Techno economic analysis of a micro Gas-to-Liquid unit for associated natural gas conversion

Flared and vented natural gas in remote regions of the world contribute ¿1% of the total CO2 emissions. High investment costs to build facilities to treat this gas and labor costs to operate the infrastructure are deterrents to addressing this environmental burden. Here we report a techno-economic analysis of a commercial mobile manufacturing plant that processes 2400 m3 d-1 of methane via a tandem short contact time catalytic partial oxidation (CPOX) and a single-pass Fischer–Tropsch fluidized bed to produce 7 bbl d-1. Starting from methane and air, a thermodynamic analysis identified the optimized operating conditions considering both carbon yield, CO/H2 ratio and adiabatic conditions. We studied the flammability limits of the mixture at operating pressures and temperatures. The economic analysis itemizes costs for all equipment rather than applying scale-up power law or factors. The greatest contributors to direct costs are the compressors and the CPOX reactor. Operating CPOX at 2.0 MPa reduces reactor volumes but to achieve 90% conversion and selectivity requires operating this unit above 900 °C. Avoiding syngas compression and upstream syngas conditioning reduces capital costs. The capital cost (CAPEX) reaches 570 000 USD when the whole process operates at 2.0 MPa. Considering numbering-up, the price of the 100th unit approaches 360 000 USD thus the MRU increases profitability. We demonstrate how thermodynamics constrains methane conversion and syngas selectivity. A large part of achieving low CAPEX is operating a single pass process, building multiple units, and replacing the methane to heat the treater at the oil tank battery with the incondensable gas leaving the three phases separator downstream the Fischer–Tropsch reactor.