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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

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