Nitrogen Blanketing of Edible Oils
Generating nitrogen in-house and on-demand is a safe, cost-effective approach for many tank blanketing and modified atmosphere packaging applications.
Generating nitrogen in-house and on-demand is a safe, cost-effective approach for many tank blanketing and modified atmosphere packaging
During processing, it may be necessary to store foodstuffs such as edible oils in tanks while awaiting further processing or delivery. Because edible oils are sensitive to spoilage by oxygen in air, any oxygen in the tank must be kept to acceptable levels. In a technique called “tank blanketing,” nitrogen is applied to protect the oils against the onset of oxidative rancidity and contamination. The technique is preferred because nitrogen is an inert gas, and, as
such, it offers a natural alternative to using chemical additives to prevent rancidity.
The process offers several different supply options. A newer approach, which is typically more cost effective for most applications, is that of generating nitrogen
on-demand in the processing facility itself. Before discussing on-demand nitrogen generation, it is first helpful to understand more about tank blanketing in general.
Blanketing Basics and Benefits
Process control managers often overlook the potential for chemical tank blanketing to improve facility productivity and product quality. In tank blanketing, a low-pressure flow of nitrogen gas (typically less than 0.1 Bar) with purities of between 97% to 99.9% is introduced above the liquid level of the edible oil to fill the vapor space at the top of the tank with a dry, inert gas. On closed tanks, this creates a slight positive pressure in the tank. Nitrogen is the most commonly used gas because it is widely available and relatively inexpensive, but other gases such as carbon dioxide or argon are sometimes employed.
However, carbon dioxide is more reactive than nitrogen and argon is about ten times more expensive. Maintaining the nitrogen blanket or “pad” helps prevent the ingression of ambient air (which contains water vapour and oxygen) and therefore prevents the onset of oxidative rancidity of the oil. The result is the oil has a longer product life. For example, oxygen and water vapour in air can react with editable oils to eventually form undesirable polymers, acids, aldehydes and ketones. Because nitrogen blanketing removes both oxygen and water vapor from the vessel, it prevents oxidation from ruining the oil.
Considerations for Tank Blanketing Systems
How nitrogen is controlled in tank blanketing applications usually depends on the type of tank used. Typically, tanks with fixed roofs and unsealed tanks
are blanketed while tanks with floating roofs are not blanketed. Nitrogen control methods include continuous purge, pressure control and concentration control. Continuous purge provides a constant flow of nitrogen and is probably the easiest and most common method because a control device is not required. However, nitrogen consumption is high. A sealed tank for pressure control blanketing includes a tank blanketing valve that allows the addition
of nitrogen when the liquid level drops as well as a vent that vents nitrogen when the liquid level rises. A tank equipped with concentration control blanketing uses a feedback loop from an oxygen analyzer back to the nitrogen source that tells the source to cycle on or off. This method economizes the use of nitrogen because it shuts down the nitrogen supply until enough outside air infiltrates to raise the concentration of oxygen above the acceptable limit.
How Much N2 do I need?
We can work with you to correctly size all components including N2 generation equipment to deliver the required flow rate and purity. We also size all auxiliary equipment needed to ensure the N2 blanket is maintained correctly and efficiently.
Click here for our brochure on N2 generators