Coal, adsorption

ABSTRACT Experimental study was done on the effects of electromagnetic fields on gas adsorptive constant a/b of different coal rank. The research results show that the electromagnetic fields almost have no effects on gas adsorptive constant a, but can reduce adsorptive constant b obviously. Adsorptive constant b decreases with voltage and frequency of electromagnetic field exalting. The exerted electromagnetic fields can reduce the capability of coal adsorption to gas and gas adsorptive volume. 

When alternative electromagnetic field is exerted in adsorptive step, typical experimental result is shown in Figure 2, Figure 3, Figure 4 and Figure 5 in which y axis represent gas adsorptive quantity calculated indirectly from every ton of coal adsorptive quantity and x axis represent adsorptive balance pressure. Figure 2 and Figure 3 show the adsorptive results which the volt of alternative... 

Coal adsorption to gas is physical adsorption. Under high pressure and at certain temperature it is follow the famous 1 angmuir equation as... 

Coal adsorption to gas under electromagnetic field is physical adsorption. The gas adsorptive capacity... 

Based on Fig.l, consider that the adsorption interface is controlled by capillary cohesion (i.e. surface tension) in the process of coal adsorption of nitrogen, the following can be obtained ... 

White, W.E., et al., Changes in surface area, pore structure and density during formation of high-temperature chars from representative US coals, Adsorpt. Sci, Technol., 7(4). 180-209 (1991). 

Adsorption. Adsorption involves the transfer of a component onto a solid surface. An example is the adsorption of organic vapors by activated carbon. Activated carbon is a highly porous form of carbon manufactured from a variety of carbonaceous raw materials such as coal or wood. The adsorbent may need to be... 

The general type of approach, that is, the comparison of an experimental heat of immersion with the expected value per square centimeter, has been discussed and implemented by numerous authors [21,22]. It is possible, for example, to estimate sv - sl from adsorption data or from the so-called isosteric heat of adsorption (see Section XVII-12B). In many cases where approximate relative areas only are desired, as with coals or other natural products, the heat of immersion method has much to recommend it. In the case of microporous adsorbents surface areas from heats of immersion can be larger than those from adsorption studies [23], but the former are the more correct [24]. 

Fig. 4.2 Adsorption isotherms of benzene at 25°C on (1) a charcoal from anthracite coal, activated to 56% yield (2) an activated coconut charcoal. (After Cadenhead and Everett.)...

The swelling of the adsorbent can be directly demonstrated as in the experiments of Fig. 4.27 where the solid was a compact made from coal powder and the adsorbate was n-butane. (Closely similar results were obtained with ethyl chloride.) Simultaneous measurements of linear expansion, amount adsorbed and electrical conductivity were made, and as is seen the three resultant isotherms are very similar the hysteresis in adsorption in Fig. 4.27(a), is associated with a corresponding hysteresis in swelling in (h) and in electrical conductivity in (c). The decrease in conductivity in (c) clearly points to an irreversible opening-up of interparticulate junctions this would produce narrow gaps which would function as constrictions in micropores and would thus lead to adsorption hysteresis (cf. Section 4.S). 

Fig. 4.27 Swelling and low-pressure hysteresis in the adsorption of n-butane on compacts of coal at 273 K. The following are plotted against the relative pressure (a) the amount adsorbed (b) the percentage increase on length (c) the decrease —Ajc in electrical conductivity. The curves for ethyl chloride were very similar to the above curves.

Fig. 5.14 Adsorption isotherms of water on carbon in (a) to f) with corresponding isotherms of nitrogen in (a), (c) and (J), and of benzene in (f>). (a) Charcoal (b) active carbon AY8 (c) charcoal A (J) charcoal (e) a coal tar pitch kilned at 1200°C (/) a charcoal (S600H). (Redrawn from the diagrams in the original papers.)...

Fig. 4. Coal gasification process. PSA = pressure-swing adsorption.

In carbon adsorption, contaminants are physically attracted or adsorbed on the surface of the carbon. Adsorption capacities are high for carbon because its porous nature provides a large surface area relative to its volume. Activated carbon is prepared from lignite, bituminous coal, coke, wood, or other organic materials such as coconut shells. 

Adsorption. Adsorption (qv) is an effective means of lowering the concentration of dissolved organics in effluent. Activated carbon is the most widely used and effective adsorbent for dyes (4) and, it has been extensively studied in the waste treatment of the different classes of dyes, ie, acid, direct, basic, reactive, disperse, etc (5—22). Commercial activated carbon can be prepared from lignite and bituminous coal, wood, pulp mill residue, coconut shell, and blood and have a surface area ranging from 500—1400 m /g (23). The feasibiUty of adsorption on carbon for the removal of dissolved organic pollutants has been demonstrated by adsorption isotherms (24) (see Carbon, activated carbon). Several pilot-plant and commercial-scale systems using activated carbon adsorption columns have been developed (25—27). 

Activated carbon is an amorphous solid with a large internal surface area/pore strucmre that adsorbs molecules from both the liquid and gas phase [11]. It has been manufactured from a number of raw materials mcluding wood, coconut shell, and coal [11,12]. Specific processes have been developed to produce activated carbon in powdered, granular, and specially shaped (pellet) forms. The key to development of activated carbon products has been the selection of the manufacturing process, raw material, and an understanding of the basic adsorption process to tailor the product to a specific adsorption application. 

Table 4 shows the composition of a typical British natural gas, including the components as relative pressures, and their potential for adsorption on a coal based pellet (SSC 207EA 4mm). 

Granular media filtration is used for treating aqueous waste streams. The filter media consists of a bed of granular particles (typically sand or sand with anthracite or coal). The anthracite has adsorptive characteristics and hence can be beneficial in removing some biological and chemical contaminants in the wastewater. This material may also be substituted for activated charcoal. 

Adsorption is the process by which liquid or gaseous molecules are concentrated on a solid surface, in this case activated carbon. This is different from absorption, where molecules are taken up by a liquid or gas. Activated carbon can made from many substances containing a high carbon content such as coal, wood and coconut shells. The raw material has a very large influence on the characteristics and performance activated carbon. 

The term activation refers to the development of the adsorption properties of carbon. Raw materials such as coal and charcoal do have some adsorption capacity, but this is greatly enhanced by the activation process. There are three main forms of activated carbon. 

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