Utilization of oil palm ash (OPA) as an absorbent for the removal of sulfir dioxide (SO2) from flue gas

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Date
2005-06
Authors
Zainudin, Nor Fatiha
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Abstract
Oil palm ash (OPA) was utilized as an absorbent for dry-type flue gas desulfurization (FGD). The preparation of the absorbent was conducted with two different methods; water hydration and steam hydration. Other chemicals such as calcium oxide (CaO), calcium hydroxide (Ca(OHh and calcium sulfate (CaS04) were added during the synthesis of the absorbent. The absorbent prepared with water hydration gave a higher desulfurization activity than the steam hydration method. The absorbent prepared with an optimum hydration parameters has a surface area of 88.3 m2/g, was obtained using 5 g CaO, 15 g oil palm ash (OPA), and 1 g CaS04 at the hydration period of 24 h. This absorbent was used as the reference absorbent for desulfurization activity test. The characteristic of prepared absorbent in terms of absorbent surface area, average pore diameter, chemical composition and surface morphology were investigated in order to check their influence on the desulfurization activity. The results showed that the increase in absorbent surface area increases the desulfurization activity. In contrast, the absorbent average pore diameter gave no specific trend towards the desulfurization activity. Nonetheless the absorbent prepared using water hydration with CaO as the starting material produced an absorbent with average pore diameter of 5 to 14 nm (mesopore size). The chemical composition of the prepared absorbent showed that it consists of some complex compounds as a result of combination reaction of different basic compounds present in oil palm ash (OPA) and the calcium sources materials. The surface morphology of the absorbent revealed the existence of different kind of fine materials (such as calcium silicate hydrate, calcium aluminum silicate hydrate and potassium aluminum silicate) within the absorbent pores. The reference absorbent was subjected to the synthetic flue gas mixtures where the reactivity was compared to the raw materials, and it showed that the absorbent easily outperform the desulfurization activity of the un-treated raw materials. The absorbent was also subjected to different desulfurization reaction parameters. The time to maintain 100% sulfur dioxide (S02) removal was increased at a high reaction temperature (up until 300°C), but the reaction was maintained a low temperature (below 100°C) for the study of other parameters effects. The presence of water vapors as well as nitrogen oxide (NO) in the stream gas significantly affected the desulfurization activity of the absorbent. The presence of NO was not significant if the reaction was carried out in a dry condition (absence of relative humidity). The 100% sulfur dioxide (S02) removal can be achieved until 50 min with relative humidity of 75% at reaction temperature of 80°C. As a result, the spent-absorbent consists of sulfated compounds such as calcium sulfate hydrate (CaS04.H20) and potassium sulfate hydrate (K2S20 3.H20).
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Oil palm ash (OPA) was utilized as an absorbent for , dry-type flue gas desulfurization (FGD).
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