Study And System Analysis Of Natural Gas Non-catalytic Partial Oxidation Process

Natural gas non-catalytic partial oxidation technology is investigated in this thesis. The effects of operating parameters on natural gas conversion performance are studied with the hot model experiment, numerical simulation and reactor network simulation. Additionally, the exergy efficiencies of different natural gas indirect conversion technologies are compared.1. Natural gas non-catalytic partial oxidation hot model experiment platform is established. The effects of O2/CH4 ratio, steam, carbon dioxide and operating load on the syngas composition are studied. The reaction processes of CH4-steam and CH4-CO2 are investigated by using the tubular experiment device. The results of experiment indicate that the effective syngas (H2+CO) concentration reaches maximum when the mole ratio of O2/CH4 equals to 0.90. The addition of CO2 or steam could be applied to adjust the syngas ratio of H2/CO.2. The numerical simulation model of non-catalytic partial oxidation reformer is established. The results of the PDF model based on chemical equilibrium and the EDC model coupled with detailed chemistry reaction mechanism are compared. The PDF model presents some deviations on predicting the flame structure and overestimates the CH4 conversion; the EDC model predicts the blow off phenomenon of the flame and reflects the temperature and syngas composition variations with axial distance change. Besides, the outlet syngas composition coincides well with the industrial data. The effects of operating pressure, O2/natural gas ratio and steam addition on the natural gas reforming performance are studied with EDC model.3. The reactor network model (RN model) is established according to the flow partion of industrial reformer. The effects of operating pressure, O2/natural gas ratio and residence time on natural gas conversion are studied with RN model and equilibrium model. The RN model results agree well with the industrial data. The effects of steam, CO2, natural gas composition and raw material preheat temperature on the syngas compositions are studied with the RN model. The feasibility of multi-reforming on the natural gas non-catalytic partial oxidation process is analyzed.4. The simulation processes of natural gas to hydrogen are established with different indirect conversion technologies. The Natural gas-O2-Steam thermodynamic ternary phase diagram is applied to investigate the natural gas reforming and heat recovery unit. The exergy efficiencies and exergy distributions about processes are analyzed. The excess steam concentration in raw material may lead to poor thermodynamic performance in natural gas indirection conversion systems. The process established by analysis results of the ternary phase diagram method presents the highest exergy efficiency (ηEF=79.28%), followed by the non-catalytic partial oxidation (ηEF=79.23%). The hydrogen exergy efficiencies of non-catalytic partial oxidation coupling heat exchange reforming (ηEF=76.80%, ηH2=70.41%) and heat exchange reforming (ηEF=76.31%, ηH2=70.18%) are higher than other technologies with the cost of high pressure steam generation.