Experimental Study On H₂S Removal Based On The Rare Earth Metal Oxide Modified SnO₂ Sorbent

Coal polygeneration system based on gasification is an important way for the clean coal utilization,while H₂S removal from coal syngas is one of the key technologies.Based on the rare earth metal oxide modified SnO₂ sorbent,the dissertation aimed to study the following four aspects,including the reduction behavior of the sorbent under the reducing atmosphere,sulfidation reaction with high concentration steam,regeneration characteristics under steam regenenration and SO₂ regeneration,and COS hydrolysis and co-removal with H₂S.In order to avoid the formation of metallic tin during the reduction of SnO₂ sorbent,rare earth metal oxide modification in the preparation and the influence of H₂O/H₂ ratio in the syngas were studied.For Y modified sorbent,after calcination under at least 700oC,there was pyrochlore Y₂Sn₂O₇ in the Sn2Y-700 sorbent.Y₂Sn₂O₇ increased the reduction temperature of SnO₂ and made it possible to improve the working temperature.At the same reduction temperature,increasing the steam content inhibited the reduction of SnO₂.When there was no metallic tin in the sorbent,the relationship between the minimum H₂O/H₂ ratio and temperature followed the relationship in the equilibrium state of SnO₂ reduction reaction.Under the syngas with high steam content,there was degradation in the sulfidation of SnO₂ sorbent.For La and Y modified sorbent,the sulfidation performance improved by inhibiting SnO₂ grain growth and improving pore structure.At 400oC,30 vol.%H₂and 10 vol.%H₂O,La2Sn sorbent had the breakthrough sulfur capacity of 102.8 mg/g.Based on the study of the influence of steam content and sulfidation temperature,the sulfidation process with steam regeneration was proposed and a fixed-bed reactor sulfidation model was built.The regeneration of SnO₂ sorbent was tested under the steam regeneration and SO₂regeneration at 400-600oC.The H₂S concentration curves and elemental sulfur recovery curves were obtained,respectively.After regeneration,the sintering of SnO₂sorbent resulted in the decrease of cyclic desulfurization performance in the initial cycles.The rare earth metal oxide modified sorbent maintained a stable cyclic desulfurization performance with steam regeneration.Based on the pros and cons of steam regeneration and SO₂ regeneration,a two stage regeneration process was proposed.In the COS and H₂S co-removal process,the COS hydrolysis catalyzed by SnO₂sorbent was studied at 300-400oC and found that the formation of SnS caused the degradation of COS conversion.The La and Y modifide SnO₂ sorbent improved the COS hydrolysis conversion and achieved a COS enhanced hydrolysis by H₂S co-removal.A cyclic desulfurization test of modified SnO₂ was carried out under the simulated coal syngas atmosphere and realized a continuous co-removal of COS and H₂S.