The oxygen and hydrogen production section consists of alternative technologies, including (i) an air separation unit (ASU) that produces a 99.5 wt % O2 stream and purchased hydrogen produced by steam reforming of natural gas, or (ii) an electrolyzer unit that produces pure H2 and O2 from the plant's water effluent and electricity. Electricity can be obtained from the grid or alternative sources such as solar, wind, and nuclear technologies as they become more available in the future.
If hydrogen is purchased, the oxygen input must be obtained from an ASU. Air is compressed from ambient conditions and sent to a separation unit (P501) where a 99.5 wt % O2 stream is recovered and the nitrogen rich stream is vented. A portion of the oxygen stream is fed to the low pressure Claus furnace and the rest is compressed to 32 bar for the remaining process units. Hydrogen is produced via steam reforming of methane (SRM) technology to provide the required amount for the RGS unit and the upgrading units. If hydrogen is produced on-site, an electrolyzer unit will be utilized to produce pure H2 and O2 from the water effluent of the SS unit. Oxygen that is not consumed by the CBGTL process will be sold as a byproduct.
The heat and power recovery system utilizes heat engines and pumps that interact with process streams to produce steam or electricity. The framework used is described in detail here. Once the full heat and power integration step is completed, the obtained investment costs are factored into the economic analysis of the whole process.