Coproduction of transportation fuels in advanced IGCCs via coal and biomass mixtures

Abstract

Converting abundant fossil resources of coal to alternative transportation fuels is a promising option for countries heavily dependent on petroleum imports if plants are equipped with carbon capture for sequestration and cofed with biomass (30% by weight of the total feed on a dry basis), an essentially carbon neutral fuel, without penalizing the process economics excessively. A potential exists to improve both thermal efficiency and economics of such plants by taking advantage of the synergies of coproducing electricity using advanced technologies under development. Three types of transportation fuels are considered. Fischer–Tropsch (F–T) liquids consisting predominantly of waxes could be processed in existing refineries while displacing petroleum and the refined products introduced into the market place at the present time or in the near term without requiring changes to the existing infrastructure. Ethanol could potentially serve in the not so distant future (or phased in by blending with conventional liquid fuels). Hydrogen which could play a dominant role in the more distant future being especially suitable to the fuel cell hybrid vehicle (FCHV). Two types of coal along with biomass cofeed are evaluated; bituminous coal at $42.0/dry tonne, lignite at $12.0/dry tonne, and switchgrass at $99.0/dry tonne. The calculated cost for F–T liquids ranged from $77.8/bbl to $86.6/bbl (or $0.0177 to 0.0197/MJ LHV) depending on the feedstock, which is comparable to the projected longer term market price of crude oil at ∼$80/bbl when supply and demand reach a new equilibrium [Lafakis. Moody’s Analytics. <http://money.cnn.com/2015/01/09/investing/oil-price-bottom/index.html> (accessed on 12.01.15)] [32] (or ∼$0.0172/MJ LHV). It should be noted, however, that F–T liquids contain no sulfur or nitrogen compounds and no inorganics. The calculated cost of fuel grade ethanol ranged from $4.84 to 4.91/gal (or $0.0566 to 0.0582/MJ LHV), while the price of gasoline in the U.S. amounted to $0.0240 to 0.0279/MJ LHV when crude oil was at ∼$80/bbl. Ethanol coproduction may not appear to be as attractive as the other options at these scales, primarily due to the much lower plant efficiency. However, from a life cycle greenhouse gas emissions standpoint, ethanol produced with biomass cofeeding and CCS, have a lower carbon footprint than gasoline or diesel, especially when derived from petroleum. The calculated cost of hydrogen ranged from $1.87 to 2.13/kg (or $0.0156 to 0.0177/MJ LHV), which is significantly lower than the DoE announced goal of $3.00/kg in 2005.