Dry desulfurization

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Dry desulfurization involves thorough mixing and contact between the desulfurizing agent and flue gas, allowing it to react rapidly with SO2 in the flue gas under the action of catalysts and accelerants. Furthermore, inside the reactor, flue ducts, and bag filters, the ultra-fine desulfurization agent powder continuously reacts with SO2 in the flue gas. The reaction is rapid and complete, with the by-product Na2SO4 being produced within 2 seconds. Bybagging, the by-products are recovered and utilized as chemical products. This reaction has a high desulfurization efficiency; when the chemical reaction ratio is 1:1, the desulfurization efficiency exceeds 95%. Moreover, the desulfurizing agent is injected only once, without the need for recycling. Desulfurization mechanism: Baking soda (NaHCO3) is used as the desulfurizing agent, which is activated under the influence of high-temperature flue gas, resulting in the formation of a microporous structure on its surface, similar to popcorn popping. The flue gas inside the ducts comes into full contact with this activated desulfurizing agent, leading to chemical reactions; as a result, SO2 and other acidic substances in the flue gas are absorbed and purified. The desulfurized and dried Na2SO4 byproduct then enters the bag filter along with the airflow and is captured there. Main reactions: 2NaHCO3(S) = Na2CO3(s) + H2O(g) + CO2(g) (1) SO2(g) + Na2CO3(s) + 1/2O2 = Na2SO4(s) + CO2(g) (2) Side reactions: SO3(g) + Na2CO3(s) = Na2SO4(s) + CO2(g) (3) When the temperature exceeds 140°C, ultra-fine baking soda undergoes spontaneous reactions: Baking soda starts to react at temperatures above 85°C, and at temperatures above 140°C it undergoes a rapid popcorn-like reaction, changing from a powder to fluffy popcorn particles; this greatly increases its surface area and its reactivity, **accelerating the reaction rate. The reaction product Na2CO3 is the actual reactant that reacts with SO2 and HCl. Through the decomposition reaction, the internal surface area of Na2CO3 increases, enhancing its reactivity. Once activated, baking soda exhibits high reactivity, and the following reactions occur in flues or reactors: SO2 + 2NaHCO3 + 1/2O2 → Na2SO4 + 2CO2 + H2O (1); SO3 + 2NaHCO3 → Na2SO4 + 2CO2 + H2O (2); HCl + NaHCO3 → NaCl + CO2 + H2O (3); HF + NaHCO3 → NaF + CO2 + H2O (4). The reactions between the acidic components in the flue gas (SO2, SO3, HCl, and HF) and the adsorbent (NaHCO3) mainly take place in the flues or reactors upstream of the bag filter, where the conditions for heat and mass transfer are optimal. The principle of dry desulfurization using calcium hydroxide is the same. The waste generated causes relatively little secondary pollution.