Thermally modified hybrid aspen

This thesis is focused on thermal modification of hybrid aspen (Populus tremula L. x Populus tremuloides Michx.), its mechanical properties, wood defects and potential use in construction. In the recent years, wood as a building material has become increasingly popular. It is preferred because of its aesthetic appeal; it is renewable and substitutes fossil-based energy consuming materials. However, greater use of wooden products can also put more pressure on our natural forests. The main problems discussed in this paper were: mechanical characteristics after intense thermal modification and overall quality characteristics of thermally modified hybrid aspen. The present thesis conducts an empirical research of harvesting model trees, band sawing them into boards and kiln-drying, in order to prepare samples for thermal modification. Specimens were prepared for compressive strength, bending strength and wood density testing. Mechanical tests were carried out following the standards of ISO 13061-17, ISO 13061-3 and ISO 13061-2, accordingly. Furthermore, thermally treated sample boards from hybrid aspen (Populus tremula L. x Populus tremuloides Michx.), were evaluated according to 14 predetermined quality characteristics. Thermally modified hybrid aspen showed lower wood density and lower bending strength, but higher compressive strength in comparison with untreated hybrid aspen material. Wood quality evaluation showed that hybrid aspen had almost two times more wood defects compared to European aspen. Thermal modification process had statistically insignificant effect on measured wood quality. As a result, it can be said, that despite the decrease of some mechanical properties, thermally modified hybrid aspen still has a potential in areas where load bearing abilities are not so important, for example sauna interiors and interior panelling

Tulevikuresidentuur

Eesti Arst 2019; 98(5):255–26

Mechanical durability of wood pellets at the example of OÜ Puidukoda

Bakalaureusetöö Metsanduse õppekavalEuroopa Liidu kliimapoliitika raames 2020. aastaks võetud eesmärgid ja otsused toetamaks taastuvenergia kasutusele võtmist on pannud riigid otsima võimalusi rohelise energia osakaalu suurendamiseks. Puitpelletile omane suur energia kontsentreeritus ja võrdlemisi lihtne kasutusele võtmine kivisöe kateldes teeb sellest ideaalse kütuse. Käesoleva bakalaureusetööl oli kaks eesmärki, esiteks uurida kuidas mõjutab vee ja lisandite kasutamine puitpelletite mehaanilisi omadusi ja teiseks teostada kvaliteedianalüüs OÜ Puidukoda pelletite põhjal. Töö käigus koguti liinilt proove ja mõõdeti puitpelletite niiskusesisaldus, mahukaal, temperatuur ja peenete osade protsent. Mõõtmisi teostati pooleteise aasta jooksul ja saadud andmete põhjal hinnati toodangu kvaliteeti. Töö tulemustest on näha, et kõige parema toodangu saame 8-9,5 protsendise niiskuse juures, kuid kõrgema kui 10% niiskuse juures suureneb pelletite purusus järsult. Lisaainete kasutamine tõstab kvaliteeti, enim parandab seda 2% ligniini lisamine. Kogutud proovide põhjal tuleb OÜ Puidukoda lisaaineteta toodangu keskmiseks mehaaniliseks tugevuseks 96,5%.European Union’s climate policies and subsidies for meeting 2020 goals, has made countries look for ways to increase the share of green energy. The high energy concentration of wood pellets and their relatively easy use in coal boilers makes it an ideal fuel. This bachelor’s thesis had two aims. First aim was to reasearch how the use of water and additives affects the mechanical properties of wood pellets and secondly to carry out a general quality analysis of OÜ Puidukoda pellet production. During research samples were taken from production line. Moisture content, volumetric weight, temperature and percentage of fines was measured. Measurements were carried out over a year and a half and the quality of the production was assessed on the basis of the data obtained. The results of the work show that wood pellets have the best durability when they contain around 8-9,5% of water, after going over that level mechanical durability drops drastically. Additives improve quality of wood pellets, research shows that best results come out of using 2% lignin. Collected samples show that OÜ Puidukoda wood pellets mechanical durability is around 96,5%