不同热解升温速率下烟煤热解焦结构特性及其气化反应性的研究

Study on Structure and Gasification Reactivity of Char from Different Pyrolysis Heating Rates

煤焦结构是影响煤焦气化反应性的关键因素,而制焦温度和煤热解升温速率会影响煤焦物化结构,进而影响气化反应性。本文是以烟煤为实验用煤,在两种不同升温速率的固定床石英热解反应器中分别制700~1100℃五种煤焦样品,通过X射线衍射仪(XRD)、拉曼光谱仪、低温N_(2)吸附仪表征不同升温速率下制得煤焦样品的物化结构,并通过固定床反应器评价煤焦气化反应性。结果表明,固定床程序升温热解和快速升温热解制得煤焦样品随着热解温度变化,微晶结构和孔隙结构呈现不同的变化规律。随着热解温度的增加,煤焦微晶结构尺寸(L_(c)芳香片层高度,L_a芳香片直径)不断增大,S带交联反应强度(I_(S)/I_(G))减弱,大环与小环的比例(I_(D)/I_((Gr+Vr+Vl)))不断减小,芳香度(ƒ_(a))不断增大,表明煤焦样品缩聚程度不断加深,石墨化程度增加,煤焦结构更加稳定有序,气化反应性逐渐降低。气化反应性主要与微晶结构尺寸、大环与小环的比例、无定形碳结构数量有关,孔隙结构与其关联性不大。

Char structure is a key factor affecting the gasification reactivity,while char prepared temperature and coal pyrolysis heating rate affect the physical and chemical structure of char,which in turn affects the gasification reactivity.In this paper,five char samples were prepared in two fixed-bed quartz pyrolysis reactors with different temperature ramping rates from 700 to 1100℃using bituminous coal inthis study,and the physical and chemical structures of the char samples were characterized by X-ray diffractometer(XRD),Raman spectrometer,and low-temperature N^(2) adsorption instrument at different temperature ramping rates,and the reactivity of char gasification was evaluated by the fixed-bed reactor.The results showed that the microcrystalline structure and pore structure of the char samples obtained from the fixed-bed programmed warming pyrolysis and the fast warming pyrolysis showed different patterns of changes with the change of the pyrolysis temperature.With the increase of pyrolysis temperature,the size of char microcrystalline structure(L_(c) aromatic sheet layer height,L_(a) aromatic sheet diameter)increased continuously,the intensity of S-band cross-linking reaction(I_(S)/I_(G))weakened,the ratio of large ring to small ring(ID/I_((Gr+Vr+Vl)))decreased continuously,and the aromaticity(ƒ_(a))increased continuously,indicating that the degree of condensation of char samples deepened,the degree of graphitization increased,the char structure is more stable and orderly,and the reactivity of gasification is gradually reduced.The gasification reactivity is mainly related to the size of microcrystalline structure,the ratio of large ring to small ring,and the number of amorphous carbon structures,and the pore structure has little effect on it.