Fuchen Wang

Multifractal detrended fluctuation analysis of combustion flames in four-burner impinging entrained-flow gasifier

Abstract On a laboratory-scale testing platform of an impinging entrained-flow gasifier with four opposed burners, the flame images for diesel combustion and gasification process were recorded with a single charge coupled device (CCD) camera. The two-dimensional multifractal detrended fluctuation analysis was employed to investigate the multifractal nature of the flame images. Sound power-law scaling relations in the annealed average of detrended fluctuations were unveiled when the order q > 0 , and the multifractal feature of flame images was confirmed. Further analyses identified two multifractal parameters, the minimum and maximum singularities α min ⁡ and α max ⁡ , serving as characteristic parameters of the multifractal flames. These two characteristic multifractal parameters vary with respect to different experimental conditions.

Mechanism of Hydrogen Production by the Catalytic Steam Reforming of Bio-oil

Many oxygen compounds were contained in bio-oil, such as acids, alcohols, ketones, aldehydes, phenols, and sugar. Acetic acid, ethylene glycol, butanone, furfural, and m-cresol were selected as bio-oil model compounds in this article. Hydrogen production was carried out via catalytic steam reforming under the conditions of the mole ratio of steam and carbon = 6, liquid hourly space velocity = 5 h−1, and 600°C with catalyst Ni/MgO. Infrared gas analyzer was used to analyze gas concentration via catalytic steam reforming of model compounds on line, while the liquid products from a collection device were analyzed by gas chromatography/mass spectrum. Intermediates were formed under catalytic steam reforming through elimination and recombination reaction, etc. The intermediates reacted with steam to produce H2 and CO2, and then the reactions reached equilibrium in the end. The hydrogen yield of acetic acid, ethylene glycol, and butanone as materials were higher than that of furfural and m-cresol as materials at the same conditions. The lowest hydrogen yield is only 34.0% (m-cresol as feedstock) and the highest hydrogen yield is up to 78.6% (butanone as feedstock).

Preparation of Coal Slurry with Alcohol Fermentation Wastewater

Abstract The feasibility of substituting alcohol fermentation wastewater of maize and cassava for water to prepare coal slurries was explored. The rheological and stability properties of coal alcohol fermentation wastewater slurries were studied and compared with that of coal water slurry. The results showed that both coal maize and cassava alcohol fermentation wastewater slurries exhibited shear-thinning behavior. Because of the oxygen-containing functional groups (carboxylic) with exchangeable cations in alcohol fermentation wastewater and its low pH value, coal maize and cassava alcohol fermentation wastewater slurries exhibited the higher apparent viscosities, the stronger shear-thinning behavior, and worse stabilities compared with the coal water slurry. In addition, alcohol fermentation wastewater should be diluted for preparing coal slurries to meet industrial need in apparent viscosity and solid concentration at the same time.

The Steam Gasification of Coal Catalyzed by KOH for the Production of Hydrogen

Potassium-catalyzed steam gasification of Hohhot coal for H2 production was performed using a laboratory fixed-bed reaction system with an on-line cubic micro flow infrared gas analyzer. The gasification reactivity, gasification selectivity, and gas release for the catalytic gasification were investigated and compared with the non-catalytic gasification. The amounts of gases released in the heat-up stage were insignificant for catalyzed gasification, compared to those released in the gasification stage. The potassium hydroxide catalyst could not only effectively promote gasification reactivity, but also enhance greatly H2 production. In the case of catalytic gasification, the steam partial pressure had an effect on the gasification reactivity, suggesting that there existed in an optimum steam partial pressure (about 50%) for H2 production from the potassium-catalyzed steam gasification of the Hohhot coal. In addition, Hohhot coal could be feasibly utilized as the feedstock for the catalytic steam gasification to produce gases with high H2 (60.9–65.2%).

An Experimental Investigation on Characteristics of Individual Flame and Multi-jet Flame

In this article, the differences between individual flame and multi-jet flames are studied. The results show that the air-blast atomization flame length is co-controlled by liquid atomization and combustion intensity. Multi-jet burner is an effective method to improve combustion intensity and shorten flame absolute length. As the oxygen velocity increased, the individual flame increased in length due to better atomization, and yet the multi-jet flame length decreased owing to better combustion intensity. A further increase in oxygen velocity had little effect on flame length but flame noises and luminosity continued to increase. The temperature gradient of the multi-jet flame was higher. An empirical formula to express the variation of the multi-jet flame length and the individual flame length was given.

R/S method for unevenly sampled time series: Application to detecting long-term temporal dependence of droplets transiting through a fixed spatial point in gas–liquid two-phase turbulent jets

We perform rescaled range analysis upon the signals measure d by Dual Particle Dynamical Analyzer in gas-liquid two-phase turbulent jets. A novel re scaled range analysis is proposed to investigate these unevenly sampled signals. The Hurst ex ponents of velocity and other passive scalars in the bulk of spray are obtained to be 0.59 ±0.02 and the fractal dimension is hence 1.41 ± 0.02, which are in remarkable agreement with and much more pr ecise than previous results. These scaling exponents are found to be in dependent of the configuration and dimensions of the nozzle and the fluid flows. Therefore, su ch type of systems form a universality class with invariant scaling properties.

Reaction Kinetic Analysis of Bituminous Coal Char Gasified by CO2

CO2-gasification behaviors of Shenfu bituminous coal from China were investigated by thermogravimetric analyzer within the temperature range of 1173–1323 K, and the pressure from 0.1 to 3.0 MPa. The effects of the temperature and pressure on the CO2 gasification of Shenfu char and the relationship between the gasification rate and gasification time in reactor were analyzed. It is found that the reaction rate presents normal distribution with gasification time and a normal distribution model is proposed to fit the kinetics data. Compared with the random pore model, the normal distribution model can be used to describe the gasification rate varying with gasification time at different temperature and pressure. The gasification time tm for maximum gasification rate obeys the following equation as the function of reaction temperature: . rm, r0 were calculated by a normal distribution model following Arrenius law.

The Effect of Industry Slag on Coal Water Slurry and Gasification

With the development of the coal gasification industry, the output of industry slag is increasing. The industry slag, mostly as a waste, is not only composed of ash but also some coal that was not gasified. Thus, it is a critical problem to adequately utilize the slag. It can be solved if the slag is recycled to use as an additive for the coal gasification because the slag has a catalytic effect on coal gasification and the coal left in the slag could be utilized. However, the feasibility of coal water slurry with slag is unknown. This article aims to investigate the feasibility and focus on the effect of the slag as an additive on the property of the coal water slurry and the reactivity of gasification. Different loading contents of slag were analyzed to investigate the optimum and the maximum loading contents of the slag. The apparent viscosity, stability, and fluidity of coal water slurry were compared to study the mechanism of the slag on the property of coal water slurry and the activity of gasification.

Steam Catalytic Gasification Kinetics of the Hohhot Coals

The effects of temperature on the steam gasification of the Hohhot coal and saturated addition of KOH catalyst were investigated by thermo gravimetric-differential scanning calorimetry equipment. It was found that K showed an obvious catalytic activity on gasification, and decreased the steam gasification temperature for 100°C, and the saturated addition of K catalysts was about 10% for the Hohhot coal steam gasification. A homogeneous phase model, shrinking core model, and integrated model were applied to correlate the data of conversion with time and to estimate the reaction rate constants under different temperatures. The results of simulation showed that the integrated model was best suitable for the TR and the TD steam gasification process, and the shrinking core model was best suitable for the gasification processes of TR-10K and TD-10K. The integrated model was used for solving kinetics parameters of the TR and the TD steam gasification, and the shrinking core model was used for the TD-10K. It was found that the E is 55.06 kJ·mol−1 for the TD-10K, 132.19 kJ·mol−1 for the TR, and 144.38 kJ·mol−1 for the TD.