Thesis (doctoral)--Christian-Albrechts-Universität zu Kiel, 2003.

Cottbus, Techn. Univ., Diss., 2006 (Nicht für den Austausch)

Zugl.: Hamburg, Techn. Univ., Diss. 2009

I en värld med ökande koldioxidhalter i atmosfären och höjd medeltemperatur, råder det inga tvivel om att vi står inför en rad utmaningar för att minska användandet av bland annat fossila bränslen som generar skadliga utsläpp. Det finns många alternativ till oljebaserade bränslen, och ett som har ökat markant de senaste åren är bränslepellets. Bränslepellets är ett träbaserat biobränsle som i sitt kompakta tillstånd erbjuder ett bra värmevärde och är klimatneutralt. För att tillverka pellets måste råmaterialet först termiskt torkas, från en fukthalt på ca 55 % till ca 10 %, vilket i dagsläget kan motsvara upp till en fjärdedel av hela energiåtgången i pelleteringsprocessen. Med den ökade efterfrågan av bränslepellets finns också ökade förutsättningar för energieffektiviseringar i pelletsproduceringen, speciellt i torkningssteget.   Drinor AB har tagit fram en avvattningsmaskin av biomaterial som heter CDP, och med den är det möjligt att avvattna biomaterial till ca 30 %, vilket skulle reducera både tiden och energin det tar att termiskt torka materialet. Avvattningen sker under tryck på minst 40 ton, där vattnet mekaniskt pressas ut ur råmaterialet. Hur avvattningen påverkar råmaterialet, speciellt i en pelletframställning, är oklart och syftet med detta arbete var att ta reda på hur pelleteringsegenskaperna påverkas efter pressning med CDP, och om det finns möjligheter att spara energi i malningsdelen i pelleteringsprocessen.   Målet med arbetet var att ta reda på hur CDP påverkar pelletskvaliteter i form av hårdhet och densitet, samt om friktionsutvecklingen i pelleteringsmatrisen förändras, genom att framställa pellets ur 3 scenarion. I ett scenario ska en traditionell pelletsframställning liknas, med endast termisk torkning och i de resterande två scenarion implementeras CDP som försteg till den termiska torkningen. I ett av dessa två scenarion mals inte träflisen innan pelletering, för att se om energi kan sparas utan att offra pelletskvalitet. Ett annat mål var att, per scenario, ta reda på vid vilken fukthalts- och temperaturkombination de bästa pelletsen tillverkades med avseende på hög densitet och hårdhet samt låg friktionsutveckling.   Resultaten visade att scenariot med CDP som komplement till termisk torkning och utan malningprocess, producerade pellets med högst hårdhet, högst densitet och lägst friktionsutveckling under båda fukthalterna på pelleteringsmaterialet och nästintill samtliga matristemperaturer. Det scenario som hade endast termisk torkning producerade pellets med lägst densitet och hårdhet samt högst friktion under nästan alla temperaturer och fukthalter.   När den bästa fukthalts- och temperaturkombinationen togs fram per scenario, så var scenariot med CDP och utan malning bäst. Pellets producerade där hade ökad densitet, nästan tredubblad hårdhet samt mer än halverad friktionsutveckling i pelleteringsmatrisen, jämfört med scenariot som imiterade traditionell pelletsframställning med endast termisk torkning.   Skulle det scenariot med CDP och utan malningsprocess implementeras i en verklig industriell skala skulle det innebära stora förutsättningar för ökad produktion av pellets med bättre kvalitet, samt ett minskat energianvändande i form av reducerad termisk torkning och minskat användande av malningsprocessen. / In a world with growing carbon dioxide contents in the atmosphere and elevated average temperature, there is no doubt that we are faced with a number of challenges to reduce the use of, among other things, fossil fuels that generate harmful emissions. There are many alternatives to oil-based fuels, and one that has increased markedly in recent years is fuel pellets. Fuel pellets are a wood-based biofuel that, in its compact state, offers a good thermal value and is climate neutral. In order to produce pellets, the raw material must first be thermally dried, from a moisture content of about 55 % to about 10 %, which can currently account for up to at least a quarter of the total energy consumption in the pelleting process. With the increased demand for fuel pellets, there are also increased possibilities for energy efficiency in the pellet production, especially in the drying stage.   Drinor AB has developed a biomaterial dewatering machine called CDP, with which it is possible to drain the biomaterial to a moisture content of about 30%, which would reduce both the time and the energy it takes to thermally dry the material. The dewatering pressure is at least 40 tonnes, where the water is mechanically squeezed out of the raw material. How the dewatering affects the raw material, especially in a pellet production, is unclear and the purpose of this work was to find out how the pelleting properties are affected after pressing with CDP and if there is potential for saving energy in the grinding process in the pelleting process.   The aim of the work was to find out how CDP affects pellet qualities in terms of hardness and density, and if the friction development in the pelleting dye changes, by making pellets out of 3 scenarios. In one scenario, traditional pellets production should be resembled, with only thermal drying, and in the remaining two scenarios, CDP is implemented as a complement to thermal drying. In one of these two scenarios, the wood chips were not milled before pelleting, to see if energy can be saved without sacrificing pellet quality. Another goal was to determine, by each scenario, what moisture and temperature combination the best pellets were produced with respect to high density and hardness and low friction development.   The results showed that the CDP scenario, as a complement to thermal drying and without grinding process, produced the hardest pellets, highest density and lowest friction development during both moisture levels of the pelleting material and almost all die temperatures. The scenario that only had thermal drying produced pellets with the lowest density and hardness, as well as maximum friction under almost all temperatures and moisture levels.   When the best moisture and temperature combination was achieved by each scenario, the scenario with CDP and without grinding was the best. Pellets produced there had increased density, almost triple the hardness, and more than half the friction development in the pelleting die, compared to the scenario that imitated traditional pellets production with only thermal drying.   Should the scenario with CDP and without grinding process be implemented on a real industrial scale, it would provide great conditions for increased production of better quality pellets, as well as reduced energy use in the form of reduced thermal drying and reduced use of the grinding process.

Denna rapport baseras på experimentella försök där det undersökts hur pelletdensiteten påverkar utsläpp av kolmonoxid (CO) och stoft vid småskalig förbränning. I en testpanna med ansluten pelletsbrännare testades tre densiteter: låg, mellan och hög. Testerna uppdelades i tre faser i form av uppstart, kontinuerlig drift och släckning. Tre repetitioner gjordes på varje fas och för varje bränsle med undantag av släckning där endast en mätning per bränsle gjordes. Resultatet visade generellt en tydlig skillnad i CO-emission. Oberoende av densitet var CO-emissionerna mycket större vid uppstart och släckning än vid kontinuerlig drift. Avseende densitet gavs ett entydigt resultat där den lägsta pelletdensiteten gav högre stoftemissioner under alla driftsförhållanden. Skillnaden mellan de två pelletssorterna av högre densitet är däremot inte signifikant. För CO-emissioner sågs vid uppstartsfasen en tydlig trend mellan minskad pelletdensitet och ökade CO-emissioner. Vid kontinuerlig drift sågs emellertid det omvända: hög densitet gav högre CO-emissioner, varvid mellandensiteten gav något lägre CO-emissioner och låg densitet gav lägst CO-emissioner. Om skillnaden är uteslutande beroende på pelletdensiteten är svårt att säga. Ytterligare försök rekommenderas för att avgöra den exakta inverkan av pelletarnas densitet.

No description available.

<p>In this study 4 solar and pellet heating systems have been studied with the help of annual dynamic simulations. Two of the systems comprised a pellet stove and two systems were solar combisystems; one with a store integrated pellet burner, the other with a separate pellet boiler.</p><p>The aim was to evaluate their thermal performance and their CO-emissions. The systems have been modelled based on lab measurements of the single system components. The used models allow a detailed study of the dynamic behaviour of the systems.</p><p>The stove systems have the least primary energy consumption provided the auxiliary electricity is taken into account with a conversion factor of 100%. If the auxiliary electricity is taken into account with a conversion of 40% and/or the systems are placed in the heated area the combisystems need less or a similar amount of primary energy.</p><p>Modulating combustion power reduces the number of starts and stops and for most pellet units this reduces the total CO emissions. The obtained annual CO emissions are higher than the values obtained from the standard test methods. It was shown that the average emissions under realistic annual conditions were greater than the limit values of two Eco-labels.</p><p>The system performance can be significantly improved by a proper control of the pellet heater and by sizing the pellet heater according to the size of the peak space heating demand.</p><p>Based on these findings from the simulations two prototypes of a combined solar and pellet heating system has been designed, built and tested; one for the lab and one that has been installed in a demonstration house. The system is very compact and is suitable for detached houses with no heating room or little space for a heating room.</p>

In this study 4 solar and pellet heating systems have been studied with the help of annual dynamic simulations. Two of the systems comprised a pellet stove and two systems were solar combisystems; one with a store integrated pellet burner, the other with a separate pellet boiler. The aim was to evaluate their thermal performance and their CO-emissions. The systems have been modelled based on lab measurements of the single system components. The used models allow a detailed study of the dynamic behaviour of the systems. The stove systems have the least primary energy consumption provided the auxiliary electricity is taken into account with a conversion factor of 100%. If the auxiliary electricity is taken into account with a conversion of 40% and/or the systems are placed in the heated area the combisystems need less or a similar amount of primary energy. Modulating combustion power reduces the number of starts and stops and for most pellet units this reduces the total CO emissions. The obtained annual CO emissions are higher than the values obtained from the standard test methods. It was shown that the average emissions under realistic annual conditions were greater than the limit values of two Eco-labels. The system performance can be significantly improved by a proper control of the pellet heater and by sizing the pellet heater according to the size of the peak space heating demand. Based on these findings from the simulations two prototypes of a combined solar and pellet heating system has been designed, built and tested; one for the lab and one that has been installed in a demonstration house. The system is very compact and is suitable for detached houses with no heating room or little space for a heating room.

A novel compacted, torrefied, spherical biomass pellet, known as the "Q'Pellet", is aimed at overcoming the challenges of modern biomass pellets by building on the bene fits of torrefaction and utilizing the durability of a sphere. Pellets were made from both untreated hybrid poplar sawdust and material that had been partially torrefied at 250 C, allowing the torrefaction and pelletizing stages to be decoupled. A pelletizing die pre-heated to 280 C was successfully used to heat and torrefy room temperature raw and pre-torrefi ed material, greatly reducing the time required to produce each pellet. All Q'Pellets demonstrated 100% mechanical durability, and did not abrade during a tumbling can test or fracture during an impact resistance (drop) test. The gross calori fic value (GCV), ash and nitrogen content of pellets produced from raw hybrid poplar were 21.29+/-0.08 MJ/kg, 2.42+/-0.23 wt%, and <0.01 wt%, respectively. The GCV, ash and nitrogen content of pellets produced from pre-torre ed material were 21.25+/-0.34 MJ/kg, 3.58+/-1.11 wt%, and 0.42+/-0.03 wt%, respectively. The Q'Pellet was compared to biomass fuel speci fications in Europe and North America. The experiments performed herein provided an understanding of the material and process properties and limitations. Design speci fications for the development of a continuous pelletizing process were outlined. BGM Metalworks Inc has been hired by Queen's University to assist in the design and to fabricate the continuous pelletizing apparatus. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2014-05-06 14:04:54.059

Zugl.: Aachen, Techn. Hochsch., Diss., 2009