Yunmei Li

Promotion of Ferrous Sulfate Catalyst by Sulfur for Hydrogenation of Coal

Sulfur released from five Chinese coals and an USA coal in hydrogen was correlated with the catalytic activity of an impregnated ferrous sulfate for hydrogenation of the coals. The hydrogenation was carried out at a high or ambient pressure. Sulfur released from the coals into the gas phase at the ambient pressure was monitored online with a flame photometric detector. The data indicate that the catalytic activity of the impregnated ferrous sulfate was promoted by the sulfur released from the coals. The promotion ability is proportional to the amount of sulfur released for the lower sulfur coals generally and levels out for the higher sulfur coals. The promotive effect of sodium sulfide on the activity of ferrous sulfate shows the similar behavior. Additional sulfur, no matter added or released, does not improve the catalytic activity further significantly for the higher sulfur coals. The results partially explain the difference in the catalytic activity of ferrous sulfate and effectiveness on added sulfur for different coals.

Dynamic Behaviors of Sulfur Evolved in the Gas Phase from Pyrolysis of Six Chinese Coals

Dynamic behaviors of gaseous sulfur-containing compounds evolved from pyrolysis of six Chinese coals were studied in the temperature range of up to 800°C under N2 and H2. The released amount of total sulfur-containing gases was traced by an online flame photometric detector (FPD). Simultaneously, the changes of different sulfur forms, including H2S, SO2, COS and CS2, also were investigated using an online mass spectrometer (MS). FPD results show that the effect of H2 on gaseous sulfur evolved is complex, which promoted certain peak and suppresses other peaks. Based on the data from MS, it is suggested that a series of competitive reactions between active sulfur and other active matters during pyrolysis may impact on the sulfur form in gas phase. Interactions between active sulfur-containing intermediates and the coal matrix are attributed to be the main factor determining the dynamic behavior.

Effects of Organic Gaseous Additives on Desulfurization of Coal during Pyrolysis

Sulfur removal from coal prior to combustion is an ideal form of sulfur emission control. Pyrolysis is likely to be an effective way to transform sulfur in coal to gas and liquid phases and to generate chars of low sulfur for clean combustion. This article presents recent research on the effects of organic additives on sulfur removal from a Spanish coal and 3 Chinese coals (Yanzhou, Datong, and Xianfeng) by pyrolysis. The coal samples were pyrolyzed in a fixed-bed reactor in a temperature range up to 700°C. Ethanol or acetone was introduced to a pyrolysis atmosphere. It was observed that the introduction of the organic reagents in pyrolysis altered the behavior of sulfur removal as well as the evolution of volatile matter from coals, which resulted in lower sulfur content chars and higher char yields than that in hydrogen and nitrogen. The desulfurization efficiency increases with increasing ethanol or acetone addition. For Datong coal, the promotion of ethanol and acetone on sulfur removal was the most remarkable. Based on XPS information, the promotive effect is contributed to selective oxidation of organic sulfur.

Preparation of mesophase pitch from coliquefaction residue under pressure

ABSTRACT Large wide-area mesophase pitch (MP) could be prepared by thermal polymerization method from asphaltene (AP) extracted from coliquefaction residue. The influences of temperature, soaking time, and initial gauge pressure on MP formation were investigated. The results indicate that initial gauge pressure has a strong impact on MP formation except for temperature and time. Increasing initial gauge pressure appropriately promotes the coalescence and rearrangement of mesophase microspheres, but too high pressure hinders microspheres to coalesce. The optimum formation condition of large wide-area MP with lower softening point (~270°C) is determined by the temperature at about 400°C, initial gauge pressure at about 1 MPa, and a soaking time of about 10 h. Based on SEM result, mesophase microspheres present a globe structure, they grow and coalesce obeying the mechanism of homogeneous nucleation.