Thermal effects, mineral processing

Although only a limited amount of experimental data is available on the effect of temperature, it is apparent that a modest change in temperature has only a minor effect on the process. When a large change in temperature is involved, as may be encountered in thermal oil recovery processes, the temperature effects can be more pronounced. However, at temperatures involved in thermal recovery operations, other formation damage mechanisms, such as mineral dissolution and reprecipitation and colloidal iron plugging, may also be involved. 

This is also important in determining processing behaviour. The thermal conductivity of most mineral fillers is about one order of magnitude higher than that of thermoplastics and their incorporation considerably increases the conductivity of a composite. This effect is beneficial in processing as mouldings can be expected to heat up and cool down more rapidly, leading to shorter cycle times [68]. 

The coefficents of thermal expansion of mineral fillers are considerably less than those of thermoplastic polymers and thus their incorporation can significantly reduce that of a composite material. This is a generally useful effect. High aspect ratio fillers, when aligned by processing, will often give rise to anisotropic effects, leading to problems of warp age [69]. 

A knowledge of minerals and of their formation processes serves as a basis of study of inanimate nature. That knowledge becomes increasingly necessary to the understanding of technological processes involving mineral raw materials. All inorganic materials turned out by present-day industry are the effect of a mechanical, chemical, thermal or pressure action on minerals or their associations called rocks. 

Although SRC-II was basically a thermal liquefaction process, it was most successful using bituminous coals with a high native pyrite content. Iron sulfides are well known to have catalytic properties for coal liquefaction. Recycling part of the ash-minerals-containing bottoms had two beneficial effects (1) it increased the pyrite concentration in the reactor feed, and (2) it increased the residence time for heavy components, thus giving them more time to hydrocrack to distillate products. A block flow diagram of the SRC-II process is shown in Fig. 19.19. 

On the basis of the studies conducted here, it is readily apparent that the presence of minerals can drastically alter the reactivity of the residual char on spent oil shale More detailed quantitative studies of the mineral compositions are necessary in order to be able to assess their importance under typical oil shale processing conditions and will be the subject of future manuscripts from this laboratory. However, at this time, there are several conclusions which can be made. First, the combustion of the char in all six of the shales followed first order kinetics with respect to the oxygen partial pressure and the char available For the western shales this is in agreement with previous works which studied PCM and Anvil Points shales, but it does conflict with the results of Rostam-Abadi and Mickelson (9) who reported second order kinetics for Antrim shale. Secondly, we found that CaO has a catalytic effect on char combustion, most likely due to a chemisorption process And finally we found that Na20, as derived from the thermal decomposition of nahcolite, has a pronounced catalytic effect on the char combustion rate of saline zone shale ... 

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