Pyrolysis of Natural Gas: Effects of Process Variables and Reactor Materials on the Product Gas Composition

Abstract

High-temperature pyrolysis of natural gas is the basis of the standard method for the manufacture of acetylene. The study of methane pyrolysis was designed to find optimum process conditions that would produce high yields of acetylene with minimal carbon formation. High temperatures and short residence times enhanced the selectivity for acetylene, while hydrogen dilution was found to suppress the generation of carbonous products. Carbon formation on reactor surfaces over time may be mainly responsible for the misalignment of predicted and measured product gas compositions, as the mechanisms reported do not consider the surface chemistry. In essence, the pyrolysis system favors the highest possible temperature and shortest possible residence time, suggesting that the selection of reactor materials is the key for pyrolysis process optimization. The operating temperature is likely dictated by the physical properties of the reactor materials rather than the selection of optimal pyrolysis conditions.

Experimental and Theoretical Studies on Water-Added Thermal Processing of Model Biosyngas for Improving Hydrogen Production and Restraining Soot Formation

“…The results presented in Table S1 show an influence of the total flow and water content on the conversions and productions measured at the temperature of 1500 °C. The residence time refers to the real residence time in the reaction zone above 1100 °C; the calculation method was described in detail in the study done by Wang et al 34 Corresponding residence times for the total flows of 5000, 2500, and 1500 mL/min are approximately 23, 46, and 76 μs, respectively. Both conversions of CH 4 and CO 2 and both productions of CO and H 2 decrease when increasing the flow rate, as shown in Figure 5, which can be explained by the change in residence time corresponding to different flow rates.…”

“…For example, the solid carbon can be periodically removed from the reactor and utilized in some other application. It can alternatively be periodically burned or gasified, 34 or its formation can be minimized by choosing a specific reaction condition, possibly with a controlled amount of steam presented in the system.…”

“…Moreover, the silicon carbide wafers were believed to only affect the temperature distribution versus radius and the intersection area of the reactor, thereafter affecting the actual reaction temperature profile and the residence time of the reactants in the reaction zone instead of the reaction mechanism. 28,29,34 6. CONCLUSIONS Thermal processing to upgrade biosyngas was studied with an aim to convert the present CH 4 to H 2 and CO.…”

“…It is noted that the carbon deposition mechanism has been studied by this team in previous researches. ,,, In this paper, we only concentrate on the effects of reaction parameters on carbon deposition rather than on the carbon deposition mechanism itself. Moreover, the silicon carbide wafers were believed to only affect the temperature distribution versus radius and the intersection area of the reactor, thereafter affecting the actual reaction temperature profile and the residence time of the reactants in the reaction zone instead of the reaction mechanism. ,, …”