Experimental Studies On Promotion Of Steel Slag On Steam-Biomass Gas Reforming For Hydrogen Production

Biomass resources are abundant and renewable,which is expected to play a vital role in replacing traditional fossil energy.At the same time,steel slag output is large in China,but the utilization rate is low.A large number of accumulated steel slag not only occupies land,but also causes serious environmental pollution.Therefore,this paper mainly aims at the synergistic utilization of steel slag and biomass,and systematically studies the promotion mechanism of steel slag on steam reforming biomass gas for hydrogen production.Steel slag-derived high-performance CO₂ sorbent is coupled with steam reforming of biomass gas to improve hydrogen production efficiency,which has vital significance for realizing the high-value utilization of biomass and steel slag.The main research contents and results of this paper are as follows:First of all,steel slag-derived Ca O-based sorbents were prepared by different concentrations of acid solution leaching and CO₂ capture carpacities of these sorbents were experimentally studied.The results showed that steel slag-derived Ca O sorbent,leached by 1 mol/L acetic acid solution,exhibited the optimal CO₂ capture carpicity of0.25 g _CO2/g_sorbent after 35 carbonation/desorption cycles.The reason was that uniformly distributed Mg O and Si O₂ in Ca O could play the role of anti-sintering inert skeleton.Secondly,the enhancing effects of Ca O（SS）-1.0 on hydrogen production during sorption enhanced steam reforming of biomass gas（SE-SRBG）was thoroughly investigated.Impacts of reaction temperature,weight hourly space velocity and catalyst-to-sorbent ratio on performance of SE-SRBG with Ca O（SS）as CO₂ acceptor were investigated in detail and the enhancing effect of Ca O（CA）on hydrogen production during SE-SRBG was compared.The results showed that product gas containg high purity H₂ and trace CO could be achieved by SE-SRBG at lower temperature.CH₄ conversion,CO selectivity and H₂ recovery factor increased with the increase of temperature.The sorption enhancement of Ca O（SS）was more obvious when the reforming temperature was lower than 600 ^oC.With the assistance of Ca O（SS）-1.0,SE-SRBG at 600 ^oC achieved product gas containing 96 vol.%H₂ and only 1 vol.%CO,with CH₄ conversion of 92%and H₂ recovery factor of 2.71.When C/A was 0.6,CH₄ conversion and H₂ recovery factor at the pre-breakthrough stage were the highest,due to the largest sorption capacity.Compared with Ca O（CA）,the enhancement of Ca O（SS）was more obvious,because the CO₂ sorption capacity of Ca O（SS）was larger and Fe and Mg in Ca O（SS）could promote steam reforming of methane and water-gas shift reaction.Finally,based on particle contents and loading patterns,cyclic SE-SRBG was carried out and investigated in four different operating modes,including（I）mono-functional particles mechanically mixed,（II）bi-functional particles combined by directly tableting,（III）bi-functional particles combined by adhesively tableting and（IV）mono-functional particles layered packed.The effects of operating procedure and integrating calcined leaching residue with sorbent on the cyclic reforming/regeneration stability were also investigated.The results showed that an intermediate reduction step between reforming and regeneration steps was found to be crucial to maintain the catalytic activity of the Ni-based catalyst for consecutive reforming-regeneration cycles.Combined catalyst-sorbent by adhesively tableting exhibited the worst cyclic reforming stability.This was mainly ascribed to the loss of Ni active sites,caused by severe sintering and coverage by Ca CO₃.Operating modes employing layered packed catalyst and sorbent offered a H₂ purity of 90%and CH₄ conversion of 78%even after 10 cycles.In operating mode using layered packed catalyst and sorbent,integration of LR into sorbent was demonstrated to be able to significantly improve cyclic reforming stability.This was attributed to the synergistic catalysis activity of Fe in the LR and the sintering resistance of LR.Resultantly,H₂ concentration of 92%and CH₄ conversion of 90%was still achieved in the 10th cycle of SE-SRBG operated using layered packed catalyst and Ca O（SS）-20wt.%LR.