Computer controlled measurement of spontaneous combustion in coal stockpiles of the Western Lignite

Journal of University of Science and Technology BeijingVolume 13, Number 2, April 2006, Page 97MineralComputer controlled measurement of spontaneous combustion incoal stockpiles of the Western Lignite Corporation, TurkeyA Hadi Ozdeniz and Cem Sensogut1)Mining Engineering Department, Selcuk University, 42079 Konya, Turkey2) Mining Engineering Department, Dumlupinar University, 43100 Kutahya, TurkeyReceived2005-05-15)Abstract: The spontaneous combustion event in coal stockpiles is inevitable when appropriate environmental conditions are availableThe objective of a computerized measurement system is to measure temperature changes existing in a coal stockpile. In order to achiethis intention, the electrical signal conversion of temperatures sensed by 20 temperature sensors placed in certain points inside the coalthe transfer of these electrical signals into computer media by using analogue-digital conversion unit after applying necessaryfilterization and upgrading processes and the record of these information into a database in particular time intervals are provided. Afterwards, the diagrams of these time-temperature data are plotted. With the help of these graphs, the competent company will be able toexamine the behavior of coal stockpiles in terms of spontaneous combustion and take necessary precautions against self-combustionKey words: spontaneous combustion; coal stockpile; Western Lignite Corporation; resistance temperature detector1. Introductionthe coal stockpile area of the Western Lignite Corporation (WlC) in Tuncbilek (FiThe event beginning with oxygen absorption of coal from both open and underground mines of WLC arefrom air, continuing with oxidation and probably end- enriched in coal preparation plants. The coals useding with a flaming fire is called spontaneous combus- during this work were the enriched coals with particletion. The heat transfer caused by the effect of heat sizes between 18 and 50 mm. The size of the stockyardtransportation and diffusion mechanisms turns into a pile was about 10 m by 5 m in width with a height of 3chemical reaction after the adsorption of oxygen mo- m; the mass being approximately 120 t of coal in totallecules on to the surface of coal [l]. Knowing practi- and having a triangular prism shapegreat importance in terms of taking necessary precautionsAlthough many laboratory-scale works were carriedTuncbilekout on Tuncbilek coals in Turkey, no detailed researches were realized on large-scale stockpiles to de-termine their spontaneous combustion susceptibilitFig. 1. Location of the Western Lignite CorporationIndustrial sized studies have great importance espeTuncbilekcially in determining the general behavior of coal durIng spontaneous combustion. This behaavior includesA computer system was used to record the heat datamost or all of the parameters that are effective on received from 20 sensors(Pt100) and the informationspontaneous combustion event [2]. However, the num- saved on to a data base. The schematic presentations ofber of works is extremely few as they involve more these sensors are shown in Fig. 2. Additionally,thebudget and longer period of time. Therefore in this technical characteristics of Pt100s are presented in Tastudy, the behavior of coal in a stockpile was investi- ble I and Fig 3gated by a computer controlled setup2.1. Computerized measurement system2. Experiment mechanism and layoutTheV凵中国煤化工 d in dtermCNMH G accepted asThe coal stockpile of the experiment was formed in the most important signals of spontaneous combustionCorresponding author: Cem Sensogut, E-mail: sensogut@mail dumlupinar. edu. trJ. Univ. Sci. TechnoL. Beijing, Vol 13, No 2, Apr 2006n coal stockpiles involves three main parts:(1)conto-digital conversion unitT173)computer program(1)Converter circuits.6T4人TThese circuits can be called as signal harmonizationor conditioning unit. The basic members of measure10Bment processes are the Pt100 temperature sensors. Actually being electronic resistances, these sensors are7T15人119electronic members and their resistances increase inC TIIAdirect proportion with temperature. Different fromnormal resistances, its resistance changes linearly withT8⊥T1人T2emperature. When the resistance changes due to tem12perature variation on the sensor, the voltage varies atthe ends of the resistance proportional with the temperature. This voltage variation is transmitted throughlow conductive filter(transmits low frequencies but notHumidity sensorTemperature sensorhigh frequencies) in order to eliminate the effects especially caused from system noises and other electricalparasite resources. This type of circuit is shown in FigAnalog-Digital ConvertorFollowing this process, the boundaries of voltagevariation are adjusted. This process should be performed considering input voltage boundaries of analogue-digital conversion unit, and if the voltage varia-2 m in heighttion exceeds these boundaries the aforementioned unitdoes not work and on the contrary if the variatiopears in the lowest boundaries, the measurementracy decreases. Differential amplifiers are used to re-main between these boundaries. The principle scheme Fig. 2. Schematic view of Pt100s in a stockpile:(a)plan;(b)of this circuit is given in FigA-A’ cross- sectionTable 1. Technical characteristics of Pt100(K type)Temperature /C Voltage/mV Temperature/C Voltage/mV Temperature/oC Voltage /mV012207800332771429290040018513l10045108613720640200101519128R30090012001500Fig. 4. Secondary level low voltage filter circuit.reaches to analogue-digital conversion unit after beingFig 3. Voltage-temperature diagram of Pt100transmitted thid harmonized. This unit isformed fro中国煤化工(2) Analogue-digital conversion unitanalogue multiCNMHG circuitTheThe electrical signal including temperature data unit used in this study has the following characteristicsA. Hadi Ozdeniz et al., Computer controlled measurement of spontaneous combustion in coal stockpiles of.R(C) Have separate calibration chance for each chan-nelured values coming from two devices are displthe first interface shown in Fig. 6. The first one is analogue-digital conversion unit connected to the parallelFig. 5. Differential amplifier.port and the second one is a portable measurement dee connected to serial port and measures humidity(a)12 bit resolution analogue-digital conversion, and temperature. 20 temperature data that are measured(b)100 us conversion periodwith 20 temppile come from the measuring unit connected to the(c)8 channels analogue inputparallel port. The humidity and temperature informa(d)5 bit digital outputtion of air is determined from measuring unit connected(e)3 bit digital input;to the serial port. In this interface, there exist buttonsand data boxes to open and close serial port, change(f) Communication with printer portmeasurement interval, take instantaneous records forThe MAX186 serial ADC integrated circuit is used testing purposes and achieve backup prodin this unit. In addition, 74HC373 Latch Buffer inte- ally. System time and calendar are also shown in twograted circuit is used in digital input-output processes. data boxes continuously again in this interface. The reThe communication with this unit is provided by the cords are saved according to these calendar and timeprinter port. The communication speed is rather im- informationportant since the analogue-digital conversion integrated circuit communicates with serial connection Sincethe speed of the communication is directly proportionalwith the speed of computer, it should be determinedinitially. After adjusting the speed, the data communication from analogue-digital conversion integrated circuit is achieved by the help of printer port by using only3 pins of this integrated circuit. The channel informa-tion from which the reading will be made and the timewhen measurement will begin is transferred into comFig. 6. First interface displaying the measurement values.puter with Din pin and the measurements are saved onThe records shown in the interface in Fig. 6 andto the computer with Dout pin. The third pin named assaved automatically in certain intervals or saved maClK pin provides synchronization during sending andally with an instantaneous record button are seen in thereceiving information with Din and Dout pins. In addi- second interface presented in Fig. 7. These records cantion to this unit, a 24-channel analogue multiplexer be deleted or changed one by one with the button set at(MUX) circuit was designed to get measurements fromthe bottom of the interface. In this interface. the meas20 measurement points since 8 channel analogue inputurement values are tabulated with two separate tableswas not enough. This additional module is designed byusing 4051 analogue key integrated circuits and 74138because of numerous measurement pointscode solving integrated circuitIn the third and last interface shown in Fig. 8, the re(3)Computer programlured coefficients and zero-tuning values are on display and record 20 temperature values in centigradThe program was built with a visual and objective and they were all measured as numbers between 0 andoriented programming language Delphi 3.0 and AS- 4096. These measured values coming from the meas-sembler language codes were used in the program toportreach the computer ports. The properties of the pro- as integer numbbetween 0 and 4096 due to thegram are as followsnature of thece. he maximum and minimum(a)Gets measurements in time interval in which the temperature vaperiod is adjustable (it is taken as 5 min if any other 0 respectively中国煤化工directly progiven)CNMHGB)Take two backups of all measurement values ear. An offset is used in fine-tuning the adjusted lowestJ. Univ. Sci. Technol. Beijing, Vol 13, No 2, Apr 2006emperature value on the device. This means numbeThe cables coming from Pt100s placed in the stock-addition to the measured lowest temperature value to pile are connected to the digital converter panel andobtain zero in the measured value. There are separate then to the computer. The measurement readings arecoefficients and offset values for each measurement made automatically with a computer. For this purposepoint and they are kept in an exchangeable databasea special program in Delphi 3.0lphi 3.0 programming languagDy using this program the tempvalues taken from sensors are recorded into a databaseautomatically every 5 minutes during 24 hours. Themeasurements were taken in June, July and August ofthe year 2002 [3]3. Evaluation of recorded dataThe measurements were taken from 20 different in-Fig. 7. The second interface displaying the location of the neous combustion. The data taken from the stockpile ismeasured valuestabase by a computer every 5 minutes. The total num-ber of data obtained from stations every 5 minutes isand temperature of the weather, a total of 454.014 datater. while col-pIcorded every hour from 3 stations. The total number ofthese manual records was 5157. There were 459. 171Fig. 8. The third interface in which the calibration of thedata in totalsystem is realizedThe measured raw data were filtered with the movIn this program, measurement processes are pering Average Filter method in Excel program [4].Theformed by using TIMERs. The record of measured val- aim of this filtration was to eliminate the effects ofues in certain intervals and the display of time and cal- voltage fluctuations in electrical network and miningendar on the screen are provided by using two different machinery such as grader, bulldozer etc. working nearIMERs. At the same time, a small software filter is the station The values selected every hour for TI areplaced in this process. 10 values are read from the same given in Appendix 1. Moreover, the time-temperaturechannel and after arranging them, the mean of the three graph belonging to TI station is also presented in Figvalues at the middle is calculated. This is not a sliding 9mean filter but a mean filter purifying from end points排TYH中国煤化工CNMHGFig 9. Time-temperature graph of Tl staticA. Hadi Ozdeniz et al., Computer controlled measurement of spontaneous combustion in coal stockpiles of.4. ConclusionsReferencesIn this study, an experimental research work was [1]BUnver and A. Ozozen. models related with the timeperiod of the spontaneous combustion occurring in coalcarried out on a coal stockpile of WLC, Tuncbilek forstockpiles and precautions to be taken, Min.J. Turkey(in1720 h from June to August 2002. For this purpose, theTurkish),37(1998),No.3,p.29stockpile were evaluated. The time-temperature e [21 FAkgun, Theoretical and Experimental Evaluation of thereadings taken from 20 sensors located inside theSpontaneous Combustion of Coals [Dissertation](in Turkgrams of 20 station points were plotted using these dataish), Graduate and Applied Sciences, Technical UniversitThe maximum 26c value of ti was reached in theof Istanbul. 1994600th hour. The main reason for the regular observa[3 A.H. Ozdeniz, Investigation of Spontaneous Combustiontion of the stockpile was to detect any heat accumulaEvent in Coal Stockpiles-Western Lignite CorporationCase Dissertation](in Turkish), Graduate and Appliedtion, which may cause a spontaneous combustion pheSciences, Selcuk University, 200nomenon resulting in serious economical loss. In case,[4] S. Canan, Y. Ozbay, and B Karlik, A method for removingthere is a spot of heat accumulation the mine managelow varying frequency trend from ECG signal, [in] Proment can take a necessary precaution to combat itwithout any lossEngineering Days, 1998, p.161Appendix 1. Values recorded and filtered for I h intervals [3]zT「T214T51WTT9「T0T1T2T3T4T5m6ⅳ7|T8T9T| S N B RHRY「194168611261512252240621621018199281120215043891791W1511925127918d08wE21981842157124618219751652184197206215823019z204220321758186195417620741692576918d06190176149281759_19091571724190419920722381891981971647177516119814356597917416218841744146a7217331881554175018.80l2e22191871942193161617320221818421891911158717131813230016821832152082151136|86155416891402716618101488168180190198223217,818481831536165682275164818014771677180四囚四15151708183174C19022852284859854224451782193162617811972022162282195419919317211832的2a23217204819817819052010720471864191时团但1四团252四4四四时279243891E269319892139186212218222402518218228218419742 9s 31, 06f 21 9219751 0.66NS122192017432701192142186202192524172532192421919832310121591605Nsa2c2时1时192141因182图2团2122282242191时21962483252241916904Ns221921761221418616219223424025221722115213224他234286!9169002218420md2312121211212142249222121812281222588A4964d00242571616729419020517121214623243209248218920321218528233999162000Note: Ztime, h; Sweather temperature, C; RYwind direction: N humidity, %; Ttemperature inside the stockpile, C:RH-wind velocity, m/s: B--atmospheric pressure, Mb中国煤化工CNMHG