Recycling of marble waste for desulfurization of flue gas accompanied by synthesis of gypsum and PoP

Abstract

The suitability of marble waste (MARWAS) slurry as an alternative sorbent to limestone for wet flue gas desulfurization (WFGD) was studied by absorbing SO2 from air-SO2 mixtures in a semi-batch bubble column reactor. The concentration of SO2 at the inlet to- and exit from the reactor was measured using an infrared SO2 analyser (ZJRFAY36, Fuji, Japan). Percent removal efficiency (PRE) of SO2 and slurry saturation time (SST) were determined as functions of pertinent process variables. The maximum values of PRE and SST obtained were 99.8% and 40.83 min, respectively, for a slurry depth of only 3 × 10−2 m. Product gypsum was calcined to Plaster of Paris (PoP) using a modified electric furnace and characterized using XRD, TGA, and SEM analyses. A design criterion for the continuous absorption of SO2 using two semi-batch absorbers have been proposed that allows complete conversion of MARWAS and more than 99% PRE of SO2. The synthesized gypsum can be used to adjust the desired properties of cement products while the PoP as a construction material. A comparison of PRE of SO2 using MARWAS and limestone slurries showed its maximum value to differ by approximately± 1%. MARWAS slurry can, therefore, be favorably employed for the WFGD.