Characteristics of Nitrogen Protected Grinding Equipment

Nitrogen protection grinding equipment is suitable for the grinding of explosive and oxidizable substances. The grinding effect of nitrogen protection airflow grinder is good, and the stability and safety are higher than that of general airflow grinder. The nitrogen-protected grinding equipment has a compact structure, polished inner and outer walls, no stock in the grinding box, no dead corners, easy to clean, and meets GMP requirements.

The materials collide and grind, and the materials with Mohs hardness 1-10 can be processed. The products are free of iron pollution and can be mixed and pulverized with several materials; good grinding efficiency and strict particle size distribution can be obtained, and the grinding particle size can be 2 -74μm can be adjusted arbitrarily, up to sub-micron level, and material loss is small; the whole system adopts a touch screen automatic control system, which can realize one-button start and stop, simple and convenient operation, and realize remote control.

Features of Nitrogen Protection Grinding Equipment:

1.  Oxygen isolation: Before starting the feed, replace the air in the closed circulation system with nitrogen. At the same time, the closed feeding and unloading system can replace the air in Shaoli during the feeding and unloading process with nitrogen to maintain the oxygen in the system. The content is basically stable. During the grinding process, an oxygen content tester is used to continuously monitor the oxygen content in the airflow, and when it exceeds a certain level, nitrogen is added immediately to keep the oxygen content within the safety production standard.

2.  Control the concentration of gas and powder: the feeding system is a fully enclosed, uniform speed device, which is programmed and controlled by the control cabinet. Fully enclosed plays the role of isolating oxygen, while the uniform speed controls the concentration of the materials inside the added equipment, and the feeding speed can be set arbitrarily. If the materials added to the equipment at a constant speed accumulate inside the equipment, there is no guarantee of safety. Therefore, the shape of the equipment, such as the bending angle of the pipe, the shape of each part, etc., are scientifically calculated to eliminate the dead corners inside the equipment. At the same time, the high-speed airflow in the equipment is driven and washed, and the powder will not accumulate in the pipe.

3.  Timely release of static electricity and elimination of ignition sources: The special filter material with carbon steel wire used for the pulse blowback collector can eliminate static electricity in time and ensure that the pulse cleaning is clean and thorough. The nitrogen protection grinding equipment is all metal components, all grounded, and try to release the powder static electricity.

4.  Circulating air cooling: Because the whole system is a closed circuit system, there are multiple moving parts inside the equipment, which will produce a certain temperature during high-speed movement, and the temperature is very important to the safety of processing. Therefore, the equipment is equipped with a fin-type cooler on the pipeline, which can effectively reduce the safety hazards caused by the equipment working for a long time or working in a high temperature environment.

by ALPA Powder

Basic conditions for choosing an ultra-fine grinder

  1. Material properties

The nature of the material includes the nature and density of the abrasive material. Under the action of the negative pressure airflow caused by the fan, the material ground by the airflow mill is taken out of the grinding chamber, enters the material collection system, filtered by the filter bag, the air is discharged, the material and dust are collected, and the grinding is completed.

The ultra-micro grinding machine is a device that uses air separation, pressure grinding, and shearing to achieve ultra-micro grinding of dry materials. It is composed of cylindrical grinding chamber, grinding wheel, grinding rail, fan, material collection system and so on. The material of the superfine pulverizer enters the cylindrical grinding chamber through the feeding port, and is crushed and sheared by the grinding wheel that moves in a circular motion along the grinding rail to realize grinding.

  1. Material status

The material status mainly refers to the humidity and temperature of the material. Unlike wet grinding, in dry grinding, the water content of the material cannot exceed 3%, otherwise the processing capacity of the grinder will drop sharply, especially the dry ball mill is more important.

  1. Material size

Unlike the crusher, the feed size has a great influence on the output of the crusher, and is one of the main factors affecting the processing capacity of the grinder. Therefore, the energy consumption in the crushing and grinding stages is different, and the energy consumption in the crushing stage is much less. It is very important to apply the principle of more crushing and less grinding in the crushing operation. Therefore, in the crushing stage with less energy consumption, the material should be crushed to a finer particle size as much as possible to reduce the energy consumption in the grinding operation.

  1. Grinding ability

Even if the product needs to be grinded according to the requirements, the crusher can be selected to obtain the same size of material particles, and then the appropriate grinder can be selected according to the type and size.

  1. Grinding method

Grinding methods are divided into wet and dry methods. Wet grinders: limited to rotary grinders and tower grinders that use steel balls or other media, and there are also many dry grinders. Which type of grinding machine is used is affected by the operation before and after grinding, the number of grinding sections, and the choice of grinding process.

by ALPA Powder

The composition & function of the air classifier system

Some application fields of ultrafine powder have certain requirements on the particle size distribution or gradation of ultrafine powder. Only fine classification of ultrafine powder products can meet the requirements, such as microelectronics, advanced ceramics, advanced abrasives, paper fillers and Coatings, plastics and rubber fillers, paint pigments or fillers, toners and other industries. Airflow classifier is a professional equipment for fine classification of ultra-fine powder, and it has been widely used in various fields.

The air flow classifier is mainly composed of a feeding control system, a classifier host (1-4 units), a high-efficiency cyclone collector, a pulse bag filter, a high-pressure induced draft fan and an electrical control system.

(1) Feeding control system: The feeding control system is composed of a star feeder or a vibrating feeder combined with a frequency conversion control instrument, a feeding bin, etc., and a continuous uniform speed control of the feeding is achieved by adjusting the output frequency/current level of the feeder.

(2) Classifier host: The classifier host is mainly composed of a motor, a grading wheel, a cylinder, etc., which can effectively classify materials by adjusting the speed of the grading wheel and cooperating with the secondary air.

(3) The impeller of the classifier is adjusted by the frequency converter, and protection measures such as loss of voltage protection, over current protection, material level control, operation status monitoring and alarm system are designed.

(4) Cyclone collector: This equipment is a first-level collection system in classified products. After the dust-laden airflow enters the cyclone collector, due to the centrifugal force, the powder will slide down the wall of the cylinder and be separated and purified at the end of the inner cone. The purified gas and a small amount of fine powder are discharged through the cyclone center tube.

(5) Pulse bag filter: This equipment consists of a bag collection device, a pulse cleaning device and a pneumatic control device.

by ALPA Powder

Performance characteristics of air classifier

Air classifiers are often used in series with grinding equipment because it can precisely control the particle size of the finished product. For example, the airflow grinding equipment with a classification system is screened by the classification system after grinding, and the particles of qualified particle size are passed through the classification wheel with the airflow to the next process, and the coarse particles that do not meet the particle size are returned to the grinding chamber to continue grinding. Because of the precise screening function of the air classifier, it can be used not only alone, but also in series with most grinding equipment.

The principle of the air current classifier is that the material is quantitatively raised to the classification area through the feeder under the action of negative pressure air, and under the action of the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated, and the fine particles meeting the particle size requirements pass through The gap between the grading wheel blades enters the cyclone separator or the dust collector to collect, the coarse particles entrained by the part of the fine particles hit the wall and the speed disappears, and descends along the cylinder wall to the secondary air outlet. After the strong elutriation of the secondary air, the coarse and fine particles are separated. The fine particles rise to the classification zone for secondary classification, and the separated coarse particles are discharged through the unloader.

Performance characteristics of air classifier

  • It is suitable for fine grading of powder, the particle size of the grading product can reach D50:1~45μm, the product size can be adjusted, and the variety change is extremely convenient.
  • High classification efficiency (extraction rate) 60% to 90%.
  • The classification accuracy is high, the particle size distribution is narrow, and oversized particles and sieve residues in the product are completely eliminated.
  • Low rotation speed and long service life: The rotation speed of the classification wheel is 50% lower than other horizontal and vertical classifiers for the same classification particle size. When producing powder with Mohs hardness <5, the grading wheel has no abrasion; when producing powder with Mohs hardness ≥ 7, the service life of the grading wheel is 5-8 times longer than that of other horizontal and vertical types.
  • The vertical grading turbine device is adopted, which has low speed, wear resistance and low system power configuration.
  • Multi-stage classifiers can be used in series to produce products with multiple particle sizes at the same time.
  • It can be used in series with jet mill, impact mill, ball mill, vibration mill, Raymond mill and other grinding equipment to form a closed loop.
  • The system is produced under negative pressure, no dust pollution, excellent environment, high degree of automation, strong stability, and easy operation.

by ALPA Powder

Factors of gear wear of ball mill

According to the investigation, when the ball mill is in operation, most of the components are running very well, except that the large and small gears of the ball mill are frequently worn out, and the scrap rate is very high, which increases the production cost. So what causes the gear wear of the ball mill?

1.   Poor lubrication conditions: In actual operation of the ball mill, the lubrication effect of the gear lubrication points is not ideal, because as the gear rotates or the speed increases, most of the grease does not enter the gear surface under the action of centrifugal force. It was thrown to the gear cover, and dropped onto the surface of the gear in the vibration of the gear cover, and was still directed to the gear cover, and finally fell to the bottom of the gear cover. As a result, the gear meshing parts have poor lubrication conditions, and dry friction or boundary friction will occur at the local meshing points of the tooth surface, causing serious wear and failure of the gear surface.

2.  Frequent slurry leakage of the equipment: During the operation of the ball mill, due to improper operation or improper maintenance, there is a slurry leakage in the ball mill, and the slurry enters the gear without being cleared in time, causing the gear to wear; or the threaded hole at the hole cover of the ball mill is leaking. Pulp, causing gear wear.

3.  Poor sealing performance: If the performance of the sealing element of the ball mill is too poor, a large amount of debris will enter the grease during operation, such as excessive mineral pulp, powder particles and other impurities. As a result, the gear lubrication conditions are worse, aggravate the wear of the gear, shorten the operating life of the gear, and increase the user's production cost.

4.  The installation accuracy cannot be achieved: Although the ball mill has a simple structure and high manufacturing and installation accuracy requirements, when installing the gear of the ball mill, the manufacturing process and installation methods must be emphasized. If the lubricating oil is not added in time during installation to relieve the friction of the installation, the wear will be increased and the service life of the ball mill gear will be short.

by ALPA Powder

Types of dust collector

Dust collector is a dust removal equipment that separates dust from flue gas. The performance of the dust collector is expressed by the amount of gas that can be processed, the resistance loss when the gas passes through the dust collector, and the dust removal efficiency. At the same time, the price of the dust collector, operation and maintenance costs, the length of the service life and the difficulty of operation and management are also important factors to consider its performance.

Dust collectors are divided into the following categories according to their principle of action:

  • Filter type dust collector, including bag filter and particle layer dust collector, etc.
  • Electrostatic precipitators.
  • Magnetic dust collector.

Dust collectors are divided into:

  • Dry dust collector;
  • Semi-dry dust collector;
  • Wet dust collector.

The working principle of the dust collector:

After the dust-containing gas enters from the upper air inlet of the ash hopper, under the action of the wind baffle, the air flow flows upward, the flow rate is reduced, and some large particles of dust are separated and fall into the ash hopper due to inertial force. The dust-containing gas enters the middle box and is filtered and purified by the filter bag, and the dust is trapped on the outer surface of the filter bag. The purified gas enters the upper box through the filter bag mouth and is discharged from the air outlet. The most commonly used in modern industry are: electric bag compound dust collector and bag dust collector.

The electric bag compound dust collector is installed in a box, with a short electric field installed at the front end and a filter bag field installed at the back end. The smoke and dust are introduced from the left end and pass through the electric field area first. The dust particles in the electric field area are 80%-90% charged. Dust is collected (use the advantages of electric dust removal to reduce the load on the filter bag field). The flue gas passing through the electric field enters the filter bag area for secondary filtration, and enters the inner cavity of the filter bag through the outer surface of the filter bag. The dust is trapped on the outer surface of the filter bag, and the pure gas is discharged from the inner cavity into the flue. Exhaust from the flue.

The electric bag compound dust collector combines the advantages of the electric dust collector and the pure bag dust collector, and is a new generation of dust removal technology.

Precautions for the use of dust collector:

During use, prevent the gas from cooling below the dew point temperature in the bag chamber, especially when using the bag filter under negative pressure. Because the shell often has air leakage, the air temperature in the bag room is lower than the dew point temperature, and the filter bag will be damp. As a result, the dust is not loosely attached to the filter bag, but sticky to the filter bag, resulting in a paste. The bag cannot remove dust, and the holes of the filter bag are blocked, causing the cleaning failure, and the pressure drop of the dust collector is too large, and the operation of the dust collector cannot be continued.

by ALPA Powder

Reasons for the lower and lower output of ball mills

  1. "Saturated grinding" is the main reason that affects the output of ball mills

When the output of the ball mill is getting lower and lower, the first thing to consider is whether there is a phenomenon of "saturated grinding". The causes of "saturated grinding" are: too much feed; the hardness and particle size of the grinding material become larger; The material has too much moisture; the steel ball grading is unreasonable; the compartment board or the grate is blocked by debris. The solution to the "full grinding" problem: reduce the amount of feed; when the size or hardness of the grinding material changes, make corresponding adjustments in time; adjust the water content of the grinding material; reasonably configure the large, medium, and small steel balls Than; clean up the blockage of the compartment board or grate seam; increase the ventilation of the ball mill cylinder.

  1. The working time of the ball mill is too long

The length of the milling time directly affects the product composition and purity, and the impact of the milling time on the particle size is also obvious. In the initial stage, with the extension of time, the particle size decreases faster, but after the ball milling for a certain period of time, even if the ball milling time continues to be extended, the particle size value of the product does not decrease too much. Different materials have different optimal ball milling times. On the other hand, the longer the milling time, the more serious the pollution caused, which affects the purity of the product.

  1. Failure to add steel balls in time

The grinding effect of the ball mill and the output are restricted by the steel balls of the ball mill. With the grinding and impact of the steel balls in the cylinder, the steel balls will wear out. Therefore, the steel balls must be added in time to ensure the output of the ball mill consistency.

  1. The temperature in the cylinder rises

The temperature of the ball mill increases during operation, the effective strain of the ball mill to form nanomaterials is reduced, and the crystal grain size increases, which significantly affects the mechanical properties of the powder made into bulk materials. Moreover, whether the final product of ball milling is solid solution, intermetallic compound, nanocrystal, or amorphous phase, diffusion is involved, and diffusion is affected by the grinding temperature, so temperature is also an important factor affecting the output of the ball mill.

  1. The material moisture content is too high

Due to the large moisture content of the material, the uniformity of the feeding is affected and the feeding time is prolonged. Secondly, because the wet material is fed too much, it may cause the phenomenon of paste ball and paste liner in the mill, and even "full grinding" will be forced to stop the grinding process. Generally speaking, for every 1% increase in the comprehensive moisture of the material entering the mill, the output of the ball mill will decrease by 8%-10%; when the moisture is greater than 5%, the ball mill basically cannot perform grinding operations.

  1. Addition ratio of grinding aid

Grinding aids are allowed to be added in the cement production process, but the addition amount should not exceed 1%. Adding more than this standard is unreasonable. In addition, most of the grinding aids are substances with strong surface activity, which are not suitable for all materials. They should be added reasonably according to the nature of the materials.

To sum up, if the output of your ball mill is getting lower and lower, first check whether the "full grinding" phenomenon occurs. If not, then perform investigations based on other reasons to find the crux of the problem, and then you can fundamentally solve the problem of low output. The problem caused the ball mill to resume production as soon as possible, bringing greater economic benefits.

by ALPA Powder

The fineness and purity of the jet mill are the main performance "highlights"

The jet mill has various properties such as winnowing type, no screen, no net, uniform particle size, etc., and the production process is continuous. This machine has reached the international advanced level and is widely used in the grinding of materials in the pharmaceutical, chemical, food and other industries. It is suitable for the grinding of various non-metallic minerals, cement, building materials and other brittle materials. It can also be used for some materials difficult to achieve grinding fineness. The jet mill adopts purified and dry compressed gas, which is jetted into the grinding chamber at a high speed through a special supersonic nozzle. The air flow carries the material at high speed, causing strong collision, friction and shearing between the material and the material to achieve the purpose of grinding.The ground material rises into the classification chamber, the material that meets the particle size requirements passes through the forced impeller classifier, and the particles that do not meet the particle size requirements return to the grinding chamber to continue grinding.

The entire production process is fully enclosed and continuous operation, no dust pollution, and the air is purified after dust removal and filtration. The grinding principle of the jet mill determines the typical characteristics of the machine such as wide application range, fine particle size and high product purity. It can be matched with inert gas to form a new type of inert gas closed-circuit protection grinding production line, which is widely used in flammable, explosive, easy to oxidize, etc. grinding processing of materials.

The reason why the jet mill is favored by the majority of users is mainly because it has many "highlights", one is "fineness", as the name suggests is how fine the jet mill can grind, and the application requirements of various industries are different, how Achieving the established fineness is the primary consideration when designing and manufacturing. Various materials require different grinding fineness, depending on the applicable industry and the requirements for material grinding. The second is "purity", which requires no pollution during the grinding process and the original composition should be maintained. Many materials will have some chemical effects during grinding due to temperature, humidity and other reasons, especially in the pharmaceutical industry of Chinese herbal medicine grinding, this is even more important. Therefore, the temperature, humidity and other conditions of the material must be considered in the design. The airflow of the jet mill must have a high speed in order to generate a lot of energy. Therefore, increasing the air velocity of the nozzle is beneficial to improving the material grinding effect and grinding efficiency. However, if the pursuit of high speed is too high, energy consumption must be increased.

by ALPA Powder

Factors affecting the performance of cyclone dust collector

There are many factors that affect the performance of the cyclone dust collector. Generally speaking, one is the structure factor, and the other is the operating condition factor.

The structural factors are generally divided into four aspects:

  1. Entrance and top

1) The inlet form is generally divided into two types, direct inlet and vortex inlet.

2) The top of the dust collector is usually flat, but there are also raised and spiral types.

  1. Exhaust pipe

The exhaust pipe of ordinary cyclone dust collector is mostly cylindrical and concentric with the body of the dust collector. The shorter the insertion depth of the exhaust pipe, the lower the pressure loss.

  1. The length and diameter of the dust collector

Generally, when the ratio of length to diameter is greater than 2, it is called a high-efficiency cyclone dust collector; when it is less than 2, it is a low-type cyclone dust collector. The former is more efficient because the dust stays in it for a long time.

  1. Roughness of the inner wall

The rougher the inner wall of the cyclone dust collector, the easier it is to cause vortex, which will increase fluid resistance and reduce dust collection efficiency. Therefore, in the manufacturing, attention should be paid to the smooth welding seam, and the cylindrical and conical heads should strive to be smooth.

Factors in operating conditions

The operating conditions of the dust collector include factors such as gas flow, temperature, dust particle size and density.

  1. Gas performance

1) Gas flow: The efficiency and resistance of the cyclone dust collector are related to the flow rate of the gas into the dust collector.

2) Gas temperature: The gas temperature directly affects the viscosity coefficient of the gas. The coefficient of viscosity increases with the increase of temperature, while the dust collection efficiency decreases with the increase of temperature.

  1. Dust properties

1) Particle size of dust

The efficiency of the cyclone dust collector is very sensitive to the particle size of the dust. Generally, the efficiency of particles smaller than 5μm is low, while the dust collection efficiency of particles larger than 20μm is more than 90%.

2) Density of dust collection

The higher the dust density, the higher the efficiency; when the density reaches a certain value, the smaller the particles, the greater the influence of density. However, the impact on the actual dust collection range of the dust collector is relatively small.

3) Dust concentration

The dust concentration has an impact on the efficiency and resistance of the dust collector. The effect of dust concentration on the performance of the dust collector is that when the dust concentration is high, the friction loss between dust particles increases, the rotation speed of the airflow decreases, and the centrifugal drop occurs, which reduces the resistance and efficiency; but on the other hand, On the other hand, the increase of the concentration will cause the agglomeration of dust, which will increase the dust collection efficiency.

Therefore, only a sufficient understanding of the factors that affect the performance of the cyclone dust collector can better avoid performance loss and make the dust collection efficiency of the cyclone dust collector better.

by ALPA Powder

What to do if the work efficiency of the ball mill is low

The ball mill is a kind of beneficiation equipment. Its main function and function is to grind and process various minerals. However, the work efficiency in the production process is very low. How to solve such problems?

  1. The equipment configuration is low

There is a close relationship between the level of equipment configuration and production capacity, and the higher the production capacity, the higher its work efficiency will be. At this time, the output can also meet the user's standard. Otherwise, the work efficiency will be low. Therefore, users must choose equipment with high configuration when purchasing equipment, so that the problem of low work efficiency can be easily solved.

  1. Poor operating performance

If the equipment is prone to problems during operation, it will inevitably affect production, and the performance of the equipment is directly related to the motor. Only a good motor can ensure the stability of the equipment, and in the actual production process Higher reliability, this move provides a hardware foundation for improving the efficiency of the equipment.

  1. The problem of failure rate

The production capacity of equipment with high failure rate is necessarily low. The failure of equipment is caused by technical reasons. Generally speaking, equipment with high technology content will have higher technology content. On the contrary, equipment with low technology is not enough to meet the normal production of users. This is also one of the main reasons for its work efficiency. When purchasing equipment, you must choose carefully.

  1. User operation

In the course of use, improper operation will also lead to a sharp decline in the production capacity of the equipment. Therefore, it is quite necessary to effectively improve the user’s operational proficiency. Therefore, various manufacturers have increased the training level of their employees. In this process, the equipment The production capacity has been greatly improved, and the output also meets the actual production standards of users.

  1. External environmental factors

Changes in the external environment will also cause the equipment’s working efficiency to be low, because the ambient temperature will have a great impact on production, too high or too low temperature is not conducive to production and operation, so it is necessary to install a temperature controller on the equipment and start it officially In the past, effective temperature detection was required to provide necessary preparations for improving the production efficiency of the equipment.

by ALPA Powder