Globally, the European Union is the second largest steel producer after China, followed by the countries of the North American Free Trade Agreement (NAFTA), Japan and the Commonwealth of Independent States (CIS). These five steel regions produce around 80% of the world's steel. Over the past 50 years, the production capacity of steel, by far one of the most essential materials in terms of volume, has increased from 595 million tons (1970) to 1952 million tons (2021). The steel industry has evolved from a supplier of raw materials to a partner of many steel processors and suppliers of high-value products to individual components. [1] Traditional methods of primary steelmaking depend on using fossil fuels for process reasons, inevitably generating significant amounts of CO2. Globally, the CO2 emissions generated by the steel industry is about 7%, and at the European level, it is 5%. Hence, there is a need to develop alternative green and thus environmentally friendly process technologies to counteract the progressive climate change. [2] Hydrogen plasma smelting reduction (HPSR) is one of the most promising technologies for realizing climate-neutral primary steel production. While most reducing technologies for pig iron production are based on carbon as an energy carrier and reducing agent, the HPSR process relies on electrical energy combined with hydrogen to produce CO2-free green molten steel and water vapor as a byproduct. The HPSR process is currently at technology readiness level (TRL) 5, which means it has been validated in an industrially relevant environment. The demonstration-scale plasma reactor is able to process 200 kg of iron ore. Further, scale-up steps require more solid research results concerning kinetic metallurgical reactions, arc performance and plasma characterization. This cumulative thesis covers the research results obtained by the Montanuniversitaet Leoben and other research groups, the influence of continuous charging via the hollow electrode and the use of pre-reduced material. Another topic covers arc stability, its dependence on the cathode tip, and the characterization of the plasma species by optical spectrometry. Based on various experiments, it was shown that continuous feeding positively affects the reduction rate and hydrogen utilization. Furthermore, it was determined that the geometry of the electrode tip has a much more significant influence on the arc stability than the graphite quality. Experiments with pre-reduced iron ores and sidestream materials showed inconsistent behavior in the initial reduction stages. However, microstructural analyses of the obtained samples showed almost identical results. OES measurements yielded information on plasma colors, influences of process parameters on electron density, information on slag formers, and a methodology for evaluating arc stability or position.