Magnetic magnetic separator

PTMS magnetic separation

what is magnetic separation in chemistry？

New developments in magnetic separation technology have provided an efficient method for magnetic cleaning drug raw materials. Today's innovative magnet materials and circuit design methods enable the production of magnetic separators to operate at higher field strengths than ever before. Therefore, many new techniques for cleaning and purifying pharmaceutical materials by magnetic separation have been developed. With all these new opportunities and demands for increased purity, it is critical that pharmaceutical companies fully understand the technology and implement key considerations when installing equipment.
Particle characteristics
When a magnetic field is exposed, the particles will show a specific response, dividing them into three categories: ferromagnetic, paramagnetic or diamagnetic.

Ferromagnetic particles have a very high magnetic susceptibility and are strongly induced by a magnetic field. Paramagnetic minerals have low magnetic susceptibility and weak response to magnetic fields. Finally, minerals with a negative magnetic susceptibility are called diamagnetic and are considered non-magnetic for all practical purposes.

When placed in a magnetic field, ferromagnetism and a lesser degree of paramagnetic material will be magnetized. The amount of magnetization induced on the particles depends on the mass and magnetic susceptibility of the particles and the strength of the applied magnetic field. This is expressed as:

The induced magnetization of the particles, the mass of the particles, the specific magnetic susceptibility, and the strength of the magnetic field.
Magnetic separation separator characteristics
Magnetic field strength and magnetic field gradient are key variables that influence the separation response. High-intensity magnetic separators typically operate in areas of 5000 Gauss or 0.5 Tesla. Low intensity separators typically produce magnetic field strengths of less than 2,000 Gauss or 0.2 Tesla.

Therefore, the magnetic particles entering the magnetic field will be attracted to the flux line and remain stationary without migrating to either pole piece.

As these lines pass through smaller areas, the magnetic field strength increases significantly. Magnetic particles entering the field structure are not only attracted to the flux lines, but also migrate to the region with the highest magnetic flux density.

According to the earlier magnetization equation, the magnetic attraction force acting on the particle is the product of the particle magnetization and the magnetic field gradient, which can be expressed as:

Among them is the magnetic attraction and is the magnetic field gradient. The maximum magnetic force is generated only when the magnetic field strength and the field gradient are both maximized.

There are two common methods for generating magnetic gradients in a magnetic separator. The first is a typical magnetic circuit using permanent magnets, which concentrates the flux lines on the steel pole pieces in the circuit. This can be achieved by placing a steel pole piece between the two magnets. The flux will concentrate in the steel pole piece, resulting in an area of ​​extreme magnetic field strength. The second involves directly positioning a steel substrate, such as a metal mesh, in a uniform magnetic field generated by an electromagnetic solenoid coil. Therefore, this matrix amplifies the magnetic field and converges the flux lines to produce a localized region of extremely high magnetic field strength.
Separation method
Magnetic field generation
All magnetic separators use permanent magnets or electromagnets to generate a magnetic field. There are two different types of permanent magnets for permanent magnets. "Ferrite" magnets are used in low intensity magnetic separators. These typically produce magnetic field strengths of up to 2000 Gauss (0.2 Tesla).

Another type of permanent magnet consists of rare earth elements. The advent of this type of magnet allows the design of high-strength magnetic circuits that are capable of free running energy. Rare earth magnets are used in various types of magnetic separators and efficiently collect paramagnetic particles. These separators generate magnetic field strengths of up to 24,000 Gauss (2.4 Tesla) depending on the magnetic circuit.

Electromagnet electromagnetic separators are usually designed with electromagnetic coils. Some separators use the holes of the solenoid as the separation zone. Other separators use electromagnetic coils to transmit magnetic flux through steel circuits or "C" circuits. The magnetic field in the gap, ie the hole in the solenoid or the gap in the C-frame, is the separation zone in the magnetic separator. Most electromagnetic separators operate up to about 20,000 Gauss (2 Tesla).

Magnetic separation separator
Fixed rare earth permanent magnet separator
Fixed permanent magnet separators, especially plates, grids and traps are commonly used to collect ferromagnetic iron particles and ensure product quality.
The plates, grids and traps are just rare earth permanent magnets that are arranged in the circuit and contained in a stainless steel casing. The process stream flows through or around the permanent magnets and the ferrous material is collected and retained.

Fixed permanent magnets have low investment costs and no operating costs. No moving parts, virtually eliminating maintenance costs. These separators are hand cleaned and are ideal for applications where only trace amounts of ferrous materials are present.

Magnetic filter
Magnetic collection of micron-sized paramagnetic particles requires high-intensity magnetic fields and high magnetic field gradients. This can be done with an electromagnetic matrix separator. The magnetic filter consists of an electromagnetic coil housed in steel. The coil produces a uniform magnetic field throughout the aperture. A porous metal mesh (referred to as a matrix) is deposited in the pores of the coil and induced by a magnetic field. The matrix produces a very high gradient local area and provides a collection site for paramagnetic particle capture. As the feed is filtered through the matrix, the paramagnetic particles are captured and thus removed from the particle stream. When the magnetic contaminants eventually accumulate on the substrate, the separator is de-energized and the substrate is rinsed clean.

The separator can be operated when the slurry is wet treated or dried. In wet mode, fluid resistance provides separation between magnetic contaminants and non-magnetic media. In the dry mode, the substrate vibrates and the fine material flows as it flows through the substrate.
Wet magnetic filter
Magnetic filters have a wide range or inner diameter and magnetic field strength to meet production capacity and the required level of magnetic collection. Wet magnetic filters have magnetic field strengths ranging from 1,500 Gauss to collecting ferromagnetic iron with 20,000 Gauss to collect fine paramagnetic contaminants, where product specifications require ppm or ppb contaminant levels. The duty cycle, the magnetic operating time between the substrate rinse cycles, is typically determined by identifying the amount of magnetic material contained in the filter feed. Materials containing up to 1% magnetic material will require frequent substrate flushing, corresponding to a duty cycle of 10 to 30 minutes.
Dry magnetic filter
The operation of high-strength magnetic separators for dry applications, including rare earth drums and rare earth rolls, always balances the magnetic attraction with a counterforce. With these types of separators, the separation efficiency decreases as the particle size decreases. Finer particles can react to electrostatic forces and other adhesions, resulting in poor separation. When the magnetic attraction force and the reaction force are no longer balanced, separation based on magnetic susceptibility is possible.

High frequency, low amplitude vibrations are applied to the substrate which fluidize the fines, resulting in high volume flow through the substrate. Dry filters have a wide range or inner diameter and magnetic field strength to meet production capacity and the required level of magnetic collection. (The dry vibrating magnetic filter for processing glass batches is shown in Figure 6.)

Particle size, shape and density are the main factors affecting the output of dry vibrating magnetic filters.
in conclusion
Recent advances in magnetic separation technology have produced various separators specifically developed for the processing of fine, high purity materials. The continued development of rare earth permanent magnets and the complexity of electromagnetic circuit design are considered to be the development of magnetic separators.

It is preferable to predict the separation response of fine-sized particles to magnetic separation. The theoretical determination of equilibrium particle size and magnetic force has little practical value at particle sizes of 50 to 75 microns. The natural variability of most materials, especially those containing iron contaminants, often requires laboratory or pilot magnetic separation tests to determine capacity and quantify separation efficiency.