Syn Gas Preparation 2/3

After desulphurization, the feed gas(CH4) is reformed to get hydrogen and nitrogen which are the main constituents for the ammonia synthesis. The reforming reaction is highly exothermic and requires a high amount of heat which is being supplied by the burning of natural gas. As the reaction requires much heat it is carried out in two steps: primary and secondary reforming.

In primary reforming steam methane reforming(SMR) reaction is carried out in catalyst tubes present inside the furnace. The reaction favours high temperature and low pressure but due to economic and operation parameters downstream, the reaction is carried out at high pressure. The catalyst tubes present inside the radiation section of the furnace takes the heat by burning fuel gas and reaction is performed and around 12% of unconverted methane is left in the end which is reformed in the secondary reformer.

Secondary reforming is also called Auto-thermal reforming(ATR). The secondary reformer has two zones: combustion and catalyst bed zone. In the combustion zone, process air combust with the partially reformed gas and provide heat to complete the reforming reaction. The remaining methane is consumed by complete reforming and downstream of the secondary reformer, we get Syngas. The flow rate of the process air is adjusted in such a ratio that total O2 is utilized in combustion and we get an H2:N2 ratio of 3:1 in the synthesis loop.