A novel method for gas-solid contact visualization and efficiency quantification in dry fixed-bed desulfurization

Abstract

A novel method for the visualization of gas–solid contact states and the quantitative evaluation of contact efficiency in the dry fixed-bed desulfurization process is proposed in this study. This method utilizes the chromogenic properties of phenolphthalein (PP) on the surfaces of various sodium salt products during the sodium bicarbonate dry desulfurization process, enabling visualization of gas–solid contact status. Samples of desulfurization products are photographed, and ImageJ software is employed for image processing to calculate color residual rates, thereby quantifying gas–solid contact efficiency. The specific operating conditions that produced the best visualization effect of gas–solid contact states were determined through experimentation, including: an appropriate PP solid content of ≤ 0.336 % for ultrafine NaHCO3 with D90 = 6.14 μm; a steam volume ratio of approximately 13.94 % to 24.46 %, a temperature inside the reactor of 110 °C–175 °C. Moreover, the fading effect of the indicative sodium-based absorbent was consistent across SO2 concentrations from 850 mg/m3 to 5100 mg/m3, with higher concentrations reducing the time needed for visualizing gas–solid contact and quantifying efficiency. The gas–solid contact efficiency (Egs = 87.85 %) calculated by the method showed a small deviation of only 0.55 % from the efficiency (E’gs = 88.4 %) calculated based on sulfur capacity, validating the method’s reliability. The study’s outcomes present a novel method for analyzing the gas–solid contact state, which can serve future efforts in the design optimization of dry fixed-bed desulfurization reactors.