Bamboo charcoal and active carbon are new products developed in recent years. Bamboo being of special microstructure possesses extreme absorbing and other special capacities after carbonization. Their uses in the areas of new technology are of importance.
Variety of Bamboo Charcoal: There are many kinds of bamboo charcoal. In line with their origin, bamboo charcoal can be divided into two parts: raw bamboo charcoal and charcoal stick of chips. Raw bamboo charcoal is made of small sized bamboo, old bamboo, and bamboo tops, roots, which are not fit for making other bamboo products. Charcoal stick of chips is made of residue from bamboo processing industries. In the process of making different kinds of industrialized products, there will be residue, which should be broken in chips, dried, and pressed into sticks before carbonization.
Charcoals are of different shapes: cylinders, pieces, chips and powder. In line with the temperature of carbonization charcoals can be divided into three groups: charcoal of low, medium and high temperature. Physical and mechanical properties of charcoal differ due to different temperature of carbonization. Charcoal for regulating humidity is made at temperature of 600 degrees Celsius, that for absorbing is at 700 – 800 degrees Celsius, and for higher electric conductivity is higher than 1000 degrees Celsius. According to their uses charcoal is defined as fuel, water purifier, for cooking, for improving soil, for regulating room humidity, for preservation of vegetables, fruits and flowers, for deodorizing, for conducting electricity etc.
Process of making bamboo charcoal
Bamboo is an organic matter with high polymer content, composed of cells of different shapes and properties. The process of making bamboo charcoal is the process of heating and resolution, which can be divided into four stages according to the change in temperature, show in the adjoining table.
Methods of Charcoal making: There are two different methods of charcoal making: dry distillation (pyrogenic decomposition), and direct kiln burning.
The main equipment for pyrogenic decomposition is a cauldron for distillation. Bamboo material should be pre-dried to decrease the water content to +/- 20% before loading into the cauldron for pyrogenic decomposition. The mixed steam gas is to be processed in jar-separator and in condenser for retrieving bamboo vinegar liquid and bamboo tar. In this process, the oxidation of bamboo material is lower, and the rate of production is higher.
In the process of direct kiln burning, the heat resulting from fuel burning curls up to the top of the kiln and spreads in the kiln. Most of the heat moves about in the upper part of the kiln, the rest of it radiates on all sides, step by step goes down to dry and pre-carbonize the bamboo material. In the process of carbonization, a small part of bamboo material is being oxidized and burnt, raising the temperature in the kiln and removing volatile matter. The smoke and steam moves in circles, and regulating the temperature in the kiln. Thus the canonization and refining process is complete producing bamboo charcoal fine and close in texture. In this process the bamboo material undergoes stages of pre-drying, drying, pre-carbonizing, carbonizing, refining and natural cooling. The temperature differs in different stages. The temperature of refining stage influences the density and electric conductivity of charcoal greatly. The rate of production through this method is low and the quality of charcoal is not stable.
Utility
- Bamboo Charcoal: Bamboo charcoal is used as water purifier (drinking water, sewage and industrial water treatment), air purifier, medical applications, deodorizing agent, soil improvement, etc
Bamboo Active Carbon: Bamboo active carbon can be used for water and gas treatment, refining coarse sugar, refining wines and edible oils, pharmaceuticals and cosmetic applications, filters in atomic reactors, improving soil through nitrogen fixation, as electrodes in microelectronic technology, etc.
Charcoal is next only to firewood in terms of meeting the energy needs of rural communities. The decreasing availability of wood and the greater need for its sustainable use necessitate the use of alternative sources of energy. Bamboo charcoal is one such source. It has a high calorific value and can be produced using simple equipment that can be made locally. Honeycomb briquettes extruded using powdered bamboo charcoal (calorific value of 26-29 MJ/kg) and the producer gas generated during char production (average calorific value 4,520 kJ/nm3) is both good sources of energy. In one hour, a thermal gassifier can produce 100 kg of charcoal from 400 kg or bamboo. Therefore, in 24 hours, 2.5 tons of charcoal can be produced from about 10 tons of bamboo. This translates into an annual production of 625 tons of charcoal using 2,500 tons of bamboo, assuming 250 days of operation. A supply chain set up to service this scale of production would financially benefit a large number of producers, while reducing deforestation and increasing energy security.
