-chain organic flocculant in the oily sludge can be selectively degraded into short chains, or even oxidized into carbon dioxide and water under relatively mild conditions, thereby destroying the adsorption and bridging effect of the organic flocculant on solid phases such as colloids and suspended particles, so that the encapsulated solid phase reacts efficiently with the acid. At the same time, the surface Zeta potential of the oil phase and the solid phase can be changed, the electrostatic adsorption force between the oil phase and the solid phase can be reduced, and the oil phase can be separated from the solid phase surface, thereby achieving efficient separation of the three phases of oil, water and solid; the oil phase recovery rate is greater than 85%, and it can be recycled; the amount of oily sludge is reduced by more than 50%, achieving a significant reduction in solid waste and reducing environmental impact.

[0064] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for treating oily sludge and recovering oil phase, It is characterized in that The steps include: mixing the oily sludge, the oxidant solution and the acid solution to obtain a mixed slurry; performing phase separation on the mixed slurry to obtain a solid phase, an aqueous phase and an oil phase respectively; The oily sludge is a product obtained by treating oily wastewater with a coagulation-flocculation method.

2. The method for treating oily sludge and recovering oil phase according to claim 1, It is characterized in that The acidic solution includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and acetic acid.

3. The method for treating oily sludge and recovering oil phase according to claim 2, It is characterized in that The hydrogen ion concentration of the acidic solution is 0.1 mol / L to 10 mol / L, preferably 0.5 mol / L to 8 mol / L.

4. The method for treating oily sludge and recovering oil phase according to claim 1, It is characterized in that The oxidant in the oxidant solution includes at least one of hydrogen peroxide, potassium permanganate, potassium persulfate, sodium persulfate, ammonium persulfate, hypochlorous acid, sodium hypochlorite, sodium chlorate, potassium hypochlorite, potassium chlorate, sodium perchlorate and potassium perchlorate.

5. The method for treating oily sludge and recovering oil phase according to claim 4, It is characterized in that The molar concentration of the oxidant in the mixed slurry is 0.01 mol / L to 0.2 mol / L, preferably 0.02 mol / L to 0.1 mol / L.

6. The method for treating oily sludge and recovering oil phase according to claim 1, It is characterized in that The volume mass ratio of the acidic solution to the oily sludge is 1:50 to 1:5, preferably 1:20 to 1:

8.

7. The method for treating oily sludge and recovering oil phase according to any one of claims 1 to 6, It is characterized in that The temperature during the mixing process of the oily sludge, the oxidant solution and the acid solution is 20°C to 90°C, preferably 50°C to 80°C.

8. The method for treating oily sludge and recovering oil phase according to claim 7, It is characterized in that The mixing time of the oily sludge, the oxidant solution and the acid solution is 0.5 h to 5 h, preferably 1 h to 3 h.

9. The method for treating oily sludge and recovering oil phase according to any one of claims 1 to 6, It is characterized in that The method for phase separation of the mixed slurry comprises at least one of static separation, filtration and centrifugal separation.

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