Activated carbon adsorption material balances

Yield of Organic Residue. A high yield of organic residue adversely affects the cost of leaching the pulping base from the solid product as well as the thermal balance of the over-all recovery system. However, it was found in the laboratory (using the methylene blue adsorption test) that if the residue were produced at 750°C. or higher, it showed excellent adsorptive properties, similar to commercial activated carbons. The optimum yield of the residue appears to depend therefore on the size of the accessible market for this material. 

In most activated carbon adsorbents, the adsorption kinetic is governed by particle diffusion which generally takes place by two parallel mechanisms pore diffusion (diffusion of the solute molecules within the particle pores) and surface diffusion (diffusion of the adsorbate molecules adsorbed on the pore walls). For this case, the model is defined by the particle material balance ... 

The results of their study are summarized in Table 12-36. The adsorption systems generally consisted of banks of 24" x 24" x 1" panels treating from less than 25% to as high as 100% outside air. The results show that activated carbon can adsorb and retain significant amounts of volatile matter from ambient air. Material balances based on the amount of volatile matter adsorbed, the amount of air processed, and the assumption of 100% efficiency, indicate that the inlet air streams contained 10 to 150 ppb VOCs. The highest levels were observed in geographical areas known to have more polluted air (i.e., Pasadena, San Marino, and downtown Los Angeles). 

During activation the composition of the outlet gas is mainly determined by the quality of the charred material (volatile matter) and by the bed and freeboard temperature. At the operating temperature (800 °C—900 C) used in the experiments the water gas reaction essentially reaches equilibrium, which fixes the gas composition for a given air, fuel, and steam feedrate. For the total mass balance a closure from 95.6% to 102.6% was found. For elementary carbon the deviation was 86.5%—1065%. Further details on the production and influence of the process parameters on the adsorptive capacity are described elsewhere [ 5 ]. 

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