Search

A series of iron oxide sorbents with novel structures of three-dimensionally ordered macropores (3DOM), ranging in size from 60 to 550 nm, were fabricated and creatively used as sorbents for the removal of H2S at medium temperatures of 300-350 °C. Evaluation tests using thermogravimetric analysis (TGA) and a fixed-bed reactor showed that, in comparison to the iron oxide sorbent prepared by a conventional mixing method, the fabricated iron oxide sorbent with a 3DOM structure exhibited much higher reactivity and efficiency, as well as high sorbent utilization with low regeneration temperature. The excellent performance of 3DOM iron oxide as a sulfur sorbent is attributed to its special texture, i.e., the open and interconnected macroporous, large surface area, and nanoparticles of iron oxide, which are revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption techniques. The investigation results of the pore effect on the performance of the sorbent show that sorbents with pores size around 150 nm in diameter revealed the best performance. The reason is that pores of this size are large enough to allow gas to pass through even if the channel is partially blocked during the reaction process while remaining a large surface area that can provide more active sites for the reaction.

Understanding the conversion of coal-N during gasification is an important part of the development of gasification-based power generation technologies to reduce NO(x) emissions from coal utilization. This study investigated the conversion of coal-N in the presence of NO during the gasification of three rank-ordered coals and their chars in steam and low-concentration O(2). Our results show that NO can be incorporated into the char structure during gasification. The inherent char-N and the N incorporated into the char from NO-char reactions behave very similarly during gasification. During the gasification in steam, significant amounts of HCN and NH(3) can be formed from the incorporated N structure in char, especially for the relatively "aged" chars, mainly due to the availability of abundant H radicals on the char surface during the gasification in steam. During the gasification in 2000 ppm O(2), the formation of HCN or NH(3) from the N structures in char, including those incorporated into the char from the NO-char reactions, was not a favored route of reaction mainly due to the lack of H on char surface in the presence of O(2).