Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: devolatilisation

Sortuj według:

Ogranicz wyniki do:

Prediction of coking dynamics for wet coal charge

Kardaś D., Polesek-Karczewska S., Ciżmiński P., Stelmach S.

Chemical and Process Engineering

2015

Vol. 36, nr 3

291--303

A one-dimensional transient mathematical model describing thermal and flow phenomena during coal coking in an oven chamber was studied in the paper. It also accounts for heat conduction in the ceramic oven wall when assuming a constant temperature at the heating channel side. The model was solved numerically using partly implicit methods for gas flow and heat transfer problems. The histories of temperature, gas evolution and internal pressure were presented and analysed. The theoretical predictions of temperature change in the centre plane of the coke oven were compared with industrialscale measurements. Both, the experimental data and obtained numerical results show that moisture content determines the coking process dynamics, lagging the temperature increase above the water steam evaporation temperature and in consequence the total coking time. The phenomenon of internal pressure generation in the context of overlapping effects of simultaneously occurring coal transitions – devolatilisation and coal permeability decrease under plastic stage – was also discussed.

In-situ observations of devolatilisation of coal

Strezov V., Lucas J. A., Osborn S. R., Strezov L.

Polish Geological Institute Special Papers

2002

Vol. 7

253-258

Coal devolatilisation phenomena were observed in-situ during heating. A single particle of coal of approximately 1 mm diameter was placed on a stainless steel strip heated by an alternative current source. The behaviour of the coal particle was recorded at 100 times magnification through an arrangement of a long focal distance microscope attached to a CCD camera. The two different coal types examined (thermal and coking coal) exhibited significant differences during heating. At about 460oC, during the plastic stage, the coking coal showed rapid swelling and formation of bubbles within the liquid. Unlike the coking coal, the thermal coal showed very little swelling, although devolatilisation (predominantly tars for both coals) was taking place. The volatiles were diffusing to the surface of the particle through the pores in the char, without any significant swelling. At temperatures above 600oC, significant shrinking was observed with the coking coal, while in both samples, evolution of hydrogen was monitored. These observations were compared to the measured specific heats for these coals. The specific heats showed significant differences between the samples associated with a very complex behaviour following the onset of softening. While the coking coal exhibited predominantly exothermic reactions coinciding with the observed swelling phenomena, the thermal coal showed a sequence of endothermic and exothermic reactions. The changes in the specific heats also correlated well with the observed evolution of hydrogen (and shrinking for the coking coal) at higher temperatures.