Article pubs.acs.org/EF
Characteristics of Coal and Pine Sawdust Co-carbonization Linbo Qin,† Jun Han,*,† Wei Ye,† Shun Zhang,† Qiangu Yan,‡ and Fei Yu*,‡ †
Hubei Key Laboratory of Coal Conversion and New Materials, Wuhan University of Science and Technology, Wuhan 430081, People’s Republic of China ‡ Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi State, Mississippi 39762, United States S Supporting Information *
ABSTRACT: All energy scenarios show a shift toward an increased percentage of renewable energy sources, including biomass. In this study, pine sawdust (PSD) was added to coals to make coke used for blast furnaces. The influences of PSD additive on coke quality, tar composition, and non-condensable gas components were evaluated during coal/PSD co-carbonization. The experimental results indicated that the addition of 5% PSD into coals did not have an evident effect on coke qualities, such as abrasion index (M10), fragmentation index (M40), coke reactivity index (CRI), and coke strength after reaction with CO2 (CSR). It was also observed that the tar and coke gas yields were remarkably increased when the mass fraction of PSD was increased from 0 to 10%. Moreover, the addition of PSD favors producing low-molecular-weight compounds and improving the quality of liquid tar. miscanthus reduced the fluidity even with 2 wt % addition. The biomass can act as an additive of changing the fluid material in coking coal, and the viscoelastic properties of the blend are identical to those of prime coking coals. Diez et al.10 also stated that the addition of biomass to coking coals was expected to have a deleterious effect on the coke strengths, which had been proven by Matsumura et al.11 MacPhee et al.12 pointed out that the addition of 5 wt % biomass to coking coals reduced the coke strength after reaction (CSR) index from 56.7 to 35.8, which was below the limits of metallurgical coke. On the contrary, Hanrot et al.13 claimed that the partial substitution of coal by biomass in a coke plant had a double advantage of reducing CO2 emissions and improving coke reactivity to lower the reserve zone temperature of the blast furnace. They also presented that the incorporation of charcoal produced more reactive cokes and decreased the threshold temperature of the Boudouard reaction. With a charcoal addition of 3 wt % in a fluid-enough blend and by gravity charging, all coke properties keep a correct level but the gasification temperature was reduced by only 100 °C. However, most previous studies about making coke by biomass/coals have focused on coke qualities, and the influence on coke oven gas and tar components has been minimally reported. In fact, coke oven gas and tar are very important byproducts in a coke plant. In this study, coal and pine sawdust (PSD) co-carbonization was studied in a fixed-bed reactor and a 5 kg laboratory-scale coke oven. Meanwhile, the effects of PSD addition on the product qualities (coke, tar composition, and non-condensable gases) were also evaluated.
1. INTRODUCTION Coke, one of the necessary raw materials for blast furnaces, mainly acts as a fuel, a reducing agent, and a permeable support of blast-furnace charge during the iron-making process. In 2011, the production and consumption of coke in China were 428 and 384 million tons, respectively.1 It is forecasted that the consumption of coke in 2020 will be kept at 370 million tons,2 which needs 500 million tonnes of coking coal. However, only part of coal can be used for making coke. It was reported that the reserve of coking coal was only 27% of the total coal reserve in China, about 276 billion tons.3 Hence, it is necessary to find an alternative fuel or material that can replace part of coking coal. As is well-known, coke utilization will produce a great amount of CO2. The steel industry accounts for 3% global CO2 emissions and 5−7% total anthropogenic CO2 emissions.4,5 In 2009, the Chinese government announced that China would cut the intensity of carbon dioxide emissions per unit of gross domestic product in 2020 by 40−45% from 2005 levels.6 To reduce carbon dioxide emissions on such a large scale and over such an extended period of time, tremendous efforts are needed to be made. Replacing fossil fuels with sustainably produced biomass is a promising method of reducing CO2 emissions. The net flow of CO2 is zero during biomass utilization because plants need CO2 to grow and the energy utilization emits CO2.7,8 The addition of biomass into coals to make coke offers two advantages: one is reducing production costs by replacing part of expensive prime coking coals, and another is reducing CO2 emissions because biomass is carbon-neutral. A great amount of researches about coutilizing of biomass and coal have been ́ et al.9 investigated the effect of biomass reported. Castro Diaz (pine wood, sugar beet, and miscanthus) on the fluidity properties of coal. The results indicated that sugar beet could be added to metallurgical coals up to 5 wt % without altering the viscoelastic properties of the coals, whereas pine wood and © 2014 American Chemical Society
Received: September 30, 2013 Revised: January 12, 2014 Published: January 13, 2014 848
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Table 1. Basic Characteristics of These Coals and Biomass Blend Coal proximate analysis (%)
plastometer
moisture
ash
volatile
fixed carbon
1.59
10.10
28.92
59.39
SiO2
Al2O3
Fe2O3
TiO2
P2O5
47.71
33.44
10.40
1.98
0.27
sulfur (%)
coking index
X
Y
78
23.16
18.48
0.49 ash chemistry (%)
CaO
MnO
Na2O
K2O
BaO
basicity index
4.05 0.91 0.06 blend ratio of seven coals (%)a
MgO
0.29
0.78
0.11
0.160
coal 1
coal 2
coal 3
coal 4
coal 5
coal 6
coal 7
20
5
10
15 PSD
10
22
18
proximate analysis (%)
a
plastometer fixed carbon
sulfur (%)
Y
ash
volatile
9.78
0.78
65.09
SiO2
Al2O3
Fe2O3
P2O5
MgO
Na2O
BaO
basicity index
29.33
7.90
4.57
2.33
6.93
0.34
0.34
0.127
24.35 ash chemistry (%)
coking index
X
moisture
0.11
The main characteristics of coals 1−7 are given in the Supporting Information. and analyzed by gas chromatography−mass spectrometry (GC−MS, Agilent 19091S-433, Agilent Technologies, Inc., Santa Clara, CA). The yields of tar and coke were calculated according to their weights, while the yield of the non-condensable gases was calculated by a different method. The low heating values of tar and coke were also measured by a calorimeter (YX-ZR/Q 9704, Li Thermal Company, China) according to GB/T213-2008. As for the noncondensable gases, the low heating was calculated on the basis of CO, H2, CH4, CmHn concentrations and their caloric values. 2.2.2. Laboratory-Scale Coke Oven (5 kg Capacity). To study the effect of PSD on coke quality parameters [such as CSR, coke reactivity index (CRI), fragmentation index (M40), abrasion index (M10), apparent density, true density, and bulk porosity of the cokes], the coal/PSD blends were carbonized in a 5 kg laboratory-scale coke oven. The scheme of the 5 kg laboratory-scale coke oven is presented in Figure 2. The chamber is electrically heated, and the temperatures of the reactor are automatically controlled by two thermocouples. To simulate the operation conditions in the coke plant, the 5 kg coke oven is heated by the following temperature program: (1) the temperature increases from 40 to 800 °C at 20 °C/min; (2) the temperature is
2. MATERIALS AND METHODS 2.1. Materials. A blended coal and a biomass (PSD) were used in this study. The blended coal was composed of seven different rank coals (identified as coals 1−7). Before the experiments, the seven coals were mixed (the detailed characteristic information of the seven coals can be found in the Supporting Information). The basic characteristics of the blend coal and biomass were listed in Table 1. Then, the blended coal was milled to less than 3 mm, while the PSD was milled to 0.3−0.6 mm. Last, milled PSD was mixed with the milled coal at a mass percentage of 3, 5, 7, and 10%, respectively. 2.2. Carbonization Tests. 2.2.1. Fixed-Bed Reactor. The effects of biomass addition on the distributions and components of gaseous and liquid tar were studied in a fixed-bed reactor, as shown in Figure 1.
Figure 1. Scheme of the fixed-bed reactor: (1) furnace cover, (2) furnace stack, (3) reactor, (4) thermocouple, (5) temperature control, (6) silicone tube, (7) glass bottle, (8) gas bag, (9) cooling water, (10) stopper, and (11) glass tube. The system consists of a stainless-steel reactor with a diameter of 60 mm and a height of 100 mm, a heater, and a cooling system for separating water from condensable tar. The heater is electrically heated, and the temperature is controlled by a thermocouple. Before the experiment, 30 g of sample was fed into the fixed-bed reactor. The reactor was heated from room temperature to 1000 °C at a rate of 10 °C/min and held at 1000 °C for 30 min. The volatiles that were released from coal/PSD pass through a condenser and then are collected by a gas bag. The low heating values and components of coke oven gas were analyzed by a infrared gas analyzer (Gasboard-3100, China). The tar was collected by a glass tube condensed with water
Figure 2. Scheme of the laboratory-scale coke oven (5 kg capacity): (1) carbonization chamber, (2) furnace door, (3) heating chamber, (4) furnace stack, (5) temperature control, (6) thermocouple, (7) chimney, (8) resistance wire, and (9) moving parts. 849
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isothermally held at 800 °C for 30 min; (3) the temperature ramps from 800 to 900 °C at the rate of 1.5 °C/min; (4) the temperature is isothermally held at 900 °C for 30 min; and (5) the temperature ramps at 2 °C/min to 1150 °C and is held at 1150 °C for 90 min. Before the experiment, the coal/PSD blend with a moisture content of 10 wt % was charged in a steel box (200 mm width, 210 mm length, and 230 mm height). The steel box was used to simulate the carbonization chamber. When the temperature of the coke oven rises to 800 °C, the steel box with the coal/PSD blend was placed into the coke oven. After the central temperature of the coke reaches 950−960 °C, the test run was completed. Finally, the coke was quenched using water. 2.3. Product Pretreatment and Analysis. 2.3.1. Coke Pretreatment and Analysis. According to the Chinese Standard (GB/T 20062008), the cold mechanical strength of the cokes must be first assessed. After the cold mechanical strength test, the cokes were sieved and the M40 index (the amount of coke with a particle size greater than 40 mm) and the M10 index (the amount of coke with a particle size lower than 10 mm) were calculated. Then, 200 g of coke with a particle diameter of 21−25 mm was reacted with CO2 at a flow rate of 5 L/min for 2 h at 1100 °C to determine the CRI. The reacted cokes were placed in an I-type drum (MKM-2000, Hebi Tianhong Instrument Co., China) and subjected to 600 revolutions for 30 min according to GB/T2006-94. The percentage of cokes with +10 mm diameter was defined as the coke strength after reaction (CSR). In addition, the apparent density and true density were determined according to the ISO 1014-1985 standard procedure, and then the bulk porosity of the coke was calculated. To ensure the reliability of the results, the above experiments were repeated 5 times and the average data and error bar of the results were presented in Figures 3−5.
Figure 5. Effect of PSD on the apparent density and true density. 2.3.2. Tar Pretreatment and Analysis. First, the tar samples collected from the fixed-bed reactor were dehydrated by anhydrous sodium sulfate and filtered to remove the dust. Then, the tar was separated into several groups, such as aliphatics, aromatics, oxygencontaining compounds, and asphaltene fraction, by the planigraphy separation method. The planigraphy, taking the solid adsorbent as the stationary phase, is the liquid−solid chromatography. Silica gel and alumina were used as the adsorbent materials in this experiment. Before the experiment, silica gel and alumina had been activated at 105 and 400 °C for 4 h, respectively. A total of 2 g of activated alumina and 3 g of activated silica gel were loaded into the planigraphy column successively each time. According to the difference of absorbability between various types of organics in tar and adsorbents, a successive separation of the tar sample into aliphatics, aromatics, and heavy oxygenated hydrocarbons was achieved by eluting with normal pentane, benzene, and ethyl acetate, respectively. The remainder of the tar sample was regarded as the asphaltene fraction. The rotary evaporator was used to evaporate the solvent in each fraction. Finally, the liquid of each fraction was analyzed by GC−MS to determine their components. In this experiment, GC was equipped with a 30 m × 0.25 mm capillary column coated with a 0.25 μm thick film of 5% phenyl methyl siloxane (HP-5 MS). The carrier gas flow (He) was 1 mL/min, and the split ratio was 10:1. The initial oven temperature of 40 °C was kept isothermal for 4 min, then heated to 300 °C at a rate of 10 °C/ min, and held at 300 °C for 10 min. The temperatures of the MS source and MS quad were 230 and 150 °C, respectively. The full-scan mode with mass to charge (m/z) ratios from 30 to 500 was used, and the solvent delay was 2 min. The chromatographic peaks were identified according to the National Institute of Standards and Technology (NIST) mass spectral data library. 2.3.3. Gas Analysis. CO, CO2, H2, CH4, CmHn (m ≤ 3; n ≤ 8), O2, and the low heating value of the non-condensable gases produced from coal/PSD blend carbonization were also recorded by the gas analyzer (Gasboard-3100, China). The Gasboard-3100 infrared gas analyzer is based on the single-source two-beam non-dispersion infrared (NDIR) method for CO, CO2, CH4, and CmHn and microthermal conductivity detector (TCD) gas sensor for H2 and O2 by the fuel cell method. The maximum measure ranges for CO, CO2, H2, CH4, CmHn, and O2 are 25, 50, 100, 100, 50, and 25%, respectively, and the precision for CO, CO2, H2, CH4, and CmHn is ≤1% full scan.
Figure 3. Effect of PSD on the cold strength.
3. RESULTS AND DISCUSSION 3.1. Mass and Energy Distribution of the Products. Table 2 demonstrates the mass distributions of products obtained from coal/PSD carbonization in a fixed-bed reactor. It is found that the main carbonization products from PSD are tar, gas (calculated by the difference method), char, and water; their mass fractions are 42.84, 20.09, 27.20, and 9.87%, respectively, while the yields of tar, gas, coke, and water for the blended coal
Figure 4. Effect of PSD on the hot performance of the coke. 850
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Table 2. Mass Distribution of Products Obtained from Coal and Biomass Co-carbonization tar (%) PSD (%) 100 0 3 5 7 10
experiment 42.84 6.78 8.06 8.97 10.16 10.88
± ± ± ± ± ±
gas (%) calculation
0.24 0.13 0.11 0.08 0.15 0.12
7.86 8.58 9.30 10.39
± ± ± ±
0.24 0.23 0.22 0.20
experiment 20.09 12.03 12.70 12.80 12.93 13.23
± ± ± ± ± ±
0.21 0.18 0.14 0.18 0.12 0.13
coke (%) calculation
12.27 12.43 12.59 12.84
± ± ± ±
0.21 0.21 0.20 0.19
experiment 27.2 77.12 75.01 73.86 72.43 71.16
± ± ± ± ± ±
0.18 0.34 0.15 0.14 0.17 0.16
water (%)
calculation
75.62 74.62 73.63 72.13
± ± ± ±
0.19 0.20 020 021
experiment 9.87 4.07 4.23 4.37 4.48 4.73
± ± ± ± ± ±
0.11 0.07 0.09 0.09 0.12 0.08
calculation
4.24 4.36 4.48 4.65
± ± ± ±
0.11 0.10 0.10 0.10
Table 3. Energy Distribution of the Products energy distribution of the products tar (%) PSD (%)
experiment
100 0 3 5 7 10
67.67 14.77 16.62 18.06 20.03 21.60
gas (%) calculation
experiment
16.36 17.42 18.47 20.06
10.91 7.29 7.63 7.76 7.88 8.30
coke (%) calculation
experiment
calculation
7.40 7.47 7.54 7.65
21.42 77.95 75.75 74.18 72.09 70.11
76.25 75.12 73.99 72.30
remaining oxygen-rich compounds that release in the coal plastic stage, which may promote a rapid cross-linking and rapid stabilization of free radicals by consuming hydrogen available in the system, and (ii) the addition of biomass particles increases the amount of inert particles (biomass is a physically inert component in the blend with chemical activity) in the plastic stage; thus, the concentration of active components in the plastic stage needed for a good agglomeration is lower. Figure 4 indicates that CSR of coke increases from 53.18 to 56.32 with the PSD mass concentration increasing from 0 to 3% and then decreases to 39.39% when the PSD mass percentage is 10%. In contrast, CRI of coke is first decreased, followed by increasing as the PSD mass percentage is above 3%. The concentration of CaO, K2O, and MnO in PSD is relatively high, while the presence of oxides of alkali metals, such as Ca, Ba, Na, and K, negatively affects the quality of coke produced with respect to CRI and CSR.17 Moreover, Macphee et al. pointed out that the mineral matter content of the biomass, particle size, and CSR/CRI tests had an significant influence on the variation of the coke quality.12 On the basis of the experimental results, it can be concluded that the addition of 5% PSD has no significant influence on the coke quality indexes (both cold and hot performances). Even 3% PSD addition has a positive effect on the coke qualities. Meanwhile, CRI is decreased by 1.48. However, when the mass percentage of PSD is above 5%, M40 and CSR of coke are gradually decreased and M10 and CRI are dramatically increased. Indeed, the addition of 2% sawdust will reduce the maximum fluidity of blend coals, which leads to the detrimental effect of the coke structure and its final properties.18 Because of biomass containing more volatile matter, more gases or tar are formed during coal and biomass cocarbonization when the mass concentration of biomass is increased and the specific surface area of coke is also increased. Thus, CO2 can easily diffuse into and react with coke, which results in the decrease of CSR and increase of CRI. Moreover, Table 1 indicates that PSD ash contains about 10.87% K2O and 37.2% CaO, which can be used as a catalyst for the reaction of coke and CO2.19
are 6.78, 12.03, 77.12, and 4.07%, respectively. When 10% mass concentration of PSD is added to the blend coal, the yields of tar and gas are increased from 6.78 to 10.88% and from 12.03 to 13.23%, respectively. On the contrary, the yield of the coke is decreased from 77.12 to 71.16% because of PSD containing more volatile matter, which was converted to gas or liquid products during coal/PSD carbonization. Moreover, the yields of the experiments and the calculations during coal/PSD carbonization were compared. As shown in Table 2, the experimental values of tar and gas yields are slightly higher than the calculated values. On the contrary, the coke yield is lower than the calculated values. The experimental water yield is consistent with the calculated value, which is proven by other researchers.13−15 The above results can be explained by two reasons: one is that the biomass in blends plays a hydrogenation role on coal pyrolysis, resulting in some obvious synergetic effects during the co-pyrolysis of biomass and coal. Thus, tar and gas yields are increased, while the coke yield was decreased. Another may be that the high content of Fe2O3 and P2O5 in PSD may be responsible for the decreasing char yield in the case of the PSD/coal blend.16 The energy distribution is presented in Table 3. Similar to the distribution of the mass, the energy in the tar and gas is also increased when biomass is added to the blended coal. However, there are some differences between the experimental and calculated values because of the secondary reaction of gas−solid phases. 3.2. Effect of PSD on the Quality of Coke. The effects of PSD addition on the cold strength (M10 and M40) and hot performances (CRI and CSR) of coke produced from the 5 kg laboratory-scale coke oven are given in Figures 3 and 4, respectively. In Figure 3, M10 of coke is first decreased from 7.33 to 6.68% as the mass concentration of PSD increases from 0 to 3%, followed by the increase from 6.68 to 25.00% as the mass concentration of PSD increases from 3 to 10%. PSD addition can promote M40 of coke when the PSD mass concentration range is 0−3%. The further addition of PSD has a negative influence on M40 because of the decrease of the plasticity of coal/PSD. Biomass seems to decrease the coal plasticity because of the two mechanisms: (i) the presence of 851
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Table 4. Main Components of Tar mass fraction of biomass (%) tar composition asphaltene aliphatics aromatics oxygenated hydrocarbons others aliphatics
aromatics
oxygenated hydrocarbons
cycloalkane alkane alkene others substituted benzene naphthalene and its derivatives indene and its derivatives biphenyl and its derivatives fluorene and its derivatives anthracene and its derivatives phenanthrene and its derivatives pyrene and its derivatives others phenol and its derivatives acids aldehydes alcohols others
0%
3%
5%
7%
10%
34.64 11.94 44.07 7.25 2.10 1.65 8.38 1.06 0.85 26.49 8.35 1.03 0.71 2.00 0.84 2.87 0.55 1.23 3.82 0.80 0.80 0.74 1.09
33.47 13.11 42.86 8.05 2.51 1.63 9.25 1.22 1.01 25.44 8.59 0.84 0.82 2.24 0.82 1.30 0.83 1.98 4.25 0.93 0.95 0.89 1.03
32.44 13.50 42.42 8.84 2.80 1.68 9.64 1.19 0.99 24.38 8.64 0.80 0.79 2.16 0.80 1.35 0.92 2.58 4.76 1.06 0.98 0.97 1.07
31.79 14.12 41.93 9.06 3.10 1.62 9.80 1.45 1.25 23.87 8.58 0.67 0.91 2.24 0.67 1.04 0.91 3.04 4.99 1.15 0.99 1.04 0.89
31.07 15.43 40.06 10.07 3.37 1.69 11.54 1.20 1.00 21.12 8.34 0.32 1.00 2.42 1.10 1.26 1.16 3.34 5.62 1.38 1.00 1.23 0.84
decreased and then increased as the PSD addition is increased from 0 to 10%, while the content of octacosane increases with PSD addition. On the contrary, dodecane decreases with adding PSD because of tar of PSD contains no dodecane. The aromatic compounds in the tar (Table 6) mainly include substituted benzene, naphthalene and its derivatives, indene and its derivatives, biphenyl and its derivatives, fluorene and its derivatives, anthracene and its derivatives, phenanthrene and its derivatives, pyrene and its derivatives, etc. Ethylbenzene (peak 2 in Figure 7), p-xylene (peak 3 in Figure 7), derivatives of benzene and naphthalene (peaks 12, 31, 32, and 33 in Figure 7), and toluene (peak 1 in Figure 7) are the five most dominant compounds of the aromatic group, while benzene was not found in the aromatic group. In addition, substituted benzene in the aromatic group is the most dominant compound, at about 21.12−26.49%. However, substituted benzene in tar is decreased from 26.49 to 21.12% as the PSD concentration is increased from 0 to 10% because of tar from PSD containing less aromatic compounds.20 Oxygenated hydrocarbons (Table 7) contain some heavy oxygenated compounds, such as phenol and its derivatives, carboxylic acids (RCOOH), and ketones (RCOR). The content of phenol and its derivatives in tar is increased from 3.82 to 5.62% when the PSD fraction is increased from 0 to 10%, as shown in Table 4. This can be explained by the reasons that the aromatic compounds are the main products in tar during coal carbonization, while aliphatic and heavy oxygenated compounds are the primary components in bio-oil during PSD carbonization. Thus, in comparison to the tar compositions obtained from coal carbonization, PSD addition increases the relative contents of aliphatics and heavy oxygenated compounds during coal and PSD co-carbonization while decreasing the content of the aromatic compounds in tar. Although lignin (one of the main components of PSD) is a precursor of oxygenated compounds forming phenolic and methoxy
In addition, the apparent density, true density, and bulk porosity of the cokes produced from coal/PSD co-carbonization were also analyzed, as shown in Figure 5. It can be seen that the true relative density and bulk porosity are increased, while the apparent density is decreased, when the mass concentration of PSD is increased from 0 to 10%. 3.3. Effect of PSD Addition on Tar Composition. Tar is a complex mixture, which contains thousands of organic compounds varying from a wide variety of chemical groups. The main components of the tar from coal/PSD cocarbonization are summarized in Tables 4−7. Generally, the main components of tar can be divided into four groups as follows: asphaltenes, aromatics, aliphatics, and oxygenated groups. Figures 6 and 7 compare the chromatograms of the tars from the coal blend adding 10 wt % PSD and the coal blend. Table 4 indicates that the addition of biomass has a significantly influence on the tar compositions. When the mass concentration of PSD is increased from 0 to 10%, asphaltene and aromatic contents in tar are decreased from 34.64 to 31.07% and from 44.07 to 40.06%, respectively. In contrast, aliphatics increased from 11.94 to 15.43%. Similar to aliphatics, oxygenated hydrocarbons are also increased from 7.25 to 10.07%. The results reveal that coal/PSD co-carbonization favors producing the low-molecular-weight compounds and improving the quality of tar by the contribution of the hydropyrolysis and hydrogenation reactions.14 The aliphatic compounds (Table 5) in the tar mainly involve various C6−C28 hydrocarbons, such as alkane, alkene, and cycloalkane. Among the hydrocarbons, the concentration of nonane (peak 9 in Figure 6), dodecane (peak 16 in Figure 6), octacosane (peak 18 in Figure 6), and docosane (peak 22 in Figure 6) are the highest in the aliphatic group. Meanwhile, there are about 3% compounds that cannot be identified by GC−MS. Moreover, it was also found that the contents of nonane and docosane in the aliphatic compounds first 852
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Table 5. Detailed Compositions of the Aliphatics in the Tar mass fraction of biomass (%) peak
retention time
aliphatic fraction in the tar 1 4.15 2 4.20 3 4.28 4 4.40 5 6.10 6 6.17 7 7.20 8 7.27 9 7.59 10 7.71 11 7.94 12 8.16 13 8.25 14 8.39 15 11.27 16 12.86 17 14.22 18 15.69 19 16.94 20 18.73 21 19.28 22 20.35 23 21.38 24 22.35 25 23.27 26 24.17 27 25.77 28 25.84 29 26.56 30 26.62 31 27.37 others
compound
0%
3%
5%
7%
10%
heptane, 2-methylcyclopentane, ethylcyclopentane, 1,2,4-trimethylcyclopentane, 1,2,3-trimethylcyclohexane, ethylcyclohexane, 1,1,3-trimethylcyclohexane, 1,1,2-trimethyl2-nonene, (E)nonane 1-ethyl-3-methylcyclohexane (c,t) pentalene, octahydro-2-methylcyclohexane, propyloctane, 2,6-dimethylheptane, 3-ethyl-2-methylundecane dodecane 1-tridecene tetradecane pentadecane dibenzofuran, 4-methylheptadecane octadecane nonadecane eicosane heneicosane docosane tricosane tetracosane hexacosane heptacosane octacosane
11.94 0.98 5.04 1.59 0.94 1.25 1.59 1.07 1.20 8.23 0.88 1.76 1.47 1.66 0.95 0.00 8.81 0.00 5.57 6.14 6.04 4.56 1.06 4.11 5.62 2.88 8.74 2.60 1.01 1.11 1.22 9.13 2.79
13.11 0.87 4.54 1.30 0.79 1.15 1.44 0.98 1.09 7.57 0.81 1.59 1.35 1.53 0.88 1.57 8.60 0.00 10.08 4.57 6.58 3.96 3.71 3.65 5.72 4.32 8.35 2.16 0.78 0.88 1.16 5.31 2.71
13.50 0.93 4.56 1.42 0.84 1.10 1.42 0.96 1.08 7.39 0.79 1.58 1.32 1.51 0.86 1.82 8.12 1.09 8.11 5.04 6.30 4.17 4.26 4.09 4.11 3.58 8.45 2.26 1.15 1.10 1.30 5.72 3.57
14.12 0.87 4.25 1.32 0.78 1.05 1.35 0.88 0.99 8.71 0.71 1.40 1.17 1.34 0.76 2.12 7.10 1.06 10.82 4.76 6.85 4.20 4.61 3.87 3.50 1.79 8.58 1.08 1.20 1.15 1.30 7.05 3.38
15.43 0.89 4.42 1.09 0.65 0.92 1.48 0.67 0.79 10.07 0.56 1.30 1.12 1.28 0.75 2.23 6.44 0.98 8.76 5.73 4.36 3.95 4.74 3.53 5.14 2.10 9.26 1.52 1.20 1.10 1.49 8.03 3.45
given in Table 9. It is observed that there are H2, CO, CO2, CH4, and some C2 and C3 hydrocarbons (C2H2, C2H4, C2H6, and C3H8), which account for 89% of the gas fraction. The contents of CO, CO2, and CmHn gradually increased, while CH4, H2, and the low heating value of the non-condensable gas slightly decreased, as the mass concentration of biomass was increased from 0 to 10%. Meanwhile, the comparison of experimental product yields to the calculated values of noncondensable gas is also presented in Table 9. In comparison to the calculated values, the contents of CO and CO2 in the experiments are slightly low, while the content of CmHn is higher than the calculated values. The contents of CH4 and H2 are similar between the experimental and calculated results. The above results were contributed to the reaction between CO, CO2, H2O, CmHn, and coke.12
compounds, methoxyphenolic compounds are not identified in the fractions (Table 7). The methoxyphenolic compound in the PSD tar is only 9.49%. Thus, it can be calculated that only 0.949% methoxyphenolic compound was obtained from coal blends with 10 wt % addition PSD carbonization. The ultimate analysis and lower heating value of the tar are given in Table 8. It can be seen that the contents of the carbon, nitrogen, and sulfur and the lower heating value of the tar decreased, whereas the hydrogen content and H/C in the tar increased when the mass concentration of the PSD is increased from 0 to 10%. This is the reason that PSD contains a high content of hydrogen, which can provide hydrogen to coal during carbonization. It is also found that the experimental values of the carbon content and lower heating value of the tar are higher than their calculated values. On the contrary, the hydrogen content and H/C in the tar are lower than their calculated values. The experimental values of the nitrogen and sulfur contents are consistent with their calculated values. Cocarbonization of coal and PSD favors producing low-molecularweight compounds and improving the quality of the liquid product, which was contributed to the hydropyrolysis and hydrogenation reactions during co-carbonization of coal/PSD. 3.4. Effect of PSD Amount on the Gas Composition. The effect of PSD addition on the compositions of noncondensable gas produced from coal/PSD co-carbonization is
4. CONCLUSION The addition of PSD has no significant influence on the coke quality indexes, such as M10, M40, CRI, and CSR, when the mass concentration of PSD is below 5%. Even 3% PSD addition can improve the coke quality, whereas the coke quality indexes are degraded gradually as the mass concentration of PSD is above 5%. The yields of tar and non-condensable gas are increased, whereas the coke yield is decreased, as the mass concentration 853
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Table 6. Detailed Compositions of the Aromatics in Tar mass fraction of biomass (%) peak
retention time
mass fraction 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 others
compound
of aromatics in the tar 4.78 toluene 6.81 ethylbenzene 7.09 p-xylene 7.31 cis-1-ethyl-3-methyl-cyclohexane 7.50 benzene, 1,3-dimethyl8.07 benzene, (1-methylethyl)8.65 benzene, propyl8.81 benzene, 1-ethyl-3-methyl8.94 benzene, 1,3,5-trimethyl10.16 indane 11.95 1H-indene, 2,3-dihydro-4-methyl12.66 naphthalene 13.02 benzene, 1,3-dimethyl-5-(1-methylethyl)13.41 benzene, 1,4-diethyl-2-methyl13.52 benzene, 1-ethyl-4-methoxy13.63 1H-indene, 2,3-dihydro-4,6-dimethyl13.83 1H-indene, 2,3-dihydro-4,7-dimethyl13.91 1H-indene, 1-ethenyl-2,3-dihydro14.08 benzene, 1,3-dimethyl-5-(1-methylethyl)14.11 4-hydroxy-3-methylacetophenone 14.31 naphthalene, 2-methyl14.55 naphthalene, 1-methyl14.68 1H-indene, 2,3-dihydro-1,1,3-trimethyl15.50 biphenyl 15.90 naphthalene, 2,7-dimethyl16.17 naphthalene, 1,6-dimethyl16.35 naphthalene, 1,3-dimethyl16.39 naphthalene, 1,4-dimethyl16.88 1,1′-biphenyl, 3-methyl16.99 1,1′-biphenyl, 4-methyl17.14 naphthalene, 2,3,6-trimethyl17.41 naphthalene, 1,4,5-trimethyl17.49 naphthalene, 1,4,6-trimethyl18.13 fluorene 18.28 fluorene, 4,4′-dimethylbiphenyl18.35 fluorene, 1,1′-biphenyl, 2-methyl19.10 1,4,5,8-tetramethylnaphthalene 19.33 benzene, (4,5,5-trimethyl-1,3-cyclopentadien-1-yl)19.45 9H-fluorene, 2-methyl20.39 anthracene 20.72 9H-fluorene, 2,3-dimethyl21.09 5H-[1]pyrindine-3,7-dicarbonitrile, 2-amino-4,6-dimethyl21.56 1H-cyclopropa[l]phenanthrene, 1a,9b-dihydro21.75 anthracene, 2-methyl21.86 1H-cyclopropa[l]phenanthrene, 1a,9b-dihydro21.91 phenanthrene, 1-methyl22.30 9,10-di(chloromethyl)anthracene 22.75 phenanthrene, 3,6-dimethyl22.96 di-p-tolylacetylene 23.02 9,10-dimethylanthracene 23.07 di-p-tolylacetylene 24.04 benzenamine, 4-[2-oxo-2-(1-pyrrolidinyl)ethoxy]24.59 pyrene, 1-methyl25.59 pyrene, 1,3-dimethyl-
of PSD is increased from 0 to 10%. Besides, the addition of PSD also causes the variation of components in tar and gas.
0%
3%
5%
7%
10%
44.07 4.40 14.01 30.00 0.22 9.21 0.49 0.19 0.69 0.10 0.59 0.61 1.99 0.00 0.11 0.50 0.12 0.36 0.29 0.26 0.42 5.60 0.57 0.37 0.39 3.85 1.33 0.81 0.31 0.67 0.55 2.18 0.70 1.41 1.46 0.57 0.56 0.32 0.39 1.93 0.88 1.70 0.45 1.50 0.54 0.62 0.40 0.32 0.66 1.02 0.70 0.28 0.35 0.89 0.36 0.80
42.86 4.10 12.82 28.13 0.21 8.61 0.46 0.18 0.65 0.10 0.34 0.57 1.79 0.00 0.11 0.42 0.11 0.29 0.26 0.24 0.61 5.65 0.54 0.40 0.43 4.26 1.44 0.87 0.35 0.82 0.66 2.61 0.89 1.66 1.79 0.75 0.75 0.41 0.40 1.93 0.91 1.84 0.48 1.72 0.70 0.78 0.53 0.32 0.74 0.97 0.68 0.29 0.54 1.42 0.51 0.96
42.42 4.10 13.08 27.93 0.28 8.57 0.46 0.18 0.64 0.09 0.34 0.56 1.78 0.00 0.12 0.43 0.11 0.31 0.23 0.26 0.74 5.67 0.55 0.35 0.48 4.28 1.43 0.90 0.38 0.78 0.60 2.58 1.06 1.74 1.75 0.66 0.69 0.29 0.43 1.98 0.83 1.71 0.00 1.83 0.68 0.81 0.55 0.29 1.15 1.19 0.76 0.37 0.61 1.59 0.58 0.24
41.93 4.10 13.28 28.04 0.20 8.58 0.45 0.18 0.67 0.11 0.25 0.52 2.04 0.11 0.12 0.44 0.13 0.33 0.00 0.28 0.94 5.83 0.66 0.37 0.67 4.18 1.35 0.86 0.35 0.83 0.66 2.60 0.94 1.64 1.75 0.72 0.73 0.38 0.44 2.14 0.92 1.20 0.47 1.53 0.47 0.56 0.40 0.00 1.10 1.06 0.67 0.85 0.56 1.40 0.77 0.17
40.06 3.79 12.04 25.79 0.18 7.85 0.44 0.19 0.84 0.16 0.00 0.00 1.94 0.11 0.14 0.40 0.14 0.32 0.00 0.32 0.94 5.38 0.73 0.33 0.74 4.39 1.45 0.87 0.34 0.91 0.83 2.69 1.25 1.79 1.99 0.81 0.84 0.42 0.47 2.41 1.55 1.40 0.53 1.92 0.61 0.73 0.50 0.44 1.28 1.12 0.77 0.40 0.68 1.73 1.17 0.94
Co-carbonization of coal and PSD favors producing lowmolecular-weight compounds and improving the quality of the 854
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Table 7. Detailed Compositions of the Oxygenated Compounds in the Tar mass fraction of biomass (%) peak
retention time
compound
oxygenated compound content in the tar 1 10.60 phenol, 2-methyl2 11.03 phenol, 3-methyl3 11.46 phenol, 2,6-dimethyl4 12.14 phenol, 2,4-dimethyl5 12.18 phenol, 2,3-dimethyl6 12.52 phenol, 3,5-dimethyl7 13.00 phenol, 2,3,5-trimethyl8 13.35 phenol, 2-ethyl-6-methyl9 13.58 phenol, 2-ethyl-4-methyl10 13.86 phenol, 3-ethyl-5-methyl11 14.03 phenol, 2,3,6-trimethyl12 15.04 2,3,5-trimethylanizole 13 18.57 [1,1′-biphenyl]-4-carboxaldehyde 14 19.67 1,4-methanonaphthalene, 1,4-dihydro-9-((1-methylethylidene)15 19.91 phenol, 3-(2-phenylethenyl)-, (E)16 20.06 8-dimethylaminonaphthalene-1-carbonitrile 17 21.99 dibutyl phthalate 18 26.05 phenol, 2,2′-methylenebis19 26.65 phenol, 2,4-bis(1-phenylethyl)20 27.02 1,2-benzenedicarboxylic acid others
Figure 6. GC−MS chromatograms of the aliphatic group in tar: (a) coal blends/10 wt % PSD and (b) reference coal blend.
0%
3%
5%
7%
10%
7.25 4.62 9.32 3.00 6.09 4.78 6.09 2.11 1.25 1.45 5.09 1.30 1.74 12.2 10.9 5.59 8.14 1.54 0.89 1.07 7.91 4.92
8.05 5.70 9.25 2.69 5.28 5.72 5.68 1.93 1.07 1.28 6.24 1.34 2.31 12.3 11.8 4.79 6.98 1.67 0.89 0.91 8.75 3.42
8.84 6.26 8.17 2.44 6.01 6.40 6.55 1.99 1.08 1.36 6.10 1.35 3.56 12.7 11.1 3.92 3.71 1.67 0.95 1.31 9.3 4.07
9.06 6.95 6.40 2.34 7.78 6.74 6.74 1.92 1.22 1.61 6.20 1.47 5.22 10.9 10.3 3.59 3.26 1.69 1.04 1.08 9.94 3.61
10.07 9.46 4.86 2.86 7.43 5.39 7.02 2.08 1.42 1.78 6.13 1.50 5.11 8.6 9.94 3.89 5.85 1.52 0.94 1.10 10.7 2.42
Figure 7. GC−MS chromatograms of the aromatic group in tar: (a) coal blends/10 wt % PSD and (b) reference coal blend. 855
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Table 8. Properties of the Tar Produced from Coal/PSD Co-carbonization C
H
N
S
lower heating value (MJ/kg)
H/C
PSD (%)
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
0 3 5 7 10 100
73.58 72.04 71.19 69.69 67.47 43.80
72.69 72.09 71.50 70.60 -
10.20 10.82 11.17 12.02 12.54 16.82
10.40 10.53 10.66 10.86 -
4.75 4.65 4.59 4.51 4.40 1.13
4.64 4.57 4.50 4.39 -
1.08 1.05 1.05 1.07 1.02 0.54
1.06 1.05 1.04 1.03 -
1.66 1.80 1.88 2.07 2.23 4.61
1.72 1.75 1.79 1.85 -
37.46 36.84 36.39 35.67 34.79 23.15
37.03 36.74 36.46 36.03 -
Table 9. Non-condensable Gas Compositions Obtained from Coal and Biomass Co-carbonization CO
CO2
CH4
CmHn
H2
low heating value
PSD (%)
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
experiment
calculation
0 3 5 7 10 100
4.41 4.90 5.25 5.87 6.17 25.8
4.41 5.05 5.48 5.91 6.55 25.8
1.91 2.51 2.88 3.34 4.42 27.7
1.91 2.68 3.20 3.71 4.49 27.7
25.69 25.24 25.04 25.08 24.87 17.51
25.69 25.44 25.28 25.12 24.87 17.51
2.65 2.76 2.78 2.80 2.84 1.37
2.65 2.61 2.59 2.56 2.52 1.37
54.42 53.97 53.06 52.43 50.96 19.64
54.42 53.38 52.68 51.99 50.94 19.64
17.46 17.26 17.11 16.87 16.65 12.61
17.46 17.32 17.22 17.12 16.98 12.61
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liquid product, which was contributed to the hydropyrolysis and hydrogenation reactions during co-carbonization of coal/ PSD.
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ASSOCIATED CONTENT
* Supporting Information S
Detailed characteristic information of coals 1−7. This material is available free of charge via the Internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was partly supported by Foundation of Hubei Key Laboratory of Industrial Fume & Dust Pollution Control (HBIK2012-05), Foundation of Hubei Key Laboratory of Coal Conversion and New Carbon Materials and Foundation of State Key Laboratory of Coal Combustion (FSKLCC1113).
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