Adverse Effects of Inherent CaO in Coconut Shell-Derived Activated Carbon on Its Performance during Flue Gas Desulfurization

Abstract

Activated carbon has been used commercially to remove SO 2 from coal combustion flue gas. However, the role of inherent CaO in activated carbon is uncertain. In this study, the adverse effects of inherent CaO in the activated carbon derived from coconut shell (CSAC) on its desulfurization performance were systematically studied at the temperature range of 60−100 °C in a fixed-bed reactor. The solid sorbent samples were analyzed using scanning electron microscopy, X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and Brunauer−Emmett−Teller analysis. The flue gas compositions were analyzed by using an online flue gas analyzer. The experimental results showed that the inherent CaO had a profoundly adverse influence on the desulfurization capacity and efficiency of CSAC at all of the temperatures studied. This adverse influence was clearly identified by a comparison of the desulfurization performance of the raw CSAC to those of the acid-washed CSAC samples. It was found that the removal of the inherent CaO from CSAC using a pretreatment of HCl aqueous solution led to an increase in the desulfurization capacity of 41.7%. The adverse effects were attributed to the conversion of CaO into dihydrate calcium sulfate whiskers which formed solid crystals that blocked the micropores of the CSAC particles.

Desulfurization Performance and Kinetics of Potassium Hydroxide-Impregnated Char Sorbents for SO2 Removal from Simulated Flue Gas

“…The inhibition of SO 2 adsorption with high steam concentration is possibly caused by water molecules occupying the active sites and blocked the pores of the char sorbent. 1 Therefore, it is believed that high steam concentration in the flue gas made it difficult for the desulfurization process to take place in the char-supported KOH sorbents. 6a, the breakthrough time of K12 during desulfurization significantly increased from 50 to 341 min when the oxygen concentration was increased from 0 to 5%.…”

“…The desulfurization breakthrough time was established when the outlet concentration of SO 2 decrease below 50 ppmv, corresponding to a 95% SO 2 removal efficiency. 1 The breakthrough sulfur capacity of the sorbent ( q t , mg/g) was calculated using eq 8 . 15 with Q , t , m representing the volume flow rate of SO 2 (m 3 /min), the breakthrough time of sorbent (min), and the weight of sorbent (g), respectively.…”

“…The desulfurization breakthrough time was established when the outlet concentration of SO 2 decrease below 50 ppmv, corresponding to a 95% SO 2 removal efficiency. 1 The breakthrough sulfur capacity of the sorbent (q t , mg/g) was calculated using eq 8.…”

“…Activated carbon (AC) materials such as char can be used as an adsorbent, catalyst, or catalyst support because of their relatively large BET surface area, amenability to surface functionalization, and stability in acidic media. 1 , 8 In the cause of using AC as a catalyst support, the reactivity of the activated components is often improved significantly. 9 Liu and co-workers used an AC-supported V 2 O 5 adsorbent for simultaneous SO 2 and NO removal.…”

Evaluation of adsorptive desulfurization performance and economic applicability comparison of activated carbons prepared from various carbon sources

“…As a rousingly competitive desulfurization technology, adsorptive desulfurization (ADS) has attracted signicant attention from academics and enterprises. [13][14][15][16][17][18][19][20] Various desulfurization adsorbents, for instance, metal-organic frameworks (MOFs), 21 zeolites, 22 and activated carbons (ACs), 23 have been constantly developed to fulll the requirements of desulfurization. AC adsorbents (ACA) have the qualities of simple preparation processes, low-cost, relatively high adsorption capability, and earth-abundant sources for manufacture.…”