Structure and pyrolysis behaviour of different coals and relevant model substances

Recently, interest in catalytic gasification of carbon has expanded rapidly. In consequence of the volume and diversity of this interest, there is a need to collate, summarize, and interpret the available information on the mechanism of gasification catalyst action.

The Mechanism of the Catalytic Gasification of Coal Char: A Critical Review

Thermal behaviour during the pyrolysis of low rank perhydrous coals

In this study, the first GPU-enabled ReaxFF MD program with significantly improved performance, surpassing CPU implementations, was employed to explore the initial chemical mechanisms and product distributions in pyrolysis of Liulin coal, a bituminous coal from Shanxi, PRC. The largest coal model ever used in simulation via ReaxFF MD, the Liulin coal molecular model consisting of 28 351 atoms was constructed based on a combination of experiments and classical coal models. The ReaxFF MD simulations at temperatures of 1000-2600 K were performed for 250 Ps to investigate the temperature effects on the product profile and the initial chemical reactions of the Liulin coal model pyrolysis. The generation rates of C-14-C-40 compounds and gas tend to equilibrate within 150-250 ps, indicating that the simulation should allow most of the thermal decomposition reactions complete and the simulated product profiles are reasonable for understanding the chemical reactions of the Liulin coal pyrolysis. The product (gas, tar, and char) evolution tendencies with time and temperature observed in the simulations are fairly in agreement with the experimental tendency reported in the literature. In particular, the evolution trends of three representative products (naphthalene, methyl-naphthalene and dimethyl-naphthalene) with temperature are very consistent with Py-GC/MS experiments. The detailed chemical reactions of the pyrolysis simulation have been generated using VARMD (Visualization and Analysis of Reactive Molecular Dynamics), which was newly created to examine the complexity of the chemical reaction network in ReaxFF MD simulation. The generation and consumption of HO center dot and H3C. radicals with time and temperature are reasonable and consistent both with the evolution of H2O and CH4, and with the detailed chemical reactions obtained as well. The amount of six-membered ring structures was observed to decrease with time and temperature, because of their conversion into 5-membered rings or 7-9-membered rings or even-larger-membered ring structures that will further open and decompose into small fragments. This work demonstrates a new methodology for investigating coal pyrolysis mechanism by combining GPU-enabled high-performance computing with cheminformatics analysis in ReaxFF MD.

Pyrolysis of Liulin Coal Simulated by GPU-Based ReaxFF MD with Cheminformatics Analysis

K2CO3 catalyzed CO2 gasification of ash-free coal. Interactions of the catalyst with carbon in N2 and CO2 atmosphere

Reactions of oxygen containing structures in coal pyrolysis

Steam gasification of German hard coal using alkaline catalysts: Effects of carbon burn-off and ash content

Application of K2CO3 catalysts in the coal gasification process using nuclear heat

Bei den konventionellen Verfahren zur Kohlevergasung wird die Kohle sowohl als Rohstoff fur das Gas als auch zur Erzeugung der notigen Prozeswarme eingesetzt. Neue Verfahrensvorschlage zielen darauf ab, fur den letztgenannten Zweek Hoch-temperatur-Kernreaktoren einzusetzen. Dadurch spart man einen erheblichen Teil der Kohle ein und bewirkt so eine Schonung der Kohlenvorrate sowie eine verminderte CO2-Emission. Fur die technische Durchfuhrung wurde aufgrund von Untersuchungen zur Vergasungskinetik und Warmeubertragung das Konzept eines allothermen Gasgenerators entworfen, in dem die Helium-Warme uber einen Zwischenkreislauf aus dem Kernreaktor auf ein Kohle/Wasserdampf-Wirbelbett durch einen Warmetauscher ubertragen wird, der in das Wirbelbett eintaucht. Bei einer Helium-Temperatur von 950°C konnen in einem Gasgenerator mit einem Wirbelbettvolumen von 318 m3 und einer Warmetauschflache von 4000 m2 ca. 50 t Steinkohle/h vergast werden. Das laufende Forschungs- und Entwicklungsvorhaben hat zum Ziel, im Jahre 1983/84 eine Demonstrationsanlage zu betreiben.

Karl-Heinrich van Heek

Papers

Reactions of oxygen containing structures in coal pyrolysis

Steam gasification of German hard coal using alkaline catalysts: Effects of carbon burn-off and ash content

Application of K2CO3 catalysts in the coal gasification process using nuclear heat

Vergasung von Kohle mit Kernreaktorwärme