(712b) Techno-Economic Assessment of the Polygeneration of Liquid Fuels and Electricity By Solar Hybridised Gasification of Coal

Solar gasification offers the potential to convert a greater portion of the fuel input to syngas than is possible with a conventional gasifier, resulting in a higher production of Fischer-Tropsch liquids (FTL), by displacing the carbonaceous fuel that is otherwise burnt in O₂ to provide process heat. In this hybrid gasification process, concentrated solar thermal energy is used when it is available, while autothermal gasification is used when the incoming solar insolation is insufficient. Thus, the intermittency of the solar resource is accommodated through the use of intermediate storage of syngas and turning down the liquid fuel production rate. This paper presents a techno-economic evaluation of a coal-to-liquids process integrated with a solar hybridised, oxygen blown, atmospheric pressure vortex-flow gasifier (SCTL) located at Daggett, USA. The influence of the solar multiple (SM) and syngas storage capacity (hours) on the plant feasibility was assessed. Here, the SM is the ratio of the heliostat field area to the required heliostat field area that can generate a net annual peak solar thermal energy matching the energy required by the gasification process.

The annual specific FTL output and the specific total energetic output (FTL and electricity) of the SCTL plant relative to the conventional coal-to-liquid (CTL) were found to increase by 12% and 15%, respectively, as the SM was increased to 3. On the other hand, the annual reduction in mine-to-tank (MTT) CO₂ emission from the SCTL relative to the CTL was reduced by 17%. The utilization factor of the FT and power generation plants in the SCTL was significantly influenced by the syngas storage capacity. The utilization factor for the SCTL with no syngas storage was calculated to be 74% compared with 93% for the SCTL with 4 hours syngas storage capacity.

To produce 1500 barrels per day of FTL, the levelised cost of fuel (LCOF) for the CTL was estimated to be USD1.2/L₂₀₁₂. The LCOF for the SCTL with no syngas storage was increased from USD1.3/L₂₀₁₂ to USD1.4/L₂₀₁₂, and from USD1.4/L₂₀₁₂ to USD1.5/L₂₀₁₂ with 4 hours syngas storage capacity, as the SM was increased from 0.5 to 3. Despite the fact that the outputs from the SCTL were higher than that of the CTL, this could not overcome the high cost of the solar components and the syngas storage system. Furthermore, the LCOF for the SCTL is sensitive to several parameters identified in the sensitivity analysis, such as the total plant cost, the assumed cost for carbon capture and sequestration, and the operation and maintenance costs.