This standard has as its object a method for determining humidity in solid fuels, humidity being understood as free or loosely bound water, which is eliminated from the fuel by heating to 105 -=- 110 °C in a nitrogen stream. The determination is carried out with the aim of reporting with the dry calculation the various analytical results obtained in the execution of tests on solid mineral fuels and derivatives, as well as to obtain the content of volatile materials by deduction from the result of the relevant test. The determination is carried out on the coal sample prepared for the analysis, i.e. made compliant with the environmental conditions by exposure to the air and pulverized until it passes through the sieve 28 UNI 2331, specifically intended for the execution of other analytical determinations, such as ashes, materials volatiles, calorific value, sulphur, etc. Since coal has hygroscopic properties, and is therefore susceptible to varying mass in relation to changes in environmental conditions, together with the execution of this determination, all the different weighings for the individual sample collections necessary for the aforementioned analyzes must also be prepared. ; in this case it is sufficiently valid to base the calculations on a single humidity determination. The humidity dosage must instead be repeated in relation to each deferred sample taking, particularly when there is reason to believe that the intervention of significant variations in relative humidity and environmental temperature could appreciably influence the result. The process is suitable for all types of coals; it is expressly required for those that are subject to oxidation following heating in air.
UNI 7340-1974 history
1974UNI 7340-1974 Solid mineral dyes and derived dyes. Humidity measurement. Nitrogen flow direct gravimetric analysis