Pyrolysis furnace simulation

Traditionally, olefins in the United States have been produced from light hydrocarbon pyrolysis. Earlier publications on computer simulation and control of pyrolysis reactors were addressed primarily to pyrolysis furnaces using ethane, propane and butane as feedstocks (1,2,3). 

Values of the thermal conductivity of different chars are shown in Fig. 3. together with the conductivities of the cellulose pellets, and for reference, gaseous nitrogen. The chars tested for thermal diffusivity (conductivity) had fairly uniform properties because they were prepared in a pyrolysis furnace, and not in the simulated fire apparatus. This tended to minimize temperature gradients, but there was no assurance of absolutely uniform density, for the reasons noted above. Preparation of the chars followed a temperature history designed to simulate that in the simulated fire apparatus. 

In order to extrapolate the laboratory results to the field and to make semiquantitative predictions, an in-house computer model was used. Chemical reaction rate constants were derived by matching the data from the Controlled Mixing History Furnace to the model predictions. The devolatilization phase was not modeled since volatile matter release and subsequent combustion occurs very rapidly and would not significantly impact the accuracy of the mathematical model predictions. The "overall" solid conversion efficiency at a given residence time was obtained by adding both the simulated char combustion efficiency and the average pyrolysis efficiency (found in the primary stage of the CMHF). 

Chapters 7-9 deal with the process aspects of pyrolysis to produce epbba. The first discusses the use of aerospace technology to simulate an unconventional process. The second discusses the results of recent attempts to develop computer models for large scale pyrolysis of hydrocarbons and the third discusses recent process and furnace design advances. 

Cold box and refrigeration system. After the acid gas and water removal, the pyrolysis gas is cooled and condensed to approximately -165°C only hydrogen and some methane remain in the vapor phase. The feed locations are determined via process simulation. Hydrogen and methane are drawn from the lowest temperature stage separator and sent to thermal cracking furnaces as fuel. 

Simulate the vinyl chloride process (Problem 5.4) using Aspen Plus. Take the feed at room temperature and 20 psia. Operate the direct chlorination reactor at 65°C and 560 kPa. A distillation column removes the trichloroethane and the rest of the stream is sent to the furnace. Heat the stream to 1500 F so pyrolysis takes place. Cool the effluent from the furnace, and recycle the vapor (mostly HCl). Send the hquid (vinyl chloride and ethylenedichloride) to a distillation column for separation. 

Nowadays, improved computing facilities and, more importantly, the availability of the Chemkin package (Kee and Rupley, 1990) and similar kinetic compilers and processors have made these complex kinetic schemes more user-friendly and allows the study of process alternatives as well as the design and optimization of pyrolysis coils and furnaces. In spite of their rigorous, theoretical approach, these kinetic models of pyrolysis have always been designed and used for practical applications, such as process simulation, feedstock evaluations, process alternative analysis, reactor design and optimization, process control and so on. Despite criticisms raised recently by Miller et al. (2005), these detailed chemical kinetic models constitute an excellent tool for the analysis and understanding of the chemistry of such systems. 

Based on naphtha pyrolysis experiments conducted in a bench scale tubular reactor (suitable for the simulation of industrial tubular furnace operations and taking into account the changes of expansion, temperature and the pressure in the reactor), a kinetic model has been developed for the calculation of the degree of de-con osition, the actual residence time, and the severHy of cracking. 

Combustion of polymers in horizontal or vertical furnaces and subsequent off-line HRGC-MS of pyrolysis products is suitable for simulation of burning processes [454]. Kettmp et al. [455] use a macro-scale TG/DTG-DTA-CT-GC-MS system for enlarged sample capacity, simultaneous TG-MS and... 

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