Fuel and hydrogen related problems for conventional steam reforming of natural gas

Steam reforming (SR) process in largescale plants produces more than 500,000 kg H2/day. This mature technology is currently the cheapest method for hydrogen generation with a production cost of about 2 h/kg H2 (https://www.shell.com, 2019). At present the manufactured hydrogen is primarily used in the chemical industry (c.63%), mainly for the synthesis of ammonia and methanol, followed by hydrotreating in refineries (c.31%) [46]. Hydrogen is also used for a number of hydrogenation reactions, involving unsaturated hydrocarbons (including hardening of edible oil) and aromatics, aldehydes and ketones (for instance, oxo-products), and nitrogen compounds (for instance, for aniline manufacture). Other present uses (c.6%) of hydrogen are related to the food, semiconductor, and metallurgical industries.Large-scale (central) facilities can be employed in a decentralized production (2030 scenario) in which the hydrogen can be delivered in pipelines to the end users. However, pure hydrogen networks are only possible if infrastructures and appliances are upgraded accordingly.Small-scale and medium-scale reforming plants are more suitable for distributed application, in which high-grade H2 (99.9%99.999%) is used as fuel for FC-based vehicles or combined heat and power systems. Small-scale plants would produce from ,100 to about 1500 kg H2/day. However, several aspects need to be improved for commercial purposes, such as the filling station footprint, reactor compactness and efficiency, fuel treatment and purification, as well as hydrogen separation and purification steps. Another important aspect from a technical, economic, and environmental point of view is the carbon footprint of the reforming technologies, especially in large-scale production. The natural gas utilization causes the coproduction of large amount of carbon dioxide, the main gas responsible for the so-called greenhouse effect. Carbon capture and storage (CCS) refers to the capture of CO2 from emissions followed by storage, thereby preventing it from entering the atmosphere. There is an increasing interest in SMR plants with CCS technology to produce low-carbon hydrogen. In this chapter, all the abovementioned aspects are elucidated by referring to the technologies conventionally available.