Desulfurization performance of iron-manganese-based sorbent for hot coal gas

Abstract

A series of iron-manganese-based sorbents were prepared by co-precipitation and physical mixing method, and used for H 2 S removal from hot coal gas. The sulfidation tests were carried out in a fixed-bed reactor with space velocity of 2000 h -1 (STP). The results show that the suitable addition of manganese oxide in iron-based sorbent can decrease H 2 S and COS concentration in exit before breakthrough due to its simultaneous reaction capability with H 2 S and COS. Fe 3 O 4 and MnO are the initial active components in iron-manganese-based sorbent, and FeO and Fe are active components formed by reduction during sulfidation. The crystal phases of iron affect obviously their desulfurization capacity. The reducibility of sorbent changes with the content of MnO in sorbent. S7F3M and S3F7M have bigger sulfur capacities (32.68 and 32.30 gS/ 100 g total active component), while S5F5M has smaller sulfur capacity (21.92 gS/100 g total active component). S7F3M sorbent has stable sulfidation performance in three sulfidation-regeneration cycles and no apparent structure degradation. The sulfidation performance of ironmanganese-based sorbent is also related with its specific surface area and pore volume.

Desulfurization Behavior of Fe–Mn-Based Regenerable Sorbents for High-Temperature H2S Removal

“…The breakthrough curve was expressed as a plot of the outlet concentration of H 2 S versus time. In addition, the amount of sulfur captured by the sorbent at the breakthrough onset (lower than 50 ppmv sulfur in the outlet) was denoted as the breakthrough sulfur capacity or effective sulfur capacity, calculated using eq lefttrue S C ⁢ ( g S / 100 g sorbent ) = WHSV × M S V m × false[ prefix∫ 0 t normalb false( C in − C out false) d t false] × 10 − 4 where SC is the effective sulfur capacity of the sorbent, WHSV is the weight hourly space velocity (L h –1 g –1 ), M s is the mole weight of sulfur (32.06 g mol –1 ), V m is the mole volume of H 2 S at 1 atm and 298 K (24.5 L mol –1 ), t b is the breakthrough time of the sorbent (h), and C in and C out are the inlet and outlet concentrations of H 2 S (ppmv), respectively.…”

“…In Zhang's work, however, when the molar ratio of Mn:Fe is less than 2.0, the breakthrough sulfur capacity increases with increasing molar ratio of Mn:Fe; when the molar ratio of Mn:Fe is more than 2.0, the breakthrough sulfur capacity decreases with increasing molar ratio of Mn:Fe; the maximum breakthrough sulfur capacity was obtained at a molar ratio of 2.0 of Mn:Fe at 923 K. This may be related to the reducibility of mixed oxides. At lower temperature, the reduction products and degree of iron oxide and manganese oxide depend on the molar ratio of Mn:Fe and temperature; 27 it results in different desulfurization activity of sorbents with different molar ratios of Mn:Fe. In our work, all oxides of Fe and Mn are rapidly reduced to Fe and MnO at the high temperature of 1123 K; Fe and MnO are the active component of the sorbents.…”

“…Furthermore, many reports have indicated the excellent sulfidation–regeneration performance, high sulfur capacity, high desulfurization efficiency, and high stability of alumina-supported MnO at temperatures up to 1123 K. − Therefore, Fe–Mn-based sorbents were investigated widely to reserve the advantages possessed by iron and manganese and avoid their disadvantages. In the studies of Ren, it was shown that the addition of manganese oxide can improve the desulfurization capacity of iron-based sorbent at 773 K, Fe 3 O 4 and MnO are the active components of the Fe–Mn-based sorbents, and sorbents with Fe/Mn mole ratios of 7:3 and 3:7 have bigger sulfur capacities. The desulfurization performance of Fe–Mn-based sorbents was also investigated by Zhang; the studies showed that the sorbent’s reactivity and regenerability were improved at 923 K when Mn and Fe were supported upon a suitable support; the maximum breakthrough sulfur capacity of 4.2 g S/100g sorbent was obtained at the mole ratio of 0.5 Fe/Mn; the breakthrough sulfur capacity of regenerated sorbent was slightly decreased compared with the fresh sorbents when the number of sulfidation–regeneration cycles exceeded seven.…”