Pharmaceutical Unit Operations: Size Reduction, Heat Transfer, and More

Posted on Sep 8, 2024 in Geology

Pharmaceutical Unit Operations

Size Separation

Size separation is a pharmaceutical process that involves separating particles of the desired size from a mixture of various-sized particles.

Size Reduction

Size reduction is the process of reducing large drug substances into smaller particles.

Manometer

A manometer is a device used to evaluate the pressure of a fluid by comparing it with a predetermined column of standard fluid. Types of manometers include:

  • Simple Manometer
  • Differential Manometer

Heat Transfer

Heat transfer is the transfer of heat from a warmer fluid to a cooler fluid, usually through a solid wall separating the two fluids. Applications include power generation.

Evaporation

Evaporation is a process that converts liquid into gas by absorbing heat. Applications include wet reduction, concentrating products, and manufacturing drugs.

Fluid Flow

Fluid flow is the motion of a fluid subjected to unbalanced forces. Types of fluid flow include:

  • Turbulent Flow
  • Transitional Flow
  • Steady Flow
  • Unsteady Flow

Hammer Mill

Principle

As material passes through the mill, it is subjected to repeated impacts, attrition, shear, and compression, resulting in reduced particle size.

Construction

A hammer mill consists of:

  1. Rotor: A horizontal or vertical shaft with attached hammers.
  2. Hammers: Swinging or fixed hammers that crush material.
  3. Grate: A perforated screen that allows crushed material to pass through.
  4. Frame: The housing that supports the rotor and grate.

Working

  1. Material is fed into the mill through a hopper.
  2. The rotor spins, and hammers swing or rotate, crushing the material.
  3. Crushed material passes through the grate and is collected.

Uses

  1. Crushing and grinding grains, corn, and other agricultural products.
  2. Milling spices, herbs, and other food products.
  3. Pulverizing minerals, ores, and rocks.
  4. Shredding paper and cardboard.

Advantages

  1. High production capacity.
  2. Easy to operate and maintain.
  3. Can handle a wide range of materials.
  4. Relatively low cost.

Disadvantages

  1. Can generate heat, leading to material degradation.

Ball Mill

Principle

As the drum rotates, the balls are lifted and dropped, creating a cascading effect that grinds the material. The drum liners protect the drum from wear and tear while also helping to grind the material.

Construction

A ball mill consists of:

  1. Cylindrical drum (shell) with a horizontal axis
  2. Drum liners (protective layer)
  3. Forced feed hopper
  4. Discharge hopper
  5. Ball charge (steel or ceramic balls)
  6. Drive system (motor, gearbox, bearings)

Working

  1. Material is fed into the drum through the hopper.
  2. Balls are lifted and dropped, grinding the material.
  3. Material is crushed and pulverized between balls and drum liners.
  4. Ground material is discharged through the hopper.

Uses

  1. Grinding and milling ores, minerals, and rocks.
  2. Mixing and blending materials.
  3. Refining and powdering chemicals.
  4. Pulverizing coal and other fossil fuels.

Advantages

  1. High production capacity.
  2. Versatile and adaptable to various materials.
  3. Low maintenance and operating costs.
  4. Can handle abrasive and hard materials.

Disadvantages

  1. High energy consumption.

Orifice Meter

An orifice meter is a device used to measure the flow rate of a fluid (liquid or gas) through a pipe. It works on the principle of differential pressure measurement.

Working

  1. Fluid flows through the orifice plate, creating a pressure drop.
  2. Pressure difference is measured between upstream and downstream taps.
  3. Flow rate is calculated using the pressure difference and orifice plate dimensions.

Advantages

  1. Simple and inexpensive.
  2. High accuracy.
  3. Wide range of applications.

Energy Losses

The energy losses associated with an orifice meter are:

  1. Permanent pressure loss: The irreversible loss of pressure due to friction and turbulence as the fluid flows through the orifice plate.
  2. Temporary pressure loss: The reversible pressure loss due to the acceleration and deceleration of fluid as it passes through the orifice plate.
  3. Friction loss: The loss of energy due to friction between the fluid and the orifice plate, as well as friction within the fluid itself.
  4. Turbulence loss: The loss of energy due to turbulent flow created by the orifice plate.
  5. Vena contracta loss: The loss of energy due to the contraction of the fluid stream as it passes through the orifice plate.
  6. Re-expansion loss: The loss of energy as the fluid expands downstream of the orifice plate.

Steam Distillation

Steam distillation is a separation process that uses steam to distill mixtures of liquids with different boiling points. It’s commonly used to:

  1. Separate heat-sensitive or high-boiling-point substances.
  2. Purify essential oils, fragrances, and flavorings.
  3. Recover volatile compounds from aqueous solutions.

Process

The process involves:

  1. Steam injection into the mixture.
  2. Vaporization of the volatile components.
  3. Condensation of the vapor mixture.
  4. Separation of the condensed liquid mixture.

Advantages

Steam distillation offers advantages such as:

  1. Lower operating temperatures.
  2. Reduced risk of thermal degradation.
  3. Improved separation efficiency.

Applications

Common applications include:

  1. Essential oil extraction (e.g., lavender, tea tree).
  2. Flavor and fragrance production.
  3. Pharmaceutical and cosmetic manufacturing.
  4. Food processing and beverage production.

Steam distillation is particularly useful for separating mixtures where traditional distillation methods are not effective or would cause degradation of the desired compounds.