Clean coal technologies and the path to zero emissions

Henderson, Colin B.; Topper, J.M.

doi:10.1016/b978-008044704-9/50183-x

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…It has been estimated that coal-based integrated gasification combined cycle (IGCC) and fuel cell (IGFC) technologies under development can achieve a high power generation efficiency of 45–55% and consequently lead to 20–30% reduction of CO 2 emissions, compared with conventional pulverized coal-fired plants. − IGCC or IGFC is thus expected to be one of the most promising clean coal technologies in the future. We have recently been focusing our research interest on examining the fate of halogens in coal utilization.…”

Section: Introductionmentioning

confidence: 99%

Chlorine Release during Fixed-Bed Gasification of Coal Chars with Carbon Dioxide

et al. 2013

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CO2 gasification of two kinds of coal chars has been carried out using a fixed-bed quartz reactor mainly at 0.1 MPa and 1000 °C to investigate the behavior of chlorine release during char gasification. For this purpose, an Indonesian sub-bituminous coal or an American bituminous coal is first pyrolyzed at 400 °C/min up to 1000 °C, and the resulting char is gasified in situ at 1000 °C with 50 vol % CO2. The Cl contents of the sub-bituminous and bituminous coal chars are 310 and 1300 μg/g-dry, respectively. Conversion of the Cl to gas species increases with increasing char conversion, and there is an almost 1:1 linear relationship between the two. Chlorine distribution depends strongly on char conversion: yield of water-soluble Cl species increases significantly with increasing conversion up to approximately 50 mass %-daf and then levels off, whereas that of water-insoluble Cl increases more remarkably at the latter stage of the gasification. No measurable amounts of Cl2 are detectable, irrespective of the extent of char conversion, but HCl can be detected significantly. The temperature-programmed desorption run of an activated carbon sorbent recovered after gasification also shows that most of the water-insoluble Cl is thermally stable even at a high temperature of 1000 °C. The formation of water-insoluble Cl-functional groups is discussed mainly on the basis of the results of some model experiments and subsequent Cl 2p XPS measurements.

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Section: Introductionmentioning

confidence: 99%

Chlorine Release during Fixed-Bed Gasification of Coal Chars with Carbon Dioxide

et al. 2013

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“…Through worldwide efforts over many years, the integrated gasification combined cycle (IGCC) process has been developed, capable of achieving increased power generation efficiency compared with pulverized coal-fired plants. , However, when coal is fed into the gasification chamber during this process, a portion of the nitrogen present in the coal (coal-N) undergoes pyrolysis (devolatilization) during the primary stage of gasification, and is released in the form of various volatiles, such as tar-N, HCN and NH 3 . − The remainder of the nitrogen is retained in the form of char (char-N) − and subsequently undergoes gasification reactions to form HCN and, predominantly, NH 3 . − As is well-known, the gaseous N-containing compounds evolved in these two stages poison the catalysts used in the gas conversion processes and form NO X during subsequent combustion at the gas turbine. , It is thus important to examine in detail the fates of coal-N and char-N during coal pyrolysis and following char gasification.…”

Section: Introductionmentioning

confidence: 99%

Effects of Solid Residence Time and Inherent Metal Cations on the Fate of the Nitrogen in Coal during Rapid Pyrolysis

Tsubouchi

2014

Energy Fuels

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Six coals with carbon contents ranging from 69 to 80 wt % dry ash-free (daf) were rapidly pyrolyzed at 1300°C under a stream of high purity He in a free fall-type graphite reactor incorporating a graphite filter to control the residence time of coal particles. In this manner, the effects of both residence time and inherent mineral contents on N 2 formation from char-N following devolatilization were examined. At a residence time of zero, 20−30% of the coal-N was released as volatile-N species, such as tar-N, HCN and NH 3 , while <15% was transitioned to N 2 and the remainder (60−80%) was retained in the char. When the residence time was increased to 120 s, the yields of tar-N, HCN and NH 3 were almost unchanged, irrespective of the coal type, although the N 2 yield increased and the char-N decreased with increasing residence times, with the changes in yields of both species being roughly equal. When an Indonesian char sample already devolatilized at 1000°C was pyrolyzed again by applying a slow heating rate of 10°C/min to 1300°C, the nitrogen in the 1000°C char was converted almost exclusively to N 2 . These observations demonstrate that char-N and/or its precursors are the main source of the N 2 in pyrolysis products. The enhancement in N 2 yield observed on increasing the residence time from zero to 120 s increased with increasing inherent Ca or Fe contents in the range of ≤0.3 wt % (dry), although the data were somewhat scattered. Thus, small amounts of naturally occurring Ca and Fe appear to promote N 2 formation from the devolatilized char-N. It appears likely that Ca-or Fe-containing minerals in the coal are partly transformed into CaO or α-Fe, respectively, under the present rapid pyrolysis conditions, both of which enhance the conversion of char-N to N 2 as well as the transition of amorphous carbon to crystallized carbon with turbostratic structures. A linear relationship was observed between the N 2 yield and the proportion of crystallized carbon formed, which may indicate that the yield of one may be predicted from the yield of the other. The catalysis of N 2 formation from char-N without volatile materials through the presence of mineral-derived CaO or α-Fe is discussed herein in terms of solid−solid reactions of these metal particles with heterocyclic nitrogen species in the char.

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Clean coal technologies and the path to zero emissions

Cited by 2 publications

References 2 publications

Chlorine Release during Fixed-Bed Gasification of Coal Chars with Carbon Dioxide

Chlorine Release during Fixed-Bed Gasification of Coal Chars with Carbon Dioxide

Effects of Solid Residence Time and Inherent Metal Cations on the Fate of the Nitrogen in Coal during Rapid Pyrolysis

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