Hao Shen’s research while affiliated with Sun Yat-sen University and other places

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Publications (16)


Effects of several cosolvents and non-solvents on ester true solvents in nitrocellulose lacquer thinner
  • Article

November 2022

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65 Reads

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2 Citations

Progress in Organic Coatings

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Hao Shen

Choosing better organic solvents and providing appropriate mixing ratios for nitrocellulose (NC) lacquer thinner is a very important topic in NC lacquer thinner industries. This paper studied the effects of cosolvents and non-solvents on ester true solvents in NC lacquer thinner. The research objects were ester true solvents (Methyl Acetate (MA) and Ethyl Acetate (EA)), alcohol cosolvents (Ethyl Alcohol (ETA), Isopropyl Alcohol (IPA), and Isobutyl Alcohol (IBA)) and non-solvents (n-Hexane (NX), n-Heptane (NP), and Petroleum Ether (PE)). Nitrocellulose lacquer dissolution experiments, explosion characteristic experiments, and algal growth inhibition experiments were performed. The results indicated that: the mixed organic solvents containing cosolvent of ETA were better than those containing the other two cosolvents (IPA and IBA) in terms of dissolution rates, explosion characteristics, and environmental influences. For non-solvent, NX was a better non-solvent as the dissolution rates of mixed organic solvents (containing MA, ETA, and NX) all kept at relatively higher levels at different non-solvent proportions. NX and PE were safer non-solvents when the concentration of non-solvent was relatively lower (16.7 %). The IC50 values of mixed organic solvents containing non-solvent NT on Dunaliella bardawil were a little bit higher than those of mixed organic solvents containing NX or PE when the volume ratios of non-solvent were the same. In conclusion, the mixed organic solvent of MA (ester true solvent), ETA (alcohol cosolvent), and NX (non-solvent) with a volume ratio of about 4:1:1 was a relatively ideal composition for the industrial application of NC lacquer thinner.


Figure 1. Schematic diagram of sawdust stack self-heating experiment.
Figure 3. The TG curves of poplar sawdust samples at different heating rates.
Figure 6. The OTU number of collected samples: (a) bacteria and (b) fungus, and the Chao richness index of collected samples: (c) bacteria and (d) fungus. Mean value (n = 3) with standard deviation.
Experiment process and samples collected in the self-heating experiment.
Activation energies of poplar sawdust samples calculated by Friedman method.

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Poplar Sawdust Stack Self-Heating Properties and Variations of Internal Microbial Communities
  • Article
  • Full-text available

January 2022

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48 Reads

Materials

The heat accumulation generated by microbial metabolic activities during the storage of the sawdust may lead to spontaneous combustion accidents. This paper studied the Critical Ambient Temperature (CAT) variation of poplar sawdust at different stack dimensions and investigated the physicochemical properties as well as microbial community dynamics during the self-heating process of poplar sawdust stacks. From the self-heating substances test experiments and Frank-Kamenetskii (FK) theory, it was found that the CAT of poplar sawdust stacks would decrease from 158.27 °C to 102.46 °C with the increase of stack size from 0.1 m to 3.2 m. From the sawdust stack self-heating experiments, microbial metabolic activities were enhanced with the increasing moisture content (by watering) and oxygen (by turning over), which led to a remarkable increase of the sawdust stack temperature and the rapid decomposition of biochemical components (especially cellulose and hemicellulose). From the microbiological community analysis, at the thermophilic stage (around 60 °C, large amounts of heat release in compost bin), the existence of thermostable bacteria (such as Brevibacillus thermoruber, Bacillus thermoamylovorans and Paenibacillus barengoltzii belonging to Firmicutes) played an important role in degrading organic substances. The heat generated by the microbial metabolic activities might lead to spontaneous combustion eventually if sawdust stack is large enough. Therefore, the sawdust should be stacked in a cool and dry area while avoiding large amounts of storage in high humidity environments.

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Experimental study on artificial lightning ignition phenomenon and model of the fuel bed

June 2021

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32 Reads

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2 Citations

As global warming continues, wildland lightning fires have exhibited an increasing trend. The phenomenon of lightning ignition and a model are urgent research fields. In this study, an impulse current generator was used to study artificial lightning ignition. Ignition phenomena for several fuel beds were compared. Flames in the grass bed existed in the form of particles, but these particle flames had a short duration and were extinguished by the shock waves from the artificial lightning. It is noteworthy that a 10/350 μs impulse current could ignite a cotton fibre bed and produce sustained and stable combustion. An artificial lightning ignition model for the fuel bed was established. The model was verified by artificial lightning ignition experiments. The results show that the model could be applied to grass and needle fuel beds and waveforms of 10/350 μs impulse current and short continuing current. The findings of this study provide valuable information for understanding the mechanism of lightning ignition.


The impulse current generator circuit diagram
The typical current and voltage curves. Note: The grass bed was Cleistogenes squarrosa (Trin.) Keng. The peak current (Ip) = 10.76 kA, the bulk density (ρ) = 0.1062 g/cm³, the moisture content (x) = 7.14%. The waveform was 10/350 μs, and the current direction was plate to needle
a–f The phenomenon of the artificial lightning ignition
a, b The samples before and after the experiment
The measured values and fitted values of Ec. Note: Points that are closer to the line have a greater concordance between the fitted values and the measured values
Experimental analysis of artificial lightning breakdown and ignition characteristics in grassland

August 2020

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452 Reads

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2 Citations

Theoretical and Applied Climatology

Lightning fire is an important influencing factor of grassland ecology. It is one of the important ignition sources of grassland fire. The previous researches on lightning fires were mainly focused on forests, but researches on grassland were insufficient. In this paper, the impulse voltage generator was used to evaluate the breakdown characteristics of grass bed. The relationship of breakdown voltage to moisture content and bulk density was obtained. Based on the impulse current generator, an artificial lightning ignition prediction model of impulse current was derived. Results show that the breakdown voltage of grass bed decreases rapidly with the increase of moisture content. With the increase of peak current, the total lightning energy increases, while the heating efficiency decreases.



Investigation of lightning ignition characteristics based on an impulse current generator

December 2019

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103 Reads

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8 Citations

Lightning strike is an important ignition source of forest fires. Artificial lightning discharge is a method for studying lightning fires. However, there is not enough data on the ignition of combustible materials caused by artificial lightning discharge. Previous studies on lightning ignition have focused on the heating and ignition effects of long continuing current (LCC), but the function of the impulse current that occurs before the LCC has not been taken into account. In this paper, an impulse current generator of 8/20 μs was used to simulate the ignition effect of impulse current on conifer needle beds. Different current waveforms have different ignition characteristics. We compared five kinds of conifer needle beds. The average of the current needed to ignite the needle bed of Larix gmelinii (Ruprecht) Kuzeneva was the smallest, and the average of the breakdown voltage was the smallest for the needle bed of Pinus massoniana Lamb. The total energy input to the conifer needle beds was fitted as a multiple log‐linear regression model. The heating energy proportion value varies with different bulk densities, current amplitudes, and moisture contents. Based on this data, the heating energy of the impulse current transferred to the needles can be predicted. This information in conjunction with previous research on LCC was used to derive a lightning ignition prediction model of the full waveform for conifer needle beds. With the rise of global temperature, the forest lightning fire is very serious. Forest fires have seriously damage to the ecosystem and cause great economic losses. In this manuscript, the ignition characteristics of lightning strike were studied, and the prediction model of lightning ignition was established.


The spontaneous combustion mechanism of sawdust from the aspect of biochemical components

November 2019

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422 Reads

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5 Citations

Cellulose, hemicellulose and lignin are generally recognized as the main components of sawdust. In this paper, the spontaneous combustion mechanism of sawdust was studied from the aspect of these components. The thermogravimetry analysis and biochemical component analysis showed that the lignin decomposed evidently at the induction period of thermal decomposition of sawdust, and the lignin contents of sawdust also presented positive correlation with their spontaneous combustion risk. Scanning electron microscope, fourier transform infrared spectroscopy and X-ray photoemission spectra were implemented further. The results showed that: the cellulose remained stable at the induction period; for hemicellulose, the oxidation reaction took place, but it was very weak. However, for lignin, the dehydration reaction (loss hydroxyl group of alcohols) took place evidently so that the lignin exhibited an apparent porous structure. Therefore, the dehydration reaction of lignin might greatly affect the spontaneous combustion of sawdust.



Effect of initial temperature and initial pressure on vapor explosion characteristics of nitro-thinner

September 2019

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13 Reads

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7 Citations

Journal of Loss Prevention in the Process Industries

Combustible vapor explosion characteristic test device (NEU-G-EL) was set up to study the explosion characteristics of nitro-thinner under the conditions of different pressure and temperature. The experimental results showed: The LLEL (Lower Limit of Explosion) of vapor explosion of nitro-thinner was between 1.0% and 2.0%, while the LUEL (Upper Limit of Explosion) was between 4.5% and 10.0%, and the △L (Range of Explosion Limit) was between 3.5% and 8.0%. The LLEL, LUEL, △L and the (△P)max (maximum over-pressure) will increase with the increase of the initial pressure, and the (△P)max of Nitro-thinner vapor explosion will decrease with the increase of the initial temperature.


The influence of soluble components on spontaneous combustion risk of sawdust samples

October 2018

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208 Reads

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10 Citations

Thermochimica Acta

Sawdust is a common by-product of wood processing industry. Spontaneous combustion would even take place under unfavorable conditions of storage and transportation. In this study, self-heating substances test experiments, Thermogravimetry (TG) experiments and Frank-Kamenetskii (FK) theory were used to compare the spontaneous combustion risk of three sawdust samples (DCP, CFE, and LOH). The results revealed that the Critical Ambient Temperatures (CATs) of DCP, CFE and LOH were 81.2 (±0.3), 96.0 (±0.4) and 125.9 (±0.3)°C respectively when the stack dimension reached 1.6 m. Lower CAT for sample indicated that it had a higher spontaneous combustion risk. On the other hand, the relationship between spontaneous combustion risk and soluble components of three sawdust samples was studied with Gas Chromatographic and Mass Spectrometric (GC–MS) experiments. The results found that if a sawdust sample contained more soluble components than other sawdust samples, the spontaneous combustion risk of this sample would also higher than other sawdust samples, and vice versa.


Citations (12)


... In turn, from 2005 to 2008 [14,15]. In the same Muli County (Li'er village), a lightning-induced fire took the lives of 27 firefighters and 4 residents in March 2019 [14,16]. Liu et al. [17] reported that lightning strikes caused 45% of the wildfires in the boreal forest of northeast China. ...

Reference:

Lightning-Induced Wildfires: An Overview
Experimental study on artificial lightning ignition phenomenon and model of the fuel bed

... These solvents are designed to dissolve or dilute paints, varnishes, and other coatings, making them easier to apply or remove. Paint thinners typically consist of a mixture of organic solvents, such as mineral spirit, turpentine, toluene, xylene, and acetone, among others [1][2][3][4][5][6]. ...

Effect of initial temperature and initial pressure on vapor explosion characteristics of nitro-thinner
  • Citing Article
  • September 2019

Journal of Loss Prevention in the Process Industries

... Given this consideration, some research has been completed to analyze the impulse current. Feng et al. [12] used the impulse current generator to investigate lightning-induced ignition. They derived a model for the impulse current based on the impulse current generator. ...

Experimental analysis of artificial lightning breakdown and ignition characteristics in grassland

Theoretical and Applied Climatology

... Ignition occurred at 10/350 µs impulse current; hence, their model applies to grass and needle fuel beds with a waveform of 10/350 µs impulse current and short-continuing current. In another work, Feng et al. [56] studied the lightning-ignition mechanism using an impulse current generator. They used an impulse current generator of 8/20 s to study the ignition influence of the impulse current on conifer needle beds. ...

Investigation of lightning ignition characteristics based on an impulse current generator

... These solvents are designed to dissolve or dilute paints, varnishes, and other coatings, making them easier to apply or remove. Paint thinners typically consist of a mixture of organic solvents, such as mineral spirit, turpentine, toluene, xylene, and acetone, among others [1][2][3][4][5][6]. ...

Comparison of six ester components in nitrocellulose lacquer thinner from the aspects of dissolution rates, explosion characteristics and environmental influence
  • Citing Article
  • February 2020

Progress in Organic Coatings

... The compositions and some properties of the raw biomasses are shown in Table 1, where it can be seen that their content of water is appropriate to be used in thermochemical processes. The elemental compositions and the amounts of lignocellulosic material are typical of wood sawdusts [32,33] and grain shells [34]. However, important differences between the various biomasses can be noticed: the contents of cellulose and lignin in rice husk are smaller than in wood sawdusts, and, on the contrary, the content of ash in rice husk is high and, consequently, its volatile matter is low, associated with less C and O. ...

The spontaneous combustion mechanism of sawdust from the aspect of biochemical components

... The degradation of lignocellulosic wastes is also attributed to the metabolism of indigenous microorganisms. Xu et al. [8] had found that when the dimensions of a stack of sawdust increased from 0.1 to 1.6 m, the Critical Ambient Temperature (CAT) of Dalbergia cochinchinensis, Cupressus funebris, Larix olgensis all would gradually decrease, especially for Dalbergia cochinchinensis, whose CAT could reduce from 155 • C to 81.2 • C. It can be found from the above studies that the heat accumulated by microbial metabolism might reach the CATs of sawdust stacks, which would then cause thermal decomposition and even spontaneous combustion. Therefore, it is necessary to obtain the characteristics of the spontaneous combustion of sawdust stack. ...

The influence of soluble components on spontaneous combustion risk of sawdust samples
  • Citing Article
  • October 2018

Thermochimica Acta

... These methods allow one to study the gases released during thermal decomposition, to trace the mechanisms of chemical decomposition. In [2], based on the Frank-Kamenetskii theory, the effect of NC volume on the temperature of its decomposition and on the temperature of thermal explosion was studied. In [3], the effect of gunpowder aging on the combustion rate was studied. ...

The Thermal Properties of Nitrocellulose: From Thermal Decomposition to Thermal Explosion
  • Citing Article
  • February 2018

... Thiourea dioxide reducing agent is environmentally friendly and also has an important strong point of not being easily decomposed compared to traditional sodium hydrosulfite-based reducing agents when in contact with moisture. Thiourea dioxide can discharge more heat and gas than sodium hydrosulfite at high temperature [11]. It means that thiourea dioxide has good heat resistance stability, and its decomposition rate is milder than that of sodium hydrosulfite, even in a high temperature (80-100 o C). ...

Comparison of thermal hazards of sodium dithionite and thiourea dioxide from thermal analysis (DSC-TG), small-scale self-heating experiments and FTIR smoke gas analysis
  • Citing Article
  • June 2017

Fire Safety Journal

... We came to the conclusion, after a detailed literature survey, that only limited experimental methods have been developed to check the self-heating and spontaneous ignition of agricultural products, e.g., coal, wheat, and hay [5,[16][17][18][19][20][21], including basket heating, the crossing-point temperature method proposed by Worden (2011), thermogravimetric analysis (TGA) conducted by Khattab (1999), the Ordway apparatus used by Thompson (1928), and the Mackey apparatus method proposed by Khattab et al. (1999) [22]. Also, some researchers proposed solutions to measure and control external weather conditions of the storage area only, and they aim to improve safety mechanisms there [16,20,21]; one study focused on chemical processes to identify gases produced during smoldering [17], and little work has been done to investigate factors contributing to SC and its effect on cotton quality [5,19]. ...

A study on the thermal decomposition temperature (TDT) and critical ambient temperature (CAT) of cotton
  • Citing Article
  • January 2017

Journal of Thermal Analysis and Calorimetry