A cascade hydrothermal catalytic oxidation treatment method for oily sludge

Abstract

This invention discloses a tiered hydrothermal catalytic oxidation treatment method for oily sludge, belonging to the field of oily sludge treatment technology. The tiered hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps: mixing oily sludge with water and performing a hydrothermal oxidation reaction to obtain mixture A; reacting mixture A under high temperature and high pressure to separate gaseous component A, oil-water mixture B, and solid component C; adding an oxidant and catalyst to solid component C and performing a supercritical catalytic oxidation reaction, followed by flash evaporation to obtain solid component D; mixing solid component D with clay, granulating, and calcining to produce fracturing proppant particles. This invention achieves tiered oil recovery and tiered volume reduction through tiered treatment of oily sludge. The treatment method is simple, systematic, and low-cost, maximizing the resource utilization rate and near-zero emissions of oily sludge, and possessing the ability to cope with numerous extreme conditions, thus having extremely high production application value.

Description

Technical Field

[0001] This invention relates to the field of oily sludge treatment technology, and in particular to a cascade hydrothermal catalytic oxidation treatment method for oily sludge. Background Technology

[0002] Currently, with the development of the petroleum industry, the amount of oily sludge produced annually is gradually increasing. Oily sludge from different sources, such as crude oil storage tank sludge, water treatment coagulation and sedimentation tank sludge, landfill sludge, oily waste pond sludge, and refinery oily sludge, has varying characteristics, mainly including aliphatic hydrocarbons, aromatic hydrocarbons, asphaltenes, and gums, with high viscosity and severe emulsification. If this oily sludge is discharged without effective treatment, it will pose a serious threat to the surrounding ecological environment and human health. Traditional oily sludge treatment methods, such as landfill, incineration, solidification, and biodegradation, have drawbacks such as low efficiency, high cost, resource waste, and environmental pollution risks, making them unsuitable for large-scale implementation.

[0003] Hydrothermal oxidation (HTO) technology is a novel method for treating oily sludge. It oxidizes and decomposes oily sludge in a hot water phase under high temperature and pressure conditions, along with air, oxygen, and other oxidants, to largely remove organic solid particles, COD, and BOD. However, its operating conditions are quite harsh, requiring consideration of engineering factors such as corrosion, salt precipitation, catalyst usage, and heat transfer. Therefore, designing a highly efficient method for treating oily sludge that can withstand extreme conditions is receiving increasing attention. Summary of the Invention

[0004] The purpose of this invention is to provide a tiered hydrothermal catalytic oxidation treatment method for oily sludge. This method is simple and low-cost, meeting industrial emission requirements while improving the resource utilization rate of oily sludge. It also possesses the ability to handle oily sludge under numerous extreme conditions, including high content of gums and asphaltenes, high emulsification, high oil content, low water and solids content, high salt content, high scaling tendency, and high corrosiveness, making it highly valuable for production applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention provides a method for the cascade hydrothermal catalytic oxidation treatment of oily sludge, comprising the following steps:

[0007] (1) Mix oily sludge with water and perform hydrothermal oxidation to obtain mixture A;

[0008] (2) Mixture A is reacted under high temperature and high pressure to separate gaseous component A, oil-water mixture B and solid component C;

[0009] (3) Add oxidant and catalyst to solid component C, carry out supercritical catalytic oxidation reaction, flash evaporate, and obtain solid component D, gas component E and liquid component F;

[0010] (4) Mix solid component D with clay, granulate, calcine, and prepare fracturing proppant particles.

[0011] Preferably, in step (1): the entire reaction stage is carried out in a hydrothermal oxidation reactor; the oily sludge is preheated to 30-70℃; the mixing is the mixing of oily sludge and water at a volume ratio of 1:2-4; the specific process of the hydrothermal oxidation reaction is to react for 15-30 minutes at 250-280℃ and 10-15 MPa.

[0012] Preferably, in step (2): the entire reaction stage is carried out in a high-temperature and high-pressure three-phase separator; the conditions for the high-temperature and high-pressure reaction are 300-360℃ and 20-30Mpa for 10-30min.

[0013] Preferably, in step (3): the entire reaction stage is carried out in a supercritical reactor; the conditions for the supercritical catalytic oxidation reaction are 380-400℃ and 25-30 MPa for 3-5 min.

[0014] Preferably, in step (4): the mixing is a mixture of solid component D and clay at a mass ratio of 1:4; the particle diameter of the granulation is 1-3 mm; and the calcination is calcined at 1000-1150℃ for 1-1.5 h.

[0015] Preferably, the oxidant is one or more of H2O2, O3 and potassium ferrate, and the amount of oxidant added is 0.1-0.5% of the mass of the solid component C.

[0016] Preferably, the catalyst is one or more of FeSO4, vitamin C and dimethylglyoxime, and the amount of catalyst added is 0.01-0.05% of the mass of the solid component C.

[0017] Preferably, the hydrothermal oxidation reactor or the supercritical reactor is equipped with a heat exchange tube made of stainless steel, and the heat exchange tube uses heat transfer oil as the reaction heat exchange medium.

[0018] The inventors discovered that fracturing proppant particles prepared from sludge at the bottom of water treatment tanks exhibit superior mechanical properties. This is likely because the solid particles in the sludge mainly consist of rock fragments from the formation and inorganic flocculants added during water treatment (primarily composed of alumina and iron oxide). These inorganic flocculants significantly contribute to the strength of the fracturing proppant.

[0019] The beneficial technical effects of the present invention are as follows:

[0020] This invention produces fracturing proppant particles by granulating the solid components generated during the reaction process, thereby improving the resource utilization rate of oily sludge. Moreover, this invention only adds clay during the granulation process, resulting in extremely low cost and a relatively simple preparation method. However, the mechanical properties of the obtained fracturing proppant particles are exceptionally good, with a compressive strength of 45-52 MPa and a breakage rate of less than 20%, fully meeting the needs of normal applications. This is mainly because this invention utilizes a stepped hydrothermal oxidation method for oily sludge, enabling the stepwise demulsification and recovery of oil components in the sludge, while simultaneously reducing the amount of oil and lowering energy consumption at each stage. Finally, under supercritical hydrothermal oxidation, organic matter in the solid residue is removed to a great extent, achieving a higher organic impurity removal rate compared to conventional one-step high-temperature supercritical hydrothermal methods. Therefore, the pores generated during calcination are smaller, thereby improving the strength of the fracturing proppant and its compatibility with the supported rock.

[0021] The oil-water mixture B obtained by the treatment method of this invention can efficiently recover petroleum hydrocarbons after demulsification, and the separated water can be used as circulating water in this system and as water for oilfield reinjection. The liquid phase F after supercritical catalytic oxidation has a COD of less than 15 mg / L, fully meeting the industrial emission standards for COD.

[0022] This invention utilizes a tiered processing approach, employing step-by-step oxidation and demulsification to achieve efficient recovery and reuse of oil, gas, and water. This reduces the amount of material requiring supercritical processing, thus avoiding energy waste caused by repeated heating of residues in oily sludge. Furthermore, the tiered processing method of this invention exhibits a strong separation effect on oil, water, and other components in oily sludge, achieving a greater degree of harmlessness. Therefore, it also shows excellent treatment results for sludge such as aged oily sludge that cannot be efficiently demulsified and oil recovered using conventional methods.

[0023] This invention also reduces heat energy waste and enables the resource utilization of products by introducing light combustible components such as methane and hydrogen generated in the supercritical catalytic oxidation reaction into the secondary combustion chamber. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0025] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0029] Example 1

[0030] The oily sludge used in the plan is the bottom mud of crude oil storage tanks at a joint station of an oilfield in northern Shaanxi: oil content 41.45%, water content 47.18%, solid content 11.37%, gum content 3.27%, and asphaltene content 2.52%.

[0031] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0032] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 70°C and then mixed with water at a volume ratio of 1:4. The mixture is then reacted at 280°C and 15 MPa for 15 min to obtain mixture A.

[0033] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 300℃ and 20MPa for 30 minutes to separate gas phase component A, oil-water mixture B and solid phase component C.

[0034] (3) Place solid component C into a supercritical reactor, add 0.5% H2O2 and 0.02% FeSO4 by mass of solid component C respectively, react at 360℃ and 30MPa for 5 min, flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0035] (4) Mix solid component D with clay at a mass ratio of 1:2 to form particles with a diameter of 3 mm, and then calcine them at 1150°C for 1 h in a secondary combustion chamber to form fracturing proppant particles.

[0036] Example 2

[0037] The oily sludge used in the plan is the bottom mud of the coagulation sedimentation tank of a joint station in an oilfield in northern Shaanxi: oil content 1.35%, water content 97.51%, solid content 1.14%; colloidal content 2.31%, asphaltene content 0.52%.

[0038] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0039] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 50°C and then mixed with water at a volume ratio of 1:2. The mixture is then reacted at 250°C and 13 MPa for 30 min to obtain mixture A.

[0040] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 320℃ and 25MPa for 25 minutes to separate gas phase component A, oil-water mixture B and solid phase component C.

[0041] (3) Place solid component C into a supercritical reactor, add 0.3% O3 and 0.03% vitamin C by mass of solid component C respectively, react at 300℃ and 26MPa for 3 min, flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0042] (4) Mix solid component D with clay at a mass ratio of 1:3 to form particles with a diameter of 1 mm, and then calcine them at 1050 °C for 1 h in a secondary combustion chamber to form fracturing proppant particles.

[0043] Example 3

[0044] The oily sludge used in the plan is the bottom mud of the oily sludge pond of a joint station of an oilfield in northern Shaanxi: oil content 4.78%, water content 92.66%, solid content 2.56%, colloidal content 2.19%, and asphaltene content 4.91%.

[0045] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0046] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 50°C and then mixed with water at a volume ratio of 1:3. The mixture is then reacted at 250°C and 13 MPa for 30 min to obtain mixture A.

[0047] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 300℃ and 20MPa for 20 minutes to separate gas phase component A, oil-water mixture B and solid phase component C.

[0048] (3) Put solid component C into a supercritical reactor, add potassium ferrate (0.2% by mass of solid component C) and dimethylglyoxime (0.05% by mass of dimethylglyoxime), react at 350℃ and 25 MPa for 5 min, and flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0049] (4) Mix solid component D with clay at a mass ratio of 1:4 to form particles with a diameter of 2 mm, and then calcine them at 1000℃ for 1.5 h in a secondary combustion chamber to form fracturing proppant particles.

[0050] Example 4

[0051] The oily sludge used in the plan is heavy oil-type oily sludge from a joint station of an oilfield in northern Shaanxi: oil content 42.35%, water content 54.68%, solid content 2.97%, colloidal content 6.19%, and asphaltene content 4.91%.

[0052] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0053] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 50°C and then mixed with water at a volume ratio of 1:2. The mixture is then reacted at 280°C and 10 MPa for 30 min to obtain mixture A.

[0054] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 330°C and 27 MPa for 25 min to separate gas phase component A, oil-water mixture B and solid phase component C.

[0055] (3) Place solid component C into a supercritical reactor, add 0.3% H2O2 and 0.05% dimethylglyoxime of solid component C respectively, react at 350℃ and 30MPa for 5 min, and flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0056] (4) Mix solid component D with clay at a mass ratio of 1:2 to form particles with a diameter of 1 mm, and then calcine them at 1150 °C for 1 h in a secondary combustion chamber to form fracturing proppant particles.

[0057] Example 5

[0058] The oily sludge used in this scheme is the same as that in Example 3.

[0059] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0060] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 50°C and then mixed with water at a volume ratio of 1:3. The mixture is then reacted at 250°C and 13 MPa for 30 min to obtain mixture A.

[0061] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 300℃ and 20MPa for 20 minutes to separate gas phase component A, oil-water mixture B and solid phase component C.

[0062] (3) Place solid component C into a supercritical reactor, add 0.2% O3 and 0.05% dimethylglyoxime of solid component C respectively, react at 350℃ and 25MPa for 5min, flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0063] Example 6

[0064] The oily sludge used in this scheme is the same as that in Example 4.

[0065] The cascade hydrothermal catalytic oxidation treatment method for oily sludge includes the following steps:

[0066] (1) In a hydrothermal oxidation reactor, the oily sludge is preheated to 50°C and then mixed with water at a volume ratio of 1:2. The mixture is then reacted at 280°C and 10 MPa for 30 min to obtain mixture A.

[0067] (2) Mixture A is placed in a high-temperature and high-pressure three-phase separator and reacted at 330°C and 27 MPa for 25 min to separate gas phase component A, oil-water mixture B and solid phase component C.

[0068] (3) Place solid component C into a supercritical reactor, add 0.3% H2O2 and 0.05% vitamin C by mass of solid component C respectively, react at 350℃ and 30MPa for 3 min, flash evaporate to obtain solid component D, gaseous component E and liquid component F.

[0069] Comparative Example 1

[0070] The oily sludge used in this scheme is the same as that in Example 4.

[0071] The specific steps are as follows:

[0072] Oily sludge is processed by a high-dryness sludge filter press to obtain an oil-water mixture and residue. The residue is then dried under normal conditions for 1 day and mixed with clay at a mass ratio of 1:2 to form 1 mm diameter particles. These particles are then calcined at 1150℃ for 1 hour to produce fracturing proppant particles.

[0073] Effect verification

[0074] (1) The compressive strength and breakage rate of the fracturing proppant particles prepared in Examples 1-4 and Comparative Example 1 were tested. The compressive strength and breakage rate were tested according to the "Recommended Methods for Performance Indicators and Tests of Fracturing Proppants" (SY / T5108-2006). The test results are shown in Table 1.

[0075] Table 1 Performance Test Table of Fracturing Proppant Particles

[0076] project Compressive strength (MPa) Breakage rate (%) Example 1 50 17 Example 2 45 8 Example 3 48 7 Example 4 52 13 Comparative Example 1 31 67

[0077] As can be seen from Table 1, in Example 4 and Comparative Example 1, by only changing steps (1) and (2), the compressive strength of the prepared fracturing proppant particles rapidly decreased from 52 MPa to 31 MPa, and the breakage rate rapidly increased from 13% to 67%. This is mainly because the present invention reduces the voids generated in the particles due to the combustion of residual oil and other organic components through the step-by-step hydrothermal oxidation purification process, thereby improving the compressive strength and reducing the breakage rate.

[0078] (2) The oil-water mixture B from Examples 1-6 and Comparative Example 1 was demulsified and separated to obtain treated water. The treated water and liquid phase component F were then tested for COD. The demulsification method was as follows: 100 ppm of demulsifier AN-266 (purchased from Hebei Anno Environmental Protection Technology Co., Ltd.) was added to the oil-water mixture B, and the mixture was stirred until the water quality became clear. The COD test conditions were the potassium dichromate digestion method. The test results are shown in Table 2.

[0079] Table 2 Solution Performance Test Table

[0080]

[0081]

[0082] As shown in Table 2, the COD of the oil-water mixture B obtained by the method of this invention after demulsification and oil-water separation is significantly lower than that of Comparative Example 1, and it can be used for circulating water in this system and oilfield reinjection water. Furthermore, the COD of the liquid phase component F after supercritical catalytic oxidation treatment is all below 15 mg / L, which meets the industrial emission requirements for COD (100-200 mg / L).

[0083] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for cascade hydrothermal catalytic oxidation treatment of oily sludge, characterized in that, The following steps are involved: (1) Mix oily sludge with water and perform hydrothermal oxidation to obtain mixture A; (2) Mixture A is reacted under high temperature and high pressure to separate gaseous component A, oil-water mixture B and solid component C; (3) Add oxidant and catalyst to solid component C, carry out supercritical catalytic oxidation reaction, flash evaporate, and obtain solid component D, gas component E and liquid component F; (4) Mix solid component D with clay, granulate, calcine, and prepare fracturing proppant particles; In step (1): the entire reaction stage is carried out in a hydrothermal oxidation reactor; the oily sludge is preheated to 30-70℃; the mixing is the mixing of oily sludge and water at a volume ratio of 1:2-4; the specific process of the hydrothermal oxidation reaction is to react at 250-280℃ and 10-15Mpa for 15-30min; In step (2): the entire reaction stage is carried out in a high-temperature and high-pressure three-phase separator; the conditions for the high-temperature and high-pressure reaction are 300-360℃ and 20-30Mpa for 10-30min. In step (3): the entire reaction stage is carried out in a supercritical reactor; the conditions for the supercritical catalytic oxidation reaction are 380-400℃ and 25-30Mpa for 3-5 min.

2. The method for cascade hydrothermal catalytic oxidation treatment of oily sludge according to claim 1, characterized in that, In step (4): the mixing is the mixing of solid component D and clay at a mass ratio of 1:4; the particle diameter of the granulation is 1-3 mm; the calcination is calcined at 1000-1150℃ for 1-1.5 h.

3. The method for cascade hydrothermal catalytic oxidation treatment of oily sludge according to claim 1, characterized in that, The oxidant is one or more of H2O2, O3 and potassium ferrate, and the amount of oxidant added is 0.1-0.5% of the mass of solid component C.

4. The method for cascade hydrothermal catalytic oxidation treatment of oily sludge according to claim 1, characterized in that, The catalyst is one or more of FeSO4, vitamin C and dimethylglyoxime, and the amount of catalyst added is 0.01-0.05% of the mass of solid component C.

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