The main goal of this contribution is to present results of analyse of mathematical models of wood biomass compacting. Doesn't exist a lot of models which describes real state in pressing chamber and amount of factors impact at compacting process and thereby on briquette quality. According to our suggestion have also constructional parameters of pressing chamber (pressing spout and pressing ram) expressive impact on result briquette quality. We did theoretical analyses which showed us that impact on briquette quality have also change of pressing chamber length, change of friction coefficient, change of pressing chamber conicalness and also change of pressing chamber diameter

Djordje Vukelić

Peter Krizan

International Journal for Quality Research

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International Journal for Quality research  UDK- 674.8                            Short Scientific Paper (1.03)                                                        Vol.2, No. 3, 2008                                                193        Peter Krizan1),   Djordje Vukelić2)  Slovak university of technology, Slovakia 1) University of Novi Sad y, Serbia2)   Shape of Pressing Chamber for Wood Biomass Compacting  Abstract: The main goal of this contribution is to present results of analyse of mathematical models of wood biomass compacting. Doesn’t exist a lot of models which describes real state in pressing chamber and amount of factors impact at compacting process and thereby on briquette quality. According to our suggestion have also constructional parameters of pressing chamber (pressing spout and pressing ram) expressive impact on result briquette quality. We did theoretical analyses which showed us that impact on briquette quality have also change of pressing chamber length, change of friction coefficient, change of pressing chamber conicalness and also change of pressing chamber diameter  Keywords: shape of pressing chamber, conicalness of pressing chamber, mathematical model of compacting, briquette quality, compacting pressure    1. INTRODUCTION  By experience we know that not only technological parameters (compacting pressure, pressing temperature, material humidity and fraction largeness) have impact on result briquette quality however also constructional parameters (pressing chamber length, pressing chamber conicalness, friction coefficient between pressing chamber and pressed material). The goal of this analyze is to obtain more knowledge about impacts of all constructional parameters on result briquette quality, to obtain knowledge about interaction relations between lonely parameters, which should be the base for optimalisation of compacting process. After these analyses we would like to verify results on our designed experimental pressing stand (Fig. 2 and Fig. 3).           2. MATHEMATICAL MODEL OF       COMPACTING       On Fig.1 we can see described pressing process on vertical press. Maximal compacting pressure Pk which is rising by pressing depend on pressing chamber length and shape, depend on friction relations between pressed material and wall of the chamber. Drag friction is backward assigned by radial pressure Pr, applied to chamber wall, by friction largeness μ and pressing chamber length L. Required compacting pressure Pk we are able to obtain with right dimensioning, with construction and with changing of pressing chamber length. Equation (1) describes Fig.1. ( )[ ] 0...Pr.4..2=−+− dxdddPmPmPm πμπ .....(1)  By equation (1) solving and by border conditions substituting we get equation (2). dLGk ePP...4.μλ= .......................................(2)  We analyzed equation (2) and we monitored impact of changing of pressing chamber length and impact of changing of  194                                                P. Krizan, Dj. Vukelić                                                friction coefficient on axial pressure on extrusion (Pm).  dxdLxPkPGPmPm+dPmµ.PrPr Prµ.Pr Pk – axial pressure of ram [MPa] Pr – radial pressure [MPa] PG – backpressure in pressing chamber [MPa] Pm – axial pressure on extrusion [MPa]  d – diameter of pressinf chamber [m]  μ – friction coefficent [-] L – pressing chamber length [m] Figure 1 – Pressing process on vertical press   3. IMPACT OF PRESSING CHAMBER LENGTH  At analyze of change of pressing chamber length impact we chose as a base value L=140 mm, because in our experimental pressing stand we are limited by construction. We raised this value about 10%. Other parameters we chose according to designed experimental pressing stand. 5,010 →⇒÷∈== choosePPmrmrσσλ (3)  μ= 0,35; d= 0,02 m; PG = 1 MPa   175,020,015,0 →⇒÷≅= choosePPkrα (4)  krkr PPPP .175,0175,0 =⇒= ................(5)  By substituting (5) into (3) we get equation (6): mk PP .86,2= ............................................(6)  By completing of equation (6) into the equation (2) we get equation (7): dLGm ePP...4.86,2μλ= ................................(7)  L [mm] 140 126 113,4 102 91,8 82 changeof L [%] - -10 -10 -10 -10 -10 Pm [MPa] 46,95 28,77 18,51 12,42 8,7 6,17 changeof Pm [%] - -38,7 -35,7 -32,9 -29,95 -29 Table 1 – Calculated values for pressing chamber length „L“    Figure 2 – 3D model of pressing stand   Figure 3 –Experimental pressing stand                                                         Vol.2, No. 3, 2008                                                195  Figure 4 – Dependence of axial pressure on pressing chamber length  Results of this analyze is when we increase pressing chamber length also increase the compacting pressure on extrusion Pm. At enlarging the pressing chamber length about 10% compacting pressure increase average about 33%.   4. IMPACT OF FRICTION COEFFICIENT  At analyze of change of friction coefficient we chose as a base value μ=0, 1. We raised this value about 20% from interval of values <0,1÷0,4>, which is interval of friction coefficient values for steel - wood. Other parameters we chose according to designed experimental pressing stand. 5,010 →⇒÷∈== choosePPmrmrσσλ  L= 0,14 m; d= 0,02 m; PG = 1 MPa. At calculation we worked with mathematical model – equation (7). μ [-] change of μ [%] Pm [MPa] change of Pm [%] 0,1 - 1,42 - 0,12 20 1,88 32,4 0,144 20 2,63 40 0,173 20 3,94 50 0,21 20 6,61 68 0,252 20 11,91 80,2 0,3 20 23,32 96 0,36 20 54 131,6 0,432 20 148 174 Table 2 – Calculated values for friction coefficient „μ”   Figure 5 – Dependence of axial pressure on friction coefficient  Result is follow - compacting pressure exponential increase at enlarging the friction coefficient about 20%.   5.  IMPACT OF PRESSING CHAMBER DIAMETER  At analyze of change of pressing chamber diameter we chose as a base value d=20 mm. We raised this value about 20% in interval of values <20 ÷ 50 mm>, which is interval is interval values according to designed experimental pressing stand. Other parameters we chose according to designed experimental pressing stand. 5,010 →⇒÷∈== choosenPPmrmrσσλ Chosen constant parameters: L=0,14 m; μ=0,35 ; PG = 1 MPa  At calculation we worked with mathematical model – equation (7). d [mm] 20 24 29,8 35,56 42,67 change of d [%] - 20 20 20 20 Pm [MPa] 46,95 21,1 9,5 6,15 3,48 change of Pm [%] - 55 55 35,3 43,4 Table 3 – Calculated values for pressing chamber diameter „d”   196                                                P. Krizan, Dj. Vukelić                                                 Figure 6 – Dependence of axial pressure on pressing chamber diameter  Result of this analyze was awaited - compacting pressure on extrusion exponential decrease at enlarging of pressing chamber diameter.   6.  EXPERIMENTS PREPARING   Results of these analyses show us that pressing chamber length and friction coefficient are parameters which have expressive impact as on compacting pressure so as on overall compacting process and briquette quality. We think that also conicalness of pressing chamber has also great impact on compacting pressure. It is necessary to make experiments in this field and to reach of shape and dimensional optimalisation of pressing chamber and pressing spout. We have to verify results of analyses by experiments. We designed following types of pressing chambers in various dimensional scales. dlh=lk Figure 7 –Pressing chamber with constant diameter and varied length  dlklhx Figure 8 –Pressing chamber with varied length of conic and varied angle of conic  dlh=x Figure 9 –Pressing chamber with varied angle of conic through full chamber  dlkxlh Figure 10 –Pressing chamber with constant length of conic and varied angle of conic   In this time we make this experiments therefore I don’t have know results.   7.  CONCLUSION  Pressing chambers or pressing spouts are parts of compacting machines which belongs to the group of machine parts which are extreme shabby. Therefore it is necessary to make shape and dimensional optimalisation of pressing chambers from shabby point of view. By decreasing of pressing chambers shabby we increase of result extrusion hour production. But this optimalisation will have impact also on result briquette quality. We try to design those pressing chambers which will be able to work                                                         Vol.2, No. 3, 2008                                                197 by lower compacting pressures and will produce asked result briquette quality. Conicalness of pressing chamber is advantageous from pressures distribution in chamber point of view. We know that when we use conic shape chamber at the same compacting pressure we are able to produce better quality briquettes as with cylindrical shape of chamber. Impact of pressing chamber conicalness is necessary to verify by experiments in practice on real compacting machines.  • We would like to input results of shape and dimensional optimalision to the mathematical model which describes compacting process and where is included only some technological parameters till now.    REFERENCES  [1] Holm, J., Henriksen, U., Hustad, J., Sorensen, L.: Toward an understanding of controlling parameters in softwood and hardwood pellets production, published on web 09/09/2006, American Chemical Society. [2] Križan, P.: Experimental research of factors impact on briquette quality at compacting process, In: Proceedings from 1. International conference of young research workers and PhD. students ERIN 2007, 25-26.04.2007, Bratislava, ISBN 978-80-227-2636-8. [3] Križan, P.: Impact of factors at biomass compacting process, In.: Proceedings from 13. International conference TOP 2007, 26.-28.06.2007, Senec, ISBN 978-80-227-2693-1, page 381-386. [4] Šooš, Ľ., Križan, P.: Analyze of forces interaction in pressing chamber of briquetting machine, In.: Proceedings from 11. International conference TOP 2005, 29.06.-01.07.2005, Častá-Papiernička, ISBN 80-227-2249-9, page 299-306. [5] Hodolic, J., Vukelic, Dj., Agarski, B., Hudjik, C.: Briquetting of biomass and environmental engineering, Proceedings - Quality Festival 2007 - 2. Conference About Quality of Life, Kragujevac: Center for Quality - Faculty for Mechanical Engineering, pp. 8. - 11. May, 2007, ISBN 85-86663-09-5. [6] Hodolic, J., Vukelic, Dj., Agarski, B.: Biomass briquetting and enviromental protection in the region of province of Vojvodina, Proceeding - Engineering of Enviroment protection TOP 2007, Bratislava: Slovac University of Technology in Bratislava, 26. - 28. June, 2007, pp. 111.- 116., ISBN 978-80-227-2693-1.                     Recived:      04.06.2008 Accepted:  16.08.2008 Open for discussion:        1 Year  

SHAPE OF PRESSING CHAMBER FOR WOOD BIOMASS COMPACTING

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