A superfine iron oxide powder single particle spheroidization preparation method

Abstract

The application discloses a kind of superfine iron oxide powder single particle spheroidization preparation methods, spheroidization preparation device is by preheating venturi dispersion part, high-temperature spherical furnace part, material collection part, control system composition;Preheating venturi dispersion part lower discharge and hot air feed inlet pass through hot air feed pipe (12) and connect with the top feed inlet of high-temperature spherical furnace part, the lower discharge of high-temperature spherical furnace part and cold air feed inlet pass through cold air discharge pipe (13) and connect with the feed inlet of material collection part, rotary feed valve (2) is connected with the negative pressure port of venturi pipe (3), the upper portion of high-temperature spheroidization furnace (4) is cylinder, lower portion is conical body.The application is by regulating high-temperature flame section temperature, temperature section temperature and superfine iron oxide powder single particle respectively in high-temperature flame section and temperature section time, so that superfine iron oxide powder single particle spheroidization rate keeps at 95.0% or more, with continuous operation, batch production, use safety and the like advantages.

Description

Technical Field

[0001] This invention belongs to the field of metal oxide spherical particle material preparation technology, specifically involving a method for preparing spherical ultrafine iron oxide powder single particles. The prepared ultrafine iron oxide powder has good sphericity and good flow properties, and can be widely used as a weighting material in oil and gas field development. Background Technology

[0002] In recent years, with the continuous development of HPHT (high temperature and high pressure), ERD (extended reach drilling), CTD (small borehole coiled tubing drilling), TTRD (through-tubing rotary drilling), and ultra-deep wells, the drilling process requires the use of weighting agents with characteristics such as high density, regular spherical structure, controllable particle size, non-magnetic, high acid solubility, high lubricity, low plastic viscosity, and high stability, which can be used to prepare high-density cement slurry and high-density drilling fluid.

[0003] Traditional oilfield weighting materials are mineral powders such as barite and hematite. These powders have irregular shapes and disordered particle sizes with many edges and corners. There are certain limitations on their proportion when added to drilling mud and cementing slurry. Exceeding a certain proportion results in insufficient flowability of the drilling mud or cementing slurry for field operations, and it is difficult to truly achieve close packing and particle size distribution theory to prepare high-density cement slurry. If the powder weighting material is a regular spherical shape, the proportion of weighting material added can be significantly increased, thus meeting the density requirements of drilling mud and cementing slurry for high-pressure wells and ultra-deep wells in oil and gas field development.

[0004] Currently, research on the preparation of spherical silica micropowder, spherical iron oxide, and spherical magnesium oxide powders using flame melting methods has been reported. Patent CN109095482A, entitled "A Spherical Magnesium Oxide and Its Manufacturing Method," describes melting magnesium oxide powder using a flame melting method to form spherical droplet-like melts. Oxygen and natural gas are used as the combustion gases to create a high-temperature flame. After cooling and solidification, spherical magnesium oxide is formed. The prepared spherical magnesium oxide exhibits good flowability and excellent thermal conductivity. Its magnesium oxide content is ≥85%, average particle size is 2–150 μm, sphericity is ≥0.86, water content is ≤8% wt%, and density is 3.0–3.8 g / cm³. 3 This method uses natural gas and oxygen combustion as a heat source. Theoretically, the oxygen consumption during complete combustion of natural gas is about twice its volume. For large-scale industrial production, multiple large oxygen-generating units are required. These units are expensive, and their energy consumption is 1.1–1.5 kW·h / Nm³. 3 Furthermore, the sphericity of the spherical magnesium oxide prepared by this method is less than 0.9, which is still not high. Therefore, it is necessary to find a lower-cost, easily industrially feasible flame melting spheroidization method and key equipment. Summary of the Invention

[0005] The purpose of this invention is to address the technical challenges of existing technologies, such as high equipment investment, large natural gas consumption, low flame temperature, small system processing capacity, high product energy consumption, and low sphericity rate. It provides a method for preparing single-particle sphericity of ultrafine iron oxide powder that enables continuous operation, high production efficiency, convenient operation, safe use, and high particle sphericity rate. This method uses high-pressure oxygen and natural gas to melt irregularly shaped iron oxide powder particles of 0-10 micrometers at high temperature, which can produce perfectly spherical iron oxide particles with a sphericity rate of over 95%, meeting the requirements of industries such as oil and gas field extraction for weighting materials.

[0006] To achieve the above-mentioned objectives of this invention and meet the requirements of industries such as oil and gas field extraction for weighting materials, this invention provides a method for preparing single-particle spheroidized ultrafine iron oxide powder using the following technical solution:

[0007] This invention discloses a method for preparing single-particle spheroidized ultrafine iron oxide powder. The spheroidization preparation device consists of a preheated Venturi dispersion section, a high-temperature spherical furnace section, a material collection section, and a control system. The lower discharge and hot air inlet of the preheated Venturi dispersion section are connected to the top feed port of the high-temperature spherical furnace section through a hot air feed pipe. The lower discharge and cold air inlet of the high-temperature spherical furnace section are connected to the feed port of the material collection section through a cold air discharge pipe.

[0008] The preheated Venturi dispersion section consists of an air heater, a hopper, a rotary feeder valve installed on the discharge pipe at the bottom of the hopper, and a Venturi tube. The rotary feeder valve is connected to the negative pressure port of the Venturi tube. The Venturi tube is installed below the rotary feeder valve in the hot air feed pipe. The air heater is used to heat the gas entering the Venturi tube, and the rotary feeder valve is used to uniformly feed the ultrafine iron oxide powder. Under the action of the carrier gas, the ultrafine iron oxide powder fed from the hopper to the hot air feed pipe is continuously and stably transported to the high-temperature spheroidizing furnace to meet the requirements of spheroidization of ultrafine iron oxide powder.

[0009] The high-temperature spherical furnace includes a high-temperature spheroidizing furnace, the upper part of which is a cylindrical body and the lower part is a cone. Gas burners are arranged in layers around the upper periphery of the cylindrical body. A regulating valve is installed on the discharge pipe at the lower part of the cone, and the discharge port at the lower part of the cone is connected to the upper side wall of a cold air discharge pipe. An air filter is installed at the inlet of the cold air discharge pipe. The cold air supplied into the cold air discharge pipe is used to reduce the temperature of the hot air entering the bag filter.

[0010] The material collection section includes a fan, a bag filter, and a rotary discharge valve. The upper part of the bag filter is a cylindrical body and the lower part is a cone. The fan is laterally connected to the upper cylindrical body of the bag filter. The rotary discharge valve is installed on the discharge pipe at the lower part of the cone. The fan provides negative pressure power to the bag filter.

[0011] The control system consists of an air-fuel ratio adjustment system, a temperature control system, and a pipeline pressure control system. The required temperature is set according to the process conditions, and the signal is fed back to the air-fuel ratio adjustment system. The air-fuel ratio is adjusted according to the temperature difference to obtain the required temperature. The pipeline pressure system is used to ensure that the high-temperature spheroidizing furnace is always under a slight negative pressure of 3 to 50 Pa.

[0012] The high-temperature furnace chamber within the upper periphery of the high-temperature spherical furnace section, which contains gas burners in layers, is the high-temperature flame zone. The lower cylindrical and conical sections of the high-temperature spherical furnace section are the insulation zones. The ratio of the length of the high-temperature flame zone to the length of the insulation zone is 1:

[0013] (2.5~9); The temperature of the hot air in the hot air feed pipe is controlled between 100 and 450℃, the temperature of the high-temperature flame section is controlled between 1200 and 1800℃, and the temperature of the heat preservation section is controlled between 200℃ and 1600℃; By adjusting the temperature of the high-temperature flame section, the temperature of the heat preservation section, and the time that each ultrafine iron oxide powder particle spends in the high-temperature flame section and the heat preservation section, the sphericity rate of the ultrafine iron oxide powder particle is maintained above 95.0%.

[0014] It should be noted that the air-fuel ratio here refers to the ratio of (oxygen + air) to natural gas fed into the high-temperature spheroidizing furnace. Depending on the air-fuel ratio, the temperature inside the high-temperature furnace can be adjusted from 1200℃ to 1800℃, with a maximum of 2400℃.

[0015] Furthermore, the temperature of the high-temperature flame section should be controlled between 1400 and 1600℃, and the temperature of the heat preservation section should generally be controlled between 300℃ and 1200℃, gradually decreasing from top to bottom.

[0016] Furthermore, the number of gas burners arranged in layers around the upper periphery of the cylindrical body should preferably be 30, 36, or 42, with 6 burners in each layer, and evenly distributed on the cylindrical furnace wall in 5, 6, or 7 layers to form a uniform flame band.

[0017] Furthermore, it is best to maintain a slight negative pressure of 5–40 Pa within the high-temperature spheroidizing furnace.

[0018] Furthermore, the gas burner has a double-ring structure, with the middle hole being the combustion-supporting hole and the outer ring hole being the gas hole. The combustion-supporting gas is oxygen or oxygen + air, and the gas is natural gas. The flame temperature is controlled by adjusting the ratio of the combustion-supporting gas and the gas.

[0019] As a preferred embodiment of the present invention, the length of the high-temperature flame section is generally 500-2000 mm, preferably 800-1700 mm; the length of the heat preservation section is generally 4000-5000 mm, preferably 4300-4800 mm; and the height of the lower cone of the high-temperature spheroidizing furnace is 1300-1700 mm, generally in the range of 1400-1600 mm.

[0020] As a preferred embodiment of the present invention, the Venturi fitting is made of 310S stainless steel nozzle.

[0021] As a preferred embodiment of the present invention, the inlet of the material collection section is located on the side of the lower cone of the bag filter.

[0022] As a preferred embodiment of the present invention, the number of gas burners arranged in layers around the upper periphery of the cylindrical body is 30, with 6 burners in each layer, and evenly arranged in 5 layers on the furnace wall of the cylindrical body to form a uniform flame band; the hot air temperature in the hot air feed pipe is controlled within the range of 200 to 400°C.

[0023] This invention uses high-pressure oxygen and natural gas to melt hematite at high temperature to prepare spherical iron oxide. The principle of this invention is similar to electric welding. It uses high-temperature burning and melting, rapid cooling and other methods to liquefy the surface of ultrafine iron oxide powder in a high-temperature furnace. Under the action of surface tension, it forms spherical droplets. At the same time, under the action of gravity and slight negative pressure, it passes through the cooling section to form single spherical powder particles.

[0024] The method for preparing single-particle spheroidization of ultrafine iron oxide powder according to the present invention has the following positive effects after adopting the above technical solution:

[0025] (1) The technical solution adopted in this invention is to preheat the air with an air heater to generate hot air, and introduce ultrafine iron oxide powder into the spheroidizing device in the negative pressure area formed by the Venturi tube. The hot air generated by the air heater preheats the air to make the ultrafine iron oxide powder fully dry, which not only ensures the individual dispersion of the ultrafine iron oxide powder particles, but also raises the particles to the corresponding temperature, creating conditions for high-temperature single particle spheroidization.

[0026] (2) The present invention uses a high-temperature spheroidizing furnace with 30 flame nozzles to spheroidize ultrafine iron oxide powder particles. The 30 flame nozzles can control the temperature inside the furnace and effectively prevent particles from sticking to the wall.

[0027] (3) The high-temperature spheroidizing furnace of the present invention is equipped with a high-temperature section and a heat preservation section, and finally the material is collected by negative pressure.

[0028] (4) The present invention has the advantages of continuous operation, simple structure, convenient operation and safe use.

[0029] (5) The method of the present invention optimizes the design of the ratio of the length of the high-temperature flame section to the length of the heat preservation section, the length of the high-temperature flame section, the length of the heat preservation section, and comprehensively controls the air-fuel ratio, the temperature of the high-temperature flame section, the temperature of the heat preservation section, and the time that the ultrafine iron oxide powder particles spend in the high-temperature flame section and the heat preservation section, so that the sphericity rate of the ultrafine iron oxide powder particles is maintained above 95.0%. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the spheroidization preparation device used in this invention.

[0031] The attached diagram is labeled as follows: 1-Hopper; 2-Rotary feed valve; 3-Venturi fitting; 4-High-temperature spheroidizing furnace; 5-Gas burner; 6-Regulating valve; 7-Air filter; 8-Cold air regulating valve; 9-Fan; 10-Bag collector; 11-Rotary discharge valve; 12-Hot air feed pipe; 13-Cold air discharge pipe. Detailed Implementation

[0032] To further describe the present invention, a method for preparing single-particle spheroidization of ultrafine iron oxide powder according to the present invention will be further clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Depend on Figure 1 As shown in the schematic diagram of the spheroidization preparation device used in this invention, the spheroidization preparation device of the present invention for the preparation of single particles of ultrafine iron oxide powder consists of a preheated Venturi dispersion section, a high-temperature spherical furnace section, a material collection section, and a control system. The lower discharge and hot air inlet of the preheated Venturi dispersion section are connected to the top feed port of the high-temperature spherical furnace section through a hot air feed pipe 12, and the lower discharge and cold air inlet of the high-temperature spherical furnace section are connected to the feed port of the material collection section through a cold air discharge pipe 13.

[0034] The preheated Venturi dispersion section consists of an air heater, a hopper 1, a rotary feed valve 2 installed on the lower discharge pipe of the hopper 1, and a Venturi fitting 3. The rotary feed valve 2 is connected to the negative pressure port of the Venturi fitting 3, and the Venturi fitting 3 uses a 310S stainless steel nozzle. The Venturi fitting 3 is installed below the rotary feed valve 2 inside the hot air feed pipe 12. Ultrafine iron oxide powder stored in the hopper 1 is fed into the negative pressure section of the Venturi fitting 3 via a feeding screw and the rotary feed valve 2, thus preventing dust generation. The air heater heats the air inside the hot air feed pipe 12 to 200℃~450℃. Using hot air conveying not only heats the ultrafine iron oxide powder but also effectively disperses the powder into individual particles.

[0035] The high-temperature spherical furnace includes a high-temperature spheroidizing furnace 4, which has a cylindrical upper part and a conical lower part. Gas burners 5 are arranged in layers around the upper periphery of the cylindrical body. A regulating valve 6 is provided on the discharge pipe at the lower part of the conical body, and the discharge port at the lower part of the conical body is connected to the upper side wall of the cold air discharge pipe 13. An air filter 7 is installed at the inlet of the cold air discharge pipe 13. The number of gas burners 5 arranged in layers around the upper periphery of the cylindrical body is 36, with 6 burners in each layer, and they are evenly arranged on the furnace wall of the cylindrical body in 6 layers. The high-temperature furnace chamber within the upper part of the high-temperature spherical furnace section, surrounded by layers of gas burners 5, is the high-temperature flame zone. The lower part of the high-temperature spherical furnace section, within both the cylindrical and conical sections, is the insulation zone. The flames generated by the 36 gas burners 5 ensure a uniform temperature in the high-temperature section of the furnace, forming a uniform flame band. Preheated ultrafine iron oxide powder forms droplets in this area. Under the influence of gravity and negative pressure, the droplet particles enter the lower part of the high-temperature spheroidizing furnace 4, where the temperature drops due to the action of cold air, forming spherical particles. The gas burners 5 have a double-layered annular structure, with a central hole for combustion-supporting gas and an outer annular hole for gas. The combustion-supporting gas is oxygen or oxygen + air, and the gas is natural gas. The flame temperature is controlled by adjusting the ratio of the combustion-supporting gas and the gas.

[0036] The material collection section includes a fan 9, a bag filter 10, and a rotary discharge valve 11. The upper part of the bag filter 10 is a cylindrical body, and the lower part is a cone. The fan 9 is laterally connected to the upper cylindrical body of the bag filter 10. The rotary discharge valve 11 is installed on the discharge pipe at the lower part of the cone. The inlet of the material collection section is located on the side of the lower cone of the bag filter 10.

[0037] The control system consists of an air-fuel ratio adjustment system, a temperature control system, and a pipeline pressure control system. The required temperature is set according to the process conditions, and the signal is fed back to the air-fuel ratio adjustment system. The air-fuel ratio is adjusted according to the temperature difference to obtain the required temperature. The pipeline pressure system is used to ensure that the high-temperature spheroidizing furnace 4 is always under a slight negative pressure of 3 to 50 Pa.

[0038] High-temperature spherical particles enter the bottom pipe through regulating valve 6 and are fed into bag filter 10 through cold air discharge pipe. They are then collected by bag filter 10 and the spherical particles leave the system through rotary discharge valve 11.

[0039] In this embodiment, the high-temperature flame section is approximately 1000 mm long, and the insulation section is approximately 4500 mm long. Additionally, the height of the four cones of the high-temperature spheroidizing furnace is approximately 1500 mm. The temperature of the high-temperature flame section is controlled between 1400 and 1600°C, and the temperature of the insulation section is controlled between 300 and 1200°C, gradually decreasing from top to bottom.

[0040] In practical application, the present invention discloses a method for preparing single-particle spheroidized ultrafine iron oxide powder. The ultrafine iron oxide powder, preheated by an air heater, is then uniformly fed into a high-temperature spheroidizing furnace 4 via a hot air feed pipe 12 through a preheated Venturi dispersion portion. Within the furnace 4, the preheated ultrafine iron oxide powder undergoes surface liquefaction, forming spherical droplets under surface tension. These droplets then pass through a cooling section under gravity and slight negative pressure to form single-particle spherical powder. A bag filter 10 collects the material, thus enabling safe and continuous batch production.

[0041] Practice has proven that the method for preparing single-particle spheroidization of ultrafine iron oxide powder according to this invention, using a combination of Venturi tube fittings 3 for hot air conveying, a high-temperature spheroidizing furnace 4, and 36 gas burners 5, can produce spherical iron oxide particles with a particle size of 0-10 micrometers, meeting the requirements of various industries for weighting materials. This device has been verified in practice, achieving a particle spheroidization rate of 96.2-99.3% for iron oxide, yielding unexpected technical results.

[0042] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. For those skilled in the art, it will be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing single-particle spheroidized ultrafine iron oxide powder, characterized in that: The spherical preparation device consists of a preheated Venturi dispersion section, a high-temperature spherical furnace section, a material collection section, and a control system. The lower discharge and hot air inlet of the preheated Venturi dispersion section are connected to the top feed port of the high-temperature spherical furnace section through a hot air feed pipe (12), and the lower discharge and cold air inlet of the high-temperature spherical furnace section are connected to the feed port of the material collection section through a cold air discharge pipe (13). The preheated Venturi dispersion section is composed of an air heater, a hopper (1), a rotary feed valve (2) installed on the discharge pipe at the bottom of the hopper (1), and a Venturi fitting (3). The rotary feed valve (2) is connected to the negative pressure port of the Venturi fitting (3). The Venturi fitting (3) is installed at the lower part of the rotary feed valve (2) inside the hot air feed pipe (12). The high-temperature spherical furnace includes a high-temperature spheroidizing furnace (4). The upper part of the high-temperature spheroidizing furnace (4) is a cylindrical body, and the lower part is a conical body. The high-temperature spheroidizing furnace (4) is always under a slight negative pressure of 5-40 Pa. Gas burners (5) are arranged in layers around the upper periphery of the cylindrical body. The number of gas burners (5) arranged in layers around the upper periphery of the cylindrical body is 30, 36, or 42, with 6 burners in each layer. They are evenly arranged on the furnace wall of the cylindrical body in 5, 6, or 7 layers to form a uniform flame band. The gas burner (5) described above has a double-layer annular structure. The middle hole is the combustion-supporting hole, and the outer annular hole is the gas hole. The combustion-supporting gas is oxygen or oxygen + air, and the gas is natural gas. The flame temperature is controlled by adjusting the ratio of combustion-supporting gas and gas. A regulating valve (6) is provided on the lower discharge pipe of the cone of the high-temperature spheroidizing furnace (4). The lower discharge port of the cone of the high-temperature spheroidizing furnace (4) is connected to the upper side wall of the cold air discharge pipe (13). An air filter (7) is installed at the inlet of the cold air discharge pipe (13). The material collection section includes a fan (9), a bag filter (10), and a rotary discharge valve (11). The upper part of the bag filter (10) is a cylindrical body and the lower part is a cone. The fan (9) is laterally connected to the upper cylindrical body of the bag filter (10). The rotary discharge valve (11) is installed on the discharge pipe at the lower part of the cone of the bag filter (10). High-temperature spherical particles enter the bottom pipe through the regulating valve (6) and are fed into the bag filter (10) through the cold air discharge pipe. They are then collected by the bag filter (10). The spherical particles leave the system through the rotary discharge valve (11). The control system consists of an air-fuel ratio adjustment system, a temperature control system, and a pipeline pressure control system. The required temperature is set according to the process conditions, and the signal is fed back to the air-fuel ratio adjustment system. The air-fuel ratio is adjusted according to the temperature difference to obtain the required temperature. The pipeline pressure system is used to ensure that the high-temperature spheroidizing furnace (4) is always under a slight negative pressure of 5 to 40 Pa. The high-temperature furnace chamber within the upper part of the high-temperature spherical furnace section, which is surrounded by layers of gas burners (5), is the high-temperature flame section. The lower part of the high-temperature spherical furnace section, within the cylindrical and conical bodies, is the insulation section. The length of the high-temperature flame section is 500-2000 mm, the length of the heat preservation section is 4000-5000 mm, the height of the lower cone of the high-temperature spheroidizing furnace (4) is 1300-1700 mm, and the ratio of the length of the high-temperature flame section to the length of the heat preservation section is 1:2.5-9. The temperature of the hot air in the hot air feed pipe (12) is controlled between 200-400℃, the temperature of the high-temperature flame section is controlled between 1200-1800℃, and the temperature of the heat preservation section is controlled between 200℃-1600℃, gradually decreasing from top to bottom. By adjusting the temperature of the high-temperature flame section, the temperature of the heat preservation section, and the time that each ultrafine iron oxide powder particle spends in the high-temperature flame section and the heat preservation section, the spheroidization rate of the ultrafine iron oxide powder particle is kept above 95.0%.

2. The method for preparing single-particle spheroidization of ultrafine iron oxide powder as described in claim 1, characterized in that: The temperature of the high-temperature flame section is controlled between 1400 and 1600℃, and the temperature of the heat preservation section is controlled between 300℃ and 1200℃.

3. The method for preparing single-particle spheroidization of ultrafine iron oxide powder as described in claim 2, characterized in that: The length of the high-temperature flame section is 800-1700mm, the length of the heat preservation section is 4300-4800mm, and the height of the lower cone of the high-temperature spheroidizing furnace (4) is 1400-1600mm.

4. The method for preparing single-particle spheroidization of ultrafine iron oxide powder as described in claim 3, characterized in that: The Venturi fitting (3) is made of 310S stainless steel nozzle.

5. The method for preparing single-particle spheroidization of ultrafine iron oxide powder as described in claim 4, characterized in that: The feed inlet of the material collection section is located on the side of the lower cone of the bag filter (10).

6. The method for preparing single-particle spheroidization of ultrafine iron oxide powder as described in claim 5, characterized in that: There are 30 gas burners (5) arranged in layers around the upper periphery of the cylindrical body, with 6 burners in each layer, and they are evenly arranged on the cylindrical furnace wall in 5 layers to form a uniform flame band.

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