Zhaosheng Yu

Experimental and kinetic modeling of oxygen-enriched air combustion of municipal solid waste

The characteristics of oxygen-enriched air combustion of raw municipal solid waste (MSW) were studied by thermogravimetric analysis. Experiments on oxidative pyrolysis of MSW were carried out under different atmospheres (N(2), N(2):O(2)=7:3, N(2):O(2)=5:5, N(2):O(2)=4:6, and N(2):O(2)=2:8) at 30 degrees C/min. Two distinct peaks of weight loss were obtained according to the derivative thermogravimetric curves; one of them is centered on 305 degrees C with about 40% weight loss, and the second is centered on 420 degrees C with about 20% weight loss. Effects of oxygen concentration on the decomposition process and char combustion were analyzed, and then the process of oxygen-enriched air combustion of MSW was divided into four steps. Kinetic parameters were observed by direct non-linear regressions. According to the obtained data, the apparent activation energy and reaction order decreases along with the combustion process, while that of char combustion increases as oxygen concentration increases.

Investigation on thermochemical behavior of co-pyrolysis between oil-palm solid wastes and paper sludge

The pyrolysis characteristics of oil-palm solid wastes, paper sludge and their blends were studied via thermogravimetric analysis. Blends ranging from 10 wt.% to 90 wt.% on dosage ratio were prepared to investigate their co-pyrolysis behavior and kinetics. There was a synergistic interaction at low temperature during co-pyrolysis between oil-palm solid wastes and paper sludge. The synergistic interaction would improve thermochemical pyrolysis reactivity of the blends, which could be attributed to the hydrogenation role and the potential mineral catalytic effects on paper sludge pyrolysis. The value of average activation energy obtained by Starink and Friedmen methods did not gradually decline with the increasing proportion of oil-palm solid wastes in the blends. The lowest average activation energy was achieved when the percentage of oil-palm solid wastes was 70%, which was 152 kJ/mol by Starink and 149 kJ/mol by Friedmen, respectively.

Effects of additives on the co-pyrolysis of municipal solid waste and paper sludge by using thermogravimetric analysis.

By using thermogravimetric analysis (TGA), the effects of different additives (MgO, Al2O3 and ZnO) on the pyrolysis characteristics and activation energy of municipal solid waste (MSW), paper sludge (PS) and their blends in N2 atmosphere had been investigated in this study. The experiments resulted that these additives were effective in reducing the initial temperature and activation energy. However, not all the additives were beneficial to reduce the residue mass and enhance the index D. For the different ratios of MSW and PS, the same additive even had the different influences. The catalytic effects of additives were not obvious and the pyrolysis became difficult with the increase of the proportion of PS. Based on all the contrast of the pyrolysis characteristics, MgO was the best additive and 70M30P was the best ratio, respectively.

Hydrothermal carbonization of typical components of municipal solid waste for deriving hydrochars and their combustion behavior

In this work, five typical components were employed as representative pseudo-components to indirectly complete previous established simulation system during hydrothermal carbonization (HTC) of municipal solid waste. The fuel characteristics and combustion behavior of HTC-derived hydrochars were evaluated. Results clearly illustrated that the energy ranks of hydrochars were upgraded after HTC. For paper and wood, superior combustion performances of their hydrochars could achieve under suitable conditions. While for food, none positive enrichments on combustion loss rate were observed for hydrochars due to its high solubilization and decomposition under hot compressed water. It was noteworthy that a new weight loss peak was detected for paper and food, suggesting that new compounds were formed. For rubber, the HTC process made the properties of styrene butadiene rubber more close to natural rubber. Therefore, the first peak of hydrochars became significantly intense. While for plastic, only physical changes of polypropylene and polyethylene were observed.

Drying Kinetics and Characteristics of Sewage Sludge/Rice Straw Mixture

This study aimed at investigating thin-layer drying characteristics of sludge mixed with different rice straw contents (1, 2, 3, and 5% wb). The experimental results showed that adding 1, 2, and 3% (wb) rice straw to sludge is helpful to improve the drying rate of sludge as the surface area and cracks increase but the drying rate of the sludge mixed with 5% (wb) rice straw decreases with a reduction in thermal conductivity. When the content of rice straw is 2% (wb), the increased amplitude of drying rate is the highest, 14.6, 14.8, 16.0, and 17.6% at 100, 120, 140, and 160°C, respectively. The model proposed by this study showed better prediction compared with the other models and satisfactorily described the drying characteristics of sludge/rice straw mixture as well and is applicable under the given experimental conditions. The values of R2, root mean square error (RMSE), and χ2 varied from 0.99935 to 0.99992, 0.00295 to 0.00830, and 0.00001 to 0.00007, respectively.

Structural Design and Numerical Simulation for Furnace Arch in Straw-fired Boiler

Aiming at distinct straw in different areas of China, this paper has schemed out a kindly straw-fired boiler which can burn different kind of straws. The 200t/d straw-fired boiler has been taken as subject investigated, when Air to fuel stoichiometric ratio is 1.85, the ratio of primary air and secondary air is 6.5:3.5 and the air temperature is 180°C, different straw in the same furnace arch straw-fired boiler has been burned and related mathematical modeling methods have been established in order to simulate in-bed combustion process using a share software FLIC (developed by Sheffield University Waste Incineration Centre). In the computation out-of-bed gas combustion and furnace arch radiation were simulated by commercial software FLUENT, not only the temperature, velocity and concentration distributing of the top of bed but also the solid temperature profile of in-bed and burning character of out-of-bed have been obtained. The simulation results showed that the calculation is in coincidence with the relative literature data. it has also proved that the furnace arch structure design in this paper is reasonable and useful.

A study on microwave-assisted fast co-pyrolysis of chlorella and tire in the N 2 and CO 2 atmospheres

The microwave-assisted fast co-pyrolysis of chlorella and tire with additive under N2 and CO2 atmospheres were investigated. The pyrolysis profiles, yields of three-phase, the chemical composition of liquid and the ultimate analyses of solid residues were gained. With the tire ratio increasing, all the characters had the changes. The finial temperature had a wave change. The yield of liquid decreased and the chemical composition obtained in liquid of oxygenates compounds decreased, while hydrocarbon compounds increased, among which aromatic hydrocarbons had the highest content. The yield of solid increased, the HHV had a wave change and the values of H/C decreased. Under CO2 atmosphere, the final temperatures were lower with 70% and 100% chlorella ratios, the yield difference of liquid reached the minimal with 70% and 30% chlorella ratios. According to the quantity and quality of liquid and solid, and the former results, 50% percentage of tire was the suitable ratio.

Forecasting the byproducts generated by hydrothermal carbonisation of municipal solid wastes.

The influences of temperature and residence times on the conversion and product distribution during hydrothermal carbonisation of municipal solid wastes were investigated. Analysis of variance and reaction severity were used to comprehensively analyse the experimental results. Analysis results showed both reaction temperature and residence time had varying degrees of impact on production distribution and hydrochars characteristic, while the effect of combine temperature and time was negligible. It is novel to find that the products yield was a linear function of the logarithm of the reaction ordinate. Base on comprehensive consideration, 240 °C to 260 °C and 50 min to 60 min would be the optimised reaction region to achieve relatively better economic benefits for hydrothermal carbonisation of municipal solid waste. By employing the analysis results and estimated models of high heating value and solid yield established in this article, predicting the product characteristics that have not been explored experimentally become possible.

Co-pyrolysis kinetics of sewage sludge and bagasse using multiple normal distributed activation energy model (M-DAEM)

In this study, the kinetic models of bagasse, sewage sludge and their mixture were established by the multiple normal distributed activation energy model. Blending with sewage sludge, the initial temperature declined from 437 K to 418 K. The pyrolytic species could be divided into five categories, including analogous hemicelluloses I, hemicelluloses II, cellulose, lignin and bio-char. In these species, the average activation energies and the deviations situated at reasonable ranges of 166.4673-323.7261 kJ/mol and 0.1063-35.2973 kJ/mol, respectively, which were conformed to the references. The kinetic models were well matched to experimental data, and the R2 were greater than 99.999%y. In the local sensitivity analysis, the distributed average activation energy had stronger effect on the robustness than other kinetic parameters. And the content of pyrolytic species determined which series of kinetic parameters were more important.

Ultrasonic pretreatment effects on the co-pyrolysis of municipal solid waste and paper sludge through orthogonal test

In this study, the influences of ultrasonic pretreatment factors (frequency, power, treatment time) on blends of municipal solid waste (MSW) and paper sludge (PS) with additive (MgO) was explored, through orthogonal experiments design. The optimum operating condition wanted to be acquired. However, for the ultimate (H/C) and ash analysis after pretreatment, solid residue mass and oxygenates compounds contents in products, the influences of factors were in different results. With adding PS unceasingly, the contents of hydrocarbon compounds decreased. And the ultrasonic pretreatment had the obvious influence with high PS percentage. Longer treatment time resulted to the lower content of oxygenates compounds. After adding MgO, the residue mass reduced, which meant MgO had the catalytic action, and the oxygenates compounds content reduced only with 100 kHz, which had the sonochemical effect.