Experimental Study of Kinetic Properties of Pyrolysis for Conveyor Belt in Coal Mine

De.2005J.China Univof Mining &Tech (English Edition)Vol 15 No 4Experimental Study of Kinetic Properties ofPyrolysis for conveyor belt in Coal mineSONG Zheng-changSchool of mechanical Engineering, China University of Mining Technology, Xuzhou, Jiangsu 221008, Chinabstract: The combustion of conveyor belt is a leading factor of mine fire. In this paper, the pyrolysis properties ofdinary conveyor belt and fire-resistant belt were studied experimentally with thermo-gravimetric analysis andderivative thermo-gravimetric analysis, and the curves of pyrolysis properties were achieved. On this basis, theactivation energy and reaction order of pyrolysis were obtained in combination with theoretical analysis, aiming toprovide data for further numerical simulation and simulating experiment of mine fireKey words: conveyor belt; combustion; pyrolysis; mine fireCLC number: TD 51 Introductiondiffer from those on the ground. Therefore, it is ofgreat significance to study the pyrolysis characConveyor belts are widely used in coal minesteristics of conveyor belt and the principle ofand other places such as power plants and harbors as poisonous and hazardous gases release. The studyimportant means of material transportation. Inan provide necessary experimental data for furthercoalmines, with the deepening of mining and the numerical simulation of mine fire.increase of the production capacity, belt conveyorshigh2 Experimental Set-up and Procedurea variety of fire prevention measures have beeThe thermo-gravimeter made in Japan is of thetaken, mine fires due to conveyor belt take placetype TAS-100 with accuracy of li g, its workingnow and then. The poisonous and hazardous gasesprinciple is shown in Fig. Iand high temperature fume during mine fire spreadsExperimental procedure: the sample(1)is putfast and widely, as a result, not only a large amountinto a container and heated in the oven (2). Itsof coal and installation are destroyed, but also theweight will change due to pyrolysis so that the leverhuman lives are in danger. and what's more. mineof the scale supporting the sample will incline to onefire can induce coal or dust explosion resulting inde, and the signal is detected and output throughcatastrophethe photoelectrical element (12). The analogousIn order to guarantee normal production,photoelectrical signals are converted through themining system must be ventilated, so the firing oftooth-like waved circuit(13), comconveyor belt usually takes place in a confined sIcircuit(15)and operator(17) to digital signals andand under forced ventilation - The pyrolysisinput to computer followed by calculation andcombustion characteristics of conveyor belt as wellanalysis in the computer, finally, are displayed onas the release of poisonous and hazardous gasesthe screen or中国煤化工 rintingReceived 14 April 2005: accepted 20 May 2005CNMHGCorrespondingauthorTel+86-516-3885511;E-mailaddresssongzhengchang@sohu.comSONG Zheng-chang Experimental Study of Kinetic Properties of Pyrolysis for Conveyor Belt in Coal Mine315In order to form an inert atmosphcontainer, the oven is inflated with highly purenitrogen to prevent the sample from being oxidized1517 Fat the beginning of experiment 31 During the experiment, the recorder plots the TG and DTG curvesautomaticallyIn the experiment, the samples are fire-resistantconveyor belt and ordinary conveyor belt, and the6}-7temperature increment rates are 10 C/min,Fig 1 Diagram of experimental system for pyrolys20C/ min, and 30 /min, respectivelySample; 2. Electrical oven; 3. Support; 4. Magnet; 5. Poise: 6. Balancelever; 7. Raster; 8. Counterpoise; 9. LBD; 10. Electrical source: 113 Experimental Result and analysisPreamplifier; 12. Photoelectrical element; 13. Tooth-like waved circu14. Comparator; 15. Pulse circuit; 16. On-off circuit; 17. Operator: 18The TG-DtG curves of conveyor belts are givenCPU; 19. Keyboard switch; 20. Display, recorderas Fig 2-300400200400600800a)20℃/min(c)10℃/minFig 2 TG-DTG curve for fire-resistant conveyor belt曾2004006008000040060080000400600800a)20℃/minb)15℃/min(c)10℃minFig 3 TG-DTG curve for ordinary conveyor beltFrom the TG and dTG curves, the curves of the namely the V-T curves, can be derived, as shown inreleased volatile variation with the temperature,Fig 4翼704▲=20℃/min10℃/min—10℃/min10200300400500600700800900200300400500600700800900(a) Fire-resistant belt中国煤化工Fig 4 v-t relationCNMHGExperimental results show that, for the same kind of sample, the quantity of volatile releaJ.China Univof Mining &Tech(English Edition)Vol 15 No 4depends on the temperature only, and the tempera△ln(-)=--△(二)+n△Inw,ture increment rates have little influence on it Fordifferent samples, the volatile release are different atand further rewritingthe same temperature, and the quantity of released△log(dr)Rvolatile of fire resistant convey belt is lower than that△logof ordinary conveyor belt at the same temperatureespecially under 350 C, the former is greatly less△(plottingby using the left-hand side of thisthan the latter. This demonstrates that the fireresistant conveyor belt can prevent from firing atequation, the activation energy and reaction order cantemperature lower than 350C effectively, buttemperature above 450 C, this effect will reduceIn this process, the expnts arefirstly regressed in the linear form of y=ax+b, andActivation Energy and reaction Orderthen, E and n are determined. All the experimentalpoints are selected at the steep location of TG curveThe pyrolysis process is considerably complicat- The results are shown in table belowd and the reaction order that is unknown in theTable 1 E, n of fire-resistant conveyor beltexperiment can be derived conveniently with theTemp. increment rateFreeman-Caroll methodTemp. range/C320-460340-380340460From the reaction kinetic equation,Volatile range/%2.76-588811.07-590210.53-57.67dwkf (w)E/(kJ, mol)40.022.where w is the residual weight, equal to the weight atthe time t minus the residual weight at the time of 5 Conclusionsinfinitude(w), and w is the weight of contents thatcan not be volatilized1) Through experimental investigation andLet f(w)=w, and take account of Arrhenius theoretical analysis, the pyrolysis results are achievedas well as the activation energy and reaction orderequationThe experimental data can be used to calculate thedimensionedDwhere A is frequency factor, E is activation energy, experiment of mine fireand R is an ideal gas constant, thus2)For the same kind of sample, the quantity ofvolatile release depends on the temperature only, anddtthe temperature increment rates have little influenceAs w does not change, f(w)is constant, independent on itof temperature, and the temperature increment rate3)At the same temperature, the quantity ofreleased volatile of fire resistant convey belt is lowerdtconstant, thus the equation above can bethan that of ordinary conveyor belt, especially underwritten as350 C, fire-resistant conveyor belt can prevent fromdfiring effectively, but at a temperature above 450 Cthis effect will decreaseTaking the logarithm of the equation above yieldsererences[1 Fan WC, Introduction to Fire Science. Wuhan: Hubei Science and Technology Press, 1993. (In Chinese)[2] Tewarson A, JiangMorikawat. ventilation and controlled combustionbustion and Fl95:151-169中国煤化工[3] Tewarson A. The SFPE Handbook of Fire Protection Engineering MassachusetCN MH Gciation, 1988[4] Fu W B. Combustion Principles. Beijing: Higher Education Press, 1989. (In Chinese)