Pyrolysis of Huadian oil shale by electrical heating on different heating rates

Global Geology, 15(2): 120-125(2012)doi:10. 3969/j. isn. 1673-9736. 2012. 02.05 ;Article ID: 1673-9736(2012 )02-0120-06Pyrolysis of Huadian oil shale by electrical heatingon different heating ratesG. Roland Nguimbi, sUN Youhong and LI QiangCollege of Construction Engineering, Jilin Uniersity, Changchun 130026，ChinaAbstract: The eletrical heating experiments on oil shale sample from Huadian of Jjin were carried out by thepyrolysis method at three different heating rate2 C/ min, 5 C/ min and 10 C/ min in the temperature range of30 C -750 C. Ileating rate 2 C/ min is considered low, while intermediale one covers the range 5 C/minand high heating rate is 10 C/ min. The contolling parameters studied were the final pyrolysis temperature andthe infuence of the heating rale as well as type. The heating rate has an important effect on the pyrolysis of oilshale and the amount of residual carbon obtained therefore. It is found that increasing the heating rate and py-rolysis temperalure also inereases the production of oil and the total weight loss. Higher heating rates resulted inhigher rates of accumulation. The rate of oil and water collection passed through the maximum of diferent heat-ing raltes at different pyrolysis temperatures. Heating rate afcted density, oil conversion and oil yield.Key words: oil shale; pyrolysis; electrical heating; Huadian; JjinHascakir & Akin, 2010). 'The main constituent of the1 Introductionoil shale is kerogen; Kerogen is a complex substanceTo ensure current energy needs and meets futureconsisting of large molecules of carbon and bhydrogenexpectations, new techniques for efficient use of un-with nitrogen, sulphur and oxygen atoms introducedconventional resources, exploration of new reserves ,into the molecule. The heating valuc of oil shalc isand evaluating the potential altermalives have to behighly variable, but in most cases is substantially lessconsidered together ( Hascakir & Babadagli, 2008).than 3000 kcal/kg. Comparing to other traditional sol-Oil shale is one of the altemative fossil fuel resources ,id fuels， the heating value of oil shale is limitedand one of the most promising sources of energy in the(Steiger, 2007 ). When shale particles are heated toworld with large deposits situated in almost all the .about 450C，the kerogen starts to decompose andcontinents. Its energy capacity is 2.5 times than thatpartially vaporize, leading to final products that, atof coal and 30 times that of petroleum ( Gersten elroom temperature, consist of gas, oil, and residualal. , 2000).carbon. For the design of equipment to obtain oil fromIn the literature, the kinetics of the thermal de-shale, it is neccssary to know the rate of decomposi-composition of various oil shale from dillerent regionstion ( Torrente & CalaAn, 2001; Lozano et al. ,of the world has been investigated and various sugges-1978) proposed the new kinetic model for oil shaletions as to the decomposition mechanisms have beenpy中国煤化工:1).reported (Li & Yue, 2004; Fermandez et al. , 1978;YHCNMHGReceived 20 February 2012, accepted 20 March 2012Pyrolysis of Huadian oil shale by electrical heating on different heating rates121350-450C>oil + gas +cokeactions of kerogen and bitumen. Kerogen is an insolu-kengen-+bitumen :275 -365C” 3450 polyme260 oiltosble organic component of shale ( Zainal et al. ，2006). indicated the temperature at which kerogen is(1)released as has been used in the model. The elemen-Oil shale is a complex mixture of kerogen andtal analysis of the samples were perforned using Fis-wide range of minerals. Therefore ，the thermal degra-cher Assay and results are summarized in Table 2.dation of oil shale is too difficult to be demonstratedThe table lists the values along with the standard devi-by one simple chemical reaction. Oil shale distillationations.takes place up to 230 9C，the cracking and viscosity2.2 Experimental setup and procedurereduction come between 270 C and 400 C and pyrol-The experiments were conducted with a setupysis of oil shale generally starts between 450 C andthat consists of a iron-steel cylindrical body with an550 C. 'The 0il shale behavior during pyrolysis isinner diameter of 25 cm and beight of 35 cm that hou-considered to be cormplicated because the shale is ases the samples. In the top of the cylindrical body wascomplex mixture of kerogen and wide range of miner-inserted two stem of healers ( 1000 W)，and thisals. Also, the oil produced by pyrolysis is the resultheater was connected to a temperature controller to in-of various chemical and physical reactions occuringcrease the temperature of the system. The tempera-together. The only way to produce oil from this oiltures were controlled to obtain the desired retortingshale is to reduce oil viscosity and that is best accom-temperature and monitored by digital temperature con-plished by heating these resources up to 450 Ctroller. A temperature sensor was placed ( inserted )which is known as the pyrolysis process, also as thefrom the top side of the rctort to the middle point ofway decormposition of the kerogen. 0il retorting canthe oil shale sample at the center, and connected tobe considered as the most effective method for extrac-the temperature controller to record temperature valuesting oil from oil shale. The easiest way to increase thecontinuously. 'Then, the sample holder was placed inefficiency of this method is to increase the thermalanother cylindrical cell, which has 45 cm height andconductivity of the system or increase the reduction of35 cm inner diameter. To minimize the heat losses,the oil viscosity.he space between two cylinders was flld by crushedDuring the pyrolysis of oil shale, qwany reactionsperlite show as Figs.1, 2.take part, like the distillation , visbreaking and crack-By use the controller and the band heater, thing reactions associated with the decomposition of ker-temperature of the system could be increased to de-ogen and decomposition of rock can take place also af-sired temperatures (Fig. 1). This installation is capa-ter reaching necessary temperatures.ble of simultaneous mass evolution and heat flow2 Experimental equipment and setmeasurements as function of time and temperature.The eylindrical body was piereed with two pipes, onepto the upper side which recovers gas rand the other on2. 1 Samplesthe underside that can recover the oil by simple steamOil shale samples investigated in this work wereoil is recovered by a graduated test tube. Finally, oil,obtained from Huadian area located in Jilin Provincegas and water were separated from each other for oilin Northeast of China, The elementary analysis showsyield calculation. At the end of each nun, the retortoil shale particles with a size range of 5-15 mm were中国煤化reigled for the totalused as feed stocks( Wang & Feng， 2006 ). Themodel was developed based on the decomposition re-YHCNMHG122Nguimbi C.R., Sun Y. H. and Li Q.便携式数据监控系统8888.0O0OFig,1 Power temperature and control management systemA|HJDB目。A - monitor; B- coler; C -oil; D - gas clletor; E - fluid condenser; F - temperature sensor; G - heater;H- oil shale; 1- crushed perliteFig.2 Experimental setupods determined as the optimal experimental operation3 Experimental resultsperiod. The first one starts at 100C , this imbibitionsTo determine the optimum heating periods for anyperiod helps to vaporize water. The second imbibitionsrate and to determine the yield of oil shale and gas twobegins at 450C, which is the pyrolysis temperaturediferent experiments were carried out with oil shalerequired for the decomposition of the kerogen. Weaccording to the highest oil production the Optimumneeded time to vaporize the water or decompose thesoaking and heating periods were chosen. Because thekerogen, time is given with the help imbibitions peri-pyrolysis starts over 450C，for all of these experi-ods.ments and 450C was selected as last temperature val-The experiment results show that it is possible toue to produce shale oil. The highest production of oilprodu中国煤化工prolysis tempera-corresponds to the optimum heating periods and thetureTYHCNMH G_ould be much, andother experiments were accomplished by using the op-in fU00U1c w puuuuc; oil from oil shaletimum condition. There are two different soaking peri-sample below the pyrolysis temperature.Pyrolysis of Huadian oil shale by eletrical heating on diferent heating rates123Between different parameters that play importantthird stage represents the decomposition of the mineralroles in the reaction of kerogen during oil shale pyrol-matter in the oil shale, which begins al 600C ( de-ysis, but the principal one is the rate of heat input topending on the heating rate). This is a high endother-the systerm. Many researchers have studied the heatingmic reaction manifested in the high peak in the heat.rate efct on the kinetics of oil shale pyrolysis , weightDecompusition of the carbonates in the mineral matlerloss，heat flow and derivative curves of oil shale deg-of the shale at these high temperatures is accompaniedradation was also studied (Li & Yue, 2004 ; Torrenteby considerable heat losses. This is one of the reasons& GalaAn, 2001 ) Three stages of weight loss the bestwhy oil shale is usually retorted at 450C - 550C, aillustrated in the derivative curves, shown as Fig. 3,part from the fact that a maximal oil yield is obtainedthe first stage corresponds to drying of the oil shale ，under these conditions. The total loss of this stage iswhich continues until 300C with a 7% decrease in19%. At the end of the reaction the residual weight istotal weight ( corresponding to the moisture content in81%. The electrical heating pyrtolysis used to measurethe sample). Up to 300C, the weight was almost sta-the weight loss of a sample as the function of time andble.temperature at a constant heating rate.---- 10C/min4 DiscussionSC/min一2C/minThe rate of weight loss determined by the rate of;taccumulation of shale oil and water was measured asthe function of both time and pyrolysis temperature.10-All runs were conducted to the final temperature750C as it can be seen from Fig. 4. This figure showsthe efet of increasing pyrolysis temperature on therate of liquids ’accumulation for different heatingrates. The high heating rate is 10C● min and the004005060intermediate one covers the range 5C●min -1. Heat-Temperature/Cing rate in the range 2C●min-' is considered low ;Fig. 3 Conversion versus temperature for Huadian oillAs it can be seen from the figure, low heating rateshale at different heating rates2C/min produced low oil and water rate passingthrough the maximum value at the temperature close toAbove this inlerval , the second stuge correspond-530C. In the low heating rate range, the percentageing to the decomposition of the organic matter and be-of liquids’formation in diferent conducted runs var-gan to produced oil with weight loss on difTerent rale,ied 13.0 to 14.6 and with an intermediate value ofit began at 450C ending at 600C. The heat needs13. 8% higher heating rate within a small range resul-for this reaction is low. Table 1 is listed the data forted in a higher liquid total weight loss percentage atthe pyrolysis temperatures. The characteristic temper-the end of a run. The total weight loss was calculatedatures of the process depends on the heating rate. Theas the difference between input weight and spent shaleTable 1 Different temperature values for three heating ratesHeating rateBeginning pyrolysisMaximum peak raleT。( temperature ofEnd pyrolysis temperature/C●min-temperature /C/%●min-1maxi中国煤化工竺380568565.9YHCNMH G010345.4665124Nguimbi G. R., Sun Y. H. and li Q.weight at the end of the any experiment. No doubtOn the contrary, oil conversion and oil yield waslower heating rate run requires more time to approachaffected by heating rate , oil yield calculation based onhigher reaction temperature, so the decrease in thethe quantity of oil generated in Fischer Assay. Therate of oil and water aceumulation when reaction tem-standard Fischer Assay is shown in Table 2perature increases will not afect the final quantity of( Heistand, 1976). The oil yield was calculated tothe oil and water produced but definitely change thethe 9.4% oil content and the results show that oilproduct distribution. The calculated total weight lossyield was affected negatively by the heating rate. Asfor low heating rate runs were found to vary betweenindicated in Table 3, the oil yield calculated based on13% -15%. The estimaled average loltal weight loss isFischer Assay for Huadian samples decreased with in-14. 0% for low heating rate experimental runs Fig. 4.creasing heating rates in the studied range. The high-The figure shows the similar behavior for the interme-est oil yield measured in this work was 80% corre-diate heating rate 5C/min. As it is clear from the fig-sponding to the lowest heating rate in this work. Theure, the magnitude of the weight loss rate, 2.3 g/decrease in the oil yield is accompanied by variationmin, was observed with the 10C / min heating ratc.in composition and physical properties of the producedThe higher heating rate has higher magnitude of oiloil. Conversion percentage inereased with increasingshale mass loss. The rate of liquids' accumulation in-heating rate while oil yield decreased.creased from 1. 3 g/ 'min in the low heating rate rangesTable 3 shows the variation of shale oil density( Kok, 2007 )，has reported similar results: higherwith heating rale. The densily of oil is heaviness andheating rates are resulted in higher reaction tempera-lightness of it is hydrocarbon contents. The table showtures and higher heat of reactions. Maximum weightthat increasing heating rate results in increasing oilloss peaks shifted to higher temperatures with increas-density. Oil density increased from 0. 838 g/cm’ ating heating rate. The influence of heating rate to thelow heating rate to 0. 867 g/ cm' at intermediate heat-total conversion of oil shale that included liberation ofing rate to 0. 898 g/cm’ to high heating rate. Thismolecular, water and kerogen decomposition is shownchange is ascribed to the change in composition of thein Fig.4 at low heating rates (2C/ min), conversionproduced hydrocarbons and the formation of heavierof oil shale is less. On the other hand; conversioncomponents.perccntagc was not afected by heating rates higherthan 5C/min. Higher than 10C/ min healing ralesTable 2 Elemental analysis of Huadian oil shale /wt%were not examined since control over reaction temper-Fischer asayProximale analysisSamupleature was dificult.Coke 0i1 Water Cas Volatile Ash CO2--- 2C/min83.7 9.3.16.60 77.66 3.21- 5C/min83.8 9.1 4.1 3.0 16.0 8.1 2.91---- 10C/min三1.s5e 1.0-Table 3 Variation of shale oil density with heating rateHeating rate ConverionOil yieldDensity .Oil and water/C●min-1/%%/g* cm-31%Temperature/心中国煤化工. 0.8387.750.867Flg.4 O11 and water ollection rate on dfterent tem.MYHCNM H G0.8989peraturesPyrolysis of Huadian oil shale by electrical heating on dfferent heating rates125this work.5 ConclusionsReferences(1) For oil shale samples used, the conversionof kerogen is direculy dependent on the final pyrolysisGersten J. Fainberg V, Hesroni C.2000. Kinetie study of thetemperature. The pyrolysis by electrical heating of oilthernad decomnposition of polyproplere, oil shale andtheir mixture. Fuel, 79: 1679-1686.shale at different heating rates is different, and thatHascakir B, Akin s. 2010. Recovery of Turkish oil shales byvaries with the pyrolysis conversion rate and changeelectromagnetic heating and determination of the dielectricfor a single sample at the special heating rate. Anyproperties of oil shales hy an analytical method. Energy &heating rates result in the different heat transfer ratesFuels, 24( 1) :503-509.and lermperature gradienl.Hascakir B, Babadugli T.2008. Experinental and numerical(2)This study shows that increasing the heatingsimulation of oil recovery from oilshales by electrical heat-rate increase also the product liquid hydrocarbons anding. Energy & Fuels, 22: 3976-3985.decrease the oil yield. Table 3 shows the direct im-Heistand R N. 1976. The Fischer assy, a stundard method.pacts of the heating rate have on oil formation and wa-Developrment Engineering， Ine. P. 0. Box A, Anvilter loss from oil shale during pyrolysis time. For the 3Points Rifle, Colorado 81650.heating rates a peak of the oil and water loss rate wasKok M V. 2007. Heating rate efet on the DSC kinetics of oilshales. Journal of Thermal Analysis, 90: 817-821.observed corresponding pyrolysis temperature whereLiS Y, YueC T.2004. Sudy of diferent kinetic models forthe maximum occurs.oilshale pyrolysis. Fuel Procesing Technology, 85(1):(3 )The relationship temperature -viscosity as da-55-56.ta was the paraneler inportant to determine duringLozanoJ A F, Gonzaler R A, Fermandez M C.1978. Thermalpyrolysis time but is not easily measurablc. Thermaldegradation of bitumen from the Faja of the Orinoco Ind.degradation of oil shale is a versatile process for up-Eng. Chem. Prod. Res, Deu., 17(1):71-79.grading kerogen. During degradation, kerogen mole-Steiger F. 2007. A study on the EU oil shale industry -viewedcules undergo cracking and polymerization to oil, gas,in the light of the FEstonian experience. Eurpean Acade-and coke. Higher heating raltes and higher heatingmies.Torrente M C, GalaAn M A. 2001. Kinetics of the thermal de-temperatures encourage the production of oil. Andcomposition of vilshale from Purollno ( Spain). Fucel,450C was the optimum temperature for all pyrolysis80: 327-334.rates.Wang Q X, Feng BJ. 2006. Sudy on the basie physicochemi-Acknowledgementscal charateristis of the Huadian oil shale. Jourmal of Ji-lin Uniersity:Earth Science Ediuion, 36(6): 1006- 1011.The authors gratefully acknowledgc financial sup-( in Chinese with English abstract)port by Jilin University and the Collge of ConstructionZainalS A. Abidin Z, Bekri 0. 2006. Simulation of oil shaleand Engineering for purchasing the necessary instru-retorting using the ICON steady state model. 26th Oilments and equipments for the experimental tests ofSymposum 15-17th, Colorado Schuul of Mine, USA.中国煤化工MHCNMHG