Size Separation: Objectives, Applications & Mechanism of Size Separation

Size Separation

It involves separating a mixture of particles of different sizes into two or more portions using a screening surface. Sieving, sifting, and screening are additional names for size separation. Based on the differences in size, shape, and density between particles, this technique is used.

Elutriation

• Using a stream of gas or liquid flowing in the opposite direction of sedimentation, elutriation separates particles by their size, shape, and density.
• It consists of a horizontal column with a bottom inlet to accept suspension, a bottom outlet to receive coarse particles and a top outlet to handle fluids and fines.
• The apparatus can separate two fractions with a single column. Tubes with increasing cross sections can be connected in series if more than one fraction is required.
• With increasing cross-sectional area of the tube, the fluid's velocity decreases, giving birth to a series of fractions.
• Fractions are dried and separated.
• It is an ongoing process.
• If a fluid current isn't flowing through low-density particles, they remain unaffected.

Bag filter

• Density and size of the particles.
• The size separation of milled powder from fines (or dust) occurs in two steps in a bag filter.
• A cloth bag (made from fabric) is used to convey milled powder in the first step, followed by suction on the opposite side of the feed entry. In this way, the powder is separated.
• After shaking the bags, a pressure is applied in order to remove powder attached to the bag that falls from it, which is collected from the conical base.

Objectives of Size Separation

• Particle size determination is necessary for tablet and capsule production.
• Mixing powders should be improved.
• During production, particles should be made more solubilized and stable.
• During production, agitation, screening, and feed rate should be optimized.
• Raw materials are subject to quality control.
• Tablets, capsules, suspensions, emulsions, ophthalmic products, ointments, creams, etc. can be prepared with this product.

Applications of Size Separation

• In the production of tablets and capsules, particle size and size distribution are used to determine particle size.
• Analyze raw materials such as griseofulvin, aspirin, and even food to evaluate quality.
• Testing the effectiveness of size reduction processes.
• Optimise the conditions of the process, like the agitation method, screening time, and feed rate.

Mechanism of Size Separation

Mechanized sieving devices work according to one of the following methods.

Agitation - There are many different ways to agitate sieves, including:

• Oscillation - During operation, this sieve oscillates back and forth in a frame. Despite its simplicity, this method may result in material rolling over the sieve.
• Vibration - A high speed vibration device is used to vibrate the sieve. It is achieved by imparting rapid vibrations to the particles on the sieve, thereby allowing powdered materials to pass through it.
• Gyration - The third method employs a system whereby the sieve is attached to a rubber mounting and rotated by an eccentric flywheel. As a result, a small rotary motion is produced by the sieve, which in turn causes the particles to spin, allowing them to pass through the sieve.

Brushing method - In this case, the particles are moved on the surface of the sieve with the help of a brush. Normally, a circular sieve rotates its brush in the middle, while a horizontal cylindrical sieve rotates its brush along its longitudinal axis.

Centrifugal method - This method involves the use of a high-speed rotor that is set inside a cylindrical sieve, so that when the rotor rotates, the particles are hurled outward. As the rotor spins at high speed, air current is produced that helps sieve the powder.

Get subject wise printable pdf documentsView Here

Share

Tweet

Share

Share