Experimental study on integrated desulfurization and denitrification of low-temperature flue gas by oxidation method.

In this paper, TiO2 catalysts doped with different Fe contents (Fe-TiO2 catalysts) were prepared by coprecipitation method and the Fe loading capacity was optimized, and then the integrated pollutant removal experiment was conducted, in which TiO2 doped with Fe as catalyst and H2O2 as oxidant. The results show that under the condition of constant H2O2/(SO2 + NO) molar ratio, low concentration of SO2 can promote the oxidation and removal efficiency of NO, while high concentration of SO2 can inhibit the removal of NOx. The pollutant removal efficiency is proportional to the amount of catalyst, liquid-gas ratio and pH value of the absorbing solution. The optimal experimental conditions are H2O2/(SO2 + NO) molar ratio 1.5, space velocity ratio 10,000 h-1, H2O2 mass fraction 10 wt%, liquid gas ratio 10, pH 10. Correspondingly, NO oxidation efficiency reaches 88%, NOx removal efficiency 85.6%, and SO2 is almost completely removed. The microstructure of the catalyst before and after the reaction was characterized, and the crystal structure did not change obviously. However, with the deepening of the reaction, the specific surface area of the catalyst decreases, and the catalytic effect decreases slightly.

Research on the optimum carbonization process of walnut shell based on dynamic analysis.

Walnut shell is characterized by high yield, high fixed carbon content, and low ash content. In this paper, the thermodynamic parameters for walnut shell during the carbonization process is investigated, and its carbonization and mechanism are discussed. Then, the optimal carbonization process of walnut shell is proposed. Results demonstrated that the comprehensive characteristic index of pyrolysis first increases and then decreases with the increase of heating rate and reaches the peak at about 10 °C min-1. Note that the carbonization reaction intensifies at this heating rate. The carbonization process of walnut shell is a complex reaction involving multiple steps. It decomposes hemicellulose, cellulose, and lignin in stages, and the activation energy of this process gradually increases. The simulation and experimental analyses showed that the optimal process presents a heating time of 14.8 min, final temperature of 324.7 °C, holding time of 55.5 min, particle size of material of about 2 mm, and optimum carbonization rate of 69.4%.

Co-combustion of high alkali coal with municipal sludge: Thermal behaviour, kinetic analysis, and micro characteristic.

Blending sludge rich in protein and aliphatic hydrocarbons into the high alkali coal (HAC) has been demonstrated to reduce the ash melting temperature of the HAC/sludge mixture, thereby increasing the effectiveness and efficiency of liquid slagging. However, whether the incorporation of sludge can affect the combustion stability of the original coal-fired boiler is still debatable. As the combustion stability of the fuel can directly affect the operational safety of the boiler, it is of great practical value for exploring the effect of sludge incorporation on the combustion performance of HAC. In this work, the thermal behaviour and microscopic properties of individual HAC, municipal sludge (MS) and HAC/MS mixtures were tested using a Thermogravimetric analyser (TGA) and a Fourier transform infrared (FTIR) spectrometer, respectively. The exothermic, thermodynamic and functional group evolution patterns during the combustion of these samples were also evaluated. Ignition temperatures (Ti) of the HAC/MS mixtures were relatively lower than that of individual HAC, and decreased with the increase in sludge mass ratio (SMR). The synergistic effect of the co-combustion of HAC and MS resulted in a slightly higher total heat release during the combustion of MS10HAC90 (i.e., the mass percentage of MS and HAC is 1:9) than HAC alone, however, the total heat release of the blend decreased progressively with increasing SMR. The experimental values of the average Eα for all four mixtures were lower than the theoretical values, indicating that the addition of MS lowered the reaction energy barriers of the mixtures. Consumption rates of the principal groups in samples during the oxidation and combustion all tended to increase progressively with increasing SMR. There are three major synergistic effects existing during co-combustion of HAC and MS: (1) the reaction of free radicals with benzene molecules; (2) the interaction of free radicals; and (3) the catalytic effect of alkali and alkaline earth metals. These findings can provide theoretical guidance for the determination of key parameters (mixing ratio) for the blending of HAC and MS, and can fill the research gap in terms of microscopic reactivity and synergistic effects during the co-combustion of HAC and MS.

Research on Combustion Properties and Pollutant Emission Characteristics of Blends of Maltol Byproduct/Pine Sawdust.

In this paper, the combustion and pollutant emission characteristics of maltol byproduct, pine sawdust, and their blends were experimentally studied by thermogravimetry, tube furnace experiment, and scanning electron microscopy. The results show that the combustion process of maltol byproduct, pine sawdust, and their blends can be divided into three stages, in which the volatile release of the maltol byproduct includes two stages. The ignition temperature of the blended fuel is lower than that of sawdust. The NO x produced by combustion of the blended fuel is lower than that produced by sawdust combustion alone, and the SO2 emission is always at a low level. There is a certain synergy between maltol byproduct and pine sawdust mixed combustion. Comprehensively comparing the combustion characteristics and emission characteristics, the blended fuel made by adding less than 10% maltol byproduct into pine sawdust can improve the combustion characteristics and reduce emissions, and 10% is the best proportion of the blended fuel.

Comparative Analyses between Raw and Preoxidized Pulverized Coals: Combustion Behaviors and Thermokinetic and Microcharacteristics.

Investigating the difference in the combustion performance and microcharacteristics of oxidized and raw pulverized coal (PC) can contribute to effectively prevent and control the spontaneous combustion of deposited coal dust in high-temperature environment and further help guarantee the safe operation of coal-fired boiler. In this study, the combustion performance and thermokinetic and microcharacteristics of three raw coal samples and their preoxidized forms were explored by a thermogravimetric analyzer (TGA) and Fourier transform infrared spectroscopy (FTIR). According to the characteristic temperatures and variations of the mass loss rate during heating, the entire combustion process of PC was divided into four periods. For each type of coal, the preoxidized PC had relatively lower characteristic temperatures than the corresponding raw PC. The preoxidized samples had larger values of ignition index (C ig) and comprehensive combustibility index (S), but lower values of burnout index (C b) than raw samples. The values of apparent activation energy (E) for the preoxidized PC were below that of the corresponding raw PC at the same conversion rate (α), which suggested the preoxidized PC required relatively less energy to react and was more prone to spontaneous combustion. In addition, although parts of -OH, C=O, and aliphatic hydrocarbon groups were consumed after the preoxidation treatment, the increase in C-O and -COO- bonds compensated for the adverse effect of the reduction of the aforementioned groups on coal combustion.

Plant height-crown radius and canopy coverage-density relationships determine above-ground biomass-density relationship in stressful environments.

Debate continues in theoretical ecology over whether and why the scaling exponent of biomass-density (M-N) relationship varies along environmental gradients. By developing a novel geometric model with assumptions of allometric growth at the individual level and open canopy at the stand level, we propose that plant height-crown radius and canopy coverage-density relationships determine the above-ground M-N relationship in stressful environments. Results from field investigation along an aridity gradient (from eastern to western China) confirmed our model prediction and showed that the above-ground M-N scaling exponent increased with drought stress. Therefore, the 'universal' scaling exponents (-3/2 or -4/3) of the M-N relationship predicted by previous models may not hold for above-ground parts in stressful environments.

[Pharmacognostic identification of Cryptolepis buchanaii].

OBJECTIVE: To supply basis for the establishment of quality standard of Cryptolepis buchanaii. METHOD: Characters of crude drugs, microscopic characteristic as well as UV spectrum of the herb were studied. RESULT: Laticifers were found in the cortex and pith of the stem; much papillary non-glandular hair was found covering the stomata in the sub-cuticle of the leaf. CONCLUSION: The results can be employed as the basis for identifying the herb.