| Autor: |
Abotsi, Godfried, Bota, Kofi, Saha, Gautam |
| Zdroj: |
Petroleum Science and Technology; January 1993, Vol. 11 Issue: 2 p327-348, 22p |
| Abstrakt: |
The electrokinetic properties of lignite, subbituminous and bituminous coal particles and their demineralized derivatives have been measured as a function of pH. Compared to the raw coals, demineTalization generally increased the net negative surface charge densities on the coals. Calcium or potassium adsorption (by ion-exchange) onto the demineralized coals was strongly dependent on pH and the surface charge properties of the coals. Metals uptake was very low (0,1-0.4% wt.) in strongly acidic media (∼pHl) but increased dramatically as the net negative charge on the coals was increased by increasing the pHs of the coal suspensions to pH 6 or 10. The reactivities of the calcium- ot potassium-loaded chars in carbon dioxide at 800°C were similarly dependent upon the pHs at which the catalysts were ion-exchanged onto the coals. For the calcium-containing chars, the reactivities increased in the order: pH 6 > "pH 10 > pH 1 while the variation of the gasification rates with potassium loading pH was: pH 6 ∼ pH 10 >> pH I. These findings are attributed to differences in the extent of electrostatic interaction between the calcium or potassium ions and the charged coal surface during catalyst loading from solution. |
| Databáze: |
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