阅读说明：本技术 废旧氧化铍陶瓷制备氧化铍瓷粉的方法 (Method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic ) 是由 王刚 尚华 段冰 于 2020-05-06 设计创作，主要内容包括：本发明属于陶瓷材料技术领域,涉及废旧氧化铍陶瓷制备氧化铍瓷粉的方法。该方法包括以下步骤：A、对废旧氧化铍瓷件进行挑选、清洗；B、将步骤A预处理后的瓷件、氧化铍瓷球、去离子水混合球磨、过100～200目筛；C、将筛下物、瓷球混合球磨至D50为1～2μm,干燥得到循环瓷料；D、煅烧；E、破碎煅烧后的物料得到料团,将料团、瓷球、乙醇混合进行分散球磨至D50为1～1.5μm,干燥得到分散循环料；F、将分散循环料、瓷球、去离子水、三硅酸镁混合砂磨至粒度为0.5～1μm,干燥得到氧化铍瓷粉；球磨和细磨设备内衬材质为高分子材料。本发明方法制备得到的氧化铍瓷粉能够满足后续制备氧化铍陶瓷的使用要求。(The invention belongs to the technical field of ceramic materials, and relates to a method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic. The method comprises the following steps: A. selecting and cleaning waste beryllium oxide porcelain pieces; B. b, mixing and ball-milling the ceramic piece pretreated in the step A, beryllium oxide ceramic balls and deionized water, and sieving the mixture by a sieve of 100-200 meshes; C. mixing and ball-milling the undersize product and the porcelain balls until D50 is 1-2 μm, and drying to obtain a circulating porcelain material; D. calcining; E. crushing the calcined material to obtain a dough, mixing the dough, ceramic balls and ethanol, performing dispersion ball milling until D50 is 1-1.5 mu m, and drying to obtain a dispersion circulating material; F. mixing and sanding the dispersed circulating material, the ceramic balls, deionized water and magnesium trisilicate until the granularity is 0.5-1 mu m, and drying to obtain beryllium oxide ceramic powder; the lining material of the ball milling and fine grinding equipment is a high molecular material. The beryllium oxide ceramic powder prepared by the method can meet the use requirements of the subsequent preparation of beryllium oxide ceramics.)

1. The method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic is characterized by comprising the following steps of: the method comprises the following steps:

A. pretreatment: selecting and cleaning waste beryllium oxide porcelain pieces;

B. ball milling: b, mixing and ball-milling the ceramic piece pretreated in the step A, beryllium oxide ceramic balls and deionized water, sieving the mixture by a sieve of 100-200 meshes, and taking undersize products for later use;

C. fine grinding: mixing and ball-milling the undersize product and the porcelain balls until D50 is 1-2 μm, and drying to obtain a circulating porcelain material;

D. and (3) calcining: calcining the circulating porcelain at 1100-1200 ℃;

E. dispersing and ball-milling: crushing the calcined material in the step D to obtain a dough, mixing the dough, ceramic balls and ethanol, performing dispersion ball milling until D50 is 1-1.5 mu m, and drying to obtain a dispersion circulating material; the mass concentration of the ethanol is more than 99%;

F. sanding: mixing and sanding the dispersed circulating material, the ceramic balls, deionized water and magnesium trisilicate until the granularity is 0.5-1 mu m, and drying to obtain beryllium oxide ceramic powder; wherein, the lining material of the ball milling and fine grinding equipment is a high molecular material.

2. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to claim 1, which is characterized by comprising the following steps: the high polymer material is polyurethane, rubber or PVC and the like.

3. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to claim 1 or 2, which is characterized by comprising the following steps: in the step A, at least any one of the following conditions is satisfied:

the cleaning is carried out by mixing a polishing medium and water; further, the finishing medium is alumina ceramic; furthermore, the finishing medium is an alumina ceramic knob insulator with the diameter of 1mm and the length of 10 mm;

the addition amount of the finishing medium is 10-20% of the mass of the porcelain;

the cleaning time is 2-4 h.

4. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to any one of claims 1 to 3, which is characterized by comprising the following steps: in the step B, at least any one of the following conditions is satisfied:

the ceramic piece, the beryllium oxide ceramic ball and the deionized water are in a mass ratio of 1: 0.5-1;

the diameter of the beryllium oxide ceramic ball is 30-50 mm;

the ball milling time is 72-120 h.

5. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to any one of claims 1 to 4, which is characterized by comprising the following steps: in the step C, at least any one of the following conditions is satisfied:

the ceramic balls are zirconia ceramic balls or beryllium oxide ceramic balls; preferably zirconia ceramic balls; further, the diameter of the zirconia ceramic ball is 5-10 mm;

the adding amount of the ceramic balls is 3-5 times of the mass of the undersize;

the ball milling time is 1-3 h.

6. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to any one of claims 1 to 5, which is characterized by comprising the following steps: in the step D, the calcining time at 1100-1200 ℃ is 2-4 h.

7. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to any one of claims 1 to 6, which is characterized by comprising the following steps: in the step E, at least any one of the following conditions is satisfied:

the crushing head adopted for crushing is made of zirconia;

crushing into a material mass of 1-3 cm;

the mass ratio of the material balls to the ceramic balls to the ethanol is 1: 3-5: 0.5-1;

the ceramic balls are zirconia ceramic balls or beryllium oxide ceramic balls; more preferably zirconia ceramic balls; further, the diameter of the zirconia ceramic ball is 5-10 mm;

the lining of the dispersing ball-milling equipment is ceramic; further, the lining of the equipment is more than 95 percent of alumina ceramic;

the time of the dispersing ball milling is 2-4 h;

the drying temperature is 50-75 ℃.

8. The method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic according to any one of claims 1 to 7, which is characterized by comprising the following steps: in the step F, at least any one of the following conditions is satisfied:

the dispersing circulation material, the ceramic balls, the deionized water and the magnesium trisilicate are in a mass ratio of 1: 3-5: 0.5-0.8: 0.03-0.05;

the ceramic ball is a beryllium oxide ceramic ball or a zirconium oxide ceramic ball; more preferably zirconia ceramic balls; further, the diameter of the zirconia ceramic ball is 0.5-1 mm;

mixing the three raw materials except the ceramic balls for 30 min-1 h, and then adding the ceramic balls for sanding;

the sanding time is 1-2 h;

the drying adopts a spray drying mode; further, the inlet temperature of spray drying is 250-300 ℃, and the outlet temperature is 100-120 ℃.

Technical Field

The invention belongs to the technical field of electronic functional ceramic materials, and particularly relates to a method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic.

Background

The beryllium oxide ceramic is prepared from powder extracted from gem-grade mineral andalusite, has the characteristics of good heat-conducting property, high breaking strength, low dielectric constant, low dielectric loss and high insulating property, is widely used in the fields of military communication, remote sensing and remote measuring electronic countermeasure, photoelectric technology and the like, becomes a related field of microelectronic devices, photoelectric devices and the like, and is one of high heat-conducting ceramics with the highest practical degree at present.

As is well known, the ceramic is subjected to the problems of raw material mineral resource consumption, dust and toxic substance emission in the preparation process, and particularly, the beryllium oxide ceramic is more suitable. The beryllium oxide ceramic mineral source is the andalusite, the mineral resource is a rare substance in the world, although the content of Chinese is rich, the reserve accounts for only 16%, the yield per year is less than 200 tons, the beryllium oxide powder is high due to the shortage of resources, and the market price of the beryllium oxide raw powder is as high as 120 ten thousand/ton at present. Meanwhile, a large amount of waste products can be generated in the production and preparation process of beryllium oxide, a large amount of beryllium oxide waste can be generated after parts of beryllium oxide ceramic parts fail, the waste products are usually treated in a burying mode, the environment is polluted, a large amount of rare and precious resources are wasted, and the related development of the beryllium industry in China is not facilitated.

In order to realize sustainable development of beryllium oxide resources, domestic starts to research recycling of beryllium oxide ceramic waste ceramic parts in the last 90 th century, and a production method for preparing beryllium oxide circulating materials by adopting metal steel ball milling and acid pickling purification modes is formed at present. The whole production process has the defects of long production period, large environmental hazard, severe production conditions and the like, and specifically comprises the following steps:

1. industrial hydrochloric acid is used as a cleaning impurity-removing substance in a large amount, and a large amount of acidic wastewater is discharged in the cleaning process, so that the ecological environment is greatly harmed.

2. In the cleaning process, powder material ball-milled by the beryllium oxide porcelain piece can be partially dissolved in acid, has fine particles, and can be washed away by water in the cleaning process, so that beryllium-containing waste water is discharged, and environmental pollution is caused again. And the effective utilization rate of the waste porcelain is low, which is only about 50% on average.

3. The whole production environment is relatively severe due to the use of strong acid in the production process, certain corrosivity exists on production equipment and various appliances, and great health threat is caused to operators.

4. The production cycle is long, the acid washing cycle is 3-4 weeks generally, the sintering temperature of the prepared powder exceeds 1750 ℃ due to low activity, and the utilization value or the utilization cost is high.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic. The method comprises the following steps:

A. pretreatment: selecting and cleaning waste beryllium oxide porcelain pieces;

B. ball milling: b, mixing and ball-milling the ceramic piece pretreated in the step A, beryllium oxide ceramic balls and deionized water, sieving the mixture by a sieve of 100-200 meshes, and taking undersize products for later use;

C. fine grinding: mixing and ball-milling the undersize product and the porcelain balls until D50 is 1-2 μm, and drying to obtain a circulating porcelain material;

D. and (3) calcining: calcining the circulating porcelain at 1100-1200 ℃;

E. dispersing and ball-milling: crushing the calcined material in the step D to obtain a dough, mixing the dough, ceramic balls and ethanol, performing dispersion ball milling until D50 is 1-1.5 mu m, and drying to obtain a dispersion circulating material; the mass concentration of the ethanol is more than 99%;

F. sanding: mixing and sanding the dispersed circulating material, the ceramic balls, deionized water and magnesium trisilicate until the granularity is 0.5-1 mu m, and drying to obtain beryllium oxide ceramic powder; wherein, the lining material of the ball milling and fine grinding equipment is a high molecular material.

Specifically, in the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the high polymer material is polyurethane, rubber or PVC.

Specifically, in the step a of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the cleaning is carried out by mixing the polishing medium and water. Further, the finishing medium is alumina ceramic. Furthermore, the finishing medium is an alumina ceramic knob insulator with the diameter of 1mm and the length of 10 mm.

Preferably, in the step A of the method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic, the addition amount of the finishing medium is 10-20% of the mass of the ceramic piece.

Preferably, in the step a of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the addition amount of the water is only required to submerge the ceramic piece and the finishing medium.

Preferably, in the step A of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the cleaning time is 2-4 h.

Preferably, in the step B of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the ceramic piece, the beryllium oxide ceramic ball and the deionized water are in a mass ratio of 1: 0.5-1.

Preferably, in the step B of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the ball milling is performed by using a roller ball mill.

Preferably, in the step B of the method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic, the diameter of the beryllium oxide ceramic ball is 30-50 mm.

Preferably, in the step B of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the ball milling time is 72-120 h.

Preferably, in the step C of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the fine grinding is performed by using a stirring ball mill.

Preferably, in the step C of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the ceramic ball is a zirconium oxide ceramic ball or a beryllium oxide ceramic ball. More preferably zirconia ceramic balls. Furthermore, the diameter of the zirconia ceramic ball is 5-10 mm.

Preferably, in the step C of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the adding amount of the ceramic balls is 3-5 times of the mass of the materials below the sieve.

Preferably, in the step C of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the ball milling time is 1-3 h.

Preferably, in the step D of the method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic, the calcining time at 1100-1200 ℃ is 2-4 h.

Preferably, in the step E of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the crushing head used for crushing is made of zirconia. The crushing adopts a pre-crushing jaw crusher.

Preferably, in the step E of the method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic, the waste beryllium oxide ceramic is crushed into a material mass of 1-3 cm.

Preferably, in the step E of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the mass ratio of the material balls, the ceramic balls and the ethanol is 1: 3-5: 0.5-1.

Preferably, in the step E of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the ceramic ball is a zirconia ceramic ball or a beryllium oxide ceramic ball. More preferably zirconia ceramic balls. Furthermore, the diameter of the zirconia ceramic ball is 5-10 mm.

Preferably, in the step E of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the lining of the dispersing ball-milling equipment is ceramic. Further, the lining is more than 95% of alumina ceramics. The dispersing ball mill adopts a roller ball mill.

Preferably, in the step E of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the dispersing and ball milling time is 2-4 h.

Preferably, in the step E of the method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic, the drying temperature is 50-75 ℃.

Preferably, in the step F of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the dispersing circulation material, the ceramic balls, the deionized water and the magnesium trisilicate are in a mass ratio of 1: 3-5: 0.5-0.8: 0.03-0.05.

Preferably, in the step F of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the sand grinding is performed by using a sand mill.

Preferably, in the step F of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the ceramic balls are beryllium oxide ceramic balls or zirconium oxide ceramic balls. More preferably zirconia ceramic balls. Furthermore, the diameter of the zirconia ceramic ball is 0.5-1 mm.

Preferably, in the step F of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the three raw materials except the ceramic balls are mixed for 30min to 1h, and then the ceramic balls are added for sanding.

Preferably, in the step F of the method for preparing the beryllium oxide ceramic powder from the waste beryllium oxide ceramic, the sanding time is 1-2 hours.

Preferably, in the step F of the method for preparing beryllium oxide ceramic powder from waste beryllium oxide ceramic, the drying is performed in a spray drying manner. Further, the inlet temperature of spray drying is 250-300 ℃, and the outlet temperature is 100-120 ℃.

The method takes waste beryllium oxide ceramic pieces as raw materials, and the beryllium oxide ceramic powder is prepared through the procedures of sorting, cleaning, ball milling, fine grinding, calcining for impurity removal, dispersing for ball milling and sanding, and can be directly used for preparing the beryllium oxide ceramic subsequently. The method disclosed by the invention overcomes the problems of metal ball milling, strong acid pickling, long preparation period, excessive discharge of toxic and harmful substances, low material utilization rate, overhigh sintering temperature for preparing the porcelain and the like in the conventional beryllium oxide porcelain powder preparation process, realizes the recycling of the beryllium oxide ceramic material, does not generate harmful substances to the environment such as solid waste, harmful dust, waste water and the like in the recycling preparation process, and realizes the green manufacturing of the beryllium oxide ceramic. The beryllium oxide ceramic product prepared from the beryllium oxide ceramic powder has good overall performance, can meet the development requirements of military and civil high-power electronic devices and heat treatment systems on high performance and high reliability of the beryllium oxide ceramic, and has strong practical value.

The beryllium oxide ceramic powder obtained by the method can be used for forming beryllium oxide ceramic products through dry pressing, injection and tape casting, and the sintering temperature of the beryllium oxide ceramic powder is reduced to 1680 ℃ compared with the sintering temperature of normal beryllium oxide ceramic by adding a sintering aid magnesium trisilicate, wherein the sintering temperature of the beryllium oxide ceramic powder is more than 1750 ℃ in the traditional process. The beryllium oxide ceramic product produced by the method has good thermal property, mechanical property and electrical property, can meet the performance requirements of most of the fields of microelectronics, electric vacuum and photoelectrons on the high-heat-conductivity special ceramic at present, and has great market potential.

Detailed Description

The method for preparing the beryllium oxide ceramic powder by using the waste beryllium oxide ceramic comprises the following steps:

A. screening and cleaning the beryllium oxide waste ceramic pieces:

(a) manually screening the collected beryllium oxide waste ceramic pieces, selecting and removing blanks with colored impurities in the ceramic bodies, and keeping the blanks for later use;

(b) placing the screened porcelain piece blank into a vibration polishing machine, adding a polishing medium, adding tap water to immerse the porcelain piece and the polishing medium, performing vibration cleaning operation on the porcelain piece, removing harmful impurities such as oil stains, dust, corundum particles and the like which can be attached to the surface of the waste porcelain piece, fishing out the waste porcelain piece blank subjected to vibration cleaning by using a strainer, filtering out the polishing medium, rinsing the waste porcelain piece blank in the tap water (swinging and cleaning back and forth) for 2-3 times, and finally pouring the porcelain piece blank into a plastic basket frame, and airing the porcelain piece blank for later use;

B. ball milling of the porcelain:

after the ceramic piece blank body is aired, weighing related substances according to the ratio of the ceramic piece blank body to beryllium oxide ceramic balls to deionized water to be 1: 0.5-1, putting the weighed related substances into a roller ball mill for ball milling for 72-120 h, sieving ceramic piece slurry subjected to ball milling by using a 100-200-mesh sieve, and keeping the sieved slurry for later use;

C. fine grinding treatment:

pouring the sieved ceramic piece slurry into a stirring ball mill, adding ceramic balls with the diameter of phi 5-phi 10mm, the mass of which is 3-5 times that of the slurry, wherein the ball milling time is 1-3 h, carrying out particle size detection on the ball-milled slurry, controlling the size D50 to be 1-2 mu m, and drying the ball-milled slurry by using an oven to obtain a circulating ceramic material;

D. high temperature calcination

C, placing the circulating porcelain obtained in the step C into a burning pot, calcining in an oxidizing atmosphere kiln at the final temperature of 1100-1200 ℃, and burning off various high-temperature volatile impurities introduced in the ball milling and stirring ball milling processes;

E. dispersing ball mill

(a) Pre-crushing the calcined material block by using a jaw crusher to obtain a small material block of 1-3 cm;

(b) weighing corresponding substances according to the mass ratio of the calcined circulating material small briquette to the ceramic ball to the alcohol (the mass concentration of ethanol is more than 99 percent) being 1: 3-5: 0.5-1, putting the corresponding substances into the roller ball mill again for dispersion ball milling for 2-4 hours until D50 is 1-1.5 mu m, and putting the powder subjected to dispersion ball milling into an oven for drying for later use to obtain a dispersion circulating material;

F. sanding

(a) Taking out the powder after drying by the dispersion mill, and dispersing the circulating material according to the mass ratio: ceramic ball: deionized water: weighing corresponding substances according to the ratio of 1: 3-5: 0.5-0.8: 0.03-0.05, putting the ceramic balls into a sand mill, mixing and stirring the rest substances in a stirring barrel for 30 min-1 h, pouring the stirred circulating slurry into the sand mill, sanding for 1-2 h, and controlling the particle size of the sanded slurry to be 0.5-1 mu m;

(b) discharging the slurry after sanding, drying in a spray drying mode, and collecting powder, wherein the obtained powder is beryllium oxide ceramic powder which can be directly used for molding beryllium oxide ceramic to produce products; wherein, the lining material of the ball milling and fine grinding equipment is a high molecular material.

In the method, the ceramic is directly ground into slurry by the ball mill, so the abrasion is severe, and the lining material of the equipment can be abraded into the slurry, thereby polluting the slurry. The method selects the high molecular material as the lining of the ball milling equipment, and the lining material can be removed through the subsequent calcining step even if the lining material is worn and brought into the slurry. Although the degree of abrasion of the fine grinding is not more than that of the ball grinding, the fine grinding also has certain abrasion, and the lining of the fine grinding equipment is also made of high molecular materials. The high polymer material is polyurethane, rubber or PVC and the like.

In step A of the method, equipment used for cleaning the waste blank is a vibration polishing machine. The adopted finishing medium is alumina ceramic. The alumina ceramics is an alumina ceramics porcelain column with the diameter of 1mm and the length of 10 mm. The adding proportion of the finishing medium is 10-20% of the mass of the blank. The cleaning time is 2-4 h.

In step B of the method, the ball milling equipment is a roller ball mill. The diameter of the beryllium oxide porcelain ball is phi 30-phi 50 mm. The beryllium oxide ceramic ball is also used for ensuring that other impurities are not introduced in the ball milling process. The ball milling time is 72-120 h. In order to ensure that the subsequent fine grinding can reach the corresponding particle size range, the slurry after ball milling needs to be filtered by a 100-200 nylon screen.

In the step C of the method, the fine grinding equipment is a stirring ball mill. The ceramic ball is a beryllium oxide ceramic ball or a zirconium oxide ceramic ball. In order to save raw material cost, zirconia ceramic balls are preferred. Furthermore, the diameter of the zirconia ceramic ball is phi 5-10 mm. The ball milling time is 1-3 h.

In the step D of the method, the kiln used for calcination is an oxidation or air atmosphere kiln. The highest temperature of the kiln is 1100-1200 ℃, and the heat preservation time is 2-4 h. Removing the high molecular material introduced in the ball milling and fine milling processes by a high-temperature calcination mode.

In step E of the method of the present invention, in order to ensure that the slurry is not doped with impurities, the crushing head of the crushing apparatus is made of zirconia. The specific crushing adopts a pre-crushing jaw crusher. The diameter of the crushed material mass is between 1 and 3 cm.

In step E of the method of the present invention, (b), the lining of the dispersion ball mill apparatus is ceramic. The lining is more than 95% of alumina ceramics. The dispersing ball mill adopts a roller ball mill. The ceramic ball is a beryllium oxide ceramic ball or a zirconium oxide ceramic ball. In order to save raw material cost, zirconia ceramic balls are preferred. Furthermore, the diameter of the zirconia ceramic ball is phi 5-10 mm. Industrial alcohol (with a mass concentration of more than 99%) is used as a dispersant.

In the step E of the method, the circulating powder is obtained by adopting an oven drying mode after the alcohol dispersion grinding, wherein the oven drying temperature is 50-75 ℃.

In step F of the method, the sanding process is carried out by a sand mill. The ceramic ball is a beryllium oxide ceramic ball or a zirconium oxide ceramic ball. In order to save raw material cost, zirconia ceramic balls are preferred. Furthermore, the diameter phi of the zirconia ceramic ball is 0.5-1 mm. Deionized water is used as a dispersant. Analytically pure (AR) magnesium trisilicate was used as a subsequent sintering aid.

In step F of the method, powder is dried by adopting a spray drying mode for the dispersed circulating material after sanding. The inlet temperature of spray drying is 250-300 ℃, and the outlet temperature is 100-120 ℃.