Welding wood achieves joints whose strength is comparable with the strength of glued joints. When welding, the top of the dowel is not welded because of the lack of melted lignin. To achieve ...satisfactory strength of a welded joint, it is necessary to optimize the main welding factors such as interference fit, frequency of dowel rotation, welding depth, welding duration, etc. There are also other ideas to increase the strength of welded joints. One of these ideas involves pre-treatment of dowels with wood decaying fungi to increase the proportion of lignin on the surface of the dowels and thus in the melt. This paper presents the results of the impact of pretreatment of beech wood dowels with the brown-rot fungus Gloeophyllum trabeum. Results showed that biological pretreatment of the dowels had a significant impact on the pull-out force of the joint. Pretreatment for 4 weeks caused a substantial increase in pull-out force, while pretreatment for 2 weeks did not have a positive effect on the strength of the welded joint. Grooved dowels exhibited an increase in pull-out force of 26.9%, while smooth dowels had an increase of 21.1% of pull-out force. Research also determined additional vibrations during welding.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The increasing use of wood leads to the need for a better understanding of its thermal properties with the aim of quantitatively identifying the exchange of thermal energy between wood and the ...surrounding solar radiation as precisely as possible. Reliable and rapid measurement of thermal conductivity is one of the most important current industrial requirements. The aim of this study is to examine the validity of using the modified transient plane source method (MTPS), which uses the principle of one-sided heating of the sample, and is defined by the ASTM D7984-21 (2021) standard, for determining the thermal conductivity of complex biocomposite composite materials such as wood. The analysis of the available literature shows a lack of data on the thermal conductivity of the type of wood originating in Croatia. In this study, the thermal conductivities of beech and fir wood samples in the longitudinal direction was determined by the MTPS method depending on the temperature and moisture content in the samples. Measurements were made on samples with a moisture content of 0%, 10%, and 20% in the temperature range from 20 to 80 °C.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The research was conducted with the goal to determine the variability of the quality parameters of the wood chips produced from the most favorable raw material (energy roundwood), and in the most ...controllable operational conditions (pellet factory), as the first step in identifying opportunities to optimize the wood chips’ quality monitoring. Four raw material types were tested: fir/spruce and beech debarked energy roundwood, as well as energy wood with bark of the same species. Sampling was conducted during six consecutive months along with laboratory testing, all according to the HRN EN ISO standards for solid biofuels. Interpretation of the results was done in relation to deviation from the first sampling results (as an indicator of the possibility to retain the quality of wood chips), and repeatability and reproducibility set in the standards (as an indicator of acceptable variability). The influence of the species and debarking process on the wood chips’ quality was analyzed as well. Relative deviation from the first sampling as well as the quality class change pointed moisture content as a normative property with the lowest possibility to retain initial values over the six-month period. Ash content results indicated a strong possibility to maintain the initial ash content class in the majority of the samples. In just three cases, the results of ash content were outside the reproducibility limits with first sampling as a reference. Gross calorific value results pointed only four samples outside the reproducibility limits with the first sampling results are set as a reference. Wood species influenced gross calorific value and the median value of the particle size distribution and debarking showed a significant positive effect on the moisture content reduction as well as on the ash content reduction. Presented findings are indicative for the investigated raw materials, however for the general conclusion on the subject of wood chips normative properties variation, various raw material types will have to be examined in further research.
Biomass Pelletizing Process Dujmović, Marin; Šafran, Branimir; Jug, Matija ...
Drvna industrija,
03/2022, Letnik:
73, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A review paper was designed as a lab-scale start-up guideline for general pelletizing process and technologies for biomass feedstock. The main body consists of summarized published research on the ...topic of all main parts of the biomass pelletizing process and technology, including machinery and their parts, optimal feedstock conditions as well as pellet forming processes and principles. This paper is more focused on the specific parameters necessary to obtain optimal pelletizing process that results in desired pellet quality, and less on feedstock preparation, final product post-treatment (e.g. cooling), handling (storage, transportation) or exact quality specifications. A summary of the suggested feedstock, technological and other parameters for the purpose of easier lab-scale start-up of biomass pellets production, which is based on the cited literature throughout this paper, is given in the last section.
Pregledni rad pripremljen je kao laboratorijski priručni materijal za osnovne procese i tehnologije peletiranja biomase. U njemu su sistematizirane spoznaje iz dostupnih izvora literature o temi glavnih dijelova procesa i tehnologije peletiranja biomase, uključujući strojeve i njihove pripadajuće dijelove, optimalne ulazne parametre sirovine, kao i načela i procese izrade peleta. Ovaj je priručni materijal više usmjeren na specifične parametre nužne za optimalan proces peletiranja radi dobivanja peleta željene kvalitete, a manje na pripremu sirovine, tretiranje proizvedenog peleta (npr. hlađenje), rukovanje peletima (skladištenje, transport) ili na određena kvalitativna svojstva peleta. Sažetak preporučenih tehnoloških parametara i ulaznih parametara sirovine, koji se temelji na informacijama iz navedene i citirane literature, nalazi se na kraju ovoga preglednog rada.
The paper presents the research results of process characteristics during cutting beech prisms on horizontal log band saw type Mebor HTZ–1000. The band saw blades were equipped with swaged teeth and ...stellited teeth. The power consumption, tool wear resistance, surface roughness and variation of board thickness during 6000 m sawn prism length were studied. All studied parameters were monitored during the tool life-circle (from sharpening to loosing its sawing capability). Wearing process was monitored as a function of cutting length. The cutting edge modifi cation, i.e. its wearing affecting energetic demands during sawing process as well as the surface quality and dimension accuracy of produced work piece was monitored, too. Based on cutting edge wear process and its effect on the above mentioned sawing process parameters, the optimal period of saw band replacement with a new or sharpened one was determined. Based on measured parameters, it was possible to determine which type of band saw tooth is recommended for cutting frozen beech.
The article presents preliminary results of the biological durability of oil heat treated (OHT) alder wood (Alnus glutinosa) against pure cultures of rot fungi (Postia placenta and Trametes ...versicolor) in lab conditions. The modification was performed by heating of specimens immersed in soya oil. There were four heating regimes of different duration (6 and 10 hours) at final temperature of 180 and 200 ºC. The increase in mass (MI) caused by modification and mass loss of wood caused by fungal decay (ML) were determined. In addition, the natural durability of alder wood was determined and compared to the natural durability of beech wood as the reference wood species. After modification of alder wood at 200 °C, MI was lower than after treatment at 180 °C. MI was also lower after 10 hours of treatment than after 6 hours of treatment. The results showed significantly increased biological durability of modified alder wood against both tested fungi. The effect of OHT on increasing the biological durability of alder wood was higher against the fungus P. placenta. It seems that the fungus T. versicolor favours the remained oil after modification causing higher mass loss. The results showed that alder wood, thermally modified in soya oil by testing regimens, is not suitable for applications in use classes 3-5.
Welding wood achieves joints whose strength is comparable with the strength of glued joints. When welding, the top of the dowel is not welded because of the lack of melted lignin. To achieve ...satisfactory strength of a welded joint, it is necessary to optimize the main welding factors such as interference fit, frequency of dowel rotation, welding depth, welding duration, etc. There are also other ideas to increase the strength of welded joints. One of these ideas involves pre-treatment of dowels with wood decaying fungi to increase the proportion of lignin on the surface of the dowels and thus in the melt. This paper presents the results of the impact of pretreatment of beech wood dowels with the brown-rot fungus Gloeophyllum trabeum. Results showed that biological pretreatment of the dowels had a significant impact on the pull-out force of the joint. Pretreatment for 4 weeks caused a substantial increase in pull-out force, while pretreatment for 2 weeks did not have a positive effect on the strength of the welded joint. Grooved dowels exhibited an increase in pull-out force of 26.9%, while smooth dowels had an increase of 21.1% of pull-out force. Research also determined additional vibrations during welding.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Because of its hardness, wear-resistance, strength, and bending capabilities, beech wood is a widely-used hardwood in Europe. It is mainly used for furniture, floors, construction, veneer boards, and ...laminated wood. For such uses, the mechanical properties are very important, especially in cases of impact loads. The aim of this work is to analyse the mechanical properties of beech wood samples exposed to compressive force in the longitudinal direction based on different loading rates (in the range from 10 mm/min to 500 mm/min). Stress–strain diagrams were made with the experimental data, and mathematical functions were fit to them. Using the fit functions, the following properties of beech wood samples were determined: the stress and strain at the elastic limit; the maximum stress and associated strain; the modulus of elasticity; the tangent modulus; the specific energy of elastic strain; and the specific energy of plastic strain. The results showed that by increasing the loading rates, the elastic properties of beech wood increase, while the analysed plastic properties do not show a clear tendency of changes with increase of the loading rates.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Pregledni rad pripremljen je kao laboratorijski priručni materijal za osnovne procese i tehnologije peletiranja biomase. U njemu su sistematizirane spoznaje iz dostupnih izvora literature o temi ...glavnih dijelova procesa i tehnologije peletiranja biomase, uključujući strojeve i njihove pripadajuće dijelove, optimalne ulazne parametre sirovine, kao i načela i procese izrade peleta. Ovaj je priručni materijal više usmjeren na specifične parametre nužne za optimalan proces peletiranja radi dobivanja peleta željene kvalitete, a manje na pripremu sirovine, tretiranje proizvedenog peleta (npr. hlađenje), rukovanje peletima (skladištenje, transport) ili na određena kvalitativna svojstva peleta. Sažetak preporučenih tehnoloških parametara i ulaznih parametara sirovine, koji se temelji na informacijama iz navedene i citirane literature, nalazi se na kraju ovoga preglednog rada.
The increasing use of wood leads to the need for a better understanding of its thermal properties with the aim of quantitatively identifying the exchange of thermal energy between wood and the ...surrounding solar radiation as precisely as possible. Reliable and rapid measurement of thermal conductivity is one of the most important current industrial requirements. The aim of this study is to examine the validity of using the modified transient plane source method (MTPS), which uses the principle of one-sided heating of the sample, and is defined by the ASTM D7984-21 (2021) standard, for determining the thermal conductivity of complex biocomposite composite materials such as wood. The analysis of the available literature shows a lack of data on the thermal conductivity of the type of wood originating in Croatia. In this study, the thermal conductivities of beech and fir wood samples in the longitudinal direction was determined by the MTPS method depending on the temperature and moisture content in the samples. Measurements were made on samples with a moisture content of 0%, 10%, and 20% in the temperature range from 20 to 80 °C.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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