Spray drying is used in the production of a wide variety of consumer goods,
from the food we eat, to the medicines that keep us safe and healthy. It is used throughout the
food manufacturing and pharmaceutical industries to rapidly dry liquid product feed into a powdered
material using heated gas for a variety of consumer and industrial applications.
The process begins when a liquid product feed is passed through a special nozzle called an atomizer.
The atomizer disperses the liquid stream as a mist of fine droplets into a heated
gas atmosphere to facilitate the drying process. There are various nozzle designs
such as pressure nozzles and rotary nozzles. The type of atomizer used will vary by application.
As the product feed is dispersed into the drying chamber the droplets rapidly dry as the liquid
evaporates the dried particles fall through the drying chamber for collection using a variety of
methods and packaging for further processing and distribution the heating gas is vented back into
the atmosphere this is the simplest form of spray drying otherwise known as a single pass system
several major components make up a typical spray drying system the process begins when the product
feed is delivered from the feed tank through the feed line to the atomizer which is located at the
top of the drying chamber drying gas is introduced to the drying chamber through the inlet hepa
the atomizer disperses the product feed as a fine mist of droplets into the drying gas once
the material has dried the particles pass through the system to the collection chamber where the
material is deposited into powder bags the heating gas is then vented out through the outlet hepa
in any spray drying system there are several key control variables that affect the success
of the process feed rate inlet temperature and outlet temperature these variables are all tied
together by the boundary value of drying gas flow the drying gas flow is usually held steady
at a high value while the others get adjusted to optimal levels for production on any given product
the specific method of adjustment will vary by system design and setup
spray drying systems can exist across multiple floors and through multiple graded spaces
more importantly a lot of what happens is often occurring between floors because the
spray drying operation can consist of equipment that passes through multiple levels it's important
to understand the scale of the entire operation and not just what is visible on any given floor
at the most basic level a spray drying system is composed of a feed tank
atomizer drying chamber collection chamber heater control panels intakes
exhausts and various fans and pumps all of these components are connected and work through
a series of ducts to help move the products and gases through the system during production
like any complex system there are safety factors that must be considered the most important safety
aspects for the common spray drying operation are asphyxiation powder contact and explosion control
depending on the type of drying gas in use asphyxiation can pose a significant danger
gas leaks can be hazardous or fatal without the proper safety precautions and monitoring equipment
if the spray drying process is being used for material that includes an api
powder contact with the skin can pose a danger to operators api mixtures can be considered
potent which means that inhalation and or human contact with the powder can produce an effect
even at low doses explosion risks are also a very real danger dust gas and heat can all serve as
potential trigger points for disaster dust for example can be exponentially more explosive than
dynamite explosion controls to mitigate the danger include redundant kill switches fire suppression
systems and even explosion vents the explosion coefficient and flammability of the product will
ultimately dictate the design and implementation of the explosion suppression system spray drying
is just one of the many steps that it takes to deliver products to the consumer it is a critical
component in the manufacturing chain with its own unique systems processes and safety considerations