The present researches are aimed at studying the physical and mechanical properties of pellets produced from hardwood. For the experiment black alder and birch widespread on the territory of the Republic of Belarus hardwood timber has been chosen. It is stated that the use of wood in an unaltered  form is impractical because the pellets derived from them have a low mechanical strength. The technological solution of this problem was the treatment of crushed wood raw material by saturated steam.  The results of industrial tests confirmed that wood particles activation of hardwood fuel pellets gives  the required quality standard. Technical feature of the technology is the use of a matrix with the length  of the pressing channel 33 mm

Dubodelova, E. V.

Khmyzov, I. A.

Snopkova, T. A.

Solovyeva, T. V.

Sychova, N. A.

The present researches are aimed at studying the physical and mechanical properties of pellets produced from hardwood. For the experiment black alder and birch widespread on the territory of the Republic of Belarus hardwood timber has been chosen. It is stated that the use of wood in an unaltered form is impractical because the pellets derived from them have a low mechanical strength. The technological solution of this problem was the treatment of crushed wood raw material by saturated steam. The results of industrial tests confirmed that wood particles activation of hardwood fuel pellets gives the required quality standard. Technical feature of the technology is the use of a matrix with the length of the pressing channel 33 mm

Belarusian State Technological University

Chemistry and Technology of Wood Processing 127УДК 674.81 E. V. Dubodelova, PhD (Engineering), researcher (BSTU); N. A. Sychova, master’s degree student, engineer (BSTU); I. A. Khmyzov, PhD (Engineering), assistant professor, Dean (BSTU); T. A. Snopkova, researcher (BSTU); T. V. Solovyeva, D.Sc. (Engineering), professor (BSTU) TECHNOLOGY FEATURES OF FUEL PELLETS  FROM DECIDUOUS WOOD The present researches are aimed at studying the physical and mechanical properties of pellets pro-duced from hardwood. For the experiment black alder and birch widespread on the territory of the Re-public of Belarus hardwood timber has been chosen. It is stated that the use of wood in an unaltered form is impractical because the pellets derived from them have a low mechanical strength. The tech-nological solution of this problem was the treatment of crushed wood raw material by saturated steam. The results of industrial tests confirmed that wood particles activation of hardwood fuel pellets gives the required quality standard. Technical feature of the technology is the use of a matrix with the length of the pressing channel 33 mm. Introduction. The current trend in the devel-opment of fuel-power complex in the Republic of Belarus contacts with the greatest possible use of renewable and non-polluting sources of raw mate-rials. Timber cutting wastes and wood processing belong to such most available sources. These raw materials are a high-calorific fuel. The perspective using direction of wastes woodworking produc-tions is considered to manufacture the pressed ma-terials (biofuel) in the form of fuel granules. Today the market of fuel pellets extends enormous rates, and after the ratification of Kyoto Protocol about environmental protection by the majority of the states in the world (the Republic of Belarus ratified the contract in 2005) the demand for them grew in several times [1]. Coniferous woods in the form of sawmill wastes are traditionally applied in fuel pellet tech-nology. The wood of coniferous species is an ex-pensive and scarce raw material that is widely used in the woodworking industry [2]. Therefore the resources of this wood are steadily reduced. It re-sults in the work necessary to involve the direction of cheaper and invaluable softwood in fuel pellet technology that in a large part still doesn't find prac-tical satisfactory application in various branches of industrial production.  The technology and the properties of used wood raw material are known to make essential impact on the quality of produced biofuel. There-fore physics and mechanical quality indicators of fuel pellets derived from deciduous wood, and their comparison with those ones from coniferous wood – i. e. pine is of interest to study. According to references the structure, the morphology and the sizes of anatomic elements essentially differ not only coniferous and deciduous wood, but also a separate species [3].  Main part. The fuel pellets from the follow-ing forest species of Belarus – birches [Betula verrucosa Ehrh], an alder [by Alnus glutinosa (L.) Gaertn] and a pine [Pinus silvestris L.] were produced in vitro at the chemical woodworking processing chair of BSTU. The samples were made at granulation temperature 110°С and time of pressing 15 minutes. Humidity of initial raw materials was from 8 to 11 %, the fraction size was used 1.0/3.0, cooling of pellets was made as far as 20°С.  To research the physics and mechanical char-acteristics of obtained fuel pellet samples accord-ing to the requirements of STB 2027, humidity, ash-content, density, the lowest heat of combus-tion and mechanical durability was defined. The tests results of obtained fuel pellets are presented in Table 1.  Table 1 Physics and mechanical characteristics of fuel pellets Wood species Name indicator Pine Alder BirchHumidity, % 8.36 8.95 7.96 Ash-content, % 0.27 0.71 0.77 Density, kg/m3 1150 1200 1110 Mechanical durability, MPa 9.83 8.74 8.06 The lowest heat of a combus-tion, MDZh/kg 18.39 17.49 18.43 From Table 1 we can seen that the lowest heat combustion indicators of pellets from deciduous and coniferous wood are comparable and vary in the range from 17.49 to 18.43 MDZh/kg. As to an ash-content, deciduous wood pellets have ap-proximately in 3.5 times higher ash-content in comparison with coniferous ones. However the ashes that were formed during combustion can be applied as a fertilizer.  ISSN 1683-0377. Proceedings of BSTU. 2012. Issue 4. Chemistry, Organic Substances Technology and Biotechnology 128This experiment showed basically a possible replacement of coniferous wood by softwood in fuel pellets production. However obtained from alder and birch wood the pellets possessed the low-ered mechanical durability (respectively for 11 and 18%) in comparison with the reached one, when using wood of a pine. It doesn't allow its fully us-ing in fuel pellet composition. The results of indus-trial tests presented below showed that on applying additional processing by saturated steam of wood particles from deciduous species, it is possible to reach mechanical durability value of fuel pellets (granules), comparable with the reached one of coniferous wood. The process of wood particles steaming is a rather efficient way to increase the mechanical durability of fuel granules. Saturated steam effect resulted in the activation of wood components, the formation of new functional groups enhancing adhesive interactions during the process of pellets creation (granules). In the result of additional humidification of wood particles the temperature in the press granulator increased from 110 to 120°С. The high temperature of pressing provided a fast course of reactions and accumula-tion in a bigger amount of high-molecular com-pounds generally at the expense of high- reaction-ary gemicelluloses. The melted and softened com-ponents filled emptiness between fibers both capil-lary and submicrocapillary systems of cellular walls [4, 5]. Thus the quantity of wood compo-nents molecule cross-links, including spatial ones that provided the formation of strong products more and more increased. The trial tests of fuel pellets, derived from de-ciduous wood particles previously processed by saturated steam were carried out on JSC Vitebsk-drev. The pellets were obtained in the form of gra-nules in the following geometrical sizes: in the length of 10–30 mm and in diameter of 6 mm. The content of a birch in composition of granules made 35%, an alder – 20%, aspens – 40%, pines – 5% (definition of pedigree structure was carried out in accordance with GOST 15815–83). The full cycle production industrial line of fuel granules from vaporized wood particles includes the following basic equipment: the chopper, the crusher, the mill, the dryer, the press granulator equipped with the device for supply of saturated steam, the cooling column and the line on packing. The drawing shows the sequence of operations per-formance with use of the latter equipment [6].  Keeping of wood wastesSending to the finishing storageDrying of crushed productGrindingGrinding up to requirementСutting of wood chipsPackingCooling of pellets Press granulationGrading of pellets The sequence of operations in the production of fuel pellets with using deciduous wood  In the whole the technological process of fuel pellets produced with use of pine wood in addition to deciduous wood is rather simple, effortless and the most automated. The technical feature of production process was a matrix application with the length of the ef-fective pressing 33 mm(instead of 45 mm) channel as deciduous in comparison with coniferous wood demanded a shorter-term thermal processing. As a result there was an electricity consumption de-crease that involves a particular interest in use of various deciduous wood species in the fuel pellets technology.  Physics and mechanical characteristics of the obtained fuel granules are presented in Table 2.  Table 2 Physics and mechanical characteristics of fuel pellets made of the wood processed by saturated steam Wood species Indicator name Requirements STB 2027 Pine Deciduous wood composition Humidity, % 9–10 7.9 6.3 Ash-content, % 0.4–1.2 0.22 0.78 Density, kg/m3 1,200–1,400 1,170 1,220 Share of a trifle, % 7.0–8.5 1.4 2.0 The lowest heat of combustion, kJ/kg more than 16,900 17,520 17,810 Note. The indicators of a trifle share and the lowest heat of combustion were defined in scientific research insti-tute PCP BSU. Chemistry and Technology of Wood Processing 129From Table 2 we can see that the trifle share indicator of the fuel granules made of wood parti-cles processed by saturated steam has a low value that not only corresponds to STB 2027 require-ment, but also exceeds it in 3.5 times that confirms a high mechanical durability comparable with that one of pellets obtained of pine wood. Deciduous woods emit enough heat at combustion and their high-calorific capacity is allowed to be proved. Some increase of the ash-content indicator of the granules obtained from composition, containing deciduous wood is limited by permitted values on STB 2027.  In general fuel pellets in the form of the gran-ules, made during the experimental industrial tests corresponded to STB 2027 requirements.  Conclusion. The carried-out researches showed the possibility of almost complete re-placement in the production of fuel pellets in the form of granules of expensive and scarce conifer-ous wood on cheap and invaluable softwoods. It is realized by processing of wood particles by saturated steam directly before their pressing (granulation). The steam activation of deciduous wood particles enables to obtain fuel granules with the quality indicators satisfying the require-ments STB 2027. References 1. Васильев, Н. И. Пеллеты и топливные бри-кеты – прогрессивные виды твердого биотоп-лива / Н. И. Васильев // Энергосбережение. – 2011. – № 4. – С. 14–20. 2. Вторичные материальные ресурсы лесной и деревообрабатывающей промышленности (оборудование и использование): справочник / под ред. Г. М. Михайлова. – М.: Экономика, 1983. – 224 с. 3. Азаров, В. И. Химия древесины и синте-тических полимеров / В. И. Азаров, А. В. Буров, А. В. Оболенская. – СПб.: СПбЛТА, 1999. – 628 с. 4. Леонович, А. А. Физико-химические ос-новы образования древесных плит / А. А. Лео-нович. – СПб.: Химиздат, 2003. – 192 с. 5. Никитин, В. М. Химия древесины и цел-люлозы / В. М. Никитин, А. В. Оболенская,  В. П. Щеголев. – М.: Лесная пром-сть, 1978. – 368 с. 6. Мясоедова, В. В. Экологически чистые топливные брикеты и пеллеты на основе возоб-новляемого лигноцеллюлозного сырья и их пе-реработка / В. В. Мясоедова // Энциклопедиче-ский справочник. – 2011. – № 2. – С. 22–28. Received 21.03.2012  

Technology features of fuel pellets from deciduous wood

http://elib.belstu.by/bitstream/123456789/6505/1/030dubodelova-e.-v.-sychova-n.-a.-khmyzov-i.-a.-snopkova-t.-a.-solovyeva-t.-v.-technology.pdf

Technology features of fuel pellets from deciduous wood

Abstract

Similar works

Full text

Available Versions

Belarusian State Technological University