A magnesium oxide calcining process

Abstract

The invention discloses a magnesium oxide calcining process, which adopts an automatic control system in conjunction with a mechanical arm to realize digital control according to weight, time, formula, and raw material characteristics, so that industrial primary magnesium oxide can be automatically, accurately, safely, and efficiently intelligently loaded / unloaded, and the entire production realizes an automated intelligent production line, which only requires 2-3 people to operate, and can realize continuous production with high production efficiency; the track kiln calcination adopts segmented and zoned control to realize fuzzy and accurate temperature control in each calcination area, and the combustion is sufficient and the environmental protection performance is good; in addition, the hot air and the materials carried by it in the calcination stage are partly used for preheating in the preheating section, and partly used for the magnesium carbonate production system, so as to realize recycling and reduce costs; the obtained food-grade magnesium oxide meets or exceeds the requirements of national standards. The utilization of industrial primary magnesium oxide, a process raw material, is conducive to the economical development and high-efficiency comprehensive utilization of Qinghai magnesium resources, and improves the added value of products.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium oxide calcination, and in particular to a magnesium oxide calcination process. Background Art

[0002] Magnesium oxide is an inorganic compound with the chemical formula MgO. It is an oxide of magnesium and an ionic compound. It is a white solid at room temperature. Magnesium oxide exists in nature in the form of periclase and is the raw material for magnesium smelting. Magnesium oxide has high fire-resistant and insulating properties. Usually, it can be transformed into crystals by burning at a high temperature of more than 1000°C, and it becomes dead-burned magnesium oxide (magnesia) or sintered magnesium oxide when it rises to 1500-2000°C.

[0003] Magnesium oxide calcination is usually carried out in equipment such as rotary kilns, vertical kilns, and rail kilns. These equipment can provide the required high temperature environment and ensure that the magnesium oxide is heated evenly. During the calcination process, magnesium oxide undergoes a series of physical and chemical changes. For example, the crystal structure of magnesium oxide may change, and its particle size and specific surface area may also change. In addition, calcination may also cause impurities in magnesium oxide to volatilize or decompose, thereby improving its purity. Calcinated magnesium oxide usually has a higher melting point, hardness and chemical stability. Its color may vary depending on the calcination conditions, generally white or light yellow. Calcinated magnesium oxide may also have different activity and adsorption properties, depending on its calcination temperature and time, etc.

[0004] Magnesium oxide is widely used in materials such as construction, decoration, food additives and packaging. Due to different application fields, the requirements for the physical and chemical properties of magnesium oxide are also different. Based on this, this application relies on the magnesium oxide raw materials provided by the salt lake magnesium resource processing industry to further process the low value-added magnesium oxide crude products into high-end food-grade magnesium oxide. Summary of the invention

[0005] Based on the above technical problems, the present invention uses industrial-grade magnesium oxide as raw material, adopts a new CNC orbital kiln calcination technology, and produces food-grade magnesium oxide through calcination and purification, thereby realizing high-value utilization of magnesium oxide resources. The purpose is to provide a magnesium oxide calcination process.

[0006] The present invention provides a magnesium oxide calcining process, which specifically comprises the following steps:

[0007] Step 1, automatic loading: add industrial primary magnesium oxide into the vacuum ceramic sagger, and use the automatic control system and the robotic arm to place the vacuum ceramic sagger in the track kiln;

[0008] Step 2, calcination in sections: calcining the industrial primary magnesium oxide by means of a track kiln, wherein the track kiln is divided into a preheating section, a calcination section, a heat preservation section and a cooling section for section-by-section temperature control, wherein the calcination is performed by section heating and temperature control, wherein the section heating and temperature control is divided into 10 sections, and the temperature is between 300°C and 1000°C;

[0009] Step 3, automatic unloading: unloading the cooled vacuum ceramic sagger through an automatic control system and a robotic arm;

[0010] Step 4, crushing: crush the cooled magnesium oxide in the ceramic sagger into food-grade magnesium oxide with a particle size of 150 to 350 meshes by a jet mill, and set aside;

[0011] Step 5, detection and analysis: After the above magnesium oxide is subjected to chemical composition analysis, physical property and microbiological detection, magnesium oxide ≥ 96.0%; calcium oxide ≤ 1.5%; hydrochloric acid insoluble matter ≤ 0.1%; loss on ignition ≤ 5.0%; lead ≤ 4.0%; arsenic ≤ 3.0%; bulk density of 0.7-0.9 g / ml; and food-grade magnesium oxide with the appearance of white powder is obtained.

[0012] Furthermore, the automatic control system includes a system control module and a robotic arm. The system control module includes a 3D vision technology modeling unit and an Ai artificial intelligence technology simulation calculation unit. The automatic control system is used to realize digital control based on weight, time, formula, and raw material characteristics, and realize automatic loading / unloading of raw materials.

[0013] Furthermore, the preheating section is 300-600°C, the calcining section is 600-1000°C, the insulation section temperature is 900-1000°C, and the cooling section gradually cools down to room temperature; the preheating section takes 3-4.5 hours; the calcining section takes 15-18 hours; the insulation section takes 2-3 hours; and the cooling section takes natural cooling time.

[0014] Furthermore, the temperatures of the 10 heating zones are: first zone: 300-400°C; second zone: 400-500°C; third zone: 500-600°C; fourth zone: 600-650°C; fifth zone: 650-700°C; sixth zone: 700-750°C; seventh zone: 750-800°C; eighth zone: 800-900°C; ninth zone: 900-1000°C; tenth zone: 900-1000°C.

[0015] Furthermore, the heating times of the 10 heating zones are: first zone: 1 to 1.5 h; second zone: 1 to 1.5 h; third zone: 1 to 1.5 h; fourth zone: 2.5 to 3 h; fifth zone: 2.5 to 3 h; sixth zone: 2.5 to 3 h; seventh zone: 2.5 to 3 h; eighth zone: 2.5 to 3 h; ninth zone: 2.5 to 3 h; tenth zone: 2 to 3 h.

[0016] Furthermore, the heating times for the 10 heating zones are: first zone: 1 h; second zone: 1 h; third zone: 1 h; fourth zone: 2.5 h; fifth zone: 2.5 h; sixth zone: 2.5 h; seventh zone: 2.5 h; eighth zone: 3 h; ninth zone: 3 h; tenth zone: 2 h.

[0017] Furthermore, in the preheating section of the segmented calcination, a part of the hot air from the track kiln calcination section is introduced into the preheating section for preheating through an induced draft fan, and the other part is used in the magnesium carbonate production system, thereby realizing the recovery and utilization of waste heat and the materials it carries.

[0018] The present invention also protects a system for a magnesium oxide calcining process, comprising an automatic control system, a track kiln, and an induced draft fan; the automatic control system comprises a system control module and a robotic arm, the system control module comprises a 3D visual technology modeling unit, and an Ai artificial intelligence technology simulation computing unit, the automatic control system is used to realize digital control according to weight, time, formula, and raw material characteristics, and realize automatic loading / unloading of raw materials; the inlet end of the induced draft fan is connected to the discharge port of the track kiln calcining section, the first discharge end is connected to the inlet end of the track kiln preheating section; the second discharge end is connected to the raw material inlet of the magnesium carbonate production system; the track kiln is divided into a preheating section, a calcining section, an insulation section and a cooling section, each section is connected to a natural gas pipe, and a valve is provided on the natural gas pipe for temperature control.

[0019] Furthermore, the total length of the rail kiln is 82m, the width is 2.72m, and the height is 2m, including a preheating section of 2.02m, a calcining section of 2.18m, a heat preservation section of 75.78m, and a cooling section of 2.02m.

[0020] Compared with the existing technology, the present invention has the following beneficial effects:

[0021] The method of the present invention adopts an automatic unloading system in conjunction with a mechanical arm to realize digital control according to weight, time, formula, and raw material characteristics, so that industrial primary magnesium oxide can be automatically, accurately, safely, and efficiently intelligently loaded / unloaded. The entire production realizes an automated intelligent production line, which only requires 2-3 people to operate, and can achieve continuous production with high production efficiency; the track kiln calcination adopts segmented and zoned control to achieve precise temperature control in each calcination area, sufficient combustion, and good environmental protection performance; the calcination section (static calcination) takes more than 15 hours, the temperature is uniform, and the output magnesium oxide is screened and sorted to obtain food-grade magnesium oxide; The hot air and the materials it carries in the external calcination stage are partly used for preheating in the preheating section, and partly used in the magnesium carbonate production system, which realizes recycling and reduces costs; the obtained food-grade magnesium oxide meets or exceeds the requirements of the national standard indicators of GB1886.216-2016 "National Food Safety Standard Food Additive Magnesium Oxide (including heavy and light)", magnesium oxide ≥ 96.0%; calcium oxide ≤ 1.5%; hydrochloric acid insoluble matter ≤ 0.1%; ignition loss ≤ 5.0%; lead ≤ 4.0%; arsenic ≤ 3.0%; bulk density is 0.7-0.9g / ml; appearance is white powder. The utilization of industrial primary magnesium oxide, the raw material of this process, is conducive to the economical development and high-efficiency comprehensive utilization of Qinghai magnesium resources and enhances the added value of products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A magnesium oxide calcining process specifically comprises the following steps:

[0026] (1) Automatic loading

[0027] Industrial primary magnesium oxide is added into the vacuum ceramic sagger, and the vacuum ceramic sagger is placed in the orbital kiln by using an automatic control system and a robotic arm. The ceramic sagger adopts indirect heating on the basis of traditional direct combustion to ensure the homogeneous and stable product quality, high purity, and no secondary pollution. The automatic unloading system includes a system control module and a robotic arm. The system control module includes a 3D vision technology modeling unit and an Ai artificial intelligence technology simulation calculation unit. The automatic unloading system is used to realize digital control by weight, time, formula, and raw material characteristics, and complete automatic loading of raw materials.

[0028] (2) Staged calcination

[0029] The ceramic sagger filled with industrial primary magnesium oxide is heated in sections and zones in a track kiln:

[0030] 1) Preheating section:

[0031] Zone 1: Zone 1 is also called low temperature zone. The heating temperature of this zone is 300℃ and the heating time is 1h.

[0032] The second zone: The second zone is also called the high temperature zone. The heating temperature in this zone is 400℃ and the heating time is 1h.

[0033] Zone 3: The heating temperature of this zone is 500℃ and the heating time is 1h;

[0034] 2) Calcination stage: 600-1000℃, 15h

[0035] Zone 4: The heating temperature of this zone is 600℃ and the heating time is 2.5h;

[0036] Zone 5: The heating temperature of this zone is 650℃ and the heating time is 2.5h;

[0037] Zone 6: The heating temperature of this zone is 700℃ and the heating time is 2.5h;

[0038] Zone 7: The heating temperature of this zone is 750℃ and the heating time is 2.5h;

[0039] Zone 8: The heating temperature of this zone is 800℃ and the heating time is 2.5h;

[0040] Zone 9: The heating temperature of this zone is 900℃ and the heating time is 2.5h;

[0041] 3) Insulation section:

[0042] Zone 10: The heating temperature of this zone is 900℃ and the heating time is 2h;

[0043] 4) Cooling stage: gradually cool down to room temperature, natural cooling time

[0044] (3) Automatic unloading

[0045] The cooled vacuum ceramic sagger is unloaded through an automatic control system and a robotic arm.

[0046] (4) Crushing

[0047] The magnesium oxide cooled in the ceramic sagger is ground into food-grade magnesium oxide with a particle size of 150 mesh by air jet mill.

[0048] (5) Detection and analysis

[0049] After chemical composition analysis, physical property and microbiological detection of the magnesium oxide, the obtained magnesium oxide contains 96.8% magnesium oxide, 1.38% calcium oxide, 0.08% hydrochloric acid insoluble matter, 4.40% loss on ignition, 3.4% lead, 2.3% arsenic, a bulk density of 0.7 g / ml and is a food-grade magnesium oxide with the appearance of white powder.

[0050] Example 2

[0051] A magnesium oxide calcining process specifically comprises the following steps:

[0052] (1) Automatic loading

[0053] Industrial primary magnesium oxide is added into the vacuum ceramic sagger, and the vacuum ceramic sagger is placed in the orbital kiln by using an automatic control system and a robotic arm. The ceramic sagger adopts indirect heating on the basis of traditional direct combustion to ensure the homogeneous and stable product quality, high purity, and no secondary pollution. The automatic unloading system includes a system control module and a robotic arm. The system control module includes a 3D vision technology modeling unit and an Ai artificial intelligence technology simulation calculation unit. The automatic unloading system is used to realize digital control by weight, time, formula, and raw material characteristics, and complete automatic loading of raw materials.

[0054] (2) Staged calcination

[0055] The ceramic sagger filled with industrial primary magnesium oxide is heated in sections and zones in a track kiln:

[0056] 1) Preheating section:

[0057] Zone 1: Zone 1 is also called low temperature zone. The heating temperature of this zone is 360℃ and the heating time is 2h.

[0058] The second zone: The second zone is also called the high temperature zone. The heating temperature in this zone is 450℃ and the heating time is 1h.

[0059] Zone 3: The heating temperature of this zone is 550℃ and the heating time is 1h;

[0060] 2) Calcination section:

[0061] Zone 4: The heating temperature of this zone is 630℃ and the heating time is 2.8h;

[0062] Zone 5: The heating temperature of this zone is 680℃ and the heating time is 2.8h;

[0063] Zone 6: The heating temperature of this zone is 730℃ and the heating time is 2.8h;

[0064] Zone 7: The heating temperature of this zone is 780℃ and the heating time is 2.8h;

[0065] Zone 8: The heating temperature of this zone is 880℃ and the heating time is 2.8h;

[0066] Zone 9: The heating temperature of this zone is 980℃ and the heating time is 2.8h;

[0067] 3) Insulation section:

[0068] Zone 10: The heating temperature of this zone is 950℃ and the heating time is 2.5h;

[0069] 4) Cooling stage: gradually cool down to room temperature, natural cooling time

[0070] (3) Automatic unloading

[0071] The cooled vacuum ceramic sagger is unloaded through an automatic control system and a robotic arm.

[0072] (4) Crushing

[0073] The magnesium oxide cooled in the ceramic sagger is ground into food-grade magnesium oxide with a particle size of 250 mesh by air jet mill.

[0074] (5) Detection and analysis

[0075] After chemical composition analysis, physical property and microbiological detection of the magnesium oxide, the obtained magnesium oxide contains 96.4% magnesium oxide, 1.45% calcium oxide, 0.09% hydrochloric acid insoluble matter, 4.6% loss on ignition, ≤3.5% lead, ≤2.8% arsenic, a bulk density of 0.8 g / ml and is a food-grade magnesium oxide with the appearance of white powder.

[0076] Example 3

[0077] A magnesium oxide calcining process specifically comprises the following steps:

[0078] (1) Automatic loading

[0079] Industrial primary magnesium oxide is added into the vacuum ceramic sagger, and the vacuum ceramic sagger is placed in the orbital kiln by using an automatic control system and a robotic arm. The ceramic sagger adopts indirect heating on the basis of traditional direct combustion to ensure the homogeneous and stable product quality, high purity, and no secondary pollution. The automatic unloading system includes a system control module and a robotic arm. The system control module includes a 3D vision technology modeling unit and an Ai artificial intelligence technology simulation calculation unit. The automatic unloading system is used to realize digital control by weight, time, formula, and raw material characteristics, and complete automatic loading of raw materials.

[0080] (2) Staged calcination

[0081] The ceramic sagger filled with industrial primary magnesium oxide is heated in sections and zones in a track kiln:

[0082] 1) Preheating section:

[0083] Zone 1: Zone 1 is also called low temperature zone. The heating temperature of this zone is 400℃ and the heating time is 2.5h.

[0084] The second zone: The second zone is also called the high temperature zone. The heating temperature in this zone is 500°C and the heating time is 1.5 hours.

[0085] Zone 3: The heating temperature of this zone is 600℃ and the heating time is 1h;

[0086] 2) Calcination section:

[0087] Zone 4: The heating temperature of this zone is 650℃ and the heating time is 3h;

[0088] Zone 5: The heating temperature of this zone is 700℃ and the heating time is 3h;

[0089] Zone 6: The heating temperature of this zone is 750℃ and the heating time is 3h;

[0090] Zone 7: The heating temperature of this zone is 800℃ and the heating time is 3h;

[0091] Zone 8: The heating temperature of this zone is 900℃ and the heating time is 3h;

[0092] Zone 9: The heating temperature of this zone is 1000℃ and the heating time is 3h;

[0093] 3) Insulation section:

[0094] Zone 10: The heating temperature of this zone is 1000℃ and the heating time is 3h;

[0095] 4) Cooling stage: gradually cool down to room temperature, natural cooling time

[0096] (3) Automatic unloading

[0097] The cooled vacuum ceramic sagger is unloaded through an automatic control system and a robotic arm.

[0098] (4) Crushing

[0099] The magnesium oxide cooled in the ceramic sagger is ground into food-grade magnesium oxide with a particle size of 350 meshes by air jet mill.

[0100] (5) Detection and analysis

[0101] After chemical composition analysis, physical property and microbiological detection of the magnesium oxide, the obtained magnesium oxide contains 96.3% magnesium oxide, 1.46% calcium oxide, 0.09% hydrochloric acid insoluble matter, 4.8% loss on ignition, 3.9% lead, 2.88% arsenic, a bulk density of 0.9 g / ml and is a food-grade magnesium oxide with the appearance of white powder.

[0102] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A magnesium oxide calcining process, characterized in that: The specific steps include: Step 1, automatic loading: add industrial primary magnesium oxide into the vacuum ceramic sagger, and use the automatic control system and the robotic arm to place the vacuum ceramic sagger in the track kiln; Step 2, calcination in sections: calcining the industrial primary magnesium oxide by means of a track kiln, wherein the track kiln is divided into a preheating section, a calcination section, a heat preservation section and a cooling section for section-by-section temperature control, wherein the calcination is performed by section heating and temperature control, wherein the section heating and temperature control is divided into 10 sections, and the temperature is between 300°C and 1000°C; Step 3, automatic unloading: unloading the cooled vacuum ceramic sagger through an automatic control system and a robotic arm; Step 4, crushing: crush the cooled magnesium oxide in the ceramic sagger into food-grade magnesium oxide with a particle size of 150 to 350 meshes by air jet mill, and set aside; Step 5, detection and analysis: After the above magnesium oxide is subjected to chemical composition analysis, physical property and microbiological detection, magnesium oxide ≥ 96.0%; calcium oxide ≤ 1.5%; hydrochloric acid insoluble matter ≤ 0.1%; loss on ignition ≤ 5.0%; lead ≤ 4.0%; arsenic ≤ 3.0%; bulk density of 0.7-0.9 g / ml; and food-grade magnesium oxide with the appearance of white powder is obtained.

2. A magnesium oxide calcining process according to claim 1, characterized in that: The automatic control system includes a system control module and a robotic arm. The system control module includes a 3D vision technology modeling unit and an Ai artificial intelligence technology simulation calculation unit. The automatic control system is used to realize digital control based on weight, time, formula, and raw material characteristics, and realize automatic loading / unloading of raw materials.

3. A magnesium oxide calcining process according to claim 1, characterized in that: The preheating section is 300-600°C, the calcining section is 600-1000°C, the insulation section is 900-1000°C, and the cooling section gradually cools down to room temperature; the preheating section takes 3-4.5 hours; the calcining section takes 15-18 hours; the insulation section takes 2-3 hours; and the cooling section takes natural cooling time.

4. A magnesium oxide calcining process according to claim 1, characterized in that: The temperatures of the 10 heating zones are: first zone: 300-400°C; Second zone: 400~500℃; The third zone is 500-600℃; the fourth zone is 600-650℃; the fifth zone is 650-700℃; the sixth zone is 700-750℃; the seventh zone is 750-800℃; the eighth zone is 800-900℃; the ninth zone is 900-1000℃; the tenth zone is 900-1000℃.

5. A magnesium oxide calcining process according to claim 1, characterized in that: The heating times of the 10 heating zones are: first zone: 1 to 1.5 hours; second zone: 1 to 1.5 hours; third zone: 1 to 1.5 hours; fourth zone: 2.5 to 3 hours; fifth zone: 2.5 to 3 hours; sixth zone: 2.5 to 3 hours; seventh zone: 2.5 to 3 hours; eighth zone: 2.5 to 3 hours; ninth zone: 2.5 to 3 hours; tenth zone: 2 to 3 hours.

6. A magnesium oxide calcining process according to claim 5, characterized in that: The heating times of the 10 heating zones are: first zone: 1 hour; second zone: 1 hour; third zone: 1 hour; fourth zone: 2.5 hours; fifth zone: 2.5 hours; sixth zone: 2.5 hours; seventh zone: 2.5 hours; eighth zone: 3 hours; ninth zone: 3 hours; tenth zone: 2 hours.

7. A magnesium oxide calcining process according to claim 1, characterized in that: In the preheating section of the segmented calcination, a part of the hot air from the track kiln calcination section is introduced into the preheating section for preheating through an induced draft fan, and the other part is used in the magnesium carbonate production system, thereby realizing the recovery and utilization of waste heat and the materials it carries.

8. A system for calcining magnesium oxide according to any one of claims 1 to 7, characterized in that: It includes an automatic control system, a track kiln, and an induced draft fan; the automatic control system includes a system control module and a robotic arm, the system control module includes a 3D visual technology modeling unit and an Ai artificial intelligence technology simulation calculation unit, the automatic control system is used to realize digital control according to weight, time, formula, and raw material characteristics, and realize automatic loading / unloading of raw materials; the inlet end of the induced draft fan is connected to the discharge port of the track kiln calcining section, the first discharge end is connected to the inlet end of the track kiln preheating section; the second discharge end is connected to the raw material inlet of the magnesium carbonate production system; the track kiln is divided into a preheating section, a calcining section, a heat preservation section and a cooling section, each section is connected to a natural gas pipe, and a valve is provided on the natural gas pipe for temperature control.

9. The system for calcining magnesium oxide according to claim 8, characterized in that: The total length of the rail kiln is 82m, the width is 2.72m and the height is 2m, including a preheating section of 2.02m, a calcining section of 2.18m, a heat preservation section of 75.78m and a cooling section of 2.02m.

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