Centrifuge / Reactor Blanketing
Centrifuge Blanketing System
The risk of flash fires and explosions is inherent in many plant operations, especially where volatile solvents and dusts are present in process vessels like high-speed industrial centrifuges. These conditions can create highly flammable environments, and without proper safety measures, the situation can lead to catastrophic fires and explosions.
The potential hazards associated with using industrial centrifuges for separating solids from flammable liquids have become increasingly recognized due to numerous serious incidents resulting in personal injury or death. Therefore, it is crucial for all individuals involved, from production operators to safety managers, to implement methods for monitoring and preventing such hazards.
Inertizing systems are well-established safety measures. Traditionally, there have been two main approaches:
Timed-Volume or Continuous-Purge Approach: This method involves initially flushing the vessel with inert gas, followed by a continuous flow of inert gas to maintain conditions below the Minimum Oxygen Concentration (MOC) level.
Pressurized Approach: In this method, the vessel is initially flushed with inert gas, and then positive pressure is maintained within the vessel using the inert gas.
Applications
There are various types and sizes of centrifuges, with the most common being the top or bottom discharge filtration batch centrifuge. Other types include the Continuous Decanter Centrifuge and the Disc Stack Centrifuge. Industrial centrifuges are widely used in diverse industries such as chemical, pharmaceutical, petrochemical, and food industries. Unfortunately, explosions involving centrifuges are reported annually, with accident inquiries often citing human error, equipment failure, or poor engineering design as major causes.
Typical Process Cycle of a Batch-Type Centrifuge:
Sweep or purge the centrifuge with an inert gas, typically nitrogen.
Introduce the feed slurry to the centrifuge for the separation stage.
Purge the centrifuge again with inert gas to remove oxygen.
Close the purging operation and start blanketing throughout the spinning process.
After final spinning, most of the liquid is removed from the cake.
Discharge the remaining solids from the basket or bowl.
Throughout these operations, the centrifuge must be inert, either through purging or blanketing with inert gas. The principle behind inertizing is to keep the oxygen level below the Minimum Oxygen Concentration (MOC) of 3-6%, thereby eliminating the possibility of an explosion.
In the pharmaceutical industry, three types of inertization systems are commonly used based on application, criticality, suitability, and commercial aspects:
Manual Centrifuge Blanketing System
Semi-Automated / Timer-Based System
Fully Automated / On-Line Oxygen Monitoring System