Study On Modified Rare Earth Tailing Catalysts For Combustion Of Low Concentration Methane

In the process of mining,a large amount of coalbed methane?CBM?is diluted and discharged into the atmosphere,the main component is CH₄.As a long-termgreenhouse gas,the greenhouse effect of CH₄ has 21²3 times to CO₂.The concentration of methane in the CBM is extremely low.Low concentration of methane has low energy utilization rate,which is difficult to utilize in the traditional way.At present,low concentration methane is generally treated by catalytic combustion,therefore,The key to solve the problem is find an efficient and economical catalysts.As is known to all,Bayan obo rare earth tailings were generated in the process of iron and rare earth separation in Baotou steel concentrator,which is a typical symbiosis associated refractory tailings.The rare earth tailings contain a large number of valuable mineral components such as rare earth ferromanganese,and are a potential secondary resource.If the tailings are accumulated excessively,it will not only waste the mineral resources,but also harmful to the environment,which will seriously hinders the development of circular economy and the establishment of a resource-saving and energy-conserving society.The Bayan obotailings catalysts?Calcined tailings-based catalyst?Multi-hole ceramic monolithic catalyst in tailings base?were successfully prepared.The structure and morphology of catalysts weresystematically investigated by XRF,XRD,SEM and other characterization methods.The methane catalytic performances of catalysts were studied by H₂-TPR and activity evaluation devices.The valence compositions of active substances in catalysts were determined by XPS.The main conclusions were as follows:?1?Rare earth tailings have good catalytic performance after roasting at 600?,its T₁₀ and T₉₀ are 495?and 676?,respectively.It is showed that the surface roughness of the tailings increased after roasting,which made the contact between the reaction gas and the active substances more sufficient,and some minerals decomposed to form the active substances which were beneficial to catalysis.?2?The rare earth tailings foam ceramics were prepared by organic foam impregnation method.The pretreated polyurethane sponge was immersed in the ceramic slurry and after the sponge was saturated,the excess slurry was removed by glass extrusion methodfor several times.The ceramic prefabricated blocks were dried in the drying box.At last,rare earth tailings foam ceramics were made by sintering at 950?in muffle furnace.It can be obtained by calculation thatthe porosity and compressive strength of the porous ceramic were 85.7%and 2.9Mpa,respectively.The results of the activity evaluation showed that the activity foam ceramics was poor,when the reaction temperature is 800?,the conversion of methane was only 63.8%.?3?By adding sintering aids B₂O₃ in rare earth tailings based foam ceramics,the sintering temperature of ceramics can be reduced and the catalytic performance of ceramic catalysts was enhanced.The effect of B₂O₃ on the performance of tailings ceramic catalyst was studied.Finally,the best formula of tailings ceramic paste was as follows:63wt%rare earth tailings?10wt%B₂O₃?7wt%sodium silicate?1wt%sodium lauryl benzene sulfonate solution?mass fraction 1%??1wt%CMC solution?mass fraction 1%??16wt%deionized water.The tailings ceramic catalyst prepared by this formula has excellent catalytic performance and high chemical stability to low concentration methane,which the T₁₀ and T₉₀were 407?and 637?,respectively,and the compressive strength was 2.6MPa.