Enhancement of lignite char reactivity to steam by cation addition

Hippo, E.J.; Jenkins, Robert G.; Walker, P.L.

doi:10.1016/0016-2361(79)90150-9

Cited by 130 publications

(50 citation statements)

References 15 publications

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“…Furthermore, samples A, B, and D presented much lower carbon yields at 120 minutes activation, around 30%, compared with those of samples C and E, around 70%, indicating that samples A, B, and D were more reactive with steam than samples C and E. This was presumably attributed to the intrinsic composition and structure of the unburned carbon samples, such as the pore size distribution, and mineral matter (Hippo, et al, 1979). It was reported that carbonaceous materials with large percentage of meso-and macropores were more reactive.…”

Section: 27mentioning

confidence: 91%

“…This was because the meso-and macropores could, at least in part, result in a better utilization of the surface area in the micropore for activation. Some elements present in the mineral matters in unburned carbons, such as Fe, K and Ca, were expected to catalyze the activation reactions, and hence, lead to an increase in reactivity (Hippo, et al, 1979). ) because of its low resolution (Patrick, 1995;Rouquerol, et al, 1999).…”

Section: 27mentioning

confidence: 99%

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Development of Activated Carbons From Coal Combustion by-Products

Schobert¹,

Maroto‐Valer²,

Lü³

2003

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The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons.The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor.LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N 2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygenIn addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m 2 /g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be inferred from their physical and chemical properties. The developed porosity of the activated carbon was a function of the oxygen content, porosity and H/C ratio of the parent unburned carbon feedstock. It was observed that extended activation times and high activation temperatures increased the porosity of the produced activated carbon at the expense of the solid yield.

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Section: 27mentioning

confidence: 91%

Section: 27mentioning

confidence: 99%

Development of Activated Carbons From Coal Combustion by-Products

Schobert¹,

Maroto‐Valer²,

Lü³

2003

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“…CaO and K20 account for only 2.6 wt% and 2.1 wt%, respectively, of the ash . Hippo et al (1979) compared the catalyzed reactivity of steam gasification for these latter two catalysts at the same loading and the same reaction conditions. It was found that Ca and K exhibited a greater catalytic effect than Fe (the ratio of the catalyzed reactivities to Fe were about 1.4 and 1.8, respectively), and Mg exhibited significantly less catalytic activity than Fe.…”

Section: Methodsmentioning

confidence: 99%

Reactivity of young chars via energetic distribution measurements. Final report, 1 September 1990--31 December 1994

Calo¹,

Zhang²,

Lu³

et al. 1996

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“…It is well recognized that lignite is enriched with carboxyl groups, which is often combined with alkali and alkaline metals (AAMEs), especially with calcium [28,33,34]. This form of calcium is highly or atomically dispersed in lignite.…”

Section: Model Developmentmentioning

confidence: 99%

“…However, it is well known that the char gasification process is mechanistically associated with the formation of active site and intermediate during gasification. The active site and intermediate in a char, although difficult to quantify and track, is a key factor for determining the gasification rate [28][29][30]. Lignite char is generally the most reactive among the chars derived from a whole spectrum of coal.…”

Section: Model Developmentmentioning

confidence: 99%