Activated soda

The alumina or sodium alurninosiHcate catalysts used to regenerate degraded working solutions lose activity with time as active soda sites are neutralized, but these too can be regenerated. 

Over two hundred dry or wet processes have been proposed for the removal of SO2 gases. Limestone and dolomite find extensive use in many of the desulfurization processes. Activated soda is considered as an attractive and more reactive alternate to limestone. In addition to calcium and sodium based processes, ammonia based, magnesia based, organic based scrubbing systems and catalytic processes have also been proposed for SQ2 removal. Calcium based dry processes have found wide application especially in fluidized bed combustors and in... 

In recent years, considerable attention has been devoted to the understanding of S02-limestone reaction mechanism. Kinetics of this reaction is complicated by the changes in the pore structure, in surface area and by the variations of diffusional effects during the reaction. In this manuscript, emphasis is given to the mechanism of SOj-limestone reaction in a dry system and a detailed review of literature is presented. In the second part, kinetics of S02-activated soda reaction is discussed and applications to flue gas desulfurization are summarized. 

The major drawback of using limestone or dolomite in desulfurization processes is the low conversion of the solid when reacted with SOj. On the other hand, with activated soda ash upto 100% conversion was reported. Soda shows much higher reactivity towards SOj than magnesium and calcium carbonates and it reacts with SO2 at much lower temperatures. 

When NaHC03 is heated to temperatures over 100 C it decomposes and gives a porous reactive product which is called activated soda. 

TABLE 3.1. Physical Properties of Activated Soda Obtained at Different Temperatures (Dogu,1984). (Total Porosity = 0.51)... 

A detailed thermogravimetric study was reported by Kimura and Smith (1987) for the reaction of SO2 with activated soda in the absence of oxygen... 

SINGLE PELLET MOMENT METHOD FOR THE ANALYSIS OF SO2 - ACTIVATED SODA REACTION KINETICS... 

The single pellet moment technique which was originally developed by Dogu and Smith (1975,1976) for the evaluation of diffusion and adsorption parameters in porous solids, was extended to reaction systems and used for the kinetic analysis of SO 2-activated soda reaction (Dogu et al, 1986). In this technique, an inert carrier gas (helium) flowed over two end faces of a cylindrical soda pellet placed into the single pellet reactor (Figure 11). 

Details of the experimental set up were reported elsewhere (Dogu et al, 1986). Sulftir dioxide was introduced as pulses into the stream entering the upper chamber. Part of the carbon dioxide formed by the reaction of SO2 with activated soda left the pellet from the lower face and was detected at the exit of lower flow stream with a TC detector. It was shown that no unreacted SO2 left the pellet from the lower end face at the initial stages of the reaction. The response peaks of CO2 were then analyzed to determine the rate parameters of the reaction system using the moment technique. Other sets of pulse response experiments were repeated with Nj and CO2... 

Dry injection of activate soda (trona or nahcolite) after the combustor is an attractive alternative due to its much higher reactivity at typical flue gas temperatures (150"C). This allows the use of bag filters to be used for collection of particles as well as further sorption of SO2 on... 

Agca,S. (1981) "Reaction of SO2 with activated soda", M.S. Thesis, METU, Ankara... 

Dogu, G., Keskin, A. and Dogu, T. (1988) "Dynamic analysis of changes in diffusion and sorpyion parameters in the reaction of SO2 with activated soda ash". Can. J. Chem. Eng., 66, 605. 

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