Tech-economic assessment of a coproduction system integrated with lignite pyrolysis and Fischer–Tropsch synthesis to produce liquid fuels and electricity

• Tar hydrogenation was coupled with Fischer–Tropsch synthesis for oil production.
• Moisture content of lignite, gasifier type and product strategy are the key factors.
• Electricity generation improves the economy but decreases the energy efficiency.

A novel coproduction system of lignite pyrolysis integrated with Fischer–Tropsch synthesis and coal-tar hydrogenation to produce liquid fuels and chemicals is proposed. The moisture content of the lignite, the gasifier adopted and the choice of electricity generation are the critical factors that make a big difference in the assessment of the system. Sensitivity analysis of different moisture contents and gasifier types are investigated and comparisons are done between processes with and without electricity generation. The results showed that the system could benefit a lot from the decrease of moisture content of feedstock, and that although requiring higher financial investment, Shell-gasifier-based process would produce more liquid. Moreover, applying the electricity generation system would enhance the economic performance and make an impact on the energy efficiency. By the energy and economic assessments, nearly 40% of the low heat value and over 15% of the internal rate of return in the best case are obtained at an annual handling scale of 5 million tons of lignite. Meanwhile, over half a million tons of liquid are obtained and the CO2 emission is within the range of 7.5–9.5 t/t-oil.

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