25. Hydrogen Network Optimization

Plantwide systems impact every process unit in a petroleum refinery. All units require electrical power, water, steam and instrument air. Units with fired heaters burn fuel oil or fuel gas from a common pool. Many units require hydrogen and most produce offgas streams, which are collected and treated in common facilities. In addition to methane and other light hydrocarbons, offgas may contain H₂ and toxic H₂S. Most modern refineries can benefit from hydrogen recovery and purification. Keeping hydrogen out of fuel gas is beneficial for many reasons. Recovery decreases the required amount of on-purpose hydrogen. Hydrogen burns hotter than other gases, so it raises the temperature of fuel gas combustion, which can limit fired heaters constrained by tube temperature limits. Hydrogen network optimization is more complex that other utility optimization efforts, because in addition to flow and pressure, one must consider the impact of gas composition on the units to which hydrogen gas might be sent. The benefits of hydrogen network optimization with the technology described in this chapter range from US$ 1 million per year for low- or no-cost recovery and purification projects to more than US$ 15 million per year for modest-investment projects, with payback times measured in months.