Three-phase separation method and device for oil-containing hazardous wastes

Abstract

The invention provides an oil-containing hazardous waste three-phase separation method and device, and relates to the technical field of hazardous waste treatment. The method comprises the following steps: sorting substances containing stones, branches and weeds in the pretreatment of the oily sludge; washing the substance with water at 70-75 DEG C, stirring and layering; generated dangerous volatile gas is discharged after being adsorbed by activated carbon, and sediment sand at the bottom is pumped out for drying treatment; the residual oil-water mixture is subjected to oil-water separation by a cyclone air flotation method The oil phase enters an oil storage tank, and the residual water phase is discharged after reducing the content of dissolved organic matters and heavy metals. According to the invention, three-phase separation of oil, sludge and water can be realized, the oil phase recovery rate is improved, the purposes of reduction and harmlessness of oil sludge treatment are realized, and related environment-friendly emission requirements can be met.

Description

Technical Field

[0001] The invention relates to the technical field of hazardous waste treatment, in particular to a three-phase separation method and device for oil-containing hazardous waste. Background Art

[0002] Oily sludge is a common hazardous waste produced by the oil industry during the mining, transportation and refining process. It belongs to the HW08 hazardous waste specified in the "National Hazardous Waste List". Oily sludge is generally denser than water, with a high oil content, generally 10%-50%, and a water content of 50%-90%. It has high viscosity and is difficult to dehydrate. It is a black, viscous semi-fluid. Oily sludge is huge in volume. If it is discharged directly without treatment, it will not only occupy a large amount of arable land, but also pollute the surrounding soil, water and air, accompanied by the generation of foul-smelling gases. The sludge contains a large number of pathogens, parasites (eggs), heavy metals such as copper, zinc, chromium, mercury, salts, and toxic and harmful substances that are difficult to degrade, such as polychlorinated biphenyls, dioxins, and radionuclides.

[0003] The treatment and disposal of oily sludge has been a major challenge in recent years, and there are few typical and mature disposal solutions and application examples. The main treatment methods currently include landfill, solvent extraction, biological method, incineration, pyrolysis, hot washing, etc. Among them, the treatment of hazardous waste landfill or direct boiler co-combustion has high requirements for landfill seepage prevention and other pollution prevention treatments, and the waste of a large amount of petroleum substances will cause certain economic losses; pyrolysis and solvent extraction methods are better for treating sludge with an oil content greater than 5%, but will incur higher economic costs; and biological methods can treat sludge with a lower oil content, but the treatment cycle is long and crude oil cannot be recovered. The hot washing method is suitable for all types of oily sludge, has strong adaptability and can recover some crude oil, but the disadvantage is that the recovery of crude oil is not complete.

[0004] Improper operation in the treatment and disposal of oily sludge will cause risks of environmental pollution. Due to the complex composition of oily sludge, it cannot be properly treated by relying on a single process. One of the development trends is to combine various processes for deep treatment of oily sludge according to actual conditions. Summary of the invention

[0005] In view of the shortcomings of the existing single process, the embodiment of the present invention provides a three-phase separation method and device for oil-containing hazardous waste, which adopts an ideal combined process mode, controls the temperature to destroy the emulsification system of oil-containing sludge to achieve three-phase separation of oil phase, water phase and solid phase, and achieves the purpose of low-cost recovery of oil phase and reduction of crude oil waste. The technical solution is as follows:

[0006] On the one hand, a method for three-phase separation of oil-containing hazardous waste is provided, the method comprising:

[0007] S1. In the pretreatment of oily sludge, materials including stones, branches and weeds are sorted;

[0008] S2, washing the material in step S1 with water at 70-75°C, stirring and then separating into layers;

[0009] S3, the dangerous volatile gas generated in step S2 is discharged after being adsorbed by activated carbon, and the sediment at the bottom is extracted and dried;

[0010] S4, separating the oil and water from the remaining oil-water mixture in step S2 by cyclone flotation;

[0011] S5. In step S4, the oil phase enters the oil storage tank, and the remaining water phase is treated to reduce the content of dissolved organic matter and heavy metals before being discharged.

[0012] Optionally, an alkaline solvent, a mixed alkali or a demulsifier is added in step S2 to accelerate demulsification; if an alkaline solvent is added, the reaction environment is adjusted to acidic in step S4.

[0013] Optionally, the solid-liquid ratio of water washing in step S2 is 1:4.

[0014] Optionally, in step S2, the stirring time is 60 min and the rotation speed is not higher than 200 r / min.

[0015] Optionally, in step S4, the flotation method is used for separation under acidic conditions, wherein separation is difficult when pH>9, and after adjusting to acidic conditions, neutralization is performed before entering the water treatment equipment.

[0016] Optionally, in step S4, when the oil and water are treated, 0.1 m 3 / m 3 Nitrogen is injected proportionally, the centrifugal acceleration is 8 to 10 times the acceleration of gravity, and the reaction time is 30s±5s.

[0017] On the other hand, a three-phase separation device for oil-containing hazardous waste is provided, which is applied to the above-mentioned three-phase separation method for oil-containing hazardous waste, and the device comprises two parts: a stirring reactor and a cyclone flotation device; the stirring reactor comprises a feed inlet, a heating water inlet, a temperature regulating device, a reactor water inlet, and a vacuum pump; the cyclone flotation device comprises a mixer, an air inlet device, an air inlet valve, a separation zone, an oil and gas zone, a water phase zone, and an oil outlet valve; the stirring reactor is connected to the cyclone flotation device through a pipeline, and the feed inlet valve controls the feed in the pipeline;

[0018] Among them, the feed port is located above the side wall of the stirred reactor, the two ends of the temperature regulating device are connected to the heating water inlet and the reactor water inlet through pipelines, the vacuum pump is located above the stirred reactor, the activated carbon adsorption device is connected to the stirred reactor through a pipeline, the bottom is the solid phase discharge port, which is connected to the heat pump drying device through a pipeline, the side wall of the stirred reactor a is the oil-water mixture discharge port, which is connected to the mixer on the side wall of the cyclone flotation device through a pipeline and a feed port valve, the air inlet valve is connected to the air inlet device and the mixer through a pipeline, the upper part of the cyclone flotation device is the oil and gas zone, the middle is the separation zone equipped with a centrifugal device, the bottom is the water phase zone, the water phase zone is provided with a water outlet, the top of the oil and gas zone is provided with an oil outlet, and the oil storage tank is connected through a pipeline, and the pipeline is equipped with an oil outlet valve and a flow meter.

[0019] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0020] The sand content in the oil phase of the oil-containing hazardous waste treated by the process of the present invention is about 3%, which can be mixed with the mined crude oil. The oil content in the mud and sand is less than 1%, the water content is between 10% and 30%, and the particle size is 3 to 50 mm of non-uniform granular sludge. The design is reasonable and practical. The oil sludge is treated by controlling the temperature and mechanical separation to reduce the energy consumption of the treatment process, and the reaction is carried out in a closed environment to adsorb and remove volatile gases. The three-phase separation of oil, mud and water is achieved; the oil phase recovery rate is improved, and the purpose of reducing and harmless oil sludge treatment is achieved, which can meet the relevant environmental protection emission requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0022] Figure 1 This is a flow chart of a three-phase separation method for oil-containing hazardous waste provided by an embodiment of the present invention;

[0023] Figure 2 It is a structural schematic diagram of a three-phase separation device for oil-containing hazardous waste provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0025] The embodiment of the present invention provides a three-phase separation method for oil-containing hazardous waste, such as Figure 1 As shown, the method comprises the following steps:

[0026] S1. In the pretreatment of oily sludge, materials including stones, branches and weeds are sorted;

[0027] S2, washing the material in step S1 with water at 70-75°C, stirring and then separating into layers;

[0028] S3, the dangerous volatile gas generated in step S2 is discharged after being adsorbed by activated carbon, and the sediment at the bottom is extracted and dried;

[0029] S4, separating the oil and water from the remaining oil-water mixture in step S2 by cyclone flotation;

[0030] S5. In step S4, the oil phase enters the oil storage tank, and the remaining water phase is treated to reduce the content of dissolved organic matter and heavy metals before being discharged.

[0031] Furthermore, in step S2, an alkaline solvent, a mixed alkali or a demulsifier is added to accelerate demulsification; if an alkaline solvent is added, the reaction environment is adjusted to be acidic in step S4.

[0032] Furthermore, in step S2, the solid-liquid ratio of water washing is 1:4, and adding too much water will increase the difficulty of water treatment.

[0033] Furthermore, in step S2, the stirring time is 60 min and the rotation speed is not higher than 200 r / min, which will accelerate emulsification.

[0034] Furthermore, in step S4, the flotation method is used for separation under acidic conditions, wherein separation is difficult when pH>9, and after adjusting to acidity, neutralization is performed before entering the water treatment equipment.

[0035] Furthermore, in step S4, when the oil and water are treated, the 3 / m 3 Nitrogen is injected in proportion, the centrifugal acceleration is 8 to 10 times the acceleration of gravity, and the reaction time is about 30 seconds, preferably, 30 seconds ± 5 seconds.

[0036] The principle of the present invention is as follows:

[0037] Through vacuum temperature control equipment and stirring equipment, the different physical properties of oil and water are used to stir the water, oil, mud and sand to fully separate them. The oil with a small specific gravity is attached to the top layer, the water with a small specific gravity is in the middle layer, and the mud with a large specific gravity settles to the bottom layer, and the oil-water mixture is further separated.

[0038] Among them, the principle of the effect of temperature on oil-mud-sand separation: petroleum contains asphalt, colloid and other components that are hydrophobic at room temperature. By raising the temperature to about 70°C, the adhesion of petroleum asphalt on the mud and sand is softened, and mechanical stirring is used to achieve dynamic viscosity reduction for oil washing.

[0039] The relationship between oil viscosity and temperature can be expressed by the Walther equation:

[0040] log[log(v+a)]=b 1+ b 2 logT

[0041] Where, v is kinematic viscosity, mm 2 ·s -1 ;

[0042] T—absolute temperature, K;

[0043] a, b 1 、b 2 —Constants related to oil properties. Different empirical equations for different oil properties have different empirical constants. Among them, the empirical constant a generally has a fixed value. The a value applicable to my country's petroleum products is generally 0.6.

[0044] In addition to temperature, within a certain pressure range, viscosity is also related to physical parameters such as density, average molecular weight and characteristic factor.

[0045] The partial flotation method of oil-water separation mainly refers to the use of highly dispersed tiny bubbles as carriers to adhere to the oil phase in the water, making its buoyancy greater than gravity and floating resistance, so that the oil and gas phase float to the water surface. The cyclone flotation oil removal device is based on the advantages of conventional flotation devices such as large processing capacity, simple operation, and high separation efficiency. It uses low-intensity cyclone centrifugal force to promote the collision and adhesion between microbubbles and oil droplets, further improving the separation performance of the flotation oil removal device. The oil-water separation process follows the Stokes formula:

[0046]

[0047] Where, g—gravitational acceleration, m / s 2 ;

[0048] d—particle size of oil droplets, m;

[0049] μ—dynamic viscosity of water, Ns / m 2 ;

[0050] ρ w —Density of water, kg / m 3 ;

[0051] ρ—density of oil droplet particles, kg / m 3 .

[0052] Accordingly, the embodiment of the present invention also provides a three-phase separation device for oil-containing hazardous waste, such as Figure 2As shown, the device includes two parts: a stirred reactor a and a cyclone flotation device b; the stirred reactor a includes a feed inlet 1, a heating water inlet 2, a temperature regulating device 3, a reactor water inlet 4, and a vacuum pump 5; the cyclone flotation device b includes a mixer 9, an air inlet device 10, an air inlet valve 11, a separation zone 12, an oil and gas zone 13, an aqueous phase zone 14, and an oil outlet valve 15; the stirred reactor a is connected to the cyclone flotation device b through a pipeline, and the feed inlet valve 8 controls the pipeline feed.

[0053] Among them, the feed inlet 1 is located above the side wall of the stirred reactor a, the two ends of the temperature regulating device 3 are connected to the heating water inlet 2 and the reactor water inlet 4 through pipelines, the vacuum pump 5 is located above the stirred reactor a, the activated carbon adsorption device 6 is connected to the stirred reactor a through a pipeline, the bottom is the solid phase discharge port, which is connected to the heat pump drying device 7 through a pipeline, the side wall of the stirred reactor a is the oil-water mixture discharge port, which is connected to the mixer 9 on the side wall of the cyclone flotation device through a pipeline and a feed inlet valve 8, the air inlet valve 11 is connected to the air inlet device 10 and the mixer 9 through a pipeline, the upper part of the cyclone flotation device b is the oil and gas zone 13, the middle is the separation zone 12 equipped with a centrifugal device, the bottom is the water phase zone 14, the water phase zone 14 is provided with a water outlet, the top of the oil and gas zone 13 is provided with an oil outlet, and the oil storage tank 17 is connected through a pipeline, and the pipeline is equipped with an oil outlet valve 15 and a flow meter 16.

[0054] The specific operation process of the device is as follows:

[0055] (1) The pre-treated sludge enters the stirring reactor a of the device, and after stirring, solid-liquid separation is achieved by utilizing the density difference between oil, mud and sand;

[0056] (2) The oil-water mixture is mixed with gas and enters the cyclone flotation device b, where the oil and water are separated by centrifugation.

[0057] The specific steps of step S1 are as follows: the pretreated sludge enters the stirring reactor a of the device from the feed port 1, water enters the temperature regulating device 3 from the heating water inlet 2, the heated water is added through the reactor water inlet 4 at a solid-liquid ratio of 1:4, and the stratified oil-water phase and solid phase are treated separately after stirring, the oil-water mixture enters the cyclone flotation device b, the solid phase is extracted from the bottom and dehydrated by the heat pump drying device 7 and then landfilled, and the volatile gas generated during stirring is adsorbed in the activated carbon adsorption device 6;

[0058] The specific steps of step S2 are as follows: the oil-water mixture and the gas (nitrogen) are mixed in a certain proportion in the mixer 9, and the fluid enters the tank tangentially along the horizontal direction of the tank outer wall, and forms a cyclone motion under the action of the spiral guide vane. The dissolved gas in the mixture and the previously injected nitrogen are released as larger bubbles, and migrate and rise toward the cyclone center with the oil, small particles of scum, etc., forming a layer of oil and scum on the water surface in the tank. Finally, the oil and gas enter the oil storage tank 17 from the top, and the water phase is discharged from the bottom, and then the organic matter and heavy metals are removed.

[0059] The calculation formulas for the oil content and water content of the sludge involved in the following examples are as follows:

[0060] The moisture content of oily sludge is calculated by measuring the moisture content in “Determination of water content of petroleum products—Distillation method” (GB / T 260-2016);

[0061]

[0062] Where W 1 is the moisture content of oil mud sand, %;

[0063] ρ is the density of water at normal temperature and pressure, g / ml;

[0064] V is the volume reading of the moisture receiver, ml;

[0065] m is the mass of the oil mud and sand initially added, g.

[0066] The sand content of oily sludge is calculated by measuring the solid content according to the "Determination of Ash Content of Petroleum Products" (GB / T508-1985);

[0067]

[0068] Where W 2 ——solid content of the sample, %;

[0069] m 1 ——weight of the crucible, g;

[0070] m 2 ——weight of crucible and sample, g;

[0071] m 3 ——The weight of the crucible and the sample after ignition, g.

[0072] Oil content of oily sludge;

[0073] W=1-W 1 -W 2

[0074] Where W is the oil content of oily mud sand, %.

[0075] Example 1

[0076] Take oily sludge from an oil field and analyze the separation effect of oily sludge. After sampling, mix the samples evenly and seal them. The oil content is 18.9% and the water content is 15.0%.

[0077] Take 25g of oily sludge, put it in a 250mL beaker, add 100g of water and stir it with a stirrer at a constant temperature of 70℃ under a fume hood for 60min; take the lower layer of sediment for component analysis; when treating oil and water, inject nitrogen at a ratio of 0.1m3 / m3 and mix it in the 9 mixer. The fluid enters the tank tangentially along the horizontal direction of the outer wall of the tank, and forms a cyclone motion under the action of the spiral guide vane in the 12 separation zone. At this time, the centrifugal acceleration is 8 to 10 times the gravity acceleration. The increase in flow rate leads to a decrease in fluid pressure. The dissolved gas and the previously injected nitrogen are released as larger bubbles, and migrate and rise toward the cyclone center with oil, small particles of scum, etc., forming a layer of oil and scum on the water surface in the tank, which is discharged through the oil and gas outlet on the top of the tank under pressure;

[0078] According to the above formula, after the initial hot water washing and mechanical demulsification of the oily sludge, the remaining solids contain 1.14g of oil, the oil content is 4.56%, and the recovered oil is 3.585g, with a recovery rate of 75.9%.

[0079] Example 2

[0080] Take the oily sludge from an oil field and analyze the separation effect of the oily sludge. After preliminary pretreatment, the water content of the sludge is calculated to be 4.26 (mL / g)%, and the oil content is 82 (w / w)%.

[0081] Take the oily sludge, add water at a solid-liquid ratio of 1:4, realize the vacuum environment of a stirred reactor through 3 vacuum pumps, and stir at 70℃ and 200r / min for 60min. The dangerous volatile gas is discharged after being adsorbed by 6 activated carbon, and the sedimented mud and sand at the bottom are extracted for drying treatment; open the 8 feed inlet valve, inject nitrogen at a ratio of 0.1m3 / m3 during oil-water treatment and mix in 9 mixer, the fluid enters the tank tangentially along the horizontal direction of the outer wall of the tank, and forms a cyclone motion under the action of the spiral guide vane in the 12 separation zone. At this time, the centrifugal acceleration is 8 to 10 times the acceleration of gravity. The increase in flow rate leads to a decrease in fluid pressure, and the dissolved gas and the previously injected nitrogen are released as larger bubbles, and migrate and rise toward the cyclone center with oil, small particles of scum, etc., forming a layer of oil and scum on the water surface in the tank, which is discharged through the oil and gas outlet on the top of the tank under pressure;

[0082] The solid phase oil content of the treated oily sludge is about 0.3%, and the water content can reach 10% after cyclic low-temperature drying, which meets the relevant treatment standards and realizes the resource utilization and harmless treatment of oily sludge.

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A three-phase separation method for oil-containing hazardous waste, characterized in that: The method comprises: S1. In the pretreatment of oily sludge, materials including stones, branches and weeds are sorted; S2, washing the material in step S1 with water at 70-75°C, stirring and then separating into layers; S3, the dangerous volatile gas generated in step S2 is discharged after being adsorbed by activated carbon, and the sediment at the bottom is extracted and dried; S4, separating the oil and water from the remaining oil-water mixture in step S2 by cyclone flotation; S5. In step S4, the oil phase enters the oil storage tank, and the remaining water phase is treated to reduce the content of dissolved organic matter and heavy metals before being discharged.

2. The method according to claim 1, characterized in that: In step S2, an alkaline solvent, a mixed alkali or a demulsifier is added to accelerate demulsification; if an alkaline solvent is added, the reaction environment is adjusted to acidic in step S4.

3. The method according to claim 1, characterized in that The solid-liquid ratio of water washing in step S2 is 1:

4.

4. The method according to claim 1, characterized in that: In step S2, the stirring time is 60 min, and the rotation speed is not higher than 200 r / min.

5. The method according to claim 1, characterized in that In step S4, the flotation method is used for separation under acidic conditions, wherein separation is difficult when pH>9, and after adjusting to acidic conditions, neutralization is performed before entering the water treatment equipment.

6. The method according to claim 1, characterized in that In step S4, when the oil and water are treated, the 3 / m 3 Nitrogen is injected proportionally, the centrifugal acceleration is 8 to 10 times the acceleration of gravity, and the reaction time is 30s±5s.

7. A three-phase separation device for oil-containing hazardous waste, used to implement the method according to any one of claims 1 to 6, characterized in that: The device comprises two parts: a stirred reactor a and a cyclone flotation device b; the stirred reactor a comprises a feed inlet (1), a heating water inlet (2), a temperature regulating device (3), a reactor water inlet (4), and a vacuum pump (5); the cyclone flotation device b comprises a mixer (9), an air inlet device (10), an air inlet valve (11), a separation zone (12), an oil and gas zone (13), an aqueous phase zone (14), and an oil outlet valve (15); the stirred reactor a is connected to the cyclone flotation device b through a pipeline, and the feed inlet valve (8) controls the feed in the pipeline; The feed inlet (1) is located above the side wall of the stirred reactor a, the two ends of the temperature regulating device (3) are connected to the heating water inlet (2) and the reactor water inlet (4) through pipelines, the vacuum pump (5) is located above the stirred reactor a, the activated carbon adsorption device (6) is connected to the stirred reactor a through a pipeline, the bottom is the solid phase discharge port, which is connected to the heat pump drying device (7) through a pipeline, the side wall of the stirred reactor a is the oil-water mixture discharge port, which is connected to the cyclone through a pipeline and a feed inlet valve (8). The air flotation device is connected to a mixer (9) on the side wall, and an air inlet valve (11) is connected to an air inlet device (10) and a mixer (9) through a pipeline. The upper part of the cyclone air flotation device b is an oil and gas zone (13), the middle is a separation zone (12) equipped with a centrifugal device, and the bottom is a water phase zone (14). The water phase zone (14) is provided with a water outlet, and the top of the oil and gas zone (13) is provided with an oil outlet. The oil storage tank (17) is connected through a pipeline, and the pipeline is equipped with an oil outlet valve (15) and a flow meter (16).

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