Effects of Heating Temperature and Moisture on Indirect Gasification of Rubber Wood in Closed Gasifier Chamber

Rural area in Indonesia of which electrification ratio is still low has a strong demand for off-grid electric power supply. On the other hand, Indonesia is a leading natural rubber production country and these rubber wood trees are cultivated in vast plantation farms. A rubber wood tree is woody biomass resource which can be stably supplied because a lot of trees aged more than 25 years are logged and nursery trees are planted constantly. Woody biomass is burned directly as solid fuel and the generated thermal energy can be applied only for room heating or cooking. Otherwise, direct conversion of biomass to electric energy requires a large scale equipment such as a boiler and a steam turbine, whereas gasified woody biomass can be easily handled and can have wide application. A closed gasifier chamber which was kept vacuum and fulfilled with gas yield during gasification was recently developed by the authors for indirect gasification. It was confirmed that generated gas by the gasifier is clean and can be directly used to drive an engine generator to supply electricity. In this study, planer dust of rubber wood is used as gasification feedstock for indirect gasifying in the closed gasifier chamber, and effects of heating temperature and moisture content on gasification performance are discussed to examine characteristics of the closed gasifier chamber in details.

Effects of Secondary Chamber on Gas Yield by Pre-Vacuum Chamber Pyrolysis of Rubber Wood

Global warming awareness criticizes further usage of fossil fuels and insists promotion of renewable energy usage. Additionally, many people in rural areas of developing countries cannot access electricity. To solve this sort of energy crisis including global warming, current authors developed a proto-type of a pyrolysis plant equipped with a prevacuum chamber, which can be used to produce combustible gases for an engine generator in rural areas where people cannot access electricity. The plant is simple and easily maintained in consideration of special conditions that a rural area can receive very few maintenance service, technical assistance, and supply of spare parts. However, gas yield obtained by the proto-type of plant was around 20 wt% of feedstock. One way to enhance gas yield from this proto-type of plant is to utilize reaction of secondary tar cracking. This research work aims to examine possibility of gas yield enhancement keeping a simple structure of the proto-type of plant and using a simple technique of secondary tar cracking. Two tar cracking methods are examined: one is homogeneous tar cracking and the other is heterogeneous tar cracking using catalysis. In the homogeneous tar cracking, pyrolysis gases must be heated up to 650oC to 700oC and in the heterogeneous tar cracking, wood char is used as catalysis, because wood char is byproduct of pyrolysis. It is concluded that the homogeneous tar cracking is quite unlikely in the secondary chamber, but on the other hand, heterogeneous tar cracking using wood char can produce 30 wt% of gas yield from 1 kg of feedstock.

Numerical Analysis on Wood Pyrolysis in Pre-Vacuum Chamber

In the previous experimental work, a new technology system for wood pyrolysis was developed to aim at mitigating climate change, global warming, and energy crisis as well as enhancing low electrification in rural areas in developing countries. The new technology system equipped with a pre-vacuum chamber requires low cost and less maintenance. However, large wood pyrolysis in the pre-vacuum chamber is rather complicated. To obtain a good understanding of the previous experimental results, a numerical analysis taking account of heat-mass transfer and chemical reaction is carried out. Two-step general reaction model is proposed for the numerical analysis. The first stage is volatile and char formation from the wood pieces and the second state is decomposition of the volatile to five species including vapor of tar. In this analysis, chemical formulae of the volatile and the tar are successfully identified hypothetically. The results obtained by this numerical analysis can explain the experimental results reasonably and provide useful information about time evolution of volatile formation, temperature change in pre-vacuum chamber with time, and species mole concentration decomposed from the volatile.

Wood Pyrolysis in Pre-Vacuum Chamber

Climate change, global warming, and energy crisis are critical issues to be solved urgently in a global framework. Alternative energy and renewable energy technologies must be quickly developed to be substituted for fossil fuels like oil, gases, and coal. USA, UE, and Japan invested huge budgets to develop biomass renewable energy technology. Their target is to develop a commercial base large-scaled plant. On the other hand, in developing countries, especially in rural areas, people who can access electricity is still less than 70%, To decelerate or prevent global warming and improve electrification in rural areas, a new technology for wood pyrolysis, which requires low manufacturing cost and less maintenance, and of which gases are directly applicable to the gas engine generator, is developed in a laboratory scale. This paper reports the performance of this new plant and effects of several parameters on the performance. It is concluded that the new technology is quite feasible in rural areas, and upgrading of the plant is easily possible.