Explosion Treatment Research Articles

Experimental determination and calculation of powder mixture heating temperature at explosive compaction

The paper presents the experimentally determined heating temperature of mixed chromium carbide powders and titanium bond under explosive loading on a metal substrate. Pressure of powder mixture compression in shock waves during explosive pressing was 2,5 GPa. The experiment involved recording a thermal cycle on the back side of the coated metal substrate serving as a heat receiving element. It also solved a problem of non-stationary heat conduction until the calculated and experimental thermal cycles coincided. Initial conditions were chosen assuming that the compacted material is uniformly heated to a certain average temperature by the time the shock-wave processes end. Required thermophysical properties of the compacted material were determined by the laser flash method using the LFA 427 unit («Netzsch», Germany). According to calculations, powder mixture heating temperatures were 208 °C and 225 °C for adiabatic approximation and taking into account heat transfer into the environment, respectively. The obtained values were compared with ones calculated by the increase in enthalpy during the shock wave processing (these calculations used solid material densities under normal conditions and final powder material density determined after explosive treatment to be 199 °C and 220 °C, respectively), and it was found that they differ insignificantly. Thus, the assumption of equal material density in a shock wave and solid density does not lead to a significant error and can be used for practical calculations.

Thermally enhanced hydrolysis for treatment of pesticides and explosives

AbstractThermally enhanced hydrolysis of halogenated alkanes such as 1,1,1‐trichlorethane has become a proven method of in situ soil and groundwater remediation. Electrical resistance heating is commonly used to heat soil and groundwater to accelerate the rate of hydrolysis. This article provides practical information to extend the hydrolysis remediation toolkit to include treatment of common pesticides and explosives. Sites with comingled volatile compounds, pesticides, and/or explosives can also be treated via a single solution.

Environmentally-Friendly Extraction of Cellulose Nanofibers from Steam-Explosion Pretreated Sugar Beet Pulp.

Cellulose nanofibers (CNFs) with an average diameter of 22 nm were prepared from sugar beet pulp (SBP) via an environmentally-friendly method. Steam-explosion pretreated SBP was treated with hydrogen peroxide (H2O2) bleaching, high-speed blending, and ultrasonic treatment. Thermogravimetric analysis showed that hemicellulose was partially hydrolyzed in the steam-cooking stage, pectin was removed in the explosion stage, and lignin was removed by H2O2 bleaching. The removal of non-cellulosic components was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. Morphological analysis showed that steam-explosion pretreatment largely extracted the binder materials of hemicellulose and pectin. This exposed the microfibrillated cellulosic fibers, which promoted subsequent nanofibrillation. X-ray diffraction showed that the CNFs had a crystallinity index of 62.3%. The CNFs had good thermal stability, and thus have potential for use as fillers in polymer matrices. The only chemical reagent used in this green method was H2O2. Combining H2O2 bleaching with steam explosion, high-speed blending, and ultrasonic treatment reduced the overall energy consumption and increased the efficiency of the CNFs extraction. The method, therefore, has potential application in industrial processes.

Isolation and characterization of cellulosic fibers from kenaf bast using steam explosion and Fenton oxidation treatment

Degumming is the dominant method to isolate cellulosic fibers in the textile industry. High content of lignin is the principle obstacle in bast-fibers degumming. In order to remove lignin efficiently, the treatment using steam explosion coupled with Fenton oxidation was conducted on kenaf bast in this study. The influence and mechanism of the combined treatment of steam explosion and Fenton oxidation were studied. Fiber microstructure, composition proportion and distribution, cellulose Segal crystallinity and polymerization as well as residual lignin structure were analyzed. The results showed that the pretreatment of steam explosion could sufficiently extract most of the hemicellulose from kenaf bast. Also, the Fenton oxidation followed by alkaline boiling could effectively remove the lignin from the fiber, especially from the fiber surface. The refined dry fibers produced only remained 8.82% of hemicellulose and 9.36% of lignin. And the whole treatment process didn’t change the cellulose crystalline structure but could gradually degrade hemicellulose, lignin and other amorphous gummy matter as well as disordered areas in cellulose, leading to the increase of fiber Segal crystallinity from 62.02 to 70.12%. Part of cellulose was damaged with the increase of degumming intensity, resulting in the decrease of the polymerization degree of cellulose. Meanwhile, the structure of residual lignin changed during the degumming stages of steam explosion, Fenton oxidation and alkaline boiling. All the results revealed that the treatment of combined steam explosion and Fenton oxidation is significantly effectual for isolating bast-fibers.

High mechanical performance of AISI304 stainless steel plate by surface nanocrystallization and microstructural evolution during the explosive impact treatment

The surface treatment on AISI304 stainless steel plate was successfully carried out by explosive impacting technique. We have obtained a high mechanical performance and corresponding fine microstructures compared to its base metal by the technique. Experimental results indicate that nanograins (around 30nm of diameter) with random crystallographic orientations formed in the top impacted surface and many deformation bands in the subsurface layers. The explosive impact generated deformation induced martensite (DIM) in the plates, where DIM volume fraction increased firstly and then decreased toward inside. These surface nanocrystallization and microstructural evolution, which can be attributed to the co-actions of the grain-refinement, deformation-bands and phase transformation effects, can enhance surface hardness and mechanical properties remarkably not only near surface but entire plate.

A green degumming process of ramie

Ramie provides the longest and strongest natural fiber in textile industry, but its traditional degumming process is costly and requires a large amount of alkali, which causes serious environmental concerns. In the current work, a steam explosion (STEX) treatment followed by sodium percarbonate (SP) soak degumming process was investigated. Microstructure, chemical composition and mechanical properties of the refined ramie fibers were comprehensively characterized. The residual gum content was below 5%, the fineness was higher than 1600 Nm (6.25 dtex), the breaking tenacity was 5.4 cN/dex, and the whiteness was above 50%. All of the properties met the requirements of Chinese national standard, and the breaking tenacity and whiteness were notably better than those of the fibers degummed traditionally. In addition, environmental impacts of the new degumming process were evaluated. Only 50% chemicals were needed for the new process, and chemical oxygen demand (COD) of the waste reduced to 35% of the traditional method. Therefore, the new method was more environment-friendly and economically feasible. It has great potential for industry applications.

A novel degumming process of kenaf

The high content of lignin is the major disadvantage for kenaf fiber separation. In order to remove lignin effectively as well as to improve the dispersion of kenaf fibers, a novel degumming process with steam explosion followed by Fenton treatment was applied in the present study. Fibers prepared by traditional chemical degumming process and raw kenaf samples were employed as control. The fiber microstructure, chemical composition, and physical and mechanical properties were characterized and analyzed in this paper. The results revealed that steam explosion coupled with Fenton treatment could effectively remove the gum materials from kenaf bast, which performed noticeably effectively in lignin removal. The refined dry fibers showed a clean and smooth surface. The average fineness of the refined dry fibers degummed by the novel process was measured to be higher than 70 dtex, which is much better than fibers prepared by the traditional chemical degumming process. It can be concluded that the novel degumming process of combined steam explosion and Fenton treatment is feasible and effective for kenaf degumming.

Assessment of Instant Catapult Steam Explosion Treatment on Rice Straw for Isolation of High Quality Cellulose

Instant catapult steam explosion (ICSE) was applied to treat rice straw for isolating high quality cellulose. After ICSE treatment under the condition of maintaining the pressure at 2.0 MPa for 11 min, the hemicellulose content decreased to 3.70% from the original 20.10%, and the content of α-cellulose was 72.02%. The enormous explosion power density provided by ICSE turned rice straw into cellulosic fibers with good accessibility, as well as it protected the cellulose fibers from being over-hydrolyzed. All of the straw cellulosic samples were analyzed by scanning electron microscopy (SEM), Fourier transformation infrared spectrometry (FTIR), and X-ray diffraction (XRD) to collectively examine the impact of ICSE treatment on the structure and morphology of the cellulose components. The recycled lignin was also analyzed by two-dimensional nuclear magnification resonance spectrometry (2D NMR) to understand the mechanisms underlying the ICSE treatment.

The Effect of Explosive Treatment on the Structure and Thermomechanical Properties of Filled Polytetrafluoroethylene

The effect of explosive treatment with variation in the shock pulse configuration and in the pressure within the shock front on the structure and thermomechanical properties of a composite of polytetrafluoroethylene with 30% polyarylate was investigated.

Steam explosion enhances digestibility and fermentation of corn stover by facilitating ruminal microbial colonization

The purpose of this study was to evaluate steam explosion as a pretreatment to enhance degradation of corn stover by ruminal microbiome. The steam explosion conditions were first optimized, and then the efficacy of steam explosion was evaluated both in vitro and in vivo. Steam explosion altered the physical and chemical structure of corn stover as revealed by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy, respectively, and increased its cellulose content while decreasing hemicellulose content. Steam-exploded corn stover also increased release of reducing sugars, rate of fermentation, and production of volatile fatty acids (VFAs) in vitro. The steam explosion treatment increased microbial colonization and in situ degradation of cellulose and hemicellulose of corn stover in the rumen of dairy cows. Steam explosion may be a useful pretreatment of corn stover to improve its nutritional value as forage for cattle, or as feedstock for biofuel production.

Investigation on the structure evolution of pre and post explosion of coal dust using X-ray diffraction

To reveal the effects of coal dust explosion on its crystal structures evolution, the micro structure of six different rank of coal dust and its explosion solid products had been studied using 20 L explosion sphere vessel and X-ray diffraction (XRD) analyzer. The correlations between structural parameters and explosion severity had been analyzed detailed. Results show that coal dusts with higher volatile matter contents (Vdaf), lower vitrinite reflectance (Ro,max) and less ash contents (Aad) show stronger explosion severity. The effects of vitrinite reflectance (Ro,max) on the explosion severity parameters present the same role as the influence of volatile matter contents (Vdaf). Coal dusts with developed porous structure (SBET and VBJH) also present higher explosion reactivity. Interestingly, six selected coal samples present the strongest explosion severity at the same optimum explosion concentration (250 g/m3). For the different rank raw coal, the difference of the shape and intensity of 002 peak varies greatly. With the decreasing of coal ranks, the 002 band tends to be blunt and the peak intensity is relatively short. Quantitative analysis show that the lattice parameters (La, Lc, and Navg) of six coal samples are found to relatively increase with increasing vitrinite reflectance (Ro,max), whereas the d002 slightly decreases. The explosion treatments have significant effects on the ordering of coal aggregate structure. Compared with raw coal sample, the relative intensity of 002 bands at about 26° is reduced by the explosion treatments, which would increase the degree of graphitization of the explosion solid products. With the increasing of explosion pressure, the relative intensity of 002 peak would be gradually decreased. However, the shape of 002 peak for the explosion solid products tend to be more asymmetric and blunter than that at lower explosion conditions. Compared with the parent coals, the inter-layer spacing d002, Lc and Navg of all explosion products would be slightly reduced correspondingly. However, there is no clear rule for the evolution of La parameter. Moreover, calculated aromaticity (fa) of the coals ranges from 0.2208 to 0.6883, which is linear positively increased with the coal maturity by vitrinite reflectance.

Evaluating anaerobic and aerobic digestion strategies for degradation of pretreated pine needle litter

The present study evaluated the effect of different pretreatments on unlocking the lignocellulosic composition of pine needle litter biomass followed by performance under aerobic/anaerobic digestion. The pretreatment strategies employed were milling, steam explosion, and chemical treatment with acid–base–acid. The results revealed that the most effective method of pretreatment of pine needle litter was the physico-chemical treatment (milling + steam treatment + acid–base–acid hydrolysis), which resulted in 65.92% increase in holocellulose content with a corresponding 21.34% decrease in total lignin content as compared to untreated control. The effect of pretreatments on anaerobic digestion using digested sludge as inoculums was evaluated through biochemical methane generation. During the liquid-phase anaerobic digestion process of different pretreated pine needle litter, the mechanically milled pine litter yielded a methane level of 5.53 ± 0.11 mmol CH4/g VSin in 40 days, which was 40.7% higher than during anaerobic digestion of untreated pine needle litter. The physico-chemical pretreatment resulted in 21.4% higher methane levels as compared to untreated pine litter. Additionally, the aerobic digestion of pretreated pine needle litter with white rot fungal strain, Cotylidia pannosa for 60 days at 30 °C, resulted in 95.5% decrease in holocellulose content and 52.3% decrease in total lignin content. Findings in the present study suggest that in spite of significant reduction in lignin content during the pretreatment, the addition of pine litter as a substrate inhibits anaerobic digestion process.

Effects of steam explosion on the characteristics of windmill palm fiber and its application to fiberboard

Windmill palm fiber (WPF) obtained from the leaf sheath was treated by steam explosion under the pressure of 2.0 MPa for 120 s to modify and improve the properties of the panels manufactured with it. For comparison, an alkali treatment and acid treatment have also been used to treat WPF. Fiber analysis, scanning electron microscopy (SEM) observation, Fourier transform infrared spectroscopy (FTIR) and chemical composition analysis showed that after the steam explosion treatment: (1) the length, width and fine elements of the windmill palm fibrils were more influenced by the steam explosion treatment than by the other two treatments. (2) A great number of spinulose spherical silica bodies and waxy layers were observed on the surfaces of all the fibers except for the steam explosion treated windmill palm fiber (SEWPF) surfaces, and (3) the cellulose fraction correspondingly increased with the decrease of the hemicelluloses and lignin contents. Finally, the SEWPFs were used to produce fiberboards, and the modulus of rupture (MOR), internal bond (IB), water absorption (WA) and thickness swell (TS) of the fiberboards were measured. The results showed that the WA and TS of the fiberboards made of SEWPF decreased 22 and 32%, respectively, in relation to those made of WPF, whereas the IB increased 46%. It is suggested that steam explosion can be a feasible approach to modify WPF and expand its uses.

The degumming effect on kenaf by different residence times of steam explosion treatment

Steam explosion (STEX) is an effective method of degumming kenaf and separating kenaf fibers. The residence time has a strong effect on the STEX process, and its mechanism of degumming kenaf was studied in this paper. In this research, five different residence times were chosen to treat kenaf at 1 MPa STEX pressure. The morphological changes were recorded using an optical camera and scanning electron microscopy (SEM). The chemical and physical properties of kenaf fiber were analyzed using wet chemistry analysis and a standard mechanical test. The cellulose content increased with increasing residence time. The breaking strength of kenaf fiber reached the highest level at 5 min residence time. It was also found that four different levels of kenaf fiber exist in the steam explosion process. This finding is very helpful for the degumming method development.

Isolating cellulose nanofibers from steam-explosion pretreated corncobs using mild mechanochemical treatments

Cellulose nanofibers (CNFs) with an average diameter 8 nm were isolated from corncobs using a stepwise method that included steam-explosion pretreatment, alkaline treatment, sodium hypochlorite bleaching, high-speed blending, and ultrasonic treatment. This mechanochemical method used only two chemical reagents in low concentrations to remove non-cellulosic components. The removal of non-cellulosic components was confirmed by Fourier-transform infrared spectroscopy. X-ray diffraction revealed an increase in crystallinity during steam explosion and subsequent mechanochemical treatments. Pretreatment by steam explosion caused the partial hydrolysis of hemicellulose and loosened the structure of raw materials, which facilitated the subsequent chemical processes. The thermal stability and morphology of samples at different stages were also investigated. Steam explosion increased the thermal stability of hemicellulose and cellulose components, as it removed a fraction of hemicellulose. High-speed blending reduced the entanglement of cellulosic fibers and created uniform size. Ultrasonic treatment was used in the final step of nanoscale fibrillation. The method used in this study is environmentally friendly and has the potential to be applied at industrial scale.

Integral methods of solving boundary-value problems of nonstationary heat conduction and their comparative analysis

The modern state of approximate integral methods used in applications, where the processes of heat conduction and heat and mass transfer are of first importance, is considered. Integral methods have found a wide utility in different fields of knowledge: problems of heat conduction with different heat-exchange conditions, simulation of thermal protection, Stefantype problems, microwave heating of a substance, problems on a boundary layer, simulation of a fluid flow in a channel, thermal explosion, laser and plasma treatment of materials, simulation of the formation and melting of ice, inverse heat problems, temperature and thermal definition of nanoparticles and nanoliquids, and others. Moreover, polynomial solutions are of interest because the determination of a temperature (concentration) field is an intermediate stage in the mathematical description of any other process. The following main methods were investigated on the basis of the error norms: the Tsoi and Postol’nik methods, the method of integral relations, the Gudman integral method of heat balance, the improved Volkov integral method, the matched integral method, the modified Hristov method, the Mayer integral method, the Kudinov method of additional boundary conditions, the Fedorov boundary method, the method of weighted temperature function, the integral method of boundary characteristics. It was established that the two last-mentioned methods are characterized by high convergence and frequently give solutions whose accuracy is not worse that the accuracy of numerical solutions.

Review of the pretreatment methods for wheat straw building materials

This paper reviews the pretreatment methods for wheat straw building materials and classifies the main methods according to their characteristics. The results indicate that the steam cooking and steam explosion treatment methods are relatively better than other methods and that particleboard and medium-density fiberboard manufactured using pretreated wheat straw possess correspondingly superior physical and mechanical properties. However, deficiencies in internal bonding, tensile strength, dimensional instability (swelling) and high moisture absorption remain. Thus, the present study proposes improving the pretreatment method and measurement and suggests a future development direction for the pretreatment of wheat straw building materials.

Glucose and Valuable Chemicals Production from Cotton Waste Using Hydrothermal Method

Direct hydrolysis of a towel to glucose was investigated using steam explosion and microwave-assisted treatment to find effective uses for cotton waste. The maximum glucose yield by direct hydrolysis (based on an untreated towel) was 18.8%, obtained at a steam pressure of 5.5 MPa (at 271 °C) and steaming time of 5 min using steam explosion. For the microwave-assisted treatment, with a 1.0 (w/w)% sulfuric acid catalyst, the maximum glucose yield by direct hydrolysis was 28.9%, obtained at a microwave heating temperature of 200 °C for 7 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 78.0%, attained at a microwave heating temperature of 200 °C for 7 min with 0.5 (w/w)% sulfuric acid catalyst. Furthermore, the maximum total glucose and valuable water soluble chemicals (cellobiose, 5-hydroxymethylfurfural, formic acid, and levulinic acid), 94.1%, were achieved at heating temperature of 200 °C for 10 min with 0.5 (w/w)% sulfuric acid catalyst. Finally, ethanol, 84.5% of conversion rate, could be produced using supernatant (it contained glucose) and microwave treated residue (200 °C for 7 min with 0.25 (w/w)% sulfuric acid catalyst) as carbon source for Saccharomyces cerevisiae with less fermentation inhibition.

Experimental and numerical study on bubble-sphere interaction near a rigid wall

This study is concerned with the interaction between a violently oscillating bubble and a movable sphere with comparable size near a rigid wall, which is an essential physical phenomenon in many applications such as cavitation, underwater explosion, ultrasonic cleaning, and biomedical treatment. Experiments are performed in a cubic water tank, and the underwater electric discharge technique (580 V DC) is employed to generate a bubble that is initiated between a rigid wall and a sphere in an axisymmetric configuration. The bubble-sphere interactions are captured using a high-speed camera operating at 52 000 frames/s. A classification of the bubble-sphere interaction is proposed, i.e., “weak,” “intermediate,” and “strong” interactions, identified with three distinct bubble shapes at the maximum volume moment. In the numerical simulations, the boundary integral method and the auxiliary function method are combined to establish a full coupling model that decouples the mutual dependence between the force and the sphere motion. The main features of bubble dynamics in different experiments are well reproduced by our numerical model. Meanwhile, the pressure and velocity fields are also provided for clarifying the associated mechanisms. The effects of two dimensionless standoff parameters, namely, γs (defined as ds/Rm, where ds is the minimum distance between the initial bubble center and the sphere surface and Rm is the maximum bubble radius) and γw (defined as dw/Rm, where dw is the distance between the initial bubble center and the rigid wall), are also discussed.

Characterization of cellulose nanofiber from steam-exploded Japanese cedar

Cellulose nanofiber (CNF) was produced from Japanese cedar using a new environmentally friendly pulping process, i.e. a steam explosion treatment followed by water and acetone extractions. The effect of the steam explosion treatment on the morphological, chemical, and mechanical properties of steam-exploded CNF were clarified. The increase of steam explosion severity markedly decreased the molecular weight of α-cellulose in the steam-exploded cedar pulp. The maximum tensile strength value of 88.9 MPa and Young’s modulus value of 12.9 GPa were obtained for the films made from steam-exploded CNF at a steam pressure of 35 atm for a steaming time of 5 min. The results obtained in this work were useful for developing a new production method of CNF from various steam-exploded woody biomass.