An investigation of the surface structure of surfactants modified calcium hydroxide and enhancement of dry flue gas desulfurization performance

Calcium hydroxide (Ca(OH)₂) is an inexpensive, widely available desulfurization absorbent with limited calcium utilization in dry flue gas desulfurization. To improve the desulfurization performance of Ca(OH)₂, this study provides a simple and industrially applicable method for modifying Ca(OH)₂ using surfactants. Three surfactants, triethanolamine (TEA), diethylene glycol (DEG), and propylene glycol (PPG), were selected from ten surfactants for modifying Ca(OH)₂. The surfactants were added at mass fractions of 2 wt%, 4 wt%, 6 wt%, 8 wt%, and 10 wt%. The addition of 6 wt% TEA synthesized a Ca(OH)₂ with a specific surface area of 52.59 m²/g and a pore volume of 1.88 cm³/g. The desulfurization test was conducted in a fixed bed reactor at an SO₂ concentration of 800 mg/m³, a reaction temperature of 100 °C, an O₂ concentration of 12%, and a water vapor content of 9%. The high specific surface area Ca(OH)₂ exhibited a breakthrough time of 60 min and a SO₂ adsorption capacity of 84.43 mg/g, more than 4 times that of ordinary Ca(OH)₂. The physicochemical structural changes of high specific surface area Ca(OH)₂ before and after the reaction were characterized using Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS), and the reaction mechanism was analyzed. The results indicated that adding TEA changed the crystal structure and surface morphology of Ca(OH)₂. The Gibbs free energy, surface energy, and polarity of the surfactants affected the quicklime digestion, causing a complexation reaction between Ca²⁺ and TEA, altering the surface structure of Ca(OH)₂.

Graphical abstract