Commercial process for mass production of synthetic natural gas through the adiabatic reactors: operational characteristics of a 50-kW pilot-plant, influence of steam, and CO2

What is it about?

In synthetic natural gas (SNG) reaction process, the water gas shift (WGS) reaction and methanation reaction take place simultaneously, and an insufficient supply of steam might deactivate the catalyst. In this study, the characteristics of the methanation reaction with a commercial catalyst and using a low [H2]/[CO] mole ratio in SNG synthesis are evaluated. The reaction characteristics at various possible process parameters are evaluated varying different process parameters such as the [H2O]/[CO] mole ratio, [H2]/[CO] mole ratio, flow of different % CO2 and reaction temperature. Temperature profiles on catalyst bed are monitored as a function of the [H2O]/[CO] mole ratio, [H2]/[CO] mole ratio, and flow of different % CO2. Through a lab-scale optimization process, suitable optimum conditions are selected and in the same condition a 50kW pilot-scale SNG production process through adiabatic reactors are carried out. The pilot scale SNG reaction is stable through overnight and the CO conversion efficiency and CH4 selectivity are 100% and 97.3%, respectively, while the maximum CH4 productivity is 0.654 m3/kgcat·h.

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Why is it important?

In this study, we have evaluated a methanation reaction characteristic with a commercial catalyst using low, [H2]/[CO] mole ratio, in the presence of steam using two different concentrations of CO2. The CO conversion efficiency and CH4 selectivity as a function of steam and CO2 supply were compared. Low CO2 syngas concentrations did not affect the CO conversion efficiency or CH4 yield, but increasing reaction temperatures led to low CO conversions efficiency and catalyst deactivation. On the other hand, with high CO2 syngas concentrations, the CO conversion, and CH4 yield were not affected. A pilot scale simulation has been carried out by 50 kW pilot scale SNG processing plant using operational parameters 360 °C, [H2O]/[CO] mole ratio = 2.5, [H2]/[CO] mole ratio = 0.93 and 22% CO2, WHSV = 32.5 m3/kgcat·h, 20 bar based on lab scale optimization. Almost the same SNG synthesis efficiency could be achieved in the pilot scale operation as observed in laboratory scale. The CO conversion and CH4 selectivities were 100% and 97.3%, respectively, and the CH4 productivity was 0.654 m3/kgcat·h. This allows us to offer the efficient technology in our SNG synthesis process. A 50 kW pilot scale SNG production was investigated, optimized and reproduced. Through the pilot scale SNG synthesis process 100% of the CO conversion and 96–97.3% of CH4 selectivity were achieved using a commercially available catalyst, indicate viable mass production of SNG is feasible through the designed plant (through further scale up). The design of 4 stages of the adiabatic reactor in the scaled-up process could be a challenged need to be overcome.

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