Bioresource Technology 102 (2011) 10124–10130

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Bioresource Technology

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Nitrogen conversion under rapid pyrolysis of two types of aquatic biomassand corresponding blends with coal

Shuai Yuan, Xue-li Chen, Wei-feng Li ⇑, Hai-feng Liu, Fu-chen WangKey Laboratory of Coal Gasification of Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

a r t i c l e i n f o

Article history:Received 2 June 2011Received in revised form 9 August 2011Accepted 10 August 2011Available online 18 August 2011

Keywords:Co-pyrolysisBlue-green algaeWater hyacinthCoalNitrogen

0960-8524/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.biortech.2011.08.047

⇑ Corresponding author. Tel.: +86 21 64251418.E-mail address: liweif@ecust.edu.cn (W.-f. Li).

a b s t r a c t

Rapid pyrolysis of two types of aquatic biomass (blue-green algae and water hyacinth), and their blendswith two coals (bituminous and anthracite) was carried out in a high-frequency furnace. Nitrogen con-versions during rapid pyrolysis of the two biomass and the interactions between the biomass and coalson nitrogen conversions were investigated. Results show that little nitrogen retained in char after the bio-mass pyrolysis, and NH3 yields were higher than HCN. During co-pyrolysis of biomass and coal, interac-tions between biomass and coal decreased char-N yields and increased volatile-N yields, but the totalyields of NH3 + HCN in volatile-N were decreased in which HCN formations were decreased consistently,while NH3 formations were only decreased in the high-temperature range but promoted in the low-tem-perature range. Interactions between blue-green algae and coals are stronger than those between waterhyacinth and coal, and interactions between biomass and bituminous are stronger than those betweenbiomass and anthracite.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction higher than those in coal (Abraham and Muraleedhara, 1997; Li

Industrialization leads to Lake Eutrophication in many countries.In China, more than 66% of the lakes and reservoirs are eutrophic,among which 22% are highly eutrophic (Huang, 2001), resulting inextensive reproductions of blue-green algae and water hyacinth.Blue-green algae which contain large amount of heavy metals andtoxins rots rapidly, thus serious pollutions can be caused to waterand ecological environment (Falconer, 1999). The extremely fastreproduction of water hyacinth usually leads to blocks of water traf-fics. Salvage is a direct and rapid method to control the spread ofblue-green algae and water hyacinth, and secondary destructionsand pollutions on ecological environment can be avoided. However,further toxicant-free treatment process is energy consuming sincethe salvaged blue-green algae and water hyacinth contain highmoisture contents (>90%) (Li et al., 2009). It has been reported that,high quality slurry for gasification can be obtained by blending thehigh moisture blue-green algae with coal (Li et al., 2009). Therefore,incorporating the blue-green algae and water hyacinth as parts offuel for gasification process might be an economical method forblue-green algae and water hyacinth treatment.

During gasification, nitrogen pollutants such as NH3 and HCNcould be accumulated, which not only affect the gasification sys-tem operation over time, but also increase the difficulty of sewagetreatment (Chen et al., 2009). Nitrogen contents and their corre-sponding reactivity in blue-green algae and water hyacinth are

ll rights reserved.

et al., 2009). Therefore, nitrogen conversions during gasificationof blue-green algae and water hyacinth should be concerned.

Rapid pyrolysis is not only an important process of combustionand gasification, but also a biomass thermal conversion method.Nitrogen distribution in products of rapid pyrolysis is an importantimpact factor for the subsequent nitrogen conversions and the finalnitrogen products during combustion and gasification. Great effortshave been made by researchers to study nitrogen conversions dur-ing rapid pyrolysis of coal and biomass. However, scarce researcheson nitrogen conversion during rapid pyrolysis of aquatic biomasssuch as blue-green algae and water hyacinth have been reportedat present. Further more, interactions (synergies) between biomassand coal, such as the decrease of char and tar yields and the increaseof gas phase products, have been found during pyrolysis of biomass/coal blends (Haykiri-Acma and Yaman, 2010; Park et al., 2010;Vuthaluru, 2004; Zhu et al., 2008). Cordero and co-workers foundthat, desulphurization was enhanced during pyrolysis of biomassand high-sulfur coal blends (Cordero et al., 2004). The reason forpromotion of biomass on coal conversion during pyrolysis of bio-mass/coal blends may be that, biomass can release abundant Hand OH radicals which can promote the cracking of coal heterocy-cles (Blesa et al., 2003; Sonobe et al., 2008). In addition, alkali min-erals in biomass have catalytic effects on char and volatileconversions to gaseous products during co-pyrolysis of biomassand coal (Keown et al., 2008). Nitrogen conversions during pyroly-sis of biomass/coal blends may be different from nitrogen conver-sions during pyrolysis of biomass and coal individually. However,effect of co-pyrolysis of biomass and coal on nitrogen evolution

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Ar

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Fig. 1. High frequency furnace rapid pyrolysis system. (1-Ar cylinder; 2-flowmeter;3-high frequency current source; 4-quartz tube reactor; 5-induction coil; 6-Mo-crucible; 7-thermocouple and meter; 8-filter; 9-absorption bottles; 10-bubblestones).

S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130 10125

has rarely been studied at present. Most of the nitrogen in biomassis bonded in protein as the form of amino-N mainly, nitrogenbonded in heterocyclic-N is low (Ye et al., 2007). As amino-N canbe easily released during rapid pyrolysis to form NHi radicals whichcan be further combined with H to form NH3, and heterocyclic-N isthe main source of HCN (Hansson et al., 2003a,b), yields of NH3

should be higher than yields of HCN during rapid pyrolysis of pro-tein. In our prior study where soybean cake (mainly proteins andsaccharides) as a model compound of proteins has been pyrolyzed,yields of NH3 were also found much higher than the yields of HCN(Yuan et al., 2010). However, during rapid pyrolysis of herbaceousbiomass (rice straw), the not easily collapsed ‘‘microshells’’ con-sisted of lignin in rice straw led to the polymerization reactions be-tween proteins and lignin, cellulose, and hemicellulose in theprimary stage of pyrolysis. The cracking of heterocyclic-N formedthrough the polymerization reactions, led to higher HCN yields thanNH3 yields (Yuan et al., 2010). The purpose of this study is to probeinto nitrogen conversions during rapid pyrolysis of aquatic biomass(blue-green algae and water hyacinth) whose structure and nitro-gen contents are very different from those of the typical agricultureand forestry biomass, and to ascertain whether co-pyrolysis of bio-mass and coal has any effect on nitrogen evolution.

Fluidized-bed reactor and entrained-bed reactor (also calleddrop-tube furnace or free fall reactor) are the mostly used reactorsfor rapid pyrolysis. During rapid pyrolysis in the fluidized-bedreactor and entrained-bed reactor, volatiles released from the fuelsamples must go through the long high-temperature zone, there-fore secondary reactions can not be prevented. Microwave heatingis a powerful method to carry out rapid pyrolysis without second-ary reactions (Chen et al., 2008; Huang et al., 2010; Menéndezet al., 2002; Miura et al., 2004; Salema and Ani, 2011). Wire meshreactor (WMR) has also been used for rapid pyrolysis without sec-ondary reactions (Lim et al., 1997; Liu and Niksa, 2004). In thisstudy, a high-frequency furnace which could also restrain second-ary reactions of primary pyrolysis products was employed to carryout rapid pyrolysis experiments, and therefore the uncertainties ofnitrogen products caused by secondary reactions can be avoided.

2. Experimental

2.1. Fuel samples

Blue-green algae are mixtures of different algae, mainly includepseudanabaen, limnothrix, microcyst, and dactylococcopsis, and infact they are bacteria (Richmond et al., 1989). Water hyacinth is anadvanced plant. Elemental analysis and proximate analysis of blue-green algae (BGA) and water hyacinth (WH) are listed in Table 1. Asseen in Table 1, nitrogen contents in organic components of thetwo fuel samples are higher than those of biomass such as ricestraw, chinar leaves, and pine sawdust (Yuan et al., 2010), espe-cially for blue-green algae which has a nitrogen content higherthan 7%. Particles sizes of the samples were chosen to be in therange of 90–180 lm.

All the fuel samples were dried before experiments. Blue-greenalgae (BGA) and water hyacinth (WH) were blended with bitumi-nous (B) and anthracite (A), respectively with a mass ratio of 1:9(dry basis). Elemental analysis, proximate analysis, and particle

Table 1Proximate analysis (dry basis, wt.%) and elemental analysis (daf, wt.%) of blue-green algae

Samples Proximate analysis (wt.%, d)

A V FC

Blue-green algae 18.69 71.98 9.33Water hyacinth 39.90 51.02 9.08

A: ash content; V: volatile matter; FC: fixed carbon.

sizes of the bituminous and anthracite have been reportedelsewhere (Yuan et al., 2011). The four kinds of blends were as thefollows: blue-green algae + bituminous (BGA + B), blue-green algae+ anthracite (BGA + A), water hyacinth + bituminous (WH + B), andwater hyacinth + anthracite (WH + A). Moreover, co-pyrolysis ofthe biomass components (lignin, cellulose, and hemicellulose) withbituminous (1:9, wt) was also carried out to investigate their effectson nitrogen evolution.

2.2. Pyrolysis setup

A high-frequency furnace as shown in Fig. 1 was used to carryout rapid pyrolysis of the fuel samples at 600–1200 �C. Molybde-num crucible placed in the quartz reactor was heated by thehigh-frequency alternating magnetic field generated by the induc-tion coil connected to the high-frequency power supply unit. Thetemperature was monitored by an S-type thermocouple insertedinto the hole drilled in the bottom of the crucible, and the finaltemperature of the crucible was controlled by the current fromthe power supply unit. Fuel samples (0.3 g each experiment) wereinjected from the top of the reactor through a feeding tube to thecrucible. Rapid pyrolysis was initiated when fuel samples camein contact with the surface of crucible. As the crucible could beheated by the high-frequency alternating magnetic field, but thequartz tube reactor could not be heated by the magnetic field,the high-temperature zone was limited just in the crucible and asmall zone around. Therefore, gas products released from the cru-cible could be carried away from the high-temperature zone andbe rapidly quenched, and secondary reactions can be restrained.The sample feeding time was 2 min each time, and the power sup-ply unit was shut down after 2 min when the injection of fuel sam-ples was finished. More details of the operating conditions havebeen described elsewhere (Yuan et al., 2010, 2011).

2.3. Quantification method

Pyrolysis gas released from the reactor was introduced into theadsorption bottles, NH3 and HCN in pyrolysis gas were adsorbed byHNO3 solution and NaOH solution, respectively. Parallel experi-ments were carried out to adsorb NH3 and HCN separately undereach condition. NHþ4 and CN� concentrations in the solutions were

and water hyacinth.

Ultimate analysis (wt.%, daf)

C H N S O

55.25 5.24 7.10 1.34 31.0747.72 2.25 3.59 0.80 45.64

10126 S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130

detected by Metrohm-861 ion chromatograph. Separating columnsare C 4-100 for anion and Supp 1-250 for cation. Solid product(char) in crucible was collected and weighted after each experi-ment, nitrogen contents in char were analyzed by an industrialanalyzer (5E-MAG6700) and an element analyzer (Vario MACROCHN/CHNS). Parallel experiments were carried out in each condi-tion to ensure the relative standard deviations were lower than5%. More details have also been reported elsewhere (Yuan et al.,2010, 2011).

3. Results and discussion

3.1. Nitrogen conversion under rapid pyrolysis of blue-green algae andwater hyacinth

Yields of NH3 and HCN during rapid pyrolysis of blue-green al-gae and water hyacinth under different temperatures are shown inFig. 2. HNCO may be formed during pyrolysis of coal and biomass,which can be converted to NH3/NHþ4 during wet adsorption meth-od (Ledesma et al., 1998). However, abundant of H radicals, OHradicals, as well as H2O can be formed during pyrolysis of biomass(Predel and Kaminsky, 1998), as HNCO can be converted to NH3 byreacting with H radicals, OH radicals, and H2O (Ma et al., 1997; Shiet al., 1999), conversion of HNCO to NH3 should has been alreadystarted far before HNCO reaches to the adsorption bottle. More-over, some researchers believe that attributions of HNCO to NH3/NHþ4 are very low especially under the rapid pyrolysis conditions(Hansson et al., 2003b). In this study, only total NH3 (directly orvia HNCO) is discussed.

According to the results of Fig. 2, NH3 is the main nitrogen pol-lutant during rapid pyrolysis of blue-green algae, and yields of HCNare much lower than NH3. It has been confirmed that, organic com-ponents of blue-green algae are mainly proteins and saccharides.The content of proteins in blue-green algae is about ±60% (daf).The saccharides are mainly pectin and a low portion of hemicellu-lose (Richmond et al., 1989). As amino-N which can be easily con-verted to NH3 (Hansson et al., 2003a,b) is the main nitrogen form inprotein, the yields of NH3 should be higher than the yields of HCNduring rapid pyrolysis of blue-green algae. This result is consistentwith the result of the prior study where soybean cake as a proteinmodel compound was pyrolyzed (Yuan et al., 2010).

During rapid pyrolysis of water hyacinth which is an herbaceousbiomass, NH3 yields are found higher than HCN yields. But in ourprior study, HCN yields are higher than NH3 yields during rapid

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18 HCN NH3

Temperature,

Nitr

ogen

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vers

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CN

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NH

3, m

ol %

a b

Fig. 2. Yields of NH3 and HCN from BGA(a) and

pyrolysis of rice straw which is also an herbaceous biomass (ricestraw). The reason was that, the not easily collapsed ‘‘microshells’’consisted of lignin in rice straw led to the polymerization reactionsbetween proteins and lignin, cellulose, and hemicellulose in the pri-mary stage of pyrolysis, and the heterocyclic-N formed through thepolymerization reactions led to higher HCN yields than NH3 yields(Yuan et al., 2010). The organic compositions (daf) of water hyacinthare lignin (5.8%), cellulose (44.4%), hemicellulose (23.1%), proteins(14.1%), fat (10.1%), starch (2.4%), and gloea (0.1%) (Abraham andMuraleedhara, 1997). From the comparison between the organiccomparisons of water hyacinth and rice straw, lignin content inwater hyacinth can be found lower than that of rice straw (Yuan etal., 2010). Moreover, structure of water hyacinth presents abundantlarge cavities and bubbles with thin walls (University of Hawaii atManoa Botany, 2011), this is also different to the rice straw whichhas rich microporous structures (Xiao, 2010). Therefore during rapidpyrolysis of water hyacinth, the large cavities which have thin wallsmight be easily destructed, proteins in the cells can be directlydecomposed without serious polymerizations, and NHi can be re-leased easily, and then be converted to NH3 mainly.

As it could be seen in Fig. 2, as the pyrolysis temperature in-creases, yields of HCN decrease gradually, while yields of NH3

increase initially and then decrease gradually during rapid pyrolysisof both blue-green algae and water hyacinth. The reason might bethat, volatiles release slowly from the particles under the low-tem-perature conditions, which leads to some polymerizations of vola-tiles in the particles (Park et al., 2010). As heterocyclic-N formedthrough the polymerization reactions is the main source of HCN(Hansson et al., 2003a,b; Yuan et al., 2010), yields of HCN shouldbe higher under the low-temperature conditions. As the tempera-ture increases, volatiles release more rapidly, and less polymeriza-tion reactions happen, therefore less heterocyclic-N formed, andless HCN released. However, polymerization reactions happenedunder the low-temperature conditions are unfavorable to the for-mation of NH3. As temperature increases, less polymerization reac-tions happen and more volatile-N (mainly NH3 except for tar-N andN2) releases. But when the temperature is high enough, more pro-teins may be decomposed completely to form N2, and yields ofNH3 also decrease.

Tar yields during rapid pyrolysis of biomass at the temperaturehigher than 600 �C are low (Klass, 1991). As a small quantity of fuelsample was pyrolyzed each time, and part of the tar was con-densed in the inner wall of the upper part of the reactor, it was dif-ficult to collect the tar and make accurate quantification of tar-N.N2 in air may also result in errors on detection of N2 in pyrolysis

Temperature, 600 700 800 900 1000 1100 1200

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WH(b) at different pyrolysis temperatures.

S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130 10127

gas. Therefore, sums of N2-N and tar-N (N2 + tar-N) were calculatedby subtraction method. Fig. 3 shows nitrogen distributions in prod-ucts (char-N, NH3 + HCN, and N2 + tar-N) during rapid pyrolysis ofblue-green algae and water hyacinth under different temperatures.

According to the results in Fig. 3, most of the fuel-N was con-verted to N2 + tar-N. Yields of N2 + tar-N from blue-green algaeare higher than those of water hyacinth, while char-N yields of

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Fig. 3. Effect of pyrolysis temperature on distributio

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100 Char-N(experimental) Char-N(calculated) HCN+NH3(experimental) HCN+NH3(calculated) N2+tar-N(experimental) N2+tar-N(calculated)

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Fig. 4. Nitrogen distribution in products under rapid pyrolys

water hyacinth are higher than those of blue-green algae. This alsoproves that polymerization reactions caused by lignin in waterhyacinth may restrain the release of nitrogen from the fuelsamples.

As the pyrolysis temperature increases, char-N yields decreasegradually, about 15% of fuel-N was retained in char after pyrolysisof water hyacinth at 1200 �C, while just lower than 5% of fuel-N

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n of the nitrogen products: BGA(a) and WH(b).

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Temperature,

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is of BGA + B(a), BGA + A(b), WH + B(c), and WH + A(d).

10128 S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130

was retained in char after pyrolysis of blue-green algae at 1200 �C.Yields of NH3 + HCN decrease and yields of N2 + tar-N increase withthe increasing temperature when the temperature is higher than700 �C. Although tar-N was not quantified in this study, tar yieldsunder high-temperature conditions were qualitatively observedlower than tar yields under low-temperature conditions, therefore,tar-N yields should decrease, and N2 yields should increase withthe increasing temperature. It can be deduced that the increasingtemperature (>700 �C) can decrease the yields of NH3 and HCN,and promotes nitrogen conversion to harmless N2 during rapidpyrolysis.

For the conditions of 600 �C, although yields of gaseous productsare higher than those of at 700 �C, yields of NH3 + HCN are lower. Thereason may be that more tar-N was formed during rapid pyrolysis ofblue-green algae and water hyacinth at 600 �C and tar-N may attri-bute a higher proportion in N2 + tar-N.

3.2. Nitrogen conversion under rapid pyrolysis of blue-green algae/coaland water hyacinth/coal blends

Nitrogen distributions in pyrolysis products under rapid pyroly-sis of the bituminous and anthracite have been reported elsewhere(Yuan et al., 2011). Comparisons of experimental and weighted val-ues of nitrogen distributions in pyrolysis products during rapidpyrolysis of BGA + B, BGA + A, WH + B, and WH + A are shown inFig. 4. The weighted values were calculated according to the mass

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Fig. 5. Nitrogen conversion to NH3 and HCN under rapid pyro

proportions and nitrogen distributions during rapid pyrolysis ofbiomass and coal individually, the function is as the follows: N-yieldblend = N-yieldbiomass � 0.1 + N-yieldcoal � 0.9. As seen in Fig 4,experimental char-N yields are lower than the weighted valuesin most of the conditions. It indicates that co-pyrolysis of the bio-mass and coals can make more fuel-N convert to volatile-N. Exper-imental HCN + NH3 yields are lower than the weighted values inmost of the conditions, but experimental N2 + tar-N yields are high-er than the weighted values. In other words, although more vola-tile-N can be formed during rapid pyrolysis of BGA/coal and WH/coal blends, HCN + NH3 in volatile-N becomes lower.

By comparing the results of the blends of the two coals blendingwith same biomass, interactions between biomass and bituminousare more obvious than the interactions between biomass andanthracite. In the study of Haykiri-Acma, synergies between bio-mass and low-rank coal were also found weaker than the synergiesbetween biomass and high-rank coal during co-pyrolysis of bio-mass and coal. They considered that the higher structure similaritybetween biomass and low-rank coal than that between biomassand high rank coal was the reason (Haykiri-Acma and Yaman,2010).

By comparing the results of the two biomass with the samecoal, it could be seen that the interactions between blue-green al-gae and coal are more obvious than the interactions between waterhiyacinth and coal. According to the results shown in Table 1 that,blue-green algae has a higher V/FC ratio, yields of volatile-N of

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lysis of BGA + B(a), BGA + A(b), WH + B(c), and BGA + A(d).

S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130 10129

blue-green algae can also be found to be higher than those of waterhyacinth (Fig. 2). It can be deduced that, blue-green algae has ahigher reactivity than water hyacinth, which leads to the higherpromotion on coal-N conversion.

Comparisons of experimental and weighted values of NH3

yields and HCN yields during rapid pyrolysis of BGA + B, BGA + A,WH + B, and WH + A are also shown in Fig. 5. As seen in Fig. 5,experimental HCN yields are lower than the weighted value inmost of the conditions. The reason may be that, abundant OH rad-icals with a strong oxidizability can be released from blue-green al-gae and water hyacinth during rapid pyrolysis, therefore the HCNyield from coal would be decreased.

It can also be found that, during rapid pyrolysis of BGA/coalblends, experimental NH3 yields are lower than the weighted valuein the high-temperature range, but experimental NH3 yields areobviously higher than the weighted value in the low-temperaturerange. Similar trends can be found during rapid pyrolysis of WH/coal blends, but the experimental NH3 yields are not obviouslyhigher than the weighted NH3 yields in the low-temperature range.

During pyrolysis of biomass/coal blends, heat transfer rates aredecreased, leading to the decreased heating rates of the fuel parti-cles (Park et al., 2010). The decrease of heating rate should be moreevident in the low-temperature conditions where contact heattransfer plays a much more important role than radiation heattransfer. As blue-green algae has no lignin and lignin content inwater hyacinth is very low, scarce polymerization reactions

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Fig. 6. Effects of lignin, cellulose, and hemicellulose on th

between proteins and the other contents of biomass (lignin, cellu-lose, and hemicellulose) should happen (Ren et al., 2011; Yuan etal., 2010). Therefore the formation of heterocyclic nitrogen leadingto the formation of HCN also should not be enhanced (Hanssonet al., 2003a,b; Yuan et al., 2010). Park and co-workers consideredthat, the increasing release time of volatile could increase the sec-ondary decompositions of volatiles during co-pyrolysis of biomassand coal (Park et al., 2010). In the low-temperature condition, moreheterocyclic nitrogen in the slowly released volatile can be thor-oughly decomposed, more NHi radicals can be released, and theabundant H radicals provide essential condition for the conversionof NHi to NH3.

Effects of the biomass components (lignin, cellulose, and hemi-cellulose) on the yields of char-N, NH3, and HCN during co-pyroly-sis of the biomass components with coal are shown in Fig. 6. It canbe found that hemicellulose decreases char-N yields under all thetemperatures. Lignin and cellulose decrease char-N yields in thehigh-temperature range. But in the low-temperature range, char-N yields are increased by lignin and cellulose, and lignin has astronger effect on the increase of char-N yields than cellulose.HCN yields are seriously decreased during co-pyrolysis of all thethree biomass components with bituminous under all the temper-atures. NH3 yields are also restrained by cellulose and hemicellu-lose under all the temperatures. But NH3 yields are increasedduring co-pyrolysis of bituminous and lignin under the low-tem-perature range. It can be concluded that, hemicellulose owns the

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B+Hem-NH3

B-HCN B+Hem-HCN

e yields of char-N, NH3, and HCN from bituminous.

10130 S. Yuan et al. / Bioresource Technology 102 (2011) 10124–10130

strongest promotion effect on the coal conversion during co-pyro-lysis. Lignin in biomass which plays as a role of ‘‘binder’’ to agglu-tinate the cellulose and to ensure the mechanical strength of thecell wall, may cause some polymerizing reactions in the low-tem-perature range, and lead to the increase of NH3 yields. The specificinteraction mechanisms of the lignin, cellulose, and hemicellulosewith coal during co-pyrolysis should be further studied.

4. Conclusions

Char-N yields are low after pyrolysis of BGA and WH. High pro-tein in BGA and low lignin and abundant cavities with thin walls inWH make more NH3 released than HCN. The increasing tempera-ture decreases NH3 + HCN yields and promotes fuel-N conversionto N2. Interactions between biomass and coal during co-pyrolysispromote fuel-N conversion to volatile-N, but decrease HCN + NH3

yields. Interactions between biomass and coal restrain HCN yields.NH3 yields are restrained at high temperature, but promoted bythe decreased heating rates at low temperature. Higher biomassreactivity and similarity between biomass and coal enhance theinteractions between biomass and coal.

Acknowledgements

This study was financially supported by National Natural Sci-ence Foundation of China (20906024), and New Century ExcellentTalents in University (NCET-08-0775) by Ministry of Education ofChina. The authors also acknowledge Prof. Ji Yang (School of Re-source and Environmental Engineering, ECUST) for his help onlanguage.

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