It is known that during the process of carbon nanomaterials synthesis, gaseous products and various unknown hydrocarbons are formed. Thus, the production of carbon nanomaterials could damage the environment. A detailed analysis of all gaseous products during the pyrolysis process is needed in order to clarify the nature of the formed substances and to control the technological characteristics of the catalyst. The chemical composition study of exhaust gases was made on the facility of propane-butane mixture pyrolysis for the carbon nanomaterial synthesis. The analysis of 16 polycyclic aromatic hydrocarbons (PAHs) of the extracts is made using a gas chromatography-mass spectrometry method. A quantitative analysis of gases was made by gas chromatography coupled with a heat conduction detector and a flame ionization detector. It was established that the concentrations of some PAHs exceed 14, 20, 90 and 100 times much as a maximum permissible concentration in the air. It was found that the appropriate devices of carbon nanomaterial production should be used in order to eliminate the PAHs that are formed.
UDC 536.46The results of investigations of the propagation of supersonic combustion in a tube completely or partially filled with a porous medium are presented. The relationship between the combustion-wave velocity, the medium parameters, and the properties of the combustible mixture has been established.Introduction. The last few years have seen growing interest in the processes of combustion propagation and detonation in porous media (PM) and blocked-up spaces (BS) connected with the development of new technologies based on filtration combustion, as well as with the unsolved problems of explosion safety in different branches of industry.It is known [1] that the velocity of the denotation wave propagating in a porous medium is, as a rule, lower than the Chapman-Jouget detonation velocity in a free tube, and this difference increases with decreasing initial pressure of the gaseous mixture. As follows from the previously published papers [2, 3], the mechanisms of ignition initiation and transfer in PM differ considerably from the case of combustion in a free space, since a PM is characterized by a much larger hydrodynamical drag coefficient and greater heat losses and, therefore, in the reaction wave propagating in a porous frame the pulse and energy losses from the wave front are much more significant and the gas flow is more strongly turbulized [3].In general, the mechanism of propagation of fast combustion waves in a PM incorporates the elementary processes of convective energy transfer, diffusion, and heat exchange between the gas and the porous body. However, these processes are still not clearly understood [4]. Moreover, the mechanism of mixture ignition in the interpore space is not clearly understood either. It is believed that at lower velocities initiation occurs due to the penetration of the burning gas from the nearby pores, the flame-front acceleration under interaction with reflected shock waves, and the spontaneous ignition of the compressed mixture that follows. With increasing velocity, the gas ignites mainly as a result of the adiabatic compression after the reflected shock waves [3,4].At present, there is no detailed theoretical description of the processes of porous combustion that would permit a priori prediction of the flame velocity depending on the PM characteristics and the initial pressure. As a rule, to construct such a model and check its validity, one needs a set of experimental data varying over a wide range of change in the basic parameters. However, currently an extremely small amount of data on the rate of supersonic combustion depending on the mixture composition, the initial conditions, and the properties of the porous medium is available.The aim of the present paper is to investigate the spectrum of supersonic combustion wave velocities in a tube completely or partially filled with a porous material, as well as to verify the empirical relationship established in [5] between the flame velocity, the PM characteristics, and the detonation properties of the combustible mixture.Exper...
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