J O l RNAL OK SCIKNCK & TECHNOLOGY'''' * No 87 2012 CHARACTERIZATION OF VIETNAM BIOMASS FUEL PROPERTIES Ai\D INVESTIGATION OF THEIR COMBUSTION BEHAVIOR DANH GIA CAC D^C TJNH KY THU^T VA KHAO SAT QUA TRIN[.]
J O l RNAL OK SCIKNCK & TECHNOLOGY' * No 87 - 2012 CHARACTERIZATION OF VIETNAM BIOMASS FUEL PROPERTIES Ai\D INVESTIGATION OF THEIR COMBUSTION BEHAVIOR DANH GIA CAC D^C TJNH KY THU^T VA KHAO SAT QUA TRINH CHAY CUA NHIEN LI$U SINH K H I Van Dinh Son Tlw, Vo Cao Hong Thu, Nguyen Tien Cuong, Pliam Huang Luong Hanoi University of Science and Technology Received March 30 2012; accepted April 26 2012 ABSTRACT Biomass has been mcognized as an important renewable energy source for the near future in Vietnam and its potential equivalence to 12 GV\/,n However the application for industry has not been widely applied because of considerable problems encountered in using it for heat and power production This work deals with fuel properiies as well as thermal behavior of some selected biomass (nee husk, nee straw and saw dust) which am widely available for energy services in Vietnam The moisture of biomass is around 12-15% the volatile is In a range of 67-83% and the HHV is in a range of 18-20 MJ/kg There is two combustion processes for biomass fuel The volatile combustion occurred at 300°C-400°C and the char combustion was in a range 400-50(fC TOM TAT V&i trQ" luang u&c tinh khodng 12GV\/th phij phdm ndng Idm nghidp sS Id ngudn nhidn lidu quan cua Vidt Nam tmng tuang lai Nhien li$u cd ngudn gde phij phim ndng Idm nghiep ung dung de cung cdp nhidt vd didn v&i quy md cdng nghidp bdt diu duac quan tdm a nu&c ta Cdng trinh ndy ddnh gid cdc ddc tinh nhidn lidu ciia ba ngudn phu phdm cd tru- lugng l&n dd la triu rom va mun cua Phu pham ndng Idm nghidp cd hdm im cao tir 12-15%, hdm lugng chit bde tir 67-83% va HHV tir 18-20 Ml SO" dung phuang phdp phdn lich nhidl de ddnh gia qud trinh chdy cua c^c nhidn lieu trdn thiy ring giai doan chay chit bde cua smh khoi xdy tir 300oC-400oC va giai doan chay cacbon vimg 400-50(fC \ INTRODUCTION „ • • , u • J Biomass is mainiv snort-rotation woody , ', , „ crops and aencultural residues Biomass , '^ , , ° , , , , , absorbs carbon dioxide durint> erowth and -n r !_• emits it during combustion Thcreiore biomass , , , ^ , , •_, ,• helps the atmospheric carbon dio.xide recychne J , ^ , , , and does not contribute lo the greenhouse n„ ^ ,effect Biomass consumes the same amounl ot „„ • i_ • LUi from the atmosphere durinj' erowln as is , • *^ , , , , , - , released during combustion Worldwide , , c L biomass ranks fourth as an energy resource providing approximately 14% of the uorid s '^ '^ j ^ * ^ •' , energy needs and biomass is the most important c • J , • • r,i source ot enerey in the deve opine nations I f -wood, shortII Biomass fuels =•'potential includes , , rotation woody crops, agricultural ULISIC^ species, woody wastes, baggage, K •industrial ^ • residues waste paper, municipa so id waste , , ' : / ^ ^ r , sawdust, bio-so ids grass, waste from food ^, ,, ^ , ,., processing The Vietnam potential ot biomass ", , J' , ^ , derived from agricultural waste equivalences to n r-.i, J -.a-, ^-.w, r-,1 1-1 12GW,h and J.87 GWh [2 jJ The biomass samples for the characterization in this report are some mains , r,,• i i J • J •i residues of Vietnam aencultural and industrial , • i j processinE such as rice straw, rice husk and , Z, , j -i ij L sawdust Those samples are daily disposed huge ,, , j • iamount, collectable and convenience for , -,- • , j -ieathermg and ulilizalion In order to utilize f• _ c biomass as an importance sources for energy , • u • r •• production via combustion, gasification or , , _ r • pyrolysis process, the most important factor is / i • • cu - i the characterization ot biomass tuel properties There were several papers informed the fuel • r i.i i • i, properties of biomass however their results -.L i • i i ivary with location In general speaking, nee • u i u L- u u saw and rice husk have high ash content c-,vu nnH nee hiKk have hich ash content (around 10-20% dr\ basic) and Iheir HHV is in r - , ^ i,', I C J , L I '' '''"y^ °' 14-16 vl.lHHV kg Sawdust has very low content and their is approximately 18ash , „ , „ , , , -,-, ,,- u- ,- • 20MJ/kiif The objectives ot this investiealion ^.'^' - - , • • i e are: Characterization ol tuel properties of main , ,• \,- J • ,• ,.u biomass ot Vielnam and invesligalion the , , • -u• K >u i thermal behavior ot biomass usine bv thermal JOURNAL OF SCIENCE & TECHNOLOGY * No 87 - 2012 EXPERIMENTAL Fuel properties for the combustion analysis of biomass can be conveniently grouped into physical, chemical, thermal, and mineral properties Physical properties values vary greatly are related to fuel preparation methods Thermal property values such as specific heat, thermal conductivity, and emissivily vary with moisture content, temperature, and degree of thermal degradation by one order of magnitude Importanl chemical properties for combustion are the ultimate analysis, proximate analysis, analysis of pyrolysis products, higher heating value, heat of pyrolysis, heating value of the volatiles, and heating value of the char The Differential Scanning Calorimelric (DSC) were used to characterize the combustion reaction of biomass [4],[5] Analyses of biomass samples were carry out by DSC of STP 409-Netzsch The simultaneously measurements of mass loib (TG) vs lemperature and DSC of process vs temperature were made in a range 25-800''C and a linear heating rate of 10°C.min'' , the atmosphere used was air flowing at 50ml min' STP Table Method of hiomasK fuel uiiahiLi Properties Heating value Proximate analysis Moisture Ash Volatile matter Fixed- carbon Ultimate elemental Carbon and hydrogen Oxygen Ash elemental Analytical method ASTMD20I5 ASTME871 ASTMD1102 ASTM E872 By dilTerence ASTM E777 By difference By ICP-MS RESULTS AND DISCUSSION 3.1 Fuel properties of biomass Proximate analysis of a biomass fuel sample involves the determination of its moisture, volatile matter, ash and fixed carbon content, all as percentage of its original weight The term "fixed carbon" is hypothetical and does not imply the existence of uncombined carbon in the biomass substance, nor does it represent the total carbon as determined from an ultimate analysis This quantity Is not determined experimentally, but is calculated as the sum of the percentages of moisture, volatile matter and ash subtracted from IOO The proximate analysis and ultimate analysis of samples were shown in table It could be said that the moisture (diy basic) is around 12-15% [1] and it will significantly affect the UHV (useful heating value) of the samples It could be said that Ihe water content of a biomass fuel has to be evaporated first before heat is available for Its end application The higher the moisture content, Ihe lower is the useful energy available Three samples have high volatile, however the sawdust has a highest value and contains very small amount of ash The ash of rice straw and rice husk are about 12-14% The wood materials tend to be low in ash content while the agricultural materials can have high ash contents The fixed-carbon of samples is in a range of 15-19%, Based on the proximately aii.iij it •'"lid be said that the volatile matter is the most importanl paramcicr of sh - Y" The utility of their volatile matter will responsible for their application In industries Ultimate analysis is the chemical analysis of materia] It involves the determination of the more iiiip.iit.iiu Lli.:iiii a! jl-r.iciiis in a biomass fuel, which are usually carbon (C), hydrogen (H) The percentage of oxygen is normally not delermined directiy but calculated as the sum of Ihe above elements plus moisture and ash subtracted from 100, The percentages carbon, hydrogen and oxygen of the samples also mentioned in table The carbon content of samples is in a range 33-48%, while the hydrogen content is around 2,7-5.3% The composition of the ash of Ihe rice husk, rice straw and sawdust shows their differences The main compositions of rice husk are SiO CaO and K,0 and AhOj FcjO,, MgO just appearance with small amount The content of SiO^ significantly holds 91.86% mass of rice husk For rice straw, the composition of SiOj, CaO and K2O were also the main ingredient however their proportion was difference with rice husk The potassium of straw was 15,68% and this value is very high and directly related to the corrosion, ash deposition and fusion temperature of the ash JOURNAL OF SCIENCE & TECHNOLOGY * No 87-2012 For the sawdust sample, the SiOj content is smaller Ihan of above samples, and the content of CaO and MgO is approximately 40.9% of the ash and it is high compared with those of agricultural residues It is about 18% mass of ash are unidentified The ash content of sawdust has a major impact on the trouble-free operation of a biomass gasifier or combustor It has long been recognized that the most troublesome components of the ash are SiOi and the alkalis The danger lies not only in their influence to lower the fusion temperature of the ash but in their vaporization at temperatures prevailing inside a biomass gasifies/combuslor and the subsequent deposition on cold surfaces Table Some fuel properties of biomass Characteristics Proximate analysis Moisture (%-ad) Volaffle matter* (%) Ash*(%) Fixed carbon* (%) Ultimate analysis Carbon • (%) Hydrogen* (%) Oxygen * (%) Ash (%mass) • SiO, A1,0, FEiO, CaO MgO NajO K2O • Other HHV (MJ/kg) Rice husk Rice straw Sawdust 12.2 67.38 13.46 19.16 13.4 69.60 12.05 18.35 15.3 82.98 1.52 15.50 40.53 2.71 43.30 33.13 4.92 49.90 47.67 5.31 45.50 91.86 0.25 0.91 3.13 0.12 0.29 1.54 1.90 15 87 71.26 0.67 0.89 7.05 1.46 0.98 15.62 2.07 15.72 29.24 2.54 3.99 36.54 4.39 1.63 3.77 17.90 19.45 * Dry basic Higher heating value, HHV, (or gross calorific value) is defined as the number of heal units evolved from complete combustion of a unit mass (or volume) of fuel, including the sensible heat and the latent heat of condensation of the water produced during combustion when the products of combustion are cooled to 25"C Based on the HHV of the fuel, LHV and UHV are calculated and they are most important characteristics of biomass The HHV of biomass samples are shown in table It could be said that the HHV of rice husk and straw are similar to each others The woody biomass has higher HHV compared to those of agricultural residues Because the sawdust contains small amount of the ash in comparison to the agricultural residues and the carbon composition was higher therefore it own higher HHV Biomass generally has less carbon, more oxygen, more silica and potassium, less aluminum and iron, low heating value, high moisture content, and low density and fiiability The high moisture and ash contents in biomass fuels can cause ignition and combustion problems The melting point of the dissolved ash can also low which causes fouling and slagging problems 3.2 Thermal behavior of biomass The dynamic results for thermal analysis of samples are shown in figure 1,2,3 The right vertical axis is the weight loss of samples during analysis process (TG), Ihe left vertical axis is a thermal signal (DSC) of the reaction, the other curve is the DTG line The horizontal axis is the temperature of the oven during analysis It is evident that the weight loss curve is similar to each other's and clearly observed that there are two overlapping reaction zones (DSC signal) take place between 200-500°C for all samples Thus, the thermal degradation characteristics and parameters of the two overlapping reaction zones were investigated separately Increasing the temperature from ambient to about 200"C results in weight loss of water, which presented in the samples and external water bounded by the surface tension This physical phenomenon was required heat and the first endothermic pick cause by this The detail data of the water loss during analysis process are mentioned in table The initial decomposition temperature of samples started around 200°C whereas the final temperature for the first reaction zone were 360''C for rice husk and rice straw and 400^ for saw dust The total degradation of the first reaction zone was 53.89% 46.17% and 49.82% for straw, rice husk and sawdust The results of the initial JOURNAL OP SCIENCE & TECHNOLOGY * No 87 - 2012 thermal decomposition were presented in table The end of the first decomposition zone was accepted as the beginning of the second reaction /.one and this was defined by DTG line The final temperature of the second decomposition zone was around SOOT The degradation of the second zone was 27.27%, 34.17% and 34.93% for straw, rice husk and sawdust respectively There is no weight loss after the second zone and It means that the Ihermal degradation of samples is completed The residual weights of the samples were recorded and were 14.64% 12.36% for straw, rice husk and neariy 0% for sawdust respectively These values were close to the initial ash contents of the frcsh samples therefore we observed the endothcntnic peak This peak was neglected during discussion Generally speaking, the weight toss of water ts observed by TO, this is an endothcnmic reaction end should be appeared in DSC curve As explained caused by the error during measurement of this process therefore there is an overlap of (his phenomenon Fig TG-DTG-DSC results of the soH'dust analysis Fig I TG'OTG-DSC re.\ults of the straw analyst Fig TG-DTG-DSC results of ihe rice husk lllllll] \i\ The firsi endothermic peak is around 41)"t' This is an error for the measurement of the equipment (!iir\ni; starting analysis From the Btarl up procedure, the oven temperature is rather difficult to control isothermal condition The first exothermic peak of straw and rice husk is al ^ and 333"C and it fit in range of the release of volatile of biomass It is well accepted that the biomass pyrolysis required energy and il is an endothermic reaclion However there was an exothermic peak in the DSC ciir\c in this temperature range In the air investigation atmosphere, perhaps the combustion of volatile was occurred The combustion of the volatile was the strong exothermic reaction and caused by the exothermic signal for Ihe first decomposition period The second exothermic peak occurred at 46rC and 4()2"C- These results implied lo Ihe second biomass decomposition After release of the volatile of biomass, the samples converted into char The char of the biomass is \cr\ active and at that tcmperalure range in Ihe air environment, the exolhermic combustion reaction of the char was occurred For the case of sawdust samples, the DSC signal is more complicated than two about explanation Beside the dr\ing range, there are two endothermic peaks and two exothermic peaks Two exothermic peaks are similar to the above samples and there are combustion of volatile and char Both endothermic reactions simultaneously with the mass loss could be JOIHNAL OF SCIKNCE & TECHNOLOGY * No 87 - 2012 understood for the decomposition of biomass Perhaps the Ihermal degradation characteristics of biomass are strongly influenced by their chemical composition (cellulose, hemicellulose and lignin content) Sawdust is Ihe hard wood, it owns Ihe ordered and large polymer structure therefore its physical structure arc difference from Ihe straw and husk The endothermic phenomenon at that range could be explained by ihe decomposition of polymer structure of cellulose [6] Table The data of the samples analysis process during Parameter Sawdust Dryin.q l("C) Water loss First decomposition t("C) Mass loss Second decomposition t(°CI Mass loss Ash Rice husk Rice straw I6U 4.2 160 6.9 161) 13.02 287 53.89 312 46.17 337 49.82 456 27.27 14.64 462 34.17 12 36 476 34.93 a typical characterization of biomass The moisture is around 12-15%, high volatile and low HHV, The ash of sawdust is much lower than of rice husk and straw, however they contain silica and alkaline and these will impact on the softening point of the ash during combustion or gasification The ultimate analysis of biomass identified their main composition is carbon and oxygen and around 3-5% hydrogen Three,samples showed similar behavior during TG-DSC analysis Three typical zone appeared during invesligalion are drying pyrolysis and combustion of char The drying zone occurred below 200°C The mass loss in the second period executed in the 200"C-400'*C range and it, was a release of volatile The last zone carried out in 400-500°C range and implied to the char combustion The remained quantities of the samples after analysis was ash content of biomass The typical results of biomass fuel properties are very valuable for the engineers, who will design the combustion, gasification or pyrolysis system for the following research * l('C) was defined in DTG line Ac kn ow ledgm ent CONCLUSIONS This study is part of the research project on "Developing a small scale biomass gasification system" which is funded by Ministry of Science and Technologj' of Vielnam Vielnam has a potential of biomass resources that are residues of agricultural products (rice husk, straw) and the waste of wood processing industry (sawdust) They own REFERENCES Shinya Vokoyama The Asian Biomass Handbook The Japan Institute of Energy 2008 Pham Hoang Luong Promoting biomass fuels based technologies for energy production in Vietnam; The 20"* scientific conference of Hanoi University of Technology, p49-54.2006 Pham Hoang Luong, Pham Van Tan, Bui Thanh Hung Van Dinh Son Tho Bui Quoc Khanh, Renewable energy resources and technology in Vietnam-an overview The A S L A \ C O S r - New Energy Forum for Sustainable Environment May 25-27 2008 Kyoto Japan Van Dinh Son Tho, Using DSC analysis for investigation the combustion and pyrolysis of Vietnamese coal: The 20''' scientific conference of Hanoi University of Technology 55-59 20(.iCi Micheal E Brown The introduction to thermal analysis lechniques and applications, Kiuuer academic publisher Second edition 2001 T.B Reed, Biomass gasification principle and Technology Solar Energy Research Inslituie \ o y e s Data corporation Park Ridge New Jersey USA 1981 Aiiiiior's address- Van Dinh Son Tho-Tel.(-84)973604372.Hmail-thovds-pcirochcmr^huail.hut,cdu-\'ii Hanoi University of Science and Technology No.l Dai Co Vict Sti Ha \ o i Vict \aiii 51