A novel gas-solid suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This series of papers reports on the results of process simulation for the proposed process operated with natural gas. This Part 1 deals with simulation of a commercial scale reformerless ironmaking process with heat recovery and hydrogen recycling steps. Ironmaking was simulated in one-step and two-step process configurations. The results indicated that the proposed process would, depending on the process configuration, reduce carbon dioxide emissions by 39–51% and energy consumption by 32-44% compared with the average blast furnace process (61–66% if the lower heating value of natural gas is used). The sensitivity of the energy requirement to operating conditions was also examined.