Shenmu Coal Research Articles

The Synergistic Effect Between Coal Macerals During Hydropyrolysis

Using TGA technology, the volatile matter yields during hydropyrolysis of Chinese Shenmu coal and its derived high purity macerals under different heating rates and pressures were investigated. The Δ W, calculated by the difference between the volatile matter yield of parent coal and that of macerals, is used to evaluate the synergistic effect of macerals during hydropyrolysis. The results showed that with increasing pressure and decreasing heating rate, the Δ W increases. At temperature of 500°C and pressure of 3 MPa, the difference of volatile matter yield between parent coal and vitrinite reaches the maximum and the Δ W also occurs the highest value of 14.1%, suggesting the existence of the synergistic effect between macerals during hydropyrolysis. Based on the structural characteristics of macerals and the basic knowledge of hydropyrolysis, the possible explanation for the synergism are proposed.

Thermogravimetric-Mass Spectrometric Study of the Pyrolysis Behavior of Shenmu Macerals Under Hydrogen and Argon

The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H2, heating rate of 10°C/min and final temperature of 900°C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H2O, C1–C4, and C6H6. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H2O and light hydrocarbons was higher in H2 than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H2O and CH4 had different peak distributions and evolution temperatures under H2 and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.

Devolatilization Characteristics of Shenmu Coal Macerals and Kinetic Analysis

The pyrolysis of Shenmu coal macerals was performed in TG151 thermobalance. The volatile matter evolved in primary and secondary devolatilization and devolatilization kinetics were studied. The volatile matter evolved during primary devolatilization is the major part of the total volatile matter, especially for vitrinite. The percentage of volatile matter evolved during primary and secondary devolatilization suggested that inertinite have higher thermal stability. Though the heating rate can affect the percentage of volatile matter evolved during primary and secondary devolatilization, the order of volatile matter in all the temperature range is the same: vitrinite > parent coal > inertinite. The kinetic analysis of devolatilization using distributed activation energy model (DAEM) shows that the activation energy existed relatively large error at the conversion of initial 10% and final 10%. And the conversion of 10% to 90% was used to describe the variation of activation energy during pyrolysis. The activation energy of vitrinite appeared a minimum of about 50% conversion, but that of inertinite always increased as pyrolysis went on, indicating the different structure and chemical composition between them. Inertinite has higher activation energy and lower pyrolysis rate than vitrinite.

Physicochemical properties of Chinese pulverized coal ash in relation to sulfur retention

The sulfur-retention properties, mineralogical compositions, porosities and surface morphologies of two Chinese high-calcium coal ashes are studied by XRD, SEM and porometer analysis. It is found that the active calcium (CaCO 3 and CaO) content in Shenmu coal ash prepared at 800 °C is 22.40% and its sulfation product (CaSO 4) content is 17.79%, which are both higher than those in Huangling coal ash (respectively, 4.48% and 4.92%). With an increase in furnace temperature from 800 to 1200 °C, the porosity parameters of these two coal ashes dramatically decrease due to their intensely melting and no calcium compounds are found.

Release of fuel-nitrogen during the gasification of Shenmu coal in O 2

Formation of NH 3, HCN, NO and NO 2 from the gasification of a Chinese coal (Shenmu) in a fluidised-bed/fixed-bed reactor in 4.1% O 2 in argon was investigated. The presence of O 2 even at 673 or 773 K could lead to the gradual gasification of char to form HCN and NH 3. The yields of NH 3 and HCN showed maxima at about 773 K, amounting to 40% of coal-N. In the presence of O 2, the H radicals required for the formation of NH 3 and HCN may be generated from the reactions in the gas phase and within the solid particles. The yields of NO x increased from 773 to 973 K. A non-negligible proportion (∼5%) of coal-N was converted into NO 2 at 773 K through homogeneous and heterogeneous reactions. The yield of NO 2 diminished with increasing temperature. At 1173 K, the reactions between char-N and H 2O (or O/H-containing radicals) formed from the oxidation of char and volatiles led to the formation of NH 3 but not HCN. This route of NH 3 formation is believed to be an important pathway for the formation of NH 3 in an air-blown gasifier.

Study on hydropyrolysis of macerals from Shenmu coal : Sun, Q. et al. Ranliao Huaxue Xuebao, 2002, 30, (1), 11–15. (In Chinese)

Coal tar pitch-based coke powder with a fine mosaic texture was heat-treated with various concentrations of boron powder at 2900°C. Increasing the boron amount led to smaller d002 and larger d110, and made the original fine texture coarser. Some small particles showed specific structures of polyhedrons, of which surfaces are 002 planes of graphite lattice, after heat treatment with boron. The size of the polyhedron increased with boron content. Boron concentration was lower at the surface than at the inner portions of particles for a powder heat-treated with a higher amount of boron, while it depended less on the depth for that heat-treated with a lower amount of boron. The formation mechanism of the polyhedron particle is discussed.

Combustion reactivity of char from pyrolysis of Shenmu macerals : Sun, Q. et al. Huagong Xuebao, 2002, 53, (1), 92–95. (In Chinese)

The combustion reactivity of chars from pyrolysis of Shenmu coal maceral concentrates under different pyrolysis temperature, heating rate and pressure were systematically investigated by using TGA.The results indicated that the combustion reactivity of chars was related to pyrolysis temperature, pressure,heating rate and distribution of elements in chars.With decreasing temperature and pressure and increasing heating rate,the combustion reactivity of the pyrolysis residues increased.The lower carbon content and higher hydrogen content in chars,the higher combustion reactivity of chars.Under the same pyrolysis condition,the vitrinite chars had higher combustion reactivity than the fusinite chars.

99/00697 Pyrolysis of coal in a fluidized bed pyrolyzer

Pyrolysis of coal is the first step of all coal conversion processes. In a fluidized bed reactor, the secondary reaction of primary pyrolysis products in the freeboard can affect the final product composition. Therefore, by means of controlling the freeboard temperature and the residence time of primary pyrolysis products in the freeboard favorable products can be produced. A Chinese bituminous coal (Shenmu coal, sized 45--80 mesh) is pyrolyzed in a fluidized bed pyrolyzer which is 1.4 meter high, 48mm i.d., heated by electric furnaces. The fluidization gas is N{sub 2}. Coal is continuously fed into the pyrolyzer (the feeding rate is about 1.8g/min). Temperatures of the upper part (freeboard) and the lower part (dense phase) of the reactor within the range of 400--1000 C can be controlled. Along the freeboard there are 4 sampling points of products related to different residence times in the freeboard. In this paper, the effects of operational temperature of dense phase and freeboard, and the residence time of primary product gas in the freeboard on the product composition are investigated. The gaseous products are analyzed by GC. A simple secondary pyrolysis model in the freeboard is given.