Loss of Carbon Dioxide and Oxygen Buildup in Process Vessels Caused by Circulation of Cleaning-in-Place Solution
MBAA TQ vol. 45, no. 1, 2008, pp.
39-42 |
VIEW ARTICLE
George Agius. JohnsonDiversey Inc., Oakville, ON, Canada.
Abstract
Brewers are increasingly using acidic instead of alkaline detergents to carry
out cleaning in place (CIP) of process vessels. Unlike alkaline detergents,
acidic detergents do not react with carbon dioxide. This means that the tanks or
vessels being cleaned need not be purged of their carbon dioxide, which
considerably shortens the CIP cycle. During CIP, rinse water or detergent
solution is pumped from a CIP solution tank that is open to the atmosphere to
the vessel being cleaned and kept under carbon dioxide pressure. This solution
or rinse water is then returned to the CIP tank or sent to a drain. The carbon
dioxide under pressure dissolves in the circulating CIP solution or rinse water
in direct proportion to the pressure (Henry’s law). On returning to the CIP
solution tank, the dissolved carbon dioxide is released into the atmosphere,
where the partial pressure is close to zero, which can cause a gradual loss of
carbon dioxide from the vessel. Similarly, oxygen can be transported into the
tank from the outside during CIP. Equations have been developed to calculate the
amount of carbon dioxide carried out and oxygen transported into the tank during
CIP. The safety implications for the release of carbon dioxide around the CIP
tank and ways to limit the loss of carbon dioxide and suppress the introduction
of oxygen during CIP are discussed.
Keywords: carbon dioxide, clean in place, equations, Henry’s law, oxygen,
vessel
Figure 1 is in color in this online article.
This online article includes links to websites containing additional
information on:
CO(2) air safety limits:
http://www.cdc.gov/niosh/npg/npgd0103.html
Henry’s law constants:
www.henrys-law.org
CIP:
http://www.johnsondiversey.com/Cultures/en-GB/OpCo/Your+Business/Breweries.htm
Explanations of Henry’s law:
http://www.intute.ac.uk/sciences/reference/plambeck/chem2/p01182.htm and
http://www.wwnorton.com/college/chemistry/gilbert/tutorials/ch8.htm
Síntesis
Muchos cerveceros han comenzado a utilizar detergentes ácidos, en lugar de
los alcalinos, para los sistemas de CIP de tanques de proceso. A diferencia de
los detergentes alcalinos, los de ácido no reaccionan con gas carbónico, lo que
reduce el tiempo del ciclo de CIP al no necesitan ser purgados los tanques del
gas carbónico. Durante el CIP, tanto el agua de enjuague como la solución de
detergente ácida es bombeada (de un tanque CIP abierto a la atmósfera) al tanque
siendo lavado que se mantiene bajo presión de gas carbónico. Una pequeña parte
del gas carbónico presurizado del tanque se disuelve en la solución CIP (o agua
de enjuague) según la ley de Henry y al ser reciclado al tanque CIP (o botado,
cuando necesario) este gas se pierde a la atmósfera, ocasionando una pequeña
pérdida de gas del tanque siendo lavado. Por otro lado, oxígeno en el detergente
o agua de enjuague puede contaminar el gas carbónico del tanque. Se han
desarrollado ecuaciones para determinar la cantidad de gas carbónico removido, y
la cantidad de oxígeno introducido, a los tanques. Se discuten las posibles
consecuencias de la contaminación con gas carbónico en el área del tanque CIP
así como maneras de reducir la pérdida de gas carbónico y controlar la cantidad
de oxígeno introducido al tanque de proceso.
Palabras claves: CIP (limpieza en sitio), ecuaciones, gas carbónico, ley
de Henry, tanques de presión, oxígeno
