Effects of ultrasound on the desulfurization performance of hot coal gas over Zn-Mn-Cu supported on semi-coke sorbent prepared by high-pressure impregnation method

Abstract

Zn-Mn-Cu/SC(U) sorbent was hydrothermally synthesized by ultrasound-assisted high-pressure impregnation method with semi-coke (SC) as support and the mixed solution of zinc nitrate, manganese nitrate and copper nitrate as active component precursors. The desulfurization performances of hot coal gas on the prepared sorbent at a mid-temperature of 500 °C were tested in fixed-bed reactor. Morphology and pore structure of the prepared sorbent were also characterized by TEM, N2 adsorption/desorption isotherms and XRD. For comparison, the sorbent of Zn-Mn-Cu/SC prepared by conventional high-pressure impregnation was also evaluated and characterized in order to study the effects of ultrasound treatment. Zn-Mn-Cu/SC(U) sorbent prepared by high-pressure impregnation under ultrasound-assisted condition showed a better desulfurization performance than Zn-Mn-Cu/SC. It could remove H2S from 1000×10−6 m3/m3 to 0.1×10−6 m3/m3 at 500 °C and maintained for 12.5 h with the sulfur capacity of 7.74%, in which both the breakthrough time and sulfur capacity were about 32% and 51% higher than those of Zn-Mn-Cu/SC sorbent. The introduction of ultrasound during high-pressure impregnation process greatly improved the morphology and pore structure of the sorbent. The ultrasonic treatment made particle size of active components smaller and made them more evenly disperse on semi-coke support, which provided more opportunities to contact with H2S in coal-based gases. However, there were no any difference in compositions and existing forms of active components on the Zn-Mn-Cu/SC and Zn-Mn-Cu/SC(U) sorbents.