Experimental Investigation of the Reactivity of Sodium Bicarbonate toward Hydrogen Chloride and Sulfur Dioxide at Low Temperatures

Abstract

The use of sodium bicarbonate (NaHCO 3) as a solid reactant for the removal of acid pollutants in industrial flue gas streams is a simple and effective process solution. Nonetheless, despite its technological maturity, the industrial application of NaHCO 3-based flue gas treatment is still highly empirical. A better knowledge of the heterogeneous reaction process could allow process optimization, resulting in a reduction both in the consumption of reactants and in the generation of solid waste products. In the present study, the reactivity of NaHCO 3 toward HCl and SO 2 was investigated in the temperature range between 120 and 300°C. The key role of thermal activation in determining the reactivity of the sorbent was confirmed. The choice of the optimal temperature for acid gas sorption results from a trade-off: higher temperatures increase the reaction kinetics, but induce the sintering of the activated sodium carbonate. The occurrence of sintering is particularly detrimental for high removal efficiency toward SO 2 , possibly due to the role of the sodium sulfite layer originated by SO 2 sorption. As a consequence, the optimal operating temperature resulted as 150°C for SO 2 and 210°C for HCl. The choice of operating temperature in industrial dry sorbent injection units for acid gas abatement is discussed in view of the present findings.

Hydrogen chloride removal from hydrogen gas by adsorption on hydrated ion-exchanged zeolites

“…Adsorption at low temperatures, offers a very selective and energy-efficient alternative [30,31], however, it is particularly challenging to achieve an efficient HCl removal at high gas velocities and low concentrations. Although the adsorption of impurities such as hydrogen sulfide, carbon monoxide and ammonia have been studied on various adsorbents, including hydroxide and carbonate based adsorbents [32][33][34][35], active carbon [36][37][38], zeolites [34,39,40] and MOFs [31], the adsorptive removal of HCl from hydrogen gas at low temperatures remains almost unexplored, and in particular for zeolites [41,42]. Kim et al carried out HCl adsorption and desorption breakthrough experiments with 13X pellets packed beds at high pressure and gas velocities under nitrogen environment [43].…”

Kinetic Study of Low Temperature Sulfur Dioxide Removal Reaction By Sodium Carbonate Using Random Pore Model

“…Several studies were conducted to investigate the influence of NaHCO3 thermal decomposition to Na2CO3 on SO2 absorption efficiency (Carson 1980, Dal Pozzo et al 2019, Erdos et al 1989, Knight 1977, Mocek &Beruto 1986. These reports indicated that gas temperatures between 120-175 o C showed the best performance for SO2 scrubbing when the initial substance is sodium bicarbonate.…”

New insights on mercury abatement and modeling in a full-scale municipal solid waste incineration flue gas treatment unit

“…For this purpose, NaHCO 3 and powdered activated lignite are directly injected in the flue gas pipe (in-duct treatment), followed by a solid/gas separation step in a bag filter. In particular, NaHCO 3 is related to acid gas removal, while activated lignite is associated to mercury abatement (Dal Pozzo et al, 2019;Pavlish et al, 2003;Srivastava et al, 2001). Considering that the injection of solid reactants is done simultaneously, the analysis of mercury transformations and mercury removal in this section was performed in two steps.…”

“…Nevertheless, it is important to point out that even if a decrease in the process temperature may promote the mercury capture by activated lignite, a too low temperature level may be detrimental for the acid gas abatement. In this case, temperatures around 200°C are required to increase the reactivity of NaHCO 3 and attain a better HCl and SO 2 neutralization (Dal Pozzo et al, 2019). In accordance, process temperature for in-duct and baghouse filtration systems working with activated lignite and sodium bicarbonate should be chosen carefully, depending on the pollutants concentration in flue gases.…”