n 14 MAY 2015 | PHARMACEUTICAL PROCESSING
nSTERILE PROCESS ■ PHARMPRO.COM
Pure water is as necessary to a pharmaceutical manufac- turer’s existence as oxygen is to the patients it serves.
The trouble is, water doesn't want to
be pure. It wants to dissolve things,
and as a universal solvent, it’s very
good at that. In pharmaceutical manufacturing the dissolved oxygen and
CO2 in water can mean death to the
manufacture of products designed to
preserve the health of customers.
So to ensure purity in the manufacture
of medicines, dissolved oxygen and CO2
must be removed and prevented from
contaminating the water supply. This is
especially true of water stored in tanks.
Oxygen in water can lead to microbial
growth and CO2 can affect water’s pH.
One procedure to remove these impuri-ties is called sparging. Typically, nitrogen
is used not only to deaerate water, but to
prevent oxygen and CO2 reabsorption.
While nitrogen makes up 78 percent of the air we breathe, harnessing its properties for pharmaceutical
manufacturing can be problematic and
expensive. Nitrogen can be ordered
from outside vendors but delivery,
storage and handling high pressure
cylinders in the working environment
can be costly and hazardous. It also
represents a finite supply that can be
exhausted quickly when there’s an unexpected rise in demand.
The costs to address these issues
can be high and difficult to budget for,
An alternative would be to generate
the nitrogen needed on demand. In the
pharmaceutical world, this investment
is easily justified considering the value
of the product, and the potential harm
that introducing contaminated water
can have on consumers.
Nitrogen sparging and blanketing
practices can prevent oxidation in the
manufacturing process. Sparging and
blanketing practices introduce near-pure nitrogen into the water tanks and
maintain a protective layer of nitrogen.
In other words, nitrogen sparges the
water to remove any dissolved oxygen
and CO2. Humid air in the head space
is replaced by pure, inert nitrogen.
This may be maintained by a precise
valve-control system that automatically
adjusts the nitrogen content to maintain
the protective blanket as the tank is filled
or emptied, or by simply having a continuous purge of low pressure nitrogen.
The nitrogen – when bubbled
through water – agitates it and forces
out oxygen and CO2 dissolved in it to
prevent bacterial and algae growth.
This can supplement the use of pumps
that serve this purpose. However, a
500-gallon tank pumping at a gallon
a minute can take up to 10 hours to
churn its contents. Sparging increases
the rate of agitation in the tank, with
sintered stainless steel plates or rods
(called sparging elements) purging the
water on a continuous basis.
In addition to preserving pH and
eliminating microbial growth, deaerated water containing low concentrations of oxygen and carbon dioxide
minimizes corrosion, as well as iron
and copper oxide scale.
SUPPLIED OR MAKE YOUR
There are two ways pharmaceutical
plants may obtain nitrogen. The nitrogen can be received from a supplier as
a gas in high-pressure cylinders or as
a liquid in micro-bulk tanks (dewars)
and bulk tanks. Relying on an outside
supplier, however, is subject to price
increases, rental agreements, hazmat
fees, surcharges and taxes. Delivery of
gas also requires access to the facility
by a third party, and creates a security
situation for the plant to manage.
An alternative to sourcing is to
generate the nitrogen on-site via PSA
(Pressure Swing Adsorption) nitrogen
generators. Payback on such equipment
can be two years or less. Nitrogen can
be generated for eight to 12 cents per
100 cu. ft., while gas-utility companies
charge 50 cents to a dollar or more
per 100 cu. ft. The plant relies on an
energy-intensive cryogenic process to
cool air to extremely low temperatures
How Nitrogen Sparging
and Blanketing Keep
Pharmaceutical Processing Pure
Ensuring continuous supplies of near-pure nitrogen to deoxygenate water can
be a time-efficient and cost-effective way to formulate today’s medicines.
n By David J. Connaughton, Product Manager, Parker Hannifin Corporation, Filtration and