Pyrolysis Characteristics Of Lignite Research Articles

Effect of pressure and H2 on the pyrolysis characteristics of lignite: Thermal behavior and coal char structural properties

The aim of the present work was to investigate the effect of pressure and H2 on the pyrolysis characteristics of lignite. Thermogravimetric behavior during lignite pyrolysis was studied under different Ar or H2 pressures using a pressurized thermogravimetric analyzer (P-TGA). Structural properties of coal chars obtained from P-TGA were investigated by the application of elemental analyzer, Fourier transform infrared spectroscopy, X-ray diffraction analyzer, and gas sorption surface area and pore size analyzer. CO2 gasification reactivity of coal chars was also evaluated by TGA tests. The results demonstrated that the weight loss for lignite pyrolysis increased in the presence of H2 and it became more remarkable with rising pressure. Meanwhile, conversion of C and H during pressurized hydropyrolysis was promoted to a higher level considerably. Aromaticity as well as graphitization degree for coal chars were both intensified with addition of H2, especially under elevated pressures. As to the mesopore structure, BET specific surface area of coal chars from hydropyrolysis increased obviously in comparison with that of coal chars obtained in Ar atmosphere, especially under pressurized conditions. Moreover, coal chars from hydropyrolysis exhibited higher CO2 gasification reactivity.

Study on catalytic co-pyrolysis of physical mixture/staged pyrolysis characteristics of lignite and straw over an catalytic beds of char and its mechanism

Although the study of co-pyrolysis of coal and biomass have dominated the primary chemicals production in the field of renewable energy utilization, it is still challenging for tar to become lighter. Here we design a set of experimental programs, including the individual pyrolysis, staged catalytic pyrolysis and the co-pyrolysis of physical mixture to investigate the effects of feedstock arrangement on pyrolysis product characteristics. We demonstrated that the experimental results of co-pyrolysis of physical mixture indicate some synergetic effects on pyrolysis products rather than the superposition of individual pyrolysis process of lignite and straw, thus the subsequent tar composition and char structure were characterized. Based on the existing catalytic cracking mechanism, we obtained the staged catalytic pyrolysis have a more pronounced catalytic cracking effect on heavy components compared with the co-pyrolysis of physical mixture, which enables the formation of light oil, naphthalene oil, tar with the lower oxygen content and higher benzene. The Raman spectra of char in catalytic bed exhibits the total peak area of char and the amount of large aromatic ring formed by polymerization increased with the increase of pyrolysis temperature. Simultaneously, the role of catalytic cracking of straw char was stronger than that of lignite char remarkably has been confirmed from the point of view of the chemical structure of char.

The Pyrolysis Characteristics of Low Ash Lignite

The pyrolysis characteristics of lignite with low ash were investigated and the influences of heating rate on the weight loss process were also discussed. The results showed the lignite pyrolysis process can be divided into three stages, in which the second stage, the temperature range is about 300oC ~550oC, is the main process of the weight loss; with the heating rate is enhanced, the temperature of maximum rate of weight loss was increased while the maximum rate of coal weight loss is increased, and the temperature of maximum rate of coal weight loss is basically the same.