Humidity
Coal fresh, just open the kiln, contains very little moisture, usually less than 1%. The absorption of air humidity is very fast, and win moisture over time, even without getting wet with rain, can reach a content of 5 to 10%, even for charcoal burning well. When not been properly burned coal or when piroleñosos acids and soluble tars have been taken up by charcoal because of rain, as can happen in the graves or burned in Parva increases hygroscopic coal and natural moisture content or balance can go up to 15% or more
The humidity is an adulterant that low calorific value or heat of charcoal. when coal is sold by weight, dishonest traders often maintain a high moisture content, wet with water. Adding water does not change the volume or the appearance of charcoal. For this reason, those who buy coal to prefer to buy bulk or volume in the rough, eg in cubic meters, or by weight, but determining its moisture content through laboratory tests and adjust the price ratio. In small markets are often sold by piece.
It is virtually impossible to prevent the charcoal is something wet with rain, during transport to market, but the storage of coal indoors is a good practice, even if it has been acquired by volume, because the water contained has to eva pores in combustion and represents a direct loss of calorific value. This happens because the water in the form of steam passes in the flow and rarely condenses releasing its heat content, on property that is warming in the oven.
The quality specifications generally limited moisture content to about 5-15%. the gross weight of charcoal. The moisture content is determined drying oven to a sample of coal, and is expressed as a percent of initial weight wet.
Clearly, the charcoal with a high moisture content (10% 0 more) tends to crumble and charcoal produces fine when heated in foundries, which is not desirable in the production of iron.
