7.3. Technologies for Hydrogen Production

Technologies for hydrogen (H₂) production fall into three main categories:

1. Thermal Processes: Some thermal processes use the energy in various feedstocks (natural gas, coal, biomass, etc.) to release the H₂ that is part of their molecular structure. Other thermal processes known as thermo-chemical processes use heat in combination with a closed chemical cycle to produce H₂ from feedstocks such as water. 
   
   In addition to gasification, the main thermal process technology which is available for production of H₂ is steam reformation of natural gas. It is a well established technology that produces about 95% of the H₂ produced in the United States. Steam reforming involves the reaction of natural gas and steam over a nickel based catalyst. This breaks the methane component of the natural gas into carbon monoxide (CO) and H₂ gas, similar to synthesis gas (syngas) produced via gasification. Then water-gas shift (WGS) is performed to increase the amount of H₂ in the product gas as much as possible.
2. Electrolytic Processes: These processes use electricity to split water into its two chemical constituents, oxygen (O₂) and H₂, using an electrolyzer. The cost and efficiency of producing H₂via electrolytic processes is directly dependent on the cost and efficiency of the electricity used in the process.
3. Photolytic Processes: These processes use light energy to also split water into H₂ and O₂. These processes are currently in the early stages of development and currently are not viable for large scale production.

Efficiency/Cost Comparison to Competing Technologies 
Table 1 presents the cost and performance characteristics of various H₂ production pathways, as of 2004. Many of the technologies that are in the research and development (R&D) stage will require years of improvements before becoming a commercial reality.

The cost of H₂ production depends heavily on the cost of fuel or electricity from which it is produced. As the market price for these inputs to the H₂ production system fluctuate, one given technology may become more attractive economically compared to others.

Coal-to-Hydrogen Process Description 
The U.S. Department of Energy (DOE) has sponsored many design studies on the production of H₂ from coal, with or without the co-production of power.

Recent DOE studies presented the following four process design schemes as possible options for centralized-large-scale H₂ production from coal, and discussed their performance and efficiency:²

• Co-producing H₂ and power in today's coal-based integrated gasification combined cycle (IGCC) plants
• Co-producing H₂ and power in coal-based IGCC with carbon capture
• H₂ production from coal without power export
• Co-producing H₂ and power in future IGCC based on advanced warm gas clean-up and advanced membrane (combined shift and H₂ separation) technologies

Hydrogen

• Why Hydrogen
• Hydrogen & Synthetic Natural Gas from Coal
• Technologies for Hydrogen Production
  • Co-producing H₂ with Current IGCC Technology
  • Co-producing H₂ in IGCC with Carbon Sequestration
  • Hydrogen Production from Coal without Power Export
  • IGCC/H₂ Co-production with WGCU and Advanced WGS Membrane
• Technology for SNG Production
• SNG from Coal: Process & Commercialization
• DOE Supported R&D for Production of Hydrogen