Zhu Tingyu

Effect of calcium oxide on pyrolysis of coal in a fluidized bed

The pyrolysis of Shenmu bituminous coal in both the presence and absence of calcium oxide was studied under atmospheric pressure over a temperature range of 450–750°C in a fluidized bed reactor. Calcium oxide significantly increases the gas yield while decreasing the tar yield. Tars produced in both the presence and absence of calcium oxide were analyzed and compared. The results indicated that tar yields reach a maximum at 650°C for coal pyrolysis without calcium oxide, in accordance with Tylers results. When calcium oxide is added, the temperature of tar maximum yield is reduced to 550°C. It is also demonstrated that the ratio of H/C; benzene, toluene, xylene (BTX); phenol, cresol, xylenol (PCX) and other light components in tar increase while the ratio of (O+N+S)/C and oxide compounds in tar decrease in the presence of calcium oxide. It is noted that the maximum composition of alkanes in tar is C14–C20 in the presence of calcium oxide, while it is C8–C15 in the absence of calcium oxide. It results from the fracture of alkanes with long chains to alkanes with short chains when calcium oxide is added.

Enhanced Effect of O/N Groups on the Hg-0 Removal Efficiency over the HNO3-Modified Activated Carbon

HNO3-modified activated carbon (AC) was prepared to determine its mercury removal ability on a fixed-bed reactor. In this study, the HNO3-modified AC was found to be effective for mercury removal in simulated flue gas. The original sample, the HNO3-modified sample and the production sample were characterized by elemental analysis, Brunauer-Emmett-Teller (BET) specific surface area measurements, scanning electron microscopy (SEM), Raman spectra, Boehm titrations, temperature programmed desorption (TPD) technique, and X-ray photoelectron spectroscopy (XPS). The results- show that HNO3 treatment increases the content of oxygen and nitrogen on the AC. Compared with the physical characteristics of HNO3-modified AC, the effects of its chemical characteristics on mercury removal are more significant. The Hg-0 is mainly oxidized to HgO by the HNO3-modified AC. The oxygen functional groups, possibly carbonyls, esters or anhydrides were found to be the adsorption sites for mercury removal, and these groups were reduced to hydroxyl groups or ether groups. The N-functional groups, possibly pyrrolic tautomers, were found to be the active catalytic sites. The mechanism for Hg-0 removal by HNO3-modified activated carbon is proposed based on the characterization results.

A Novel Sintering Gas Desulphurization Technology Applied in the Sintering Plants in China

The emission of sulfur dioxide (SO2) produced by the sinter machine takes up more than 50% of the total SO2 emission of the iron and steel industry in China. So it is necessary to take effective measures to strengthen the control of sintering gas desulphurization. A novel sintering gas desulphurization technology, the inner and outer circulating fluidized bed (IOCFB) which is suitable for retrofitting the existing metallurgical industry plants in China will be introduced in this paper. The novel composite internals which can improve the removal efficiency of SO2 is also described. Current research and development needs for IOCFB are to further increase desulphurization efficiency and improve the reliability of plant components. To solve these problems, a pilot plant emulating IOCFB desulfurization processes had been built.

Study on Tar Property from Coal Mild Gasification with Calcium Oxide Catalyst

Tars in both the presence and absence of calcium oxide were analyzed and compared. The results indicated that tar yields reach the maximum at 650 degrees in the absence of calcium oxide. It is in accordance with Tylers results. But when calcium oxide is added, the temperature of tar maximum yield is only 550 degrees C. It is also demonstrated that the ratio of H/C, BTX, PCX and other light content in tar increase while the ratio of (O+N+S)/C and oxide compound in tar decrease in the presence of calcium oxide. It is noted that the maximum composition of alkanes in tar is C14∼C20 in the presence of calcium oxide while is C8∼C15 in the absence of calcium oxide. The yield of phenolic compounds was higher in the presence of calcium oxide than the raw coal alone. The result disagrees with the reported literature. The difference may arise from differences in temperature and gas or solid residence time, or from the difference of activity of calcium oxide used.