Bibliography - L. De Lorenzo

1. De Lorenzo, L., Thomas Kreutz, P. Chiesa, and Robert H. Williams, 2008: Carbon-free Hydrogen and Electricity from Coal: Options for Syngas Cooling in Systems Using a Hydrogen Separation Membrane Reactor. Proceedings of ASME Turbo Expo 2005, Reno, NV, June 6-9, 2005, 130(3), doi:10.1115/1.2795763
   [ Abstract ]

   Conversion of coal to carbon-free energy carriers, H₂ and electricity, with CO₂ capture and storage may have the potential to satisfy at a comparatively low cost much of the energy requirements in a carbon-constrained world. In a set of recent studies, we have assessed the thermodynamic and economic performance of numerous coal-to-H₂ plants that employ O₂-blown, entrained-flow gasification and sour water-gas shift (WGS) reactors, examining the effects of system pressure, syngas cooling via quench versus heat exchangers, “conventional” H₂ separation via pressure swing adsorption versus novel membrane-based approaches, and various gas turbine technologies for generating coproduct electricity. This study focuses on the synergy between H₂ separation membrane reactors (HSMRs) and syngas cooling with radiant and convective heat exchangers; such “syngas coolers” invariably boost system efficiency over that obtained with quenchcooled gasification. Conventional H₂ separation requires a relatively high steam-tocarbon ratio (S/C) to achieve a high level of H₂ production, and thus is well matched to relatively inefficient quench cooling. In contrast, HSMRs shift the WGS equilibrium by continuously extracting reaction product H₂, thereby allowing a much lower S/C ratio and consequently a higher degree of heat recovery and (potentially) system efficiency. We first present a parametric analysis illuminating the interaction between the syngas coolers, high temperature WGS reactor, and HSMR. We then compare the performance and cost of six different plant configurations, highlighting (1) the relative merits of the two syngas cooling methods in membrane-based systems, and (2) the comparative performance of conventional versus HSMR-based H₂ separation in plants with syngas coolers.

2. De Lorenzo, L., and Robert H. Socolow, June 2006: Modeling Technology Choice under Alternative CO₂ Policies. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
   [ Abstract ]

   Our work addresses the interaction between CO₂ policy and coal technology over the next 25 years. Coal power is a particularly attractive sector from which to seek CO₂ emission reductions because the emissions are from large point sources and several strategies are available to lower emissions. The electric industry currently contributes approximately 40% of global CO₂ emissions, and the coal electric industry about 30% of global CO₂ emissions. We develop a linear programming formalism that allows a high-level analysis of three kinds of competition: 1) between several kinds of new coal plants with and without CO₂ capture, each becoming more efficient and cheaper over time; 2) between retiring old coal plants, retrofitting them and constructing new ones; and 3) between building CO₂ capture capability into a new coal plant in two stages (the first stage being a “capture-ready” plant) and building the capability all at once. These competitions are examined under three matched pairs of trajectories of the CO₂ tax that result in three tax levels in 2030 ($100/tC, $200/tC and $300/tC): “sudden-change,” where the tax is increased suddenly at around 2020, and “gradual-change,” where the tax is increased gradually from 2005 to 2030 (fig.1). We find that: i) a “sudden-change” carbon tax induces more retrofitting of vintage plants than a policy with “gradual-change”; ii) all retrofit options considered appear at least once in the scenarios explored; iii) the case for capture-ready plants is weak with current cost numbers available from literature.

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