Natural gas (NG) based chemical fertilizers such as urea, ammonia help increasing the overall food productions of Bangladesh. In general, NG consumption has increased in different industries over the years thus affecting the availability of it. In addition, the quality of NG has changed over the decades in Bangladesh. To better understand the impact of these changes on the ammonia plant, the performance via ammonia process modelling and simulation is considered here. The process model is developed based on the Ashugonj Fertilizer & Chemical Company Ltd (AFCCL) plant process data of Bangladesh. The preliminary safety study is also carried out for this process using Aspen Plus. The preliminary result shows that due to lower carbon content and lower heating value of the current NG, NG consumption has increased in Primary Reformer (PRF), Secondary Reformer (SRF) and different fuel systems to maintain the 3:1 ratio of hydrogen to ammonia in the ammonia synthesis section.