Study On Catalytic Co-pyrolysis Characteristics And Kinetics Of Coal And Walnut Shell

To utilize biomass resources more effectively,improve highly-efficient and clean utilization level,broaden application of natural mineral materials,the individual pyrolysis,co-pyrolysis,together with catalytic co-pyrolysis by kaolin or siderite,of Baode coal(BDC)and walnut shell(WS)were performed,by means of TG/DSC thermogravimetric analysis.The pyrolysis characteristics,kinetics,as well as mechanism functions during the main stages were obtained.Results can offer certain theoretical reference for industrial design of thermal conversion associated with biomass and coal.The individual pyrolysis were carried out at heating rates of 5?/min,10?/min and 15?/min,it was found that heating rate has little effect on the pyrolysis of BDC and WS,and partially overlapped pyrolysis temperature ranges can lay a good foundation for synergies during pyrolysis.As a reslut,series of co-pyrolysis of BDC and WS were measured at designated heating rate of 10?/min.It was shown that the first stage ranging from 250? to 400? is attributed to decompositon of cellulose and hemicellulose in the WS,the second stage between 40?and 500? stems from devolatilization of the BDC and decomposition of lignin in the WS.By comparison of theoretical and experimental mass loss values of blends BDC/WS(1:1),BDC/WS(1:2),BDC/WS(1:3),BDC/WS(1:4),synergies are observed in the co-pyrolysis,especially in BDC/WS(1:2).Addition of kaolin or siderite into the blends of BDC and WS,at levels of 1 wt%,5 wt%,10 wt%and 15 wt%,led to decrease in residue,illustrating catalytic effects from the kaolin or siderite on formation of micro-molecular compounds during the co-pyrolysis.Better catalytic effect from siderite was detected compared to kaolin.The kinetics were analyzed using differential and integral methods based on individual pyrolysis,co-pyrolysis and catalytic co-pyrolysis measurements.It was revealed that activation energy of WS individual pyrolysis is lower than that of BDC;activation energy of co-pyrolysis of the BDC and the WS is lower than those of individual pyrolysis in the same stages,confirming the synergies occurred in the co-pyrolysis.A relatively lower activation energy was acquired for blend BDC/WS(1:2).Blends from the BDC and the WS loaded with 10 wt%kaolin or 5 wt%siderite were measured with reduced activation energies compared to corresponding conventional co-pyroysis.It was suggested that individual pyrolysis of the WS belongs to Parobolic law of one-dimensional diffusion;pyrolysis of the BDC conforms to Jander equation of three-dimensional diffusion;conventional co-pyrolysis of the BDC and the WS accords with Parobolic law;mechanism function of catalytic co-pyrolysis is shifted back to Jander equation of three-dimensional diffusion,accounting for promotion in BDC pyrolysis from kaolin or siderite,which dominates in this stage.