Abstract
Natural gas resource is abundant and can be found throughout the world. But most natural gas reserves are at remote sites and considered stranded because of the extremely expensive transportation cost. Therefore advanced gas-to-liquid (GTL) techniques are being studied to convert natural gas to useful hydrocarbon liquids, which can be transported with far less cost. Direct pyrolysis of methane, followed by catalytic reaction, is a promising technology that can be commercialized in industry. In this process, methane is decomposed to ethylene, acetylene and carbon. Ethylene and acetylene are the desired products, while carbon formation should be stopped in the decomposition reaction. Some researchers have studied the dilution effect of various inert gases on carbon suppression. All previous results are based on the isothermal assumption. In this thesis, our simulator can be run under adiabatic conditions. We found there was a crossover temperature for carbon formation in the adiabatic case. Below the crossover temperature, the carbon formation from pure methane feed is higher than the one from a methane/hydrogen feed, while above the crossover temperature, the carbon formation from pure methane feed is lower than the one from a methane/hydrogen feed. In addition to the pure methane and methane/hydrogen feed, we also simulated the rich natural gas feed, rich natural gas with combustion gas, rich natural gas with combustion gas and methane recycle. We found the outlet temperature increases only slightly when we increase the initial feed temperature. Furthermore, the combustion gas or the recycled methane has a dilute effect, which increases the total heat capacity of reactants. The outlet temperature from the cracker will not drop so much when these gases are present, causing the methane conversion to increase correspondingly. Up to now there is no adiabatic simulator for methane pyrolysis. This work has significant meaning in practice, especially for rich natural gases.
Yang, Li (2003). Kinetics simulation for natural gas conversion to unsaturated C₂ hydrocarbons. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2003 -THESIS -Y26.