Kinetics investigation on the reduction of NO using straw char based on physicochemical characterization.

NO reduction using straw-char has been investigated in a fixed bed, and the effects of char-preparation temperature, reduction temperature, char concentration C(char) and NO concentration C(NO) were considered. Straw char was prepared at three temperatures, 873, 1073 and 1273K. The characterization was conducted by employing SEM-EDS, XRD, BET and TGA. Results show that the char prepared at 1073K holds the most developed pore structure and surface area, the best combustion activity, and the highest NO reduction rate. The reduction rate of NO linearly increases with increasing char concentration, but decreases with increasing NO concentration following a power-function relation. A transition temperature region from dynamic-control to diffusion-control is found to be around 1173K. In the dynamic-control region, the apparent activation energy E of char-NO reaction is in the range of 89.78-95.41kJ mol(-1), affected inconspicuously by the char-preparation temperature. The reaction rate between NO and straw-char is given by r(NO)=k(0)·exp(-11,069/T)·C(NO)(0.89)·C(char).

Study on fusion characteristics of biomass ash.

The ash fusion characteristics (AFC) of Capsicum stalks ashes, cotton stalks ashes and wheat stalks ashes that all prepared by ashing at 400 degrees C, 600 degrees C and 815 degrees C are consistent after 860 degrees C, 990 degrees C and 840 degrees C, respectively in the ash fusion temperature test and TG. Initial deformation temperature (IDT) increases with decreased K(2)O and went up with increased MgO, CaO, Fe(2)O(3) and Al(2)O(3). Softening temperature (ST), hemispherical temperature (HT) and fluid temperature (FT) do not affected by the concentrations of each element and the ashing temperature obviously. Therefore, the IDT may be as an evaluation index of biomass AFC rather than the ST used as an evaluation index of coal AFC. XRD shows that no matter what the ashing temperature is, the biomass ashes contain same high-temperature molten material. Therefore, evaluation of the biomass AFC should not be simply on the proportion of elements except IDT, but the high-temperature molten material in biomass ash.

Effect of particle size in a limestone-hydrochloric acid reaction system.

Experimental characterization of the wet flue gas desulfurization process is carried out using a model limestone-hydrochloric acid reaction system, with in-situ measurement of the dissolution rate and particle size distribution. The limestone source, initial particle size distribution, working temperature and pH value are varied in large ranges. The dissolution rate is found to be higher when the average particle size is smaller, the temperature is higher, or the pH is lower. An empirical equation is established to correlate the dissolution rate with the particle size and working conditions, which agrees well with measurements. The results may be useful for providing insights to improve the efficiency of the wet flue gas desulfurization process, as well as other solid particle-liquid solution reactions.