Proces peletiranja biomase - pregled literature

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

Obilježja procesa obrade na horizontalnoj tračnoj pili trupčari pri piljenju zamrznute bukovine

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.U radu se iznose rezultati istraživanja obilježja procesa piljenja bukovih prizmi na horizontalnoj tračnoj pili trupčari proizvođača Mebor, model HTZ-1000. Za piljenje su primijenjeni listovi pila sa stlačenim i stelitiranim zubima. Proučavana je snaga potrebna za piljenje, postojanost alata, hrapavost obrađene plohe i odstupanje debljine piljenica od nominalne dimenzije, i to tijekom piljenja prizmi ukupne duljine 6000 m. Svi proučavani parametri praćeni su tijekom vremena postojanosti pojedinog lista pile. Proces trošenja zubi lista pile promatran je kao funkcija duljine puta zahvata tijekom piljenja. Također je analiziran utjecaj postupnog zatupljivanja zubi lista pile na energiju potrebnu za piljenje, na kvalitetu obrađene plohe i na odstupanje dimenzija piljenica s obzirom na nominalne vrijednosti. Uzimajući u obzir proces zatupljivanja zubi lista pile i utjecaj na promatrane parametre obrade, određeno je optimalno vrijeme zamjene lista pile. Na temelju izmjerenih parametara zaključeno je koji je način pripreme zubi pile preporučljiv za piljenje zamrznute bukovine

CAN BIOMASS TRIGGER AN ENERGY-WISE TRANSITION IN CROATIA AND REST OF SOUTHEASTERN EUROPE?

Šumska biomasa predstavlja važan izvor energije, čijem bi se korištenju u budućnosti trebalo posvetiti znatno više pozornosti. Biomasa u svojim tradicionalnim oblicima je i dalje vrlo važan izvor energije u većini zemalje Jugoistočne Europe, te će u doglednoj budućnosti i dalje biti tako. Međutim, sve se više koristi ne samo za proizvodnju toplinske energije, već za proizvodnju električne i rashladne energije, i to se smatra kao važan dio energijske tranzicije koja je obećavajući model s visokim ekonomskim i ekološkim prednostima. Korištenje energije biomase pruža znatne mogućnosti za otvaranje novih radnih mjesta, te tako može imati znatan pozitivan utjecaj na lokalno i nacionalno gospodarstvo. U radu se opisuje trenutnu fazu energijske tranzicije u zemljama jugoistočne Europe ti ulogu šumske biomase u njegovoj provedbi. Analizirani su primjeri i događanja u Albaniji, Bosni i Hercegovini, Hrvatskoj, Makedoniji, Kosovu i Srbiji. Uporaba biomase kao energenta u ruralnim područjim, potiče stvaranje dodatnih prihoda, povećava proizvodnost te omogućava otvaranje malih seoskih poduzeća. Iz makroekonomske perspektiv, uporaba biomase doprinosi svim bitnim elementima razvoja zemalja jugoistočne Europe.Ključni pokretači, kao i prepreke na koje se može naići pri energijskoj tranziciji u jedinicama lokalne samouprave, mogu se strukturirati kao; poticaj iz potencijala, poticaj od tržišta korištenje trgovačkih i poslovnih veza, biti prvi ili lokalni ponos, zadržati novac kod kuće.U radu je prepoznat velii broj potencijalnih skupina prepreka za korištenje šumske biomase; gospodarska ograničenja, financijska ograničenja kao ozbiljna prepreka za mnoge lokalne samouprave, društvena ograničenja, ograničenja u ljudskim resursima, ograničenja zbog transparentnosti te na kraju tehnička ograničenja.Through the history of mankind, until the mid-19th century, biomass, particularly wood, represented the most important source of energy. In many countries of Europe, the awareness of the importance of forest biomass as fuel has been closely connected to the general understanding and the realization of own and world energetic situation. Forest biomass represents an important source of energy, whose use should be paid more attention to in the future. In its traditional forms, biomass is still a very significant source of energy in most countries of the southeast Europe and it will continue to be so in the near future. However, it is more and more used not just for thermal energy production, but also for the production of electric and cooling energy which is considered as an important part of the energetic transition which is a promising model with high economic and ecological advantages. The use of biomass energy offers significant possibilities for opening new jobs, thus having a significant positive impact on the local and national economy. This paper describes the present stage of the energetic transition in the south-eastern European countries and the role of forest biomass in its implementation. Examples and events in Albania, Bosnia and Herzegovina, Croatia, Macedonia, Kosovo and Serbia are analysed. Rural development projects as well as the use of bioenergy biomass has a great potential for income generation, increase of productivity and opening of small village companies. From the macroeconomic perspective, the use of biomass contributes to all the important elements in the development of the south-eastern European countries.Key drivers as well as the obstacles which can be encountered in the energetic transition in local government units can be structured as follows; potential stimulus, refers to the most south-eastern European countries regarding their significant afforestation and forest biomass potential, market stimulus due to cost-effective accessible plants and equipment for biomass, as well as the adequate support of manufacturing firms, the use of commercial and business connections: where most of biomass trades among the south-eastern European countries and EU is carried out in integration with the forest product trade, to be first or the local pride, is an important driver in the south-eastern European countries to keep money at home is another important link with the positive perception in the use of the forest biomass. The paper recognised a significant number of potential groups of obstacles for using the forest biomass; economic limitations more favourable price of the forest biomass energy in relation to fossil fuels, financial limitations as a serious obstacle for each form of the renewable energy, social limitations are very specific for each form of the renewable energy, human resource limitations since most local governments do not have sufficient human potential, limitations due to transparency are a very frequent problem, primarily depends on the democratic power, technical limitations mostly belong to the fact that most of the equipment for using renewable energy sources and the increase in energetic efficiency from the import, has not been produced on the local level

Biološka otpornost johovine termički modificirane u ulju

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.U radu su prezentirani preliminarni rezultati biološke otpornosti drva johe (Alnus glutinosa) termički modificiranoga u sojinu ulju protiv čistih kultura gljiva truležnica (Postia placenta i Trametes versicolor) u laboratorijskim uvjetima metodom mini blok prema CEN TS 15083-1. Modifikacija je izvedena zagrijavanjem uzoraka uronjenih u sojino ulje sobne temperature. Četiri načina termičke modifikacije razlikovala su se po trajanju držanja drva (6 i 10 sati) na konačnoj temperaturi (180 i 200 ºC). Usto je određena i prirodna otpornost johovine u usporedbi s prirodnom otpornosti bukovine kao referentne prirodno slabo otporne vrste drva. Mjereno je povećanje mase modifikacijom (DMM) i gubitak mase djelovanjem spomenutih gljiva (GMG). Nakon modifikacije pri višoj temperaturi DMM drva johe bio je manji nego nakon modifi kacije pri nižoj temperaturi. Slično tome, dulji je tretman rezultirao nižim DMM-om nego kraći tretman. Rezultati su potvrdili povećanje biološke otpornosti modificirane johovine protiv obje testirane gljive truležnice. S povećanjem temperature modifikacije znatno se povećava biološka otpornost protiv obje gljive, dok produljenje vremena zagrijavanja ima blagi učinak povećanja biološke otpornosti. Utjecaj modifikacije na povećanje biološke otpornosti veći je protiv gljive smeđe truleži P. placenta. Utvrđeno je da je veći gubitkom mase modificiranih uzoraka djelovanjem gljive T. versicolor (u usporedbi s gubitak mase djelovanjem gljive P. placenta) najvjerojatnije nastao zbog razaranja preostalog ulja u drvu nakon modifikacije. Dokaz tome je crvena boja mikroskopskih preparata modificiranih uzoraka (postojanje lignina) te lokalna plava obojenost u lumenima traheja (nedostatak lignina). U lumenima traheja ostalo je najviše ulja nakon modifi kacije, pa se tu ujedno i najjače razvio micelij gljive bijele truleži T. versicolor, koji je, osim razgradnje ulja, djelomično uništio i lignin. Rezultati su pokazali da johovina termički modificirana u biljnom ulju, prema testiranim režimima, nije primjerena za upotrebu u razredima opasnosti 3 i višima

Contribution to the research on wood pellet characteristics from Turopolje area

U ovome radu analiziraju se kvalitativna svojstva peleta izrađenih iz vrsta drva turopoljskog kraja – sadržaj pepela, ogrjevna vrijednost, gustoća peleta i tlačna čvrstoća. Prikupljeni su uzorci hrasta lužnjaka (Quercus robur L.), običnoga graba (Carpinus betulus L.), poljskog jasena (Fraxinus angustifolia Vahl.), crne johe (Alnus glutinosa L.) i crne topole (Populus nigra L.). Prikupljeni i okorani uzorci usitnjeni su na mlinu s noževima na granulaciju 2,00 mm. Na uzorcima je ispitan sadržaj vode, pepela i ogrjevna vrijednost. Sadržaj pepela određen je zasebno za koru i drvo. Sadržaj pepela u kori pokazuje visok udio kod hrasta lužnjaka koji iznosi 13,64 % i graba sa 11,91 %, dok je kod ostalih vrsta udio pepela u kori između 7 i 10 %. Sadržaj pepela okoranog drva pokazuje vrijednosti 0,63 % za hrast, 0,50 % za jasen, 0,46 % za grab. Vrijednosti sadržaja pepela kod johe i topole bile su oko 0,4 %. Rezultati ukazuju na potrebu okoravanja u proizvodnji peleta s ciljem postizanja kvalitete peleta klase A1 i A2. Određivanjem ogrjevne vrijednosti najbolji rezultati utvrđeni su kod uzorka drva crne topole koja iznosi 19,63 MJ/g, a najmanja vrijednost izmjerena je kod uzorka graba 18,94 MJ/g. Nadalje, navedeni uzorci pomiješani su te su fomirane 3 grupe mješavina. Udio tvrdih vrsta listača hrasta, graba i jasena u svakoj pojedinoj mješavini bio je 60 % dok su u preostalom udjelu od 40 % jednoliko sudjelovale joha (20 %) i topola (20 %). Formirane mješavine materijala JTJ (jasen 60 : topola 20 : joha 20), HTJ (hrast 60 : topola 20 : joha 20) i GTJ (grab 60 : topola 20 : joha 20) prešane su u pelete uz pomoć hidrauličke laboratorijske preše pri 2 veličine sile (3,0 i 6,0 kN) i 2 temperature (150 i 200 °C). Po isprešanju, peleti su ostavljeni 15 dana da se dimenzijski stabiliziraju te su im određene dimenzije i gustoća. Peleti su potom ispitani na tlačnu čvrstoću u radijalnom smjeru pomoću kidalice. Peleti iz svih mješavina, prešani silom 6,0 kN kod temperature 200 °C pokazali su visoku gustoću koja je bila u rasponu 1 207 – 1 234 kg/m3. Peleti osnovne mješavine jasena dali su kod sile 3,0 kN i temperature 200 °C vrlo visoku gustoću od ≈ 1200 kg/m3, dok su općenito najmanju gustoću imali peleti osnovne mješavine graba kod svih režima prešanja. Rezultati tlačne čvrstoće u radijalnom smjeru pokazuju najbolje rezultate kod peleta prešanih pri 6,0 kN i 200 °C i to 13,59 MPa kod osnovne mješavine jasena, 11,1 MPa mješavine hrasta i 9,06 MPa mješavine graba.Ako se tlačna čvrstoća peleta promatra zbirno prema mješavini, značajno bolje rezultate daju peleti izrađeni iz mješavine jasena, topole i johe u usporedbi s ostale dvije mješavine.The paper deals with some quality characteristic of wood pellets from Turopolje area. The samples of pedunculate oak (Quercus robur L.), European hornbeam (Carpinus betulus L.), narrow-leaved ash (Fraxinus angustifoliaVahl.), European alder (Alnus glutinosa L.) and black poplar (Populus nigra L.) were collected. Collected and debarked samples were crushed by a mill with knives to 2.00 mm granulation. The content of water, ash and calorific value were examined on samples. The ash content was determined separately for the bark and the wood. The ash content in the barks shows a high rate in pedunculate oak which is 13.64 % and hornbeam with 11.91 %, while in other species the ash content in a bark is between 7 and 10 %. The ash content of a debarked wood shows the following values: 0.63 % for the oak, 0.50 % for the ash, 0.46 % for the hornbeam. Values of the ash content in the alder and the poplar were 0.4 %. Results indicate the need for debarking in pellet production in order to obtain the quality of class A1 and A2 pellet. By determining the calorific value the best results were determined in the black poplar sample which is 19.63 MJ/kg, and the lower value was measured in hornbeam sample 18.94 MJ/kg. Furthermore, the mentioned samples were mixed and 3 mixture groups were formed. The share of hard broad-leaved trees of oak, hornbeam and ash in each individual mixture was 60 %,while in the remaining 40 %,alder (20 %) and poplar (20 %) equally participated. Formed material mixtures APA (ash 60 : poplar 20 : alder 20), OPA (oak 60 : poplar 20 : alder 20) and HPA (hornbeam 60 : poplar 20 : alder 20) were pressed into pellets by hydraulic laboratory press in 2 forces (3.0 and 6.0 kN) and 2 temperatures (150 and 200 °C). After pressing, pellets were left for 15 days to stabilise in dimension and their dimension and density were determined. Then, pellets were checked for pressure strength in a radial direction by a testing machine. Pellets from all the mixtures, pressed by a force of 6.0 kN at 200 °C showed a high density in the range from 1 207 – 1 234 kg/m3. Pellets of basic ash mixture at force of 3.0 kN and at 200 °C gave high density≈ 1200 kg/m3, while the smallest density was generally given by pellets of basic hornbeam mixture in all pressing regimes. The results of pressure strength in radial direction give best results in pellets pressed at 6.0 kN and 200 °C which is 13.59 MPa with the basic ash mixture, 11.1 MPa with the basic oak mixture and 9.06 MPa of basic hornbeam mixture.If the pressure strength of a pellet is considered collectively according to the mixture, pellets made from the mixture of ash, poplar and alder give significantly better results in comparison to other two mixtures

Rationalization of manufacturing of plastic injection moulds by abrasive waterjet

Rad se bavi prijedlogom i teorijskim rješenjem za racionalizaciju proizvodnje dijelova kalupa za ubrizgavanje plastike rezanjem abrazivnim vodenim mlazom. Na temelju eksperimentalnih ispitivanja i primjenom napredne tehnologije abrazivnog vodenog mlaza u procesu proizvodnje kalupa za ubrizgavanje plastike, utvrđeno je da postoji mogućnost prilične uštede vremena, odnosno značajno smanjenje vremena proteklog od narudžbe do isporuke proizvoda. Na taj je način moguće povećati konkurentnost tvrtke i osigurati joj stabilnu poziciju na tržištu, čak i u vrijeme globalne krize.The article deals with a proposal and a theoretical solution for the rationalization of manufacturing of parts of plastic injection moulds by abrasive waterjet cutting. On the basis of experimental tests and by the application of advanced abrasive waterjet technology to the process of manufacturing of plastic injection moulds, it has been found that there is a possibility of considerable time saving, i.e. a marked shortage in time period from product ordering to dispatching. In such a way it is possible to increase the competitiveness of a company and to ensure its stable position on the market even in the time of global crisis

Influence of Biological Pretreatment of Wooden Dowels on Strength of Rotary Welded Joints

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

Durability of Universal Joint Elements Depending on Damages in the Phase of Transitional Occurrences

The paper considers the influence of the relationship betweenthe dynamic behaviour of the universal joint and thedamage in the period of transitional occurrences. Based on thetheoretical study of the shaft system with universal joints, theclassification, arrangement and value of dynamic loads havebeen determined, and the dynamic model desoibed by differentialequations has been defined. Laborat01y testing havebeen directed towards checking the safety and durability comparedto the structural requirements, precision and quality ofproduction, as well as mechanical and thermal treatment for acharacteristic type of a universal joint

Mogućnosti primjene infracrvene termografije u istraživanjima procesa mehaničke obrade drva

Radi povećanja kvalitete proizvoda od drva i postizanja konkurentnosti na tržištu, nužno je praćenje kvalitete procesa mehaničke obrade drva. Između ostalih činitelja, na kvalitetu obrade drva utječe i temperatura koja se razvija pri rezanju drva, jer povećanje temperature može dovesti do nestabilnosti alata, povećanja trenja između alata i obratka, loše kvalitete pa i propaljivanja obrađene površine drva. Dodatna opasnost povećanja temperature na mjestu rezanja drva je zagrijavanje odvojenih čestica drva koje se zračnom strujom transportiraju do mjesta skladištenja te su mogući inicijator nastanka požara ili eksplozije u sustavu za transport i skladištenje drvnih čestica (Blijderveen, 2010). Infracrvena termografija najviše se primjenjuje u području tehničkih znanosti, posebice u području građevinarstva i strojarstva. Rijetka je primjena infracrvene termografije u istraživanjima u području drvne tehnologije. Primjenom infracrvene termografije mogla bi se unaprijediti istraživanja utjecajnih činitelja na povećanje temperature na mjestu reza i zagrijavanje alata. Prema rezultatima provedenih probnih mjerenja pri piljenju bukovine uz posmičnu brzinu od 2 m/min maksimalna temperatura obrađene površine u kratkom vremenu (27 sekundi) iznosila je 120 °C, a maksimalne temperature odvojenih čestica bile su oko 60 °C. Nakon definiranja potrebnih konstanti za provedbu mjerenja, infracrvena termografija može poslužiti kao vrlo korisna metoda za praćenje procesa mehaničke obrade drva