Device and process for harmless treatment of waste oil-based mud

Abstract

The present invention relates to the treatment of waste oil-based mud, and specifically to a device and process for harmless treatment of waste oil-based mud. The device comprises a feed grinding device, a homogenizing tank, a mortar pump, a fine grinding device, a mud intermediate storage tank, a high-pressure mud pump, a pressure control system, a heat exchanger, an auxiliary heater, a hydrothermal oxidation reactor, a centrifuge, a water storage tank and a water pump, which are sequentially connected through pipelines; the hydrothermal oxidation reactor comprises a hydrothermal section and a hydrooxidation section; the hydrothermal section and the hydrooxidation section respectively comprise at least one tubular reactor; an oxidant inlet is provided at the starting end of the hydrooxidation section; the oxidant inlet is connected to an oxidant manufacturing device through a pipeline. The device is used to treat waste oil-based mud, with low energy consumption, no need for chemical agents, no gas leakage, continuous treatment, and no secondary pollution.

Description

Technical Field

[0001] The invention relates to the technical field of harmless treatment of waste oil-based mud generated in the process of oil and gas drilling and production, and in particular to a device and process for harmless treatment of waste oil-based mud. Background Art

[0002] At present, in the process of oil and gas drilling and development, oil-based mud is widely used in deep wells, ultra-deep wells, horizontal wells and shale gas exploitation. Oil-based mud contains a large amount of mineral oil base oil, including diesel, white oil or other synthetic mineral oils. During the drilling process, as the mud circulates, a large amount of waste oil-based mud and oil-containing cuttings are generated. The single well production is about 400m 3 -800m 3 Waste oil-based mud is a mixture of drilling fluid, rock cuttings and dirty oil. It is a fairly stable colloidal suspension system that contains a large amount of chemical treatment agents, dirty oil and rock cuttings, as well as major pollutants such as petroleum, salts, and heavy metals. The organic matter comes from the base oil used to prepare the drilling fluid and various organic additives, and the main components are alkanes, polycyclic aromatic hydrocarbons, benzene series and olefins.

[0003] In 2016, my country promulgated a new "List of Hazardous Wastes", which clearly stipulates in "HW08 Waste Mineral Oil and Waste Containing Mineral Oil" that "waste drilling mud generated by drilling mud prepared with mineral oil as the continuous phase for petroleum extraction" (071-002-08) and "waste drilling mud generated by drilling mud prepared with mineral oil as the continuous phase for natural gas extraction" (072-001-08) are hazardous wastes and must be collected, stored, packaged, transported and disposed of in accordance with the hazardous waste management measures.

[0004] At present, the main treatment methods for waste oil-based drilling fluids are: pyrolysis, incineration, conventional extraction, supercritical CO2 extraction, chemical heat washing-mechanical dehydration, microbial method, etc. Among them, the pyrolysis method has high operating temperature, high heat consumption, high energy consumption, and large equipment investment. Due to the high temperature, the incineration method cannot recover expensive oil-based and main emulsion, auxiliary emulsion and other mud additives, resulting in a large waste of resources. At the same time, the flue gas emitted by combustion contains sulfides, heavy metals and dioxins, and the secondary pollution is serious. Environmental protection departments in Sichuan, Chongqing and other places have clearly stipulated that the incineration method is not allowed to treat waste oil-based mud. The extraction method has the disadvantages of high price of extractant, the need to increase the extraction agent recovery equipment, large equipment investment, and complex process control. The supercritical CO2 extraction method can only be operated intermittently and is in the laboratory research and development stage. The high temperature during the pyrolysis process will cause heavy hydrocarbons to condense and coke, resulting in large oil losses. At the same time, too high a temperature can easily destroy the performance of chemical additives in the drilling fluid, making it impossible to recycle. The biological method is difficult to biodegrade, has great environmental risks, and is time-consuming because oil-based mud contains polycyclic aromatic hydrocarbons and other difficult-to-biodegrade organic matter.

[0005] Therefore, it is urgent to develop a technically reasonable, non-secondary-pollution, economical and effective method to harmlessly treat the waste oil-based mud generated during oil and gas drilling and production, so as to meet increasingly stringent environmental protection requirements. Summary of the invention

[0006] The present invention provides a continuous waste oil-based mud harmless treatment device based on hydrothermal oxidation technology, which solves the problems of existing treatment methods that are prone to secondary pollution (such as incineration), high energy consumption (pyrolysis method, prone to gas leakage), long cycle (microbial method), inability to produce continuously (supercritical CO2 extraction), and large-scale use of chemical agents (chemical thermal washing method).

[0007] On the one hand, the present invention provides a harmless treatment device for waste oil-based mud, characterized in that it includes: a feed grinding device 1, a homogenizing tank 2, a mortar pump 3, a fine grinding device 4, a mud intermediate storage tank 5, a high-pressure mud pump 6, a pressure control system 7, a heat exchanger 8, an auxiliary heater 9, a hydrothermal oxidation reactor 10, a centrifuge 11, a water storage tank 12 and a water pump 13 connected in sequence through pipelines; the discharge port of the hydrothermal oxidation reactor 10 is connected to the hot material inlet of the heat exchanger 8, and the hot material outlet of the heat exchanger 8 is connected to the feed port of the centrifuge 11; the water outlet of the water pump 13 is connected to the water inlet of the homogenizing tank 2; the hydrothermal oxidation reactor 10 includes a hydrothermal section and a hydrooxidation section; the hydrothermal section includes at least one tubular reactor, and the water oxidation section includes at least one tubular reactor; an oxidant inlet 14 is provided at the starting end of the water oxidation section; and an oxidant manufacturing device 15 is also included; the oxidant inlet 14 is connected to the oxidant manufacturing device 15 through a pipeline.

[0008] The harmless treatment device of the present invention can be divided into a pretreatment unit (feed grinding device 1, homogenizing tank 2, mortar pump 3, fine grinding device 4), a temperature and pressure control unit (pressure control system 7, auxiliary heater 9), a hydrothermal oxidation treatment unit (hydrothermal oxidation reactor 10), an oxidant manufacturing unit (oxidant manufacturing device 15) and a heat recovery unit (heat exchanger 8). The device uses hydrothermal oxidation technology to continuously treat waste oil-based mud (drill cuttings), and its working principle is as follows:

[0009] Mud pretreatment: The solid phase of the waste oil-based mud generated after being recovered by the drilling mud recovery system is crushed and ground by the feed grinding device 1, and then enters the homogenization tank 2 to add water (which can be sewage generated during the drilling process) for homogenization. The homogenized material is transported to the fine grinding device 4 through the mortar pump 3, and the particles are further ground to be finer to obtain pretreated mud, which enters the mud intermediate storage tank 5. Then, the pretreated mud is transported to the pressure control system 7 through the high-pressure mud pump 6 to adjust the pressure.

[0010] Mud heating: At the initial start-up, the mud is heated by the auxiliary heater 9. After the operation is stable, the mud is heated by the heat exchanger 8, and the insufficient heat after heating by the heat exchanger is supplemented by the auxiliary heater 9 to obtain preheated mud.

[0011] Hydrothermal oxidation reaction: The preheated slurry enters the hydrothermal oxidation reactor 10 with a certain temperature (150-300°C) and pressure (5-20MPa). The hydrothermal oxidation reactor 10 includes two parts: a hydrothermal section and a hydrothermal oxidation section. The main functions of the hydrothermal section include: (1) dissolving organic matter on the surface of solid particles, (2) converting macromolecular organic matter into small molecular organic matter, and (3) stabilizing and solidifying heavy metals. Under the condition of adding an oxidant (preferably passing oxygen or oxygen-enriched air), the hydrothermal oxidation section oxidizes and decomposes the organic matter dissolved in the water and generates a large amount of heat.

[0012] Heat recovery: The material oxidized in the hydrothermal oxidation stage enters the heat exchanger 8, and the heat is recovered by the heat exchanger 8 and used to heat the pre-treated mud. The present invention utilizes the heat released by the hydrothermal oxidation reaction to heat the inlet material of the hydrothermal oxidation reactor 10, thereby achieving heat balance. The entire treatment device does not require additional heat sources during normal operation, thereby reducing the process operation cost.

[0013] Solid-liquid separation: After the oxidized material recovers heat through the heat exchanger 8, it enters the centrifuge 11 for solid-liquid separation. The separated water enters the water storage tank 12 and is transported to the homogenization tank 2 through the water pump 13.

[0014] The present invention adopts a hydrothermal oxidation reactor 10 for the first time to hydrothermal oxidation the pretreated oil-based mud at a relatively low temperature (120-300°C). Water at a temperature of 150-300°C and a pressure of 5-20MPa is called near-critical water or subcritical water (critical state of water: temperature greater than 374°C, pressure greater than 22MPa). Water in the near-critical state has some better properties than water at normal temperature and pressure. Its large ionization constant and small dielectric constant enable it to have acid-base catalytic function and the characteristics of dissolving organic matter. These characteristics make subcritical water not only a catalyst for organic chemical reactions, but also a reactant and solvent. In the hydrothermal pyrolysis stage, the organic matter in the oil-based mud (oil-based drill cuttings), mainly macromolecular organic matter composed of alkanes, alkylene oxides, polycyclic aromatic hydrocarbons (benzene series and their derivatives), aldehydes, etc., is converted into small molecular organic matter and dissolved in subcritical water; at the same time, some organic matter will generate organic carbon after anaerobic pyrolysis, which will remain on the surface of solid particles, thereby enhancing the stabilization and solidification of heavy metals. In the hydrothermal oxidation stage, the material after hydrothermal pyrolysis undergoes a hydrothermal oxidation reaction under the condition of adding an oxidant (for example, passing oxygen or oxygen-enriched air), converting the organic components in the material (mainly dissolved in subcritical water) into water and carbon dioxide, while releasing a large amount of heat.

[0015] In a preferred embodiment of the present invention, the tubular reactor includes a tube body 16 and a stirring device 17; a feed port and a discharge port are respectively provided at both ends of the tube body 16; the discharge port of the tubular reactor at the end of the water pyrolysis section is connected to the feed port of the tubular reactor at the starting end of the water oxidation section; the oxidant inlet 14 is arranged near the feed port of the tubular reactor at the starting end of the water oxidation section.

[0016] The hydrothermal oxidation reactor 10 can set the reaction time of the hydrothermal oxidation section and the hydrothermal oxidation section or the volume of the reactor according to the amount of material to be processed and the properties of the material. The hydrothermal oxidation section and the hydrothermal oxidation section preferably use a tubular reactor with a stirring device to enhance the heat transfer of the material in the reactor and the mass transfer effect between the material and the oxygen-enriched air, facilitate continuous operation and facilitate the use of a point-by-point oxygen supply method, thereby saving oxygen consumption.

[0017] In some embodiments of the present invention, the stirring device 17 includes a stirring shaft 18 extending into the tube body 16 , and the stirring shaft 18 is evenly provided with halved blades 19 .

[0018] In a preferred embodiment of the present invention, the water pyrolysis section includes two or more tubular reactors, and the water oxidation section includes two or more tubular reactors; the two or more tubular reactors are connected end to end through the feed port and the discharge port at both ends of the tube body 16.

[0019] In some embodiments of the present invention, the discharge port of the fine grinding device 4 is respectively connected to the mud intermediate storage tank 5 and the homogenization tank 2; the centrifuge 11 is provided with a feed port, a water outlet and a solid phase discharge port, and the water outlet of the centrifuge 11 is connected to the water storage tank 12.

[0020] In a preferred embodiment of the present invention, the heat exchanger 8 is a shell-and-tube heat exchanger; the oxidant manufacturing device 15 is an oxygen-enriched air manufacturing device. According to the characteristics that the outlet material of the hydrothermal oxidation reactor 10 contains a solid phase, heat recovery preferably adopts a shell-and-tube heat exchanger that can withstand a certain pressure and temperature. The shell-and-tube heat exchanger is a type of tubular heat exchanger, which is formed by connecting two standard tubes of different sizes to form concentric circular tubes. The outer one is called the shell side, and the inner one is called the tube side. Two different media can flow in the shell side and the tube side in reverse (or in the same direction) to achieve the effect of heat exchange. The tube side of the shell-and-tube heat exchanger is provided with a cold material inlet and a cold material outlet at both ends, and a hot material inlet and a hot material outlet at both ends of the shell side. The cold material inlet and the cold material outlet are respectively connected to the pressure control system 7 and the auxiliary heater 9; the hot material inlet and the hot material outlet are respectively connected to the hydrothermal oxidation reactor 10 and the centrifuge 11. The oxidant manufacturing device 15 preferably uses oxygen-enriched air (oxygen content of 90-95%) produced by oxygen-enriched air manufacturing equipment as the oxidant for the harmless treatment process.

[0021] In a preferred embodiment of the present invention, the harmless treatment device for waste oil-based mud is skid-mounted. Specifically, the functional components of the harmless treatment device of the present invention are integrated on an integral base, which can be installed and moved as a whole, with less on-site installation work, and only the interface pipes and external electrical connections need to be completed before it can work.

[0022] The skid-mounted continuous waste oil-based mud harmless treatment device based on hydrothermal oxidation technology of the present invention provides a clear and feasible process route for the harmless treatment of oil-based mud, and is suitable for single well or centralized station treatment and use on land and offshore drilling platforms.

[0023] The application of any of the above-mentioned devices in the harmless treatment of waste oil-based mud also falls within the protection scope of the present invention.

[0024] On the other hand, the present invention also provides a process for harmless treatment of waste oil-based mud, characterized in that the waste oil-based mud is treated by any of the above-mentioned devices, comprising the following steps:

[0025] S1. Pretreatment: recovering the solid phase of the oil-based mud, coarsely grinding the solid phase of the mud, adding water to homogenize and finely grinding to obtain pretreated mud;

[0026] S2. Heating: During initial operation, the pretreated slurry is heated by an auxiliary heater 9; after stable operation, the pretreated slurry is heated by a heat exchanger 8 to obtain a preheated slurry;

[0027] S3. Hydrothermal oxidation reaction: the preheated slurry enters the hydrothermal oxidation section of the hydrothermal oxidation reactor 10, and is pyrolyzed at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa; the pyrolysis product then enters the hydrothermal oxidation section of the hydrothermal oxidation reactor 10, and an oxidant is introduced into the hydrothermal oxidation section through the oxidant production device 15, and an oxidation reaction is carried out at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa to obtain an oxidation product;

[0028] S4. Heat recovery: The oxidation product is heated by the heat exchanger 8 for pre-treated slurry;

[0029] S5. Solid-liquid separation: The oxidation product after heat exchange enters the centrifuge 11 for solid-liquid separation, and the separated water enters the water storage tank 12 and is transported to the homogenization tank 2 through the water pump 13.

[0030] In a preferred embodiment of the present invention, in step S1, the solid phase of the mud enters the feed grinding device 1 and is ground into particles with a particle size of less than 5 mm; then enters the homogenizing tank 2, water is added to adjust the mud to a liquid content of 87-90%, and it is fully stirred; then it is transported to the fine grinding device 4 through the mortar pump 3 and further ground into particles with a particle size of less than 1 mm; a part of the finely ground mud returns to the homogenizing tank 2, and the other part enters the mud intermediate storage tank 5.

[0031] In a preferred embodiment of the present invention, in step S2, when the heat provided by the heat exchanger 8 is insufficient, the auxiliary heater 9 is used to supplement the heat to heat the pretreated mud to 250-300°C; in step S3, the pressure of the hydrothermal pyrolysis section is maintained at 10-20 MPa, and the mud is allowed to stay in the hydrothermal pyrolysis section for 30-60 minutes to obtain a pyrolysis product; the pressure of the hydrothermal oxidation section is maintained at 10-20 MPa, oxygen or oxygen-enriched air is introduced, the peroxygen coefficient is maintained at 1.2-2.0, and the pyrolysis product is allowed to stay in the hydrothermal oxidation section for 30-60 minutes to obtain an oxidation product.

[0032] The harmless treatment process of the present invention includes the steps of mud pretreatment, mud heating, hydrothermal oxidation reaction, heat recovery and solid-liquid separation. In the pretreatment stage, the solid phase produced after the oil-based mud (oil-based drill cuttings) is dried and recovered is coarsely ground, homogenized with water (preferably to obtain mud with a liquid content of 90%), and finely ground to obtain mud with fine particles (preferably a particle size of less than 1 mm). In the heating stage, during the initial startup, the pretreated mud is heated by an auxiliary heater 9; after stable operation, the pretreated mud is heated by a heat exchanger 8 to increase the mud temperature to 250-300°C to obtain preheated mud. In the hydrothermal oxidation stage, the preheated mud first enters the hydrothermal section of the hydrothermal oxidation reactor 10, dissolving the organic matter on the surface of the material particles into subcritical water (under high temperature and high pressure conditions, water is heated to above the boiling point and below the critical point, and the pressure of the system is controlled to keep the water in a liquid state, and the water in this state is called critical water) to convert the macromolecular organic matter into small molecular organic matter, while stabilizing and solidifying heavy metals; the pyrolyzed material then enters the hydrothermal oxidation section of the hydrothermal oxidation reactor 10, and the hydrothermal oxidation process converts the organic matter in the water into water and carbon dioxide under the condition of passing an oxidant (preferably oxygen or oxygen-enriched air) in the subcritical state of water, while generating a large amount of heat. The heat generated by the oxidation process is exchanged through the heat exchanger 8, so that the pretreated mud is heated to 250-300°C before entering the hydrothermal oxidation reactor 10.

[0033] Compared with the existing processing technology, the process of the present invention has the following advantages:

[0034] (1) The entire reaction is carried out in a closed reactor and the reaction medium is subcritical water, so it does not produce gas pollution like traditional incineration methods and gas leakage like traditional pyrolysis methods.

[0035] (2) The establishment of a hydrothermal decomposition stage is conducive to the rapid progress of the subsequent oxidation reaction, and can also play a role in stabilizing and solidifying heavy metals (while the traditional incineration method requires the addition of a solidifying agent).

[0036] (3) Directly recycling the large amount of heat released by the hydrothermal oxidation reaction can achieve heat balance of the entire system. After stable operation, no external heat source is required, which reduces the operating cost. The traditional pyrolysis method requires continuous heat supply (for example, fuel oil, gas or electromagnetic heating) to maintain a very high temperature (500-650℃).

[0037] (4) It uses low-temperature operation, which is generally 150-350°C. Traditional pyrolysis furnaces use high-temperature operation, which is generally 500-650°C.

[0038] (5) It can simultaneously treat the wastewater generated by the well site. The entire treatment process does not require the addition of any chemical agents, thus achieving green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : A device for harmless treatment of waste oil-based mud in a typical embodiment of the present invention;

[0040] Figure 2 : A tubular water pyrolysis oxidation reactor in a typical embodiment of the present invention;

[0041] Figure numerals: 1-feed grinding device, 2-homogenizing tank, 3-mortar pump, 4-fine grinding device, 5-mud intermediate storage tank, 6-high-pressure mud pump, 7-pressure control system, 8-heat exchanger, 9-auxiliary heater, 10-hydrothermal oxidation reactor (section A+B is hydrothermal oxidation section, section C+D is hydrothermal oxidation section), 11-centrifuge, 12-water storage tank, 13-water pump, 14-oxidant inlet, 15-oxidant manufacturing device, 16-tube body, 17-stirring device, 18-stirring shaft, 19-halved blades. DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used as explanations and illustrations of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] like Figure 1 As shown, the harmless treatment device for waste oil-based mud provided by the present invention comprises a feed grinding device 1, a homogenizing tank 2, a mortar pump 3, a fine grinding device 4, a mud intermediate storage tank 5, a high-pressure mud pump 6, a pressure control system 7, a heat exchanger 8, an auxiliary heater 9, a hydrothermal oxidation reactor 10, a centrifuge 11, a water storage tank 12 and a water pump 13 which are sequentially connected through pipelines; the discharge port of the hydrothermal oxidation reactor 10 is connected to the hot material inlet of the heat exchanger 8, and the hot material outlet of the heat exchanger 8 is connected to the feed port of the centrifuge 11; the water outlet of the water pump 13 is connected to the water inlet of the homogenizing tank 2; the hydrothermal oxidation reactor 10 comprises a hydrothermal section and a hydrooxidation section; the hydrothermal section comprises at least one tubular reactor, and the hydrooxidation section comprises at least one tubular reactor; an oxidant inlet 14 is provided at the starting end of the hydrooxidation section; and an oxidant manufacturing device 15 is also included; the oxidant inlet 14 is connected to the oxidant manufacturing device 15 through a pipeline.

[0044] In a preferred embodiment of the present invention, the tubular reactor includes a tube body 16 and a stirring device 17; a feed port and a discharge port are respectively provided at both ends of the tube body 16; the discharge port of the tubular reactor at the end of the water pyrolysis section is connected to the feed port of the tubular reactor at the starting end of the water oxidation section; the oxidant inlet 14 is arranged near the feed port of the tubular reactor at the starting end of the water oxidation section.

[0045] In some embodiments of the present invention, the stirring device 17 includes a stirring shaft 18 extending into the tube body 16 , and halved blades 19 are evenly arranged on the stirring shaft.

[0046] In some embodiments of the present invention, the water pyrolysis section includes two or more tubular reactors, and the water oxidation section includes two or more tubular reactors; the two or more tubular reactors are connected end to end through the feed port and the discharge port at both ends of the tube body 16.

[0047] In some embodiments of the present invention, the discharge port of the fine grinding device 4 is respectively connected to the mud intermediate storage tank 5 and the homogenization tank 2; the centrifuge 11 is provided with a feed port, a water outlet and a solid phase discharge port, and the water outlet of the centrifuge 11 is connected to the water storage tank 12.

[0048] In a preferred embodiment of the present invention, the heat exchanger 8 is a shell-and-tube heat exchanger; and the oxidant production device 15 is an oxygen-enriched air production device.

[0049] In a preferred embodiment of the present invention, the waste oil-based mud harmless treatment device is skid-mounted.

[0050] In some embodiments of the present invention, the harmless treatment device for waste oil-based mud includes: a feed grinding device 1, a homogenizing tank 2, a mortar pump 3, a fine grinding device 4, a mud intermediate storage tank 5, a high-pressure mud pump 6, a pressure control system 7, a heat exchanger 8, an auxiliary heater 9, a water pyrolysis oxidation reactor 10, an oxygen-enriched air manufacturing device, a centrifuge 11, a water storage tank 12 and a water pump 13. The waste oil-based mud generated by drilling and recovered by the drilling mud recovery system enters the feed grinding device 1, and the large particles or rock cuttings are crushed and ground and then enter the homogenizing tank 2, and a certain amount of water (which can be sewage generated by the drilling well site) is added for homogenization. The homogenized mud is pumped by a mortar pump 3, and after being ground again by the fine grinding device 4, part of it is circulated to the homogenizing tank 2, and part of it enters the mud intermediate storage tank 5, and then it is pressurized by the high-pressure mud pump 6 and sent to the pressure control system 7, and then heated by the heat exchanger 8 and the auxiliary heater 9, and enters the water pyrolysis oxidation reactor 10 after heating. Figure 1As shown, in the hydrothermal oxidation reactor 10, the A+B section is the hydrothermal decomposition section, the C+D section is the hydrothermal oxidation section, and the oxygen-enriched air produced by the oxygen-enriched air manufacturing device is introduced into the C+D section. The hydrothermal decomposition section (A+B) and the hydrothermal oxidation section (C+D) can be appropriately increased according to the amount of material to be processed. In the hydrothermal decomposition oxidation reactor 10, the water as the reaction medium is in a subcritical state (temperature: 120-350°C and pressure: 5-20MPa). The purpose of making the water in the hydrothermal decomposition section and the hydrothermal oxidation section in a subcritical state is to reduce corrosion to the equipment, reduce equipment cost and operating cost. The purpose of setting the hydrothermal decomposition section is to convert the macromolecular organic matter in the material into small molecular organic matter, and at the same time play a role in stabilizing and solidifying heavy metals; the purpose of setting the hydrothermal oxidation section is to quickly convert small molecular organic matter into water and carbon dioxide. The hot material that has been fully reacted in the water pyrolysis oxidation reactor 10 enters the heat exchanger 8 for heating the imported material. The material coming out of the heat exchanger 8 is separated into solid and liquid by the centrifuge 11. The separated solid phase is a common material that meets the relevant national standards. The separated water enters the water storage tank 12 and is pressurized by the water pump 13 into the homogenization tank 2 for recycling.

[0051] The harmless treatment process for waste oil-based mud provided by the present invention uses any harmless treatment device described in the present invention to treat the waste oil-based mud, comprising the following steps:

[0052] S1. Pretreatment: recovering the solid phase of the oil-based mud, coarsely grinding the solid phase of the mud, adding water to homogenize and finely grinding to obtain pretreated mud;

[0053] S2. Heating: During initial operation, the pretreated slurry is heated by an auxiliary heater 9; after stable operation, the pretreated slurry is heated by a heat exchanger 8 to obtain a preheated slurry;

[0054] S3. Hydrothermal oxidation reaction: the preheated slurry enters the hydrothermal oxidation section of the hydrothermal oxidation reactor 10, and is pyrolyzed at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa; the pyrolysis product then enters the hydrothermal oxidation section of the hydrothermal oxidation reactor 10, and an oxidant is introduced into the hydrothermal oxidation section through the oxidant production device 15, and an oxidation reaction is carried out at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa to obtain an oxidation product;

[0055] S4. Heat recovery: The oxidation product is heated by the heat exchanger 8 for pre-treated slurry;

[0056] S5. Solid-liquid separation: The oxidation product after heat exchange enters the centrifuge 11 for solid-liquid separation, and the separated water enters the water storage tank 12 and is transported to the homogenization tank 2 through the water pump 13.

[0057] In a preferred embodiment of the present invention, in step S1, the solid phase of the mud enters the feed grinding device 1 and is ground into particles with a particle size of less than 5 mm; then enters the homogenizing tank 2, water is added to adjust the mud to a liquid content of 87-90%, and it is fully stirred; then it is transported to the fine grinding device 4 through the mortar pump 3 and further ground into particles with a particle size of less than 1 mm; a part of the finely ground mud returns to the homogenizing tank 2, and the other part enters the mud intermediate storage tank 5.

[0058] In a preferred embodiment of the present invention, in step S2, when the heat provided by the heat exchanger 8 is insufficient, the auxiliary heater 9 is used to supplement the heat to heat the pretreated mud to 250-300°C; in step S3, the pressure of the hydrothermal pyrolysis section is maintained at 10-20 MPa, and the mud is allowed to stay in the hydrothermal pyrolysis section for 30-60 minutes to obtain a pyrolysis product; the pressure of the hydrothermal oxidation section is maintained at 10-20 MPa, oxygen or oxygen-enriched air is introduced, the peroxygen coefficient is maintained at 1.2-2.0, and the pyrolysis product is allowed to stay in the hydrothermal oxidation section for 30-60 minutes to obtain an oxidation product.

[0059] Application Examples :

[0060] The diesel-based oil-based mud drilling waste generated by drilling a gas field in the southwest has an oil content of 5% after the mud is recovered by the drilling mud recovery system (through a vibrating screen → a spin dryer → a centrifuge), which is much larger than the national standard (oil content <1%). The largest rock cuttings in the waste oil-based mud are about 3 to 4 cm in diameter. The waste oil-based mud harmless treatment device of the present invention is used for treatment, and the steps are as follows:

[0061] (1) Pretreatment: The above waste oil-based mud (oil-based drilling cuttings) enters the feed grinding device 1 through the feed system, grinds the material into fine particles with a particle size of less than 5 mm, and then enters the homogenizing tank 2, adds appropriate water, adjusts the liquid content of the material to about 90%, and fully stirs it; the stirred material is pressurized by the mortar pump 3 and sent to the fine grinding device 4, further grinded into particles with a particle size of less than 1 mm, and then a part of it re-enters the homogenizing tank 2, and the other part enters the mud intermediate storage tank 5. The pre-treated mud is pressurized by the high-pressure mud pump 6, so that it enters the pressure control system 7, and enters the heat exchanger 8 after the pressure is adjusted.

[0062] (2) Heating: During the initial operation, the pre-treated mud is heated by the auxiliary heater 9; after the operation is stable, the pre-treated mud is heated by the heat exchanger 8. When the heat provided by the heat exchanger 8 is insufficient, the auxiliary heater 9 is used to supplement the heat. The pre-treated mud is heated to 250-300°C.

[0063] (3) Hydrothermal oxidation reaction: The hot mud enters the hydrothermal oxidation reactor 10, and the pressure of the reactor is maintained at 10-20 MPa through the pressure control system 7; the residence time in the hydrothermal oxidation section is about 30-60 minutes. At 250°C, the dielectric constant of water is only 27, and the solubility of organic matter is greatly enhanced. In the hydrothermal oxidation section, most of the organic components in the oil-based mud are dissolved in water, and a part of the large molecular organic matter is converted into small molecular organic matter; the residence time in the hydrothermal oxidation section is 30-60 minutes, and the oxygen-enriched air produced by the oxygen-enriched air production device is introduced, and the peroxygen coefficient is 1.5. The small molecular organic components in the water undergo oxidation reaction with oxygen and are converted into water and carbon dioxide.

[0064] (4) Heat recovery: The reacted material is heat-exchanged in the heat exchanger 8 and used to heat the pre-treated mud.

[0065] (5) Solid-liquid separation: After heat exchange, the reacted material is separated into solid and liquid by a centrifuge 11. The solid phase is discharged from the solid phase discharge port of the centrifuge 11, and the water phase enters the water storage tank 12, and then is transported to the homogenization tank 2 by a water pump 13 for recycling.

[0066] The oil content of the obtained solid phase was found to be about 0.7%, meeting the national standard of less than 1%.

Claims

1. A device for harmless treatment of waste oil-based mud, characterized by: It comprises a feed grinding device (1), a homogenizing tank (2), a mortar pump (3), a fine grinding device (4), a mud intermediate storage tank (5), a high-pressure mud pump (6), a pressure control system (7), a heat exchanger (8), an auxiliary heater (9), a hydrothermal oxidation reactor (10), a centrifuge (11), a water storage tank (12) and a water pump (13) which are sequentially connected through pipelines; The discharge port of the hydrothermolysis oxidation reactor (10) is connected to the hot material inlet of the heat exchanger (8), and the hot material outlet of the heat exchanger (8) is connected to the feed port of the centrifuge (11); the water outlet of the water pump (13) is connected to the water inlet of the homogenizing tank (2); The hydrothermolysis oxidation reactor (10) comprises a hydrothermolysis section and a hydrooxidation section; the hydrothermolysis section comprises at least one tubular reactor, and the hydrooxidation section comprises at least one tubular reactor; an oxidant inlet (14) is provided at the starting end of the hydrooxidation section; the tubular reactor comprises a tube body (16) and a stirring device (17); a feed inlet and a discharge inlet are respectively provided at both ends of the tube body (16); the discharge inlet of the tubular reactor at the end of the hydrothermolysis section is connected to the feed inlet of the tubular reactor at the starting end of the hydrooxidation section; the oxidant inlet (14) is arranged near the feed inlet of the tubular reactor at the starting end of the hydrooxidation section; the stirring device (17) comprises a stirring shaft (18) extending into the tube body (16), and halved blades (19) are evenly arranged on the stirring shaft (18); It also includes an oxidant manufacturing device (15); the oxidant inlet (14) is connected to the oxidant manufacturing device (15) through a pipeline.

2. The device according to claim 1, characterized in that: The water pyrolysis section includes two or more tubular reactors, and the water oxidation section includes two or more tubular reactors; the two or more tubular reactors are connected end to end through the feed inlet and the discharge outlet at both ends of the tube body (16).

3. The device according to claim 1, characterized in that: The discharge port of the fine grinding device (4) is respectively connected to the mud intermediate storage tank (5) and the homogenization tank (2); the centrifuge (11) is provided with a feed port, a water outlet and a solid phase discharge port, and the water outlet of the centrifuge (11) is connected to the water storage tank (12).

4. The device according to claim 1, characterized in that: The heat exchanger (8) is a shell-and-tube heat exchanger; the oxidant production device (15) is an oxygen-enriched air production device.

5. The device according to any one of claims 1 to 4, characterized in that: The waste oil-based mud harmless treatment device is skid-mounted.

6. Use of the device according to any one of claims 1 to 5 in the harmless treatment of waste oil-based mud.

7. A process for harmless treatment of waste oil-based mud, characterized in that: The waste oil-based mud is treated by the device according to any one of claims 1 to 5, comprising the following steps: S1. Pretreatment: recovering the solid phase of the oil-based mud, coarsely grinding the solid phase of the mud, adding water to homogenize and finely grinding to obtain pretreated mud; S2. Heating: During initial operation, the pretreated slurry is heated by an auxiliary heater; After the operation is stable, the pretreated mud is heated by a heat exchanger to obtain preheated mud; S3. Hydrothermal oxidation reaction: the preheated slurry enters the hydrothermal oxidation section of the hydrothermal oxidation reactor and is pyrolyzed at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa; the pyrolysis product then enters the hydrothermal oxidation section of the hydrothermal oxidation reactor, an oxidant is introduced into the hydrothermal oxidation section through an oxidant manufacturing device, and an oxidation reaction is carried out at a temperature of 150 to 350° C. and a pressure of 5 to 20 MPa to obtain an oxidation product; S4. Heat recovery: The oxidation product is heated by a heat exchanger to the pretreated slurry; S5. Solid-liquid separation: The oxidation product after heat exchange enters the centrifuge for solid-liquid separation. The separated water enters the water storage tank and is transported to the homogenization tank through a water pump.

8. The process according to claim 7, characterized in that: In step S1, the solid phase of the mud enters the feed grinding device and is ground into particles with a particle size of less than 5 mm; then enters the homogenizing tank, water is added to adjust the mud to a liquid content of 87-90%, and the mud is fully stirred; then it is transported to the fine grinding device through a mortar pump and further ground into particles with a particle size of less than 1 mm; a part of the finely ground mud returns to the homogenizing tank, and the other part enters the mud intermediate storage tank.

9. The process according to claim 7 or 8, characterized in that: In step S2, when the heat provided by the heat exchanger is insufficient, an auxiliary heater is used to supplement the heat to heat the pretreated mud to 250-300° C.; In the step S3, the pressure of the hydrothermal pyrolysis section is maintained at 10-20 MPa, and the slurry is allowed to stay in the hydrothermal pyrolysis section for 30-60 minutes to obtain pyrolysis products; the pressure of the hydrothermal oxidation section is maintained at 10-20 MPa, oxygen or oxygen-enriched air is introduced, the peroxygen coefficient is maintained at 1.2-2.0, and the pyrolysis products are allowed to stay in the hydrothermal oxidation section for 30-60 minutes to obtain oxidation products.

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