Simulation temperature profiles pyrolysis

This paper presents the first experimental results for the solid motion inside a pilot-scale rotary kiln. Such data are useful to enable efficient pyrolysis reactions inside a rotary kiln to be carried out, through the prediction of residence time and material hold-up, and the evaluation of different surfaces and temperature profiles according to the operating conditions. In the first part, the pilot-scale rotary kiln and the principle of the experiments will be described. An original dynamic solid motion model will be presented in the second part, this dynamic model is derived from the original static model of Seaman [1], The static and dynamic experimental results are finally compared with the simulated results. 

The pyrolysis reactor can be simulated in Aspen Plus as PFR with power-law kinetics and temperature profile or heat duty. To validate the kinetic data, we consider an initial flow rate of 73000kg/h EDC at a reaction temperature of 530°C and 18 bar. The reactor consists of 16 tubes in parallel with an internal diameter of... 

In the case of 44 % moisture there is liquid water present in the structure and also the permeability of liquid influences the conversion time of the sample. Figure 6 shows the measured temperature profiles of Figure 1 and the two simulated Cases 6 and 7 in Table 1, simulated for liquid axial permeabilities of 10 and 10 respectively. In both cases the radial permeability is assumed to be 10 lower. It is seen from Figure 6 that the intrinsic permeability of liquid has a large influence on the pyrolysis time. A higher permeability leads to a larger transport of water through the wood and less water evaporates inside the sample, which reduces the time of conversion. 

Fig. 37. Simulation of the instantaneous molecular weight distribution of PE during pyrolysis, expressed in term of repeated units n heating rate 10°C/min, pressure 1 atm. Panel (a) Total mass fraction of chains nearby the border range of evaporable compounds at different temperature levels panel (b) temperature profiles of components in the gas and the nearest liquid phase.

The unit consists of a small diameter coil which is electrically heated in a multiple zone heater. The hydrocarbon feed and the steam are preheated to the desired inlet temperature of the commercial coil before they are fed to the pyrolysis coil. The pyrolysis coil has been designed to allow the control of the process gas temperature along the length of the pyrolysis coil. Since the coil used in the pilot plant has essentially no pressure drop, a technique has been developed to also control the hydrocarbon partial pressure profile in the coil, and therefore, accurately simulate commercial coil performance. The pyrolysis heater effluent is rapidly quenched and sent to an elaborate sampling system where the different fractions are collected at optimal temperature and pressure. The effluent is analyzed routinely for the presence of 45 chemical compounds and a detailed hydrocarbon breakdown including C4 s, Cs s and pyrolysis gasoline is obtained. 

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