Bioresource Technology 207 (2016) 85–91

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Bioresource Technology

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Novel carbon-rich additives preparation by degradative solventextraction of biomass wastes for coke-making

http://dx.doi.org/10.1016/j.biortech.2016.01.1050960-8524/� 2016 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel./fax: +86 27 87545526.E-mail address: xian_li@hust.edu.cn (X. Li).

Xianqing Zhu a, Xian Li a,⇑, Li Xiao a, Xiaoyong Zhang b, Shan Tong a, Chao Wu a, Ryuichi Ashida c,Wenqiang Liu a, Kouichi Miura d, Hong Yao a

a State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, Chinab School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243000, ChinacDepartment of Chemical Engineering, Kyoto University, Kyoto 615-8510, Japand Institute of Advanced Energy, Kyoto University, Kyoto 615-8510, Japan

h i g h l i g h t s

� Soluble and Deposit were producedby degradative solvent extraction ofbiomass.

� Soluble and Deposit had goodthermoplastic properties.

� Adding Soluble and Deposit intocoke-making coal improved itsthermoplastic properties.

� The addition of Deposit or Solublemarkedly enhanced the coke quality.

� Soluble and Deposit were proved tobe good additives for coke-making.

g r a p h i c a l a b s t r a c t

Using Soluble and Deposit prepared from biomass as additives for cokemaking.

a r t i c l e i n f o

Article history:Received 16 January 2016Received in revised form 25 January 2016Accepted 27 January 2016Available online 2 February 2016

Keywords:Degradative solvent extractionBiomassAdditivesThermoplasticityCoke-making

a b s t r a c t

In this work, two extracts (Soluble and Deposit) were produced by degradative solvent extraction of bio-mass wastes from 250 to 350 �C. The feasibilities of using Soluble and Deposit as additives for coke-making were investigated for the first time. The Soluble and Deposit, having significantly higher carboncontent, lower oxygen content and extremely lower ash content than raw biomasses. All Solubles andmost of Deposits can melt completely at the temperature ranged from 80 to 120 �C and 140 to 180 �C,respectively. The additions of Soluble or Deposit into the coke-making coal significantly improved theirthermoplastic properties with as high as 9 �C increase of the plastic range. Furthermore, the addition ofDeposit or Soluble also markedly enhanced the coke quality through increasing coke strength after reac-tion (CSR) and reducing coke reactivity index (CRI). Therefore, the Soluble and Deposit were proved to begood additives for coke-making.

� 2016 Elsevier Ltd. All rights reserved.

1. Introduction

Coke is an essential industrial material in iron and steel indus-try, which acts as the important roles of carbon skeleton, main fuel,reducing agent in blast furnace (Hutny et al., 1991). The coking

86 X. Zhu et al. / Bioresource Technology 207 (2016) 85–91

coals for coke production have scarce reserves and much higherprice than steam coals used for electricity generation, because oftheir special physical and chemical properties. Due to the rapidconsumption and increasingly high price of prime coking coals inpast decades, coal blending is a common practice in coke-manufacturing industry to lower the cost of coke-making (CastroDíaz et al., 2012; Shui et al., 2015). However, the addition ofnon-caking coals into coking coal blends usually causes an obviousreduction of the thermoplastic properties of coal blends and thequality of subsequently produced coke. For these reasons, variouscarbon-containing materials, such as pitch, tyre recycling residue,plastics, biochar and petroleum coke, have been used as additivesin coke-making (Du et al., 2014; Fernández et al., 2009; Melendiet al., 2011; Pis et al., 2002). However, these additives usually con-tain high sulfur content, emit high amount of pollutants or result ina certain reduction of the coke quality. Therefore, it is of greatimportance to find or produce substituted additives for coke-making.

The authors have recently presented a degradative solventextraction method to upgrade and convert various types of bio-mass wastes into carbon-rich products (Li et al., 2012, 2015;Wannapeera et al., 2012; Zhu et al., 2015). This method treatsthe biomass wastes in a non-polar solvent below 350 �C under aninert atmosphere. The products consist of an unextractable fraction(termed Residue), high molecular weight fraction (Deposit) whichis extractable at extraction temperature but precipitated at roomtemperature, and low molecular weight fraction (Soluble) whichis also extractable at extraction temperature and still soluble inthe solvent at room temperature. Soluble and Deposit have carboncontent of as high as 80.1–89.5%, and have oxygen content of aslow as 7.3–15.4%. They can melt at around 80–250 �C, like pitch.In addition, the both products are almost free from water andash, and have the sulfur content of all most null since they arebiomass-derived products. In view of their advantageous proper-ties, it seems highly potential for Soluble and Deposit to be usedas additives for coke-making. The Soluble and Deposit, asbiomass-derived additives, also have the advantage of reducingthe CO2 emission over other additives derived from fossil fuelssuch as coal and petroleum, because of the carbon–neutral andzero net carbon dioxide emission characteristics of biomass(Chen et al., 2012; Jeong et al., 2014).

Consequently, in this study, the feasibilities of using these twoextracts (Soluble and Deposit) as additives for coke-making wereexamined for the first time. The Soluble and Deposit were preparedfrom two typical biomasses by degradative solvent extraction atdifferent temperatures and then characterized in detail. Consider-ing the importance of thermoplastic properties of raw coals forfinal coke properties, the influences of Soluble and Deposit addi-tions on thermoplastic properties of coal were investigated. Theeffect of the additions of Soluble and Deposit on the coke qualitieswere finally studied and discussed.

2. Methods

2.1. Degradative solvent extraction procedure

Two typical biomass wastes, a rice straw (RS) and a fir sawdust(SD) from China, were used as the raw biomass materials. The ulti-mate and proximate analyses of RS and SD are presented in Table 1.1-Methylnaphthalene (1-MN), a non-hydrogen donor and non-polar solvent, was used as the solvent for the extraction. The sche-matic diagram of the batch autoclave and detailed experimentalprocedure were already described in our previous studies (Zhuet al., 2016, 2015). Briefly, 30 g of biomass (air-dry basis) andaround 300 mL of 1-MN were charged into the autoclave extractor.

A stainless filter (0.5 lm opening) connecting the autoclave andthe reservoir was equipped at the bottom of the autoclave. Aftersufficiently purging by N2 several times, the extractor was sealedwith N2 of 0.2 MPa and heated to the desired temperature (250,300, 350 �C) at the heating rate of 5 �C/min, and then held at thedesired temperature for 30 min. Then, the valve below the filterwas immediately opened to transfer the extracts along with thesolvent to the reservoir, realizing the in-situ separation of the Resi-due from the extracts. The reservoir and the autoclave extractorwere cooled down by circulating cooling water at ambient temper-ature and an electric fan, respectively. A fraction of the extractswhich was extractable at extraction temperature but precipitatedin the reservoir at room temperature was termed as Deposit. Theother fraction of the extracts which was also extractable at extrac-tion temperature and still soluble in the solvent at room tempera-ture was termed as Soluble. Soluble was separated from Deposit byfiltration. The solid Soluble was obtained by remove the solvent invacuum rotary evaporator at around 150 �C. Subsequently, Resi-due, Soluble and Deposit were further dried in a vacuum dryingoven at 150 �C for 5–8 h to sufficiently remove the residual 1-MN. The gaseous products (Gas) were gathered in a gas bag andanalyzed quantitatively by a gas chromatograph (Micro GC 3000,Agilent). The yields of Gas, Soluble, Deposit and Residue were esti-mated by measuring their weights. The yield of Liquid was thenobtained by mass balance. Each extraction experiment was carriedout at least three times, and the average value was reported withthe experimental errors within 3%.

2.2. Product analyses

The ultimate analysis was performed by an elemental analyzer(CHN EL-2, Vario). The proximate analysis was carried out using amuffle furnace according to GB/T212-2008 standard procedure.Thermal decomposition behaviors of solid products were deter-mined using a thermogravimetric (TG) analyzer (Diamond TG/DTA, PerkinElmer). About 10 mg sample was heated to 900 �C ata heating rate of 10 K/min in a flow of 80 mL/min pure nitrogen.The FTIR spectra of raw biomasses and solid products wererecorded using a Bruker VERTEX-70 FTIR spectrometer rangingfrom 4000 to 400 cm�1 at a resolution of 4 cm�1. The softening/melting behaviors were estimated by using a thermomechanicalanalyzer (TMA Q400EM, TA Instruments). 150 mg of the samplewas compressed under 10 MPa at room temperature into a pellet(8 mm in diameter and around 2.5 mm height) using an electrictablet machine (SDY-20, China). The displacement of the samplepellet was continuously monitored when the pellet was heatedup at 10 K/min under a load of 0.098 N in nitrogen stream in TMA.

2.3. Gieseler test

Gieseler plastometry has long been a widely used method forevaluating coal or coal blends thermoplasticity (Clemens andMatheson, 1995). In this study, a representative gas coal (GC, fromChina) with 36.74 wt% volatile matter (daf basis) was employed asthe base coal of the blends, which contains 77.28 wt% of carbon,1.68 wt% of hydrogen, 3.64 wt% of nitrogen and 17.40 wt% of oxy-gen (dry basis). The proportion of the Soluble or Deposit added toGC was 2.0 wt%. The thermoplastic properties of the raw GC andblends were estimated in a constant-torque Gieseler plastometer(PL-2006A, China), according to the GB/T 25213-2010 standardprocedure. The samples of 0.5 g were heated up from 300 �C to550 �C at a heating rate of 3 �C/min. The parameters reflectingthe thermoplastic properties of the coal or blends were obtainedfrom the test: (1) Ts: softening temperature; (2) Tf: the temperaturecorresponding to maximum fluidity; (3) Tr: resolidification

Table 1Ultimate and proximate analyses of biomasses, Solubles and Deposits.

T (�C) Sample Ultimate analysis (wt.%, daf) Proximate analysis (wt.%,db) Atomic ratio

C H N Ob VM A FC H/C O/C

RS 49.01 5.54 0.81 44.64 75.39 9.98 14.63 1.36 0.68RS-250 Soluble 72.76 6.82 1.29 19.13 77.46 0.14 22.40 1.12 0.20

Deposit 67.33 6.11 1.47 25.08 66.76 0.36 32.88 1.09 0.28RS-300 Soluble 75.78 6.75 1.43 16.04 76.49 0.00 23.51 1.07 0.16

Deposit 73.29 5.91 1.54 19.26 62.75 0.36 36.89 0.97 0.20RS-350 Soluble 78.80 6.73 1.47 12.99 68.57 0.00 31.43 1.03 0.12

Deposit 79.68 6.23 1.81 12.27 46.88 1.54 51.57 0.94 0.12SD 53.11 5.84 0.08 40.97 84.39 1.23 14.37 1.32 0.58

SD-250 Soluble 74.12 6.97 0.64 18.26 81.49 0.00 18.51 1.13 0.18Deposit 69.45 6.06 0.43 24.06 72.71 0.00 27.29 1.05 0.26

SD-300 Soluble 75.97 6.46 0.45 17.12 79.06 0.25 20.68 1.02 0.17Deposit 74.93 5.77 0.19 19.11 68.56 0.75 30.70 0.92 0.19

SD-350 Soluble 76.60 6.17 0.45 16.78 73.19 0.00 26.81 0.97 0.16Deposit 75.86 5.52 0.4 18.22 56.15 0.16 43.69 0.87 0.18

80

100 RS SD

Other gas CO2 Liquid Soluble Deposit Residue

X. Zhu et al. / Bioresource Technology 207 (2016) 85–91 87

temperature; (4) plastic range (Pr): Tr � Ts; (5) MF: maximum flu-idity (ddpm).

2.4. Carbonization experiments and crucible coking assessment

The carbonization experiments were carried out in a laboratory-scale crucible coking oven. The raw coal blends employed in thisstudy was an industrial coal blends provided by an iron and steelcompany from China, which was mainly composed of a coking coal,a gas coal, a fat coal and a lean coal. The proportion of the Solubleor Deposit added to coal blends was 2 wt%. On each run, 100 g ofraw coal blends or coal blends with Soluble or Deposit additionwas heated from ambient temperature to 300 �C at a heating rateof 10 �C/min and then to 1050 �C at a rate of 3 �C/min under anitrogen atmosphere. After the temperature was maintained at1050 �C for 30 min, the crucible was cooled down to room temper-ature to obtain the crucible coke.

The coke reactivity towards CO2 was determined according tothe reported method (Swietlik et al., 1999). Simply, 20 g of cruciblecoke (size in the range of 3–6 mm) was treated in a CO2 flow of500 L/min for 2 h at 1050 �C. The weight loss percentage of thecoke after the treatment was defined as coke reactivity index(CRI). The micro-strength of coke was assessed in accordance withthe Ragan and Marsh test (Ragan and Marsh, 1981). Briefly, twocharges of cokes of 2 g (0.6–1.25 mm in particle size) were loadedinto two separate cylinders (305 mm long and 25.4 mm i.d), andeach cylinders contained 12 steel balls (8 mm diameter). Then,the cokes along with the cylinders were rotated for 800 revolutionsat a rotation speed of 25 rpm. The weight percent of coke particleswith particle size of larger than 0.2 mm was defined as the micro-strength index (MSI) of the coke. The micro-strength of coke afterCRI measurements was designated as coke strength after reaction(CSR) (Shui et al., 2013). The CRI and CSR were all carried out induplicated runs with the errors less than 2%.

0

20

40

60

350300350300250

Yie

ld (

wt %

, daf

)

Temperature (°C)250

Fig. 1. The yield distributions of products obtained from degradative solventextraction of RS and SD.

3. Results and discussion

3.1. Yield distributions of products

Fig. 1 displays the yield distributions of products obtained fromdegradative solvent extraction of RS and SD. It can be observed thatthe extraction temperature exhibit a great influence on the yielddistributions. The yield of Soluble increased significantly with thetemperature rising for both RS and SD, while those of Depositreached a maximum at 300 �C. The sum of yields of extracts,Soluble and Deposit, was rather high at elevated temperature(300, 350 �C), especially reaching as much as 56.8% for SD at

350 �C. Biomass only decomposes slightly at around 250 �C dueto the mild decomposition of hemicellulose (Sanchez-Silva et al.,2012), which should be the reason for the low extract yield at250 �C. However, both the hemicellulose and cellulose decomposeintensively at 280–350 �C (Pasangulapati et al., 2012), so the yieldsof the extracts increased obviously at the temperature of 300 and350 �C. From the viewpoint of the extracts yields, the degradativesolvent extraction of biomass should be conducted at the temper-ature higher than 250 �C.

3.2. Ultimate and proximate analyses

The ultimate and proximate analyses of raw biomasses and theextracts obtained are shown in Table 1. Similar trends of chemicalcomposition variation of the extracts versus extraction tempera-ture were observed for both RS and SD. Compared to raw bio-masses, Soluble and Deposit contained obviously much highercarbon content and lower oxygen content respectively. In addition,the carbon content and oxygen content of Soluble increased anddecreased with the extraction temperature rising, respectively. Itwas also the case for Deposit. This suggests that elevating extrac-tion temperature can promote the deoxygenation of raw bio-masses. Furthermore, the ash contents of the Soluble and Depositwere extremely lower than those of their corresponding raw mate-rial. This could be extraordinarily favorable for the subsequent uti-lization of Soluble and Deposit by mitigating the ash-relatedproblems. To investigate the elemental composition variations,the atomic ratios of H/C versus O/C diagram of raw biomasses,

88 X. Zhu et al. / Bioresource Technology 207 (2016) 85–91

Solubles and Deposits are displayed in Fig. 2 (Van Krevelen dia-gram (Erdogan et al., 2015)). The abbreviation ‘‘RS-250-S” denotesSoluble produced from RS at 250 �C, and by this analogy. It can beobserved that RS and SD fell within the typical biomass region. ButSolubles and Deposit experienced a significant carbonization pro-cess with reduced H/C and O/C ratios, which were caused by dehy-dration and decarboxylation reactions (Parshetti et al., 2013). Fig. 2shows that the Solubles and Deposits were more coal-like productsfrom the viewpoint of the elemental composition. The carboniza-tion severities of Solubles and Deposits increased with the temper-ature rising. But the Solubles and Deposits still contained relativelyhigher H/C ratios than that of coals. According to the hydrogendonor theory (Clemens and Matheson, 1995), richer hydrogen spe-cies may produce more mobile hydrogen donor to stabilize radicalfragments formed from thermal cracking of coal macrostructure. Itmay be beneficial during cokemaking process after Solubles andDeposits addition.

3.3. Chemical structure analysis

The chemical structures of raw biomasses, Solubles and Depos-its were investigated by FTIR technique, as shown in Fig. S1. Thebroad adsorption band in the range of 3200–3600 cm�1 and1000–1100 cm�1 were respectively attributed to hydrogen bond-ing (–OH groups) and C–O groups, which were characteristic struc-ture of cellulose (Eberhardt et al., 2010; Tandy et al., 2010). Thisindicates the raw biomasses were rich of oxygen-containing func-tional groups. However, Fig. S1 shows that the Soluble and Deposithave completely different structures compared to the raw bio-masses. The peaks associated with oxygen-containing groups (suchas –OH stretching and C–O stretching) dramatically weakened.Also, the intensities of oxygen groups (especially for –OH) in Sol-uble and Deposit decreased with extraction temperature increas-ing, which is consistent with the ultimate analysis, as shown inTable 1. The oxygen groups, including hydroxyl, are deleteriousfor coke-making since they can deplete the donor hydrogen andleading to the formation of cross-linked chars (Clemens andMatheson, 1995). Hence, the lower content of oxygen groups inSoluble and Deposit is beneficial for its use in coal blends. Thepeaks attributed to aromatic groups, such as aromatic C–H stretch-ing vibration at 3050 cm�1, aromatic C@C stretching band at 1460–1600 cm�1 and aromatic out-of-plane C–H bending at 750–875 cm�1, were found to prevail in the spectra of both Solubleand Deposit.

Coal

Peat

Biomass– H2O– CH4

– CO2

0.0 0.2 0.4 0.6 0.8 1.00.0

0.5

1.0

1.5

2.0

RS

RS SDRS-250-S RS-300-S RS-350-SSD-250-S SD-300-S SD-350-SRS-250-D RS-300-D RS-350-DSD-250-D SD-300-D SD-350-D

H/C

O/C

SD

Fig. 2. Atomic H/C vs O/C diagram of raw biomasses, Solubles and Depositsobtained at different temperaures.

3.4. Thermal decomposition behavior analyses

Fig. 3 presents TG-DTG curves of Solubles and Deposits obtainedat 250–350 �C as well as the raw biomasses. The sharp peakbetween 280 �C and 400 �C observed in the DTG curves of bothRS and SD were mainly attributed to the decomposition of hemi-cellulose and cellulose. All the Solubles and Deposits exhibitedquite different decomposition behaviors compared to those ofraw RS and SD. In general, Soluble and Deposit displayed lowerweight loss rates over a wider temperature range. The weight lossrates of the Solubles decreased slightly with the extraction temper-ature increasing, which may imply that the Soluble obtained atlower extraction temperature contained more light components.As for Deposits, a greater difference appeared up among TG andDTG curves of them. Overall speaking, the weight loss of Depositsreduced with the temperature rising. There are two overlappedpeaks in the DTG curves of Deposits from both RS and SD. Theweight loss rates also weakened with the extraction temperatureincreasing, like Solubles. The temperature ranges correspondingto the weight loss of Deposits became wider with the extractiontemperature increasing for RS, while those became narrower forSD. The difference should be caused by the different chemicalstructures of Deposits obtained from RS and from SD as shown inFig. S1.

3.5. Softening and melting behavior analyses

The softening and melting behaviors of Solubles and Depositswere estimated by thermomechanical analysis (TMA). Fig. 4 showsthe TMA profiles of Soluble and Deposit obtained from RS and SD.The TMA profile, displaying the normalized displacement of thesample, reaches �1.0 when the sample melts completely. Aspointed out in previous study, raw biomass did not exhibitany melting or softening behaviors (Wannapeera et al., 2012).However, it is interestingly found that the displacements temper-ature range of all Solubles from both RS and SD were as low as80–120 �C, which was much lower than the temperature pointswhere the Solubles started to decompose, as shown in Fig. 3. Gen-erally, the melting points of Solubles produced at elevated temper-ature shifted to higher temperature, although they all fell in anarrow temperature range of 80–120 �C. In comparison with theSolubles, there were obvious bigger differences among the soften-ing or melting behaviors of the Deposits from either differentextraction temperatures or different raw biomasses. The Depositsobtained at 250 �C from both RS and SD could completely melt ataround 140 �C. The melting temperature of Deposit from SD at350 �C shifted to higher temperature (180 �C), while the Depositfrom RS at 350 �C did not show complete plastic behaviors. Thedifferent softening and melting behaviors of Soluble and Depositare expected to have different effects on the thermoplastic proper-ties of coal blends.

3.6. Thermoplastic properties of coal blends

The quality of produced coke greatly depends on the thermo-plastic properties of the raw coals (Fernández et al., 2009). So theinfluence of the extracts addition on thermoplastic properties ofcoal blends was probed by Gieseler test. Table 2 shows the thermo-plastic parameters of the GC and its blends with 2 wt% Soluble orDeposit additions. The plastic range of raw GC was only 74 �C.For Solubles addition, the softening temperature of coal blendsdecreased slightly, while the resolidification temperature of blendsincreased significantly. These leads to the enhancement of plasticrange as high as 9 �C, especially for Soluble prepared at elevatedtemperature. The more significant enhancement of the plasticrange of the blends with Solubles prepared at elevated

100 200 300 400 500 600 700 8000

20

40

60

80

100

Wei

ght l

oss

(wd /%

)

Temperature (°C)

RS RS-250-S RS-300-S RS-350-S RS-250-D RS-300-D RS-350-D

100 200 300 400 500 600 700 8000

20

40

60

80

100

Wei

ght l

oss

(wd /%

)

Temperature (°C)

SD SD-250-S SD-300-S SD-350-S SD-250-D SD-300-D SD-350-D

100 200 300 400 500 600 700 800

-10

-8

-6

-4

-2

0

DT

G (

%/m

in)

Temperature (°C)

RS RS-250-S RS-300-S RS-350-S

100 200 300 400 500 600 700 800

-10

-8

-6

-4

-2

0

SD SD-250-S SD-300-S SD-350-SD

TG

(%

/min

)

Temperature (°C)

100 200 300 400 500 600 700 800

-10

-8

-6

-4

-2

0

RS RS-250-D RS-300-D RS-350-D

DT

G (

%/m

in)

Temperature (°C)

100 200 300 400 500 600 700 800

-10

-8

-6

-4

-2

0

DT

G (

%/m

in)

Temperature (°C)

SD SD-250-D SD-300-D SD-350-D

Fig. 3. TG-DTG curves of raw biomass and Soluble, Deposit obtained from RS and SD at 250–350 �C.

X. Zhu et al. / Bioresource Technology 207 (2016) 85–91 89

temperature should be attributed to the lower oxygen content andhigher melting temperature in Solubles at higher temperature(Shui et al., 2015), as shown in Table 1 and Fig. 4. The Depositsobtained from the both raw biomasses also increased the resolidi-fication temperature and enhanced the plastic range of the blends,like Solubles. However, the additions of the Deposits obtained fromRS increased the softening temperature of the blends slightly, espe-cially for the Deposits produced from RS at 350 �C. This should bebecause that the Deposits produced from RS at elevated tempera-ture cannot melt completely before resolidification as shown inFig. 4. Additionally, it has been proved by the MOF model thatthe log (MF) value ranged from 2 to 3 was the optimum windowto obtain a strong coke (Diez and Alvarez, 2013; Fernández et al.,2015). The log (MF) values of the GC with Solubles or Depositsaddition nearly all fell within the optimumwindow. Thus, the ther-moplastic properties of the coal were improved by incorporation of

the Soluble or Deposit obtained from biomasses. So, it is expectedthat the coal blends with Solubles and Deposits addition can pro-duce coke with good strength.

3.7. Coke quality evaluation

Coke reactivity index (CRI) and coke strength after reaction(CSR) are the two most important parameters to assess the cokequality and its behavior in the blast furnace (Shui et al., 2015). Ingeneral, the high-quality coke is supposed to possess a lower CRIand a higher CSR. In this work, the coke quality was evaluated bycrucible coking process. It was found that the GC with RS-350-Sor SD-350-D addition had widest plastic range of 83 �C andsuitable values of log (MF), as shown in Table 2. So, the CRIand CSR of the raw coal blends and the blends with 2% additionsof RS-350-S or SD-350-D were estimated. The results are

0 50 100 150 200 250 300-1.0

-0.8

-0.6

-0.4

-0.2

0.0

RS-250-S RS-300-S RS-350-S RS-250-D RS-350-D

Nor

mal

ized

dis

plac

emen

t [-]

Temperature (°C)

0 50 100 150 200 250 300-1.0

-0.8

-0.6

-0.4

-0.2

0.0

SD-250-S SD-300-S SD-350-S SD-250-D SD-350-D

Nor

mal

ized

dis

plac

emen

t [-]

Temperature (°C)

Fig. 4. The TMA profiles of Soluble and Deposit obtained from RS and SD at 250–350 �C.

Table 2Thermoplastic parameters of raw GC and it with 2 wt% Soluble or Deposit additions.

Sample Addition Ts(�C)

Tf(�C)

Tr(�C)

Pr(�C)

Log(MF)(ddpm)

GC 402 439 476 74 3.1RS-Soluble RS-250-S 399 443 475 76 3.1

RS-300-S 403 444 482 79 2.9RS-350-S 398 436 481 83 2.9

SD-Soluble SD-250-S 403 446 479 76 2.5SD-300-S 399 439 480 81 3.0SD-350-S 400 445 483 83 3.0

RS-Deposit RS-250-D 403 442 485 82 3.0RS-300-D 404 445 480 76 2.7RS-350-D 407 443 482 75 2.7

SD-Deposit SD-250-D 402 444 481 79 2.9SD-300-D 403 445 483 80 3.0SD-350-D 400 444 483 83 2.9

Ts: softening temperature; Tf: the temperature corresponding to maximum fluidity;Tr: resolidification temperature; plastic range (Pr): Tr � Ts; Log(MF): logarithm ofmaximum fluidity (ddpm).

Coal blends RS-350-S SD-350-D10

20

30

40

50

CSR

/CR

I (%

)

CRI CSR

Fig. 5. The CRI and CSR values of the cokes produced from raw coal blends and theblends with Soluble or Deposit additions.

90 X. Zhu et al. / Bioresource Technology 207 (2016) 85–91

presented in Fig. 5. Compared to raw coal blend, the CRI of cokeobtained from the blends with RS-350-S decreased from 38.7% to36.7%, and the CSR of the coke increased significantly from 33.8%to 45.0%. The CSR of the coke obtained from the blends with SD-350-D also increased obviously from 33.8% to 46.1%, although theCRI of the blends was slightly higher than that of the raw coalblends. Hence, it can be concluded that the additions of Solublesor Deposits obtained from biomasses could enhance the cokequality.

4. Conclusion

Soluble and Deposit with good thermoplastic properties wereproduced by degradative solvent extraction of biomass wastesunder mild condition. The Soluble and Deposit had significantlyhigher carbon content, lower oxygen groups (such as –OH groups)and extremely lower ash content, compared to raw biomasses. Theadditions of Soluble or Deposit into the coke-making coal signifi-cantly improved its thermoplastic properties. Furthermore, theaddition of Deposit or Soluble markedly enhanced the coke qualitythrough increasing coke CSR and reducing CRI. Therefore, the Sol-uble and Deposit prepared from degradative solvent extraction ofbiomass wastes were proved to be good additives for coke-making.

Acknowledgements

The authors thank the financial support from the National Nat-ural Science Foundation of China (21306059, U1510119), Interna-tional Science & Technology Cooperation Program of China(2015DFA60410), National Natural Science Foundation of China(51306063), and the Foundation of State Key Laboratory of CoalCombustion. The authors also wish to acknowledge the Analyticaland Testing Center of Huazhong University of Science and Technol-ogy, for providing the equipments for various measurements.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.biortech.2016.01.105.

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