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Multi-walled carbon nanotubes (MWCNTs) have remarkable properties. However, their thermal stability characteristics, which may represent potential hazards during the production or utilization stage, concern unsafe or unknown properties researches. Our aim was to analyze the thermokinetic parameters of different heating rates by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG), and then to compare thermal decomposition energy parameters under various conditions by well-known kinetic equations. MWCNTs were acidified via nitric acid (HNO) in various concentrations from 3 to 15 N and were characterized by means of Fourier transform infrared (FTIR) spectrometry. For original and modified MWCNTs, we further identified the thermal degradation characteristics of the functional group by TG-FTIR. Finally, we established an effective and prompt procedure for receiving information on thermal decomposition characteristics and reaction hazard of MWCNTs that could be applied as an inherently safer design during normal or upset operation. [ABSTRACT FROM AUTHOR]

This study investigated the role played by green thermal analysis technology in promoting the use of resources, preventing pollution, reducing energy consumption and protecting the environment. The chemical tert-butyl peroxybenzoate (TBPB) has been widely employed in the petrifaction industries as an initiator of polymerization formation agent. This study established the thermokinetic parameters and thermal explosion hazard for a reactor containing TBPB via differential scanning calorimetry (DSC). To simulate thermokinetic parameters, a 5-ton barrel reactor of liquid thermal explosion model was created in this study. The approach was to develop a precise and effective procedure on thermal decomposition, runaway, and thermal hazard properties, such as activation energy ( E), control temperature ( CT), critical temperature ( TCR), emergency temperature ( ET), heat of decomposition ( ∆H), self-accelerating decomposition temperature ( SADT), time to conversion limit ( TCL), total energy release ( TER), time to maximum rate under isothermal condition ( TMR), etc. for a reactor containing TBPB. Experimental results established the features of thermal decomposition and huge size explosion hazard of TBPB that could be executed as a reduction of energy potential and storage conditions in view of loss prevention. [ABSTRACT FROM AUTHOR]

The effect of initial temperatures (100, 150, and 200 °C), operating pressures (101 and 202 kPa), and various loading oxygen concentrations (21, 17, 14...oxygen vol.%) on the flammability hazard evaluations for the mixtures of benzene and methanol (100/0, 75/25, 50/50, 25/75, and 0/100 vol.%) by using rough set method, was studied. The results indicated that the most important influence factor was the operating pressure. There is no significant difference in the safety assessment for the different concentrations of mixtures. This study proposed a helpful reference for a related practical plant combined with experimentally and theoretically feasible way for flammability prevention and protection. [ABSTRACT FROM AUTHOR]

Dicumyl peroxide (DCPO) is usually employed as an initiator for polymerization, a source of free radicals, a hardener, and a linking agent. In Asia, due to its unstable reactive nature, DCPO has caused many thermal explosions and runaway reaction incidents in the manufacturing process. This study was conducted to elucidate its essentially thermal hazard characteristics. In order to analyze the runaway behavior of DCPO in a batch reactor, thermokinetic parameters, such as heat of decomposition (Δ H) and exothermic onset temperature ( T), were measured via differential scanning calorimetry (DSC). Thermal runaway phenomena were then thoroughly investigated by DSC. The thermokinetics of DCPO mixed with acids or bases were determined by DSC, and the experimental data were compared with kinetics-based curve fitting of thermal safety software (TSS). Solid thermal explosion (STE) and liquid thermal explosion (LTE) simulations of TSS were applied to determine the fundamental thermal explosion behavior in large tanks or drums. Results from curve fitting indicated that all of the acids or bases could induce exothermic reactions at even an earlier stage of the experiments. In order to diminish the extent of hazard, hazard information must be provided to the manufacturing process. Thermal hazard of DCPO mixed with nitric acid (HNO) was more dangerous than with other acids including sulfuric acid (HSO), phosphoric acid (HPO), and hydrochloric acid (HCl). By DSC, T, heat of decomposition (Δ H), and activation energy ( E) of DCPO mixed with HNO were calculated to be 70 °C, 911 J g, and 33 kJ mol, respectively. [ABSTRACT FROM AUTHOR]

Pooling lauroyl peroxide (LPO) with nitric acid, we used differential scanning calorimetry (DSC) to assess the thermokinetic parameters, such as exothermic onset temperature ( T), heat of decomposition (Δ H), frequency factor ( A), and the other safety parameters. When LPO was contaminated with nitric acid (HNO), we found the exploder 1-nitrododecane. Obvious products were sensitive and hazardous chemicals. Concentration reaching 1-12 N HNO emitted a large amount of heat. This study combined with curve-fitting method to elucidate its unsafe characteristics and thermally sensitive structure to help prevent runaway reactions, fires and explosions in the process environment. According to the findings and the concept of inherently safer design, LPO runaway reactions could be adequately prevented in the relevant plants. [ABSTRACT FROM AUTHOR]

Cumene hydroperoxide (CHP) being catalyzed by acid is one of the crucial processes for producing phenol and acetone globally. However, it is thermally unstable to the runaway reaction readily. In this study, various concentrations of phenol and acetone were added into CHP for determination of thermal hazards. Differential scanning calorimetry (DSC) tests were used to obtain the parameters of exothermic behaviors under dynamic screening. The parameters included exothermic onset temperature ( T), heat of decomposition (Δ H), and exothermic peak temperature ( T). Vent sizing package 2 (VSP2) was employed to receive the maximum pressure ( P), the maximum temperature ( T), the self-heating rate (d T/d t), maximum pressure rise rate ((d P/d t)), and adiabatic time to maximum rate ((TMR)) under the worst case. Finally, a procedure for predicting thermal hazard data was developed. The results revealed that phenol and acetone sharply caused a exothermic reaction of CHP. As a result, phenol and acetone are important indicators that may cause a thermal hazard in the manufacturing process. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (HO), historically, due to its broad applications in the chemical industries, has caused many serious fires and explosions worldwide. Its thermal hazards may also be incurred by an incompatible reaction with other chemical materials, and a runaway reaction may be induced in the last stage. This study applied thermal analytical methods to explore the HO leading to thermal accidents by incompatibility and to discuss what might be formed by the upset situations. In this study, the thermal hazard analyses were conducted with various solvents, propanone (CHCOCH), FeO, FeSO, HSO, HCl, HNO, HPO, NaOH, LiOH, and KOH which were deliberately selected to individually mix with HO for investigating the degree of hazard. Differential scanning calorimetry (DSC) was employed to evaluate the thermal hazard of HO-mixed ten chemicals. The results indicated that HO is highly hazardous while separately mixed with ten materials, as a potential contaminant. Fire and explosion hazards could be successfully reduced if the safety-related data are suitably imbedded into manufacturing processes. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are the main factors involved in pollution control and global warming in industrialized nations. Various treatment methods involving incineration, adsorption, etc., were employed to reduce VOCs concentration. Various absorbents, such as activated carbon, zeolite, silica gel or alumina, and so on were broadly used to adsorb VOCs in various industrial applications. Differential scanning calorimetry (DSC) was handled to analyze the thermal characteristics of absorbents. Typically, a scanning electron microscope (SEM) has been used to evaluate the structure variation of absorbents under high temperature situations. In view of pollution control and loss prevention, versatility and analysis of recycled adsorbents are necessary and useful for various industrial applications. [ABSTRACT FROM AUTHOR]

A hierarchical set of kinetic models were proposed and discussed for simulation of autocatalytic decomposition of cumene hydroperoxide (CHP) in cumene at low temperatures. The hierarchy leads from a formal model of full autocatalysis, which is based on conversion degree as a state variable, through a two-stage autocatalytic concentration-based model to a meticulous multi-stage model of the reaction. By the ForK (Formal Kinetics) and DesK (Descriptive Kinetics) software, developed by ChemInform Saint Petersburg (CISP) Ltd., the related kinetic parameters and their significance have also been estimated and elucidated. Through this best-fit approach, it is possible to formulate a systematic methodology on the kinetic studies for thermal decomposition of typical organic peroxides with autocatalytic nature, specifically at low temperature ranges. [ABSTRACT FROM AUTHOR]

Lauroyl peroxide (LPO) is a typical organic peroxide that has caused many thermal runaway reactions and explosions. Differential scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data. Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were necessary and useful for inherently safer design. [ABSTRACT FROM AUTHOR]

This study aimed to locate VOC emission sources and characterized their emitted VOCs. To avoid interferences from vehicle exhaust, all sampling sites were positioned inside the refinery. Samples, taken with canisters, were analyzed by GC–MS according to TO-14 method. The survey period extended from Febrary 2004 to December 2004, sampling twice per season. To interpret a large number of VOC data was a rather difficult task. This study featured using ordinary application software, Excel and Surfer, instead of expensive one like GIS, to overcome it. Consolidating data into a database on Excel facilitated retrieval, statistical analysis and presentation in the form of either table or graph. The cross analysis of the data suggested that the abundant VOCs were alkanes, alkenes, aromatics and cyclic HCs. Emission sources were located by mapping the concentration distribution of these four types of VOCs in terms of contour maps on Surfer. During eight surveys, five emission sources were located and their VOCs were characterized. [ABSTRACT FROM AUTHOR]

Abstract  The performance of content-based image retrieval (CBIR) systems is largely limited by the gap between the low-level features and high-level semantic concepts. In this paper, a probabilistic semantic network-based image retrieval framework using relevance feedback is proposed to bridge this gap, which not only takes into consideration the low-level image content features, but also learns high-level concepts from a set of training data, such as access frequencies and access patterns of the images. One of the distinct properties of our framework is that it exploits the structured description of visual contents as well as the relative affinity measurements among the images. Consequently, it provides the capability to bridge the gap between the low-level features and high-level concepts. Moreover, such high-level concepts can be learned off-line, and can be utilized and refined based on the user’s specific interest during the on-line retrieval process. Our experimental results demonstrate that the proposed framework can effectively assist in retrieving more accurate results for user queries. [ABSTRACT FROM AUTHOR]