The Study on Bamboo Microfibers Isolated by Steam Explosion and Their Comprehensive Properties

To overcome the shortage of wood resources as well as to develop novel natural fibers materials,the Chimonobambusa quadrangularis(CQ)and Qiongzhuea tumidinoda(QT)planted in Southwest China were effectively isolated by the steam explosion(SE).The fine and uniform bamboo microfibers derived from CQ and QT were obtained,and their smallest average widths were 12.62μm and 16.05μm,respectively.The effects of steam explosion on the micro-morphology,chemical composition,thermal stability,crystallinity,surface wettability,and mechanical properties of bamboo microfibers were comprehensively investigated.The results showed that the relative content of cellulose in bamboo microfibers increased but the hemicellulose and lignin contents decreased after SE.The degrees of crystallinity for CQ and QT increased from 40.49%and 39.46%to 68.90%and 55.78%,respectively.The thermal stability and surface hydrophilicity were also improved.The CQ microfibers had a maximum decomposition temperature of 2.79°C,a tensile strength of 58.54 MPa,an elongation at break of 0.6%,and a water contact angle of 2.7°higher than those of the QT microfibers.

Optimization of Steam Explosion Process Condition for Extracting Polysaccharides from Pseudostellaria heterophylla by Response Surface Methodology

【Objective】To optimize the steam explosion process condition for extracting polysaccharides from Pseudostellaria heterophylla.【Method】The effects of steam pressure,pressure-maintaining time and material moisture content on the extraction of polysaccharides from Pseudostellaria heterophylla were studied by response surface methodology based on Box-Behnken design.【Result】The findings showed that each factor could significantly affect the test index,and the optimum condition was as follows:steam pressure 1.50 Mpa,pressuremaintaining time 46 s and material moisture content 46%.Under this condition,the verified experimental value of polysaccharides from Pseudostellaria heterophylla was 39.32%,indicating a relative standard deviation of 2.73%from the predictive value.Meanwhile,scanning electron microcopy(SEM)images showed that the surface physical structure of Pseudostellaria heterophylla was irregularly broken and cracked,which means the physical structure of Pseudostellaria heterophylla was changed and destroyed at the cellular level.【Conclusion】This experiment provides a new approach for the extraction of polysaccharides from Pseudostellaria heterophylla,as well as a reference for the resource utilization of Pseudostellaria heterophylla.

Effect of Steam Explosion Technology Main Parameters on Moso Bamboo and Poplar Fiber

One of the large-scale industrial applications of Moso bamboo and poplar in China is the production of standardized fiberboard.When making fiberboard,a steam blasting pretreatment without the addition of traditional adhesives has become increasingly popular because of its environmental friendliness and wide applicability.In this study,the steam explosion pretreatment of Moso bamboo and poplar was conducted.The steam explosion pressure and holding time were varied to determine the influence of these factors on fiber quality by investigating the morphology of the fiber,the mass ratio of the unexploded specimen at the end face,the chemical composition,and the tensile strength.The following conclusions were drawn:As the steam burst pressure and holding time increased,more cellulose and hemicellulose degradation occurred(the degradation of hemicellulose was greater than that of cellulose),the lignin content rose,and the fiber bundle strength decreased.The degradation of bamboo cellulose was slightly higher than that of poplar,and the degradation of poplar hemicellulose was significantly faster than that of bamboo.Furthermore,increasing the steam explosion pressure and pressure holding time could not effectively increase the lignin content.It is recommended to use a steam blasting pressure of 2.5 MPa or 3.0 MPa and a holding time of 180 s to perform steam blasting on bamboo and poplar specimens.

Pretreatment of Corn Stalk by Steam Explosion

A steam explosion pretreatment, which is one of the best ways of pretreating plant stalk, is applied at various severities to corn stalk. It could effectively modify the super-molecular structure of corn stalk and defibrating corn stalk into individual components. The relationship between yield of reducing sugar and the operating conditions, including temperature, pressure of steam explosion pretreatment and acidity, is also established. Experimental results prove that the steam explosion substantially increases the yield of reducing sugar, and the optimal condition for steam explosion is as follows: the pressure is 2.0 MPa, the pressure-retaining time 300 s, the initial acid concentration 1% and the acid treatment time 24 h.

Evaluation and Improvement of Antioxidant Activity of Water-soluble Lignin Products from Steam Explosion Processing of Corn Stalk

In this study,corn stalk was pretreated by steam explosion under various processing conditions,and the antioxidant activity of hydrolysates in the post-process washing liquor was analyzed using the 1,1'-diphenyl-2-picrylhydrazyl(DPPH•)scavenging method.The yield and composition of the hydrolysates obtained under different treatment conditions were also determined;the results indicated that the steam explosion extent had a significant effect on both properties.Under optimized conditions(1.5 MPa,20 min),the obtained hydrolysate had the highest phenolic compound yield(18.6 mg/g untreated corn stalk)and the highest radical scavenging capacity(IC_(50)=0.24 mg/mL).To confirm the positive effect of phenolic compounds on the antioxidant activity of the hydrolysate,one-step ethanol fractionation was carried out.Due to the enrichment of phenolic compounds,the ethanolsoluble fraction(ESF)exhibited significantly enhanced antioxidant activity with an IC_(50) value of 0.06 mg/mL,which was close to that of butylated hydroxytoluene(BHT,IC_(50)=0.056 mg/mL).Consequently,this work indicated that phenolic compounds have a significant effect on the antioxidant activity of hydrolysate from steam-exploded corn stalk and that simple one-step ethanol fractionation is an effective way to enrich the phenolic compounds in the hydrolysate and improve the antioxidant activity.

Status of the OECD-SERENA Project for the Resolution of Ex-vessel Steam Explosion Risks

OECD/NEA （Organization for Economic Cooperation and Development/Nuclear Energy Agency） launched the SERENA （steam explosion resolution for nuclear application） project to resolve internationally the ex-vessel steam explosion issue, which is one of major unresolved issues after a TMI-2 （three mile island-2） accident. One of main conclusions of OECD/NEA SERENA Phase 1, which was completed in 2005, was that some damage to the cavity is to be expected for an ex-vessel explosion. One major uncertainty that does not allow for a convergence toward consistent predictions was that there are no data on the component distribution in a pre-mixture at the time of an explosion, especially the level of the void. The other major uncertainty is the explosion behavior of corium melts. Therefore, SERENA Phase 2 was launched on October 1, 2007 to resolve the uncertainties of the coolant void and material effect by performing a limited number of well-designed tests with advanced instrumentation reflecting a large spectrum of ex-vessel melt compositions and conditions, and the required analytical work to bring the code capabilities to a sufficient level for use in reactor case analyses. The recent status of the OECD-SERENA Phase 2 project for the resolution of ex-vessel steam explosion risks will be described.

Lignocellulosic Micro and Nanofibrillated Cellulose Produced by Steam Explosion for Wood Adhesive Formulations

The reinforcing impact of Lignocellulosic micro and nanofibrillated cellulose(L-MNFCs)obtained from Eucalyp-tus Globulus bark in Urea-Formaldehyde UF adhesive was tested.L-MNFCs were prepared by an environmentally friendly,low-cost process using a combination process involving steam explosion followed by refining and ultra-fine grinding.Obtained L-MNFCs showed a web-like morphology with some aggregates and lignin nanodroplets.They present a mixture of residual fibers and fine elements with a width varying between 5 nm to 20μm,respec-tively.The effects of the addition of low amounts of L-MNFCs(1%wt.)on the properties of three different adhe-sives(Urea-Formaldehyde UF,Phenol-Formaldehyde PF,and Tannin-Hexamine TH)were studied by the evolution of the pH,the viscosity,and the mechanical properties.Results showed that the viscosity of PF and UF adhesives increased with the addition of L-MNFCs,unlike TH.Meanwhile,the addition led to better mechan-ical behavior for the three adhesives.Particleboards were then prepared using modified UF with L-MNFCs and tested.Results showed that an amount of 1%wt.of L-MNFCs was sufficient to increase the internal bonding by≈67%,the modulus of elasticity by≈43%,and the modulus of rupture by≈29%.

Use of Waste Vegetable Biomasses Treated by Steam Explosion for the Horticultural Crop Protection

The purpose of this study was to assess the suppressive effect of Waste Vegetable Biomasses （WVBs） treated by the Steam Explosion technique in a continuous plant, against soil-borne plant pathogens. In order to assess their disease suppression, five WVBs （Miscanthus biomass, durum wheat straw, rice straw, corn stalk and wood shaving） and commercial compost were tested in vivo at three different doses （10, 20 and 30% of potting mix） on seven horticultural pathosystems plant/fungus： tomato/Phytophthora nicotianae, cucumber/Pythium ultimum, lettuce/Fusariurn oxysporum f. sp. lactucae, melordFusariurn oxysporum f. sp. melonis, bearffRhizoctonia solani, eggplant/Verticillium dahlie and fennel/Sclerotinia sclerotiorum. The results showed that the corn stalk was more efficient respect to Miscanthus, compost, wheat straw, rice straw and wood shaving in all the patbosystems and at all the doses tested. The corn stalk suppression ranged from 97% in eggplant/F, dahliae to 35% in lettuce/F, oxysporum f. sp. lactucae, and it was significantly higher with respect to the other substrates. In general, the wheat straw, rice straw and wood shaving were statistically found less efficient as suppressive substrate with respect to corn stalk, Miscanthus and compost at the 30% dose in four pathosystems In particular, the wood shaving suppressiveness ranged from 48% in eggplant/V, dahliae to 12% in lettuce/F, oxysporum f. sp. lactucae. The different suppressiveness observed could be attributed to different concentration of the microbial inhibitory substances （furfurals, organic acids and lignosulfonates） produced during the processing of fresh biomass.

Corncobs as Substrate for Oleaginous Yeast-Pretreatment via Steam Explosion and Hydrolysis

Corn cobs are a promising lignocellulosic substrate for the production of biofuels like bioethanol via conventional yeast or biodiesel via oleaginous yeast. Pretreatment of the substrate is essential for further hydrolysis and fermentation steps. This study focused on the steam explosion method as pretreatment. Therefore, different steam explosion severities were evaluated. The content of glucan, xylan and Klason lignin was examined. Xylan degraded with increasing severity from 412.7 g·kg-1 （untreated） to a minimum of 127.3 g-kg1 dry matter （190 ℃/30 min）. Glucan concentrations increased from 315.1 g·kg1 （untreated） to a maximum of 371.6 g·kg-1 dry matter （200 ℃/20 min）. For soluble lignin, an increase could be observed at rising severity, from 145.3 g·kg-l （untreated） to a maximum of 214.9 g·kg-1 dry matter （190 ℃/30 min）. Furthermore, the mass recovery was calculated. At harsher pretreatment conditions, a significant mass loss was observed, estimated by the ash content in the recovered dry matter. The lowest recovery rate was observed for SF = 4.13 （190 ℃/30 min） with 68.39%. The produced inhibitors were evaluated.

Effects of Rice Straw Steam-explosion Spent Liquor on the Growth of Cabbage Seedlings

The direct use of spent liquor from pulping and papermaking engineering,which is abundant in active organic matter,can avoid resource wastage and environmental pollution.In this study,the effects of soaking solution and filtrate from steam-exploded rice straw on seed germination and the early development of cabbage were investigated.The results have shown that soaking solution and filtrate stimulated early cabbage growth at low concentrations.Optimal germination potential and the rate of soaking solution-treated cabbage seeds increased by 8%and 5%,respectively;meanwhile,that of the filtrate-treated cabbage seeds increased by 11%and 5%,respectively.Promotion of root growth by steam-exploded rice straw spent liquor was expressed in lateral root multiplication.The fresh weight of cabbage seedlings treated with the soaking solution/filtrate increased by more than 50%and the dry weight over 20%.Comparatively,the stimulation of filtrate on seed germination and early development of cabbage is superior to that of the soaking solution.Steam-exploded rice straw spent liquor is rich in bioactive lignin and oligosaccharides,which makes it a promising biostimulant for promoting crop growth.

Pelleting characteristics of selected biomass with and without steam explosion pretreatment

Processing and densification of agricultural biomass into high density and durable pellets are critical to facilitate handling,storage and transportation.Biomass pelleting experiments were designed to conduct single and pilot scale pelleting of non-treated and steam exploded barley,canola,oat and wheat straw grinds acquired from 6.4,3.2,1.6 and 0.8 mm hammer mill screen sizes at 10%moisture content(wb).Single-pelleting was performed by applying compression pressures of 31.6,63.2,94.7,and 138.9 MPa using a close-fit plunger die assembly(die length 135.3 mm and diameter of(6.30±0.5)mm).During pilot scale pelleting,customization of ground straw material was performed by adding steam exploded biomass in increments of 25%to non-treated ground straw for respective biomass at specific grind size.Ground straw samples were conditioned to 17.5%moisture content and 10%flaxseed oil was added to increase the bulk density and flowability of grinds,which resulted in the production of pellets.The quality of pellets from single pelleting experiments was ascertained by measuring their respective density and durability.In addition,the change in pellet density was measured after a storage period of one month to determine its dimensional stability.It was determined that applied pressure and pre-treatment were significant factors affecting the pellet density.Also,bigger grind sizes and lower applied pressures resulted in higher pellet relaxations(lower pellet densities)during storage of pellets.The pilot scale pellet mill produced pellets from ground non-treated straw at hammer mill screen sizes of 0.8 and 1.6 mm and customized samples having 25%steam exploded straw at 0.8 mm.It was observed that the pellet bulk density and particle density are positively correlated.The density and durability of agricultural straw pellets significantly increased with decrease in hammer mill screen size from 1.6 mm to 0.8 mm.Customization of agricultural straw by adding 25%of steam exploded straw by weight is possible,but it did not improve pellet quality.In addition,durability of pellets was negatively correlated to pellet mill throughput and was positively correlated to specific energy consumption.

Producing durable pellets from barley straw subjected to radio frequency-alkaline and steam explosion pretreatments

Pelletization,a form of densification,increases bulk density and improves the convenience and accessibility of biomass feedstock due to the uniform shape and size.Pretreatment of biomass enhances the breakdown and accessibility of the cross-linking lignin,which acts as a binding agent.In this study,pelletization of radio frequency-alkaline and steam explosion pretreated barley straw was performed.Three levels of temperature(70oC,80oC,and 90oC),five levels of the mass ratio of biomass to NaOH solution(1:4,1:5,1:6,1:7,and 1:8),one hour equilibration time,biomass screen size of 1.6 mm,1%NaOH concentration,and 20 min residence time in the radio frequency chamber were used for the radio frequency-alkaline pretreatment.Three levels of steam temperature(140oC,160oC,and 180oC),three levels of moisture content of 8%,30%,and 50%(mass fraction of total mass),and 5 min and 10 min exposure to steam were tested for the steam explosion pretreatment.The effects of both pretreatment methods were evaluated by pelletizing the pretreated and non-pretreated barley straw samples in a single pelleting unit.The pellet density,tensile strength,durability,dimensional stability,and color of the pellets were determined.Radio frequency-alkaline pretreatment with the use of 1%NaOH solution and a ratio of biomass:NaOH solution of 1:8 has significant effect(P<0.05)on the breakdown of the lignified matrix,resulting in pellets with superior physical characteristics.The steam exploded samples pretreated at higher temperatures(180ºC)and retention time of 10 min resulted into pellets with good physical qualities.

Structure, composition and enzymatic hydrolysis of steam-exploded lespedeza stalks

Pretreatment of lespedeza stalks by steam explosion has been studied. The results indicate that steam-exploded pretreatment has strong effects on physical features, morphology, crystallinity, and composition of lespedeza stalks as shown by scanning electron microscopy （SEM）, infrared （IR）, and X-ray diffraction spectrometry methods. After steam explosion, the cellulose and lignin contents of lespedeza stalks varied only slightly, but the hemicellulose content had decreased from 29.34% to 7.48%. The cellulose obtained by steam-exploded pretreatment had a higher degree of crystallinity than that of the raw material. At the explosion condition of 2.25 MPa and 4 min, lignocellulose is easier to hydrolyze by enzyme than the original lignocellulose. The concentration of reduced sugar in the hydrolyzate liquid increased from 71.77 to 162.84 g·L^-1.

Simultaneous saccharification and fermentation of steam-pretreated lespedeza stalks for the production of ethanol

Lespedeza stalks were subjected to steam pretreatment at 210℃ for some steaming time before simultaneous saccharification and fermentation （SSF）. Cellulose-derived glucose was extensively utilized by yeast during SSE The ethanol yields after steam pretreatment of the lespedeza stalks at 210℃ were 59.3%, 72.8% and 62.2% of the theoretically expected values when the steaming times were 2, 4 and 6 min, respectively. The highest yield from α-cellulose was 92.7% of the theoretical value. Steam explosion pretreatment of lespedeza stalks increased ethanol yields by a factor of 4.4, from 16.4% （untreated） to 72.8% （steam explosion pretreated）.

Steam Exploded Peanut Shell Fiber as the Filler in the Rigid Polyurethane Foams

In this study,steam exploded peanut shell fibers(SE-PSFs)were utilized to fabricate with rigid polyurethane foam(RPUF)in order to improve sound absorption performance and hydrothermal weather resistance.Optimized method of SE treatment,RPUF preparation and flame retardant treatment were selected to prepare SE-PSF/RPUF composites in this experiment.Physical and mechanical properties including density,water absorption capacity,thickness swelling rate,compressive strength,thermal conductivity and average sound absorption coefficient of SE-PSF/RPUF were investigated and compared with the control(PRUF).The results showed that the density,water absorption capacity,thickness swelling rate and thermal conductivity showed an increasing trend with the increase of SE-PSFs content.The strength of the composite material showed a downward trend with the increase of the SE-PSFs content.The average sound absorption coefficient of the SE-PSFs/RPUF compared with PRUF significant increased,and the average sound absorption coefficient of the SE-PSFs/RPUF with SE-PSFs 40%was 0.47.The study getted the best ratio of flame retardants for 10%EG and 3%DMMP.The oxygen index was 35.56 vol%.

Effect of steam-pretreatment combined with hydrogen peroxide on lignocellulosic agricultural wastes for bioethanol production：Analysis of derived sugars and other by-products

The hydrogen peroxide, a green impregnating agent suitable for lignocellulosic biomass to bioethanol process, was used to pretreat sugarcane bagasse by steam explosion. Two different concentrations of hydrogen peroxide（0.2% and 1%） were investigated. Then, the biomass was hydrolyzed after pretreatment using cellulase. The amount released of：（i） cellobiose;（ii） monosaccharides, as glucose, xylose, arabinose and mannose and（iii） lignocellulose derived by-products, as furans and small organic acids（acetic, formic,and levulinic acid）, was evaluated in the hydrolysate samples, previously pretreated both in the presence and absence of impregnating agent. By adding of hydrogen peroxide in steam-pretreatment, the average yield increase was 12% for glucose and as high as 34% for xylose, and cellobiose yield was decreased of about 30%. No significant increase has been observed in arabinose and mannose yield. Furthermore,the hydrogen peroxide seems not increased the formation of lignocellulose derived by-products during pretreatment process, with the exception of the levulinic acid.

Study of the Effect of Different Solids Load on the Optimum pH during Enzymatic Hydrolysis of Steam Exploded Corn Stover

The understanding of enzymatic saccharification of pretreated lignocellulosic material is of great importance. There are several important commercially available enzymes in the market that are used for this purpose. The conditions of pH and temperature performance of any particular enzyme are very well defined and it is clearly indicated by its manufacturer and it depends on the type of enzyme or enzymes in the complex pool. It is well know that commercial cellulases work best at pH around 4.8-5.0 and as a consequence this is widely used in the industry and the literature. In this study it was found that optimum pH of cellulases is different than that recommended by its manufacturer at higher solids load saccharification. The optimum pH changes depending on the consistency or solids loads of the matrix where the enzyme is acting upon. Steam exploded corn stover was tested with cellulases and xylanases at different pH, consistencies and ionic strength. Results showed that the optimum pH at lower consistency （1% w/w） is the same as the one recommended by the manufacturer and in the literature; however at higher consistency the value obtained was higher （pH 5.5 to pH 6.5） instead ofpH 4.8. The difference could represent up to 30-50% higher yields and hence of great importance for the economics of second generation fuel production. An explanation of this behavior could be associated with the Donnan effect theory. This effect indicates that the presence of charged groups in the fiber matrix creates a pH gradient within the slurry. If the charged groups are negatively charged this would create a local or internal pH lower than the surrounding liquid pH. This could explain why by reducing the concentration of H^＋ higher enzymatic conversion yields were observed.

Synthesis and Characterization of a Novel Cellulose Nonionic Ether

A kind of novel cellulose ether-trihydroxybutyl cellulose (THBC) was synthesized. The process includes the steam explosion treatment of cotton cellulose, alkalization, etherification and purification. Sweep electron microscope (SEM), Fourier transform infrared (FTIR) and X-ray diffraction were used to characterize the cellulose pretreated and the product. The effects of reaction conditions (temperature, time) on the molecular substitution (S_m) were discussed. To obtain a higher degree of molecular substitution, the reaction temperature is 80 ℃, and the reaction time is 4 h.

Experimental Investigation on Fuel Coolant Interaction Using Simulant Ceramic Melts in Water: Insights and Conclusions

Steam explosion is one of the crucial and poorly understood phenomena which may occur during severe accident scenario and may lead to containment failure. In spite of several experimental and analytical studies, the root cause of steam explosion has not been understood. Recent claims in the literature suggest that the presence of fine fragmentation during steam explosion causes its occurrence. In order to investigate this and understand the root cause of steam explosion, series of experiments were performed with 50 g to 2500 g of CaO-B2O3, a corium simulant in 4.5 litre of water. It was observed that steam explosion may occur even in the absence of fine fragments, which is contrary to the claims in the literature. To investigate further, conversion efficiency analysis was performed. This suggested that the amount of thermal energy converted to mechanical energy is more important deciding factor in explaining the occurrence of steam explosion. The present study discusses the importance of conversion efficiency in deciding steam explosion and also gives a new perspective to look at steam explosion phenomenology.

Pilot-scale acetone-butanol-ethanol fermentation from corn stover

Biobutanol is an advanced biofuel that can be produced from excess lignocellulose via acetone-butanol-ethanol(ABE)fermentation.Although significant technological progress has been made in this field,attempts at largescale lignocellulosic ABE production remain scarce.In this study,1m^(3)scale ABE fermentation was investigated using high inhibitor tolerance Clostridium acetobutylicum ABE-P1201 and steam-exploded corn stover hydrolysate(SECSH).Before expanding the fermentation scale,the detoxification process for SECSH was simplified by process engineering.Results revealed that appropriate pH management during the fed-batch cultivation could largely decrease the inhibition of the toxic components in undetoxified SECSH to the solventogenesis phase of the ABE-P1201 strains,avoiding“acid crash”.Therefore,after naturalizing the pH by Ca(OH)_(2),the undetoxified SECSH,without removal of the solid components,reached 17.68±1.30 g/L of ABE production with 0.34±0.01 g/g of yield in 1 L scale bioreactor.Based on this strategy,the fermentation scale gradually expanded from laboratory-scale apparatus to pilot-scale bioreactors.Finally,17.05±1.20 g/L of ABE titer and 0.32±0.01 g/g of ABE yield were realized in 1m3 bioreactor,corresponding to approximately 145 kg of ABE production from 1 t of dry corn stover.The pilot-scale ABE fermentation demonstrated excellent stability during repeated operations.This study provided a simplified ABE fermentation strategy and verified the feasibility of the pilot process,providing tremendous significance and a solid foundation for the future industrialization of second-generation ABE plants.