Fluidized activated carbon process

Recovery of Sulfur Dioxide from Stack Gases as Elemental Sulfur by a Dry, Fluidized Activated Carbon Process... 

The Purasiv HR process is an improved fluidized bed, activated carbon process based on the use of a spherical beaded adsorbent developed by Kureha Chemical of Japan. The process was introduced in the United States and Canada by Union Carbide Corporation in 1978 (Union Carbide Corp., 1983). The unique form of the carbon adsorbent represents the key feature of the process. The beads, which are about 0.7 mm in diameter, create a homogeneous fluidized bed in the adsorption section and a free-flowing dense bed in the desorption section while providing a much higher resistance to attrition than conventional granular or pelletized material. The beads are produced by a proprietary process that involves shaping molten petroleum pitch into spherical particles which are subsequently carbonized and activated under controlled conditions. 

The commercialization by Kureha Chemical Co. of Japan of a new, highly attrition-resistant, activated-carbon adsorbent as Beaded Activated Carbon (BAC) allowed development of a process employing fluidized-bed adsorption and moving-bed desorption for removal of volatile organic carbon compounds from air. The process has been marketed as GASTAK in Japan and as PURASIV HR (91) in the United States, and is now marketed as SOLD ACS by Daikin Industries, Ltd. 

Fluidized-bed powdered activated carbon systems represent another important process. The use of activated carbon for the tertiary treatment of secondary sewage effluents has been used extensively. Powdered carbon is as effective as granular activated carbon for removing the organic impurities from the wastewater. 

The remaining weight of dry sorbents with time is shown in Fig. 2. For every dry sorbent, attrition mainly still occurs in the early stage of fluidization and A1 test on the basis of the weight after 5 hours shows that Als of molecular sieve 5A and molecular sieve 13X presented 2.1 4.0 times higher than those of activated carbon and activated alumina. Therefore, the use of molecular sieve 5A and 13X in a fluidized bed can cause high maintenance cost and problems in the operating the process. 

In the fluidized bed process, attrition caused dry sorbent to be carryover. This mainly occurred in the early stage of fluidization and was highly affected by gas velocity. The amount of attrition of molecular sieve 5 A and molecular sieve 13X were larger than those of activated carbon and activated alumina. In addition, percentage losses of adsorption capacities of molecular sieve 5A and molecular 13X were 14.5% and 13.5%, whereas those of activated carbon and activated alumina were 8.3% and 8.1%, respectively. This is because retention time of molecular sieve 5A and molecular 13X decreased due to elutriation of particle generated from attrition. Also, Ka of activated alumina and activated carbon were the lower than those of Molecular sieve 13X and 5A. Consequently, molecular sieve 5A and molecular 13X could cause high maintenance cost for dry sorbent and problems in the operation of fluidized bed process. 

For waste treatment rather than fermentation for product formation, again few examples of process economics exist in the literature. Those that do, favor fluidization. Badot et al. (1994) described an industrial prototype fluidized bed reactor that competed favorably on an economical basis with activated sludge processes for treating carbon pollution and was estimated to be economically comparable to fixed bed processes for denitrification. Schneeberg (1994) described the successful and economically-sound implementation of fluidization as an upgrade to an existing wastewater treatment plant. The restricted space available for extension of the wastewater plant made fluidization particularly advantageous in this case. 

PuraSiv HR A process for removing solvent vapors from air by adsorption on beaded activated carbon contained in a combined fluidized moving bed. For water-soluble solvents, the gas used for desorption is nitrogen and the process is known as PuraSiv HR, Type N (not to be confused with PuraSiv N) for chlorinated hydrocarbons, steam stripping is used and the process is known as PuraSiv HR, Type S. Developed by Kureha Chemical Company and now marketed by the Union Carbide Corporation. The process was originally known as GASTAK because it was developed by the Taiyo Kaken Company, subsequently acquired by Kureha Chemical Company. It is also marketed by Daikin Industries under the name Soldacs. 

T0228 ECO-TEC, Inc., EnviroMech Gold Biocatalytic Contaminant Degradation T0231 EFX Systems, Inc., Granular Activated Carbon-Fluidized Bed Reactor (GAC FBR) Process... 

Granular Activated Carbon-Fluidized-Bed Reactor (GAC-FBR) Process... 

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