Self-heating Food Containers

The heat of hydration of quicklime has been used to produce a range of selfheating food containers [32.48]. The food can is packed in a larger can and medium to low reactivity quicklime, in the form of fine grains (e.g. 2 to 5 mm), is packed into the annular space around the inner can. Small, sealed bags of water are placed on top of the lime. The outer container is sealed to the inner using an annular lid. 

When hot food is required, the water bags are punctured, releasing the water on to the quicklime. After 5 to 10 min. the food in the inner can is sufficiently hot to be eaten. The cans are used by emergency services and the military in situations when the convenience of the cans outweighs their extra mass, bulk and cost. 

The production of lime and limestone inevitably results in a number of environmental effects. A responsible producer will, therefore, have an environmental management system, which addresses the relevant areas listed in Table 33.1, to ensure that appropriate actions are taken to minimise the environmenteil impact of his operations [33.1,33.2]. 

In the context of the production of lime and limestone the following effects merit detailed consideration  

These effects are considered briefly in the following sections for greater detail on individual effects, the reader is referred to the standard reference texts. 

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S. Aitoh, Resemch and Development of a Self-heating Food Container Using Lime , Proc.Intemational Lime Congress, Rome, 13-14 Sept. 1990. 

The energy of a corrosion reaction is used to prepare a meal that has a self-contained heat source. The heat comes from a packet containing a powder made of a magnesium-iron alloy and a separate packet of salt water. When the contents of the two packets mix, the reaction between the metal, salt water, and oxygen in the air releases enough energy to heat the food by 100°C in 15 minutes. The process is used to provide heated food or beverages to military personnel, truck drivers, and sports fans. 

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