Moisture Distribution Changes and Wetwood Behavior in Subalpine Fir Wood during Drying Using High X-Ray Energy Industrial CT Scanner

In some species, such as subalpine fir (Abies lasiocarpa [Hook] Nutt), the water content of the confined zones in heartwood is as high as or greater than that of sapwood. Such wet zones of heartwood are referred to as “wetpocket” or “wetwood.” Wood products from subalpine fir forests are adversely affected by the wetwood-associated problems, particularly during the drying process. The objectives of the study were as follows: (1) to investigate feasibility of a high X-ray energy industrial computed tomography (ICT) scanner for imaging wetwood; and (2) to determine changes of the 2-D and 3-D moisture profiles (from core to shell) at different drying times.

Although medical CT scanning has been used for attaining signal intensity profiles of typical wood at different drying times, the technology has not, to date, been used for the study of wetwood phenomenon. This study presents, for the first time, results from the ICT imaging of the wetwood phenomenon. The results indicate that the ICT imaging system provides a powerful technique for imaging wetwood at different drying times. In addition, the results show that during the initial phase of drying, almost flat moisture profiles were observed in all wood types except for the wetwood, which showed a relatively higher moisture profile. A much slower (sluggish) drying development pattern at each increment from core to shell was found within the wetwood zone than normal wood regions along the width, thickness, and length of the board.     

Review of heat Conduction,Second Edition,S. Kakac and Y. Yener

In some species, such as subalpine fir (Abies lasiocarpa [Hook] Nutt), the water content of the confined zones in heartwood is as high as or greater than that of sapwood. Such wet zones of heartwood are referred to as “wetpocket” or “wetwood.” Wood products from subalpine fir forests are adversely affected by the wetwood-associated problems, particularly during the drying process. The objectives of the study were as follows: (1) to investigate feasibility of a high X-ray energy industrial computed tomography (ICT) scanner for imaging wetwood; and (2) to determine changes of the 2-D and 3-D moisture profiles (from core to shell) at different drying times.

Although medical CT scanning has been used for attaining signal intensity profiles of typical wood at different drying times, the technology has not, to date, been used for the study of wetwood phenomenon. This study presents, for the first time, results from the ICT imaging of the wetwood phenomenon. The results indicate that the ICT imaging system provides a powerful technique for imaging wetwood at different drying times. In addition, the results show that during the initial phase of drying, almost flat moisture profiles were observed in all wood types except for the wetwood, which showed a relatively higher moisture profile. A much slower (sluggish) drying development pattern at each increment from core to shell was found within the wetwood zone than normal wood regions along the width, thickness, and length of the board.     

Real-Time Moisture Content Measurement of Wood Under Radio-Frequency/Vacuum (RF/V) Drying

Hinoki timber was dried under radio-frequency at 6.7 kPa using two drying schedules, schedule A and schedule B. Moisture content (MC) was measured at 58 points in various locations of the timber using a new in-process monitoring concept. This concept uses the relationship between temperature, pressure, and equilibrium moisture content (EMC). Factors affecting the accuracy of MC measurement were also investigated in this study. The results showed that small wood pieces reached equilibrium at constant conditions within 1.5 h of the fiber saturation point (FSP) and that using the mean value of temperature and pressure within 30 min during radio-frequency/vacuum (RF/V) drying for MC measurement was an efficient method. The accuracy of moisture content measurement was the same for both drying schedules A and B. It can be concluded that air in wood was removed completely with drying schedule B and that below the FSP, pressure in the wood was maintained only by water vapor pressure during drying. It was possible to obtain accurate MC measurement. Above or near the FSP, MC cannot be measured using this method, whereas below the FSP, whatever the MC is, it can be measured practically anywhere in the timber.     

Interactions of Cold Radiofrequency Plasma with Solid Wood I. Nitrogen Permeability along the Grain

Exposure of 1.5 cm diameter × 1.2 cm long white fir and Douglas-fir heart-and sapwood samples to the action of cold radiofrequency oxygen, nitrogen, and helium plasmas strongly increased wood permeability to nitrogen flow along the grain. Oxygen was most effective, followed by nitrogen and helium. While an increase in radiofrequency energy level increased the effect, the opposite was true for an increase in reactant gas flow rate. With white fir the rate of permeability increase was higher at the beginning of the plasma treatment. This was attributed to differing ablation rates of cellulose, hemicelluloses, and lignin. No significant time difference in the rate of permeability increase was observed with Douglas-fir. Extractives suppressed the plasmainduced permeability increase; thus extraction with water and ethanol, followed by oxygen plasma treatment increased permeability of Douglas-fir heartwood 32 times, while plasma treatment of the unextracted Douglas-fir increased permeability only 8 times. The permeability of extracted and oxygen plasma-treated wood did not vary much across the grain, but did decrease with distance from the ends of the samples due to incomplete removal of extractives from the center.     

The impact of drying and steaming processes on surface color changes of tension and normal beech wood

Abstract

Beech wood has a high frequency of defects such as red heartwood, reaction wood (tension wood). For the experimental measurements four logs without visible defects like red heartwood, which can noticeably affects the measurements' results were qualified. The drying medium temperature in the first phase of the process before the moisture content of the specimens fell below the FSP was maintained at 45?°C. Then, the temperature was gradually increased to the maximum value 65?°C. The results showed that different initial wood moisture content does not affect to final value of tension and normal wood. The colorimetric parameter L* was much higher for tension wood. After steaming, there were greater differences in the colorimetric parameters, respectively, a* and b*. After drying the difference of all colorimetric parameters between tension and normal wood was significantly less. The color changes were only noticed in the surface layers of specimens. Differences were small, and thus, the impact of the tension wood on the color changes was not confirmed. However, since the lightness of tension wood plays a key role for its visual detection, it may be adequate to only measure the lightness parameter (L*).     

Brightness Improvement Of Douglas Fir Thermomechanical Pulp By Edta And Ascorbic Acid Treatments On Chips

This investigation studies the use of Douglas fir wood as feedstock for thermomechanical pulp (THP). Douglas fir wood extractives include flavonoids and other polyphenolic compounds, which make the pulp susceptible to discolouration. Pulp darkening is promoted by the formation of metal-chelates and phenolic oxidation products. The effectiveness of various wood pretreat- ments to prevent the discoloration of polyphenolic extractives in Douglas fir wood was investigated in lab-scale experiments. Iron- mediated brightness losses (up to 5.1% ISO) could be prevented by wood pretreatment with 0.2% EDTA. Treatment of wood meal slurries at temperature levels comparable to those applied in thermo- mechanical pulping caused wood discoloration due to polyphenol oxidation. The brightness losses could be reduced by the addition of 0.5% ascorbic acid. The anti-oxidizing agent was more effective with sapwood compared to heartwood. EDTA pretreatment allowed an increase in the proportion of heartwood from 12% to 39% (w/w) that could be tolerated as feedstock for the production of dithionite bleached TMP with a brightness of 60% ISO. Wood chip impregnation with both EDTA and ascorbic acid only proved advantageous over EDTA alone in Douglas fir samples consisting almost exclusively of sapwood.     

Effectiveness of impregnation of ammonium polyphosphate fire retardant in poplar wood using microwave heating

Poplar samples were impregnated with ammonium polyphosphate fire retardant at various pressures and durations after they were pretreated with microwave heating. The effects of the pressure and duration on the flame‐retardation and smoke‐suppression properties were investigated with cone calorimeter analysis. The peak heat release rate (pk‐HRR), total heat release (THR), and total smoke product (TSP) of treated woods were measured for samples of pretreated and untreated with microwave. After the impregnation, the poplar wood showed the significant improvement in its fire resistance. Compared with non‐impregnation wood, the pk‐HRR, THR, and TSP of wood impregnated with ammonium polyphosphate at pressure of 0.4 MPa and duration of 10 min were 48.29%, 35.58%, and 68.64% less, respectively. The pk‐HRR, THR, and TSP of microwave pretreated wood was 15.89%, 5.69%, and 13.59% less than those without microwave pretreated sample. The microwave pretreatment of wood can increase fire retardant effectiveness of ammonium polyphosphate‐impregnated wood. Copyright © 2015 John Wiley & Sons, Ltd.     

Mechanism for De-aspirating Pits in Subalpine Fir by Steam Explosion Prior to Drying

Subalpine fir with wet wood (wet pocket wood) is regarded as a species that is difficult to dry. Aspirated pits are one of the principal reasons to block water paths up in wood tracheids. Steam explosion is a technology to improve the dryability of subalpine fir by creating water paths in some aspirated pits.

In this study, green subalpine fir lumber was treated with steam explosion. Samples taken from the lumber before and after the treatment were observed with a scanning electron microscope (SEM). Amechanism for de-aspirating pits during the process of steam explosion was proposed based on the understanding of wood anatomy. A series of observations with the SEM verified the mechanism for de-aspiration. The observations also discovered that the fractures in the pits between ray parenchyma cells and earlywood tracheids occurred during the process of steam explosion.     

Low energy steam explosion treatment of plant biomass

The rational operational condition for maximizing the pretreatment effect on plant biomass while minimizing heat required was investigated. Eucalyptus globulus chips were used to evaluate the operational method for the most efficient conversion of plant biomass into useful materials by steam explosion. The energy consumption required to carry out the steam explosion was calculated by considering the mass balances of the water, the wood component, and the heat balance in the steam explosion apparatus. The energy consumption increased significantly with the increase of steam pressure and steaming time, and decreased rapidly with increase of the thickness of the heat‐insulating material in the steam explosion apparatus. The amount of methanol‐soluble lignin, a low molecular weight lignin, was measured experimentally under various operational conditions such as steam pressure and steaming time. The steam explosion at the steam pressure of 3.9 MPa and steaming time of 1.1 min was the most effective method for maximizing the delignification with low energy consumption. © 2001 Society of Chemical Industry     

Drying behavior and decay resistance of rubberwood from steamed log and presteamed lumber

The objective of this study was to evaluate the effect of log steaming and steaming prior to drying singly and both treatments together on the drying behavior and decay resistance of Hevea brasiliensis wood (rubberwood). Logs with a diameter of 34.6?±?4.4?cm were used. Half of the logs were kept in their original condition, and the other half were steamed at 90°C for 36?h. Later, the logs were cut into flat sawn boards. Half of the boards were kept in their original condition, and the other half were presteamed at 90°C for 3?h after 1?h of heating-up. These boards were dried in a drying kiln. The drying defects, drying time, drying rate, and decay resistance of wood to the Pycnoporus sanguineus fungus were determined. The results showed that the steaming is not suitable for decreases in the time and the drying rates of this kind of wood, and it neither reduces the drying defects of boards. Furthermore, these treatments adversely affected the decay resistance of rubberwood to P. sanguineus fungi.     

A Simulation of Wet Pocket Lumber Drying

In general, wood containing wet pockets is difficult to dry and to ensure uniformity of moisture content at the end of the drying process. Large variations of final moisture content and severe case hardening are common problems associated with the drying of wet wood. In order to devise optimal strategies for drying wood containing wet pockets, it is necessary to understand its complex moisture movement mechanisms and therefore predict drying times and final moisture content. Sub-alpine fir dimension lumber was used in this research because of its inherent issues related to wet pockets.

A two-dimensional mathematical drying model for wood containing wet pockets was developed. An effective diffusion coefficient (D_eff) was utilized in the model and heat and mass transfer equations were solved using a control volume approach. The difficulties involved in the simulation of the drying process of wet pocket lumber are due to the differences in moisture content and physical properties between wet and normal wood. Thus, an adjustable D_eff based on the moisture content (for both below and above fiber saturation point) was used during the simulation.

Four drying runs involving green unsorted sub-alpine fir lumber were carried out in a 3-ft laboratory kiln and in an 8-ft pilot kiln. The results of the simulations were in agreement with the results obtained through the drying experiments.     

Heat pretreatment of oilseeds: effect on oil quality

We studied the effect of seed conditioning via a rapid preheating technique to destroy the activity of oil-degrading enzymes. Rape and sunflower seeds were heated via steaming, oven cooking, infrared, and microwave. After the pretreatment the oil was expelled from the seeds by a screw press and its quality was determined via the analysis of oxidative stability, peroxide value, free fatty acid content, phosphorus, and iron. From the results it was concluded that preheating of the seeds leads to the expected decreased activity of lipase, but nevertheless increased levels of phosphorus and free fatty acids were observed. However, increased levels of phenolic antioxidants markedly improved the oxidative stability of rapeseed oil. From the techniques studied for heating of the seeds, microwave and steaming appeared to be the most suitable techniques. Both methods gave markedly improved oxidative stability, whereas steaming seemed to result in less formation of free fatty acids than microwave heating. Infrared heating led to rapidly burnt seeds and off-flavours.     

阻燃木材的力学性质初探

针对木材经含酸的阻燃剂处理后力学性能特别是弯曲强度及弯曲模量是否降低这一问题,以马尾松、米槠、檫树为研究对象,对比分析未处理材与汽蒸后以及阻燃处理后的三种木材的力学性质。研究表明,在试验范围内汽蒸预处理对木材的抗弯强度和弹性模量的影响与汽蒸压力与时间有关;米槠与马尾松经本阻燃体系处理后再低温干燥,力学性质得到增强,而檫树的力学性质则略为降低。     

The thermal conductivity of fir and beech wood heat treated at 170, 180, 190, 200, and 212°C

Heat treatment changes the chemical, physical, and mechanical properties of wood. The properties of heat‐treated wood have been researched considerably, but the thermal conductivity of heat‐treated wood in various conditions has not been reported. In this study, the thermal conductivity of heat‐treated fir and beech wood at temperatures 170, 180, 190, and 212°C for 2 h with ThermoWood method were investigated. The results were compared with industrially kiln‐dried reference samples. The results show that heat treatment caused an important reduction on thermal conductivity of wood, the extend of which is depend upon temperature and wood species. Considering all heat treating temperatures, generally by increasing heat treatment temperature the thermal conductivity of wood decreased. The effect of heat treating temperature on thermal conductivity was identical for fir and beech wood. The highest decrease in thermal conductivity occurred at 212°C for both wood species. When compared with untreated wood, the decreases in thermal conductivity at 170°C, and 212°C for fir and beech wood were 2%, 9 and 2%, 16% respectively. Depending on heat treatment temperature, the decrease found out beech in high temperature is higher than that of fir. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of rapeseed treatment by microwave and radio-frequency application on oil extraction and oil quality. Part I: Influence on mechanical oil extraction

The effect of a pretreatment of rapeseed with microwaves and radiofrequency energy on the oil yield and on the oil quality was investigated. Rapeseed samples were treated in an experimental microwave applicator and in an experimental radio-frequency applicator at different temperatures. Duration of treatment and the power applied were also varied. Afterwards the samples were pressed in a laboratory screw press and the exploitation rate was calculated. Results showed that pretreatment led to an obvious increase of the exploitation rate. The important parameters for this effect are temperature of pretreatment and power applied. Time of pretreatment is of lower importance. Further investigations also showed an influence of the pretreatment on quality parameters of the oil. These results are presented in the second part of this article “The Effect of Rapeseed Pretreatment by Microwave- and RF-application on Oil Extraction and Oil Quality — Part II. Influence on Oil Quality”.     

微波作用下木材苄基化改性研究

利用微波辐射对杉木进行苄基化改性,研究了各种因素对苄基化反应的影响,通过红外光谱分析(FT IR)对苄基化木材的分子结构进行表征。优化的反应条件是:无需甲苯溶剂,2克木粉用10mol/L的NaOH溶液16mL、氯化苄12mL于微波下辐射100min,辐射功率为前60min用650W的30%,后40min用650W的40%,可获得苄基化木粉,其增重率达到125%,效果与常规加热法基本相同,但在反应时间上却缩短了58%,而且微波法操作简便。     

爆破处理对赤桉板材干燥速度的影响

对赤桉板材在压力为0.8MPa,温度为95℃的条件下进行爆破预处理,并与未处理板材的干燥速度作对比研究。爆破处理后赤桉板材含水率有所下降,与未爆破的赤桉板材相比,渗透性和干燥速度有明显的提高。当含水率在50%～30%时,爆破处理过的赤桉板材和未爆破处理过的赤桉板材的含水率降低速度最快;当含水率在纤维饱和点以下时,爆破处理对赤桉板材干燥速度的改善效果不显著。同时在该试验压力下,赤桉板材的力学强度没有降低,说明爆破预处理没有影响赤桉板材的宏观结构,具有一定的可行性。     

The Effect of Heat Treatment on Some Mechanical Properties and Color Changes of Uludag Fir Wood

In this study, the effects of heat treatment on color, mass loss, compression strength, and hardness of Uludag fir (Abies bornmulleriana Mattf.) were investigated. Wood specimens conditioned at a relative humidity of 65% and a temperature of 20°C were subjected to heat treatment at 170, 190, and 210°C for 4, 8, and 12 h. After heat treatment, compression strength and hardness were determined according to TS 2595 and TS 2479. Color changes were determined according to DIN5033. The results showed that compression strength and hardness of Uludag fir wood decreased to varying extents in relation to intensity of treatment, whereas mass loss increased. We determined that treatment temperature had a more significant effect on color changes than did treatment time. The color of the wood became darker at the higher treatment temperatures.     

Fabrication of microwave absorbing CoFe2O4 coatings with robust superhydrophobicity on natural wood surfaces

A superhydrophobic wood surface with microwave absorption property was prepared based on the formation of CoFe₂O₄ nanoparticles and subsequent hydrophobization using fluorinated alkylsilane (FAS). Meanwhile, sticky epoxy resin was worked as a caking agent by adhering abundant of CoFe₂O₄ nanoparticles to wood surface. The as-prepared superhydrophobic coatings on wood maintain stable superhydrophobicity after suffering a significant abrasion. Moreover, the complex permeability and permittivity of the coated wood composites were measured in the frequency range of 2–18 GHz by vector network analysis. The microwave absorption properties were elucidated by the traditional coaxial line method. The results show that the as-prepared wood composites have excellent microwave absorption properties at the frequency of 16 GHz, and the minimum reflection loss can reach −12.3 dB. The approach presented may provide further routes for designing outdoor wood wave absorbers with a specified absorption frequency.     

A Simulation of Wet Pocket Lumber Drying

In general, wood containing wet pockets is difficult to dry and to ensure uniformity of moisture content at the end of the drying process. Large variations of final moisture content and severe case hardening are common problems associated with the drying of wet wood. In order to devise optimal strategies for drying wood containing wet pockets, it is necessary to understand its complex moisture movement mechanisms and therefore predict drying times and final moisture content. Sub-alpine fir dimension lumber was used in this research because of its inherent issues related to wet pockets.

A two-dimensional mathematical drying model for wood containing wet pockets was developed. An effective diffusion coefficient (D _eff ) was utilized in the model and heat and mass transfer equations were solved using a control volume approach. The difficulties involved in the simulation of the drying process of wet pocket lumber are due to the differences in moisture content and physical properties between wet and normal wood. Thus, an adjustable D _eff based on the moisture content (for both below and above fiber saturation point) was used during the simulation.

Four drying runs involving green unsorted sub-alpine fir lumber were carried out in a 3-ft laboratory kiln and in an 8-ft pilot kiln. The results of the simulations were in agreement with the results obtained through the drying experiments.