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Journal of Analytical and Applied Pyrolysis 98 (2012) 242–246

Contents lists available at SciVerse ScienceDirect

Journal of Analytical and Applied Pyrolysis

journa l h o me page: www.elsev ier .com/ locate / jaap

omposition of the liquid product by pyrolysis of dried distiller’s grainsith solubles

e Wang, Peng Ren, Weigang Lin, Wenli Song ∗

tate Key Laboratory of Multi-Phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

r t i c l e i n f o

rticle history:eceived 16 July 2012ccepted 17 September 2012vailable online 25 September 2012

eywords:

a b s t r a c t

Presently, dried distiller’s grains with solubles (DDGS) are mainly used as the livestock feed. However, thehigh fiber content in DDGS limits its use as the diet for animals. Therefore, with increasing productionof DDGS in recent years, it is desirable to find some new uses of DDGS for fuels and/or for high valuechemicals. In this paper, experiments on pyrolysis of DDGS by spouted-entrained bed and by fixed bedare carried out, and the pyrolytic liquids are analyzed by GC/MS. It was found that the composition of the

◦

ried distiller’s grains with solubles (DDGS)yrolysisiquid productomposition

liquid by pyrolysis of DDGS in 490–570 C by spouted-entrained bed is rather complex, and varies withpyrolytic temperature. However, the pyrolysis of DDGS material is not quite suitable to the process byspouted-entrained bed, due to a severe clogging problem inside the reactor. By fixed bed, the compositionof the oil phase of the liquid obtained in 490–610 ◦C is much simpler, mainly phenol derivatives, fatty acidsand their esters. When pyrolyzed at 570 ◦C with catalyst of CaO, aliphatic and aromatic hydrocarbons aregenerated more, while fatty acids and their esters are much reduced.

. Introduction

Dried distiller’s grains with solubles (DDGS) is a byproduct ofiquor production in distillery industries. Currently, DDGS is mainlysed as the livestock feed due to its high protein content [1–3].owever, the high fiber content in DDGS limits its use as the diets

or animals for possible health problems. Therefore, with increasingroduction of DDGS in recent years, it is desirable to find some newses of DDGS for fuels and/or for high value chemicals [4–8].

Tavasoli et al. [4] studied the gasification of DDGS through aontinuous downflow fixed bed micro reactor. Alves et al. [5] inves-igated the synthesis of carbon nanomaterials (CNM) by catalyticonversion of DDGS, where DDGS were firstly pyrolyzed, and thenhe pyrolytic gases were further converted to CNM by chemicalapor deposition. The liquefaction of DDGS with hot compressedhenol was investigated by Xu et al. [6], and it was found thathe yield of liquid product reached the maximum at 300 ◦C for

min-operation with phenol/DDGS of 2/1. Lei et al. [7] studiedhe pyrolysis of DDGS by microwave. It was found that the liquidas mainly composed of aliphatic and aromatic hydrocarbons; the

romatic hydrocarbons were mainly composed of benzenes, phe-ols, and naphthalene; however, acetic acid, commonly believeds a main component in the lignocellulose pyrolytic liquid was not

∗ Corresponding author.E-mail addresses: wangze@home.ipe.ac.cn (Z. Wang), wlsong@home.ipe.ac.cn

W. Song).

165-2370/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.jaap.2012.09.006

© 2012 Elsevier B.V. All rights reserved.

detected therein, but butenoic acid was detected in small amount.The pyrolysis of distillers grains with solubles were conducted byWang et al. [9] using thermogravimetric analysis. It was found thatthe initial pyrolytic temperature increases with increasing heat-ing rate and initial moisture content, and the pyrolysis completesat 650 ◦C with residual weight of 27.15%. Gudka et al. [10] inves-tigated the pyrolysis of DDGS using Py–GC–MS (Pyroprobe–GasChromatography–Mass Spectrometry), and it was found that themain products are furfural derivatives, methoxyphenols, and longchain fatty acids and esters, as well as some heterocyclic aromaticslike indole and pyrrole.

In this paper, experiments on pyrolysis of DDGS by spouted-entrained bed and by fixed bed are carried out, and the pyrolytic liq-uids are analyzed by GC/MS (Gas Chromatography–Mass Spectrom-etry, Varian 3800GC–300MS, with FFAP 25 m × 0.25 mm × 0.2 �mcapillary column). The effect of temperature and the effect of CaO byfixed bed on the composition of the pyrolytic liquid are discussed.

2. Equipment and experimental method

The raw material of DDGS was obtained from Wolong-LiquorDistillery, Tianguan Group. The experimental system by spouted-entrained bed is shown in Fig. 1. The strait tubular reactor is 1 mtall, with inner diameter of 40 mm. The experimental procedure

is as follows: when the stove temperature rises to the set point,the carrier/fluidizing gas of N2 is introduced into the bed from thebottom, and then quarts sand (50 g) is dropped inside from thetop, spouting inside the reactor. After stabilized for 30 min, DDGS

Z. Wang et al. / Journal of Analytical and A

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ig. 1. Experimental system by spouted-entrained bed. 1, Carrying gas/fluidizingas (N2); 2, hopper; 3, screw feeder; 4, spouted-entrained bed; 5, stove; 6, cycloneeparator; 7, cold wall condenser; 8, water bath; 9, temperature controller.

owder is fed into the bed by screw feeder with carrier/fluidizingas. Inside the bed, the hot fluidized quarts sand collides with theassing DDGS powders sufficiently. It makes the temperature of theDGS powders rise to high temperature quickly, and thus leads to

fast pyrolysis of DDGS. The generated hemi-char and volatiles arehen quickly carried out of the bed by the carrier/fluidizing gas to

cyclone, where the hemi-char is separated and the volatiles passhrough to the condensing system. By the cold wall cooling process,he incondensable gases just pass through, and the condensed liq-ids are gathered in glass bottles. The obtained pyrolytic liquids arehen collected and analyzed by GC/MS.

The experimental system by fixed bed is shown in Fig. 2. TheDGS powder is firstly put inside a quarts basket (length of 8 cm,ith inner diameter of 1.8 cm). There is a sieve plate in the bot-

om of the basket, to support the solid sample and to make a passo the pyrolytic volatiles. When the temperature of the stove riseso the set temperature and stabilizes for 30 min, the basket with

DGS sample is put into the middle zone of the tubular quarts reac-

or (length inside the stove 70 cm, with inner diameter of 2.7 cm).he carrier gas (N2, 100 ml/min) is introduced into the tubular

ig. 2. Experimental system by fixed bed micro reactor. 1, Carrying gas/fluidizing gasN2); 2, tubular reactor; 3, quarts basket; 4, water bath; 5, temperature controller.

pplied Pyrolysis 98 (2012) 242–246 243

reactor from the top, and leaves out of the reactor from the bottom.The volatiles are carried out along with the carrier gas to the coldwall cooling system, where the volatiles are condensed to pyrolyticliquids and incondensable gases. The liquid is then analyzed byGC/MS.

The analytic method by GC/MS (Varian 3800GC/300MS withFFAP column of 25 mm × 0.25 mm × 0.2 �m) is as follows: the oventemperature starts from 40 ◦C (3 min), then increases to 100 ◦C(3 min) by 4 ◦C/min, and finally increases to 240 ◦C (10 min) by6 ◦C/min; injector temperature is 240 ◦C; ion source temperatureis 250 ◦C.

3. Results and discussion

3.1. Experiments by spouted-entrained bed

The pyrolysis of DDGS by spouted-entrained bed is conductedat three temperatures of 490 ◦C, 530 ◦C, 570 ◦C. The total ion chro-matograms (TIC) of the liquids obtained at the three temperaturesare shown in Fig. 3.

It can be seen from Fig. 3 that the component distribution of theliquid obtained by spouted-entrained bed is rather complex. Thecommon main components are some small acids (like acetic acid),polyol (like 1,3-propanediol), fatty acids and esters of the fatty acids(like n-hexadecanoic acid, and octadecadienoic acid methyl ester).Specifically, the liquid pyrolyzed at 490 ◦C is in particularly highercontent of anhydromonosaccharide, such as levoglucosan and1,4:3,6-dianhydro-�-d-glucopyranose. Levoglucosan is a widelyused high value intermediate for medicine synthesis [11]. Thepyrolysis of DDGS at 490 ◦C offers an advantage, since the highercontent of levoglucosan makes the fine concentration of levoglu-cosan more convenient. In the pyrolytic liquid obtained at highertemperature of 530 ◦C, the component of anhydromonosaccharidedecreases remarkably, and meanwhile the content of fatty acidsand their esters increases distinctly. It indicates that a conver-sion of the heat sensitive anhydromonosaccharide happens at thehigher pyrolytic temperature, and meanwhile the higher temper-ature causes the pyrolysis of DDGS deeper, and thus more heatstable compounds like phenols, and fatty acids and their esterswith higher boiling point are generated more. However, at theeven higher pyrolytic temperature of 570 ◦C, the conversions offatty acids and their esters happen as well, resulting in decreaseof their contents. Meanwhile, the content of small acids that mayderive from the conversion of fatty acids increases accordingly.The esters of fatty acids can be used as a type of fuel additivedue to its hydrophobic property. The fatty acids can be convertedto hydrocarbon fuels after deoxygenating treatment, and also canbe used as a raw material for surfactant synthesis. So, when thefatty acids and their esters are taken as the aim components inthe pyrolytic liquid for potential fuel product, the middle pyrolytictemperature of 530 ◦C is preferred by the spouted-entrainedbed.

In the above experimental process by spouted-entrained bed,a severe clogging problem is met. The feedstock of DDGS alwaysclogs inside the reactor very soon. The clogging makes the experi-ment stop unexpectedly. The experiment can hardly last for morethan 10 min, and is hard to be kept in a stable state within theshort running time. Such quick clogging never happens in the pro-cess for pyrolysis of cellulose, wheat straw, oil shale, or lignitecoal, by the same experimental equipment in our previous work.

It indicates that the pyrolytic process by spouted-entrained bedis not quite proper for the material of DDGS. So, experiments onthe pyrolysis of DDGS by fixed bed are conducted in the followingwork.

244 Z. Wang et al. / Journal of Analytical and Applied Pyrolysis 98 (2012) 242–246

lyzed

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Fig. 3. TICs of the liquids pyro

.2. Experiments by fixed bed

In each experiment, the DDGS sample used for test is about 5 g,nd the running time is about 12 min. The pyrolytic liquid obtainedy fixed bed naturally appears in two phases, oil phase and aque-us phase. The oil phases of the liquids pyrolyzed at 490 ◦C, 530 ◦C,70 ◦C, and 610 ◦C are analyzed by GC/MS. The TICs of the oil liquidsre shown in Fig. 4. It can be seen from Fig. 4 that the composi-ions of the oil liquids obtained at different temperatures are muchimpler and quite similar. The main components are just phenolerivatives, fatty acids and the esters of fatty acids. Some organicitrogen-containing compounds in low content derived from theyrolysis of protein in DDGS are identified as 3-pyridinol, 3-methyl-H-indole, and 4-methyl-pentanamide. The pyrolytic temperatureas a weak effect on the composition.

The composition of the liquid by fixed bed herein is similar inome degree but not same as the result by microwave pyrolysis ofDGS obtained by Lei et al. [7]. For instance, the components ofliphatic hydrocarbon derivatives herein are most abundant simi-arly, while the main hydrocarbon derivatives herein are not pureydrocarbons like that obtained by microwave pyrolysis, but some

atty acids and their esters; the main aromatic derivatives in theicrowave pyrolytic liquid include benzenes, phenols, and naph-

halenes, but herein benzenes and naphthalenes are much less, onlyhenols are relatively more abundant; acetic acid can be remark-bly detected in a low content herein, instead of no detection likehat in the microwave pyrolytic liquid. The differences may relateo the different raw compositions of the two DDGS materials, andlso to the different pyrolytic processes.

It can be seen from the comparison between Fig. 3 and Fig. 4 thathe effect of temperature on the composition of the liquid by fixeded is far different from that by spouted-entrained bed. The differ-nce is due to the difference of the pyrolitic process. In the process

at 490 ◦C, 530 ◦C, and 570 ◦C.

by spouted-entrained bed, the heat transfer rate is extremely high,and thus a fast pyrolysis of DDGS happens at a high temperatureclose to the set temperature. So, different set temperature causesdistinct difference in the composition of the liquid. However, in theprocess by fixed bed, the heat transfer rate from the stove hot wallto the outside of the basket is slower, even to the central samplesinside the basket. Before the sample temperature rises to the setpoint, the volatiles have been generated and have been carried outof the reaction zone. So, the set temperature has a weak influenceon the composition of the liquid.

3.3. Effect of CaO on the pyrolysis of the DDGS

Calcium oxide (CaO) is a well-known catalyst for pyrolysis ofcoal or biomass [12,13], so herein the effect of CaO on the pyrolysisof DDGS at 570 ◦C by fixed bed is investigated. The CaO powdersare laid in thickness about 1.5 cm in the downstream of the tubularreactor, supported by quarts wool. TICs of the oil phases of theliquids pyrolyzed at 570 ◦C with and without CaO are shown inFig. 5. It can be seen from Fig. 5 that in the oil liquid obtained at570 ◦C with CaO, the fatty acids and their esters are much reduced,and meanwhile the contents of phenols, aliphatic and aromatichydrocarbons are remarkably improved, compared to those bypyrolysis at 570 ◦C without catalyst. It indicates that CaO canpromote the further pyrolysis of fatty acids and their esters, and itcontributes to the increase of aliphatic hydrocarbons. It is in accor-dance to the previous reports [13,14] that acids can be convertedto hydrocarbons by catalytic cracking reaction using CaO catalyst.As to the nitrogen-containing compounds, a worth noticing point

is that the content of pyrrole and indole increases distinctly whencatalyzed by CaO. It may indicate that the more stable compoundsof pyrrole and indole can be generated more from the conver-sions of some other nitrogen-containing compounds originated

Z. Wang et al. / Journal of Analytical and Applied Pyrolysis 98 (2012) 242–246 245

Fig. 4. TICs of the oil phases of the liquids pyrolyzed at 490 ◦C, 530 ◦C, 570 ◦C, and 610 ◦C by fixed bed.

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Fig. 5. TICs of the oil phases of the liquids pyro

rom pyrolysis of protein. Compared with microwave pyrolysis,he improved contents of aliphatic and aromatic hydrocarbonsy catalysis of CaO are similar to the component distributionalharacteristics by microwave pyrolysis [7], while the even higherontent of phenols leaves further from that, and differently aceticcid still can be identified under the catalysis of CaO.

. Conclusions

The composition of the liquid by pyrolysis of DDGS at90–570 ◦C by spouted-entrained bed is complex. The com-on main components are some small acids, polyol, fatty

cids and esters of fatty acids. Specifically, the component of

with and without CaO at 570 ◦C by fixed bed.

anhydromonosaccharide is particularly abundant in the liquidpyrolyzed at 490 ◦C, and the liquid pyrolyzed at 530 ◦C is richof fatty acids and their esters. The process of spouted-entrainedbed is not quite proper for the pyrolysis of DDGS material, dueto a severe clogging problem inside the reactor. The composi-tions of the oil phase of the liquids pyrolyzed by fixed bed at490 ◦C, 530 ◦C, 570 ◦C, and 610 ◦C are much simpler and quitesimilar. The main components are just phenol derivatives, fattyacids, and esters of fatty acids. When pyrolyzed at 570 ◦C with

CaO, aliphatic and aromatic hydrocarbons are more generated, andthe content of phenols is relatively increased, while fatty acidsand their esters are much reduced, compared to that withoutCaO.

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cknowledgement

Thanks to the support by the National Natural Science Fund (No.1104137).

eferences

[1] E. Avelar, R. Jha, E. Beltranena, M. Cervantes, A. Morales, T.R. Zijlstra, The effectof feeding wheat distillers dried grain with solubles on growth performanceand nutrient digestibility in weaned pigs, Animal Feed Science and Technology160 (1–2) (2010) 73–77.

[2] M.K. Randall, D.M. Drew, Fractionation of wheat distiller’s dried grains andsolubles using sieving increases digestible nutrient content in rainbow trout,Animal Feed Science and Technology 159 (3–4) (2010) 138–142.

[3] M.K. Wood, H. Salim, L.P. McEwen, B.I. Mandell, P.S. Miller, C.K. Swanson, Theeffect of corn or sorghum dried distillers grains plus solubles on growth per-formance and carcass characteristics of cross-bred beef steers, Animal FeedScience and Technology 165 (1–2) (2011) 23–30.

[4] A. Tavasoli, G.M. Ahangari, C. Soni, K.A. Dalai, Production of hydrogen and

syngas via gasification of the corn and wheat dry distiller grains (DDGS) ina fixed-bed micro reactor, Fuel Processing Technology 90 (4) (2009) 472–482.

[5] O.J. Alves, C. Zhuo, A.Y. Levendis, A.S.J. Tenório, Catalytic conversion of wastesfrom the bioethanol production into carbon nanomaterials, Applied CatalysisB: Environmental 106 (3–4) (2011) 433–444.

[

pplied Pyrolysis 98 (2012) 242–246

[6] C. Xu, H. Su, D. Cang, Liquefaction of corn distillers dried grains with solubles(DDGS) in hot-compressed phenol, BioResources 3 (2) (2008) 363–382.

[7] H. Lei, S. Ren, W. Lu, Q. Bu, J. Julson, J. Holladay, R. Ruan, Microwave pyrolysis ofdistillers dried grain with solubles (DDGS) for biofuel production, BioresourceTechnology 102 (10) (2011) 6208–6213.

[8] A.J. Saunders, A.K. Rosentrater, Properties of solvent extracted low-oil corndistillers dried grains with solubles, Biomass and Bioenergy 33 (10) (2009)1486–1490.

[9] L. Wang, A. Kumar, M.A. Hanna, C.L. Weller, D.D. Jones, Thermal degradationkinetics of distillers grains and solubles in nitrogen and air, Energy Sources PartA 31 (10) (2009) 797–806.

10] B. Gudka, L.I. Darvell, J.M. Jones, A. Williams, P.J. Kilgallon, N.J. Simms, R.Laryea-Goldsmith, Fuel characteristics of wheat-based dried distillers grainsand solubles (DDGS) for thermal conversion in power plants, Fuel ProcessingTechnology 94 (1) (2012) 123–130.

11] Y. Liao, S. Wang, X. Ma, Simulation on process of levoglucosan formation duringcellulose pyrolysis, Chemistry and Industry of Forest Products 26 (2) (2006)1–6.

12] Q. Liu, H. Hu, Q. Zhou, S. Zhu, G. Chen, Effect of inorganic matter on reactivityand kinetics of coal pyrolysis, Fuel 83 (6) (2004) 713–718.

13] D. Wang, R. Xiao, H. Zhang, G. He, Comparison of catalytic pyrolysis of biomass

with MCM-41 and CaO catalysts by using TGA–FTIR analysis, Journal of Analyt-ical and Applied Pyrolysis 89 (2) (2010) 171–177.

14] L. Ding, P. Rahimi, R. Hawkins, S. Bhatt, Y. Shi, Naphthenic acid removal fromheavy oils on alkaline earth-metal oxides and ZnO catalysts, Applied CatalysisA: General 371 (1–2) (2009) 121–130.