Equipment Design Theory And Experimental Research Of Oxidation Kinetics Testing For Coal Spontaneous Combustion Tendency

Testing device for identifying the propensity of coal to spontaneous combustion based on oxidation kinetics is the concrete application of the Testing method for identifying the propensity of coals to spontaneous combustion based on oxidation kinetics. Accurate control technology of working substance and operating condition in the temperature-controlled testing furnace is the key technology of oxidation kinetics testing device for identifying the propensity of coal to spontaneous combustion. The temperature distribution in the temperature-controlled testing furnace and its main influencing factors has been studied systematic and deeply, according to this a testing device has been developed which can not only reflect the whole dynamic evolvement process of coal spontaneous combustion but also be operated conveniently and easily.In view of the electric heating mode with the advantages of fast heating, temperature easily controlled on the condition of high equably heating, heating enclosed space in a vacuum or protective atmosphere, automated job, clean and being compact in structure, it has been used as the heating pattern of the testing furnace. Through comprehensive analysis and comparison of the existing six different ways of electric heating ways and considering that the heating ambience is gaseous media in the enclosed space of testing furnace, the way of indirect resistance heating has been used as the heating mode of the temperature-controlled testing furnace.To get a high stability testing furnace with multiple temperature-controlled patterns, it has been studied as follows. By theoretical calculation and comprehensive analysis, the main parameters of mixing fan in the testing furnace have been determined as follows: the impeller structure is radial spoke, the number of vanes is six, the external diameter of the impeller is 0.175m, impeller inlet diameter is 0.55m, rotating speed is 1400rpm, the connection way between fan and engine is direct drive. Temperature distribution in the testing furnace and the shortest time to achieve uniform temperature distribution has been analyzed by means of CFD simulation under three conditions of 30o, 45o and 60o of vane installation angle, it has been showed that furnace temperature distribution is more uniform when the vane installation angle is 45o and 60 o and it takes the shortest time to achieve uniform temperature distribution when vane installation angle is 45o. Temperature distribution in the testing furnace has been analyzed under the same condition of electric heating and mixing fan respectively under the condition that the furnace size is 0.3m×0.3m×0.3m and 0.4m×0.4m×0.4m. The results indicated that temperature distribution of former is less uniform than latter and the temperature of different positions is violate and stability poorly.The internal temperature distribution of temperature-controlled testing furnace with the size 0.4m×0.4m×0.4m, where coal chamber is put in five different positions and installation angle of mixing fan blade is 45°is researched by means of CFD simulation .The results showed that when coal reaction chamber is putted in the positions of vertical(（-2.5cm,20cm,-10cm）、（-7.5cm,20cm,-10cm）and horizontal（-2.5cm,20cm,0cm）, temperature distribution in the testing furnace is uniform. Through testing the crossing-point temperature of three different typical coal samples in coal reaction chamber respectively under the condition of two different ventilation ways which are down-in up-out and up-in down-out, and two different display ways that are vertical and horizontal, it has found that the crossing-point temperature of coal with the ventilation way up-in and down-out is obviously higher than that with down-in and up-out, similarly the crossing-point temperature of coal in vertical chamber is higher than that in horizontal chamber.Hierarchical design method is applied to develop gas supply and analysis system which consists of air system, sampling system, separating system, temperature controlled system, and testing record system. They can sample, inject multiple-tract automatically ,and test different characteristic parameters like the content of O₂、N2、CO、CO₂、CxHy and temperature at the same time. The system has the advantages of large measurable range, high accuracy, and can rapidly separating gas according to acquisition requirements.Human-computer interaction operating platform is developed which integrates gas analysis system and testing oven system. Through this operating platform , some functions are realized, for example, setting experiment parameters （temperature control ways, temperature raising rate, air flow ,sampling temperature and time）,selecting collection tract ,collecting multiple-gas path signal , monitoring running state, data analysis and storage, data communication and so on ,in a word it has realized multiple-parameter rapidly and automatically testing in the process of coal spontaneous combustion.