Carbon, activated removal processes

Shiyong, Z., A new promoted potassium carbonate CO2 removal process for ammonia plants using complex activators, Nitrogen, 91 141—150 (1991). 

Careful control of the carbon atom removal process by gasification in CO2 or steam, usually termed burn-off (BO) degree, allows selection of the adsorption characteristics of an AC. Thus, highly activated carbons can be prepared... 

The most common catalyst poisons are derived from traces of solvent carried over fiom carbon dioxide removal process. These simply block the catalyst pores and, providing no suUur or arsenic compounds are used, can easily be removed by washing the catalyst with water to restore activity. If sulfur enters the catalyst bed from any other source it will rapidly poison the methanation catalyst. The low temperature shift catalyst, up-stream of the methanator, usually acts as a very efficient sulfur guard ... 

Active Carbon. The process of adsorbiag impurities from carbon dioxide on active carbon or charcoal has been described ia connection with the Backus process of purifyiag carbon dioxide from fermentation processes. Space velocity and reactivation cycle vary with each appHcation. The use of active carbon need not be limited to the fermentation iadustries but, where hydrogen sulfide is the only impurity to be removed, the latter two processes are usually employed (see Carbon, activated carbon). 

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. 

A final example of application and process layout is shown in Figure 15. In this example the process relies on activated carbon to remove color bodies from a recycled glucose intermediary prior to use in the production of confectionary. The glucose containing the color taint must be mildly heated (to about 70° C), so that the normally solid product becomes less viscous and easier to pump. The syrup is... 

In some cases, the solids themselves are subjected to extraction by a solvent. For example, in one process used to decaffeinate coffee, the coffee beans are mixed with activated charcoal and a high-pressure stream of supercritical carbon dioxide (carbon dioxide at high pressure and above its critical temperature) is passed over them at approximately 90°C. A supercritical solvent is a highly mobile fluid with a very low viscosity. The carbon dioxide removes the soluble caffeine preferentially without extracting the flavoring agents and evaporates without leaving a harmful residue. 

In-tank filtration. Steel finishing electroplating and alkaline cleaning operations use in-tank filters to extend process bath life by removing contaminants in the form of suspended solids. Solids are usually disposed of offsite. Devices such as granular activated carbon filters remove dissolved contaminants, such as organic constituents. 

Kranz MWS A flue-gas desulfurization system based on activated carbon. One carbon bed removes most of the sulfur dioxide. Ammonia is then injected for the SCR process to occur in the second bed, which also removes the residual sulfur dioxide. The carbon is regenerated off-site. Developed by Krantz Company, Germany. In 1986, three plants were operating in Germany. 

The addition of powdered-activated carbon (PAC) to the activated sludge process has received considerable attention, particularly with respect to the removal of specific organics. The applicability of activated carbon in removing specific substrates depends on the molecular weight, solubility, polarity, location of functional groups, and overall molecular configuration. Investigations of PAC systems have centered around process enhancement factors. These include ... 

Activated carbon, used commercially to remove small quantities of H2S from synthesis gas (3), is useful as a follow-on unit to a bulk-removal process. Operation is cyclic, with periodic regeneration of the carbon by steam or inert gas. 

The herbicide 2,4-D is itself a potent phytotoxin. However, a number of structurally related but inactive compounds may be converted by plants to 2,4-D following the activation process and thus act as herbicides. These phenoxyalkanoic acids are co-(2,4-dichlorophenoxy) alkanoic acids. The transformation may be viewed as shown in Fig. 12 as 6-(2,4-dichlorophenoxy)hexanoic acid as the parent compound. The sequence is called /1-oxidation because the steps in which two carbons are removed initially involve the oxidation of the /1-carbon to the aliphatic acid moiety. 

The treatment methods for ruber wastewaters consist of various biological processes, and physico-chemical processes including coagulation, ozonation, activated carbon adsorption, aeration, sulfonation, chlorination, and aeration, and biological nutrient removal processes. The purpose of the treatment is to meet USEPA effluent limitations [4]. 

The three general classifications of acid-gas removal processes are 1) amines, 2) activated hot potassium carbonate, and 3) physical solvents. These systems each have preferred operating ranges, as generally controlled by the acid-gas partial pressure, have different energy requirements, and offer different degrees of selectivity. 

To remove excess CDI and reaction by-products, Beauchamp et al. (1983) dialyzed against water at 4°C. However, the imidazole carbamate groups on mPEG formed during the activation process are subject to hydrolysis in aqueous environments. A better method may be to precipitate the activated mPEG with diethyl ether as in the protocol described for succinimidyl carbonate activation (Section 1.2). 

The HYSEC Process was developed by Mitsubishi Kakoki K. Ltd. and The Kansai Coke Chemicals Company. It has basically the same PSA unit as the UCC Process. It has prefilter beds with activated carbon that remove dirty components. After the main PSA beds, trace amounts of remaining oxygen are removed by a deoxo catalytic converter followed by a zeolitic dehumidifier. A Ni-LaaOj-Rh catalyst, supported on silica, could lower the reaction temperature to about 30°( a. 

---