|Process diagram for the CTL plant. Click to enlarge.|
The US DOE Office of Fossil Energy’s National Energy Technology Laboratory (NETL) has issued a report that examines the feasibility of a commercial 50,000 barrel per day coal-to-liquids (CTL) facility in the Illinois coal basin.
The report, Baseline Technical and Economic Assessment of a Commercial Scale Fischer-Tropsch Liquids Facility, represents the first of a series of plant design studies for commercial-scale Fischer-Tropsch (F-T) plants.
The plant design incorporates coal gasification technology and an F-T reactor system using an iron-based catalyst. The concept includes a cluster of four gasification plants, each containing two gasifier trains for a total of eight gasifier trains.
Each gasification train cluster utilizes two oxygen-blown high pressure ConocoPhillips E-Gas two-stage gasifiers to produce a medium heating value syngas. Oxygen fed to the gasifiers is generated by two cryogenic air separation units (ASUs).
Syngas from the gasification plants is joined in a central manifold and ducted to a central CTL plant. The CTL plant contains F-T reactors, hydrotreating units and hydrocracking units capable of consuming 24,533 tons per day of high-sulfur bituminous coal to produce 27,819 bbl/day of commercial-grade diesel liquid and 22,173 bbl/day of naphtha liquids, which could be shipped to a refinery for further upgrading into commercial-grade end products or for use as a feedstock for the chemicals industry.
The plant design also includes equipment to capture 32,481 tons per day of carbon dioxide, which is compressed to 2,200 psia for injection into a pipeline. Subsequent off-site use and/or sequestration of carbon dioxide were not considered in this design.
The CTL plant also generates electric power, both for internal use and for export to the grid. The off-gas from the F-T process is compressed and used as fuel for the gas turbines, which produce a total of 251 MWe. Unburned fuel remaining in the turbine exhaust is combusted in a downstream duct burner.
Hot flue gas from the gas turbine passes through a heat recovery steam generator to produce superheated high-pressure steam. The resulting steam is combined with that produced by cooling the syngas in the gasification train and with that generated by recovering heat from the F-T reactors and expanded in a multi-stage steam turbine to generate an additional 401 MWe.
Auxiliary plant loads consume the majority of the generated power, leaving a net 124 MWe available for export to the grid.
The total projected plant cost is $3.65 billion. Total capital costs including working capital, start up costs, and owners costs are $4.07 billion. Adding allowances for financing costs results in a total project cost of $4.53 billion.
The study concluded that commercial-scale CTL plants using Midwestern bituminous coal represent “promising economic opportunities,” depending upon the price of crude oil. Based on the specific plant configuration evaluated, the financial analysis projects a 19.8% return on investment, a net present value of more than $1.5 billion, and a payback period of 5 years if the price of crude is $61/bbl. At crude oil prices greater than $37/bbl, the project would achieve ROIs greater than 10%, and a 15% ROI can be achieved at crude oil prices greater than $47/bbl.