Rabu, 03 Agustus 2011
GENERAL OVERVIEW OF CHARCOAL PROPERTIES
The quality of charcoal depends on both wood species used as a raw material and of the proper application of the carbonisation technology. Charcoal produced from hardwood like beech or oak is heavy and strong. Charcoal made from softwood, on the other hand, is soft and light. The density of beech charcoal is 0.45 t/m3a, that of pine charcoal 0.28 t/m3. The bulk density of charcoal does not only depend on the apparent density but also on the size distribution, and is in the range of 180-220 kg/m3. The gross calorific value (GCV) is usually in the range of 29-33 GJ/t.
Good quality charcoal was characterized by Chaturvedi as follows: “[It] retains the grain of the wood; it is jet black in colour with a shining luster in a fresh cross-section. It is sonorous with a metallic ring, and does not crush, nor does it soil the fingers. It floats in water, is a bad conductor of heat and electricity, and burns without flame.”
Charcoal intended for barbecue typically contains 20-30%mass of volatiles, whereas metallurgical charcoal often contains 10-15%m (or even less) volatile matter. Hence, taking ash contents into account, the fixed carbon content is 78-90 %mass.
This carbon is a finely crystalline and practically free of sulfur. Charcoal also contains volatiles that may escape at elevated temperatures (obviously above the charcoal manufacturing process of approximately 400 C), consisting of hydrogen, oxygen, and nitrogen. Ash content is approximately 1.5-5%mass. Charcoal also contains water, the amount being dependent on ambient temperature and humidity. Moisture content varies between 5 %m-8 %mass.
Standards for barbecue charcoal and charcoal briquettes, according to EN 1860.
Charcoal: Carbon (fix), dry basis > 75% Ash, dry basis < 8% Moisture, wet basis < 8% Granulation [d > 80 mm] < 10% [d > 20 mm] > 80% [0 mm < d < 10 mm] < 7% Bulk density > 130 kg/m3
Charcoal briquettes: Carbon (fix), dry basis > 60% Ash, dry basis < 18% Moisture, wet basis < 8% Granulation Suitable for BBQ equipment of EN 1860-1 [d < 20 mm] < 10% Binder Combustion gases cause no health hazards in contact with food. Binder is of food grade quality.
Source : INDUSTRIAL CHARCOAL PRODUCTION, A Development of a sustainable charcoal industry,Presented by FAO