Biomass Pellet Production From Acacia Mangium Bark Waste

Date: 10/26/2020 09:10:57 From: wood-pellet-plant.com Clicks:

Raw Material Market in Tropical Countries

Indonesia and other tropical countries such as Brazil and Zaire have a great potential for creating energy from biomass as a substitute for petroleum. Taking into account the large size of Indonesia’s forests and palm oil plantations, coupled with the possibility of using timber and agricultural residues, Indonesia has the ideal conditions for this change. Wood chips, oil palm and other plant biomass provide low cost residues that are renewable and underused, environmentally friendly and potentially capable of generating heat, steam and electric power. Thus, they may constitute an alternative fuel for producing energy. In term of that, one of the potential sources of energy feedstock is Acacia mangium plantation and also its chip mill industry that produced the huge amounts of residues.

Collection of Raw Materials

Waste of A. mangiumwood bark biomass was collected from chip wood industry of PT. Sarana Bina Semesta Alam (SBSA), located at district Muara Kaman, Kutai Kertanegara, East Kalimantan, Indonesia. Before used, Acacia bark waste biomass was chipped, converted into the dust form and airdried until approximately 12% of moisture content.

Fuel Pellet Standard

The international standards of pellet such as ONORM (Austria), SS (Sweden), DIN (Germany), EN (European) and ITEBE (Italy)

1. Physical properties of fuel pellet

Table 1. Chemical properties of A. mangium bark waste biomass and tapioca

Herein this study, we found additives play a major role in wood pellet characteristics and are a subject of major interest as they act as binding agents for the biomass raw material.We found in the less tapioca used, they were easily broken into the small pieces form during pelletizing or producing a low physical quality of fuel pellet. This fact was simillar with the situation that reported on empty fruit bunches used as feedstock for the pellet production. Tapioca was used to bind the small surface of bark dust material. This natural binder was applied to increase physical properties of feedstock such as low density and less surface area that hinder the smooth flow ability of biomass and also to substitute natural function of lignin as binder. Lignin as natural binder on briquette and pellet production was common used and reported previously.

Long size and stable formation of Acacia bark waste fuel pellet in the presence of tapioca and glycerol as binder and additive; (a) 5% tapioca and (b) in the presence of 10% glycerol

Furthermore, we also observed that in the presence of suitable amounts of natural binder tapioca, the density of fuel pellets were good enough to reached 710-770 kg/cm3 to meet the Sweden (SS187120) and Austria (ONORM) standars quality of pellet products (Table 2).

Table 2. Physical properties of A. mangium bark waste biomass fuel pellet in various amounts of tapioca and glycerol

2. Chemical properties and calorific value of fuel pellet

Chemical properties of fuel pellet from Acacia bark biomass was evaluated. Evaluation was done by assesment of moisture content (MC), ash content, volatile matter and fixed carbon of pellet in the presence and absence of tapioca and biodiesel side product, glycerol into the mixtures.

From this trial production we found the distribution of moisture content (MC) of the samples were 6.39% to 8.29% and its was good to meet with the global standard quality of pellet products. Li and Liu reported that a good quality pellet has MC ranging between 6% and 12%. Further, other studies also found that wood pellets having MC ranging between 9% and 14% are most durable and resistant to abrasion.Water has a crucial role in the pelletizing process and, along withlignin content, the MC of the feed is one of the most importantparameters determining pellet durability and itsalso strong influence on heating value, combustion efficiency, and bulk density.

Table 3. Chemical properties of A. mangium bark waste biomass fuel pellet in various amounts of tapioca and glycerol

The ash content, volatile matter dan fixed carbon of fuel pellet produced from Acacia bark were evaluated and the results werecompared to the global pellet standard.The results showed that the ash content of Acacia bark pellets is still quite high at 4.30% - 5.91% (˃1%). The higher ash content of pellet was believed due to silica, the minor element commonly found in tropical climatic plant. Silica is one of the ash compounds other than potassium, calcium and magnesium. Concerning the effect of bark on the quality of biofuel,Filbakk et al reported that thepresence of bark in solid biofuels is related to increased tendency towards sintering duringcombustion and is therefore related to combustion problems. Concerning ash, [18]reported that increasing ash content results to lower heating value of the biofuel, impliesthe risk of sintering and negatively affects processing equipment.

The bark pellets produced has also lower carbon content ranging from 5.01% to 6.20%. The lower fixed carbon of pellets were believed due to high ash and volatile matter of bark material used.The results also showed that the fixed carbon values was positively increased when the number of glycerol added into the mixture increased.

Figure 4. Calorific values of Acacia bark fuel pellet (a) in the presence various amounts of tapioca (Tap), and (b)10% of tapioca and various amounts of glycerol (Gly) as binder and additive

The calorific value of bark pellets were also evaluated to find out the highest energy potency from pelleting process. Among the data collected, we found the highest calorific value was obtained from the mixture of bark dust material and 10% tapioca in the presence of 20% of glycerol to reached 4,383 kcal/kg of heating value. On the other hand, in the absence of glycerol the heating values of bark fuel pellet were only 4,227 to 4,322kcal/kg. The heating value of pellet was increased trends linearly to correspond the increase number of glycerol added into the feedstock. In term of this, again we found that glycerol was clearly affect on the heating value of the pellet. This phenomenon was related with the properties of glycerol that known as a good source of energy and when it was used as an additive in fuel will be able to maintain the burning stability of the fuel, and increasing the heat of the fuel.

Figure 4. Calorific values of Acacia bark fuel pellet (a) in the presence various amounts of tapioca (Tap), and (b)10% of tapioca and various amounts of glycerol (Gly) as binder and additive

Potential sulphur emission released on firing of fuel pellet from A. mangium bark waste biomass was also measured, especially those obtained in the presence of 10% tapiocaand 20% of glycerol into the mixture. The results showed that the sulphur emission level was 0.07%, which still meets the global standard of pellet products (0.07 ≤ 0.08%). The low sulphur levelof bark fuel pellets will positively reduce the emission rate in the air.Due to the low sulphur emission obtained, we also strong believed that bark fuel pellet will be more environmentally friendly compared to coal and other fossil fuel energy.

Conclusion

Finally, we concluded that A. mangium waste bark biomass was potentially used as alternative feedstock for the fuel pellet production. Successful manufacture of fuel pellets from Acacia bark waste biomass was achieved for all combinations studied. The optimum mixture compositions among bark waste biomass, tapioca and glycerol was found at 10% of tapioca used in the presence of 20% glycerol to reached the highest calorivic value 4,383 kcal/kg. Generally, the quality of fuel pellet produced from mix of bark waste biomass, tapioca and glycerol was satisfy to met the international standard quality of fuel pellet such as ONORM standard (Austria), SS (Sweden), DIN (Germany), EN (European) and ITEBE (Italy). Moreover, the modified common animal feed pellet press machine equipped with rotating roller-cylinders was effective used to produced fuel pellet in the small scall production.

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