The effect of acid washing on the pyrolysis products derived from avitrinite-rich bituminous coal
Journal of Analytical and Applied Pyrolysis 116(2015)142–151
Contents lists available at ScienceDirect
Journal of Analytical and Applied
Pyrolysis
j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j a a
p
The effect of acid washing on the pyrolysis products derived from a vitrinite-rich bituminous coal
Leon Roets a ,Christien A.Strydom b ,?,John R.Bunt a ,Hein W.J.P.Neomagus a ,Daniel van Niekerk b ,c
a
Coal Research Group,School of Chemical and Minerals Engineering,North-West University,Potchefstroom 2520,South Africa b
Chemical Resource Bene?ciation,North-West University,Potchefstroom 2520,South Africa c
Sasol Technology (Pty)Ltd,Box 1,Sasolburg 1947,South Africa
a r t i c l e
i n f o
Article history:
Received 25June 2015Received in revised form 23September 2015
Accepted 23September 2015
Available online 28September 2015
Keywords:Pyrolysis
Demineralization Acid washing Characterization South African coal
a b s t r a c t
Extensive characterization of the pyrolysis products,derived from raw and acid washed samples of a vitrinite-rich South African bituminous coal is reported.Pyrolysis experiments were carried out with use of a modi?ed Fischer Assay setup at 520,750and 900?C.Gaseous products were analyzed by gas chromatography (GC);tar yields by simulated distillation (SimDis),gas chromatography mass spectrom-etry and –?ame ionization detection (GC–MS and –FID)and size exclusion chromatography (SEC-UC),and the char yields by proximate,ultimate and Brunauer–Emmett–Teller (BET)CO 2adsorption analyses.The water and tar yields of the acid washed coal fraction (AW TWD)was found to be lower,whilst the gas yields were found to be signi?cantly higher than that of the raw coal fraction (TWD).The char yields were not signi?cantly affected by acid washing.Some of the differences in pyrolysis product yields can be related to increased porosity of the acid washed coal fraction.GC analysis of the derived pyrolysis gases indicated that the AW TWD derived gas contained higher yields of H 2,CH 4,CO 2,C 2H 4,C 2H 6,C 3H 4,C 3H 6and C 4s when compared to the gas derived from the TWD fraction,whilst the CO yield from the TWD fraction was greater at all ?nal pyrolysis temperatures.Analyses of the tar fraction by means of SimDis,GC–MS and –FID and SEC-UV indicated that the acid washed coal derived tars where more aromatic in nature,containing more higher boiling point components,which increased with increasing ?nal pyroly-sis temperature.On the other hand,the tars derived from the TWD coal contained lighter boiling point components with increasing ?nal pyrolysis temperature.The changes in the pyrolysis behavior of the bituminous coal are due to the removal of the mineral matter and also the in?uence of the acid washing process.This study con?rmed that acid washing of coal changes the pyrolysis products composition of a bituminous coal.
?2015Elsevier B.V.All rights reserved.
1.Introduction
Coal has a complex and heterogeneous chemical structure,con-taining various organic and inorganic species [1].The inorganic fraction consists of various minerals,of which more than 125have been identi?ed [2,3].Most of these minerals (approximately 100)are described as trace minerals (minerals present in a very low concentration with grain sizes smaller than 10?m),with only a few considered to be of signi?cance [3].The most common major minerals in bituminous coal are:quartz,kaolinite,gypsum,pyrite,calcite,illite and feldspars [4].The major mineral matter that is
?Corresponding author.Fax:+27182992350.
E-mail address:christien.strydom@nwu.ac.za (C.A.Strydom).
present in coal plays a signi?cant role during thermal conversion processes (https://www.sodocs.net/doc/7013550133.html,bustion,gasi?cation,pyrolysis,etc.).Coal prop-erties such as heating value,coal rank,reaction rate and ash content may be affected by the mineral matter content.The mineral mat-ter may also affect ?nal product yields due to the effect on the secondary pyrolysis reactions,as well as affect the composition of these products,as has been observed during tar production [5].
Pyrolysis is the initial step in most thermal coal conversion processes and it is largely dependent on the coal properties [6,7].Pyrolysis is the thermal process by which coal undergoes thermal decomposition and recombination reactions to form char,volatile liquids (containing tars,oils and aqueous compounds)and gaseous products in the absence of oxygen [1].The characterization of pyrol-ysis products of various coal samples has been reported extensively in literature [1,5–7].
https://www.sodocs.net/doc/7013550133.html,/10.1016/j.jaap.2015.09.016
0165-2370/?2015Elsevier B.V.All rights reserved.
L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)142–151143
Acid leaching or demineralization of coals is not used on a com-mercial scale,but it is an important technique to study the effect of mineral matter on coal behavior.In order to determine the effect of minerals on coal thermal treatment products,the coal behavior without these minerals present,should be investigated.Leach-ing agents used to remove mineral matter include NaOH,HCl,HF, H2SiF6,and HNO3[8].It has been found that hydrochloric acid(HCl) effectively reduces most mineral matter,whilst hydro?uoric acid (HF)is effective in dissolving the aluminum and silicon containing compounds[9].Pyritic compounds,however,are not effectively removed by these acids.Studies found that the use of solutions containing ferric ions or HNO3extraction methods can be utilized to remove associated pyrite from coal[10,11].
Manoj et al.[12]investigated changes in the structure of a Godavari coal sample after leaching with EDTA and HF.Rubiera et al.[13]reported an increase in volatile matter,oxygen and nitro-gen for a high-volatile bituminous coal char from the Harworth colliery in UK after leaching with a1:1mixture of HF/H2SiF6.An investigation into the in?uence of acid leaching procedures on a South African inertinite-rich bituminous coal,indicated that small amounts of oxygen and nitrogen containing species are incorpo-rated in the coal structure during a HF/HNO3leaching process,but not during a HCl/HF/HCl procedure[14].The remaining coal struc-ture contains increased amounts of N OH groups after HF/HNO3 leaching,whereas the COOH content was slightly increased after HCl/HF/HCl treatment[14].Reported studies focused on the char-acterization of the remaining coal sample and not on the in?uence of acid leaching on thermal treatment products.Limited studies have been undertaken to investigate the in?uence of acid leaching treatment of coal on the pyrolysis products.
Differences in coal type,acid leaching method and pyrolysis pro-cedure in?uence the results obtained.Most of the studies focused on the use of?ash pyrolysis or thermogravimetry to investigate pyrolysis products.Limited reports on the quantitative charac-terization of the pyrolysis products derived from a South African bituminous coal and the in?uence of acid washing on the pyrol-ysis products could be found in literature[14,15]In this paper a South African vitrinite-rich bituminous coal was subjected to an acid leaching process and a detailed characterization of the pyrol-ysis products,including the gas and tar yields,was conducted.The validity of using an acid washing procedure to produce a relatively mineral-free coal to investigate the in?uence of minerals on ther-mal processing of coal is discussed.
2.Material and methods
2.1.Coal samples:preparation and characterization
A washed and air dried sample from the South African Highveld coal?eld was obtained.The coal was a bene?ciated product,having a low ash content(<15wt%d.b.).The coal sample was milled and crushed to a particle size<75?m,divided into two representative fractions and sealed under a nitrogen atmosphere.The?rst fraction served as the raw coal sample,referred to as TWD,whilst the other fraction underwent acid washing and is referred to as AW TWD.
A hydrochloric(HCl)and hydro?uoric(HF)acid leaching pro-cess,as described previously,was followed[8].The analytical grade acids were obtained from MERCK.Five hundred grams(500g)of the coal sample was added to4L5mol dm?3(32wt%)concentrated HCl in a glass beaker and stirred for24h using a polyethylene coated magnetic stirrer.The liquor was removed by?ltration under reduced pressure.The insoluble solid fraction from the?l-tration stage was added to2.5dm3of29mol dm?3(48wt%)HF in a polyethylene beaker.The mixture was stirred for24h,after which the liquor was again removed by?ltration,and the HF insoluble fraction further leached in HCl using a step similar to the initial step.The liquor was separated by?ltration and the insoluble frac-tion was washed copiously using ultrapure water until the pH of the?ltrate was close to7.0.The acid insoluble solid was dried in a vacuum oven at80?C until constant weight.
Petrographic analyses,including vitrinite re?ectance and mac-eral composition,were carried out according to ISO7404:1999[16].
X-ray?uorescence(XRF)ash analysis was carried out according to the ASTM D4326method[17].For the mineral XRD analyses,the samples were dried overnight in a vacuum oven at80?C to remove surface moisture.The samples were prepared prior to analyses by a back loading preparation method.A McCrone micronising mill was used along with addition of20%Si to determine the amorphous content.XRD analysis was performed on a Phillips X’Pert PW1830 powder diffractometer.X’Pert Highscone software was used for phase identi?cation.The Rietveld method(Siroquant software) gave an estimation of phase amounts.For QEMSCAN(Quantitative Evaluation of Minerals by Scanning Electron Microscopy)analysis a representative sample was mixed with graphite and mounted in Araldite epoxy-resin.After the sample has cured it was polished to a diamond?nish of1?m and prepared by use of Carnauba wax. These samples were analyzed using a scanning electron microscope (SEM)to determine the mineralogical composition[18].
2.2.Pyrolysis experiments
Pyrolysis experiments were conducted using a modi?ed Fischer Assay setup as reported previously[19].The setup was modi?ed to accommodate temperatures up to900?C using stainless steel retorts,capable of measuring tar,char and water content and also to capture gas fractions(Fig.1).The Fischer Assay setup was oper-ated at a constant heating rate of6.2–6.3?C/min up to520?C,750?C or900?C,with a holding time of10min,at atmospheric pressure conditions.Fischer Assay preparation under ISO647is speci?ed at 520?C[20].The temperatures of750?C and900?C were selected as temperatures to study the effect of mineral matter on pyroly-sis products and composition.A temperature of900?C is generally considered to be at the end of the pyrolysis stage of coal,and therefore a good indication of the last pyrolysis product yields and composition.The temperature of750?C was chosen to represent the mid-stage of pyrolysis.The setup was purged with nitrogen before the pyrolysis experiments commenced to limit oxidizing reactions.
Condensable volatiles were captured in round-bottom?asks immersed in an ice/water mixture.Two gas washing stages(sol-vent scrubbers)using toluene were added in series to the outlet of the round-bottom?asks.The?nal gas fractions from the solvent scrubbers were captured in Tedlar?gas sampling bags for analy-sis.Water separation was done and yields determined as reported previously[19].
2.3.Gas analysis
Gas yields were determined by difference after quanti?cation of the char,tar and water yields after conventional Fisher Assay anal-yses.The gas yields were determined by using volume calculations along with compositional data for the derived gases.The gas prod-ucts were sampled in10L Tedlar gas sampling bags for the duration of the experiment.After completion of the experiment,the volume occupied by gas in the bags was measured.The pressure for the sys-tem was noted,and using of the ideal gas law,the GC results and the gas volumes,the weights of the produced gases were calculated.
The captured gas samples were analyzed in a SRI8610C Mul-tiple Gas Chromatograph(GC).The GC was operated with a hold time of7min at60?C,ramping up to280?C with a heating rate of15?C/min and holding time of20min.The thermal conductivity
144
L.Roets et al./Journal of Analytical and Applied Pyrolysis 116(2015)
142–151
Fig.1.Schematic diagram of Fisher assay setup with tar and gas traps.
detector (TCD)was operated at 25psi at a ?ow rate of 20cm 3/min He and 7psi at 10cm 3/min Ar.The ?ame ionization detector (FID)was set at 25psi and 20cm 3/min He,whilst the methanizer was used under H 2and air respectively at 20psi and 25cm 3/min,and at 5psi and 250cm 3/min.Calibration of the equipment was per-formed using gas standards and by evaluating the typical elution timesfor the expected gas product constituents.GC results were further converted to a g gas species/g coal (d.m.m.f.)value using
g i,j ?g
coal ,d.m.m.f.
=
wt .%i 100
G j
C g,d.m.m.f.
where i is the gas species,G j refers to the amount (g )gas derived from the coal at temperature j and C g refers to the amount of coal (g )on a dry,mineral-matter-free basis.
2.4.Tar analysis
Simulated distillation analyses (SimDis)were conducted according to the ASTM D2887standard method [19].The SimDis results were analyzed based on an average boiling point calcula-tion and evaluation of the mass loss curves,as described previously [19,20].The average boiling point is calculated using the following equation:
Average boiling point =(T 10+T 30+T 50+T 70+T 90)/5
where T 10,T 30,T 50,T 70and T 90are the temperatures at which 10,30,50,70and 90%tar mass loss occurred.
Further analyses of simulated distillation results were done based on division of the boiling point distributions into crude oil distillation fractions based on the method reported by Rand [21].Gas chromatography—mass spectrometry (GC–MS)analyses were performed on the tar samples using GC-FID (quanti?ca-tion)and GC–MS (peak identi?cation)techniques as previously described by Roets,et al.[19].It is noted that only semi-quantitative results were obtained from the GC-FID and GC–MS method.
Size-exclusion chromatography (SEC-UV)analysis of the derived tars were carried out with an Agilent 1100high-performance liquid chromatograph (HPLC)set at 80?C using
a
Fig.2.Typical SEC-UV chromatogram.
300mm long,7.5mm internal diameter PLgel mixed-E (Varian)GPC column for separation.1-methyl-2-pyrollidone (NMP)at a ?ow rate of 0.5cm 3/min was used as eluent [19].Data was analyzed using the HP 1100Data Analysis software.Fig.2presents a typical SEC chromatogram.The peak identi?ed between ～7and ～10min corre-sponds to material of molecular size and/or molecular composition unable to penetrate the porosity of the column packing [22].This peak was excluded in further calculations.SEC-UV results are com-pared based on heavy and light component areas as identi?ed in Fig.2.
2.5.Char analysis
Proximate analyses were carried out by use of the relevant stan-dards (moisture—ISO 11722:1999[23];Ash content—ISO 1171:2010[24];Volatile matter content—ISO 562:2010[25]and Fixed carbon content—determined by difference).Ultimate analysis was carried out according to ISO 29541:2010[26].The total sulfur con-tent was determined by IR spectroscopy according to ISO 19759:2006[27]
L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)142–151145 Table1
XRF Analysis results of raw(TWD)and acid washed(AW TWD)coal samples.
Species TWD wt.%(d.b.a)AW TWD wt.%
(d.b.a)Removal ef?ciency (%)
Al2O325.314.992.1
CaO11.58.889.7
Cr2O30.10.255.3
Fe2O39.639.045.3
K2O0.60.491.2
MgO 3.7 5.181.7
MnO0.10.196.3
Na2O0.6 1.275.0
P2O5 1.50.397.7
SiO235.9 5.198.1
TiO2 1.7 5.755.5
V2O50.10.259.7
ZrO20.10.545.2
Ba0.6 2.543.1
Sr0.7 1.768.0
SO38.214.376.5
Total/Overall ef?ciency10010086.6
a d.b.=dry basis.
Table2
Mineral XRD analysis results for the raw coal(TWD)and the acid washed coal(AW TWD)samples.
Weight%Removal ef?ciency(%)
TWD AW TWD
Amorphous content90.399.3–
Quartz 1.4–100.0
Kaolinite 4.9–100.0
Calcite0.4–100.0 Dolomite 1.60.193.8
Pyrite0.90.633.3 Aragonite0.2–100.0 Apatite,F-,0.1–100.0
TOTAL/OVERALL100.0100.092.8
BET CO2adsorption analyses were conducted on a Micrometics ASAP2010Analyser.The samples were dried overnight at80?C in a vacuum oven to remove excess moisture and the previously described procedures followed[28]
3.Results and discussion
3.1.Coal characterization
The vitrinite re?ectance range for the TWD coal occurred in the 0.5–1.0%distribution range.The random re?ectance value was cal-culated as0.74%,which classi?es the TWD coal as a Medium Rank
C bituminous coal.The TW
D coal was found to be vitrinite rich
(50.0vol.%m.m.b.),with a large inertinite(34.6vol.%m.m.b.)frac-tion.Liptinite content is low(7.0vol.%m.m.b)and typical for South African Permian-aged Gondwana land coals[4,15].The inertinite consisted mainly of reactive semifusinite and inert semifusinite, with small amounts of fusinite,secretinite and micrinite.
Mineralogical analyses include XRF ash(Table1),XRD(Table2) and QEMSCAN(Table3)analyses.The XRF ash analysis(Table1) indicates that the ash of the TWD fraction contained signi?cant amounts of SiO2,Al2O3,CaO,Fe2O3,SO3,MgO,TiO2and P2O5.For the AW TWD fraction,the species present(measured as oxides),in decreasing abundance,were:Fe2O3,Al2O3,CaO and TiO2.The most prominent minerals(Tables2and3)are calcite,dolomite,kaolin-ite,pyrite and quartz,consistent with previous results for South African coals[29].TWD coal was reported to contain17.4wt%min-eral matter,whilst the AW TWD coal fraction contained3.2wt% mineral matter as determined by QEMSCAN analyses.Pyrite(FeS2, related to Fe2O3in the XRF analysis),some quartz(SiO2)and some Table3
QEMSCAN analysis results of the raw coal(TWD)and the acid washed coal(AW TWD).
Area%Removal ef?ciency(%)
TWD AW TWD
Sulphates/Gibbsite0.810.0890.1
Pyrite 3.92 4.40–
Siderite0.160.00100.0
Calcite 2.280.0299.1 Dolomite 4.750.0299.6
Apatite0.680.0395.6
Kaolinite8.630.0599.4
Quartz 1.50.1888.0
Illite/Muscovite0.760.0198.7 Microcline0.330.00100.0
Rutile0.080.0450.0
Other0.50.78–
TOTAL24.4 5.6376.9
Table4
Pyrolysis product yields.
520?C
wt.%TWD a AW TWD a TWD b AW TWD b Water8.1 4.6––
Tar9.9 4.910.8 5.1
Char70.974.377.177.9
Gas11.216.212.217.0 TOTAL100.0100.0100.1100.0
750?C
Water8.5 4.6––
Tar8.2 5.89.0 6.1
Char66.770.072.973.4
Gas16.619.618.120.5 TOTAL100.0100.0100.0100.0
900?C
Water8.8 4.3––
Tar8.3 6.29.1 6.5
Char65.868.472.271.5
Gas17.021.118.722.0 TOTAL99.9100.0100.0100.0
a d.m.m.f.basis
b d.m.m.f.and water free basis
trace minerals were not successfully removed by the acid wash-ing procedure and the in?uence of pyrite on the pyrolysis products was excluded from this investigation.These results were similar to previously reported research[5,9].Overall mineral removal ef?-ciencies are86.6%,92.8%and76.9%from XRF,XRD and QEMSCAN analyses https://www.sodocs.net/doc/7013550133.html,parison of the XRF,XRD and QEMSCAN analyses highlights the need to use various methods to analyze coal mineral matter.
3.2.Pyrolysis product yields
Table4summarizes the pyrolysis product yields obtained for TWD and AW TWD fractions on an as determined basis dry,min-eral matter free basis(d.m.m.f.)and on a d.m.m.f.water free basis. The results are reported for95%con?dence intervals,based on four experimental repeats at each temperature for each coal fraction. All yields were found to be within the repeatability limits as set out in ISO647[21]The gas yields obtained from the AW TWD frac-tion are signi?cantly higher when compared to the TWD fraction and is consistent with previous?ndings[30].In previous studies the increase in gas yield due to acid washing was attributed to the fact that the minerals(and particularly their oxides responsible for gas formation in coal)are non-porous,thus the removal of min-eral matter is believed to increase its porosity[31].Due to higher porosity an increase in gas yield is expected.BET CO2adsorption
146L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)
142–151
Fig.3.BET CO2surface area(d.m.m.f.)results for the raw coal(TWD)and the acid washed coal(AW TWD)and their respective chars.
results(Fig.3)showed that the AW TWD chars has a higher surface area when compared to the TWD coal,con?rming this hypothesis. The gas yields are observed to increase with an increase in?nal pyrolysis temperature,with a large difference observed between the yields at520?C and750?C,consistent with previous?ndings, indicating that the second pyrolysis stage(>450?C)was found to be dominated by increasing gas yields[17]The tar yield from the TWD fraction decreased with an increase in pyrolysis temperature from 520?C and750?C,in accordance with previous?ndings[31],whilst that of the AW TWD fraction is observed to increase within the same temperature range.A change in the physical appearance of the derived tars was observed after acid washing,i.e.tars derived from the TWD fraction were black and gummy in appearance,whilst tars derived from the AW TWD fraction were light to dark brown and powdery.The tar yields were lower after acid washing,i.e.±50% lower for the experiments carried out up to520?C,±30%lower for the experiments carried out up to750?C,and±25%lower for the experiments carried out up to900?C.This result is consistent with previous?ndings[30–32].The reduction in tar yield after acid washing is attributed to hydrogen transfer occurring between the liquid and solid phases during pyrolysis.The tar yields produced during pyrolysis,are highly dependent on hydrogen transfer reac-tions.Inorganic matter,(such as minerals),ensure higher hydrogen transfer,thus stabilizing the free radicals formed during thermal shock,causing increased product release and the minimization of re-solidi?cation to char,thus forming more tar products[31,33]. In the absence of inorganic matter,the free radicals are not effec-tively capped and stabilized and the free radicals thus recombine to form char[31,34,35].Sert et al.[32]determined that the decreas-ing amounts of liquid products and increase in gas yields after acid treatment with HCl can also be attributed to more cracking of liquid products.
Char yields(calculated on a d.m.m.f.and water free basis)at520, 750and900?C are less than1%larger for the AW TWD in compar-ison to the TWD coal sample and the differences are considered very small and consistent with previous results[30].The differ-ences observed for the char yields(calculated on a d.m.m.f.and water free basis)between520?C and750?C are slightly smaller for the TWD fraction than the AW TWD fraction(4.2wt%vs.4.5wt%), whilst between750?C and900?C,the difference is1.9wt%for AW TWD,and0.7wt%for the TWD fraction.This is in accordance with observations made by other authors,who stated that a small shift in the pyrolysis range was observed after acid washing[36].
The water yield(calculated on a d.m.m.f.basis)is observed to remain constant for the AW TWD fraction,whilst a small
increase Fig.4.H2yields for the raw coal(TWD)and the acid washed coal(AW TWD).
is observed with an increase in?nal pyrolysis temperature for the TWD fraction.This different behavior can be related to the removed minerals;i.e.kaolinite which contains endothermic water,released in the temperature range of450–650?C[37,38].Other minerals such as dolomite and calcite also in?uence water yields[39],while some tar precursors are also thought to be a source of water vapor [40].
3.3.Gas analysis
Gas analysis results were normalized on a N2and O2free basis. The most common gases evolved at all temperatures for both frac-tions include H2,CO,CO2,CH4,C2s and C3s.The C2s and C3s identi?ed include:ethane(C2H6),ethylene(C2H4),propane(C3H6) and propylene(C3H4),as well as C4s(butane,iso-butane,n-butane, butadiene,etc.).Of the other gases,ethylene and ethane were most prominent.The C4s are only identi?ed in small amounts in some cases.The results obtained for the four most prominent gases(H2, CO,CO2and CH4)are discussed.
Both the TWD and AW TWD fractions showed an increase in H2yields with an increase in?nal pyrolysis temperature(Fig.4), consistent with previous?ndings[41].Standard deviations are indicated by error bars in the?gures.From Fig.4it can be observed that the H2yield of the AW TWD fraction was higher at all tem-peratures when compared to that of the TWD fraction.The higher H2yield obtained for AW TWD gas is consistent with the lower tar yield,indicating that more cracking of tar is occurring at lower tem-peratures for the AW TWD fraction[41,42].It may also be attributed to lower hydrogen transfer of the AW TWD fraction[31,33,34].The H2gas formed at the lower temperatures may also result from the bond stabilization after scission of weak aliphatic(C H)bonds[36].
Both the TWD and AW TWD fractions showed an increase in CO yield with an increase in?nal pyrolysis temperature(Fig.5). For the AW TWD fraction,no signi?cant increase in the amount of CO is observed between750?C and900?C.The higher yield of CO observed for the TWD fraction can be regarded as signi?cant at all ?nal pyrolysis temperatures.The higher CO yields observed for the TWD fraction is indicative of the presence of more oxygen function-alities within the coal and may also be due to catalytic in?uences of minerals[41].
Fig.6indicates an increase in CO2yield for the TWD fraction with an increase in pyrolysis temperature up to750?C,but no signi?cant difference between the yields produced for the750?C and900?C experiments.This initial increase in CO2yield can be attributed to the decomposition of the carbonate mineral species,calcite and https://www.sodocs.net/doc/7013550133.html,parison of the CO2yields obtained from the TWD coal
L.Roets et al./Journal of Analytical and Applied Pyrolysis 116(2015)142–151
147
Fig.5.CO yields for the raw coal (TWD)and the acid washed coal (AW
TWD).
Fig.6.CO 2yields for the raw coal (TWD)and the acid washed coal (AW TWD).
and that of AW TWD coal indicate that the CO 2yield of the AW TWD fraction is higher than that of TWD fraction at all temperatures.The difference may be related to increased crosslinking within the AW TWD fraction,which would inhibit tar formation (as observed for AW TWD)and lead to increased CO 2yields.The cracking and reforming of light hydrocarbons present in tar will contribute to the CO 2and CO yields [41].In the case of the AW TWD fraction,it seems as if most of this cracking and reforming of light hydrocarbons in the tar may be due to CO 2,while for the TWD fraction the process leads to more CO being formed.The water gas shift reaction may be catalyzed in the TWD fraction,and may cause shifts towards the CO side,thus partially converting some of the formed CO 2–CO.
An increase in CH 4yield is observed for the AW TWD fraction at all ?nal pyrolysis temperatures (Fig.7).For the TWD fraction,an increase in CH 4yield is observed up to 750?C,after which the CH 4yield decreases signi?cantly.The CH 4yield of the AW TWD coal is also observed to be much higher than that of the TWD fraction at all temperatures.The presence of CH 4at experimental temperatures of up to 520?C is indicative of the decomposition and/or hydrogena-tion of the methyl side chains on the parent coal or formed tars [43].The formation of CH 4at increased temperatures is attributed to the cross-linking reactions of coal macromolecules and/or the cracking of saturated hydrocarbons [43].More crosslinks thus seem to have formed during the pyrolysis process in the acid washed coal sam-ple than in the raw coal sample,as was also argued earlier for the increased CO 2and decreased CO yields.Alkylation reactions due to decomposition of primary tars above 600?C has also been found
to
Fig.7.CH 4yields for the raw coal (TWD)and the acid washed coal (AW TWD).
be a source of CH 4[41],thus suggesting that the lower tar yields observed for the TWD coal at increased ?nal pyrolysis tempera-tures,may be due to alkylation reactions.The decrease in CH 4yield for the TWD sample at higher temperatures (>750?C)may also be due to methane being catalytically reformed to CO and H 2.
3.4.Tar analyses
The initial starting boiling points of all derived tars were found to be 112?C.All compounds with lower boiling points were already removed during the water and toluene removal stages.The ?nal boiling point for all derived tars ranged around 525?C,with a weight averaged boiling point (WABP)con?ned to the region of 318–354?C for all tars.No signi?cant difference was seen regarding these parameters with an increase in ?nal pyrolysis temperature,or after acid washing.
The results from the simulated distillation cut fractions (based on crude oil re?ning),are summarized in Table https://www.sodocs.net/doc/7013550133.html,parison of the tars derived for the TWD fraction indicate that with an increase in ?nal pyrolysis temperature that more of the lighter components are present due to thermal cracking.For the AW TWD tar the inverse is observed,i.e.a decrease in the percentages of the lighter frac-tions is observed with an increase in temperature.From Table 5it is evident that the TWD fraction yields more tar in every crude tar fraction,and it is also clear that the AW TWD fraction yields more components with a higher boiling point with increasing ?nal pyrolysis temperature.The increase in tar yield observed with an increase in ?nal pyrolysis temperature for the AW TWD fraction can almost wholly be attributed to the light vacuum gas oil frac-tion (343–455?C),with a small increase also in the distillate fuel (277–343?C)fraction.The shift to lower boiling point components for the TWD fraction is mainly due to a reduction in the light-and heavy vacuum gas oil fractions,whilst the kerosene fraction shows an increasing amount at a ?nal pyrolysis temperature of 900?C.
The GC–MS analysis of the derived tars provides insight into the low molecular weight hydrocarbon species with boiling points below 300?C.From the SimDis results it is evident that a large fraction of the tar (～60%)will not be identi?ed by the GC–MS instrument.All results (Table 6)are reported within a 95%con-?dence interval,as calculated from standard deviation values for four repeated experiments.The various compounds identi?ed by GC–MS were classi?ed into various molecular families (as summa-rized in Table 6).Mixed aliphatic and aromatic compounds were assigned to compounds that exhibit both aromatic and aliphatic mass peaks in the mass spectra (either compounds with both
148L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)142–151
Table5
Simulated distillation(SimDis)analysis results for the tars derived from the raw coal(TWD)and the acid washed coal(AW TWD).
Boiling point range?C TWD AW TWD
wt.%tar g/100g coal(d.m.m.f.)wt.%tar g/100g coal(d.m.m.f.)
520?C
Medium naphtha79–1210.50.1 1.00.1
Heavy naphtha121–1917.60.810.20.5
Kerosene191–27723.2 2.529.6 1.5
Distillate fuel oil277–34321.2 2.321.4 1.1
Light vacuum gas oil343–45534.4 3.728.6 1.5
Heavy vacuum gas oil455–56613.1 1.49.20.5
750?C
Medium naphtha79–121 1.00.1 1.00.1
Heavy naphtha121–1918.10.78.00.5
Kerosene191–27722.2 2.026.0 1.6
Distillate fuel oil277–34321.2 1.920.0 1.2
Light vacuum gas oil343–45533.4 3.031.0 1.9
Heavy vacuum gas oil455–56614.1 1.314.00.9
900?C
Medium naphtha79–121 1.70.20.80.1
Heavy naphtha121–1919.30.8 5.20.3
Kerosene191–27728.0 2.522.0 1.4
Distillate fuel oil277–34322.0 2.023.0 1.5
Light vacuum gas oil343–45528.0 2.535.0 2.2
Heavy vacuum gas oil455–56611.0 1.014.00.9
Table6
GC–MS and GC-FID results for the tars derived from the raw coal(TWD)and the acid washed coal(AW TWD).
TWD AW TWD
wt.%
520?C
Aliphatic compounds 5.1–5.4 4.9–5.6 Alkyl-Benzenes0.8–1.10.5–1.5 Alkyl-Phenols36.6–39.439.3–40.5 Aromatic ethers and esters0.4–2.1 1.1–1.7 Alkyl-Indenes0.1–0.10.0–1.1 Alkyl-Naphthalenes 2.5–2.6 2.8–3.3 Poly-aromatic hydrocarbons0.2–0.20.1–0.2 Nitrogen heteroatoms 5.7–6.5 4.6–5.7 Mixed aliphatic and aromatic compounds43.6–47.542.1–45.7 750?C
Aliphatic compounds 4.8–5.0 4.9–5.9 Alkyl-Benzenes0.9–1.50.3–1.0 Alkyl-Phenols40.5–45.137.0–39.0 Aromatic ethers and esters0.5–1.10.3–1.1 Alkyl-Indenes0.0–0.10.0–0.1 Alkyl-Naphthalenes 2.9–3.1 2.9–3.1 Poly-aromatic hydrocarbons0.0–0.30.1–0.3 Nitrogen heteroatoms 5.7–6.6 4.8–6.6 Mixed aliphatic and aromatic compounds38.3–43.644.9–47.7 900?C
Aliphatic compounds 4.7–5.2 5.2–6.4 Alkyl-Benzenes 1.3–2.20.3–0.5 Alkyl-Phenols35.7–39.836.4–37.2 Aromatic ethers and esters 1.7–3.20.3–0.8 Alkyl-Indenes0.1–0.10.0–0.0 Alkyl-Naphthalenes 2.8–2.90.9–2.9 Poly-aromatic hydrocarbons0.2–0.30.1–0.2 Nitrogen heteroatoms 4.9–6.3 5.2–5.7 Mixed aliphatic and aromatic compounds42.4–46.349.0–49.9 aromatic and aliphatic constituents and/or co-elution of aromatic or aliphatic compounds).
No signi?cant differences in the yields of aliphatic compounds and mixed aliphatic and aromatic compounds with boiling points less than300?C were observed with an increase in?nal pyrolysis temperature for the TWD tar fraction.The mixed aliphatic and aro-matic components for the AW TWD fraction do however show a tendency to increase with an increase in?nal pyrolysis tempera-ture.The yields of mixed aliphatic and aromatic components for the AW TWD fraction are higher than that of the TWD fraction for the 750?C and900?C experiments.The similar results of the amounts of aliphatic compounds are indicative that most have formed at temperatures below520?C for both fractions,and therefore no sig-ni?cant change is observed at the higher temperatures.Secondary tars,derived at temperatures greater than600?C will be more aro-matic in structure due to decomposition of the thermally unstable primary tar compounds to gas and other tars[44,45].
The increase in alkyl-benzene,alkyl-indene and alkyl-naphthalene families with an increase in?nal pyrolysis temperature observed for the TWD derived tar,is attributed to the severity of pyrolysis at increased temperatures and the cleavage of more aromatic bridge structures[6,46].The yields of alkyl-substituted benzenes and naphthalenes could have been larger,but decomposition to CH4and parent aromatics,i.e.ben-zene and naphthalene,could have attributed to the increase in CH4 yields observed from the gas analyses.In the case of the AW TWD tar,this seems likely and therefore explains the higher CH4yields observed,as the yield of alkyl-benzenes decreased for the AW TWD fraction with an increase in?nal pyrolysis temperature.No signif-icant change is observed in alkyl-indene and alkyl-naphthalene yields with increasing?nal pyrolysis temperature.
The alkyl-phenol compounds were found to be the most promi-nent molecular family in the aromatic spectrum,in accordance with previous studies[23,45,46].The phenolic nature of the tars is related to the most prominent maceral found in the TWD and AW TWD fractions,namely vitrinite[36,47].The alkyl-phenol com-pounds decrease with an increase in?nal pyrolysis temperature for the TWD derived tar.It is expected as the oxygen function-alities are eliminated from the coal structure with an increase in pyrolysis temperature[46].The AW TWD derived tars indicate an increase in these compounds with an increase in?nal pyrolysis temperature and the results can be related to the difference in CO yields observed for the two coals.These species have been found to decompose via decarboxylation to form CO and cyclopentadiene (C5H6)at temperatures ranging between665?C and865?C[45,46].
TWD coal tar has lower yields of alkyl-phenol with an increase in?nal pyrolysis temperature,thus forming CO due to secondary decomposition reactions,whilst the AW TWD tar shows increased yield,with no signi?cant change in CO yield between750?C and 900?C.It was also found that CH4can take part in the formation of
L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)142–151149 Table7
SEC-UV results for the chars derived from the raw coal(TWD)and the acid washed coal(AW TWD).
TWD AW TWD
520?C750?C900?C520?C750?C900?C
Light components(Area%)31.933.933.038.937.535.3 Heavy components(Area%)68.166.167.061.162.564.7
Table8
Proximate and ultimate analysis results of the chars derived from the raw coal(TWD)and the acid washed coal(AW TWD).
TWD AW TWD
wt.%
Coal520?C750?C900?C Coal520?C750?C900?C Proximate analysis(As determined)
Inherent moisture 4.20.80.8 1.0 2.30.80.70.8 Ash14.319.322.022.1 2.0 1.9 2.0 2.0 Volatile matter(VM)31.49.1 3.4 2.132.77.3 3.0 1.6 Fixed carbon(FC)—by difference50.170.873.874.863.089.994.295.6 TOTAL100.0100.0100.0100.0100.0100.0100.0100.0 Proximate analysis(d.m.m.f.)
Volatile matter(VM)38.511.4 4.4 2.734.17.6 3.1 1.7 Fixed carbon(FC)—by difference61.588.695.697.365.992.496.998.3 TOTAL100.0100.0100.0100.0100.0100.0100.0100.0 Ultimate analysis(d.m.m.f.)
Carbon79.189.395.396.680.390.994.595.3 Hydrogen 4.7 2.8 1.20.1 4.7 2.7 1.20.3 Nitrogen 2.1 2.8 2.2 1.8 2.2 2.8 2.6 2.1 Oxygen—by difference12.7 4.00.10.111.5 2.80.9 1.6 Total sulfur(IR spectroscopy) 1.4 1.2 1.2 1.3 1.30.80.80.6 TOTAL100.0100.0100.0100.0100.0100.0100.0100.0
phenols.The presence of free radicals such as?CH3can lead to cresol and alkyl-substituted phenol formation during the CO2reforming methane process,resulting in a decrease in the ratio of phenols to alkyl-substituted phenols[48,49].The only signi?cant difference is observed at the?nal pyrolysis temperature of900?C,with the AW TWD fraction producing more alkyl-substituted phenols.At this temperature the CH4yield for the AW TWD fraction further increased,whilst for the TWD fraction a decrease was observed in the CH4yield.
No trend is observed in the amounts of aromatic ethers and esters with an increase in?nal pyrolysis temperature for the TWD derived tars,but for the AW TWD derived tar a decrease in these compounds is observed with an increase in?nal pyrolysis tempera-ture between520?C and900?C.For the poly-aromatic hydrocarbon (PAH)group,there is an increase observed for the tars derived from TWD at a?nal temperature of900?C.This increase in PAH yield with an increase in?nal pyrolysis temperature is in accordance with previous?ndings[41,46].The AW TWD derived tars showed no signi?cant change in PAHs with an increase in?nal pyrolysis temperature.For the nitrogen heteroatoms group,no signi?cant change can be reported for both coal tars.
Comparison of the tars derived from TWD and AW TWD,indi-cated that the tars show good comparison for the520?C and750?C experiments for all families except for the alkyl-indenes and nitro-gen heteroatoms.For the900?C experiments,there is variation between most of the groups.In the case of the alkyl benzenes,the AW TWD tar contains signi?cantly less of these compounds.For the alkyl–phenols the AW TWD tar contains80.5–84.2wt%,whilst the TWD tar has72.4–76.4wt%.Comparison of the aromatic ethers and esters families indicate that a larger fraction of these compounds were present in tars derived from the TWD coal.The alkyl-indenes are a small fraction of the analyzed tar,yet the TWD derived tars do however show higher yields of alkyl-indenes.More PAHs were present in the TWD fraction derived tars than in the AW TWD derived tars.This result can be related to the higher gas yields,i.e.gases such as C2H4in the case of the AW TWD coal,which may indi-cate increased cracking of long-chain hydrocarbons[50].Regarding the alkyl-naphthalene group,the AW TWD derived tars contained more of these components for the520?C and750?C experiments. At900?C,there is,however,no signi?cant difference observed regarding the alkyl-naphthalene molecular family.The AW TWD derived tars produced less nitrogen heteroatom compounds for the 520?C experiments,than for the TWD derived tars.
In Table7the SEC-UV results for the various derived tars are summarized.For the TWD derived tars,only a small increase in light components is observed with an increase in temperature,consis-tent with previous?ndings[23,38].It is possible that at increased pyrolysis temperatures,that the increased H2yield assists in the degradation of larger tar molecules through extensive cracking [22].At lower pyrolysis temperatures it is possible that the molecu-lar mass of the tars may increase due to hydrogenation or chemical recombination reactions,which can alter the molecular form from relatively tight coiled structures to more linear open ones[51].In the case of the AW TWD derived tars it can be observed that with increasing?nal pyrolysis temperature that there is a shift to the heavy components.Recombination of the tar molecules are spec-ulated to take place.The higher light component fractions from the SEC-UV results at520?C,750?C and900?C(Table7),observed for the AW TWD derived tar in comparison to the TWD tar can be related to the higher H2yields for the AW TWD sample,especially at the experimental temperature of520?C,where a large difference in H2yield was observed between the two coal samples.
3.5.Char analyses
From the proximate analyses of the chars,(Table8),systematic trends during coal pyrolysis can be observed—i.e.the volatile mat-ter(d.a.f.)decreases,whilst the?xed carbon content increases.This increase in the?xed carbon content and decrease in volatile mat-ter content of the chars with increasing temperature is typical of a
150L.Roets et al./Journal of Analytical and Applied Pyrolysis116(2015)142–151
pyrolysis process[7].The decrease in volatile matter is most promi-nent up to520?C,with smaller differences occurring between 520?C and750?C,and even a smaller change occurring between 750?C and900?C for both fractions.The release of volatiles is most signi?cant during the primary pyrolysis stage(up to690?C)[42]. At temperatures above690?C,the char to gas reactions will be the most prominent pyrolysis process.For the AW TWD fraction, the ash content remains approximately2.0wt%.Pyrite will form pyrrhotite,and?nally troilite(FeS)under the pyrolysis conditions [3]
With regards to the ultimate analyses results,it is evident from Table8that the hydrogen,oxygen and nitrogen contents for both char samples decrease with an increase in?nal pyrolysis temper-ature,whilst the carbon content increases.The sulfur content is observed to remain relatively constant at all pyrolysis tempera-tures for the TWD fraction and chars,where only a small decrease in sulfur content is observed.The decrease observed in the sulfur content of the AW TWD derived chars is however,much larger.It is possible that the acid washing process liberated some of the sulfur, which led to easier removal during pyrolysis than was the case for the TWD coal.Chen et al.[52]stated that mineral matter present in the coal structure may trap sulfur,and therefore lower sulfur yields in chars may be observed after acid washing.With regards to the oxygen content,the decrease is more signi?cant in the case of the AW TWD fraction when compared to that of the TWD fraction,this relates to the higher CO2yield derived from the AW TWD coal.
Fig.3shows variation in the BET surface areas of the TWD and AW TWD coal samples at the various experimental tempera-tures.Both coal fractions showed increased BET surface areas with increase in?nal pyrolysis temperature up to750?C,consistent with previous?ndings[3,28].The decrease in surface area after 750?C has been attributed to thermal annealing and the increased graphitic nature of the samples at higher pyrolysis temperatures [28].
4.Conclusions
The effect of acid washing on the pyrolysis product yields and composition of these products derived from a vitrinite-rich South African coal was investigated.The water and tar yields of the acid washed fraction(AW TWD)was found to be lower,whilst the gas yield was found to be much higher than that of the coal fraction (TWD).The char yields were unaffected by acid washing.GC anal-yses of the derived pyrolysis gases indicated that the AW TWD derived gas contained higher yields of H2,CH4,CO2,C2H4,C2H6, C3H4,C3H6and C4s when compared to the gas derived from the TWD fraction,whilst the CO yield from the TWD fraction was higher at all?nal pyrolysis temperatures.Analysis of the tar fraction by means of SimDis,GC–MS and–FID and SEC-UV indicated that the AW TWD derived tars where more aromatic in nature,con-taining more heavier boiling point components,which increased in amounts with increasing?nal pyrolysis temperature.On the other hand,the tars derived from the TWD coal contained lighter boiling point components with increasing?nal pyrolysis temper-ature.More crosslinks seem to have formed during the pyrolysis process in the acid washed coal sample than in the raw coal sample.
The thorough characterization of the pyrolysis products pro-vided valuable information to determine the effect of acid washing on the products formed during a pyrolysis process.Results indi-cate that the pyrolysis products are in some cases in?uenced to a large extent by acid washing of coal,and that the produced prod-ucts could both be due to the decreased mineral matter content and a change in the chemical and physical structure of the coal. The use of acid washing to investigate the effect of mineral mat-ter on coal thermal behavior should thus be applied with caution. Clear indication,however,exists that the mineral matter in?uences the composition of the various products formed during pyrolysis of coal and in some cases the mineral matter seems to catalyze spe-ci?c reactions,such as the water shift reaction and reforming of CH4.
Acknowledgements
The authors gratefully acknowledge the assistance from SASOL R&D staff for assistance with the analysis of the tar samples.Spe-cial reference is made of Mr.Ben Ashton for the XRD analysis.Mr.
A.Kleynhans is acknowledged for his input regarding the pyrol-ysis experiments.The work presented in this paper is based on the research?nancially supported by the North-West University and the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa(Coal Research Chair Grant Nos.86880,UID85643, UID85632).Any opinion,?nding or conclusion or recommendation expressed in this material is that of the author(s)and the NRF does not accept any liability in this regard.
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on the contrary的解析
On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.
恰恰相反，非常刺激。 https://www.sodocs.net/doc/7013550133.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.sodocs.net/doc/7013550133.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.sodocs.net/doc/7013550133.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.sodocs.net/doc/7013550133.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.sodocs.net/doc/7013550133.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.sodocs.net/doc/7013550133.html,
英语造句
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
学生造句--Unit 1
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
英语句子结构和造句
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
六级单词解析造句记忆MNO
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
base on的例句
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
(完整版)主谓造句
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
初中英语造句
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
The Kite Runner-美句摘抄及造句
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
翻译加造句
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
改写句子练习2标准答案
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
用以下短语造句
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
英语造句
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品